Sub calibration for dummy...me!

Originally Posted by Gooddoc

If you want to use an SPL meter then you need test tones; however, with dual subs it is a herculean project to do it. You've invested a lot of money in your system, spend another 1-3 hundred and buy measuring gear to properly place your dual subs. Using measuring gear will give you the greatest bang-for-the-buck improvement in SQ by far.

Using the tones in your AVR is basically a waste of time and I would just use Audyssey and forget about it if that is the route you're going to take. The 75 dB is at your primary listening position and is simply related to setting the sub level to reference when AVR volume is at 0 dB (relative scale)

Originally Posted by Mpray1983

The radio shack meter is off a little bit. You can actually download a calibration correction table is actually available to download. It gives you the correction at different frequencies. At 75 db it's only a few db off but most prefer to run a few db hot on the LFE channel as well. Its all personal preference. You will also need to change the distance settings as well. One easy way to accomplish this is to run audyssey and then just switch it off if you prefer not to use it and it will still leave the measurements intact. Is there any other particular reason you are against audyssey besides eD telling you not to?

Originally Posted by craig john

Your subs have speaker level connections. You are NOT using them, correct? Are your subs "daisy chained" or Y'd together?


If you have 2 subs, and they are both up front, between the speakers, then here's what you want to do:

1. Turn off one of the subs. Set the SPL meter at the listening position, pointed straight up.

2. Play the receiver's subwoofer test tone. Use the sub's Volume Control to set the level to 72 dB. The SPL meter will jump around some. Set it so the average is 72 dB.

3. Turn off that sub and turn on the other sub. Repeat Step 2. (Your subs are now "level-matched" at the listening position. Check that both subs are set to very close to the same Volumes. They should be, but if they are not, we may want to try "gain-matching." Let me know if they are not close to the same Volumes and I will tell you how to gain-match.)

4. Turn on both subs. When combined, they will sum and add 3 dB to the output, equaling 75 dB.

5. Run Audyssey according to The Guide:
http://www.avsforum.com/avs-vb/showt...5#post14456895

Come back and post the speaker/subwoofer levels, distances and crossovers. We'll help you with post-Audyssey optimization, if necessary.


It's best to use the receiver's subwoofer trim control. It's much more precise, and it adjusts both subs at the same time.

Craig

Originally Posted by warpdrive

The reason you want to set the sub to 75 (or duals to 72dB each) BEFORE calibration is because the receiver will try to fine tune the levels to 75 when it does the calibration. By doing it yourself first, you are getting it in the ballpark already. Then when the receiver calculates the final setting, it doesn't have to correct for the levels much (or at all). It does not have to boost or cut the sub output signal because it already is set correctly. You basically want the receiver to not have to make major adjustments because that might cause the auto-on feature of your sub not to activate correctly (because the receiver had to reduce the final ouput signal too much) or the sub's amp may chop off the signal (if the receiver has to boost the output too much)

Originally Posted by warpdrive

Think of all the gain knobs and settings on your receiver and sub as a bunch of adjustments that need to all sum together so that the receiver is putting out exactly 75dB at your listening position with the test tone.

If your receiver's sub gain is -13.5, that is WAY too low. That means you turned up the sub's knob too high. You want to end up with a receiver sub gain setting near 0dB, so you want to back down the sub volume below 12 o clock. If you run the test tone and your meter reads 72dB for each sub with the receiver's sub setting at 0 dB, then you've established the proper baseline settings for both subs at your listening position.

Then after....you have to run Audyssey with both subs turned on. Audyssey WILL override all the settings in its calibration, but because you've established the proper baseline, you'll see that it (probably) won't alter the receiver gains that much. Because Audyssey is way more accurate when it measures the sound, you may find it wants to alter your gain from what you set it to manually. Any deviation from 0dB should be expected and acceptable. These are the final settings you should keep.

If you still find that Audyssey wants to do a big correction of say more than 6dB difference something is still off. You should probably need to adjust the sub volume controls again (use the meter to make sure both subs read the same individually at your listening position) and then run Audyssey again.

Basically, the role of the meter is to:
- get the subs reading about equal
- provide a rough guide to where to set the sub's volume knob (you want 72dB for each sub)

then you let Audyssey do its work. It will use its massive computational power to adjust and EQ all the channels better than you can do so yourself.