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Old 7th January 2010, 01:20 AM   #1
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Default Budget IB for garage

I want to add some bass to my garage speakers, and I thought that IB would be the ideal way to do it. I don't want a box sitting in the garage, and I have plenty of space up above (attic). I looked at what Parts Express has to offer, and came up with these 2 candidates due to the low prices (<$25).

Fs: 24 Hz
SPL: 93/W
Vas: 14.98 cu ft
Qts: 0.34
Xmax: 4 mm
Parts-Express.com:*JAMO 20392 15" Paper Cone Woofer | JAMO 20392 15" Woofer Treated Paper Cone driver speaker bass

Fs: 27 Hz
SPL: 92/W
Vas: 17.50 cu ft
Qts: 0.85
Xmax: 3 mm
Parts-Express.com:*JAMO 20388 15" Paper Cone Woofer | JAMO 20388 15" Woofer Treated Paper Cone driver speaker bass

I've come across sites saying to look for low Qts, others to aim for a .7, and even others for a high Qts. I have never done or heard an IB setup, so I'm not quite sure what to look for in selecting drivers. I realize that Xmax is important, but being a garage setup on a budget, the price for these drivers is right. This will be mated to two speakers with 8 inch woofers; how many of the IB drivers would be suitable? Are there any better drivers within the price range?

Note: signal processing will be available through a creative sound card and KX drivers (EQ, delay, XO, etc).
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Old 7th January 2010, 11:35 AM   #2
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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
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Old 7th January 2010, 02:25 PM   #3
doug20 is offline doug20  United States
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Those drivers have crap Xmax and you will need 16 or 32 of them

Displacement is king!

Definitely go to the IB cult site linked above and talk to ThomasW. He is the IB Guru.

I have an IB array in my family room with 4 18" from ficar audio....the best displacement/$$ choice out there.

What is your budget?
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Old 7th January 2010, 03:43 PM   #4
adason is offline adason  United States
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Hi xplod1236,

that second jamo 15" woofers is good value, I have six of them in various boxes, they work well in closed box, I never tried IB

I never tried the first woofer, just seems to have magnet too small
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Old 7th January 2010, 04:15 PM   #5
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A great deal depends on how loud you want it. If you are talking 85db or so one or 2 of those drivers would probably be fine. But if you want it realy loud you will most
likely run out of xmax.
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Old 9th January 2010, 03:21 PM   #6
pjanda1 is offline pjanda1  United States
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I mentioned those PE speakers in a different thread, and just FYI, it looks as if the specs and pics could be swapped around. If you are thinking of buying them, you may want to contact PE and be sure of what you are getting.

You might consider these custom Eminence woofers listed in the classifieds. They offer a good deal more displacement for only a few more bucks.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
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Old 8th February 2010, 02:50 AM   #7
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Quote:
Originally Posted by adason View Post
Hi xplod1236,

that second jamo 15" woofers is good value, I have six of them in various boxes, they work well in closed box, I never tried IB

I never tried the first woofer, just seems to have magnet too small
I have four of the Jamo 20388's. As it happens I did temporarily rig one of them up as an IB woofer just to see what it would do. My den/man cave has the crawl space access in the closet, so I pulled the hatch and cut a piece of particle board to fit the hole. The Jamo was mounted in it magnet up to make the wiring easy. The attached FR done with HolmImpulse, and a Dayton measurement mic just off the back side of the woofer. Smoothing is 1/3 octave.

I don't know what your frequency or SPL target for the garage IB would be. Most folks doing IB's seem to be into house-shaking home theater effects at high volumes. The Jamos wouldn't go low enough for them. They do go deep enough for most music IMO. If your 8 inchers already go halfway low you might not get much benefit from the Jamos.

I don't trust the published Fs or Qt specs, which say they should play roughly flat to 30 instead of 40 Hz in IB, but WinISD says two of them should able to make 100+ dB on 4 watts and not run out of excursion at any frequency. If you limit the signal below 40, they'd play much louder. Or get four of them, for $90 you could have some cheap fun, wake the neighborhood and probably learn quite a bit about what to do the second time. i haven't found anything close for the price.

I do believe the efficiency spec for the Jamos, two of them in parallel match the efficiency of a Fostex FE1661E just as MJK's worksheet said they should. They will get quite loud powered by a five watt single ended EL34 amp. They just don't go quite as deep as the sims say they should.

If you want serious IB bass, a single AE IB15 will also hit 102 dB, but *should be* pretty flat to close to 20 Hz. It would take six of the Jamos plus some EQ to match the low bass output of the AE, and the driver cost would be about the same. I'm tempted to pick up one of those for the den. Or four for the living room HT. Might be overkill for the garage. Probably overkill for my house, too.

Bill
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File Type: jpg Jamo 20388 IB nearfield.JPG (76.9 KB, 106 views)
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Old 8th February 2010, 02:56 AM   #8
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Quote:
Originally Posted by pjanda1 View Post
I mentioned those PE speakers in a different thread, and just FYI, it looks as if the specs and pics could be swapped around. If you are thinking of buying them, you may want to contact PE and be sure of what you are getting.

You might consider these custom Eminence woofers listed in the classifieds. They offer a good deal more displacement for only a few more bucks.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
The 20388's (high-Q version) are as pictured. I don't know how the small magnet version could have as low a Q as specified, unless it's a neo magnet which I would doubt at that price.

Bill
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Old 8th February 2010, 05:20 AM   #9
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Sorry guys, I ended up picking up a 12 inch Audiosource powered sub for $25. The IB would end up costing more than I'd like to spend, and on top of that, I don't have the time to put it all together. I will definitely keep the IB in mind for my future sub projects.
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