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Any reason not to use 3 subwoofers?

post #1 of 15
4/17/10 at 1:27pm
Thread Starter 
I just bought two F12 subs to replace my Older JBL 10".

My original thought was to have two F12's, but I'm thinking now. Why not use all three?

Is there any obvious reasons not to? I will have two up front, and one somewhere else.

Clay
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post #2 of 15
4/17/10 at 2:00pm
Quote:
Originally Posted by poolboyclay View Post

I just bought two F12 subs to replace my Older JBL 10".

My original thought was to have two F12's, but I'm thinking now. Why not use all three?

Is there any obvious reasons not to? I will have two up front, and one somewhere else.

Clay

No reason not to use all three. Multiple subs, along with increased output gives a smoother in-room response. I use five subs in my room.
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post #3 of 15
4/17/10 at 2:01pm
Well if you had four that would be a reason not to use three. Otherwise I would say do it. Since the one is smaller it will not contribute as much output but that's ok. Also its addition will not add much output to the total but what it can do is help to smooth out the overall distribution of bass in the room. It may not go as low as the others but that's also ok, it can still contribute to improving the uniformity in the range it can work.

mk
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post #4 of 15
4/17/10 at 2:18pm
I've used 2 Velodynes for years. If my room would accomodate 4, I'd go for it. You can never have too much clean bass.
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post #5 of 15
4/17/10 at 2:26pm
Quote:
Originally Posted by Montekay View Post

Well if you had four that would be a reason not to use three.

That was going to be my answer.
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post #6 of 15
4/20/10 at 3:20am
Thread Starter 
Okay then, 3 it is for now!

I keep hearing, "not with three he can't" in my mind.

They Arrive TODAY! I guess I'll have to get sick at work.

Thanks Guys!

Clay
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post #7 of 15
4/20/10 at 5:04am
1. A sub which cannot perform as well as the other might hinder performance and SQ.
2. An even amount of subs would give a more even response than an odd number.
3. You would get more SPL not necessarily better SQ.
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post #8 of 15
4/20/10 at 5:06am
3 *identical* subs would be worth doing. I use 3 Submersives and that system works quite well. However, the OP is considering 2 identical subs, (dual F12's) and 1 sub with (likely), significantly less capability, (JBL 10"). In this situation, I expect the JBL sub to do nothing but hold back the F12's. At higher output, it will compress and distort long before the F12's, wasting their headroom.

More importantly, with less extension, it will cause the F12's calibrated levels to be lower, reducing the levels of their deepest output. For example, the F12 has extension to 14 Hz, (-3 dB). The JBL 10" sub is probably in the 28 to 35 Hz range. When the *combined* output of the 3 subs is calibrated to 75 dB with the speakers, the level of each individual sub is reduced 3 to 6 dB. The net effect is that the response below 28/35 Hz is reduced relative to the rest of the range.

The only situation I would suggest using the JBL sub is if the dual F12's have a large "hole" somewhere in the response. Then the JBL could be used to "fill in" that hole. However, doing so would require finding a placement that has a "complimentary" response to the F12's in the area of the hole. This would require the ability to measure the response, and the time and effort to find the correct placement. Short of that, I suggest leaving the 10" JBL sub out of the system.

Craig
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post #9 of 15
4/20/10 at 10:26am
Quote:
Originally Posted by craig john View Post

3 *identical* subs would be worth doing. I use 3 Submersives and that system works quite well. However, the OP is considering 2 identical subs, (dual F12's) and 1 sub with (likely), significantly less capability, (JBL 10"). In this situation, I expect the JBL sub to do nothing but hold back the F12's. At higher output, it will compress and distort long before the F12's, wasting their headroom.

More importantly, with less extension, it will cause the F12's calibrated levels to be lower, reducing the levels of their deepest output. For example, the F12 has extension to 14 Hz, (-3 dB). The JBL 10" sub is probably in the 28 to 35 Hz range. When the *combined* output of the 3 subs is calibrated to 75 dB with the speakers, the level of each individual sub is reduced 3 to 6 dB. The net effect is that the response below 28/35 Hz is reduced relative to the rest of the range.

The only situation I would suggest using the JBL sub is if the dual F12's have a large "hole" somewhere in the response. Then the JBL could be used to "fill in" that hole. However, doing so would require finding a placement that has a "complimentary" response to the F12's in the area of the hole. This would require the ability to measure the response, and the time and effort to find the correct placement. Short of that, I suggest leaving the 10" JBL sub out of the system.

Craig

Each sub is individually calibrated. Then you set the level for all three subs together. This means each sub will have to put out less output to get the same total SPL. This means that you gain headroom and SPL. You do not lose by using the smaller sub. You just do not gain as much. The smaller weaker sub may not add much if anything to the SPL, but it can help even out the response. A particular advantage would be using the weaker sub in a near field position.
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post #10 of 15
4/20/10 at 10:33am
One other consideration: Many rooms have substantial room gain in the mid-bass regions, which is right where the old JBL is cranking out most of it's output. Using all 3 might well create a huge gain and surround you with unpleasant boominess. I'd start with careful placement and setup of the 2 new subs and use that setup for a few weeks. You should find no need for adding the 3rd.
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post #11 of 15
4/20/10 at 12:43pm
I would make sure all three subs are operating in identical frequency ranges (25 Hz-80 Hz, for instance), and if so, use all three. If one sub has an f3 of 40 Hz, though, the system will calibrate overall bass level, and that level will be down a few deebers below 40 Hz. This is the same reason I vehemently advise against running front speakers with 40 Hz bass as "large" with subwoofers.

We ran twelve subs at our CEDIA demo last September, but they were identical, and calibrated the same. Tons 'o subs are tons 'o fun.
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post #12 of 15
4/20/10 at 1:41pm
Thread Starter 
Quote:
Originally Posted by Paul Scarpelli View Post

I would make sure all three subs are operating in identical frequency ranges (25 Hz-80 Hz, for instance), and if so, use all three. If one sub has an f3 of 40 Hz, though, the system will calibrate overall bass level, and that level will be down a few deebers below 40 Hz. This is the same reason I vehemently advise against running front speakers with 40 Hz bass as "large" with subwoofers.

We ran twelve subs at our CEDIA demo last September, but they were identical, and calibrated the same. Tons 'o subs are tons 'o fun.

Theoretically, the JBL is 27hz to 150, and the BIC F12 is 25hz to 200. Would you consider that a problem?
Keep in mind these will be used 90% movies and 10% or less music.

Clay
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post #13 of 15
4/20/10 at 2:41pm
As long as they're both down the same amount (-3 dB, -6 dB, whatever) at 27 Hz and 25 Hz, that's no problem. If one sub has less output and won't play as loud, it should be run at a lower level. Ideally, you'd like all three subs to run out of headroom at the same time, instead of two subs sounding good, and one sounding like hippo flatulence.
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post #14 of 15
4/20/10 at 5:23pm
Quote:
Originally Posted by poolboyclay View Post

Theoretically, the JBL is 27hz to 150, and the BIC F12 is 25hz to 200. Would you consider that a problem?
Keep in mind these will be used 90% movies and 10% or less music.

Clay

My previous post was based on the assumption you were talking about the Rythmik F12 sub, which is a much more capable sub than the BIC F12 sub.
http://www.rythmikaudio.com/F12_specs.html
The discrepancy between the Rythmic F12 and the JBL would be great enough to justify my previous comments.

If your new subs are BIC F12's, then the JBL sub is similar enough that using all 3 together could be an good system. Just follow Paul's recommendations and you should be good to go.

Craig
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post #15 of 15
4/23/10 at 4:47am
I'm running 4 M&K subs in my room. At each side in the front wall I have a stack.

In the RH corner
MX125 150w 2x12inch [20-200Hz] with a V75 75w 1x12inch [20-200Hz] on top

In the LH corner
MX5000 400w 2x12inch [16-200Hz] with a V76 1x12inch [20-200Hz] on top.

The bass has real solid smooth presence when needed with a good transitition to insane as it goes down low. I've tried it with each one then as I've added a sub the bass has just got better and better without getting "boomy".

To demo the difference with the LFE I show the new Star Trek movie on blu-ray with the scene when the Vulcan planet gets sucked into a black hole.

With all the subs it's just awesome.

One problem with multiple subs is running RCA splitters from the sub output on the reciever and getting an unequal signal strength. So to get around this issue I took a cheap shortcut by using an AV splitter amplifier like this.
http://www.jaycar.com.au/productView...T&SUBCATID=293
Probably not ideal but better than using RCA splitters

Cheers
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