| Subwoofer hook-up [message #68844] |
Thu, 04 August 2011 15:24  |
Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA
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Illuminati (2nd Degree) |
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With a passive pre I don't have line level out and can't remember which is better/worse: run second set of wire from amp speaker terminals to high level in or single run to sub high-level then to speakers?
I've even heard of running wire from speaker terminals to sub hi-level which would be convenient but wouldn't it change the impedance?
One more thing, following the Diyaudio thread on imaging that became a sub-woofer thread, what would you use to SUM the channels? Geddes wasn't implying that recordings do that, was he?
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| Re: Subwoofer hook-up [message #68848 is a reply to message #68844] |
Thu, 04 August 2011 16:33  |
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Wayne Parham
Messages: 18677
Registered: January 2001
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Illuminati (33rd Degree) |
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With a passive preamp, you pretty much have to use mains that have input adjustments in order to set the relative volume levels between mains and subs. This is true with active preamps too, if there is just one output. That's how I run mine - I have an active preamp, just because I want a little more gain. I also wanted the remote control, but you can get passive preamps that have remote volume. Just a remote controlled switcher/attenuator, really. The output of the preamp goes both to the sub amps and to the mains. Actually, I have the sub crossover after the preamp, again, so I can have volume control of both mains and subs simultaneously.
As for summing, I prefer to run what I call flanking subs - in stereo. They're the ones that are just a couple feet below, beside and behind the mains. They'll smooth the range from 80Hz or 100Hz up to the Schroeder frequency, and this is tremendously important, in my opinion. I think the worse room modes are actually in the lower midrange, the ones from the back wall slap and the vertical modes, floor bounce, etc. They're almost always around 100Hz to 140Hz, and are a huge notch, both in amplitude and width. They can make voices kind of thin, or sometimes seem to have an opposite effect of making them sound throaty. It depends on where the notch is, and how it contrasts with the peaks that surround it.
For the more distant subs, I think it's a coin toss as to whether or not you want to sum them or run them in stereo too. If you have just one more sub, then obviously, you'll have to sum it. If you have a 5-channel system, the solution is easy - you just run the subwoofer output to the lone distant sub. If you have two subs in addition to the flanking sub, then you have a choice. You can run them the same way, just paralleled off the 5-channel subwoofer output. Or if you don't have that output, only have stereo, then you can either sub the two channels with a couple resistors in the preamp line or you can run them in stereo too. Most of the deep bass is already summed in the recordings anyway.
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