Multiple Subwoofers effect on extension - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 16 Old 07-16-2019, 08:44 AM - Thread Starter
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Multiple Subwoofers effect on extension

I understand that multiple subwoofers have a positive effect on overall bass response in a room and better response in multiple positions.

I am weighing my options for subwoofer upgrade and multiple subwoofers. I have a single SB2000, but its low extension isnt the best, especially in my room and starts to roll off in the mid 20s(as measured in REW).

I have the option to trade it in for a dual PC2000 setup. But it would be cheaper to simply grab a second SB2000. I have no DSP currently and likely wont for some time. My system is dedicated 2.1(or .2)

I am curious, do multiple subwoofers aid in better extension?

System: Cambridge 851A, Revel M126be, SVS SB2000, Cambridge DACMAGIC 100, JVC XL-Z1050TN, Rega RP6, Vincent PHO-8. A bunch of monster power conditioning junk V: Samsung NU8000, Nvidia Shield TV
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post #2 of 16 Old 07-16-2019, 12:46 PM
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Hi there! Adding another SB-2000 would enhance overall dynamic range and flatness/uniformity of your FR, but won't really change the extension. PC-2000 would do that for sure, however.
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post #3 of 16 Old 07-16-2019, 06:07 PM
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Have you moved the sub around to see it is caused by location? If you can find a better location to bring up the low end then stacking would add 6 dB.
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post #4 of 16 Old 07-17-2019, 05:05 AM - Thread Starter
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Quote:
Originally Posted by MKtheater View Post
Have you moved the sub around to see it is caused by location? If you can find a better location to bring up the low end then stacking would add 6 dB.
I have some nasty room issues higher up that im trying to figure out how to deal with without DSP, but the extreme low end looks like typical roll off to me. I dont think placement is going to help that much.

blue line is current placement speakers+sub
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post #5 of 16 Old 07-17-2019, 06:57 AM
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What size is your room? I like the little SB2000 , it was my first sub from SVS , but its not going to fill an entire room from top to bottom with bass and two still might not. I went from SB2000 to 2 PC2000's and the difference was night and day..
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post #6 of 16 Old 07-17-2019, 07:20 AM
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Quote:
Originally Posted by Locoliberty View Post
I understand that multiple subwoofers have a positive effect on overall bass response in a room and better response in multiple positions.

I am weighing my options for subwoofer upgrade and multiple subwoofers. I have a single SB2000, but its low extension isnt the best, especially in my room and starts to roll off in the mid 20s(as measured in REW).

I have the option to trade it in for a dual PC2000 setup. But it would be cheaper to simply grab a second SB2000. I have no DSP currently and likely wont for some time. My system is dedicated 2.1(or .2)

I am curious, do multiple subwoofers aid in better extension?
Move your sub to the middle of the room and take a measurement of the sub "nearfield" with the mic 1" away from the driver. This will allow you to see the "native" response of the sub with little to no room influence. If you see the same roll-off as the in-room response, you'll know it's the sub. If the response rolls off differently than the in-room response, you'll know it's the room.

Adding a 2nd sub does not change the F3, (-3 dB point) of the subs. It will increase the amount of output at the F3, but the F3 itself will not change.

You only get FR smoothing, and more consistent response across multiple listening positions if you distribute the subs around the room. Placing them as far apart as possible is the most likely way to get the optimal amount of smoothing. Co-locating, (i.e., stacking them or placing them side by side or very close together), will provide the most output, (up to 6 dB more), but will provide little to no smoothing and/or increased consistency. When co-located, subs will "mutually couple" and the wavefronts will propagate as one, single, combined wavefront. Therefore, you'll only have one transfer function of the soundwaves to the LP. Distributing them will provide a variable amount of increased output, but it can provide the maximal amount of smoothing because you have two separate transfer functions to the listening position, and you are statistically more likely to have one transfer function fill in for the deficiencies of the other transfer function.

If the ultimate goal is deeper extension, and the lack of extension is definitely related to the subs and NOT the room, then subs with deeper extension are the only solution. OTOH, if the lack of extension is caused by the room and modal response, then additional distributed subs can *potentially* provide deeper extension by improving the modal response.

Is that as clear as mud???

Good luck.

Craig
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post #7 of 16 Old 07-17-2019, 07:26 AM
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What are you crossing to the sub at? You do have that null at 100 Hz that having 2 subs would help with, but above that should be the mains. You should be crossing well below the issues that start at 200Hz and above. I'd expect SBIR and side reflections of your two mains to be your real problem based upon that chart. How far are the speakers from the front wall? Do you have any treatments for reflections? I'd try playing around with those more personally.
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post #8 of 16 Old 07-17-2019, 07:44 AM - Thread Starter
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Quote:
Originally Posted by craig john View Post
Move your sub to the middle of the room and take a measurement of the sub "nearfield" with the mic 1" away from the driver. This will allow you to see the "native" response of the sub with little to no room influence. If you see the same roll-off as the in-room response, you'll know it's the sub. If the response rolls off differently than the in-room response, you'll know it's the room.

Is that as clear as mud???

Good luck.

Craig
Clear as mud

I will look at testing nearfield when I get a chance. I currently assume it the sub as the drop off lines up with SVS's technical chart on their website.

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Originally Posted by mushroommunk View Post
What are you crossing to the sub at? You do have that null at 100 Hz that having 2 subs would help with, but above that should be the mains. You should be crossing well below the issues that start at 200Hz and above. I'd expect SBIR and side reflections of your two mains to be your real problem based upon that chart. How far are the speakers from the front wall? Do you have any treatments for reflections? I'd try playing around with those more personally.
I crossover at ~55hz, speakers(bookshelf) run fullrange(no low pass on the amp). so really anything above 60 is speaker related. I have some treatments but not enough, 1" corning DIY panels. 2 on the front wall, 2 on the side, and 1 at an open area of the far back wall. listening area is approximately 14x14 but room is 14x21

Speakers have slightly moved since picture. speakers are 21" from back wall and not sure on side wall distance as I measured from the console when moving.
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post #9 of 16 Old 07-17-2019, 08:14 AM
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Quote:
Originally Posted by Locoliberty View Post
Clear as mud
I crossover at ~55hz, speakers(bookshelf) run fullrange(no low pass on the amp). so really anything above 60 is speaker related. I have some treatments but not enough, 1" corning DIY panels. 2 on the front wall, 2 on the side, and 1 at an open area of the far back wall. listening area is approximately 14x14 but room is 14x21

Speakers have slightly moved since picture. speakers are 21" from back wall and not sure on side wall distance as I measured from the console when moving.
Oh yeah, you definitely want more, and thicker. As a quick test, you could move the two front panels on the wall to directly behind the speakers, just rest them on the floor, and measure again. I'm guessing you'd see an improvement. That's really where you want them is behind the speaker. I'd also push the mains as close to the front wall as possible, you only need to keep them the diameter of the port away from the wall to keep it from changing the tuning.
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post #10 of 16 Old 07-17-2019, 08:17 AM - Thread Starter
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Originally Posted by mushroommunk View Post
Oh yeah, you definitely want more, and thicker. As a quick test, you could move the two front panels on the wall to directly behind the speakers, just rest them on the floor, and measure again. I'm guessing you'd see an improvement. That's really where you want them is behind the speaker. I'd also push the mains as close to the front wall as possible, you only need to keep them the diameter of the port away from the wall to keep it from changing the tuning.
I was getting that second hump on the green line closer, but I wasnt THAT close before either. will continue to mess with tuning, New speakers should be arriving by the end of the week, so that will mess things all up again, I imagine.

Everything is expensive, so slowly things will be upgraded. Ofcourse buying equipment is more fun than replacing sound panels.
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post #11 of 16 Old 07-17-2019, 08:30 AM
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Quote:
Originally Posted by Locoliberty View Post
I was getting that second hump on the green line closer, but I wasnt THAT close before either. will continue to mess with tuning, New speakers should be arriving by the end of the week, so that will mess things all up again, I imagine.

Everything is expensive, so slowly things will be upgraded. Ofcourse buying equipment is more fun than replacing sound panels.
Oh for sure. I built my theater and got all the hardware then started slowly on the treatments. I hear you. That 90Hz bump in the green will be helped some if you move the panels behind the speakers when you push them closer to the wall I'd imagine. You need both actions in conjunction.

If you aren't aware, you can build panels extremely cheap that look decent so long as you're remotely handy.
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post #12 of 16 Old 07-17-2019, 08:38 AM - Thread Starter
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Oh for sure. I built my theater and got all the hardware then started slowly on the treatments. I hear you. That 90Hz bump in the green will be helped some if you move the panels behind the speakers when you push them closer to the wall I'd imagine. You need both actions in conjunction.

If you aren't aware, you can build panels extremely cheap that look decent so long as you're remotely handy.
Apartment living is a pain, but I should be able too at my dads place. Any guides for it? the corning panels seem nice but id like a way to mount them better. the backs are just the open fiberglass. I have like 10 finishing nails in the wall and the panels pushed into them. Red(red green show reference) would approve, but no one else should...

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post #13 of 16 Old 07-17-2019, 08:57 AM
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For making them, this is a good place to start: https://www.avsforum.com/forum/19-de...els-cheap.html

For mounting them, I always just use french cleats, either home made or the metal thin ones from home depot. Or you could just make them tall enough to rest on the ground and still cover up where you need. Could possibly just use finish nails and rest the inside of the top frame on them like it sounds like you do now. You'd want the nails in a stud though I'd wager.
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post #14 of 16 Old 07-17-2019, 09:02 AM
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While you may get some flatter response below 25Hz with optimizing dual SB2000 placement I think the chances are low that it will be a huge difference other than smoothing out the rest of the FR. If you do a significant % of movie/tv watching and you want more low end impact moving to dual PC-2000s is the way to go. There will be substantially more <30hz output/tactile feel.

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post #15 of 16 Old 07-17-2019, 11:16 AM
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Since you have REW, have you moved the sub you have to all available locations in the room and measured the response? In my room I did a dozen locations and found some areas simply sucked for low end bass and others were significantly better. It may simply be a matter of real estate, finding a spot that adds whatever bass spectrum you feel is lacking (in my case it was finding a spot that has peaks where my "best" spot has nulls).

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post #16 of 16 Old 07-18-2019, 11:11 AM
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Quote:
Originally Posted by Locoliberty View Post
I have some nasty room issues higher up that im trying to figure out how to deal with without DSP, but the extreme low end looks like typical roll off to me. I dont think placement is going to help that much.

blue line is current placement speakers+sub
You need to change the graph from 3-50hz if that is the range you are using, that graph is not showing a huge drop off at all.

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