Two Subs...Gain Matching vs Level Matching

I have never gain matched my sub's, but I dont think 3.5 db is anything to worry about. Someone who knows more may chime in. I only level match my subs and If one poops out sooner I just turn it down a notch

Greg, as Haskin has said, I don't think the 3.5db is that noticeable. Personally, I am a fan of level matching identical dual subs, especially if you are using a calibration tool (such as Audyssey, Anti-mode) and have one LFE out signal Y-split to each sub. If you find that one sub is reaching its max with level matching, I would than use gain matching.

OTOH, with non-identical subs, GAIN matching the subs may help prevent the lesser sub from potentially maxing out (which would limit your sub set-up).

If you are crossing 80hz or below. It should be nearly impossible to notice one sub is 3dbs lower than the other.

I am a proponent of gain-matching. I have 3 Submersives, asymmetrically placed around my room. I want them all to drive the room with same energy, no matter what the relative SPL's are at any one listening position. This ensures they all have the same headroom, and they are all contributing equally to the sound. I don't hear any directionality from any of the subs anywhere in the room, even if I stand or sit very close to one of them.

To gain-match identical subs, the most rigorous method is to move each sub to the middle of the room, place a mic very close to the driver, and measure the SPL. Then move each of the other subs to the exact same position with the mic exactly the same distance away, and set the level to the same SPL as the first one. I place tape on the floor around the first sub, so I can ensure the subsequent subs are located in the exact same place. I don't move the mic between measurements. This works for identical subs, and the level knobs should be at the exact same point, assuming the amps are consistent from unit to unit. It also works for different subs, but then you should expect different settings on the amps.

Mark Seaton was the one who suggested this method to me, and if it's good enough for him, it's good enough for me.

Craig

Gain matching for me.

I was at a friends house tonight and he has 2 small, 12" sealed subs subs. One was placed in the left corner, and one was placed on the right but in the middle of the front wall. (The front wall is much wider than the area were the AV system is, so the the right of the right speaker is mid-front wall.) The two subs were obviously receiving significantly different room reinforcement. We initially tried level-matching. We set both subs so their levels matched at the primary LP. This yield about an 8 dB higher gain setting for the mid-wall sub. We watched the Star Wars opening scene. Immediately we realized the mid-wall sub was distorting badly and we had to turn down the overall level to compensate.

Next, we tried gain-matching. This allowed about a 3 to 4 dB increase in *system* level over the level-matched system, while retaining excellent sound quality for the entire system. This, yet again, reconfirmed my belief in the gain-matching technique.

Craig

Please ignore my ignorance but what is gain matching?

See Post #5 above.

Craig,

I gain matched (using the Anti Mode) my quad Empires a couple of days ago. I have two under the TV firing to the front (10 ft to the seat) and two to the rear of the seat (6 ft from the seat), firing forward. Big improvement over level matching with bass clairity and mid bass slam sounding the best that I have ever heard in my room. Audio thru the system has improved greatly also with gain matching of subs. So much detail that I am watching clips all over again just to see what I have been missing. Finally, just want to say . . . gain match your sub(s) and don't worry about the spl at the seat as the bass will be there.

Bill

I have a quick question and there are several people in this thread that I respect when it comes to subwoofer info. I've changed from having my dual Epik Sentinels on opposite sides of the room, which sounded great, to stacking them in a corner due to wife's request.

I'm splitting with a Y to both, so I don't have to run dual sub cables, and have a question regarding calibration. I'm using the Audyssey on my Onkyo 707 and I'm wondering if I should just hook them both up and calibrate like normal or if I need to do something different? At this point in time I don't have an SPL meter and am relying on the receiver.

If they're co-located, (stacked), they should be gain-matched. If you don't have an SPL meter, your only option is to set the amplifiers to the same volume/level setting. Assuming the amps have the same gain structure, this *should* be gain-matched. However, you will now have at least 6 dB more output from the corner-loaded, co-located subs, so you'll need to use the receiver's auto-calibrate to calibrate the combined levels. If Audyssey sets them to the negative limit of it's range, you'll need to turn each sub down by the same amount and re-run Audyssey until you get the levels within the trim range of the sub channel.

Craig

Craig,
What if you have dis-similar subs....at unequal distances to lp? When I gain matched in this scenario, one sub was over powering the other.

Thank you very much! Pardon my ignorance but I thought co-locating and corner loading was to achieve the 6db increase? If you match the volume settings on the subs, auto-calibrate afterwards and bring the 2 subs in line with Audyssey's parameters than wouldn't having just 1 sub corner loaded suffice or be the same thing? Or is this simply for gaining more headroom?

I'll be trying this later today. I'm also getting an SPL meter in the very near future.

That helped a lot! Prior to this week I had my subs separate but the wifey wants to utilize more space in the living room now. Between my job and a 9 month pregnant wife I don't have as much time as I'd like to research and learn about everything I'm interested in. Great explanation and it's appreciated!

The only thing that looks odd is going from BJC subwoofer cable to the Radio Shack splitter, much thicker cable from BJC.

I dialed both Sentinels down to 3 o'clock on their gain setting and ran Audyssey. It came back with -3.5 so I bumped it up 4db to get some heavy hitting bass. Thanks a bunch for the help!

Gain setting dialed in on a sub at 3 o'clock is pretty high. You mean 9 don't you?

Yep I was leaning over the top of them at the time, whoops! I used to have them both at about 11 when they were on opposite sides of my couch but co-located makes a huge difference. Gonna fire up a good bass movie here shortly to test out the new set up.

Yes, and that was what I was trying to say. Re-reading what I wrote, I guess you thought I was saying the gain-matching was what gave the 6 dB increase? Sorry if I wasn't clear. Co-locating the 2 subs will provide a roughly 3 dB increase. Corner loading will provide an additional 3 to 6 dB. This additional reinforcement will allow you to turn the levels of each sub down. The benefit is that each sub will be playing back at a lower level with lower distortion and in a more linear range of driver excursion. The downside of co-locating and corner loading is that you lose the FR flattening of the separated, midwall locations. You'll be giving Audyssey a more ragged FR to work with. Audyssey has a limited capability to flatten the FR. The flatter it is to start with, the better job it can do achieving it's "target curve".


Not sure I understand this question, but what do you mean by: "...bring the 2 subs in line with Audyssey's parameters..."? Audyssey will "see" the dual, co-located subs as one sub and it will provide one EQ filter set for the combined response of both subs. It will also set the Distance for the combined subs as well as the levels. I don't know what else one would "bring in line".


Yes, that is the primary benefit of co-locating/corner-loading.


Good. An SPL meter is the most basic tool for an HT enthusiast. It's like a hammer for a carpenter.

Craig

Hi Larry,

Bass below about 80 Hz is non-directional. Most humans can't hear the direction of origin of bass sounds, (below about 80 Hz.) Therefore, if you hear directionality from one of the subs, (which is what I presume you mean by one sub "overpowering" the other), then there might be some higher frequencies being played back by the closer sub. This could be caused by a crossover higher than 80 Hz, or by harmonic distortion.

Let me ask you this: If you playback using just the closer sub, can you tell the direction of origin of the sounds coming from that sub? Can you hear it as a localizable source of sound? If not, I would be surprised if you can find it as a localizable sound source with two subs running. If so, there is something going on with your sub(s) that is causing the directionality. I would spend some time figuring that piece out first. What crossover frequency are you using? Can you look at the response above 80 Hz for just the subs?

Craig

Great job, and great summary Redskin!! May I ask if your receiver applied any calibrations to the subs...and if so, which receiver?

It does set standing wave and sub trim for the reciever.

I have such an unbelievabley bad room...only one true corner and over 6500^ft. I don't care where the xover is..40, 60, or 80....or what sub I use, I can tell where the sub is in the room..you can almost point to it. I've had the same problem with 3 different subs, the 2 I have now, and the 1 sealed I had before these. I dont' think it's because I have super human ears either. It's the floor. . It's a 60 year old wood floor. It's great when you are watching canyon walls coming down, or an A6 fly-over, but I can always tell where the low end is eminating from. Doesn't matter if it's low volume or high....
The FLATEST response I can achive in my room (this is after moving 550 lbs of subs around the room) is when one sub is in the front right corner and the other sub is in the rear right corner. Nice flat graph via sms-1.
I HATED IT. It felt like the room was lopsided. It was like I had a cotton in my left ear...everything was coming from the right side of the room. When I gain matched the problem became worse.
What I ended up doing was moving the right rear sub to the left rear corner (if you can all it a corner with that damm opening) and that balanced the room. I can't tell where low stuff is coming. I also think the extra bracing in the corners of the room help. NATURALLY, it caused a 4-6 db suck out from 60 to 80 hz. I don't care....to these ears it sounds and feels pretty good.
I don't remember if I gain matched with the subs in current position. I'll try it.
Never mind moving the subs around the room...I've changed everything in this room 4 times. I'm done with it. I'm tired of fighting with it. Like I wrote above, it sounds pretty good to me..but what do I know. It's not like I am at Craig's or Bosso's level.

I've got two Epik Sentinels, one mid wall left, front firing, the second corner right, firing into the side wall. They are "Y" connected and level matched, with the corner sub set much lower than the left. Audyssey sets them at -3.5. If I want to gain match, where do I place my SPL meter? Or do I just move the right sub out into the room and meter it at one meter?

from a very knowledgeable person