I just spent an hour playing around with 55 to 85 Hz test tones on my system. (I have 60 Hz chosen as the crossover for the fronts. Vandy 2 CE Signatures. The 5.1 analog crossover is 80 Hz.)

I have come to the following unfortunate conclusion:

If I set the phase correct between the mains and sub for the DVD input using the coax digital connection (the 2 channel analog connection responds the same way anyway), and then I switch to the 5.1 analog input, the phase is out.

(I'm using the Autosound 2000 discrete test tone CD disc.)

I have an adjustable phase knob on my sub. And an inverted input (180 deg out), so I can cover the entire 360 deg possible. I repeated this many times. I adjust the phase to get the maximum output on a Radio Shack meter using the coax or 2 channel analog connection with the phase knob. Then I switch to the 5.1 input. The max in this position is roughly opposite on the phase dial. Doesn't even matter if I invert the input. (One of the inputs is always higher than the other, the correct one, but even within the sound level values measured for each input, the max for the 5.1 input on the 950 is always NOT the same as for the coax/2 channel analog input.)

OK, just tried using an 80 Hz crossover, and same thing.

Digital vs analog crossovers can induce *different* amounts of phase shift in the signal. But I would have thought that this would have been anticipated and compensated for somehow.

Scott?


[This message has been edited by Kevin C Brown (edited September 29, 2002).]

What do you mean that it acts the same when the input is inverted? Did you swap polarity and it's still 180 out of phase?

Cary

If you set the phase correct for stereo digital, is the phase correct for 5.1/7.1 channel digital?

Will- Yes. So that's good. Probably the same circuits/algorythms anyway.

J- What I mean by, "when I invert the input to the sub the effect is the same," is this:

OK, I use the "positive" sub input. I use the coax digital input on the 950 from my DVD player. Now, I adjust the phase knob on the sub so I'm getting the max output from the sub/mains at the crossover freq.

Now I switch to the 5.1 analog input on the 950 from my DVD player, still on the "positive" sub input. Now, I have to rotate the phase knob about 180 deg to get the max output from the sub/mains. My sub is in the corner, and I'm looking at the SPL meter on a tripod at the listening position.


OK, now I switch from positive to negative for the sub input. *Everything* reverses. Where the 5.1 input was at a max, now it's the coax digital input at a max, but now I have to adjust the phase knob ~180 deg to get to the max for the 5.1 input. => But because I switched from pos to neg on the sub, all of the max values are a little less than for pos. So the positive input is the best.

Short term solution is to just adjust the phase knob specifially for SACDs and DVD-As played through the 5.1 analog input on the 950, but obviously that's a pain.

Outlaw should either compensate for the diiference in phase between those inputs, or have an easy-to-adjust software setting for sub phase. The Sony TA-E9000ES has this in the config menu. Anthem's AVM 20 V2 of the software adds this.

I also thought this might be a time alignment issue. But in the Outlaw config, my mains are the farthest away, so they are not delayed at all. (The signals from the closer speakers are delayed to arrive the same time at the listening as the farthest speakers.)

And I only have a 1 ft difference in my DVD player's config between the mains and sub. That's not enough to cause the problem. Besides, like I said, the coax digital input pretty much matches the coax analog input, which *would* have any delay present from my DVD player. So the cause is the 80 Hz analog crossover in the 950.

I just freaking thought of something!

The problem is that there is a phase *difference* between the 5.1 analog crossover and the digital crossover in the 950.

So, *theoretically*, I can keep adjusting the *difference* in distance to me between the mains and sub in my DVD player's config until I get that phase to match.

For example, at 80 Hz, the wavelength is 13.75 ft long. Right now, I have that distance *difference* at 1 ft. If I change it to 13.75/2 ~ 7 ft (or so), that should compensate for it.

The problem then? I have a Pioneer DV-45a, which *does* apply time alignment to DVD-A, but NOT SACD.

Plus anyway, I might be getting the *phase* correct, but in terms of absolute time alignment, I might be an entire wavelength off.

The real soultion is for the software in the 950 to compensate for that difference...

[Added] This won't work anyway. Would only affect the phase of the LFE .1 signal, but not the signal from the mains crossed over to the sub in the 950...



[This message has been edited by Kevin C Brown (edited September 29, 2002).]

I also found that the subwoofer phase needs to be reversed when going from stereo to 5.1. If you normally listen to stereo, you might just leave the subwoofer phase optimized for stereo. Or if you normally listen to 5.1, leave the subwoofer phase optimized for 5.1.

Either that, or you can manually change the phase on your subwoofer each time you switch between stereo and 5.1.

Good luck!

[This message has been edited by Will (edited October 01, 2002).]

Will- Super duper thanks for confirming what I saw/heard!

What I might try and do long term (well, as long as it takes for Outlaw to fix the hiss problem or another alternative pre/pro or receiver-as-a-pre/pro shows up), is to try to adjust the phase in between both settings, and see if I can't get some compromise that works "well enough"...