Originally Posted by gerard1meehan
I was hoping that you folks could help me out again. I’ve adjusted some speaker positions and reran ARC. I had some very” boomy” bass and I adjusted my room gain. I found reducing it did the trick, but that honestly was through trial and error. Now I understand what room gain is, but what I do not understand is how it is addressed in the target window of ARC.
For instance the target window showed Room gain (db) 3.945749. So is ARC seeing that the room adds that gain and Arc reduces it, or does it say the room needs that gain and adds it? As of now I reduced it to 3 db and the boominess, seems to have been reduced. But I am very curious as to what ARC is doing, then my trial and error could be a bit more focused.
Next would be the Max EQ frequency, Arc offers 200-20,000 and defaults to 5,000. Why would one not use the max?
I am certain that these items have been addressed multiple times here but having a tough time tracking it down
Let's start with the 2nd question. ARC has a finite set of hardware resources to draw upon to do correction. There are more of those in the D2v than in the AVM 50 for example. The wider the frequency range you tell ARC to correct, the more spread out those resources get. Since the most important job for ARC to do is dealing with bass response for the room, and blending the bass output of the main speakers with the subwoofer, the default setting is to correct bass and only up through the mid-range -- 5 kHz.
The other problem is that getting accurate Measurements in treble is tough. Treble is a lot more directional, and so issues in Treble Measurement may be due to speaker pointing. Details of how the speakers are mounted can also be important, as well as odd things like room humidity.
And then each ARC mic has a calibration file which corrects its individual response. The ARC mic hears the entire hemisphere above the tip of the mic. So as you go up in frequency it also becomes important to correct for the polar response of the mic -- think of it as the mic's version of directionality -- its deviation from hearing that entire hemisphere equally. Depending on the geometry of mic vs. speaker placement in 3 dimensions, that correction may work more or less well.
Now, with some experience, you can learn to judge from the ARC Measurement curves how far up into the treble appears to be "good" data from the mic. For example, by comparing the different speakers, you can sometimes see uniform drop-off which means the mic isn't getting good data up there. So, of course, you don't want to try to "correct" that bad data.
Then, if you DO raise the Max EQ Frequency, you also need to be alert for problems appearing elsewhere in the ARC solution -- due to the reallocation of ARC's correction resources away from the bass region.
ARC for the D2v let's you experiment with higher values of Max EQ Frequency so you can learn for yourself how far you can extend the correction.
ARC for the new MRX AVRs does not. It has a set upper limit of 5 kHz, under the theory that MRX owners won't be doing that kind of experimentation. (If you need more correction resources in bass, you can still lower the Max EQ value.)
In my own D2v / 3D setup, I use a Max EQ Frequency of 12 kHz.
Room Gain is a "desirable" characteristic of good listening rooms. It manifests as a small boost in the bass frequencies, and you perceive it as the difference between a good listening room and a dead or anechoic room. Very large rooms, or rooms with extensive "bass treatment" have low Room Gain.
People who mix audio for movies assume the Room Gain of the listening room will be in the range 2-4dB. There's not really much consensus on this from people who mix audio for music, but the general result is that music mixes assume somewhat less Room Gain -- perhaps 1dB less.
The simple way to do an ARC-like solution would be to produce "flat" response down through the bass, but that would eliminate the Room Gain inherent in the listening room, and leave things sounding less natural.
Instead, ARC attempts to measure the inherent Room Gain of the listening room and preserve that as part of the ARC solution.
On the ARC charts, Room Gain manifests as the shallow hump in the Target curves down below, say 120Hz. If there were no Crossover processing, that hump's peak level would be flat all the way to the lowest frequencies. But instead the Crossover rolls that off.
If you look at the flat part of the ARC Target curves to the right of that -- in the mid-range frequencies -- what you've got is the Basic Volume Level of the Target ARC solution. The numeric value for Room Gain is simply the height of the peak of that Room Gain hump over the Basic Volume Level, in dB.
Now, Measuring the inherent Room Gain in the room is not easy. The inherent bass output of the speakers, and how they couple with the room, can produce dips or peaks in bass output not really related to Room Gain.
So ARC has some built in limits to the Room Gain it will select automatically for the ARC solution. It won't apply a negative Room Gain, as that has no useful physical meaning. And it won't apply a Room Gain above +4dB, as higher values are more likely to be the result of Measurement problems such as just mentioned.
For technical reasons of how the ARC math works, that 3.9...dB Room Gain value you quoted is how the +4dB limit shows up.
If you look at the Measured curves for your speakers, you will likely find they are hot in bass. This may be due either to the design of the speakers themselves, or due to how you have them physically positioned in the room -- bass resonances due to the way the speaker is coupling with the room's geometry. You can use the ARC Quick Measure Tool to see if modest repositioning of the speakers with respect to the walls reduces that unnaturally hot bass. Then redo your ARC setup.
In the ARC Targets window, you can adjust the Room Gain built into the solution -- including putting in a value MORE than +4dB if you want.
Lowering Room Gain because you think bass is overemphasized is a perfectly reasonable thing to do. But don't eliminate it entirely. Try +2dB or +3dB for example.