volume 27, issue 11 september 2013 - dayton audio voice coil review... · volume 27, issue 11...

IN THIS ISSUE

V O L U M E 2 7 , I S S U E 1 1 S E P T E M B E R 2 0 1 3

27

INDUSTRY NEWS & DEVELOPMENTSBy Vance Dickason

1

Industry News & DevelopmentsBy Vance Dickason

5

ACOUSTIC PATENTSBy James Croft

10

PRODUCTS & SERVICES

14

The room plays a huge role in a home theater system’s performance. A good design starts with room location, size, and shape. It also takes other factors into consideration (e.g., lighting, sight lines, and sound transmission). Learn how being a good room designer can make you a better theater designer. At the conclusion of this course, partici-pants should be able to:

• Discuss room basics• Determine form following function• Identify construction considerations for isolation and

bass response

CEDIA Expo 2013—Evolving Technologies in the Integrated Home

This year’s CEDIA (Custom Electronic Design & Installation Association) Expo event is scheduled for September 25–28 at the Colorado Convention Center in Denver, CO. CEDIA University is providing a variety of workshops, classes, and seminars related to the audiovisual (AV) installation industry. Courses include:

Fundamentals of Home Theater Design, Instructor: Jeff Gardner—This course is the starting point for all other training in home theater system design. At the conclusion of this course, participants should be able to:

• Understand the history of home cinema• List basic components and configurations• Describe audio and video signal types and sources• Gain insight about surround sound fundamentals

and video display options• Identify seating, room, viewing distance, and

lighting considerations

Home Theater Room Design, Instructor: Sam Cavitt—

TEST BENCH Two Pro Sound Drivers and a Home Audio SubwooferBy Vance Dickason

INDUSTRY WATCH By Vance Dickason

Photo 1: CEDIA Expo 2012 attendees gather inside the Colorado Convention Center.

Voice Coil. Reprinted by permission. For subscription information, call 800.269.6301, or visit www.voicecoilmagazine.com. Entire contents copyright © Segment, LLC. All rights reserved.

SEPTEMBER 2013 19

Photo 2: Dayton Audio’s PM220-8 is well-suited as a midbass or midrange driver in a multi-way speaker system.

SoundMap time-frequency software (now included with SoundCheck V. 12). Figure 15 shows the resulting CSD waterfall plot. Figure 16 shows the Wigner-Ville (with its better low-frequency performance) plot.

The AN3510 is a well-designed, finely crafted 3.5” full-range array driver. Given the increasing popularity of line arrays in musical instrument (MI) and public address (PA) applications, this is an important product line for Celestion. For more information, visit www.celestion.com.

The PM220-8The next driver I tested this month is the wide bandwidth

8” PM220-8, which is a new one from the Dayton Audio OEM division (see Photo 2). This driver is similar to the PS220 full-range 8” featured in Voice Coil October 2011. However,

Figure 17: Dayton Audio PM220-8 woofer 1 V free-air impedance plot

10 Hz 20 50 100 200 500 1K 2K 5K 10K 20K

Ohm

1

2

5

10

20

50

100

200

Impedance vs Freq

TSL Model LTD Model Factory

Sample 1 Sample 2 Sample 1 Sample 2

FS 45.4 Hz 46.9 Hz 43.8 Hz 41.9 Hz 43.1 Hz

REVC 6.21 6.27 6.21 6.27 6.3

Sd 0.0214 0.0214 0.0214 0.0214 0.0205

QMS 6.57 5.86 6.21 5.03 6.54

QES 0.37 0.38 0.38 0.35 0.35

QTS 0.35 0.36 0.36 0.33 0.34

VAS 71 ltr 66.5 ltr 76.6 ltr 83.8 ltr 73.8 ltr

SPL 2.83 V 94.4 dB 94.4 dB 94.1 dB 94.3 dB 95 dB

XMAX 4.6 mm 4.6 mm 4.6 mm 4.6 mm 4.6 mm

Table 2: Comparison data for the Dayton Audio PM220-8


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mailto:[email protected]

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20 VOICE COIL

unlike the PS220 which is intended for use in a single-driver speaker, the PM220-8 is a wide bandwidth version intended for use as a midbass or midrange driver in a multi-way speaker system. The PM220-8’s features are similar to the PS220. Starting with the frame, the PM220-8 utilizes a cast aluminum frame incorporating six 5-mm diameter, round vent holes in the area below the spider-mounting shelf for enhanced voice coil cooling as well as providing a heatsink for the neodymium motor. The cone assembly consists of a lightweight Kevlar-coated curvilinear paper cone along with a porous screen-type dust cap intended to decouple the high frequency that emanates at the cone’s center.

Compliance is provided by an “M”-shaped pleated coated cloth surround, making the format similar to a high-efficiency pro sound driver. This was done to make the driver easier to drive with low-watt Class A ampli-fiers (e.g., single-triode tube designs), which is also a favorite among full-range single-driver loudspeaker fans. Its remaining compliance comes from a 4”-diameter flat cloth spider.

The PM220-8’s motor design has all the right bells and whistles (due in part to Turnmire’s transducer consulting work) including an undercut T-pole with a copper cap plus a separate shorting ring. The neodymium ring mag-net motor was finite element analysis (FEA)-designed using a 25.4 mm (1”) diameter voice coil with copper-clad aluminum wire wound on a nonconducting poly-imide former. The motor parts, the T-yoke, and the front

Figure 18: Dayton Audio PM220-8 computer box simulations (black solid = sealed at 2.83 V; blue dash = vented at 2.83 V; black solid = sealed at 20 V; blue dash = vented at 21 V)

10 Hz 20 50 100 200 500 1K 2K 5K 10K 20K

dBSPL

70

75

80

85

90

95

100

105

110

115

120

SPL vs Freq

Figure 19: Group delay curves for the 2.83 V curves in Figure 18

10 Hz 20 50 100 200 500 1K 2K 5K 10K 20K

Sec

0

5m

10m

15m

20m

Time vs Freq

plate are coated with a black heat-emissive coating for improved cooling. No other vents (e.g., pole or peripheral back plate vents) were used. Last, the voice coil is ter-minated to a pair of satin-nickel color-coated push termi-nals. Cosmetically speaking, this is good-looking driver.

I began the PM220-8’s analysis using the LinearX LMS analyzer and VIBox to create both voltage and admittance (current) curves with the driver clamped to a rigid test fix-ture in free air at 0.3, 1, 3, 6, and 10 V. The 10-V curves were discarded as they were too nonlinear for LEAP 5 to achieve a good curve fit.

As has become the protocol for Test Bench testing, I no longer use a single added-mass measurement. Instead, I use the physically measured Mmd data (9.45 g for the PM220-8). Next, I post-processed the eight 550-point stepped sine wave sweeps for each PM220-8 sample and divided the voltage curves by the current curves (admit-tance) to derive impedance curves. I used the LMS cal-culation method to add the phase. I imported the data along with the accompanying voltage curves to the LEAP 5 Enclosure Shop software. Because the majority of OEM manufacturers generate their T-S data using either the standard model or the LEAP 4 TSL model, I also used 1 V free-air curves to create a LEAP 4 TSL parameter set.

I used LEAP 5’s transducer parameter derivation menu to select the complete data set, the multiple voltage imped-ance curves for the LTD model (see Figure 17 for the 1 V free-air impedance curve), and the 1 V impedance curve for the TSL model and created the parameters for the


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SEPTEMBER 2013 21

10 Hz 20 50 100 200 500 1K 2K 5K 10K 20K

M

1m

2m

3m

4m

5m

6m

7m

8m

9m

10m

Excursion vs Freq

Figure 20: Cone excursion curves for the 20 V/21 V curves in Figure 18

Figure 21: Klippel analyzer Bl (X) curve for the Dayton Audio PM220-8

Figure 22: Klippel analyzer Bl symmetry range curve for the Dayton Audio PM220-8

Figure 23: Klippel analyzer mechanical stiffness of sus-pension KMS (X) curve for the Dayton Audio PM220-8

Figure 24: Klippel analyzer KMS symmetry range curve for the Dayton Audio PM220-8

Figure 25: Klippel analyzer L(X) curve for the Dayton Audio PM220-8

Figure 26: Dayton Audio PM220-8 on-axis frequency response

300 Hz 500 1K 2K 5K 10K 20K 40K

dBSPL

50

55

60

65

70

75

80

85

90

95

100

105

110

SPL vs Freq

300 Hz 500 1K 2K 5K 10K 20K 40K

dBSPL

50

55

60

65

70

75

80

85

90

95

100

105

110

SPL vs Freq

Figure 27: Dayton Audio PM220-8 on- and off-axis frequency response (black solid = 0°, blue dot = 15°, green dash = 30°, purple dash/dot=45°)


22 VOICE COIL

computer box simulations. Table 2 compares the LEAP 5 LTD data, TSL data, and the factory parameters for both of Dayton Audio PM220-8 samples.

The PM220-8’s LEAP parameter calculation results were similar to the factory’s published data. I followed my usual protocol and used the LEAP LTD parameters to set up the computer enclosure simulations for Sample 1. I pro-grammed two computer box simulations into LEAP 5, one sealed box with a 0.84-ft3 volume (50% fill material) and a QB3 vented enclosure with a 1.3-ft3 volume tuned to 48 Hz, simulated with 15% fiberglass damping material.

Figure 18 displays the PM220-8’s results in the two enclosures at 2.83 V and at a voltage level sufficiently high enough to increase 5.3-mm cone excursion (XMAX + 15%). This produced a 86.7-Hz F3 frequency (F6 = 66.6 Hz) for the sealed box enclosure and –3 dB = 59.4 Hz (F6 = 47.8 Hz) for the EBS-vented simulation. Increasing the voltage input to the simulations until it reached the maximum linear cone excursion resulted in 110 dB at 20 V for the closed-enclosure simulation and 112 dB at the 21-V input level for the larger vented box. Figure 19 and Figure 20 show the 2.83 V group delay curves and the 20 V/21 V excursion curves.

Turnmire performed the Klippel analysis for the Dayton 8” full-range, which produced the Bl(X), KMS(X), and Bl and KMS symmetry range plots shown in Figures 21–24. The PM220-8’s Bl(X) curve is nicely symmetrical, with a small amount of offset (see Figure 21). The Bl symmetry plot shows a trivial 0.27-mm coil-out offset at the rest

Figure 29: Dayton Audio PM220-8 SoundCheck distortion plots

Figure 28: Dayton Audio PM220-8 woofer two-sample SPL comparison

300 Hz 500 1K 2K 5K 10K 20K 40K

dBSPL

50

55

60

65

70

75

80

85

90

95

100

105

110

SPL vs Freq

Figure 30: Dayton Audio PM220-8 woofer CSD waterfall plot

Figure 31: Dayton Audio PM220-8 woofer Wigner-Ville plot

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Add to that an available design team that includes some of the best transducers engineers, industrial designers and marketing experts I know of in the industry and you have a winning combination that would cost well over $750,000 a year to keep in house.



SEPTEMBER 2013 23

position increasing to a likewise trivial 0.54-mm coil-out offset at the physical XMAX position that stays constant throughout the driver’s remaining operating range (see Figure 22).

Figure 23 and Figure 24 show the PM220-8’s KMS(X) and KMS symmetry range curves. The KMS(X) curve is not so symmetrical in both directions and has an obvious offset. The KMS symmetry range plot shows a 1.7-mm coil-out offset at rest staying more or less constant out to the physical XMAX where it decreases slightly to 1.6 mm. This behavior is typical of M-shaped cloth surrounds, and really not much of an issue. This type of displacement is not audible, and should not be considered a problem for this driver. The PM220-8’s displacement-limiting numbers, calculated by the Klippel analyzer, were XBl at 82% (Bl = 3.3 mm) and for a crossover at 75%, the CMS minimum was 2 mm, which means the PM220-8’s compliance is the most limiting factor for the prescribed distortion level of 10%.

Figure 25 shows the PM220-8’s inductance curves L(X). Inductance will typically increase in the rear direction from the zero rest position as the voice coil covers more pole area. However, with a copper cap and aluminum shorting ring installed in the PM220-8, the inductance swing for this driver is a really low 0.023 mH, which is excellent performance.

Next, I mounted the PM220-8 in an enclosure that had a 8” × 15” baffle filled with damping material (foam). Then I used the LinearX LMS analyzer set to a 100-point gated sine wave sweep to measure the device under test (DUT) on- and off-axis from a 300-Hz-to-40-kHz frequency response at 2.83 V/1 m. Figure 26 shows the PM220-8’s on-axis response, indicating a smoothly (±2 to 2.5 dB) rising response to about 10 kHz. Figure 27 shows the on- and off-axis frequency response at 0°, 15°, 30°, and 45°, which is typical for an 8” woofer. Even though this is a “wideband” device, it still has the directivity of any other 8” piston, so crossover frequencies above 2 kHz will degrade a system’s power response. Figure 28 shows the two-sample SPL comparisons for the 8” Dayton driver, with a close match throughout the operating range.

For the PM220-8’s remaining tests, I used the Listen SoundCheck AmpConnect analyzer and SCM microphone to measure distortion and generate time-frequency plots. For the distortion measurement, I mounted the 8” full-range driver rigidly in free air and used a pink noise stimulus to set the SPL to 94 dB at 1 m (1.7 V). Then I used the Listen microphone placed 10 cm from the driver to measure the distortion. This produced the distortion curves shown in Figure 29. 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. For more information, visit www.daytonaudio.com.

The DE980TN-8The last driver I examined this month was the

DE980TN-8 from B&C Speakers, an Italian pro sound

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100.00 mm

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Meet the spec. IEC651 Type 1.�Capsule compare with B&K type 4190. �Application : Suitable for sound level �meter, transport-noise measurement, architectural acoustics, electro-acoustics etc.Dim : 12.7x 90 mm�

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K2

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27

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0°

60

° 90

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12

0°

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18

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Preamplifier

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PHM918Dim: 12.7(mic head) x 145 mm(L)

PHM9193Dim: 8(mic head) x 141.5 mm(L)

PHM9196Dim: 19 x 144.8 mm

PHM919 Dim: 10(mic head) x 145 mm(L)

AVLM1Dim: 7(mic head) x 95 mm(L)

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AVLM2Dim: 13.2 x 50 mm(L)

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What will you find in Voice Coil? • The latest in loudspeaker

technology, components and services—from drivers to cones, to test and measurement software, and hardware

• A valuable, comprehensive source of

industry suppliers • Monthly chronicles of industry news and

manufacturers’ insight

• Spotlight articles on new technologies

• “Acoustic Patents” by James Croft

• “Test Bench” and “Industry Watch” by Vance Dickason

Staff includes Vance Dickason and James Croft

With contributions from Wolfgang Klippel, Steve Temme, Charlie Hughes, Mike Klasco, Steve Tatarunis, Dr. Richard Honeycutt, and Jan Didden

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volume 27, issue 11 september 2013 - dayton audio voice coil review... · volume 27, issue 11...

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