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Old 8th August 2010, 10:57 PM   #1
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Default How big is TOO big?

I've been wanting to build another sub, and purchased this driver a while back, intending to build an infinite baffle design published in audioXpress. Then a construction project at my work had some leftover sonotube, and I'm contemplating something different. The only thing is, it's 36" diameter tube! There are two, each about 30" tall, for about 18 cu. ft., each! I did a little playing around with WinISD, and it seems that an enclosure that big just makes the slope off to the left more gradual.
Is there any point to trying something this big? What about a different driver, maybe something in the 15-18" range that isn't too terribly expensive, that I could play around with?
They were free, so I just wanted to experiment!

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Old 8th August 2010, 11:01 PM   #2
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You can pick up an 18 inch Eminence sigma pro for about 120.

15 inch drivers can be got for considerably less.

I love the bass of the eminence 18 inch.
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Old 8th August 2010, 11:09 PM   #3
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Quote:
Originally Posted by nigelwright7557
You can pick up an 18 inch Eminence sigma pro for about 120.
This one? Looks nice, but it has a higher Fs than the Dayton I have on hand. I'm kinda new to this, and it seems counterintuitive, but doesn't that mean I'll get lower bass out of the twelve?
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Old 8th August 2010, 11:15 PM   #4
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Yes it's too big for that driver. The problem you will run into is a reduction in power handling. You could probably make the tube half the length and not notice any difference.

But a 36 inch diameter tube in your house? Might be a bit difficult to accomodate.
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Old 8th August 2010, 11:15 PM   #5
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Yes the 12 inch will go lower as it has lower Fs and higher Qts.
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Old 8th August 2010, 11:16 PM   #6
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Thats the one.

It is quite cheap for an 18 incher so maybe thats why the Fs is a little higher.

I used one for my disco and get good results.
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Old 8th August 2010, 11:23 PM   #7
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Quote:
Originally Posted by richie00boy
Yes it's too big for that driver. The problem you will run into is a reduction in power handling. You could probably make the tube half the length and not notice any difference
Yea, I thought about that. And 9 cu. ft. is a nice size for a sub, but a big flat disc isn't too appealing.

Quote:
But a 36 inch diameter tube in your house? Might be a bit difficult to accomodate.
Thought about that, too.
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Old 9th August 2010, 03:55 AM   #8
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You could try to do a work up for the internal baffles and turn that big volume into
some type of horn enclosure.... or two
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Old 9th August 2010, 05:21 AM   #9
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Apart from the other good reasons subs might be too big, you may care to avoid half-wave resonances in the pipe. 30 inches top to bottom yields about a 60 inch wavelength, or about 220 Hz. 36 inch diameter implies a 72 inch wavelength, or about 185 Hz. You really want the crossover to leave minimal energy at those frequencies to avoid strange peaks in the low midrange.
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Old 9th August 2010, 05:40 AM   #10
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Or just cross it really low. True sub use.

I already dropped my 2 cents here.
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