Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. V O L U M E 2 9, I S S U E 4 F E B R U A R Y 2 0 1 6 IN THIS ISSUE 1 INDUSTRY NEWS & DEVELOPMENTS By Vance Dickason 4 PRODUCTS & SERVICES 6 DIRECTORY 14 ACOUSTIC PATENTS 18 TEST BENCH Cone Focus 29 By Vance Dickason Solopreneur Hotline Free Help and Encouragement for Small Business Owners Angelo Spandrio learned how to run a business the hard way, making mistakes that cost him time and money. Yet in spite of those mistakes, he has a successful home-based business that has supported his family for more than 20 years. Now he s giving back to the community by helping other business owners with his advice and guidance through the Solopreneur Hotline (www.solopreneurhotline.com). According to Spandrio, Three years ago, I thought that perhaps I could help other small business owners dodge some of the mistakes I made. That thought gave birth to the Solopreneur Hotline. Spandrio s Solopreneur Hotline services are completely free. There is no coaching package or ebook for sale here. He says, I know how frustrating it is to find the answers you want when you re first starting out. All business owners, even us more seasoned ones, have issues that keep us awake at night. I love chatting and coming up with some ideas to ease those burdens. Spandrio will even do a lot of the research to help Two High-End Tweeters from Morel and SB Acoustics, Plus a Midwoofer from Dayton Audio By Vance Dickason By Mike Klasco Industry News & Developments By James Croft INDUSTRY WATCH By Vance Dickason solve specific problems entrepreneurs bring to him. His expertise includes start-up, licensing and permits, accounting, taxes, purchasing and billing, and more. Spandrio s journey to becoming a solopreneur began more than 35 years ago when he became fed up with the 8 to 5 grind and started AMS Audio Enterprises, Inc. (www.ams-enterprises.com), which is still going strong. AMS started out producing products for the audio industry. Now, in addition to working with the audio industry, AMS has become a manufacturing resource for companies who need assistance with offshore production. It also sources different goods from offshore and is able to produce products from your design or a sample. Through AMS, Solpreneur offers: Experienced importing services Expert guidance for international transactions with offshore suppliers Overseas pricing combined with domestic support Shipments to anywhere in the world direct from Asia or from its California facility Highly responsive freight forwarding partner Engineering services mechanical design, CAD, and solid modeling support Spandrio s experience enables him to provide sound
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. Test Bench Two High-End Tweeters from Morel and SB Acoustics, Plus a Midwoofer from Dayton Audio By Vance Dickason Two of the drivers are high-end home audio tweeters from Morel and SB Acoustics. From Morel, I received its latest addition to the Supreme tweeter line, the Titanium Supreme Coppersleeve Tweeter (TSCT) 1044, and from SB Acoustics Satori high-end line of drivers, the Satori TW29RN. The final driver is Dayton Audio s new 4.5 diameter carbon fiber cone midwoofer, the CF120-4. The TSCT 1044 The first driver is the new soft dome tweeter from highend Israeli OEM driver manufacturer Morel s Supreme product line, the 28 mm TSCT 1044 (see Photo 1). As part of the Supreme line, the TSCT 1044 and the similar TSCT 1144 (which is the same tweeter with a larger faceplate) are both an entirely new design for Morel and incorporates the company s Improved Dispersion Recess (IDR) faceplate design, which is a shaped inset in the round metal faceplate. The shape is intended to increase the high-frequency output in the tweeters off-axis response. Additional features for the TSCT 1044 include a 28 mm Acuflex hand-coated fabric dome, a 104 mm IDR metal faceplate, a vented flat pancake ring-type neodymium magnet structure, a Hexatech hexagonalshaped aluminum voice coil wire (originally licensed from Dynaudio) wound on a titanium former, an underhung 1.125 diameter voice coil (4 mm gap and 2 mm coil height), a replaceable voice coil assembly, a damped die cast aluminum rear cavity, magnetic fluid in the gap for enhanced cooling, and gold-plated terminals. Because of the motor configuration, the top of the magnetic return path (pole piece) is about % open, providing a relatively small reflective surface beneath the dome. The remaining surface is damped with a round donut shaped felt ring. Last, the Din power handling specification for this tweeter is a robust 200 W. To begin, I created an impedance plot using a LMS 300-point impedance sine wave sweep (see Figure 1). The tweeter resonance occurs at 594 Hz, with the obvious damping from the large rear cavity and magnetic fluid. With a R EVC =4.04 Ω, the minimum impedance for this tweeter is 4.56 Ω at 5.2 khz. I recess mounted the TSCT 1044 in an enclosure that had a baffle area of about 17 8 and measured the 20 10 5 2 Ohm Impedance vs Freq 1 10 Hz 20 200 0 1K 2K 5K 10K 20K K Figure 1: Morel TSCT 1044 free-air impedance plot 300 Hz 0 1K 2K 5K 10K 20K K Figure 2: Morel TSCT 1044 on-axis response Photo 1: The 28-mm TSCT 1044 is Morel s new soft dome tweeter from its Supreme product line. 300 Hz 0 1K 2K 5K 10K 20K K Figure 3: Morel TSCT 1044 horizontal on- and off-axis frequency response (0 = solid; 15 = dot; 30 = dash; = dash/dot) 18 VOICE COIL
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. on- and off-axis frequency response at 2.83 V/1 m with a -point gated sine wave sweep from khz to 300 Hz. Figure 2 shows the on-axis response. The TSCT 1044 s frequency response is a gently rising slope and a smooth ±2.2 db from 1.5 khz to 10 khz, with the low-pass rolloff beginning at about 20 khz. Figure 3 depicts the TSCT 1044 s on- and off-axis response. You can easily see the effect of the Morel-shaped IDR faceplate. Off-axis, the device is only 3 db down at 13 khz from the on-axis response with respect to the 30 off-axis curve and 4 db at off-axis (also at 13 khz), again with respect to the 30 off-axis response. This is a nice improvement over the typical 1 soft dome type tweeter off-axis response 5 Ratio vs Freq dbr above 10 khz. Figure 4 shows another view of the off-axis response in the normalized on- and off-axis plot. Figure 5 gives the two-sample SPL comparison, indicating the two samples were well matched. Of course this is the kind of consistency you expect from a company such as Morel. Next, I used the Listen, Inc., SoundCheck analyzer to measure the impulse response with the tweeter recess mounted on the same baffle that I used to measure the TSCT 1044 s frequency response. Importing this data in the Listen SoundMap software produced the cumulative spectral decay plot (waterfall) shown in Figure 6. Figure 7 shows the Short Time Fourier Transform (STFT) displayed as a multi-color surface plot. Last, I set the 1 m sound pressure level (SPL) to 94 db (3.03 V), and 0-5 -10-15 -20-25 -30-35 - - 300 Hz 0 1K 2K 5K 10K 20K Figure 4: Morel TSCT 1044 normalized on and off-axis frequency response (0 = solid; 15 = dot; 30 = dash; = dash/dot) K 300 Hz 0 1K 2K 5K 10K 20K K Figure 5: Morel TSCT 1044 two-sample SPL comparison FEBRUARY 2016 19
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. Figure 6: Morel TSCT 1044 SoundCheck CSD waterfall plot The TW29RN Test Bench has discussed several SB Acoustics tweeters including the ferrite motor 29-mm ring dome SB29RDC-C000-4 (August 2009), its neodymium 29-mm ring dome version, the SB29RDNC-C000-4 (August 2011), the SB26STCN-C000-4 1 neodymium motor tweeter and the ferrite version of the SB26STCN, the 1 SB26STAC-C000-4. However. it s worth repeating that all the Sinar Baja transducers are developed by former Danish Vifa/Scan-Speak engineers Ulrik Schmidt and Frank Nielsen, who are co-owners of Danesian Audio (www.danesian.dk) This month, SB Acoustics sent its new high-end Satori line neodymium 29-mm ring dome, the TW29RN. Features Figure 7: Morel TSCT 1044 SoundCheck STFT surface intensity plot Photo 2: SB Acoustics sent its new high-end Satori line neodymium 29-mm ring dome, the TW29RN. Ohm Impedance vs Freq 20 10 5 2 1 10 Hz 20 200 0 1K 2K 5K 10K 20K K Figure 9: Satorie TW29RN free-air impedance plot 105 Figure 8: Morel TSCT 1044 SoundCheck distortion plots the analyzer range to 1 khz to 20 khz. Then, I measured the second and third harmonic distortion at 10 cm (see Figure 8). The new TSCT 1044 is another well-conceived tweeter from Morel engineering. For more information on the TSCT 1044 tweeter and other Morel OEM drivers, visit www.morelhifi.com. 300 Hz 0 1K 2K 5K 10K 20K K Figure 10: Satorie TW29RN on-axis response 20 VOICE COIL
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. include a 29-mm wide surround coated cloth ring-type diaphragm, a non-reflective cast-aluminum rear cavity, a two-part aluminum faceplate with integrated mechanical decoupling, dual balanced compression chambers, high saturation neodymium ring type motor magnet with a T-shaped pole and dual copper shorting rings (Faraday shields), a copper-clad aluminium wire (CCAW) wound voice coil, a foam mounting gasket, and gold-plated terminals. Unlike the ring domes from Vifa and Scan-Speak, the SB Satori version does not use an external phase plug. It simply has an indent where the center of the dome is attached to an interior post. Part of the reason for this is that the only thing that was patented on the first Vifa XT 105 300 Hz 0 1K 2K 5K 10K 20K K Figure 11: Satorie TW29RN horizontal on- and off-axis frequency response (0 = solid; 15 = dot; 30 = dash; = dash/dot) 5 dbr Ratio vs Freq 0-5 -10-15 -20-25 -30-35 - - 300 Hz 0 1K 2K 5K 10K 20K K Figure 12: Satorie TW29RN normalized on- and off-axis frequency response (0 = solid; 15 = dot; 30 = dash; = dash/dot) 105 300 Hz 0 1K 2K 5K 10K 20K K Figure 13: Satorie TW29RN two-sample SPL comparison FEBRUARY 2016 21
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. ring dome was the phase plug. However, I don t think this patent was ever too rigorously enforced as I have seen several China-made versions. I began testing using the LinearX LMS analyzer to produce the 300-point impedance sweep shown in Figure 9. The magnetic fluid damped resonance occurs at a moderately low 5 Hz. With a 3.03 Ω DCR, the Figure 14: SB Satorie TW29RN SoundCheck CSD waterfall plot Figure 15: SB Satorie TW29RN SoundCheck STFT surface intensity plot minimum impedance for this tweeter is 3.28 Ω at 3.6 khz. Following the impedance test, I recess mounted the TW29RN in an enclosure that had a baffle area of 17 8 and measured the on- and off-axis frequency response with a -point gated sine wave sweep at 2.83 V/1 m. Figure 10 shows the on-axis response to be a very flat ±2.3 db from 1.5 khz to 30 khz, with the SPL extending out to khz. Figure 11 depicts the TW29RN s on- and off-axis response. Figure 12 shows the off-axis curves normalized to the on-axis response. Figure 13 shows the two-sample SPL comparison, indicating the two samples were closely matched, with a small 1 db variation between 2.2 khz to 3.8 khz. Next, I used the Listen SoundCheck analyzer along with the Listen SCM 0.25 microphone (provided courtesy of Listen, Inc.) to measure the impulse response with the tweeter recess mounted on the test baffle. Importing this data into the Listen SoundMap software produced the cumulative spectral decay plot (usually referred to as a waterfall plot) shown in Figure 14. Figure 15 shows a STFT displayed as a surface plot. For the final test procedure, I set the 1 m SPL to 94 db (2.3 V) using a noise stimulus, and measured the secondnd and third harmonic distortion at 10 cm (see Figure 16). Since I know that Frank and Ulrik (Danesian Audio) spend a lot of time listening to various iterations of a driver as they go through the development process, I m guessing this is a very fine sounding product. For more information on the Satori TW29RN and other SB Acoustics drivers, visit www.sbacoustics.com. The CF120-4 The last driver is a new carbon fiber cone 4.5 diameter midbass driver from Dayton Audio, the CF120-4 (see Photo 3). Features for the CF120-4 include a pin-cushionstyle four-spoke cast-aluminum frame. While the area below the suspended spider mounting shelf is closed, cooling is provided by an 8 mm pole vent. For the cone assembly, Dayton Audio chose a rather stiff curved profile woven carbon fiber cone with a 1.13 diameter convex woven carbon fiber dust cap. Carbon fiber has some interesting acoustic properties, but the cool factor is Figure 16: SB Satorie TW29RN SoundCheck distortion plots Photo 3: Dayton Audio s new carbon fiber cone 4.5 diameter midbass driver, the CF120-4, is shown in front and rear views. 22 VOICE COIL
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. Impedance vs Freq Ohm TSL Model 20 10 5 2 1 10 Hz 20 200 0 1K 2K 5K 10K 20K Figure 17: Dayton Audio CF120-4 midwoofer 1 V free-air impedance plot pretty intense. Compliance is provided by an nitrilebutadiene rubber (NBR) surround, which is nicely designed with a shallow discontinuity where it attaches to the cone edge. The remaining compliance comes from a 2.5 diameter elevated black cloth spider. The CF120-4 s motor design incorporates an 88 mm 15 mm ferrite magnet sandwiched between black emissive coated T-yoke back-plate and front-plate. This also includes a copper cap shorting ring (Faraday shield) installed on the pole piece. The CF120-4 uses a black anodized 25.4 mm diameter aluminum voice coil former, wound with round copper wire, and terminated to a standard set of solderable terminals. In terms of physical appearance, this is very good-looking driver. I commenced analysis of the CF120-4 using the LinearX LTD Model Sample 1 Sample 2 Sample 1 Factory Sample 2 FS 53.6 Hz 53.6 Hz 52.4 Hz 53.8 Hz 532 Hz REVC 3.5 3.53 3.5 3.53 3.4 Sd 54.1 54.1 54.1 54.1 51.5 QMS 1.91 1.91 1.69 1.58 1.89 QES 0.34 0.34 0.33 0.31 0.32 QTS 0.29 0.29 0.28 0.25 0.28 VAS 5.3 ltr 5.3 ltr 5.7 ltr 5.5 ltr 4.9 ltr SPL 2.83 V.7 db.7 db.6 db 86 db 89.1 db XMAX 3.5 mm 3.5 mm 3.5 mm 3.5 mm 3.5 mm Table 1: Dayton Audio CF120-4 data comparison LMS analyzer and VIBox to create both voltage and admittance (current) curves with the driver clamped to a rigid test fixture in free-air at 0.3, 1, 3, 6, and 10 V. As I would expect, I had to discard the 10 V as they were too nonlinear for LEAP to get a good curve fit. As has become the protocol for Test Bench testing, I no longer use a single added mass measurement to determine VAS. Instead, I use the actual measured cone assembly mass (Mmd) supplied by the driver manufacturer, which was 6.7 grams for the Dayton 4.5 woofer. Next, I post-processed the 10 5 point-stepped sine wave sweeps for each CF120-4 sample and divided the voltage curves by the current curves (admittance) to derive impedance curves, phase added by the LMS calculation method. I imported them, along with the accompanying voltage curves, to the LEAP 5 Enclosure Shop software. Since most Thiele-Small (T-S) data provided by OEM FEBRUARY 2016 23
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. 110 105 10 Hz 20 200 0 1K Figure 18: Dayton Audio CF120-4 computer box simulations (black solid = sealed @ 2.83 V; blue dash = vented @ 2.83 V; black solid = sealed @ 30 V; blue dash = vented @ 30 V) manufacturers is generated using either the standard model or the LEAP 4 TSL model, I additionally created a LEAP 4 TSL parameter set using the 1 V free-air curves. I selected the complete data set, the multiple voltage impedance curves for the LTD model, and the 1 V impedance curve for the TSL model in LEAP 5 s transducer derivation menu and created the parameters for the computer box simulations. Figure 17 shows the 1 V freeair impedance curve. Table 1 compares the LEAP 5 LTD, TSL, and the factory published parameters for both of Dayton Audio CF120-4 samples. 8m Sec Time vs Freq 6m 4m 2m 0 10 Hz 20 200 0 1K Figure 19: Group delay curves for the 2.83 V curves in Figure 18 Figure 22: Klippel analyzer Bl symmetry range curve for the Dayton Audio CF120-4 10m M Excursion vs Freq 9m 8m 7m 6m 5m 4m 3m 2m 1m 10 Hz 20 200 0 1K Figure 20: Cone excursion curves for the 30 V curves in Figure 18 Figure 23: Klippel analyzer mechanical stiffness of suspension KMS(X) curve for the Dayton Audio CF120-4 Figure 21: Klippel analyzer Bl(X) curve for the Dayton Audio CF120-4 Figure 24: Klippel analyzer KMS symmetry range curve for the Dayton Audio CF120-4 24 VOICE COIL
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. Figure 25: Klippel analyzer L(X) curve for the Dayton Audio CF120-4 The CF120-4 s LEAP parameter calculation results were close to the published factory data. Following my normal protocol, I used the LEAP LTD parameters for Sample 1 to set up computer enclosure simulations. I programmed two computer box simulations into LEAP 5, both recommended by Dayton Audio. The first was a sealed enclosure with a 34.6 in 3 volume with % fiberglass fill material, and a vented box with a 103.7 in 3 volume tuned to 84 Hz with 15% fiberglass damping material. Figure 18 shows the CF120-4 s results in the vented and sealed boxes at 2.83 V and at a voltage level sufficiently high enough to increase cone excursion to 4.02 mm (X MAX + 15%). This produced a F3 frequency of 300 Hz 0 1K 2K 5K 10K 20K Figure 26: Dayton Audio CF120-4 on-axis frequency response 300 Hz 0 1K 2K 5K 10K 20K Figure 27: Dayton Audio CF120-4 on- and off-axis frequency response (black solid = 0, blue dot = 15, green dash = 30, purple dash/dot = ) MONTREAL SHOW Bonaventure Hotel, 18-20 March 2016 Premium Hi-Fi Top brands Product launches Seminars Streaming systems Headphones Vinyl Turntables Accessories New Pro Studio Zone and much, much more /montrealaudioshow /SSIexpo salonsonimage.com EARLY BIRD TICKETS NOW ON SALE INTERESTED IN EXHIBITING? BOOK NOW WITH ROBERT / 613-258-13 / robert@chestergroup.org FEBRUARY 2016 25
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. 159 Hz (F6 = 129.5 Hz) with a Q TC = 0.78 for the sealed enclosure and 3 db = 99.6 Hz (F6 = 84 Hz) for the vented alignment. Increasing the voltage input to the simulations until the maximum linear cone excursion was reached resulted in 107 db at 30 V for the closed box enclosure simulation and 108 db for the same 30 V input level for the larger vented box. Figure 19 shows the CF120-4 s 2.83 V group delay curves. Figure 20 shows the CF120-4 s 30 V excursion curves. The vented box example reached 4 mm of excursion at about Hz, so adding a steep 24 db/octave high-pass active filter located about to Hz would prevent over excursion and distortion for vented box example by a substantial margin. The CF120-4 s Klippel analysis produced the Bl(X), K MS (X) and Bl and K MS symmetry range plots shown in Figures 21 24. (Our analyzer is provided courtesy of Klippel GmbH. Patrick Turnmire of Redrock Acoustics 300 Hz 0 1K 2K 5K 10K 20K performed the analysis. For additional information, visit www.redrockacoustics.com). The CF120-4 s Bl(X) curve is symmetrical and pretty typical for a small 4.5 woofer (see Figure 21). Looking at the Bl symmetry plot, this curve shows a fairly constant, but small (0.3 mm) coil-out offset (see Figure 22). Figure 23 shows the CF120-4 s K MS (X) curve, which is definitely not as symmetrical in both directions as the Bl curve, but shows a decreasing coil-out offset that gets to about 1.2 mm at the physical X MAX position. Figure 24 shows the CF120-4 s K MS symmetry range curve. The CF120-4 s displacement limiting numbers (calculated by the Klippel analyzer) were XBl at 82% Bl = 4 mm and for crossover (XC) at % C MS minimum was 4.3 mm. For the CF120-4, the Bl is the most limiting factor for prescribed distortion level of 10%, However, both numbers were greater than the driver s physical X MAX. Figure 25 gives the CF120-4 s inductance curves Le(X). Inductance will typically increase in the rear direction from the zero rest position as the voice coil covers more pole area. However, since this driver employs a copper pole cap, the inductive swing is minimized. The result is a fairly minor inductance swing with inductive variation of only 0.04 to 0.05 mh from the resting position to the in and out X MAX positions, which is good performance in any driver. Next, I mounted the CF120-4 in an enclosure that had a 15 6 baffle and was filled with damping material (foam). Then, I measured the device under test (DUT) on and off axis from 300 Hz to 20 khz frequency response at 2.83 V/1 m and I set the LinearX LMS analyzer to a - point gated sine wave sweep. Figure 28: Dayton Audio CF120-4 midwoofer two-sample SPL comparison Figure 30: Dayton Audio CF120-4 woofer SoundCheck CSD waterfall plot Figure 29: Dayton Audio CF120-4 SoundCheck distortion plot Figure 31: Dayton Audio CF120-4 midwoofer SoundCheck Wigner-Ville plot 26 VOICE COIL
Voice Coil. Reprinted by permission. Entire contents copyright 2016 Segment, LLC. All rights reserved. For subscription information, go to www.audioxpress.com, call 0-269-6301, or e-mail voicecoil@pcspublink.com. Figure 26 gives the CF120-4 s on-axis response, indicating a fairly flat response with a 3 to 4 db plateau between 1 to 2 khz, followed by a smooth rise from 2.5 khz to about 9 khz where it begins is low-pass rolloff. Figure 27 displays the on- and off-axis frequency response at 0, 15, 30, and. The 3 db frequency at 30 off axis relative to the on-axis SPL is about 2.8 khz, suggesting a crossover between 2 to 3 khz should be appropriate. Figure 28 shows the CF120-4 s two-sample SPL comparisons, with a 0.25 to 0.5 db match throughout the operating range up to 5 khz. For the remaining tests, I used the Listen SoundCheck software, SoundConnext analyzer, and SCM microphone to measure distortion and generate time-frequency plots. For the distortion measurement, I rigidly mounted the CF120-4 in free air and used a noise stimulus to set the SPL to 94 db at 1 m (6.04 V). I measured the distortion with the microphone placed 10 cm from the dust cap. Figure 29 shows the distortion curves. I used SoundCheck to get a 2.83 V/1 m impulse response and imported the data into Listen s SoundMap Time/Frequency software. Figure 30 shows the resulting CSD waterfall plot. Figure 31 shows the Wigner-Ville plot (used for its better low-frequency performance). Overall, the CF120-4 has great cosmetics and delivers good performance from a 4.5 midbass driver. For more information about Dayton Audio products, visit www.daytonaudio.com. VC Submit Samples to Test Bench Test Bench is an open forum for OEM driver manufacturers in the industry and all OEMs are invited to submit samples to Voice Coil for inclusion in the monthly Test Bench column. Driver samples can be for use in any sector of the loudspeaker market including transducers for home audio, car audio, pro sound, multi-media or musical instrument applications. Any woofer, midrange or tweeter an OEM manufacture feels is representative of their work, is welcome to send samples. However, please contact Voice Coil Editor Vance Dickason, prior to submission to discuss which drivers are being submitted. Samples should be sent in pairs and addressed to: Vance Dickason Consulting 333 S. State St., #152 Lake Oswego, OR 934 (3-7-0427) vdconsult@comcast.net All samples must include any published data on the product, patent information or any special information necessary to explain the functioning of the transducer. This should include details regarding the various materials used to construct the transducer such as cone material, voice coil former material, and voice coil wire type. For woofers and midrange drivers, please include the voice coil height, gap height, RMS power handling, and physically measured Mmd (complete cone assembly including the cone, the surround, the spider, and the voice coil with % of the spider, surround and lead wires removed). For Over 35 Years ACOustics begins with ACO Measurement Microphones Polarized and Electret Community/Industrial Noise Monitors/Alarms Indoors and Out Windscreens 3 to18 inch & Custom Weather/UV Resistant Microphone Systems Standalone IEPE Powered Phantom Power Custom ACO Pacific, Inc www.acopacific.com sales@acopacific.com Tel: +1-6-5-88 GUANGZHOU FEB 29- MAR 3, 2016 HALL 4.1 - BOOTH - F08 FRANKFURT APR 5-8, 2016 HALL 8.0 - BOOTH - B48 FEBRUARY 2016 27