HarBal Tutorials

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    Har-Bal Tutorials

    Har-Bal is the software that introduces the concept of Harmonic Balancing and the means ofachieving it. In this section we introduce the software and the process of Harmonic Balancing asimplemented through Har-Bal. For an introduction to the concept, its origins and its benefits overother mastering processes see Harmonic Balancing. Those already familiar with this introductorytutorial and are interested in exploring the fullest potential of Har-Bal should continue on to theAdvanced Tutorial for a brief discussion on a different but sonically pleasing approach to equalisation.

    Har-Bal Layout

    The essential elements of the Har-Bal environment are shown below:

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    1. Status and time displayThis display shows the live time in seconds of the track being previewed and also displaythe current state of Har-Bal (Ready, Playback, Record)

    2. EQ Filter related toolbar buttons

    These toolbar buttons allow you to open, save and create new EQ filters for the trackbeing harmonically balanced.

    3. Reference related toolbar buttonsThese toolbar buttons allow you to open, close a reference track or reference trackanalysis and swap a playable reference with the current track being harmonicallybalanced.

    4. Filter design undo/redo toolbar buttonsThese toolbar buttons allow you to undo and redo EQ filter design changes made usingthe gain cursor.

    5. Playback/Record control related toolbar buttonsThese toolbar buttons allow you to playback and/or record the current track with orwithout the EQ filter inline.

    6. HB Air, Filter and reference control toolbar buttonsThese toolbar buttons allow you to switch HB Air in and out, switch the EQ filter in andout and switch the reference track in and out of playback.

    7. IntuitQ toolbar buttonsThese toolbar buttons allow you to utilised the IntuitQ algorithms to optimise thespectrum content of your track.

    8. Spectrum display control toolbar buttonsThese toolbar buttons let you control the spectrum display and design the EQ filter.

    9. Average power figure of merit indicatorThis indicator displays the un-weighted average power figure of merit for the current

    track. This figure is relative to the power of a full-scale sine wave.

    10. Peak power figure of merit indicatorThis indicator displays the un-weighted aggregate peak power spectrum figure of meritfor the current track.

    11. Volume control sliderThe volume control slider can be used to change the playback monitoring level. This hasno effect on recorded levels.

    12. Limiter Gain control sliderThis limiter gain control slider allows you to apply a gain to the playback and/or recordingof the current and/or reference track. This is typically used for normalising tracks. Thisgain is on the input side of the integrated Har-Bal limiter, which limits the final output to

    0.1dB relative to full scale.

    13. HB Air control sliderThis HB Air control slider allows you to apply the HB Air stereo width effect to therecorded and played back tracks. This is typically used when your track lacks a sense ofspace. Note that it has no effect on mono tracks.

    14. Tips popupThe tips popup gives spectrum context sensitive clues to designing appropriateequalisation filters.

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    15. Spectrum displayThe spectrum display shows a graphical representation of the overall energy content ofthe current and/or reference track. The spectrum display shows the average spectrum,the peak spectrum and the geometric mean of the two. We make use of the spectrumdisplay and the gain cursor to design EQ Filter.

    16. Status bar message areaThis region of the status bar is used to report context sensitive help on menu items andtoolbar buttons as well as general data values from the graphical display.

    17. Cursor focus indicatorThis indicator informs you which spectrum trace is being edited when using theparameteric and shelving cursors.

    18. Limiter gain reduction meterThe limiter gain reduction meter gives a graphical indication of the amount of gainreduction being applied during playback by the limiter. The meter is a log scale meter(linear in dB) with full-scale corresponding to 15dB.

    19. View control buttonsThe view control buttons can be used to change the visibility of various aspects of thespectrum display.

    20. Cue slider controlThis slider control allows you to cue the current and/or reference track to a particularlocation.

    Where to Start?

    Har-Bal does its magic on sound files only, so a good place to start is with collecting the sourcematerial to harmonically balance. For a list of supported file types consult the Open Command topic.

    One notable exception from the list is the mp3 format. Due to the licensing arrangements required forthe mp3 format we currently have no intention of supporting mp3. It is also worthwhile noting that

    mp3 is generally not a good format to use for source material that has yet to be harmonicallybalanced and with good reason. The mp3 format uses lossy compression built around perceptualencoding of the recorded sound. What that means is that if the model believes that you cannot hear aparticular part of the spectrum in a recording (because it is masked by an adjacent sound) then it willdrop it altogether. This is fine if the recording is already harmonically balanced but if you have apoorly balanced recording and harmonically balance it, normally, much of what is masked becomesreadily audible and hence, the improvement in clarity obtained using harmonic balancing. But if youhave encoded the source using mp3 before equalisation the mp3 encoder may drop a significantproportion of content that can never be recovered, with or without harmonic balancing. For thatreason we only recommend using mp3 post harmonic balancing.

    Ideally the source material should be arranged such that each track is in a different file. You could, ifyou wish, perform harmonic balancing on a single file corresponding to and entire album but theoutcomes that you will end up with is likely to be less than optimal. This is due to each track in a

    compilation having its own specific characteristics, which become lost in the other tracks if lumpedtogether.

    Given a set of tracks that you wish to master we are now ready to start. The first thing to do is toopen one of your tracks using the Open Command. The first time you do this on any given trackHar-Bal will proceed to analyse the spectrum content. This may take some time depending upon thelength of the track and the speed of your computer but once done the result is saved to disk forre-use. If you then re-open the same track, provided it has not been modified in any way, Har-Bal willopen it immediately by reading the analysis file of the track and using it to initialise the spectrumdisplay. Alternatively, if you have a compilation of many tracks that you are going to work on you can

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    pre-analyze those tracks in the background while you work on another file in Har-Bal by using the File| Batch Analysis menu command.

    For the sake of this tutorial I shall be demonstrating Harmonic Balancing of a CD compilation usingthe CD Face Value by Phil Collins (Atlantic 16029-2 1981). Note that we do not condone illegalpirating of copyright protected recorded material in any way. We have a legitimate copy of this CDand are re-mastering it for demonstration purposes only.

    Beginning a Session

    Assuming that you are mastering new material or re-mastering old material then the first thing youshould do is thoroughly listen to the compilation of tracks to build a mental picture of the sound theproducers are trying to achieve. Make note, mental or otherwise, of anything that concerns you.

    After doing so pick the track from the compilation that has a broad spectrum (typically tracks with themost instruments and instruments that are played loudly) but also the best sound quality. The reasonfor this choice is that the first track we master will become a reference for the remaining tracks. If youwere to chose a slow song it wont fill the entire spectrum and then you will have some difficultydrawing inferences from your reference if you were to then open a busy track.

    Using the Open Command I will open the track 9 (Thunder and Lightning)as the first track as it has a

    full spectrum and a quite good balance. This is the first time I have opened this track so the analysisprogress dialog pops up as shown below. For the purpose of following this tutorial in the case whereyou do not have access to the actual recorded material, we have included the analysis files for all ofthe tracks of this album. You can find them in the folder c:\program files\har-bal\tutorial (change thepath shown here to coincide with the location that you installed har-bal in).

    When the analysis runs to completion the spectrum display shows the following result.

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    The spectrum display has three traces; the lower trace is the average energy content of the track atdifferent frequencies and the top trace is the peak energy content of the track.

    Track 9: Thunder and Lightning

    Looking at the spectrum we see that it extends from around 50Hz to 10kHz with a subdued midrangeand a prominence at 5kHz. We could set about evening the spectrum out using manual adjustmentbut with the advent of intuitQ there is a better way. We start by selecting the intuitQ cursor and thenapplying it to the frequency range from 59Hz to 9.7kHz as illustrated below.

    Select this tool,

    and do this,

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    Note that the illustration above has been cut down in size to keep the help file size small. As manypeople who download this software are still on dial up connections we want to maintain a small installsize. We suggest that to obtain a clearer picture of the process that you follow and reproduce all ofthe steps in this mastering process by loading the corresponding analysis file in the folder c:\programfiles\har-bal\tutorial. Doing so will allow you to duplicate the steps although you will not be able to play

    the tracks. To do so you need the original source material, which should be easy enough to find. Justkeep in mind that for this discussion to be valid it needs to be the original CD master. As far as I amaware this album has not been re-mastered and re-released so I dont believe this is an issue,however, it is worthwhile checking that the analysis results you get are the same that I did.

    In following this step you will note that intuitQ has significantly smoothed the spectrum by cutting theoutput at the low frequency end, boosting the mid range, cutting the highs around 5kHz and addingsome boost around 10kHz. On listening to the result the bass still appears to be masking the midrange somewhat. Looking at the spectrum we note a still quite strong peak at around 116Hz. Byselecting the gain cursor we apply a cut of about 1.7dB with a Q of 5.3 as illustrated.

    Select this tool,

    and do this,

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    Again listening to the result I find the bass still lacking tightness so we use the low shelving cursor totame it by shelving at 296Hz in the manner illustrated.

    Select this tool,

    and do this,

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    Further listening shows that the bass is now under control but the track now sounds too bright. Totame the brightness we select the high shelving tool and shelve from 1kHz upwards in the mannerillustrated.

    Select this tool,

    and do this,

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    Now the track sounds like music to my ears as far as the tonality is concerned but the overall level ofthe recording is quite low (at 17.66dB average power). To make it more consistent with currentrecordings we can use the gain slider to increase the mastered level. My preference in this process isto increase the gain slider until the limiting meter just lights. By doing so we can obtain a good levelwithout loss of dynamics. Furthermore, if we consider that this compilation contains quite a few ratherdynamic tracks (In the Air Tonightis particularly so) it is wise to take a conservative approach so that

    the more dynamic tracks don

    t end up over limited when matching the loudness. For these reasons Isettled on a gain setting of +4dB.

    Having made the necessary EQ changes and level changes you could also perhaps use the Air sliderto add extra space although in this case I found none of the tracks required it so have avoided usingany Air. Having designed our equalisation we now save the filter file, record the result and open thistrack and the corresponding filter as a reference for the remaining tracks to be processed.

    Track 1: In the Air Tonight

    Now we move on to track 1 (In the Air Tonight). If following the tutorial in Har-Bal you should open thefile 1.anl (or if you have the tracks handy open it instead). As before, our first step is to select theintuitQ cursor and apply it to the dominant range of the track spectrum, which extends from 65Hz to9kHz.

    Select this tool,

    and do this,

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    On listening the result the clarity is significantly improved though there is a hint of low frequencymasking and the upper mid range is over-emphasised around 2kHz. Both these issues arise out ofside effects from using intuitQ with tracks in which spectrum holes exist. In such cases this problemis easily mitigated with excellent results by applying the intuitNull cursor to the frequency ranges inwhich the spectrum holes are found. This has the effect of undoing intuitQ for that specific frequency

    range. So, our next step is to select the intuitNull cursor and apply it from 106 to 129Hz and also from1.07kHz to 3.07kHz.

    Select this tool,

    and do this,

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    and this,

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    The track equalisation is complete but the loudness does not match well with the newly masteredlevel of the reference track, Thunder and Lightning. We could use the normal match loudnessfunction in Har-Bal but if you were to do so you would find that the results are far from good. Thereason for this arises from the fact that the instrumentation of the two tracks is vastly different andthis difference is not taken into account by the normal loudness matching algorithm. However, if we

    apply the match loudness algorithm so that it attempts to match only over the loudest part of the trackspectrum then the results are very good. We can do this easily using the match loudness cursor. Inthis case the spectrum plateau extends from 68Hz to 619Hz and applying match loudness to thatrange results in a gain of 4.2dB. Assuming that the original was well match this turns out to be a goodresult and it is certainly confirmed through listening.

    Select this tool,

    and do this,

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    Track 2: This Must be Love

    Now we have completed the design process for track 1 so we save the f ilter file, record the EQdversion and move on to track 2, This Must Be Love. Open the file 2.anl. Once again our first step is toexamine spectrum to determine the dominant range and then apply intuitQ to it, which from

    inspection appears to be from 55Hz to 8kHz. We apply the intuitQ cursor to this range.Select this tool,

    and do this,

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    As this track is a gentle one with few instruments you will note that intuitQ will have overemphasisedthe upper mid-range between 1kHz and 4kHz. This overemphasis if left untreated will result in aslightly metallic and hard sound rather than a warm sound that far better suits this track. To restorethe warmth we select the intuitNull cursor and apply it to the frequency range from 960Hz to 3.7kHz.

    Similarly there is a natural absence of much sound around 170Hz and 130Hz, which has beenover-emphasised by intuitQ. By also treating those regions we can increase the tightness and clarityof the lower mid range. These edits are illustrated below.

    Select this tool,

    and do this,

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    and this,

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    and this,

    With the track equalisation complete we finish off with loudness matching. We select the matchloudness cursor and apply it to the frequency range from 58Hz to 600Hz, resulting in a gain of 4.3dB,which is once again close to the reference gain increase of 4dB. It would appear that loudness

    matching is largely agreeing with the level matching in the original master.

    Select this tool,

    and do this,

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    Track 3: Behind the Lines

    Now we save the filter design, write the EQd track and move onto track 3, Behind the Lines. Openthe file 3.anl. This track, being more upbeat, shows a much fuller spectrum. Once again we start withintuitQ and apply it to the frequency range from 47Hz to 10kHz.

    Select this tool,

    and do this,

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    Once again, immediately after processing with intuitQ we look at the result to see if intuitQ hasoveremphasised naturally weak parts of the spectrum. To some extent it becomes quite easy toguess which areas those are but I would generally recommend that you validate those decisionsthrough critical listening. This is easy enough to achieve through applying the edit and then usingundo and redo while listening. Doing so should make it readily apparent if you are on the right track.

    Another good strategy is to switch to frequency response view and look at the peaks in the response.If there are a few peaks that are much larger than the rest that should arouse your suspicion. Usingthese techniques I identified two areas of concern. One around 570Hz and the other is the regionfrom 1.9kHz to 3.3kHz. We apply intuitNull to both of these as illustrated.

    Select this tool,

    and do this,

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    and this,

    It is clear from both critical listening and visual inspection that the overall tonal balance of this track is

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    markedly different from our reference. The bass is overly prominent. We attack this issue with thelow shelving cursor by applying it to frequencies below 630Hz in the manner shown.

    Select this tool,

    and do this,

    Now as a consequence the track sounds too bright (the brightness was necessary previously tocombat the masking provided by the prominent bass). We attack this issue with the high shelvingcursor by applying it to the frequencies above 870Hz in the manner shown.

    Select this tool,

    and do this,

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    At this point we partake in further critical listening. On playing back the track and toggling the EQ inand out it is clear the track has much better definition and punch than the original mastering.However, the original has a warmer mid range. In particular, my ears note a rather overbearingstridency in the lead vocal. To combat this I chose to apply a small amount of parameteric EQ to themid-range around 1kHz. This edit is illustrated below.

    Select this tool,

    and do this,

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    Further listening post edit confirms the edit as a good one and the equalisation job is complete forthis track. Once again we now match the levels by selecting the match loudness cursor and apply itto the frequency range from 58Hz to 13.6kHz. This results in a gain of 3.2dB. After doing loudnessmatching it is worthwhile playing the track and toggling the reference button to verify the compatibilityof the track level with the reference and making fine scale adjustments if need be. Listeningconfirmed the compatibility and I made no further adjustments.

    Select this tool,

    and do this,

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    Track 4: The Roof is Leaking

    Now we save the filter design, write the EQd track and move onto track 4, The Roof is Leaking.Open the file 4.anl. This track is an acoustic one with a subdued bottom end and a nasal soundingvocal. Yet again we begin with intuitQ. In this case we apply it to the range from 78Hz to 7.5kHz.

    Select this tool,

    and do this,

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    Again, after applying intuitQ we look for areas of over emphasis and confirm them through criticallistening. I identified and applied intuitNull to the frequency ranges 1.3kHz to 3.3kHz, 450Hz to 540Hzand 108Hz to 145Hz as shown.

    Select this tool,

    and do this,

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    and this,

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    and this,

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    On listening I find the result somewhat pleasing although the absence of lower harmonics in both thevocal and the electric piano does not sit well with the other tracks. To maintain a better tonalconsistency we go about restoring some bass with the low shelving cursor. We apply a boost tofrequencies below 470Hz and a subsequent cut for frequencies below 80Hz to maintain clarity andavoid excessive subsonic amplification.

    Select this tool,

    and do this,

    and this,

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    Listening to the equalisation changes made demonstrates a much fuller sound with a complete lackof mid range stridency which was evident in the original mix. Be that as it may, the track, in myhonest opinion, still holds true to what the producers were trying to achieve. It is essentially the samerecording but with a little added clarity.

    Once again, it is time to match the loudness to the reference. In this case we apply the matchloudness cursor to the frequency range from 560Hz to 1.3kHz. This results in a gain of 5.9dB. Thisfigure is seemingly large in comparison to the original master but listening tests confirm it to be a

    good choice. I would argue that the nominally extra 2dB over the original master is compensation forthe spectrum modification to the bottom end.

    Track 5: Droned

    Now we save the filter design, write the EQd track and move onto track 5, Droned. Open the file5.anl. Starting with intuitQ we apply it to the frequency range from 76Hz to 7.8kHz.

    Select this tool,

    and do this,

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    Again, we look for overemphasised regions. We identify and apply intuitNull to the followingfrequency ranges: 1.6kHz to 2.6kHz; 70Hz to 138Hz and 460Hz to 579Hz.

    Select this tool,

    and do this,

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    and this,

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    and this,

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    Then we perform loudness matching by applying the match loudness cursor to the frequency rangefrom 133Hz to 1.81kHz. This results in a gain of 3.4dB. Critical listening tests demonstrate theappropriateness of both the equalisation and the level matching.

    Effective Har-Bal Usage : The Remaining Tracks

    Now we save the filter design, write the EQd track and move onto track 6, Hand in Hand. This isbecoming rather tedious isnt it? You are getting the picture now arent you? The process is simplebut effective:

    Step 1 : Apply the intuitQ cursor to the dominant spectrum range

    Step 2 : Identify any overemphasised parts of the spectrum and counter them with intuitNullcursor.

    Step 3 : Make any further tonal changes to the track as required using the shelving andparametric cursors.

    Step 4 : Use the match loudness cursor to match the track volume with your reference.

    And above all, listen to your changes as you make them to confirm that you are doing the right thingand if you dont have a listening environment you can trust then use headphones. Its not ideal but itis better than being led up the garden path by poor room acoustics. No amount of electronic trickerywill fix poor acoustics, only appropriate acoustic treatment. Finding out what is appropriate ischallenging and time consuming, certainly worthwhile, though I suspect many will be put off by thechallenges posed and most cant afford to hire a good acoustic consultant.

    The complete edit list for the album is shown below and the filter files that I created can be found inthe same folder as the sample analysis files (c:\program files\har-bal\tutorial). On all accounts the

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    end result far exceeded my expectations and I believe the re-mastering is comparable to anythingavailable from professional mastering houses. The interesting point here is that I remastered theentire album in no more that 2 hours through my old Sennheiser HD450 headphones with dodgy earpads (home made as the originals disintegrated and as a consequence they dont sound exactly theway they should) and the effects of a cold. You certainly can achieve equal results with conventionalapproaches but I very much doubt that you can in the same time frame. Imagine the response if yousaid to a high-end professional mastering engineer that you want this re-mastered in 2 hours? Do youthink that he/she could deliver something as good? They probably wouldnt even consider taking onthe job.

    Track 6 : Hand in Hand

    IntuitQ applied from 40.5Hz to 11.5kHz

    IntuitNull applied from 483Hz to 599Hz

    IntuitNull applied from 2kHz to 3.3kHz

    Low Shelving cut applied to frequencies below 588Hz (~ -2dB @ 100Hz)

    Parametric cut applied to 1.2kHz, Q = 0.95, gain = -0.7dB

    High Shelving cut applied to frequencies above 1.1kHz (~ -2dB @ 10kHz)

    High Shelving boost applied to frequencies above 6.9kHz (~ +0.5dB @ 10kHz)

    Match Loudness applied from 58Hz to 11kHz

    Track 7 : I Missed Again

    IntuitQ applied from 47Hz to 10kHz

    IntuitNull applied from 2.1kHz to 3.3kHz

    Low Shelving cut applied to frequencies below 215Hz (~ -2dB @ 50Hz)

    High Shelving boost applied to frequencies above 4.7kHz (~ +1dB @ 10kHz)

    Match Loudness applied from 57Hz to 11kHz

    Track 8 : You Know What I Mean

    IntuitQ applied from 58Hz to 9.4kHz

    IntuitNull applied from 1.4kHz to 3.3kHz

    IntuitNull applied from 121Hz to 165Hz

    IntuitNull applied from 56Hz to 80Hz

    Low Shelving boost applied to frequencies below 348Hz (~ +3dB @ 50Hz)

    Low Shelving cut applied to frequencies below 48Hz (~ -10dB @ 20Hz)Match Loudness applied from 174Hz to 1.24kHz

    Track 10 : Im Not Moving

    IntuitQ applied from 54Hz to 9kHz

    IntuitNull applied from 1.5kHz to 3.2kHz

    IntuitNull applied from 508Hz to 672Hz

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    IntuitNull applied from 56Hz to 80Hz

    Low Shelving cut applied to frequencies below 483Hz (~ -5dB @ 40Hz)

    High Shelving cut applied to frequencies above 1.46kHz (~ -1dB @ 10kHz)

    Match Loudness applied from 61Hz to 1.16kHz

    Track 11 : If Leaving Me Is Easy

    IntuitQ applied from 56Hz to 9kHz

    IntuitNull applied from 1.1kHz to 3.8kHz

    IntuitNull applied from 121Hz to 145Hz

    IntuitNull applied from 226Hz to 290Hz

    Parametric cut applied to 103Hz, Q = 15, gain = -4.1dB

    Parametric boost applied to 71Hz, Q = 3, gain = 2.8dB

    Match Loudness applied from 65Hz to 970kHz

    Track 12 : Tomorrow Never Knows

    IntuitQ applied from 48Hz to 8kHz

    IntuitNull applied from 2.4kHz to 3.3kHz

    IntuitNull applied from 1.1kHz to 1.9kHz

    IntuitNull applied from 140Hz to 165Hz

    IntuitNull applied from 71Hz to 93Hz

    Parametric cut applied to 64.6Hz, Q = 15, gain = -2.5dB

    Parametric cut applied to 130Hz, Q = 15, gain = -2.7dB

    High Shelving cut applied to frequencies above 836Hz (~ -1dB @ 10kHz)

    High Shelving boost applied to frequencies above 6.75kHz (~ +0.2dB @ 10kHz)

    Match Loudness applied from 49Hz to 4.41kHz

    Why Does intuitQ Work as Well as it Does?

    If you mentioned something like this to a professional mastering engineer theyd most likely tell you itcant work, it will compromise your recordings and youll never obtain as good results as they couldthrough listening and considered EQ adjustment through their high end gear. If they were talkingabout spectrum matching there argument is absolutely correct but where in the preceeding exampledid we use spectrum matching? We didnt! I dont recommend it, even though Har-Bal has the

    intuitMatch function capable doing just that. Simply put, matching only works well in very specificcases. It is not something you should do as a matter of course. The arguments you hear frommastering engineers in this respect are absolutely correct.

    Let say it again. I dont recommend spectrum matching and nowhere in my recommended use of theproduct in the preceeding re-mastering, or anywhere else for that matter, did I do so. If you wish torefer to IntuitQ as spectrum matching then you would say that it is a self-referential process but intruth it isnt even that. IntuitQ is a smoothing algorithm that smooths the spectrum in the frequencyrange you choose with a penalty constraint on curvature. Put plainly, that means that it attempts tocome up with a spectrum shape that overlays the original spectrum but has fewest sharp bends.

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    What is the significance of that? Masking! If you have a sharp transition in the spectrum then it isindicative of an instrument occupying one part of the spectrum possibly masking another. Afterapplying intuitQ you typically hear more detail than before though in some cases that extra detail isnot desired. In those circumstances we can restore that masking with intuitNull. The key point here isthat these tools empower you with the ability to quickly and easily optimise the track EQ.

    It is an interesting exercise applying intuitQ to a well mastered track. Often the resulting changes

    intuitQ makes is small and inaudible indicating the validity of the algorithm. In cases where intuitQdegrades the response it is generally always due to the over-emphasis of quiet content that isnormally masked, either partially or fully. Simple application of intuitNull corrects the error resulting ina very good equalisation. Again, the key issue is that these tools give resulting equalisations that areconsistent with the decisions made by professional mastering engineers. IntuitQ and the other toolsprovided by Har-Bal form a natural, efficient and effective means of performing equalisation. It wouldseem that much of the objection stems from the fact that we dont offer single button masteringperfection though we never made such claims. Perhaps a case of damned if you do or damned if youdont.

    One thing that intuitQ offers that mere listen can never do is objective separation from the acousticpeculiarities of a specific listening setup. All studios, no matter how good, will have some degree ofbiasing, be it from imperfect acoustics or imperfect components or even imperfect engineering(people in all professions have bad days). Subtle variations in frequency response will introduce bias

    into the perception of the recording by the mixing or mastering engineer. That bias translates intoincorrect equalisation and / or mixing decisions. In fact, if you happen to overlay the realisedfrequency responses to the equalisation filters for re-mastered tracks from one album recorded inone studio a pattern generally emerges. Here are three examples of exactly that. The first is aselection of tracks from Face Valueby Phil Collins, next, the tracks from Abacabby Genesisandfinally tracks from Elsewhere for 8 minutesby Something for Kate.

    Filter responses for tracks from Face Valueby Phil Collins

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    Filter responses for tracks from Abacabby Genesis

    Filter responses for tracks from Elsewhere for 8 minutesby Something for Kate

    All tracks demonstrate a curious coincidence of problem areas, particularly for the later two cases.These are not exceptional cases. In fact, most albums that I have re-mastered (for my own personallistening pleasure not commercial re-mastering) using intuitQ shows similar consistency betweentracks. Is this mere coincidence or an indication of the acoustic characteristics of the environmentwhere the tracks were mixed and / or mastered. It certainly would be interesting to perform acoustictests on the studios involved, though the logistics of making that a reality (for someone in my

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    position) is unlikely, at least for now.

    A sceptic may argue that these results simply show biases in my own listening environment and notthat of the studio. The counter to that argument is that if this were the case you would expect thecommon features to be common to all tracks I re-master. This is clearly not the case as theSomething for Katealbum colourations are quite distinct in comparison with the Genesisand PhilCollinscases. An interesting point about the first two examples is that they were recorded and mixed

    by Hugh Padgham so there is a possibility of common factors resulting in similar mixing biases (andthis is no criticism of Hugh Padgham whose recording work I admire).

    This concludes our introductory tutorial on using Har-Bal. Be prepared to experiment. In time and withexperience you will discover the best way to use it. Those interested in exploring the fullest potentialof Har-Bal should continue on to the Advanced Tutorial for a brief discussion on how to get the bestout of your tracks. Should you have any ideas or comments concerning Har-Bal we would certainlybe interested in hearing them. You can email us on [email protected].

    Advanced Tutorial An Introduction to Empathetic Equalisation

    Although intuitQ is a powerful tool that can provide exceptional outcomes to many recordings therestill remain quite a few tracks that defy improvement using this approach. The approach you are

    about to be introduced to is one we have developed through trial and error over the past year as ameans to combat difficult recordings. To our surprise we have discovered that this approach issuperior to intuitQ on all counts even though both approaches end up with similar equalisationcurves. Where this approach is superior to intuitQ is its ability to preserve the dynamics of arecording. For poorly mixed recordings correction through intuitQ can lead to a stifled or muffledsound as extreme cutting of stridency strangles the sound of adjacent instruments. This newapproach can tame those nasty peaks whilst mitigating much of the negative impact of savageequalisation cuts. However, unlike intuitQ, this approach is entirely manual and somewhat timeconsuming to perform. In the future we are confident of being able to codify the approach into animproved intuitQ but for the time being here is the process of Empathetic Equalisation which Har-Balhelps to make possible.

    A Tale of difficult recordings

    This new process has its origins in my attempts to improve upon some commercially releasedrecordings in my collection, both of which failed dismally under intuitQ. The first case was that of thefirst self titled Dire Straitsalbum, which has no mastering credit. The second is the Robert Crayalbum I was Warned, which was mastered by Bernie Grundman. In the former case I found the DireStraitsalbum quite reasonable though a tad muddy, and a couple of the tracks are particularly harshand strident in the mid-range. In the latter case the Robert Crayalbum sounds reasonable on a firstlisten but as time progresses and on nearing the end of the album the ears are starting to strugglewith the overbearing upper mid-range. The first track, Just a Loser, Is particularly troubling.

    IntuitQ applied to the Dire Straitsalbum, whilst largely cleaning up the muddiness largely destroyedthe accuracy and quality of the top end. In many attempts at manual editing using the traditionalapproach I could get the tonal balance right but not without losing the top end quality or incurringsome degree of loss of definition. Similarly, with the Robert Craytrack, Just a Loser, I could get a

    better balance but not without making his vocal sound muffled and indistinct. Both experiences leftme wondering what could possibly be done to improve upon these recordings without the negativeside effects.

    The Robert Crayalbum sounded rather dry so I did some experiments with the application ofidealised reverberation with a specific colour designed to compliment the lack of energy in the lowermid-range. This approach did seem to make some inroads into improving the quality of his vocal partin particular. On inspecting the resulting spectrum and comparing with the original it was clear thatthe overall change in lower mid range content was rather minimal but the lumpiness had increased!That wasnt entirely surprising though the significance of it in the current approach didnt really dawn

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    upon me until months later when attempting to improve upon another entirely different album. Yetagain, intuitQ was of no help but this time I recalled that earlier result and then wondered what theoutcome might be If I were to attempt to control problem areas in a recording by exaggerating or atleast preserving of the peak and trough excursion in the spectrum rather than dumbing it down. Tomy pleasant surprise it appeared to work though not as well as Id hoped. The problem was thatHar-Bal 2.2 has 1/6th octave spectrum smoothing applied so the degree to which I could read thepeaks and dips was limited by that factor. Furthermore the selectivity of the designed filter wassimilarly limited. When the resolution was increased to 1/12th octave the quality of the equalisationoutcomes became increasingly unquestionable. Whereas before, remediation was producing abalance but dull recording, the new approach was producing a balanced average spectrum trendwithout compromising the track dynamics. Thus was born Empathetic Equalisation, the name ofwhich stems from the idea behind the technique of preserving the narrow peaks whilst taming thebroad average : the equalisation has empathy toward the music.

    So what is Empathetic Equalisation?

    Empathetic Equalisation can be loosely defined as the process of high Q notching and peakingapplied to the tracks peak spectrum in such a way as to produce a uniform envelope of spectrumpeaks with a relatively uniform depth of troughs. The filter is also constructed conditional upon

    producing a uniform peak and average spectrum trace when viewed at 1/3rd octave resolution. Fromthe outset it should be noted that the Empathetic Equalisation technique is only applicable torecordings containing two or more instruments (as a general rule you can consider theapplicability of the approach as a sliding scale from zero applicability for solo tracks to full applicabilitywith an orchestra). Religious application of the Empathetic Equalisation approach to solo tracks willundoubtedly damage the track fidelity. Working with solo tracks requires a more considered andmodest approach which we shall not be discussing here.

    To illustrate this process let us consider the track Setting Me Up, taken from the self-titled Dire Straitsalbum, the 1/12th octave spectrum of which is shown below. To view it at this resolution click on the1/12th resolution button,

    which can be found on the lower right hand corner of the Har-Bal window. It is readily apparent that

    the track is particularly strident in the 2kHz region and less so around 500Hz whilst also showingsome weakness around 300Hz and between 600Hz and 1.2kHz. These problem areas are mostapparent in the peak spectrum trace though the average trace shows similar colouration. Theseproblem areas are readily audible though ridding the track of them using conventional approaches(including intuitQ) leads to unpleasing results.

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    The essence of Empathetic Equalisation is to produce a smooth envelope of peaks in the peak tracewithout reducing the adjacent peak to trough depth. A more conventional approach would be to applya narrow band cut to high peaks but doing so will reduce the peaks far more than the troughs andthis has significant masking consequences, which we shall demonstrate later. For the moment let us

    just assume that the way to tackle this issue is by the following technique.

    Rule 1: If you have a high peak that needs cutting then cut the adjacent troughs to the peak orcut at the mid-points between the peak and the adjacent troughs using high-Q parametrictool edits.

    Rule 2: If you have a low peak that needs boosting then boost the peak directly with high-Qparametric tool edits.

    Rule 3: If you have a broad and solid peak with weak troughs then break up the broad peak buyusing high Q cutting of the weak troughs, making the trough depths much bigger.

    Rule 4: In general you should shape the spectrum (peak and average) so that the resultantspectrum flows through the original (particularly when viewed in 1/3 octave spectrum). Inother words there is as much of the old spectrum above the new as is below. The reason

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    for aiming for this type of shape is that it ensures you are respecting the mix and notattempting to drastically alter it. Note that the assumption here is that the mix was carriedout in a tonally neutral environment with neutral speakers and ears. This is not always thecase so the case may arise where you do end up altering the mix composition tocompensate for poor mixing conditions. The strong 2kHz output in the example is a casein point and possibly caused by deficiencies in the monitors used at the time.

    Please note that these rules are to be interpreted in a loose fashion. They are not absolutes in anymathematical sense but rather a guide on how to approach the problem. Every track invariablyrequires unique processing, which will often not strictly follow these rules and these uniqueadjustments are arrived at through trial and error.

    Returning to the spectrum with these rules in mind it can be seen that the peak spectrum needsboosting and cutting in the locations illustrated below.

    Dire Straits Setting Me Up: A problematic track spectrum

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    In more greater detail, let us start by bringing down the main problem area : the 2kHz region. Webegin by choosing an adjacent trough and cutting with a high-Q cut to bring down the peak amplitude(note that when using the gain tool the Q can be forced to its maximum setting by pressing andholding down the M key when dragging the mouse). This is an application of Rule 1 above.

    Step 1 cutting adjacent troughs to bring down a high peak

    Next we tackle the double peak around 2.5kHz. Here we exaggerate the depth of the trough inaccordance with Rule 3.

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    Step 2 exaggerating trough depths to reduce a broad peak

    Now we continue to cut dominant peaks in accordance with Rule 1.

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    Step 3 cutting adjacent troughs to reduce peaks

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    Step 4 cutting adjacent troughs to reduce peaks continued.

    After these edits we find our envelope of peaks is beginning to take shape though some peaks aretoo weak. Those weak peaks we exaggerate in accordance with Rule 2.

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    Step 5 boosting weak peaks

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    Step 6 boosting weak peaks continued.

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    Step 7 boosting weak peaks continued.

    The upper parts of the spectrum are now taking shape but we still need to tackle the issues in thelower part. Tackling the lower half we apply the same techniques as for the upper half. Rather thandemonstrate this in repetitive detail we simply highlight the peaks and troughs that require adjustmentand the direction of the adjustment.

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    Step 8 Illustration of the peaks and troughs to modify

    Now the spectrum is beginning to show much better uniformity. At this point we could either leave itas it is and obtain a clean but less controlled sound or take it a little bit further to obtain a morepolished but less idiosyncratic sound by adjusting the peaks such that they fit a uniform envelope. Todo so we would adjust the regions as indicated below,

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    Step 9 - Illustration of the peaks and troughs to modify for a more polished sound

    resulting in the following spectrum. The rationale for this approach is that the peak intensity in thepeak spectrum loosely corresponds to the intensity of notes played by the instruments within thecomposition. By keeping them in a smooth envelope we end up with an effect that is similar to theuse of compression to control excessive dynamics within particular instruments but without the sideeffects of compression. However, you should be cautious not to over inflate low peaks in music that

    is played with fine touch since in such cases some notes will intentionally be played with less intensitythan others and you may end up undoing that artistic intent.

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    Step 10 Illustration of the peaks and troughs to modifycontinued.

    At this point we now have a complete prototype filter for this track. You can see from the illustrationthat the peak power spectrum curve is contained within a uniform envelope. Note that although thishas been possible with this track and many others, some tracks have spectrums in which producingsuch a smooth envelope would result in the creating a excessive peaking in the average spectrum(common with tracks that have few instruments) and in such cases we need to relax that

    interpretation to allow for a more uniform average spectrum. In essence, what you should be aimingfor is a uniform peak and average spectrum trace when viewed in 1/3rd octave resolution and applyhigh-Q edits to achieve that end. It just so happens that for quite a large number of tracks, followingthe Empathetic Equalisation approach often leads to that uniformity. Where it doesnt is where youwill need to customise your approach to achieve the desired outcome.

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    Final spectrum shape showing a relatively smooth peak trough envelope

    Enabling the original spectrum trace we see that there is a considerable difference between theoriginal and the modified spectrum but importantly all troughs have been retained.

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    Comparison of final spectrum with original spectrum shape

    As a final check on the overall balance it is worthwhile viewing the spectrum shape at 1/3rd octaveresolution as this more closely corresponds to the resolution of human hearing. In this view strongnarrow peaking or dipping is indicative of a filter that possibly could be improved upon. Select 1/3rdoctave resolution by clicking on this button,

    which can be found on the lower right hand corner of the Har-Bal window. In doing so we note thatthe peak spectrum trace is much more uniform than the original shape it had prior to designing ourfilter. These differences in uniformity are readily apparent when listening to the track. This raises thequestion of whether or not to listen to the track whilst editing. As a general rule I would suggest not toas a complete filter response is composed of many edits and each individual edit, whilst having asignificant effect on the overall result, is a minor effect if taken on its own. As such, it is unlikely thatyou can make an accurate judgement on the effectiveness of each edit in isolation. Only once I havea near complete filter response do I find it worthwhile listening to the track whilst editing.

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    1/3 octave resolution spectrum shape comparison

    Another interesting thing to try is comparing the behaviour of intuitQ with Empathetic Equalisation. Ifyou do so you will find results similar to the ones shown below. In the spectrum view we see that asingle application of intuitQ has reduced the intensity of the same areas as our EmpatheticEqualisation approach but with less severity. Also, as intuitQ fitting is primarily driven off the averagespectrum we note that the average spectrum is smoothest for intuitQ whilst in the EmpatheticEqualisation case the peak spectrum is smoothest.

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    1/3 octave resolution spectrum shape comparison between intuitQ and Empathetic EQ

    Turning to the frequency response view the real differences become far more apparent. Here we seethat Empathetic Equalisation has produced a much more extreme equalisation response thoughironically it sounds far from extreme and much better than the intuitQ equalisation. More importantly,it clearly sounds superior to the original mastering, something Id encourage everyone to try, be itwith this track or a problem track of your own.

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    Realised frequency response comparison between intuitQ and Empathetic EQ

    The reason why we can get away with such extreme equalisation and yet have a natural soundingrecording is because those extreme edits are precisely in tune with the music and span a narrowbandwidth.

    On ListeningOn Listening to this track and many others processed using this approach is something quite difficultto adequately describe. Perhaps a revelation is an appropriate description. The typical impression isone of increased clarity, preservation of most of the dynamics, suppression of (digital) harshness,greater intimacy and increased sense of volume. Another way of summarising it in a single sentenceis to say it is like lifting a veil on the recording, or lifting the performance out of a box.

    The most noticeable side effects (which are rarely an issue) is a possible shift of individual instrumentpositions within the mix and a loss of some wetness in recordings with a lot of ambience. In bothcases the increased detail of that which you can now hear more than compensates for the minor and

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    largely inevitable side effects (ie. doing anything to a recording is likely to effect these in some way).

    Suffice to say we feel Empathetic Equalisation is truly a step forward in the art of equalisation but dont take us at our word. Above all, try it out for yourself and should you find problems with the techniquethen wed loved to hear about them. Only through such insights do we have any chance of improving.

    Complete Empathetic Equalisation ExamplesFour complete analysis and filter sets for commercial releases can be found under thetutorial\advanced folder(ie. C:\Program files\Har-Bal 2.3\tutorial\advanced). The albums include:

    Dire Straits Dire Straits Vertigo 800 051-2

    1978 Phonogram Ltd. London

    Foo Fighters There is Nothing Left to Lose BMG 74321715742

    1999 Roswell Records Inc.

    Suzanne Vega Suzanne Vega A&M Records CD 38490

    1985 A&M Records Inc.Tears for Fears The Seeds of Love Fontana 838 730-2

    1989 Phonogram Ltd.

    London

    So Why Does it Work?

    The question remains as to how and why this technique can produce markedly different outcomesthan more traditional approaches, particularly in view of the extremeness of typical realised filterfrequency responses. It is quite natural to assume that the less extreme the processing the moretransparent the sound yet this appears to fly in the face of that common belief. On the other hand,there is another precedent for such spectral modifications that is generally accepted as givingsuperior sound and that is diffuse room ambience.

    We believe the key to understanding why Empathetic equalisation can possibly produce suchoutcomes is to understand first and foremost, that the frequency selectivity of human hearing isfundamentally limited and that the sounds produced by various instruments can be spectrally quitedifferent. More specifically we can loosely argue that the sounds produced by instruments contain acombination of toned (confined to narrow band peaks in the spectrum) and un-toned (spread over awide spectrum) sounds with varying degrees of each for different classes of instruments. Forexample, a typical guitar track will have a spectrum that is predominantly toned and most of thesound energy confined to the harmonics that the instrument produces. In comparison drums, whilsthaving a tonal aspect to them generally produce a great deal of wideband energy not necessarilyconfined to a narrow bandwidth. Human voice is a combination of both in different parts of thespectrum with fricative, plosive and sibilance sounds being wide band sounds. Two examples of

    typical spectrums are shown below (kindly courtesy of Dean Wukstafrom his song Yourecorded inhis studio - Purple Room Studio).

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    Spectrum of a typical guitar track

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    Spectrum of a typical floor tom track

    A typical track is a collage of many different instruments each occupying parts of the spectrum,usually with a great deal of overlap. Because of this overlap masking occurs and if severe enough,can hide much of the detail within the recording. Now if the masking is of a toned sound by anun-toned one, then Empathetic Equalisation can help to unmask that sound. How is this so? Becauseone of the sounds is narrow band and the other is broadband and the frequency selectivity of ourhearing is simply not high enough to hear the spectrum aberrations we are introducing.

    For those not already familiar with the concept of critical bands in human sound perception we shallintroduce it here. With regard to a broad band sound masking a pure tone the critical bandwidth isloosely defined as follows. Consider the case of a pure tone (sine wave) that is being masked by a

    narrow band noise whose band centre is aligned with the pure tone. The presence of the noise willcause a threshold shift in our hearing at that centre frequency of some level (depending on the noiseintensity and bandwidth). Now if we were to increase the bandwidth of the narrow band noise whilstkeeping the noise power constant and centred over the tone then there will be an increase in the levelof masking. However, at some noise bandwidth the level of masking will no longer increase with anincrease in noise bandwidth and that bandwidth is known as the critical bandwidth.

    The mechanism of masking arises because sounds occupying different parts of the spectrum excitedifferent parts of the basilar membrane. When sounds are spectrally close enough or indeed occupythe same part of the spectrum they will excite the same part of the basilar membrane making the two

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    sounds fuse together and become indistinguishable as separate sounds. In the example of narrowband noise masking a pure tone, the point at which we have no further increase in masking withincreasing noise bandwidth is the point at which the noise excites all the frequencies that wouldexcite that one part of the basilar membrane. Any additional noise bandwidth will not result inincreasing level of masking since that increased bandwidth will now be exciting a different part of thebasilar membrane producing a distinct nerve response.

    The critical bandwidth of human hearing changes with frequency and very roughly corresponds toabout 1/3rd octave resolution. To that end, the way we hear the effect of Empathetic Equalisation isroughly equivalent to viewing the spectrum with 1/3rd octave resolution. Doing so it is clear that thetypical Empathetic Equalisation filter produces a smooth spectrum and not the very undulatingspectrum we see in 1/12th octave view.

    This still leaves the question as to why we can reduce masking though. This can be easily illustratedby a similar contrived experiment using two different Har-Bal filter realisations to attenuate a 440Hzsine wave mixed with pink noise by a nominal 5dB. In one filter realisation we use the traditionapproach of cutting a peak directly and in the other realisation we use the Empathetic Equalisationapproach, which creates a response with deep troughs either side of the 440Hz we wish to cut. Thetwo realisations are illustrated below.

    Conventional and Empathetic Equalisation filter realisations

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    If we apply these two filter realisations to the pure tone and the pink noise we obtain the followingresults. Note that the pure tone spectrum measurements show a noise component mixed with thesinusoid. This noise component is not and does not represent the level of the mixed pink noise in thisexperiment but is simply an added noise needed to allow Har-Bal to function properly with a high levelpure tone. Without it added the loudness compensation within Har-Bal applies so much gain that thefixed-point arithmetic used to realise the f ilter is driven into overflow.

    Attenuation of 440Hz tone by conventional and Empathetic Equalisation filter realisations

    In the pure tone case the 1/3 octave spectrum (measured using a separate spectrum analyser on theHar-Bal filtered wave file) amplitudes of the 440Hz peak are the same, which is what we wouldlogically expect to see. However, in the case of the pink noise the amount of attenuation afforded tothe pink noise within that same 1/3 octave band is significantly greater for the EmpatheticEqualisation approach (see below).

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    Attenuation of pink noise by conventional and Empathetic Equalisation filter realisations

    More importantly we note that in the case of a conventional peak cut filter response the tone isattenuated by 4.74dB whilst the noise in that third octave band is attenuated by only 2.04dB. Hencewe have a loss of separation between the noise and the tone with this filter by 2.7dB. In other words,with this filter we have increased the masking of the tone by the noise. In the Empathetic Equalisationapproach the tone is again attenuated by 4.74dB but in this case the noise in that third octave band isnow attenuated by 5.83dB. Hence we have a gain of separation between the noise and the tone withthe Empathetic EQ filter by 1.09dB. In other words, with this filter we have reduced the masking ofthe tone by the noise.

    This behaviour anecdotally agrees with listening tests conducted using the two different approachesto equalisation. That is, when equalisation is performed by peak flattening recordings start to soundmuffled and indistinct (presumably due to increased masking between toned and un-toned sounds)

    whereas when equalisation is performed by the Empathetic Equalisation approach recordings start tosound clearer and better defined (due to reduced masking between toned and un-toned sounds). Thefact that the frequency response looks horribly extreme and lumpy is made irrelevant by the fact thatour ears cant hear that non-uniformity. As such, those extreme filters do not colour the soundappreciably. In much the same way a control room or mastering studio with pleasant ambiencesounds wonderful to the ear but looks horribly non-uniform when measured as a frequency response.

    This concludes the advanced tutorial on Empathetic Equalisation. The theoretical discussion of thistechnique offers a possible explanation but much is yet to be explained. Furthermore, no attempt hasbeen made to prove this to be the fundamental mode of operation of this technique. To do so would

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    require careful experimental design with a large statistical sample for which I dont have the expertisenor the time commitment and resources to conduct. I leave that as a possible research opening for atalented engineer in the field of psycho-acoustics to conduct, if indeed anyone is interested in doingso. As a final remark on Empathetic Equalisation and Har-Bal in general, it is interesting to note thatsuch a technique is simply impossible to conduct without spectrum analysis and a tool like Har-Bal,irrespective of the talent of the mastering engineer. Just as critical bandwidth in human hearing is theachilles heel to Empathetic Equalisation it is the bane of Mastering Engineers as it makes itimpossible for them to hear the peaks that Har-Bal sees. Finally, Id like to thank both Earle Holderand Evan Kendon(Htimaker)for many engaging discussions on this new technique and Dean Wukstafor the inclusion of track analyses from his song You. Without these exchanges this tutorial wouldsurely be lacking in substance.