Building IB box - Home Theater Forum and Systems -

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post #1 of 18 Old 10-25-07, 06:34 AM
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Building IB box

After studying the greatness of IB subwoofer systems, I am keen to make a set up that i hope will work. In the land of Aussie, these designs are unheard of, so after searching E bay and many other on line shops, i have found a couple of stand alone 350Watt RMS amps, and will fit 2 X 15" subs. Lucky the amps run off the mains and will feed 4 ohms, so i can use a set of car subs. I know this is not optimal, but am on a budget, with projectors etc to come jet. Room is devoted theatre, with mojo ceiling(nearly black) and dark brown walls. I have a pioneer amplifier, 6.1. the walls and ceiling are sound proofed reasonably well. Insulation throughout the whole house's ceiling. The problem i have is can I split the RCA single channel into two so i can run two amps? will i still have enough pre - out voltage? any info or advice appreciated. only running a stand alone 10 inch sub from dick smith right now so i think this would improve it heaps.
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post #2 of 18 Old 10-25-07, 07:51 AM
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Re: Building IB box

peteaimee wrote: View Post
The problem i have is can I split the RCA single channel into two so i can run two amps? will i still have enough pre - out voltage? any info or advice appreciated.
Hi there,

Splitting your preamp level output will cause no trouble. The high input impedance of the amplifiers will cause very little voltage drop, and both will work the same.

You will enjoy your IB -- it'll be a huge improvement over a single 10" sub!

Good luck!

-- Otto
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post #3 of 18 Old 10-25-07, 04:41 PM
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Re: Building IB box

You're probably going to need more than two 15inch drivers for an IB. What is the Xmax?

An IB uses less power than a conventional box - excursion is the limiting factor.

Running a pair of amps would let you run 4 drivers per amp in a series / parallel arrangement.

If those amps are the Jaycar 350W models, bear in mind that the 6dB boost@35hz won't help you get down low. Check your design in WinISD. Sing out if you need a hand.

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post #4 of 18 Old 10-25-07, 08:27 PM
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Re: Building IB box

- Continuous output power: 350 watts RMS into 4 ohms
240 watts RMS into 8 ohms
- Frequency response: 20 to 160 Hz
- Adjustable crossover: 50Hz to 160Hz
- THD: <0.1%
- S/N ratio: >95db
- Bass boost: 6db @ 35Hz
- Input sensitivity @ max vol.: 120mV,
-Line out: 200mV @ max vol.
- Power: 240V 50Hz
- Module cutout approx 240W x 285mmH
- Remote receiver cutout 125W x 65Hmm.

this is the unit i was looking at. Not sure on the drivers yet, figure i would go to autobarn etc and find a couple of open air subs. You mentioned Xmas, what does this mean and also you mentioned that power requirements are a lot less in this type of arrangement. I build a few bandpass boxes for my cars over the years, all sound good. these subs usually require a fair bit to drive them. Sorry about the ignorance but am only new to this style of bass reproduction. Very interested though. However just build the house and another kid on the way, so i do have to be restrained a little with cost. any drivers that you know of that you would reccomend?

- Continuous output power: 350 watts RMS into 4 ohms
post #5 of 18 Old 10-25-07, 08:33 PM
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Re: Building IB box

just to add a little info, I'm savi up for a projector, have a set of Audioline 3 way with 2 12" drivers each, pioneer 6.1 dts amp with pioneer hdmi DVD player, feeding amp through optical lead. pretty simple but it packs reasonable punch.
post #6 of 18 Old 10-26-07, 02:23 AM
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Re: Building IB box

That sounds like the Jaycar amp - I've got the same specs here:

Xmax is the one-way excursion of the driver, and in conjuction with the area of the cone Sd, determines how much air you can move. To get decent SPLs at low frequencies, you need to move heaps of air.

The Americans are blessed with affordable high excursion drivers, but we Aussies are not so fortunate. Jaycar used to stock a 15 incher CS-2345 with a usable Xmax of 12.5mm but the mongrels have discontinued it!

At the moment, there doesn't seem to be an affordable IB driver for us. I had hoped you had stumbled across one, but it appears not.

If you think you're up to building a hi-pass filter, you could go for the ported design on this page

That amp driving a pair of the 12 inch drivers in a 190litre box tuned to 30hz with a 16hz hi-pass gets you around 117dB peak output.
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post #7 of 18 Old 10-28-07, 12:00 AM
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Re: Building IB box

I don't know why the US is so blessed with high-excursion- maybe for all the road-going boom-boxes?

Since the Mach5 drivers are sourced out of China, it shouldn't be too hard to convince them to make a stop in Aussieland at some point? The ones we make locally however, are cheap, especially since the dollar has fallen so much. Shipping is what kills it, I'm guessing.

As far as IB, don't bother unless you have high excursion drivers, or a lot (like 8) medium excursion ones. Box subs- when properly designed- are fantastic for the amount of sound they can put out. And you can build them like a HT- build the box in the ceiling if need be.
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post #8 of 18 Old 10-28-07, 07:00 AM
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Re: Building IB box

one of the reasons i wanted to go IB sub is because the box is hidden in the ceiling. Like mentioned, there is no reason why i couldnt fit a good sub box in the ceiling. Would be more affordable as well. will investigate this some more.
post #9 of 18 Old 10-28-07, 02:22 PM
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Re: Building IB box

I have to reinforce the message over the minimum Xmax requirement for IB.
2 x 15" car audio drivers in a house IB will disappoint and probably get wrecked on the first film you watch. I'm serious!
I searched for suitable IB drivers for ages in Europe without success.
In a car you get masses of low frequency gain. That's free bass by the bucket full. 2 x 15" in a car is great fun. But not in a house!
Using average 15" car audio drivers for an IB you'd probably need at least 8!
Only if you can get really long throw drivers with a stated Xmax of 22-25mm (or more) should you risk coming down to 4 15" drivers in an IB.
A box sub would be much safer and probably save you money.
If you share your driver specs the experts here will design you a great one!

Edit: I've just read your blog and enjoyed your pictures.
I still can't understand why you can't feel the low bass.

Last edited by Chrisbee; 10-28-07 at 02:33 PM.
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post #10 of 18 Old 10-28-07, 06:06 PM
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Re: Building IB box

If you cannot find or afford the right drivers for the IB install, you could consider the SLLT. You could get by with a couple of drivers for it. The best example we have here is the one Rodny did... the IB Makeover.

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