AES 51 International Conference Loudspeakers and .AES 51 st International Conference Loudspeakers

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Helsinki, Finland is known for having two sea-sons: August and winter (adapted from Con-nolly). However, despite some torrential rain inthe previous week, the weather during the conferencewas excellent. The conference was held at the HelsinkiCongress Paasitorni, which was built in the firstdecades of the twentieth century. The recently restoredbuilding is made of granite that was dug from theground where the building now stands. The locationnear the city center and right by the harbor proved tobe an excellent location both for transportation andthe social program.

An unexpectedly large turnout of 130 people almostoverwhelmed the organizers as over 75% of themregistered around the time of the early bird cut-offdate. Twenty countries were represented with most ofthe participants coming from Europe, but some camefrom as far away as Los Angeles, San Francisco, Lima,Rio de Janeiro, Tokyo, and Guangzhou. Companiessuch Apple, Beats, Comsol, Bose, Genelec, Harman,KEF, Neumann, Nokia, Samsung, Sennheiser, Skype,and Sony were represented by their employees.Universities represented included Aalto (in Helsinki),Aalborg, Budapest, and Kyushu.


AES 51st International Conference

Loudspeakers and Headphones

2124 August 2013Helsinki, Finland

790 J. Audio Eng. Soc., Vol. 61, No. 10, 2013 October


J. Audio Eng. Soc., Vol. 61, No. 10, 2013 October 791

Juha Backmann insists that Reproducedaudio WILL be better in the future.

A packed House of Science and Lettersfor the Tutorial Day



The conference was chaired by the ever-exuberant JuhaBackman, and the excellent papers were collated and reviewed byAki Mkivirta. They were assisted by an able committee consistingof Andrew Goldberg (sponsors), Ilkka Huhtakallio (publicity andeverything else), Asta Krkkinen (demos), Julia Turku (treasurer),Jussi Rm (website), Miikka Tikander (facilities), and MarkusVaalgamaa (social program). From Aalto University, Lauri Mela,Pekka Rnkk, and Jukka Saarelma stepped in at the last minute togive additional support to the committee.

TUTORIAL DAYJuha Backman welcomed everyone to the tutorial day. This was aspecial event held at the House of Science and Letters and organ-ized in conjunction with the Finnish Acoustical Society and theAudio Engineering Society. Graham Boswell then introduced theAudio Design Workshop for Loudspeakers. This was the first timethe AES had done a webcast from a conference and over 160 peopletuned in, which more than doubled the total audience to almost300 people. The workshop was jointly run by Prism Sound, OxfordDigital, Texas Instruments, Klippel, Loudsoft, and Audio EMC, andwas a repeat of a similar event held a few months ago in Cam-bridge, UK. This was an opportunity to hear about practical experi-ences in analog and digital audio design, and to see the latest devel-opments in technology. Wolfgang Klippel in his typically infectious, enthusiastic, and

confident style discussed his ongoing efforts to define and developmeaningful audio performance metrics for todays smart devices.

So many areas werecovered in such a shortspace of time that its notpossible to even attemptto summarize thecontent here in thissmall space. One simplyhas to see Klippel inaction to understandthis. Peter Larson ofLoudsoft then explainedhow the loudspeakerdevelopment process canbe greatly streamlinedwith modern CAD tools.Motors for small drivers,bass alignments, and

low-frequency performance can still be designed using Thiele-Small parameters in a simulation, and the effect of individualparameters (such as voice coil length and pole piece size) on thesystem performance can be seen directly. John Richards of OxfordDigital showed us how the application of DSP techniques can maxi-mize compact loudspeaker performance within a given budget andfootprint. Even as products shrink in size, customer expectationsare rising, but DSP can be used to counteract these contradictorydemands. Lars Risbo of Texas Instruments addressed the perform-ance benefits afforded by a system-level approach to active loud-speaker design, as opposed to optimizing individual components inisolation. Looking at it this way means that overall system limita-tions come from peak excursion or the thermal average. SimonWoollard of Prism Sound demonstrated how modern digital audioanalysis techniques can provide far greater and more rapid insightinto system performance. A practical demonstration showed meas-urements of digital interfacing bit transparency, drop outs, andglitches. Bin-based multitone FFT rapidly acquires many curves ina short time (approximately 30 per minute) and measures THD+N,adding filtering can give THD or N only. For acoustical measure-ments, swept sine waves are often used to calculate an impulseresponse, whereupon windowing extracts the distortion harmonics.Anthony Waldron of Audio EMC provided practical solutions to theoften-overlooked problems of electromagnetic interference and itsimpact on audio system performance. Old amplifiers can still passmodern EMC tests due to the shielding provided by metal cases.Now radio interference comes from mobile phones, computers,SMPS, lighting, and motors. Interconnecting cables act as antennaand audio frequency pickup occurs because audio circuits candemodulate RF. Ground loops can be avoided by connecting themetal chassis of the equipment to metal trucking of the installationand clamping the cable shielding to the metal case. Common-modefilters and power supply decoupling also help. A good ground planeis essential and can improve EMC performance by tens of dB.After the workshop we visited the National Library of Finland. In

the audio department they are about halfway through a digitizingproject. Currently all the Finnish 78 rpm records have beensuccessfully digitized and now they have approximately 150,000recordings from throughout the Finnish history. The earliest one isfrom 1901, and about 80% of all Finnish recordings can be heardby appointment.Following the library visit we were bussed over to the Aalto

Universitys Espoo campus for a barbecue and sauna evening.Traditional Finnish makkara (a sausage primarily consisting of fatand water that needs some serious burning before it has any tasteat all) was served together with slightly more healthy salad andslightly less healthy Finnish beer. Judging by the noise and smiles,

792 J. Audio Eng. Soc., Vol. 61, No. 10, 2013 October

Wolfgang Klippel tells everyone to Settle down now.

Sauna, beer, and makkara on the beach.Simon Woollard tries subterfuge to gethis turn on stage a bit earlier.


this proved to be a very popular ice breaker. The stillness of thetrees and bright shining moon in the clear sky added to the atmosphere which set the scene nicely for the official start of theconference.

DAY ONEJuha Backman officially welcomed everyone to the conference andintroduced the committee. Then Aki Mkivirta introduced thekeynote speech by Ilpo Martikainen of Genelec. He explored theevolution and history of studio monitoring loudspeakers andexplained that we know a lot about loudspeakers, however there isstill a long way to go. Sound sources have many different directivi-ties but the loudspeaker has only one.He asked what the reference is: akitchen radio or the best possible tech-nology? Humans and rooms are alsopart of the listening experience andthey vary greatly, also loudspeakershave a frequency response, distortions,and directivity. While the goal haschanged from the AM radio era tohigher quality today, the basic princi-ples of loudspeakers are unchangedsince the early 1900s. Basic humanperception has also been well under-stood for many decades, however ittakes a long time for research tobecome accepted by the mainstream.Martikainen then toured through vari-ous design aspects seen in studio mon-itoring such as coaxial drivers, beryl-lium and soft cones, directivity(mid-high frequencies and also bass),room response controls, edge diffrac-tion and cabinet shapes, motional feed-back, amplifier output impedance,compression horns, the room interfaceand perceived audio quality, and mostrecently DSP processing. He concluded by noting how many of thefeatures seen in todays designs originally came from demandsmade by broadcasters, and that loudspeakers for professional appli-cations have a much longer lifetime (typically 1020 years) thanconsumer products. Over the years, size has been reduced, materi-als have improved, frequency responses are flatter, directivity con-trol is smoother, knowledge of perception is better understood,electronic equalization is more extensive, and prices have dropped.Aki Mkivirta then chaired the loudspeakers and applications

session, which started with a description given by Dodd of thedevelopment of the KEF LS50 that has a coaxial driver arrange-ment. In a model, a radial channel waveguide is used to optimizethe controlled directivity producing a spherical wave front to give awide and even dispersion, with the driver surround having a mini-mized diffraction. The cabinet, driver, and port were analyzed inanother model to show how they perform as a complete system,and this prompted some design changes. Daniel Beer then followedwith an exploration of the influence of flat loudspeaker enclosureson the e