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Old 28th January 2010, 08:49 PM   #1
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Location: Dothan ,Al.
Default Open baffle question

Is an infinite baffle sub suitable for an open baffle design?

Specs of driver in question :
Fs (Hz) 16
Qms 6.8
VAS (ltrs) 439
Mms (g) 220
Cms (mm/N) .45
Sd (cm²) 830
Xmax (mm) 18.5
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Old 28th January 2010, 09:31 PM   #2
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Location: SiliconValley
Hi Rightbrained,

Your specs do not include the Qts parameter, but look like the AES IB15.

The IB15 is a very good choice for a dipole woofer that would require minimal crossover dipole compensation. Woofers with a Qts between 0.7 and 0.9 are good candidates to model for a dipole design since their high Q mechanical gain partially compensates for the dipole baffle loss. The low efficiency of 86db/watt is the trade-off for the higher Qts, and runnning two IB15s in parallel is often done to get close 92 db/watt with an amp that can drive 3 ohms.

To some ears, woofers with Qts over 0.9 start to sound "loose" and out of control on fast transients like a kick drum. Some ears like a high'ish Qms and getting most cone control from the Qes electrical parameter. Words like "sticktion" from sticky_friction are sometimes used for low Qms woofers. The IB15 Qms of 6.4 is a good compromise for an open air speaker.

===============

Acoustic Elegance Speakers: IB15 are 8ohm drivers. Running a pair in parallel at 4ohm off a modest pro audio amplifier will easily push these drivers to high levels. They have a full copper sleeve on the pole to lower inductance and distortion. Due to the low inductance they also have very good high frequency extension which could be beneficial in dipole applications. They are hand coated paper cone with a hand coated and sealed foam surround. Here are the parameters:
The IB15 is quite simply the ultimate infinite baffle driver. The IB15 was designed from the ground up to be the most accurate, lowest distortion infinite baffle driver ever made. The high Xmax means these drivers can move some serious amounts of air. The extremely low Fs along with the .707 Qts means there is the greatest possible bass efficiency and lowest possible F3 point without added bass boost needed.

The full copper shorting ring on the pole solves two of the greatest issues causing distortion in loudspeakers that remain not addressed in 99% of drivers available. It both lowers inductance and fixes the flux permanently in the gap. Inductance on the IB15 is as low as many midrange drivers, allowing them to play up high if called upon.



Fs: 16Hz
Qms: 6.8
Vas: 439L
Cms: .45mm/N
Mms: 220g
Rms: 3.239
Xmax: 18.5mm
Xmech: 25mm
Sd: 830sqcm
Vd: 3.07L (p-p)
Qes: .78
Re: 5.5ohm
Le: .33mH
Bl:12.49
Pe: 500W
Qts: .7
1WSPL: 86dB
Attached Images
File Type: png IB15frontproduct.png (36.6 KB, 97 views)
File Type: jpg DipoleBaffle.jpg (94.8 KB, 98 views)
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Old 28th January 2010, 09:36 PM   #3
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Join Date: Aug 2008
Location: Dothan ,Al.
Linesource ,
Thanks for the reply and you are dead on in regards to which driver I inquired about.
I have never built or even heard an open baffle design but I would like to try one.
I seem to have a DIY addiction and its time for another build.
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