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Old 24th November 2010, 03:56 PM   #1
MCPete is offline MCPete  United States
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Default woofer with high Qms/Qes

Does anyone know of a currently-sold woofer with 0.3 > Qes > 0.2 and Qms about 30 times Qes? I need this type of woofer to test a bass extending network.

I've had some success with Pioneer DVC 8" B20FU20-52D with Qes =0.23 and Qms= 4.05. My calculations show that a higher Qms/ Qes ratio will improve the amount of extension possible.

The size of the woofer at this point isn't of concern to me, but I would like to limit the unit cost to maybe $60. or less because I'm not absolutely certain that I can achieve success with it.

A woofer that fits the bill that I can't locate is Pioneer 6-1/2" woofer C16LU20-51F. This woofer has Qes = 0.23 and Qms = 7.63, so Qms/ Qes = 33.

I don't think that it would be easy to modify a woofer to obtain a higher Qms.

Any help is appreciated,
Pete
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Old 24th November 2010, 07:27 PM   #2
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Doesn't adding extra mass increase Qms??

I have added extra mass to lower Fs, at the expense of lower SPL so need to increase the number of woofers
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Old 24th November 2010, 10:56 PM   #3
MCPete is offline MCPete  United States
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Added mass increases Qes as well as Qms to the same degree. That is, adding mass doesn't change Qms/Qes. Ron E and I think others have posted replies here explaining this.

-Pete
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Old 25th November 2010, 04:36 AM   #4
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Quote:
Originally Posted by MCPete View Post
Added mass increases Qes as well as Qms to the same degree. That is, adding mass doesn't change Qms/Qes. Ron E and I think others have posted replies here explaining this.

-Pete
Can't say I agree with this. I seem to remember reading more than one bench test of this experiment (adding mass and taking measurements) and the Qms is the most affected parameter , IIRC .

The selection is slim with a $60 price limit.

MCM Audio Select 8'' High Excursion Woofer - 120W RMS 4ohm | 55-2421 (552421) | MCM Audio Select


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Old 25th November 2010, 08:33 PM   #5
MCPete is offline MCPete  United States
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That MCM55-2421 looks to be very similar if not identical to the Tang Band W8-740P. I bought and tested the Tang Band and was disappointed to find maximum impedance at free air resonance Fs much lower than it should be. That is,

Zmax = (Qms*Re/Qes) + Re.

If you want to see what Ron E had to say about adding mass, look at the thread entitled "altering T/S parameters?" at diyaudio.com.

Thanks,
Pete
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