What exactly will adding a 2nd sub do? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 10-10-2003, 08:02 PM - Thread Starter
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I know it will "add 6db of gain" but what does that amount to in terms of a real world experience? Is it simply louder? Do you "feel" the bass more without actually having it set any louder than it was with a single sub?

I have a single SVS 25-31PC+ that's doing an excellent job in a problematic room (4500 cubic feet with openings to other areas and a mostly tile floor). I don't need more volume but I can't help but wonder what adding a second one would really do though. I suppose that's just part of the condition. :)

-Doug
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post #2 of 7 Old 10-10-2003, 08:12 PM
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INcreased Headroom!, Increased Output!, Potentially help to smooth out the room's frequency response if properly positioned!

One sub is never enough!!!

Goodbye to a great audio and video genius and writer... JOHN GANNON. I enjoyed your friendship, wit and a nice long run we took around Indianapolis at CEDIA years back... and for buying my Runco 980 Ultra years back... you saved my ass! Rest in peace.
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post #3 of 7 Old 10-10-2003, 08:22 PM - Thread Starter
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Settle down! :)

Something else I meant to ask, I'm planning on adding a 31 band EQ to the mix sometime soon whether I get a 2nd sub or not. Should I consider a dual channel so I could EQ them seperately or would a single and Y cable do the trick? Odds are they would be right next to each other if I ever decided to add a second sub. A dual channel would cost less than two seperates and I would have a little bit of future insurance should I decide to go that route.

Edit: That's a hell of a nice theater you have there. Excellent job.

-Doug
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post #4 of 7 Old 10-11-2003, 09:48 PM - Thread Starter
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*bump for the eq question*

-Doug
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post #5 of 7 Old 10-12-2003, 03:13 PM
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I would use a single channel eq.

Explanation as follows...
Bass modes and standing waves will be location dependant....what I mean is this:

Standard one sub: start by finding the sub placement that gives the flattest respose in your listening position. (usually a corner and a couple inches can make a large difference). It is important to remember than small changes in seating position also have a profound effect on the bass. A foot to the side and whole other frequencies will be affected.

With two subs: try to have two that are the same, having two different types of subs not collocated will make eq'ing very difficult. The placement can get even trickier with two because now you have another variable. However, it will allow you to use placement to get rid of your worst nulls. After you have the placement down and the best freq response you can get...then use the eq on the pair. Always try to get rid of peaks by eq, nulls by sub position, if you eq out a null (where you have a standing wave) you will drain you sub of tons of performance.

I am assuming you are using the subs in mono? When you get into a larger room and trying for stereo bass it is more difficult and you will have to get someone else to fill in.

Also a quick plug, the Behringer (sp?) DSP 1124 is a great piece of equipment to eq a sub, highly recommended. Has 12 bands X 2 channels of parametric eq (pick band width, freq and boost/cut) for about $100. I am at +/- 1.5 dB from 25 to 80Hz using only 3 bands (the magic of parametric). I had a 18+ dB swing before from 45 to 55 Hz. You can really tighten up bass transients by fixing these problems.

Paul Taatjes
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post #6 of 7 Old 10-12-2003, 05:35 PM
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I'm trying this: 2 12" Shiva driver subwoofers (used in the sealed Adire Audio Rava) to 20-25Hz in 4-way mains for the stereo sub effect (crossed at about 100Hz with the mid-low range or "woofer" driver). Then 1 15"-18" subwoofer in the corner that goes WAY down (16Hz,,,) deep crossed at 40-50Hz. I shouldn't be able to localize that in critical listening. ;)

In a way I'd really have 3 subs. :D I may want to bi-amp my mains now, but I could just use a stereo amp (and/or use with a good 5 channel multi-channel amp) and use higher efficiency for the top 3 drivers.
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post #7 of 7 Old 10-12-2003, 06:12 PM - Thread Starter
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Thanks for the response ptaaty. I've seen several people speak highly of the Behringer eq you mention. When the time comes to add an eq I will definitely give that one a look.

-Doug
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