Originally Posted by adam2434
Using the MultEQ app and a Marantz AV7704 pre/pro, calibrated sub levels are -7.5 dB for Sub 1 and -8.0 for Sub 2.
So far (only had the 7704 for a week), I prefer to boost both subs 7 dB for music, so the resulting levels are -0.5 dB and -1.0 dB, so just barely into the negative. This is with DEQ off. When listening to music at "loud" levels briefly, the MV was at -7.
I would certainly expect/hope that a dedicated pre/pro could cleanly drive the sub outputs at those trim levels, even at high/reference volumes.
However, I've read that it's good to keep sub trims at -5 dB or lower, as a rule of thumb. However, not clear on the basis for this rule of thumb. Is it based on measured sub output distortion on some specific AVR models?
Ultimately, is it worth it to increase gain on the subs and rerun the calibration so that trims are -5 dB or less after boosting to the preferred level?
If so, I guess it would be best to increase both subs to the same level at the MLP using a SPL meter prior to rerunning the calibration.
Jerry's advice to be able to measure your frequency response, and to be able to test for indications of distortion or compression, is always good advice.
But, the simple fact is that most people are never going to do that. So, let me try to answer the questions you asked.
There are two reasons why it can be advisable to keep the AVR trims a little lower than you currently have them. First, clipping can sometimes occur with trim levels above about -5 or so. That is especially true where master volumes are at -10 or higher. Second, some subwoofers can't achieve their max output levels unless gain levels are fairly high.
I have seen that specifically apply to some SVS and PSA subs, but I can't tell you if it also applies to the Outlaw subs listed in your signature. It's a good general rule to follow for someone adding strong subwoofer boosts and/or listening at high volume levels. And, you seem to be doing both.
In any event, it is a pretty simple precaution to take, but you don't have to rerun Audyssey to do it. Just lower the AVR trim levels by 4.5db and 4db respectively. Then, you can raise the gain levels symmetrically, to add back about as much bass as you were listening to before. You probably added volume by ear before; you are just using your gain levels to do it now. And, you are trying to add the same amount if you can. Some people mark their starting points, on an analogue gain dial, with tape to facilitate that process.
You need to understand that your AVP isn't the real factor in driving your subwoofers. It simply needs to supply sufficient voltage to tell the subwoofers own internal amplifiers what to do. The subwoofer amplifiers need to do the real work, and some of them require higher gain levels in order to achieve max output, as noted above.
The ultimate factor in determining your subwoofers' ability to play both loudly and cleanly is the combination of subwoofer boost (through whatever combination of gain and trim you use) and master volume. It is important to recognize that both your subwoofer boost, and your master volume, put demands on your subs. At some point, you will simply run out of headroom. But, observing good gain/trim protocols can potentially help, up to the point at which you do run out.