May 2009 - Sound & Communications

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Figure 2. Polar diagram forwell designed four-foot columnloudspeaker (2kHz): horizontal(red trace) and vertical(blue trace). Attenuation ofsound above and below theloudspeaker (i.e., at 90°) is asubstantial 40dB.have a vertical dispersion angleof around 20° to 30° in the verticalplane, while this would have toreduce to 5° to 10° for a long-throwsituation.To put this into context, the linesource column loudspeakers thatwere installed in the iconic St. Paul’sCathedral in London in the early1950s were 11-foot-high, two-waydevices, with a shorter, three-foothigh-frequency array located in thecenter of the unit alongside the mainlow/mid frequency drivers. Over theyears, for some reason, the laws ofphysics were forgotten (though notrepealed), and marketing people tookover from engineers, with the resultthat line source column loudspeakersbecame shorter and shorter in lengthand, consequently, became less andless effective.Slowly, too, the specialist columnloudspeaker manufacturers eitherdied out or the large brand namesphased them out or succumbed tothe ignorant fashion of making short,but pretty ineffective, column speakers.The column concept, however,remained remarkably popular in Eu-Figure 3. 3D Polarballoon, front on,showing soundradiation on axis to theloudspeaker.NEED JUSTA LITTLECOBRANET?Figure 4. Polar diagram offour-foot column loudspeakerat 250Hz, showing just10-11dB of attenuation at+/-90° off axis (i.e., aboveand below the loudspeaker),with wide vertical main beamcoverage (90°).Introducing the right-sized CobraNet I/O card.The ASI5402 gives you two bi-directional channelsof CobraNet, in an affordable design you can useanywhere. Whether you’re wiring a stadium orconfiguring a studio, the ASI5402 lets you connecteffortlessly. You get our great MRX multi-rate routing/mixing and the extensive software of all our networkaudio products. Windows Vista and Linux drivers, too.To learn more, call us at +1-302-324-5333 or go towww.audioscience.com.Need more CobraNet? The ASI6416 has16 bi-directional channels of CobraNetaudio, plus MPEG record/playback.CobraNet is a registered trademark of Cirrus Logicwww.audioscience.comFigure 5. Polar diagramof two-foot columnloudspeaker at 250Hz,showing only 1-2dB ofattenuation at 90° off axis.16 Sound & Communicationswww.soundandcommunications.com
Figure 6. Sound radiation patternfrom tall phased array loudspeaker.With correct aiming, such aloudspeaker can provide very uniformcoverage without undue excitation ofthe reverberant field.rope despite the fact that most of theproducts on the market were trulyappalling devices.Then, about 10 years ago, the lostart of column loudspeaker designwas rediscovered and, indeed, takento new heights with the introductionof the DSP-based phased array. Thesignificance of source length on controlpattern was re-established, anddecent-sized (length) units began toappear. Their effectiveness in controllingthe excitation of the reverberantfield became legendary andthere are now several manufacturersoffering effective, active-phased arraydevices.Somewhat ironically, the introductionof these highly sophisticated, activedevices has caused a resurgenceof interest in line source technologyin general, and passive, and evenhybrid, array designs have emergedfrom both well-known and not so wellknown manufacturers.Over the past 12 months alone, Ihave seen at least 10 different manufacturersenter the market. Happily,the laws of physics appear not tohave been forgotten, and decentlengthcolumns (e.g., four-foot andabove) with high quality drivers andproper high density driver stacking/spacing are emerging. These newdesigns often also incorporate noveltechniques for providing a moreconsistent high frequency directivitycharacteristic.So, as the column or line sourceloudspeaker is undergoing somethingof a renaissance, lessonsclearly have been learned and the artand science of the format is advancing.Hopefully, however, the marketingpeople can be kept at bay for afew years and there won’t be a resurgenceof the cheap mini columns thathave plagued the last two decades...but, sadly, history often repeatsitself.nLoudspeakerMay 2009 17
Page 1 and 2: Vol. 55 No. 5 May 18, 2009tailoring
Page 3 and 4: The integrator’s dreamPowerful. F
Page 5 and 6: SANYO.XTC50L.SC_May09.pdf SANYO.XTC
Page 7 and 8: Deep beneath the quality sound, yea
Page 9 and 10: NEWSLETTERATLAS SOUND ACQUIRES ALL
Page 12 and 13: Why Aren’t AV Manufacturers Lever
Page 14 and 15: Line Source Column LoudspeakersA ne
Page 18: Sound DirectionsFocused audio impro
Page 22 and 23: InfoComm 100A step in the right dir
Page 24: A Microcosm Of ProgressBeallwood Ba
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May 2009 - Sound & Communications

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