Originally Posted by Big Tex
Thanks for the help as ALWAYS. I actually ran two sweeps. One with both subs at phase 0 and one with the front sub at Phase 0 and the rear at Phase 180. I've included both sets of numbers to compare. Please let me know what you think. I'm anxious to see what you see. I really appreciate you pointing out that both subs at phase 0 is canceling each other out. I've confirmed it over the past hour just listening to them.
It's silly...I went and got the Video Essentials disc and used a SPL meter this afternoon. I couldn't see a difference in the SPL meter or I don't know how to properly use it. Probably the latter... Anyhow I then went for the "listening" test. I thought the subs sounded better when both were in Phase 0. This didn't make any sense logically but I thought it sounded better. In reality it didn't "sound" better, it was just louder.
Now fast forward. I've uploaded to the AVM the ARC calculations with all subs at phase 0 and it sound nasty! It sounded much better when I had manually tuned the back sub to phase 180. So in short you're RIGHT ON...I tried to use my untrained ears and goofed. Please tell me that the second set of charts (different sub phases) looks normal because everything else sounds GREAT. The 2nd set of charts is with the subs at different phases.
We've come a long way. I appreciate all your help!!! Now I just need to get these subs dialed in. I will say my optiomal sub configuration was when I ran ARC the other day with only one sub turned on, I then uploaded the ARC results into the AVM, turned on the 2nd sub and manually tuned the 2nd sub into the system thus bypassing it in ARC. I had the front sub at phase 0 and the back at phase 180. I am about to load the latest ARC results that had the subs in opposite phases so hopefully I'll get the same results I had from my install when the subs were working.
PS. What is room gain? What does it do? I'm about to add some now. Thanks!!!!
Of these two sets of charts, your combo with Phase shifted 180 has a somewhat better result for the subs. The other speakers still look the same of course.
One thing you may not be aware of is that the effect of the "Phase" control is usually limited to the region around the crossover frequency. It is used to fine tune the sub's phase to match that of the main speakers near the crossover (using the Left Front speaker as a surrogate for all the main speakers).
So shifting phase 180 degrees does not reverse one sub vs. the other over the whole bass frequency range -- only near the crossovers.
There is another control called Polarity. It has the effect of swapping the speaker wire driving that sub -- which means it swings things around 180 degrees across the entire bass frequency range.
Typically if you have one sub in the front of the room and one in the back (as you have done), you would set the one in front to "normal" polarity, and the one in back to the opposite polarity.
Then you use the Phase control on each sub to refine the Phase of that sub when played in combo with the Left Front speaker -- using the phase calibration test tones from a calibration DVD.
Do you follow? Phase 180 degrees around is not the same as inverting Polarity. Phase operates over a limited range of frequencies. Think of which direction the speaker cone is moving. The speaker in the rear of the room is turned around compared to the one in the front which is why you typically start with the two subs at opposite polarities so that both cones are moving in the same direction. Then you use Phase to refine that around the crossover frequencies.
Personally I think this is better done by ear than with the SPL meter. Basically what you are listening for is the phase setting that gives the most output when the sub and LF are playing that Pink Noise test tone together. If the sub is out of phase with the LF then the portions of the test tone near the crossover will cancel out since it is coming out of both the sub and the LF at the same time. That leaves just the lower frequencies of bass below the crossover. So another way to think of this is you want the phase setting that seems to give you the most HIGHER FREQUENCY sounds from that pink noise test tone.
OK so you set the front sub to "normal" polarity and then adjust it's phase as described to best match LF. Then you power it down and switch to the rear sub. Set it to the opposite polarity and then adjust its Phase as well to work best with LF. When both subs are matched in phase to LF then they are also matched in phase to each other.
Done this way (the two subs using opposite Polarity) you may find that the best Phase settings for the two of them are even the same Phase. More likely you will find it is some random difference of Phase -- not 0 and not 180. Why? Because the proper Phase is also a function of the distance of the sub from the LF speaker and of course that's quite different for your two subs.
Using opposite Polarity -- which completely reverses one sub with respect to the other -- is not affected the same way because of course sub 1 is the same distance from sub 2 as sub 2 is from sub 1. Make sense?
It is easiest to do phase adjustment if you have previously done the volume setting exercise I told you about with the noise level in the Setup menu and the volume controls on each sub. That will result in the LF and sub each putting out about the same volume of this pink noise phase test tone.
The difference between in phase and out of phase is subtle so take your time. When you think you have a candidate Phase setting, try swinging phase 180 around from that. If you had a good candidate Phase, then 180 degrees around from that will be the worst Phase. Can you hear the difference in the higher frequencies of that Pink Noise test tone? The good Phase setting should have more higher frequencies in that hiss. It's not very much so listen carefully and, again take your time. Go back and forth a few times to train your ears for this maximum amount of change.
Now go back to your candidate proper Phase setting. Shift off it to one side and sneak up on it until you think it is right again. Then shift off to the other side and sneak up on it again. Compare you two results and split the difference if they are not the same. That's how you refine your idea of the "best" Phase setting. With a little practice you'll get the hang of it.
Another tip: When playing the Pink Noise phase adjustment test tone from the calibration DVD, adjust the main volume on the Anthem so that the Pink Noise measures about 70 to 75dB SPL. That's loud enough for you to hear the subtle difference between in phase and out of phase without being so loud that it gets too tiring to listen to it long enough to make a good adjustment.