Calibrating Two Different Subs - Need Help! - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 19 Old 01-02-15, 12:04 AM Thread Starter
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Calibrating Two Different Subs - Need Help!

Well, calibrating in terms of trying to get them to contribute and not cancel. I have two subs in the living room currently, and they are not quite the same. Both 10", one down-firing, one front-firing, both ported, one from 2013 and the other from 1998, both have 150W continuous, same adjustability.

From my reading, I am seeing that, I guess, I cannot gain match these things, but I can level match them, sort of. Really all I want is for them to sound good and not actually be fighting each other. My AVR has only one sub-out, and I use a splitter from there - room is large and open on two walls, tall ceilings - what a mess!

Also just downloaded REW and am looking at mics now - hoping that'll give me the tools to balance this system. Until I get REW up and running, is there a quick and easy method for making sure the two different subs aren't fighting each other using nothing more than an SPL meter?
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post #2 of 19 Old 01-02-15, 09:54 AM
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Re: Calibrating Two Different Subs - Need Help!

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Philm63 wrote: View Post
Well, calibrating in terms of trying to get them to contribute and not cancel. I have two subs in the living room currently, and they are not quite the same. Both 10", one down-firing, one front-firing, both ported, one from 2013 and the other from 1998, both have 150W continuous, same adjustability.

From my reading, I am seeing that, I guess, I cannot gain match these things, but I can level match them, sort of. Really all I want is for them to sound good and not actually be fighting each other. My AVR has only one sub-out, and I use a splitter from there - room is large and open on two walls, tall ceilings - what a mess!

Also just downloaded REW and am looking at mics now - hoping that'll give me the tools to balance this system. Until I get REW up and running, is there a quick and easy method for making sure the two different subs aren't fighting each other using nothing more than an SPL meter?
Since they are not the same model sub, you will be in for a challenge. Level matching is one thing, but you also need to get their phase and delays in line. Manually, this will be a cumbersome and near impossible task since the subs are different. It's usually not advisable to run dual subs unless they are the same model. May want to abandon and look into purchasing duals and maybe a receiver that has Audyssey XT32 and Sub HT Eq. This feature will set the levels and delays for you.
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post #3 of 19 Old 01-02-15, 09:59 AM Thread Starter
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Re: Calibrating Two Different Subs - Need Help!

That was my concern as well, that mismatched subs would be difficult to balance. I had one from several years back, and it made its way down to the basement for a while after I got a newer one, and then after the newer one broke I got another new one and decided also to bring the older one back upstairs and try a dual setup. All this before I started researching about acoustics.

I'm actually toying with the idea of dual SVS PB-2000's to replace these - perhaps I should just accept what I have for now until the replacements enter the scene - then I can worry about gain-matching and all that, no?

Thanks for the input.
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post #4 of 19 Old 01-02-15, 10:02 AM
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Re: Calibrating Two Different Subs - Need Help!

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That was my concern as well, that mismatched subs would be difficult to balance. I had one from several years back, and it made its way down to the basement for a while after I got a newer one, and then after the newer one broke I got another new one and decided also to bring the older one back upstairs and try a dual setup. All this before I started researching about acoustics.

I'm actually toying with the idea of dual SVS PB-2000's to replace these - perhaps I should just accept what I have for now until the replacements enter the scene - then I can worry about gain-matching and all that, no?

Thanks for the input.
I would keep status quo until going to the dual PB-2000's. SVS customer support is really good and they could probably give you good advice on how to get them in line.
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post #5 of 19 Old 01-02-15, 12:13 PM
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Absolutely. SVS CS is unmatched. If you want better than nothing at least, set them individually (one off, then the other) for about 72db using the internal test tone. This may yield 75-80 combined output. Then adjust phase controls til you get the most output, then set the trim to suit to taste. Try to stay below +values. This can add distortion into the signal. It's a quick dirty way, but better than flying blind. A pair of PB 2k's will be immeasurably better than what's in place now, and SVS will certainly help get things smoothed out. Is there a way to place them at the rear of the room?
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post #6 of 19 Old 01-02-15, 01:47 PM
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U mentioned pb2k's. Thought I'd share these. Cylinder subs are favorites of mine.
http://www.svsound.com/subwoofers/cylinder/pc-2000
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post #7 of 19 Old 01-05-15, 05:35 PM
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Re: Calibrating Two Different Subs - Need Help!

Co locate them and the outputs will sum.

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post #8 of 19 Old 01-07-15, 06:16 AM
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Re: Calibrating Two Different Subs - Need Help!

Quote:
Philm63 wrote: View Post
Well, calibrating in terms of trying to get them to contribute and not cancel. I have two subs in the living room currently, and they are not quite the same. Both 10", one down-firing, one front-firing, both ported, one from 2013 and the other from 1998, both have 150W continuous, same adjustability.

From my reading, I am seeing that, I guess, I cannot gain match these things, but I can level match them, sort of. Really all I want is for them to sound good and not actually be fighting each other. My AVR has only one sub-out, and I use a splitter from there - room is large and open on two walls, tall ceilings - what a mess!

Also just downloaded REW and am looking at mics now - hoping that'll give me the tools to balance this system. Until I get REW up and running, is there a quick and easy method for making sure the two different subs aren't fighting each other using nothing more than an SPL meter?
Their timing might be different but that should be of less concern. The idea is that these 2 subs SHOULD sort of cancel each other out. But not in a bad way. One may have peaks and troughs in some frequencies, and the other in different frequencies. In that way, they actually fill in the other sub's troughs or remove those peaks. So that is a Good Thing.

The best way to hear the benefit between one and two subs is the sound of the bass "outside" the room. In some places there may be too much bass, and in others too little. This will be most easily evident in Open Plan homes. As you walk from one end to the other of the space you'll hear the bass get louder or softer if there is one sub. If you have two you'll find the bass will be much more even throughout the space. What multiple subs do is reduce the comb effect caused by the room's natural nodes by evening them out. Flat bass with no peaks to annoy the neighbours, or suck-outs to annoy you.

But it is important to get the settings right. Firstly the subs themselves. If you can (or dare to!) put one in the corner and the other in the middle as these positions are the 'best' and 'worst' for bass peaks and cancellations caused by the room nodes. Against the wall but in the middle between the corners is a good alternative as most people aren't going to be able to place a sub in the middle of the room (I managed by cheating, I put my second sub under the sofa not quite but about the centre of the room).

Then since one sub is going to be SO much closer to your prime listening position, it needs to be set lower in output than the other further away. Get a analogue sound level meter from Radio Shack, or eBay (they are still available!). Play a 200 Hz tone and adjust the further sub to register at your main listening position say (70dB) with the nearer one turned down. Then raise the level of the second sub so the meter registers an additional 3dB.

The next 2 steps are just as important.

Firstly set your AVRs mains to sub crossover at 200 Hz and play a music track with repeating kick drum and adjust the Speaker Distance setting on your AVR so the sound of the kick drum is a single punch and not two one slightly before or after the other. You might find that the "distance" number does not match the actual distance of any of your subs. That does not matter. What's most important is that you hear one sound and not two.

Lastly set your crossovers to no higher than 80 Hz. 60 Hz is okay too but any lower and you are asking the main loudspeakers to do more work than they need to, reducing your systems maximum loudness.

You will now no longer have places in your room (and even outside) where there is too much or too little bass. Your neighbours will complain less!

Hope this helps.

Good luck!

Cheers,
skris88

Last edited by skris88; 01-07-15 at 06:24 AM. Reason: Errors corrected
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post #9 of 19 Old 01-12-15, 03:04 PM Thread Starter
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Re: Calibrating Two Different Subs - Need Help!

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skris88 wrote: View Post
Their timing might be different but that should be of less concern. The idea is that these 2 subs SHOULD sort of cancel each other out. But not in a bad way. One may have peaks and troughs in some frequencies, and the other in different frequencies. In that way, they actually fill in the other sub's troughs or remove those peaks. So that is a Good Thing.

The best way to hear the benefit between one and two subs is the sound of the bass "outside" the room. In some places there may be too much bass, and in others too little. This will be most easily evident in Open Plan homes. As you walk from one end to the other of the space you'll hear the bass get louder or softer if there is one sub. If you have two you'll find the bass will be much more even throughout the space. What multiple subs do is reduce the comb effect caused by the room's natural nodes by evening them out. Flat bass with no peaks to annoy the neighbours, or suck-outs to annoy you.

But it is important to get the settings right. Firstly the subs themselves. If you can (or dare to!) put one in the corner and the other in the middle as these positions are the 'best' and 'worst' for bass peaks and cancellations caused by the room nodes. Against the wall but in the middle between the corners is a good alternative as most people aren't going to be able to place a sub in the middle of the room (I managed by cheating, I put my second sub under the sofa not quite but about the centre of the room).

Then since one sub is going to be SO much closer to your prime listening position, it needs to be set lower in output than the other further away. Get a analogue sound level meter from Radio Shack, or eBay (they are still available!). Play a 200 Hz tone and adjust the further sub to register at your main listening position say (70dB) with the nearer one turned down. Then raise the level of the second sub so the meter registers an additional 3dB.

The next 2 steps are just as important.

Firstly set your AVRs mains to sub crossover at 200 Hz and play a music track with repeating kick drum and adjust the Speaker Distance setting on your AVR so the sound of the kick drum is a single punch and not two one slightly before or after the other. You might find that the "distance" number does not match the actual distance of any of your subs. That does not matter. What's most important is that you hear one sound and not two.

Lastly set your crossovers to no higher than 80 Hz. 60 Hz is okay too but any lower and you are asking the main loudspeakers to do more work than they need to, reducing your systems maximum loudness.

You will now no longer have places in your room (and even outside) where there is too much or too little bass. Your neighbours will complain less!

Hope this helps.

Good luck!

Cheers,
skris88
Wow, good stuff, thanks! I do have a good SPL meter and will try this in my space to see how it works. Any suggestions on a good sound track for this test? I have a small music collection, mostly from the 80's and 90's. Is there a particular CD I should use (or buy) for this and future sound tests?
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post #10 of 19 Old 01-12-15, 06:05 PM
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Re: Calibrating Two Different Subs - Need Help!

Try The Black Eyed Peas' Boom Boom Pow

Enjoy!
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