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2015
FA4740 –Transducer Theory
SPEAKER DESIGN
ZACH STRAUSS
1
Table of Contents Functional Description .................................................................................................................................. 4
Speaker Usage........................................................................................................................................... 4
Speaker Environment ................................................................................................................................ 4
Speaker Purpose ........................................................................................................................................ 4
Exterior Design .......................................................................................................................................... 4
SPL Output ................................................................................................................................................. 4
Sound Quality ............................................................................................................................................ 4
Design Priorities ........................................................................................................................................ 5
Design Goals .................................................................................................................................................. 6
Size ............................................................................................................................................................ 6
Weight ................................................................................................................................................... 6
Portability .............................................................................................................................................. 6
SPL ............................................................................................................................................................. 6
Personal Needs ..................................................................................................................................... 6
Driver Sensitivity ................................................................................................................................... 7
Bandwidth Needs ...................................................................................................................................... 7
Driver Sizing .............................................................................................................................................. 7
Directionality ............................................................................................................................................. 8
Driver Analysis............................................................................................................................................... 9
Tweeters .................................................................................................................................................... 9
1: Seas Prestige 29TFF/W ...................................................................................................................... 9
2: Seas Prestige 22TAF/G .................................................................................................................... 10
3: SB Acoustics SB26STAC-C000-4 ....................................................................................................... 11
4: Dayton Audio RS28F-4 .................................................................................................................... 12
5: Eton 25SD-1 ..................................................................................................................................... 13
Final Analysis ....................................................................................................................................... 14
Woofers ................................................................................................................................................... 15
1: Tymphany Peerless HDS-P830869 .................................................................................................. 15
2: Dayton Audio Rs225P-8 .................................................................................................................. 16
3: ScanSpeak ....................................................................................................................................... 17
Testing and Tuning ...................................................................................................................................... 18
Final Testing ............................................................................................................................................ 19
2
Overall Response ................................................................................................................................ 19
Harmonic Distortion ............................................................................................................................ 19
Off-axis response ................................................................................................................................ 20
Minimum Phase response................................................................................................................... 23
Impulse Response ............................................................................................................................... 24
Waterfall Plot ...................................................................................................................................... 24
Bibliography ................................................................................................................................................ 26
3
Figure 1- Design Priorities ............................................................................................................................. 5
Figure 2- Table of selected listening levels ................................................................................................... 6
Figure 3- Low Frequency Bandwidth Needs ................................................................................................. 7
Figure 4- SEAS 29TFF/W Frequency Response ............................................................................................. 9
Figure 5- SEAS 22TAF/G Frequency Response ............................................................................................ 10
Figure 6- SB26STAC-C000-4 Frequency Response ...................................................................................... 11
Figure 7- RS28F-4 Frequency Response ...................................................................................................... 12
Figure 8- Eton 25SD-1 Frequency and Impedance Charts .......................................................................... 13
Figure 9- Tweeter Analysis Table ................................................................................................................ 14
Figure 10 - HDS-P830869 Frequency Response .......................................................................................... 15
Figure 11 - HDS-P830869 in 1.8 cu. ft box tuned to 40Hz ........................................................................... 15
Figure 12 - RS2258-P Frequency Response ................................................................................................. 16
Figure 13 - RS2258-P in 1.5 cu. ft box tuned to 40Hz ................................................................................. 16
Figure 14 - Scanspeak Frequency Response ............................................................................................... 17
Figure 15- Scanspeak in 1.9 cu. ft box tuned to 30Hz ................................................................................. 17
Figure 16- Initial Driver Performance ......................................................................................................... 18
Figure 17 - Tuning Revisions ....................................................................................................................... 18
Figure 18 - System Frequency Response .................................................................................................... 19
Figure 19 - System Harmonic Distortion ..................................................................................................... 19
Figure 20 - System 0-60* Horiz. Off-axis Response .................................................................................... 20
Figure 21 - Tweeter 0-60* Horiz. Off-axis Response ................................................................................... 20
Figure 22 - Woofer 0-60* Horiz. Off-axis Response .................................................................................... 21
Figure 23 - System 0-60* Vert. Off-axis Response ...................................................................................... 21
Figure 24 - Tweeter 0-60* Vert. Off-axis Response .................................................................................... 22
Figure 25 - Woofer 0-60* Vert. Off-axis Response ..................................................................................... 22
Figure 26 - Tweeter Minimum Phase .......................................................................................................... 23
Figure 27 - Woofer Minimum Phase ........................................................................................................... 23
Figure 28 - System Impulse Response......................................................................................................... 24
Figure 29 - System Waterfall Plot ............................................................................................................... 24
4
Functional Description
Speaker Usage The speaker will be used for multiple purposes, and will not be designed to fill a specific niche. It
should be useable for mixing and general listening in varied environments, as well as being able to be
used for tracking.
Speaker Environment The speaker will be used in traditional interior environments. Rooms will have low amounts of
background noise, with reverberation ranging from that of an average home environment to a treated
studio space. The speakers will be used on stands, as components of a stereo system or as the front
mains in a surround system.
Speaker Purpose The speaker may be used for both tracking and mixing, although mixing use will be a larger goal.
The speakers will fit the needs of David Moulton’s concept of “listening-back,” they will reproduce the
given signal to the fullest extent of fidelity1. Using the range rule for listening forward, the speaker may
be used as a reference for a high-end consumer speaker or prosumer monitor2. The speaker design will
be aimed for high fidelity playback, although they will also be used for pleasure listening.
Exterior Design The speaker will be built from wood products, and must have an attractive exterior. It may be
rectangular or trapezoidal in shape, with uncovered drivers. It must be of a size and weight that that it
can be transported by one person, and fit comfortably in an average sedan’s trunk.
SPL Output The speaker must be able to be used in a home environment at moderately low listening levels,
while still having the ability to track and mix according to K-System monitoring guidelines3. It will not
distort audibly at the highest peaks of K-System usage.
Sound Quality As defined by the AES listening standards4, the speaker will be of uniform response over its
frequency range. Stereo image shall be wide and specific, with accurate reproduction of material
ambiance. Frequency extension may be dependent on listening volume, and the speaker shall be clear at
low levels. The speaker will be able to faithfully reproduce transient material without distorting. The
speaker will not be overly fatiguing, and its response will be less effected by listener movement in the
horizontal plane than in the vertical.
1 (Moulton 2000, 313) 2 (Moulton 2000, 313-314) 3 (Digital Domain n.d.) 4 (Audio Engineering Society, Inc. 2007)
5
Design Priorities Using the system suggested by Murphy, the speaker will be designed to maximize useable
bandwidth, with SPL as a secondary goal5.
Figure 1- Design Priorities
5 (Murphy 1998, 56)
Range
Size
SPL
6
Design Goals
Size The speaker will be of a size similar to two speakers that I already own, the Infinity RS 6/B
(22”x14”x10”)6, and the JBL 8330 (20”x19”x10”)7. The size will not exceed the largest height or width of
those references, but may be slightly deeper. The maximum size for the speaker will therefore be 22”W
x 19”H x 12” D.
Weight The speaker will be light enough to be handled and moved by one person, using the JBL83308 as
a reference, for a weight of 30-40lbs.
Portability The speaker will be able to be moved as needed, with an exterior built to handle handling. It will
be able to fit comfortably in the trunk of a 2nd generation Dodge Stratus Coupe (16.3 ft3)9.
SPL The speaker will be able to be used for K-20 monitoring, therefore it must be capable of
producing 103dB SPL without distorting.
Personal Needs I explored my personal listening habits to find my needs for output levels. I found that on
average, I prefer much lower listening levels, and that my goal of K-20 readiness will be the defining
factor in my design.
Figure 2- Table of selected listening levels
6 (Infinity Systems, Inc 1998) 7 (JBL Professional 1996) 8 (JBL Professional 1996) 9 (DaimlerChrysler 2005)
Night Listening
Midday
Monitoring
Jamming
40
45
50
55
60
65
70
75
80
dB
Listening Levels
7
Driver Sensitivity The speaker will be driven by a MiniDSP PWR-ICE125WD plate amp, providing 125W10 (21.5dBw)
to each driver. To reach the needed 103dB SPL, drivers must be of at least 81.5dB/W/m sensitivity.
Bandwidth Needs The speaker will be controlled by a MiniDSP 2x4 DSP platform. The 2x4 operates at 48kHz11,
which will limit the speaker to the Nyquist frequency of 24kHz at maximum. To aid in design and product
sourcing, the speaker will have a maximum output frequency of no less than 20kHz.
To find my needed f3 for normal listening material, I used a speaker system with a bandwidth of
approx. 30-20,000Hz. On that system, I played back music through a steep HP filter and charted the
points at which the lack of low end signal was noticeable and unacceptable.
Figure 3- Low Frequency Bandwidth Needs
From this experiment I found that in my normal listening the f3 of the speaker needs to be no
more than 60Hz. To allow for use on film, gaming, or other program material that contains signal below
that point, the design f3 of the speaker will be 40Hz.
Driver Sizing My original design was for a sealed 3-way system built around a 10” woofer, however upon
software modeling woofers I found that an 8” driver in a vented box could meet and exceed my
bandwidth and SPL goals while still retaining acceptable amounts of group delay and other distortions.
The speaker will therefore consist of an 8” woofer and a dome tweeter in a 2way configuration. The
drivers will be placed closely together to minimize phase interactions at the crossover point.
10 (MiniDSP n.d.) 11 (MiniDSP n.d.)
0
1
2
3
4
5
6
0 50 100 150 200 250 300 350
Son
g
HP Freq. (Hz)
18 dB/Octave Filter
Noticable
Acceptable
Unacceptable
8
Directionality The speaker will most often be employed in single-user situations, and will therefore the design
will be most concerned with on-axis performance. The off-axis abilities of the speaker are to be
considered, but are of much lesser importance. To allow use in multi-listener and differing acoustical
environments the speaker will radiate equally in the vertical and horizontal planes.
9
Driver Analysis
Tweeters
1: Seas Prestige 29TFF/W12 The 29TFF/W is a 1” fabric dome tweeter, with a useable bandwidth of 2200-25,000Hz. I am a
fan of its high-end extension, however it would be somewhat limited by its performance below 2500Hz.
Figure 4- SEAS 29TFF/W Frequency Response
12 (SEAS n.d.)
10
2: Seas Prestige 22TAF/G13 The 22TAF/G is a 1” metal dome tweeter, with a useable bandwidth of 2500-30,000Hz. While
more efficient and able to extend higher than the 29TFF/W, it shares the issue of a higher low limit. As
the speaker is hard limited to 24kHz by the MiniDSP 2x4, the ability of either driver to extend to 20kHz+
is not a significant benefit.
Figure 5- SEAS 22TAF/G Frequency Response
13 (SEAS n.d.)
11
3: SB Acoustics SB26STAC-C000-414 The SB tweeter is also a 1” soft dome, with a useable range of 750-30,000Hz. I really like this
driver for its low fs and flat response.
Figure 6- SB26STAC-C000-4 Frequency Response
14 (SB Acoustics n.d.)
12
4: Dayton Audio RS28F-415 The RS28-F is a 1-1/8” silk dome tweeter with a useable range of 700-20,000Hz. This driver,
while able to work low enough for easy crossover design, has much too unstable of a response to be
used in the speaker.
Figure 7- RS28F-4 Frequency Response
15 (Dayton Audio n.d.)
13
5: Eton 25SD-116 The 25SD-1 is a 1” soft dome tweeter with a range of 1000-30,000Hz. I like it for its flat
response, however its pricing leaves something to be desired.
Figure 8- Eton 25SD-1 Frequency and Impedance Charts
16 (Madisound n.d.)
14
Final Analysis
Driver 29TFF/W 22TAF/G SB26STAC-C000-4 RS28F-4 25SD-1
Price ($) 54.50 43.60 43.85 54.75 87.15
Lowest Frequency (Hz) 2,200 2,500 1,000 1,200 1,000
Max Frequency (Hz) 25,000 20,000 30,000 20,000 20,000
Response (dB) ±1.5 ±1.5 ±1.5 ±3 ±2
Sensitivity (dB/W/m) 92 92 91 91 90
Max Power (W) 200 180 120 100 100 Figure 9- Tweeter Analysis Table
For the speaker I will use the SB26STAC-C000-4, for its great price point and ability to be crossed
over lower than most of the other drivers. Its flat response out to 30kHz is a nice bonus, as the driver
will function far beyond the other limits in the processing chain.
15
Woofers
1: Tymphany Peerless HDS-P83086917
Figure 10 - HDS-P830869 Frequency Response
Figure 11 - HDS-P830869 in 1.8 cu. ft box tuned to 40Hz
17 (Tymphany n.d.)
16
2: Dayton Audio Rs225P-8
Figure 12 - RS2258-P Frequency Response
Figure 13 - RS2258-P in 1.5 cu. ft box tuned to 40Hz
17
3: ScanSpeak
Figure 14 - Scanspeak Frequency Response
Figure 15- Scanspeak in 1.9 cu. ft box tuned to 30Hz
18
Testing and Tuning
Figure 16- Initial Driver Performance
For my initial tuning a crossover frequency of 1200Hz was chosen based on the Fs of the tweeter and
the breakup point of the woofer. First measurements showed acceptable results without additional
action taken, and subsequent changes were minor.
Figure 17 - Tuning Revisions
The first changes made was the level matching and time alignment of the drivers, shown by the change
in blue from purple traces in fig. 17. The only other measure taken was the addition of a small boost
centered at 3.2kHz, shown by the green to purple change.
19
Final Testing
Overall Response
Figure 18 - System Frequency Response
Harmonic Distortion
Figure 19 - System Harmonic Distortion
20
Off-axis response
Horizontal
Figure 20 - System 0-60* Horiz. Off-axis Response
Tweeter
Figure 21 - Tweeter 0-60* Horiz. Off-axis Response
21
Woofer
Figure 22 - Woofer 0-60* Horiz. Off-axis Response
Vertical
Figure 23 - System 0-60* Vert. Off-axis Response
22
Tweeter
Figure 24 - Tweeter 0-60* Vert. Off-axis Response
Woofer
Figure 25 - Woofer 0-60* Vert. Off-axis Response
23
Minimum Phase response
Tweeter
Figure 26 - Tweeter Minimum Phase
Woofer
Figure 27 - Woofer Minimum Phase
24
Impulse Response
Figure 28 - System Impulse Response
Waterfall Plot
Figure 29 - System Waterfall Plot
25
26
Bibliography Audio Engineering Society, Inc. 2007. AES recommended practice for professional audio — Subjective
evaluation of loudspeakers. New York.
DaimlerChrysler. 2005. 2005 Dodge Stratus Coupe. Accessed 2 15, 2015.
http://www.dodge.com/pdf/stratus_coupe/complete.pdf.
Dayton Audio. n.d. RS28F-4 Datasheet.
Digital Domain. n.d. "How To Make Better Recordings in the 21st Century - An Integrated Approach ..."
Level Practices (Part 2).
Infinity Systems, Inc. 1998. "RS 6/B." Specifications, Woodbury, New York.
JBL Professional. 1996. "8330 Surround Foreground Music System." Specifications, Northridge,
California.
Madisound. n.d. "Eton 25SD-1, 1" Soft Dome Tweeter." madisound.com. Accessed 2 10, 2015.
https://www.madisoundspeakerstore.com/eton-soft-dome-tweeters/eton-25sd-1-1-soft-dome-
tweeter/.
MiniDSP. n.d. "2x4 Datasheet." MiniDSP.com. Accessed 1 17, 2015.
MiniDSP. n.d. "PWR-ICE125." Product Breif.
Moulton, David. 2000. Total Recording: The Complete Guide to Audio Production and Engineering.
Sherman Oaks, CA: KIQ Productions.
Murphy, John. 1998. Introduction to Loudspeaker Design. Andersonville, Tennessee: True Audio.
SB Acoustics. n.d. SB26STAC-C000-4 Preliminary Data.
SEAS. n.d. 22TAF/G H1283 Datasheet.
SEAS. n.d. 29TFF/W H1318 Datasheet.
