Calling those with multiple subwoofers - Page 3 - AVS | Home Theater Discussions And Reviews
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View Poll Results: Why did you incorporate multiple subwoofers in your home theater?
To even-out the bass response in the room 26 32.91%
To increase overall SPL 2 2.53%
To even-out bass response and increase overall SPL 51 64.56%
Voters: 79. You may not vote on this poll

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Old 05-20-2014, 06:55 PM
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Quote:
Originally Posted by Spanglo View Post

Truth be told I was able to get a good response by individual EQ, but it took forever and it was only good for one seat. I thought I had nailed it by getting a good response at the MLP, but when I tested other seats the response was again atrocious. So there went hours of testing different distances, levels, phase, and EQ.

Eventually I smartened up and averaged the response across multiple couches, then global EQ, and finally Audyessy. The response at the MLP wasn't as great as before, but it was consistently good on both couches so I considered that a win.

It was a good learning experience, because now I can do in mins what took me hours to do before.

I've found that sub symmetry can help improve seat-to-seat consistency in a rectangular room. By that, I mean symmetrical subs along the length and width.
Some examples of layouts that are symmetrical on both axes:
1) 2 subs: front center + rear center
2) 4 subs: corners
3) 4 subs: front 1/4 3/4, rear 1/4 3/4

That REW simulator is great for showing this when you enable multiple mic positions.

If you have better seat-to-seat consistency, the same EQ will work for a bigger area.

When I had 2 subs, I actually got the best results with opposing corners. This sacrificed seat-to-seat consistency, but gave a lot more room gain than front & rear center placement, which was a bigger concern in my large room. 4 subs in corners gave me both good room gain and good seat-to-seat consistency.
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Old 05-20-2014, 07:23 PM
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Quote:
Originally Posted by rcohen View Post

I've found that sub symmetry can help improve seat-to-seat consistency in a rectangular room. By that, I mean symmetrical subs along the length and width.
Some examples of layouts that are symmetrical on both axes:
1) 2 subs: front center + rear center
2) 4 subs: corners
3) 4 subs: front 1/4 3/4, rear 1/4 3/4

That REW simulator is great for showing this when you enable multiple mic positions.

If you have better seat-to-seat consistency, the same EQ will work for a bigger area.

When I had 2 subs, I actually got the best results with opposing corners. This sacrificed seat-to-seat consistency, but gave a lot more room gain than front & rear center placement, which was a bigger concern in my large room. 4 subs in corners gave me both good room gain and good seat-to-seat consistency.

Yes sub symmetry definitely helps. Before I was using the width of the room, with both couches up against walls, and horrendous sub placement (no choice due to furniture arrangement). Pretty much text book "how not to set up sound system", but it actually didn't sound bad and I got good response after EQing the subs and mains.

Now I'm utilizing the length of the room, subs place front center, side centers, and one in the rear corner (until I get rid of a couch, then it's going rear center. MLP is no longer against a boundary. The sweeps I ran the other night look very good with no EQ, and fairly even everywhere I placed the mic. What I was hoping would happen when I decided to rearrange the room.

 


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Old 05-21-2014, 01:34 AM
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Quote:
Originally Posted by Spanglo View Post

Truth be told I was able to get a good response by individual EQ, but it took forever and it was only good for one seat. I thought I had nailed it by getting a good response at the MLP, but when I tested other seats the response was again atrocious. So there went hours of testing different distances, levels, phase, and EQ.

Eventually I smartened up and averaged the response across multiple couches, then global EQ, and finally Audyessy. The response at the MLP wasn't as great as before, but it was consistently good on both couches so I considered that a win.

It was a good learning experience, because now I can do in mins what took me hours to do before.

indeed, can whip out measurements now like nothing.
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Old 05-21-2014, 10:47 AM - Thread Starter
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Thinking of this for 4 subwoofers:

Option 1

1. Calibrate each subwoofer to 75 dB manually with a SPL meter and calibration DVD.
2. EQ the subwoofers as one big group along with a 75 dB combined output for all subwoofers (through "automated" calibration).

Option 2

1. Set the gain dial/nob at the same position for all the 4 subwoofers.
2. EQ the subwoofers as one big group along with a 75 dB combined output for all subwoofers.

Basically, I want to somewhat calibrate the SPL to 75 dB for each subwoofer prior to EQing them and calibrating them to 75 dB as a group because I wouldn't want one or more subwoofers working harder than the others. I want all subwoofers working equally as hard. But I guess Option 2 will achieve this since I will be setting the gain dial/nob on the subwoofers to the same setting/position.
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Old 05-21-2014, 11:03 AM
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Ok, quick question for you multi-sub owner here.

I have 2 PB12-Plus sitting at opposite corner of the room (front right & rear left). I'm think to take advantage of SVS's trade up program & trade them up for 2 PB13-Ultra. However, on second thought, I'm thinking for about the same money, would getting a 3rd PB12-Plus for the front left corner be a better choice? My main goal is for better FR at my main seat or from seat to seat with more output would be the icing on the cake for me.

Here's my current FR at the MLP, it isn't bad with the dual sub setup, but just wondering if adding a 3rd would further smoothen out the FR for more seat? Or with my current FR, it won't help a whole lot & probably better go for more output for a dual PB13-Ultra setup?

Thanks in advance. cool.gif

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Old 05-21-2014, 12:10 PM
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Quote:
Originally Posted by Kain View Post

Thinking of this for 4 subwoofers:

Option 1

1. Calibrate each subwoofer to 75 dB manually with a SPL meter and calibration DVD.
2. EQ the subwoofers as one big group along with a 75 dB combined output for all subwoofers (through "automated" calibration).

Option 2

1. Set the gain dial/nob at the same position for all the 4 subwoofers.
2. EQ the subwoofers as one big group along with a 75 dB combined output for all subwoofers.

Basically, I want to somewhat calibrate the SPL to 75 dB for each subwoofer prior to EQing them and calibrating them to 75 dB as a group because I wouldn't want one or more subwoofers working harder than the others. I want all subwoofers working equally as hard. But I guess Option 2 will achieve this since I will be setting the gain dial/nob on the subwoofers to the same setting/position.
Option 1 is "level-matching. If you're using identical subs, this approach will work, but it's not ideal. You could, (and most likely would), end up with subs with different gain settings.

Option 2 is "gain-matching." If the subs are identical, this is the more optimal approach. It will ensure all the subs are working equally hard. If you use M/S subs, the M/S pairs will be gain-matched by default, (the amp driving the Master also drives the Slave, so there is only one gain setting.) Then you would just set both Masters to the same gain setting. If you put one M/S pair in the front corners and one M/S pair in the rear corners, you can set different delays, (Distances) for the front and rear M/S pairs. Keep their levels the same so you retain the gain-match through the entire gain structure of the system. If need be, "split the difference" in the trim settings. IOW, if the front M/S pair is set to -2 and the rear is set to -6, split the difference and set them both to -4. This will ensure they both receive the same input signal and they're both working identically.

Craig

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Perfection is not attainable, but if we chase perfection we can catch excellence."

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Old 05-21-2014, 12:13 PM
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Quote:
Originally Posted by landshark1 View Post

Ok, quick question for you multi-sub owner here.

I have 2 PB12-Plus sitting at opposite corner of the room (front right & rear left). I'm think to take advantage of SVS's trade up program & trade them up for 2 PB13-Ultra. However, on second thought, I'm thinking for about the same money, would getting a 3rd PB12-Plus for the front left corner be a better choice? My main goal is for better FR at my main seat or from seat to seat with more output would be the icing on the cake for me.

Here's my current FR at the MLP, it isn't bad with the dual sub setup, but just wondering if adding a 3rd would further smoothen out the FR for more seat? Or with my current FR, it won't help a whole lot & probably better go for more output for a dual PB13-Ultra setup?

Thanks in advance. cool.gif

You should probably start your own thread. Your questions are dissimilar enough from Kain's that a dedicated thread would be more appropriate. Besides, you'll get more and better responses if you put your SVS questions in the title.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

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Old 05-21-2014, 12:29 PM
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Quote:
Originally Posted by craig john View Post

You should probably start your own thread. Your questions are dissimilar enough from Kain's that a dedicated thread would be more appropriate. Besides, you'll get more and better responses if you put your SVS questions in the title.

Craig
Thanks. smile.gif
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Old 05-21-2014, 01:20 PM
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Quote:
Originally Posted by Kain View Post

Thinking of this for 4 subwoofers:

Option

1. Calibrate each subwoofer to 75 dB manually with a SPL meter and calibration DVD.
2. EQ the subwoofers as one big group along with a 75 dB combined output for all subwoofers (through "automated" calibration).

Option 2

1. Set the gain dial/nob at the same position for all the 4 subwoofers.
2. EQ the subwoofers as one big group along with a 75 dB combined output for all subwoofers.

Basically, I want to somewhat calibrate the SPL to 75 dB for each subwoofer prior to EQing them and calibrating them to 75 dB as a group because I wouldn't want one or more subwoofers working harder than the others. I want all subwoofers working equally as hard. But I guess Option 2 will achieve this since I will be setting the gain dial/nob on the subwoofers to the same setting/position.

The problem I see with this is that you are assuming that setting the gain knobs in the same position is going to result in the exact same output. When in reality , the gain knobs are not some sort of highly calibrated control. You have a pretty random chance of being even remotely close to the same exact output with this method. The gain knob is simply a very non precise adjustment. Using an spl meter is the only way to actually match the output closely.

Also do not calibrate each one to 75 as this will make the combined output well over 80. Try setting each one to 68 or 69
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Old 05-21-2014, 01:41 PM
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Originally Posted by bear123 View Post

The problem I see with this is that you are assuming that setting the gain knobs in the same position is going to result in the exact same output. When in reality , the gain knobs are not some sort of highly calibrated control. You have a pretty random chance of being even remotely close to the same exact output with this method. The gain knob is simply a very non precise adjustment. Using an spl meter is the only way to actually match the output closely.

Also do not calibrate each one to 75 as this will make the combined output well over 80. Try setting each one to 68 or 69
From Post 18 in this thread where I said:
Quote:
To gain-match IDENTICAL subwoofers, you would set their gains to the identical positions, no matter how they measure at the LP. If you want to get really compulsive about it, you could move each sub, one at a time, to the middle of the room. (Moving to the middle of the room reduces any interactions of the sub with the room and enables you to measure the "native" response and output of each sub.) Measure each sub nearfield, with the measurement mic 2" from the driver. (Turn the volume down before you do this because the sub will measure much higher nearfield than it will in-room.) Place tape on the floor where the sub is positioned and don't move the measurement mic when you move each sub in and out of position. Set all their gains so they measure exactly the same on the nearfield measurement. Then move each sub back into its' in-room position, send each of them the exact same signal, and they will all be "gain-matched." I use about 83 dB as the nearfield SPL setting. When I move the subs back to their in-room placements, they usually measure 65 to 70 dB, and then when combined, they're in the vicinity of 75 dB, or at least close enough that I can use the subwoofer trim control to get them properly calibrated with the speakers.

The purpose of doing the above is to ensure that, if there are small variations in the amps or drivers, they are accounted for in the gain-match. If you're not concerned about those small variations, then, as I said, you can just set the gains on all of the sub amps to the same setting.

So yeah... thanks.

Craig
its phillip likes this.

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

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Old 05-21-2014, 02:11 PM
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Sorry, forgot to read back 50 posts before replying.

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Old 05-21-2014, 04:04 PM
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Not your fault, Kain forgot to read back 50 posts before posting,lol
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Old 05-22-2014, 04:23 AM
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I understand the difference in gain and level matching. IMO level matching gives a nice FR at the main listening position. I have used this method for several years with different subs, non-identical and identical subs and have not had problems with any of the subs being over driven. Currently, I am using level matching with two sealed and two vented subs. One sealed and one vented sub is around 20 ft. from the MLP. I have an odd shaped room that does not allow for four symmetrically placed subs. My point is over driving a sub may not be that great of an issue in most HT. I calibater the 4 subs ea. to around 66 db and PEQ them as sealed pair and vented pair, then final EQ to tie them together.
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Old 05-22-2014, 04:42 PM
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I like level matching my 4 subs. After coming from a dual setup. I'll never go back. Matter of fact, by next year, I'm looking in getting my 5th and 6th S2. Multi subs is the way to go. smile.gif
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Old 05-22-2014, 05:29 PM
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Let me get this straight. You have 4 JTR S2's and want more?

Receiver - Denon 4311CI
Speakers - Klipsch RF-82 II rest coming soon
Subs - Rythmik FV15HP's
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Old 05-22-2014, 06:32 PM
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Originally Posted by JT78681 View Post

Let me get this straight. You have 4 JTR S2's and want more?

Yea, I wanted to do it together with my speaker upgrades. But I need to buy some amps and a pre-pro for the speakers. I went with 3 JTR 215's and 4 S8's.
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Old 05-24-2014, 08:17 AM
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Originally Posted by rhed View Post

I like level matching my 4 subs. After coming from a dual setup. I'll never go back. Matter of fact, by next year, I'm looking in getting my 5th and 6th S2. Multi subs is the way to go. smile.gif

WOW! That's some serious subwoofage. 

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