| Re: Multisubs [message #61321 is a reply to message #61319] |
Mon, 02 November 2009 14:21   |
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Wayne Parham
Messages: 18789
Registered: January 2001
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Illuminati (33rd Degree) |
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| feket663 wrote on Mon, 02 November 2009 11:12 | Which amp/x-over combo do you recommend for sub applications?
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I personally use a Class A FET amplifier, the ProFet amp from Selectronic. This requires a low-pass filter in front of the ProFet amp, and I have played with several types from passive line level filters to various off-the shelf devices.
The one I ended up liking best is kind of unconventional - I went through a cheap little car crossover, rebuilding it with all good capacirtors and replacing the op-amps with Burr Browns. So it's kind of a fun little project thing that really sounds good. This unit allows me to select low-pass of 50-90Hz with a gentle slope (second-order) that's perfect for blending with the mains. Flanking subs (less than 10 feet from the mains) can usually be low-passed fairly high, say 90Hz or even 120Hz in some cases. Distant subs should probably be low-passed at 50Hz. That will still offer some blending up to around 75Hz because of the gentle second-order slope.
Most people use a plate amp because it's easy and affordable. I see nothing wrong with that. Cut the hole in the back of your sub cabinet to fit, connect it up and bolt it on and presto, you have a powered sub. Most of them I've seen had fourth-order low-pass filters though, which means you'll probably set the frequency a little higher to get blending just right. Still, very do-able, just bolt it onto the back of the subwoofer cabinet. Something like this would work just fine:
A person could also use a high-power chip amp, something like the National LM3875 or LM3886. All you need is a handful of passive parts and a power supply to build a good amp with one of these chips. The larger chip (LM3886) can deliver about 65W into a 4Ω load. That's about the same kind of power my ProFet provides, and it's enough to shake the house. The power supply can be anywhere from 20V to 80V, so you could even use a pre-made power supply board, something like this:
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