Gain Matching vs. Level Matching

Being the world's dumbest man and by international decree, also holding the award for the most incompetent man alive, you won't be getting one smarter than you but my understanding, one independently gain matches, at the main listening positions, using the gain control of each subwoofer, each subwoofer turned on, one at a time, running pink noise through the AVR, with the AVR's levels (internal gain control) set to zero.

Then, after running the EQ programs, dial things in with the levels (AVR internal gain control) to taste with all subs simultaneously turned on as now you're dealing with a single combined subwoofer output.

As to the position of the sub (distance) from the main listening position, that's a time domain/phase issue as you want the sound waves to arrive at the MLP, at the same time so you're not getting cancellation; nulls.

Good luck.

No arguement here and you never fail to disappoint.

In a nutshell. move one sub to the center of the room. Using a spl meter place it a few inches from the sub and take a measurement adjusting the subs gain to 80db (the number I use). Turn the sub off and move out of the way. Then move the next sub into the same spot as the previous sub and measure at the same distance and to the same db lvl.
Now you're gain matched.

Measuring subs at your main seat is level matching.

Not really, because of the dominance of reflected versus direct radiation in what you're hearing. That makes the situation totally different than the other speakers, where what you primarily hear is direct radiation.

Well you guys beat me to it lol

lol, my post was directed at the "Being the world's dumbest man and by international decree, also holding the award for the most incompetent man alive" guy

It depends on the room size. The smaller the room the less of an issue it will be. In a full size theater I'd worry about it, but not in a home theater.

When I use the gain control to match levels, I'm gain matching the final levels. (I know you guys "THINK" I'm confused on this issue, but I'm not the confused one.)

I match at a measured 1m and then adjust at the MLP because of distant differences, the final SPL will be different as we both know, sound pressure levels fall off as the distance increases. The important point I wanted to share was to make sure the internal AVR gain control is set to zero during this gain matching and then run the EQ program.

Either which way, you had the privilege of the dumbest man in the world who holds international title to the most incompetent man in the world, trying to give you a helping hand.

I guess in a really large room near sub might reach you sooner than the farther sub if gain matched atleast on paper. Hard to say if you would tell by hearing.

It doesn't need to be compensated for with respect to the rear sounding louder. It may need to be compensated for in terms of achieving maximum smoothing of response at the LP. The only way to know that is by monitoring the room response while adjusting the volumes, to see the result on the RTA chart.

What does Newton have to say on the matter when one has unequal forces meeting each other. If it doesn't matter, then it doesn't matter where one is located when they measure the gain control set output of their subs.

If that's what you're doing, you already know the answer to your question.

I got you, I don't. My only concern is that the AVR sub trim is close to 0db which may mean I have to redo the gain matching process either up or down dependant on with the sub trim shows.
Is that what you want to know?

I think it's in your head (i'm not trying to be smartass). I can place one sub behind my couch and run it only and not be able to point it out. It wasn't what I was expecting the first time I tried it, I fully expected to tell.

+1. If you can locate it you've got directional frequencies in there that shouldn't be.

Hi Alan,

Can you try to describe the "localization" you're hearing? Localization is usually caused by hearing frequencies above about 80 to 100. It is manifested as hearing sounds "attached to" or "emanating from" the subwoofer. Often it's deep male voices where the fundamental frequency of the voice falls into that range. Darth Vader's voice comes to mind. If you are hearing his kind of directionality of specific sounds, that can usually be corrected with a lowering of the crossover. What crossover are you currently using? Also, what subs are you using? (Sorry, I forget.)

Another thing you can try is changing the closer subs' Distance setting. If your version of Audyssey has SubEQ2, you can set different Distances for one sub output than the other. The "Precedence Effect" states that directionality is determined by the first arriving sound, even if the later arriving sound is louder. Therefore, try adding a foot or 2 to the rear subs, effectively delaying them 10 or 20 ms. The front subs will arrive first and define the directionality and the rear subs will arrive later and add volume. However, be careful as these types of changes can also impact the FR. (Disclaimer: The Precedence Effect, or Haas Effect is usually defined with midrange frequencies. I'm not sure how low in frequency it applies, so don't take this as gospel.)

OTOH, if you a just "sensing" that all the bass is coming from behind, that is a different issue and it won't be corrected with a crossover change. Lowering the levels of the rear subs might help, but remember that you can run into issues with headroom if you use different trim settings or gain settings for one or more of the subs. Nonetheless, that may be a worthwhile tradeoff if it works.

I have 3 subs placed around my room at different distances to the LP, and I'm using a 100 Hz crossover on all my speakers. They're all 3 gain-matched, (using the AVS common definition of gain-matching.) I don't hear any one of my subs more prominently than any other sub. They all blend together and provide just one big bass response.

Craig

I'm wondering if it just isn't something nearby that's bringing attention to the sub. Say a sympathic vibration in the seat + the knowledge of where the sub is.

Localization frequencies are irrelevant in the subwoofer bandwidth. Run the sub hot and you'll "localize" it. Turn it up significantly higher than the mains and you'll pick it out of the crowd (of other speakers in the room) every time.

Here's one sub at 1M and an identical sub at 4M, gain matched. The inverse square law predicts a 12dB difference when doubling the distance twice (-6dB per doubling of distance), which is what the measurement confirms:



Anyone who can't hear one sub vs the other when there's a 12dB difference at his ears is too deaf to be posting in this thread. From 7 Hz down, it doesn't matter where you sit in this particular room (3500 cubes), but everywhere else across the BW... it matters.

Aside from the obvious crap shoot with the gross mismatch in arrival time (phase issues), calibrating the subs at the same neutral and irrelevant placement, then afterward placing them near field and far field simultaneously makes zero sense. If, as the OP has stated he has, you get a better FR at the LP with near field plus far field placement, then most certainly level match them at the LP.

I'm still a bit confused on the whole level vs gain matching thing. I have Audyssey XT32 and I've read posts from Chris of Audyssey that says it isn't necessary to gain match with XT32 and it also isn't necessary to get the subs volume as close to Odb as possible as long as they aren't maxed out.

I would expect the problem to be completely corrected when you get your new sub(s). It is difficult to use gain-matching properly with different subs. The technique works best when all the subs are identical.

Craig