# Calibrating Two Different Subs - Need Help!



## Philm63 (Jan 1, 2015)

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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## Tom Riddle (Aug 25, 2013)

Philm63 said:


> 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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## Philm63 (Jan 1, 2015)

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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## Tom Riddle (Aug 25, 2013)

Philm63 said:


> 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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## willis7469 (Jan 31, 2014)

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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## willis7469 (Jan 31, 2014)

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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## Ayreonaut (Apr 26, 2006)

Co locate them and the outputs will sum.


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## skris88 (Mar 7, 2011)

Philm63 said:


> 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


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## Philm63 (Jan 1, 2015)

skris88 said:


> 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.
> 
> ...


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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## skris88 (Mar 7, 2011)

Try *The Black Eyed Peas*' _Boom Boom Pow_

Enjoy!


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## willis7469 (Jan 31, 2014)

Given what's in your collection, I'd try Stone Temple Pilots "core". The bass guitar and kick drum are mixed, almost as one, and the bass player(especially later in the album) is fairly busy and keeps it interesting. Fun to listen to. My LFE is set at -9, and I trim up to -2 for music. Trim to taste!


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## skris88 (Mar 7, 2011)

willis7469 said:


> Given what's in your collection, I'd try Stone Temple Pilots "core". The bass guitar and kick drum are mixed, almost as one, and the bass player(especially later in the album) is fairly busy and keeps it interesting. Fun to listen to. My LFE is set at -9, and I trim up to -2 for music. Trim to taste!


​
​​
Trim To Taste is an important truism.

Recordings of different decades go through different "fads" and tonal balances. Those of the 70s are slightly thin - no doubt to ensure styli stay in the vinyl groves and don't pop out on loud bass signals. Recordings these days have a lot more bass. So if you fine tune your system for one set of recordings it'll sound weak or fat on the other - don't blame your system!

I have a EQ setting on my system I can turn On at will, a 3db boost at 65Hz and a 2db cut at 2kHz which I use for some recordings from the 70s. I am happy to assume the producer and artists did NOT intend for me to have loudspeakers that were mirror flat in their response, while they used loudspeakers that were boomy during their final mix and so 'cut' the bass.

In the end, once you've got it fairly even in balance without sharp peaks or dips in the sweet spot and even around the listening area, just enjoy the music - that's what this is all about!


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## Philm63 (Jan 1, 2015)

skris88 said:


> ...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.


Question: My AVR has only one sub out, and I am using a splitter and two cables feeding my two subs. If I were to place one close to my listening position and leave one in the front-corner, they obviously would be at two different distances relative to the MLP. Adjusting the distance in my AVR would move them both simultaneously. 

Would it still be possible to achieve that "single sound" during this test by adjusting the distance on both subs such that one eventiually becomes 180 degrees out of phase relative to the MLP (I suppose this would depend on the distance between the subs, no?), then I could simply flip that sub's phase switch from 0 to 180 and be golden? Or am I not understanding yet just how the distance/phase relationship works?

I'm looking to the future, one where I have a Pre/Pro or AVR that'd allow setting distance on more than one sub, so I'm sure it would work then, but for now I may just be limited to moving the subs around until they just sound right. Let me know if my theory above has any validity.


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## skris88 (Mar 7, 2011)

Move 12 inches or approx 300mm and your phase reverses. It's true! So I don't bother with it. Phase becomes an issue with higher frequencies like 200Hz , but you shouldn't make your crossover higher then 80Hz anyway.

The key benefit of 2 subs is to use them to fill in the other sub's peaks and dips caused by room nodes in the position it's in. So it is critical both are NOT in mirror image locations of the other, it'll make the problem much worse, not less.


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## willis7469 (Jan 31, 2014)

In my situation, phase settings were critical to my in room response. I'm kind of stuck with my placement options(which is luckily where they're best), and that was the only way. I have 3subs in place currently, and I wouldn't have been successful in good response without phase selection. 
To your above skriss88, it is funny about different decades, and recording practices. Today for example, I started out with imagine dragons. Now I'm listening to Pink Floyd's The wall. Wow! Worlds apart, but not less impactful. Like you,(kind of) I used mcacc presets in my 1019 backup/bedroom receiver. Flat for movies, house curve preset for tunes!


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## skris88 (Mar 7, 2011)

willis7469 said:


> In my situation, phase settings were critical to my in room response. I'm kind of stuck with my placement options(which is luckily where they're best), and that was the only way. I have 3subs in place currently, and I wouldn't have been successful in good response without phase selection.
> To your above skriss88, it is funny about different decades, and recording practices. Today for example, I started out with imagine dragons. Now I'm listening to Pink Floyd's The wall. Wow! Worlds apart, but not less impactful. Like you,(kind of) I used mcacc presets in my 1019 backup/bedroom receiver. Flat for movies, house curve preset for tunes!


Pink Floyd's The Wall is one of 70s recordings that do NOT need to have their EQ changed. 

Creedence Clearwater Revival is a good example (IMHO) of recordings that need to be trimmed. 3dB up at 65Hz and 2db down at 2kHz might even be considered as not enough of a tweak! I suspect the producers had their "Loudness" setting On when they reviewed the trial mix. Loudness settings may work fine in theory, but need careful calibration of the input and output level settings - something almost no one can. (Luckily these days Loudness buttons have gone the way of the dodo, but - sadly - tone controls as well.)

Even Audyssey can be accused of this. Their Dynamic EQ is a horror, unless you're watching BluRay or DVD through HDMI as only these confirm to SMTPE calibration standards for level matching. CD Audio and CD rips are all over the place and are messed up by Dynamic EQ unless you calibrate your tracks.

Hey, don't misunderstand. I LOVE my Audyssey, and won't consider a new system or listen to my audio without it. You just have to be smart about it.


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## willis7469 (Jan 31, 2014)

skris88 said:


> Pink Floyd's The Wall is one of 70s recordings that do NOT need to have their EQ changed.


 I love the wall, and that I can hear the room. "Nobody's home" is in my head now. "I got nicotine stains on my fingers"....Part of what I dislike about modern recording is the 3db dynamic range. A most obvious example is Metallicas last. Death magnetic. From what I gathered, the engineers had the levels up well into clipping. It sounds terrible at any volume, inducing ear fatigue after about 2 measures. Some of the content is pretty good. Sad. Everyone's gotta be louder than the next guy.


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## skris88 (Mar 7, 2011)

willis7469 said:


> I love the wall, and that I can hear the room. "Nobody's home" is in my head now. "I got nicotine stains on my fingers"....Part of what I dislike about modern recording is the 3db dynamic range. A most obvious example is Metallicas last. Death magnetic. From what I gathered, the engineers had the levels up well into clipping. It sounds terrible at any volume, inducing ear fatigue after about 2 measures. Some of the content is pretty good. Sad. Everyone's gotta be louder than the next guy.


Yes, ironic that with 96db dynamic range available these days, recording engineers use only the top 5db these days. In the heyday of rock music, they had only 40db of dynamic range available before tape hiss or tape saturation crept in, but we got at least a 20db dynamic range in those recordings - real music!

I suspect the current vinyl fad is just as a result of the way new recordings are being compressed in dynamic range, and not because of any superiority of analogue over digital.


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## skris88 (Mar 7, 2011)

Was sitting next to one of my subs tonight with New Kids On The Block & Ne-Yo's "Single" playing. It's got a repeating kick drum right through the song. And I felt (not heard, I was leaning on it) that my sub was just ever so delayed from the mains. Opened my Audyssey settings, Speaker Distances and increased my sub distance by an extra 4 feet. Perfect. 

So that's another way to get the timing right between the mains and sub, by feel!

Cheers,
skris88


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