What most people don't realize is that the "0dB" volume setting on the receiver is supposedly where you will place your volume level if you are trying to listen to your movies and TV shows exactly as was intended by the content creators. "0dB" is "reference" volume, which is why, if you turn the volume down, it goes to a negative number (indicating that you are below reference volume).
That "reference" volume is supposed to be an average 85dB with 105dB peaks in the speakers and 115dB peaks in the subwoofers. When you play your receiver's "test tone" pink noise, you are supposed to set the volume knob to read 0dB and then use the channel trim controls to adjust the actual speaker output so that you get a reading of 85dB C-weighted on your SPL meter from each speaker (including the subwoofer) at the seating position. You should also note that many receivers actually only output a 75dB "test tone", in which case, you are meant to set the volume dial to "-10dB" and look for a 75dB C-weighted reading on your SPL meter.
Most people think they are "cranking" the volume if it is set anywhere close to "0dB". That is because most people just plug in their speakers and start listening, not realizing that today's receivers have WAY more power than people think. It is often the case that even if you turn the channel trim controls all the way down to their lowest setting, you will still get a louder reading than 85dB on your SPL meter if you run the "test tone" with the volume knob set to "0dB". In other words, people's rooms are smaller, the listening distance shorter, the speakers more efficient and the receiver more powerful than is actually intended by the "reference" volume!
Bottom line, there is nothing wrong with having your receiver's volume read "0dB". That is where it is supposed to be! And if you run the "test tone" at that volume setting and use your SPL meter with C-weighting, you should get a reading of 85dB at your seat. That's "reference".
Most people find an average 85dB SPL to be too loud. Most people prefer something around a 75dB average listening level (which is another reason why many receivers actually output a 75dB "test tone" rather than an 85dB "test tone"). But if you want to listen with the volume being exactly where the content creators intended: "0dB" on the dial and 85dB average SPL with 105dB peaks.
Audyssey generally does a pretty good job at matching each speaker's output to this "reference" standard. If you have trouble understanding dialogue, it's because you have crappy room acoustics (which many, many people do). Pull your seat away from the back wall and get some absorption in there! Clear that dialogue right up
If you are not noticing your surround speakers as much as you like, it's because you're not actually SUPPOSED to notice your surround speakers! They're actually supposed to be up high (about 3 feet above your seated height in a home theatre) and merely enveloping you and creating ambience. You are always supposed to have your attention drawn to the front, to the screen. Many people think they're supposed to get "whiz bang" sound effects coming from "the back". So they put monopole speakers at ear height and then crank up the surround channels! That's not really what it's supposed to sound like!
Now, the cross-over from speakers to subwoofer: that's something that Audyssey often doesn't nail. Audyssey seems to prefer to set the speakers as low as possible, which isn't the right idea.
What you are SUPPOSED to have are speakers that naturally have a -3dB point of 80Hz and a 12dB/octave (2nd order) roll off from there on down. EXTREMELY FEW SPEAKERS ACTUALLY HAVE THAT DESIGN.
Isntead, most speaker manufacturers try to make even their smallest speakers play as low as possible, or you have small "lifestyle" speakers that can't even reach down to 80Hz. It seems as though you mostly get speakers that either play lower or not low enough. Very few that actually stick to the -3dB at 80Hz, 12dB/octave roll off design.
In your receiver, the cross-over applies a 24dB/octave (4th order) roll off to the high end of your subwoofer (a low-pass filter), starting at 75Hz so that your subwoofer has a -3dB point of 80Hz on the high end. For the speakers that are set to "small" (which should be ALL of them, regardless of physical size or ability to play lower), your receiver applies a 12dB/octave roll off on the low end of the speakers (a high-pass filter), starting at 80Hz since the speakers are SUPPOSED to already have a -3dB point of 80Hz already!
The end result is a perfect 4th order Linkwitz-Riley crossover with a summed response between the speakers and subwoofers that is perfectly flat. The 2nd order high-pass filter applied by the receiver "cascades" with the supposed 2nd order natural roll off of the speakers to give them the same -3dB 80Hz point and 4th order roll off slope on their low end as the -3dB 80Hz point and 4th order roll off slope on the high end of your subwoofers.
But, like I said, extremely few speakers actually adhere to the design. Instead, they have -3dB points that could be anywhere - usually as low as the manufacturer can make them - and low end roll offs with slopes that are steeper than 12dB/octave - usually something closer to a 3rd or 4th order slope.
So that lovely crossover design gets all screwed up! Maybe the crossover frequency is set higher than the natural -3dB point of the speaker. That's mostly OK, but with only the receiver's 12dB/octave filter on the low end, the roll off is not steep enough and you end up with a "hump" in the mid-bass where the subwoofers are sloping off as they should, but the speakers' slopes are not steep enough so you're getting more summed output than is intended.
Or maybe the crossover is set at the speakers' natural -3dB point. That's fine for that one frequency, but below that, you have the too steep natural roll off the speakers cascading with the 12dB/ocatve slope applied by the receiver! Now you have too steep a slope on the bottom end of the speakers!
It all sounds worse in description than it actually is. When you actually listen to it, it can be hard to pick out by ear and most people like the extra mid-bass "bloom", which is why so many people mistakenly prefer tower speakers and think that they sound more "full". They're just playing lower with too shallow a roll off on the bottom end.
So the easiest solution is to just set all speakers to "small" with a cross-over of 80Hz in the receiver. Technically, you might have too shallow a roll off on the bottom end of you speakers and a bit of a mid-bass "hump" as a result, but it's no big deal in reality and, as I said, most people actually like it.
The bigger problem is if your speakers cannot reach down to 80Hz. Then you will have a "hole" in the summed response. The solution is just to set the crossover higher, but Audyssey will almost always catch that if it is the case. The Audyssey problem is setting the crossover too low because it tries to use the speakers' natural -3dB point. If Audyssey sets the crossover lower, just manually bump it back up to 80Hz.
The ultimate solution if your speakers play substantially lower than 80Hz is to use your own, separate high-pass filter. But you can only do that if you are using a separate power amp to power your speakers. You would actually want to set the crossover to 90Hz in the receiver and have a separate 12dB/octave high-pass filter, also set at 90Hz - such as the
one offered by HSU Research
In that setup, the signal coming out of your receiver or pre-amp's pre-outs would start to roll off at 90Hz with a 12dB/octave slope. That signal would feed into the separate high-pass filter, which would cascade an additional 12dB/octave slope, starting at 90Hz. The result is a 24dB/octave slope, starting at 90Hz, which results in a -3dB point at 80Hz. That cascaded signal gets fed into your separate amplifier, which then powers your speakers. With this setup, your speakers need to be able to play substantially lower than 80Hz with flat frequency response, otherwise, once again, the slope would end up too steep. If you speakers can play flat to 40Hz or so, then this becomes, strictly technically, the "ideal" crossover setup.
