Two Subs...Gain Matching vs Level Matching - Page 4

If the ports are a similar distance from the middle of the driver, I would position the SPL meter at the middle of the driver, about 3" away. The ports will than have the same "respective" contribution for each sub.

Then set the SPL to read 10 to 15 dB higher than what you want it to read when the sub is back in it's placement. I set each of mine to 85 dB on the nearfield measurement. Then, when they're back in their respective placements, they'll each read 68 to 73 dB at the LP.

Craig

Thanks for the advice Craig. Sorry for beating a dead horse with this level/gain debate. I am not able to give one sub more reinforcement as it's position is fixed; however, I was able to take away reinforcement from the other. Even with taking that sub out the corner, it still has significant room gain.

I agree that in my specific situation, I think that level matching may yield the best output from my dual subs.

There will be a trade-off between FR improvements and driving the higher-set sub close to it's limits. All you can do is experiment with different gain settings to find the best compromise. If setting one sub much higher than the other yields the best FR optimization, then I would use that and limit the max output of the system.

I know you've spent an enormous amount of time optimizing your dual sub system, and you've had lots of frustrations along the way. I totally respect the effort, persistence and focus you've put into the effort.

Good luck!

Craig

Great question (was going to ask) and answer. Thanks.

Thank you Craig.

Craig, do you have Danley DTS-10 subs?

Ummmm.... no. I have 3 Seaton Sound Submersives, (gain-matched of course!)

Craig

Only champions level-match their subwoofers. The older fogies gain-match their subwoofers and will tell you that you will achieve equal workload and lower distortion but the levels will be all over the place. If the levels are all over the place then sound quality will be highly compromised. You heard it here first folks.

If you want a messier response, gain-match the hell out of your subwoofers. If you want a prettier response that sounds better, then level-match your subwoofers. It's the champions way and it's that simple. I have spoken and so shall it be.

QED.

I aggree with gonetan. Gain mathing only resolts in messyer responces. Level match all da way !!!!!!!!!!! All my systams sound worse wid gain mathing. GAIN MATHING IS USLESS !!

Hi Craig, thanks for the great info with this topic. But do have few questions.

1) is there any benefit to perform gain match steps with just one sub setup?

2) how to measure with a down firing sub?

3) should I lay sub on its side and measure with mic about 3" away from middle of the driver?

I guess that seemed like a question out of the dark...

I was reading about the Danley and a 'Craig' was touting the virtues of the box, though it might be you.

For my system I am strongly considering the construction of 2 Tuba HT subs (I already have 2 Eminence LAB 12 drivers). Right now I have a pair of Klipschorns, their 15" drivers are good, but not designed or configured for taking on the LFE tracks of modern movies so I plan to retire them to the living room for 'music only' duties and build a new front sound system for the home theater, the Tuba HT's will part of that system.

With just one sub there is nothing to "match". All you can do is calibrate the output of the single sub to the output of the speakers.


If you had 2, it's really only important that you measure them both the same way.


With just 1, I wouldn't bother with a nearfield measurement. Just calibrate to the speakers it at the LP.

Craig

Craig, thanks for clarifying my thoughts.

You're welcome. What you don't want is to use a very low gain level on the subwoofer otherwise you'll reach gain compression overload (GCO) which is the equivalent of dynamic compression. When you level-match (which is what you are supposed to do regardless), turn the gain to at least 40%, readjust your level trim in your AVR to achieve the desired SPL when using the SPL meter.

As mentioned earlier in the thread, I had great success with gain matching my dual subs. However, there is now a dilemma. I just recently got a new receiver with Audyssey XT32 (Onkyo 3008) and am debating if I want to leave my subs with the Y-cable into one sub input. Or if I should use separate cables and take advantage of XT32's dual sub calibration. If I understand correctly, XT32 does level matching, so I'd lose the benefit of gain matching.

Correct, Audyssey recommends level matching for their sub calibration; however, that is when using a y-split to multiple subs.

It may actually be best for you to gain match your subs than run Audyssey. On those 1/2/3***7/8 model Onkyos (and other higher end receivers with MultEQ-XT and XT32), Audyssey individually applies distance, level and calibration. Of course you have the creme' de la creme' with XT32!

**Actually, it would be great if you could report back to us with your results. After you gain match your subs and run Audyssey MultEQ XT32, I would be curious what trim level Audyssey will assign to your subs. FYI, this doesn't prove that one method (level vs gain) is better than the other.

To run multi subs in a room.

1) Place all subs in the location where they are going to live.
2) Mic from listening position
3) Run manual test tone from your pre or receiver.
4) Get all subs to same SPL( I use 75db as my reference) using the gain adjustment on each sub not the line level pre amp gain. Leave this at 0db or reference point.
5) Once all subs are outputting equal SPL to listening position ,now you can run a MCACC or Audyssey type Calibration system.

This also applies to owners of Powered tower speakers for theater setup.

There is no benefit of "gain matching each sub in the middle of the room. Dynamic range is the same if the sub is running 1/4 , 1/2 or wide open gain. It all gets triggered off of Line level signal. I talked to a few Engineers at respectable companies about this as I use to be worries about gain matching and dynamic range limitations. I was told my all of them this does not matter. Also the line level gain output usually from -10db to +10db will also not restrict Dynamic range or headroom if you will. I also thought this was a issue if lets say your center channel was running at +7db to make 75db and your rear lets say left was at -4 due to room acoustics playing a roll in over all output.

We all worry about things at are actually trivial but getting all the speakers in your system at the listening position the same SPL is Key. This will allow you to experience the recording the way it was meant to be. Many want to juice "LFE " or the "rear surround speaker channels" to get a more personally experience. This is fine but know you are now out of balance. Years ago this was an issue in the field as many of my customers would complain that they spent good money on expensive speakers for the rear channels(5.1 setup) and they don't sound like they are on all the time or not loud enough at their seating/ listening position. An education always proved the overall listening experience was the highest when everything was in balance.

Good luck setting up your subs. Take your time and don't get frustrated , it's not exactly easy thing to do.

I currently have it setup with the two subs gain matched and connected to the Sub 1 input on the 3008 with a y-cable. I haven't really had time for much testing.

If I were to leave the subs gain matched, then connect them separately to the 3008's sub 1 and sub 2 inputs, I'd guess it would just bump up the sub channel trim on the sub where I have the sub's gain knob set lower to facilitate gain matching. In other words, it would probably just adjust the trims as needed to accomplish level matching.

Hi Chad,

The benefit of using the dual sub outputs is that you can set different "Distance" settings for each sub. This provides better time alignment for the dual subs. However, this technique uses level-matching after the time alignment. If your subs are placed at significantly different distances to the LP, or if they have significantly different room reinforcement, (i.e., corner placement vs. mid wall placement, etc.), you could end up with significantly different level settings, causing all the problems I have previously described with level-matching.

I think you need to evaluate whether the improved "timing" of dual subs connected to dual sub outputs is more beneficial than gain-matching of dual subs connected to a single sub output. These differences will be subtle, and will be difficult to quantitate by ear. IMO, you'll need some type of measurement equipment to be able to visualize the differences between the two setups.

What measurement capability do you have?

Craig

Thanks for the reply. All I have is an older RS analog SPL meter.

With the subs gain matched and hooked into the single sub input with a y-cable, Audyssey set the sub distance at 10.5ft.

Last night I re-adjusted the subs to level matching and hooked one sub into the sub1 input and the other into the sub2 input, then I re-ran Audyssey. It calculated each sub's distance as..........10.5ft. I am running my subs in the front of the room in this order left to right: left main, sub, center, sub, right main. So in my setup the ability to set different delay settings is nil.

I need to spend more time with it, but it did sound like the one sub was strained a little bit with the new (level matched) configuration.

Something occurred to me. All I need to do is gain match the subs, then measure them separately and make note of the levels. Then switching between level and gain matching can be done in the comfort of the seating position with the Onkyo's trim levels using the remote control. However, I wonder if changing the sub levels in relation to each other will wreak havoc on Audyssey's EQ filtering, Dynamic EQ, etc.

Since your subs are equidistant to the primary LP, there is no benefit to running them on 2 separate outputs, especially since Audyssey found their distances the same. If there is some disparity in the gain settings with level-matching, and one of the subs sounds distressed before the other, then gain-matching makes more sense. However, if you go back to gain-matching, you'll want to re-run Audyssey.


Changing the trims is different than gain-matching. Changing the trims changes the input signal. This will change the level, but it won't change the gain structure of the amp. If you want to gain match, the only way to accomplish this is by setting the gains on the amps to the same gain setting, as described earlier in the thread.

Changing the relative trim levels will impact the Audyssey EQ filtering and DEQ. If you want to change the trims, they should both be changed by the same amount. However, then your subs will no longer be properly calibrated to the speakers.

If you change ALL the trims of all the speakers and subs by the same amount, you will still be "calibrated", but you'll screw up "Reference Level" and that will screw up DEQ.

Bottom line, I don't recommend adjusting the trims after running Audyssey, especially if the only measurement capability you have is an SPL meter.

Craig

So I've read this thread 4 times hoping to figure it out 100%, but still have quesitons.

1) I have TWO identical subs.
2) I have a Onkyo 809 that has 2 sub outs (internally I think it is just a fancy Y)
3) The subs will be in the front of the room for the firest and then in the rear corner for the second.
4) I will set both gains individually at 80 db at the same location.
5) I will move to final location, run audessy and the FIRST step is to record the SUB(s) output at 75.

So here is where I am confused. The MIC is now in the primary listening area...closer to the corner sub. The mic is hearing output from both subs and it is reading 85 DB. I assume I lower BOTH SUBS TOGETHER to get the matched level.

For example to get 80DB for the subs, I have my setting (digatal) on the sub at -20.
In running audessy I reduce both to -26 in order to get 75DB?

Am I understanding this correctly ?

I second this.....

I just bought two new subs. Same model. I have the 809 as well. I am debating whether to have both subs along front wall (ruins asthetics for wife) or putting one in front left corner and back right corner. Distances would be off from mlp, with back corner sub being 2 or so feet closer.

1) what do you guys suggest?
2) I want to run audyssey, but plan to gain match both prior in center of room prior to final placement. This still the best approach?

don't have spl meter, so planning to just use test tone from initial audyssey setup

Thanks

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Sorry, I didn't see this when it was posted. Yes, lower both subs identically and you will still be gain-matched.

Yes, gain-matching as described in this thread previously is still, (IMO), the best approach.

Craig

after gain matching and placing in final position, what happens when initially running audyssey if mic records higher then 75?

Should I shoot for a higher spl to takeb into account the distance from the center of room to my mlp, as described earlier in this thread?

Thanks

It would be VERY important to know this (whether it is simply 2 duplicate sub outs or if they are treated separately and individually). What version of Audyssey?





Use the AVR's sub channel level trim(s) to lower the subs' combined output in unison so that the subs remain gain matched. If the 2 sub outs on the AVR are simply duplicates of one another, Audyssey should do this properly. If there are two separate sub level trim settings, and you are doing this manually, then you should lower them both the EXACT same amount until you get to the combined level to where you want it. If you change the sub's individual gain settings at the subs, they will very most likely no longer be truly gain matched. If doing this results in a sub channel level trim value that you think is too low, you will need to gain match the subs to a little bit higher level and start over.

But, again, it would be very important to know exactly how Audyssey treats the two sub outs, here. When you run Audyssey, does it adjust each sub's level individually or not?



How are you going to gain match them using this technique without an SPL meter?

If this is really your plan, then you should just set each sub's master volume to the exact same setting. This is probably as close to gain matched as you will get without an SPL meter.

They both have the Onkyo 809 which has XT. In those models with XT and dual sub outs, they are just an internal Y connection. Audyssey "sees" them as one sub. It does *not* set different levels and distances for each sub. Therefore, if they gain-match the subs, they will remain gain-matched after Audyssey has its' way with them.

Craig

You need to get an SPL and follow the suggestions in Post #5 of this thread.

Once you've gain-matched them, if they still read higher than 75 dB at the LP before running Audyssey, then just turn each sub down an exactly equal amount. You'll still be gain-matched, and Audyssey will set the subwoofer trim in the appropriate range.

Craig

Yep, I ended up looking it up. I actually edited my initial post, which didn't address the possibility that they were treated separately, and added all those caveats regarding it after realizing that it might be a possibility. Then I looked it up. Should have left it alone. I can edit it again.