How bad is it to have a high qtc for a 12" woofer? - diyAudio
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Old 16th April 2012, 06:47 AM   #1
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Default How bad is it to have a high qtc for a 12" woofer?

Using various speaker box designers, I'm coming up with very large Vb when using a qtc of 0.707. How bad would it be to have a higher qtc (0.8 or 0.85) for this woofer:

12" Square Frame Paper Cone Woofer White 290-914

How much will sound quality suffer?
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Old 16th April 2012, 01:05 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

With a Qts of 0.69 a box sim will suggest silly sized boxes for Qbox = 0.71.

You have to accept a higher Q alignment, and the driver is intended to
be used in boxes with a Qbox >1. Qbox =1 is 5.5cuft which is similar
to Vas and going bigger won't help that much, you need 10 cuft to
get to Q=0.9, and 20cuft to get to Q=0.8.

You should accept that the driver works best an 3 to 4 cuft box with a
box Q of 1.1 to 1.2, probablty intended to be about 2cuft. If you think
Q=1.4 is bad, try some of the other cheap PE 12" in a 2 cuft box ......
One comes out with a Qbox near 3 ....

The Dayton Audio DC300-8 12" works well in a 2 to 3 cuft
sealed box, and well in 3 to 4 cuft boxes tuned low at 25Hz.

rgds, sreten.
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Last edited by sreten; 16th April 2012 at 01:20 PM.
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Old 16th April 2012, 01:08 PM   #3
AndrewT is online now AndrewT  Scotland
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Or no box at all?
Maybe this driver is intended for infinite baffle, i.e. a hole in the wall between two rooms that are isolated from each other.
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Old 16th April 2012, 02:39 PM   #4
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Perhaps the designer had the Linkwitz Transform in mind.

I would not be afraid of Q slightly over 1. Room modes will probably do a lot more harm.


For many years I have listened with pleasure to AR16's , they worked very well in our family room 8x4x2.7 meter.
Bass was quite qood...

AR16 Qtc=1,15 @55Hz according to AR specification.
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Old 16th April 2012, 04:17 PM   #5
GM is offline GM  United States
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Quote:
Originally Posted by Fusion916 View Post
How bad would it be to have a higher qtc (0.8 or 0.85) for this woofer:
0.85 Qtc calculates a ~0.43 dB peaking around 70 Hz in well stuffed ~115.44 L, so plenty good enough.

GM
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Old 16th April 2012, 04:48 PM   #6
stoc005 is offline stoc005  United States
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"Cult of the Infinitely Baffled"Hear The Bass, Not The Box The definitive online resource for Infinite Baffle subwoofer designEstablished 1999 - Home Read the FAQ there.

Like AndrewT says - An infinite baffle.
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Old 16th April 2012, 05:06 PM   #7
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Quote:
Originally Posted by GM View Post
0.85 Qtc calculates a ~0.43 dB peaking around 70 Hz in well stuffed ~115.44 L, so plenty good enough.

GM
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Old 16th April 2012, 05:12 PM   #8
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Old 16th April 2012, 06:17 PM   #9
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Well since infinite baffle isn't an option, the only option is a high qtc?
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Old 17th April 2012, 02:07 AM   #10
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by AndrewT View Post
Or no box at all?
Maybe this driver is intended for infinite baffle, i.e. a hole in the
wall between two rooms that are isolated from each other.
Hi,

No. Most drivers of this type are intended for boxes with higher Q
than 1.0. They also generally don't have any BSC so it sounds far
less worse than you might think, used in many commercial speakers.

rgds, sreten.
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