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Old 29th February 2012, 09:48 PM   #1
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Default Convert car sub enclosure into HT subwoofer?

Hi,

total noob here. I have a question:

So I have a dual 12" sealed car enclosure with Infinity Perfect VQ (variable Q) woofers. Can I somehow convert it to use in my man cave as a subwoofer in my HT set-up? The enclosure is approx. 1.25 cu. ft. per woofer. I may be able to get a couple of ports in there (if required, as it seems most HT subwoofer enclosures are ported) and I can play with the Q of the subs to get (close to) the desired response I hope. Question is, what is the desired tuning frequency of such a set-up? Also, where can I get an inexpensive amp and how much power will it need to have? The subs are 4 ohm each.

Thanks!
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Old 1st March 2012, 12:47 AM   #2
18Hurts is offline 18Hurts  United States
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I looked it up

The driver has a Fs of 22 Hz, Xmax of 16.75mm, Qts of .47 and a Vas of 96 liters (3.4 cubic feet)

I'd say it would make a good HT sub but you'll need to get it out of the tiny sealed box and build a much larger box if you tune it low for HT. You can't use the box in the home since it will roll off very quickly since the box is too small for low tuning. The little boxes work fine in cars since you have massive cabin gain in a vehicle--you don't have that in a room.

First, figure out how big of a box you can stand, how low do you want to go (20Hz tuning will be a very large enclosure) and what output requirements you desire.
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Old 1st March 2012, 11:55 AM   #3
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by kaigoss69 View Post
Hi,

total noob here. I have a question:

So I have a dual 12" sealed car enclosure with Infinity Perfect VQ (variable Q) woofers. Can I somehow convert it to use in my man cave as a subwoofer in my HT set-up? The enclosure is approx. 1.25 cu. ft. per woofer. I may be able to get a couple of ports in there (if required, as it seems most HT subwoofer enclosures are ported) and I can play with the Q of the subs to get (close to) the desired response I hope. Question is, what is the desired tuning frequency of such a set-up? Also, where can I get an inexpensive amp and how much power will it need to have? The subs are 4 ohm each.

Thanks!
Hi,

Here's two examples of sub's that is a challenge to fold:

b


PS: Note:The TS data for BL is calculated by HR relying on that the fundamental TS is correct.
Attached Images
File Type: jpg Infinity12DVQ_T-TQWT.JPG (483.1 KB, 128 views)
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Old 2nd March 2012, 11:50 PM   #4
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Wow, great info guys, thank you!

I am not sure how to interpret those graphs but I think it is clear that I probably would need a pretty large enclosure. At this time, I am not ready to build one...

However, my man-cave has the option to install subs free-air into the walls. What do you guys think about that idea? 2 12" subs IB with the high-Q inserts should work fairly well. Assuming that is a good path forward, what kind of amp do I need? - I currently have a pretty basic 5.1 HT set-up with Infinity P362 fronts, P252 center, and P162 rears. Receiver is a Denon AVR-987. I'm just looking for a little extra bump in the low end, nothing crazy. Since I already have the subs, I might as well use them. Would it make sense to wire two of them to 8 ohm and use one amp?
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Old 3rd March 2012, 04:10 PM   #5
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I'm in the same situation as the op. Two 12's, 4ohm per sub in 2 small enclosures that I'd like to use for my HT. (currently have a polk 50w powered 8") For an amp I was thinking NU3000DSP. Definitely too much power for now but lots of headroom and lots of options for the future when I build/buy a better 15" sub(s) for my HT, plus the DSP helps.
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Old 3rd March 2012, 08:27 PM   #6
bjorno is offline bjorno  Sweden
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Thumbs up IB ok?

[QUOTE=kaigoss69;2930979]
Quote:
..However, my man-cave has the option to install subs free-air into the walls. What do you guys think about that idea? 2 12" subs IB with the high-Q inserts should work fairly well..
1.25 cu.ft. to IB ? Thats a giant leap.. Unless you are restricting the free air volume once more,have look at this:

Quote:
Assuming that is a good path forward, what kind of amp do I need?
Who knows what you need but a simple plate amp >150W is a first guesstimate.

b
Attached Images
File Type: jpg Infinity12DVQ_IB-at-volumes-above ~283L.JPG (191.9 KB, 66 views)
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Old 3rd March 2012, 11:49 PM   #7
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[QUOTE=bjorno;2932032]
Quote:
Originally Posted by kaigoss69 View Post

1.25 cu.ft. to IB ? Thats a giant leap.. Unless you are restricting the free air volume once more,have look at this:



Who knows what you need but a simple plate amp >150W is a first guesstimate.

b
Thanks bjorno, but what does all that mean? If I install 2 subs IB, will it be a good set-up, compared to say a normal HT ported enclosure subwoofer? What are the pros and cons going IB vs building the optimum enclosure?

Thanks!
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Old 4th March 2012, 02:53 PM   #8
bjorno is offline bjorno  Sweden
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Quote:
..If I install 2 subs IB, will it be a good set-up, compared to say a normal HT ported enclosure subwoofer? What are the pros and cons going IB vs building the optimum enclosure?..
Hi,

It depends on the IB enclosure/space whether IB is better than the optimal box that for this driver when programmed with 'high Qts'.

In the opt. Box there is still excursion control off the cone at and below driver fs but if in a larger volume the excursion will go sky high and a >= 12 dB HPF at fs is always necessary.

Look at the submitted picture.

Any IB volume should IMO be a temperature stable one and closed with pressure equalizing only to the listening room.

Further a closed box volume acts linearizing on the driver suspension especially on a Car woofer like this that I believe is not that linear at high excursions.

So expect lower distortion from a closed box than from an IB.

IMO if the system resonance is below 30 Hz: A system Q can be chosen above opt. Q as any room except an acoustically treated one, of course, will often have a FR modifying effect far more wrecking the response an the system Q too.

b
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File Type: gif Car-sub-into-HT-IB.GIF (57.9 KB, 44 views)
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