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Old 16th June 2005, 05:55 PM   #1
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Default Need 8" sub - low Qts, low Fs???

For an infinite-baffle type of install.

I believe an ideal IB sub has a low Qts (meaning low Qes really), and a low Fs, and I imagine a low Vas also... in layman's terms, a strong motor yet a low resonant frequency, and a stiff suspension.

And since our goal here is to increase the amount of output that an already installed "ho hum" 8 inch free air sub, one with a good amount of excursion capability too, I assume.

Any suggestions?
Thanks!
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Old 16th June 2005, 08:08 PM   #2
micb is offline micb  United Kingdom
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Check out ImageDynamics ID8's.

I know plenty of people who have used then in IB installs to good result.
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Old 17th June 2005, 03:16 AM   #3
mike.e is offline mike.e  New Zealand
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IB = lots of displacement required.
Qts = Q system in IB meaning ,0.5-1.0 depending on bass 'taste'

Usually people use multiple 15"s with litres of displacement. Multiples of 8"s could do it.
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Old 17th June 2005, 04:05 AM   #4
simon5 is offline simon5  Canada
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Cheap woofer

7 mm Xmax with 27 Hz Fs and a .37 Qts.

http://www.partsexpress.com/pe/showd...number=295-366


A bit more expensive and it's more like a 7 inch woofer.

13 mm Xmax with 30 Hz Fs and a .33 Qts

http://www.adireaudio.com/Home/ExtremisMidwoofers.htm
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Old 17th June 2005, 07:33 AM   #5
micb is offline micb  United Kingdom
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Here are the details on the ID8's.

http://www.imagedynamicsusa.com/tech...type=sub&id=id

http://www.imagedynamicsusa.com/tech...type=sub&id=id

A pair is the minimum, 4 with 1000-1200 WRMS to the set is better if you want more output.
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Old 17th June 2005, 06:42 PM   #6
simon5 is offline simon5  Canada
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^^ He found out better stuff, Image Dynamics is the way to go it seems.
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Old 18th June 2005, 02:29 AM   #7
theNoid is offline theNoid  United States
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Default Re: Need 8" sub - low Qts, low Fs???

Quote:
Originally posted by geolemon
For an infinite-baffle type of install.

I believe an ideal IB sub has a low Qts (meaning low Qes really), and a low Fs, and I imagine a low Vas also... in layman's terms, a strong motor yet a low resonant frequency, and a stiff suspension.

And since our goal here is to increase the amount of output that an already installed "ho hum" 8 inch free air sub, one with a good amount of excursion capability too, I assume.

Any suggestions?
Thanks!
Is this for a car or home may I ask? I am hoping a car since you are considering only 8" drivers. As was mentioned, to achieve any kind of decent SPL levels, there is no replacement for displacement. When it comes to the Qts, I usually like lower to mid values better myself. But have heard plenty of great systems with drivers of high Qts specs as well.

For a neat looking little 8", check out http://www.soundsplinter.com and have a look at their...

Click the image to open in full size.

Noidster
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Old 18th June 2005, 02:40 AM   #8
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For IB you want a mid Q driver because the system Q is the driver's Q as there is no "box" . A low Q drive will be over-damped and won't produce much bass in IB. Why would you want an 8" driver for an IB application anyway and except for under your desk or in a horn, I'd have a hard time calling something with an 8" driver a subwoofer ?
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Old 18th June 2005, 11:47 AM   #9
theNoid is offline theNoid  United States
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Actually I have built several 8" based subwoofers that provided plenty of output into the low 30's and a few that provided useful output into the 20's as well. For an IB system though, unless we are talking about for a car here, I agree, 8" is not the way to go.

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Old 18th June 2005, 04:44 PM   #10
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OK, I'll concede the point, but personally I'd still call them Subwoofer Jr's or bass augmenters.
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