[QUOTE]Originally posted by Kevin C Brown:
[B]BoB- I'm not buying it.


Plus, the test disc is a DVD-A disc, which the player *does* do time alignment for anyway. So time alignment is being done in the player for DVD-A, and in the 950 for CD/DD/DTS.

KCB:,
Are you sure about this? Depending on your player's internal management, you may not be getting what you think. Most of the players have no, or incomplete management. For instance the Pioneer DV47/DV47ai and their clones for SACD only do bass management but no time alignment, and just the reverse for
DVD-Audio,time alignment but no bass management. There are some players that do no time alignment for DVD-Audio.
And there is another strange phenomenon I've notice that I can't explain. My subwoffer is on the left side of my sofa, used like a table. When I do the bass tests, both in-phase and out-of-phase for BOTH dvd-Audio and Dolby Digital tests are equal in level when I sit on my sofa. But, if I set on the floor, equi-distant from the sub and the left front speaker,the in-phase is louder for BOTH DVD-Audio and Dolby Digital. So I think that somehow sub position, your position, time alignment, and room nulls all have something to do with this.
Again.........it would be nice to hear something from the Outlaw engineers on this......HINT! HINT!
Is anyone there listening Scoot????

the 1st question is, is the 950's LP filter a 2nd order filter, or a 4th order filter.

the second question is, what is the LP point set to on your sub. (you're kinda screwed with this one, as the 950 has a global LFE LP point of 120hz, and the redirected bass is low passed @ 80hz. since the 2 signals are summed, you can't control the LFE's LP at the sub).

3rd, what is the low pass point of the LFE sent from the player (if it's 120hz-150hz, you have cascading filters). there should NOT BE a filter on the LFE channel in the player when in dvd-a mode, but, unfortunately, i bet there is.

so...set your sub's LP at 40hz (let the 'hole' exist, for the test).

move your sub.

change the player's sub distance.

try the test.

remember... your rears are much closer to you than your mains/center (about 4 feet, as i recall), so pick a dvd-a disc that has little bass in the rears.

BTW, none of these scenarios exist in my BM system. i have total control of LFE and RB separately. volume, phase, LP point, LP slope and i get LFE in DTS-ES. i can monitor each signal and see if there is signal and if it's clipping at the preamp and/or amp.

you still may be right about the 950's analog filter, but there are too many other things going on to rush to that conclusion.

SoP- Well, the 47ai is *advertised* at least to have time management for DVD-A, but not for SACD. The 47ai *is* different than the 47a, because the 47a had no BM for DVD-A, whereas the 47ai does at least have it for 2.0 DVD-A. (Not for 4.0 DVD-A, and 5.1 DVD-A is unknown; hard to test for.)

It actually *does* make more sense if the 47ai does have time alignment for DVD-A. Because then my question above comes into play: the distance setting in the 47ai for time alignment there, vs the sub's phase knob for DD/DTS/CD because the 950 *doesn't* have a sub distance setting (which also *affects* 6 ch bypass).

Just because I'm curious about this little tidbit now, I'll do some testing over the weekend and post the results. I'll try to get more accurate distance measurements too (up until now, I just kind of "eyeball" it: 6 ft to center channel, 8 ft to mains, 9 ft to sub, etc). And, I'll try to get to the "acoustic center" too, not just the closest part of the enclosure to the seating position.

OK, I'm a scratching my head now. Here's what I got. I'm using the Chesky Ultimate DVD-A/DVD-V test disc. Has really easy to use phase tests. Plays info in phase, then out of phase, and obviously the in phase stuff should be louder, so I have SPL measurements too. All speakers small in the 950, sub on. All speakers large in the 47ai, sub on. 80 Hz crossover switch "on" on the back of the 950. All distances are set correctly everywhere. (BTW, I did exactly measure all the distances, and for example, the 1 ft difference between the mains and sub grew to 2 ft, but unfortunately, doesn't change the results). One change I did make, I changed the sub distance in the 47ai to equal the mains difference. The reason being is that the distance between those 2 is *already* taken into account by how I have the phase knob set on the sub. OK...

DVD-V (digital connection): in phase 82 dB, out of phase 74 (pos sub input)
DVD-V (digital connection): in phase 70 dB, out of phase 78 (neg sub input)

Looks good so far, right?

DVD-A (analog connection): in phase 71, out of phase 79 (pos sub input)

So at this point you would say, bravo, the sub output using the 6 ch input *is* out of phase vs a digital input. But...

DVD-A (analog connection): in phase 66, out of phase 82 (neg sub input)

It becomes *more* out of phase even when I switch the polarity input on the sub!

So I got to thinking, something must be overriding it.

So I changed all the distances in the player to be equal. That way, no *other* channels phase could mess with the fronts. (In other words, you want to do crossing over, *then* delay/time alignment. If I have the actual distances set in the player, it's doing time alginment 1st, then the 950 is doing the analog crossing over last. So it's adding up all kinds of messed up phase info into the sub.)

But the results didn't change much from the previous numbers. The frustrating part? With the Chesky disc and its phase tests, I simply cannot get the 6 ch bypass input into phase. Not with the pos or neg polarity input on the sub, or any change to the variable phase knob, or by changing distances in the player.

Here's a different way, discrete test tone CD, so I know I am only getting 2.0 sound that is then crossed over (80 Hz test tone):

CD (digital connection): in phase 80 dB (pos sub input)
CD (digital connection): out of phase 74 dB (neg sub input)

CD (analog 6 ch connection): in phase 68 dB (pos sub input)
CD (analog 6 ch connection): out of phase 75 dB (neg sub input)

This is the very 1st test I did, and *that's* where I draw the conclusion that the analog and digital crossovers put the sub output out of phase from each other.

Also, the volume levels are consistent within each test, but because the analog and digital connections give different volumes, I adjust them slightly just to give more readable measurements. (I probably shouldn't have done that, then you'd see those differences too.)

So, I am still convinced that the 950 has a phase difference between the sub output using the analog crossover vs the digital. Just that now I am a little bit more confused in terms of how the tests for phase on the Chesky disc are generated...

??



[This message has been edited by Kevin C Brown (edited March 23, 2003).]

Have an o-scope?

They have them where I work, but I frankly would have no idea how to use one. (And they have different kinds too, low freq, high freq, DC, AC, etc...)

One more thing I was thinking of: try the Chesky disc one more time, but unplug all but the front L & R and sub inputs into the 950. But to be honest, I don't think that would give me any different results than the 2.0 CD test (where I used just the front L & R inputs of the 5.1 ch analog input).

While I certainly wouldn't contest the theoretical aspect of whatever phase shift may or may not be present in the 6-channel bypass, I think there is a real world aspect to consider as well. How much does a phase shift actually impact the sound in that frequency range?

If you have two subs out of phase with each other, the problem ought to be obvious. You're going to have cancellation. But that isn't what's happening here as I understand it.

If the two subs are in-phase but out of phase with your "small" speakers, you might only have an audible impact in the form of some cancellation around the crossover point. And then the audible impact may be limited.

In fact, I saw some measurement graphs today comparing in- and out-of-phase sub performance and it was consistent with the guesstimate that I just mentioned. There was a little suck-out in the crossover range but nothing likely to be particularly noticeable in real world content (as opposed to pink noise test tones.)

In my case it's night and day.
The bass almost disappear below the xo point[80hz].
when I exchange the speaker cable leads[a real pain],then everything sounds like the digital inputs.

You could create a test CD with a pair of tones, say one at 60Hz and one at a multiple, like 300Hz. It should be easy to observe any time offset D vs A with a probe on SUB out and a probe on left or right. A tone centered on the x-over would be useful too, since it should be seen at both outputs. This should permit greater precision as to what the electronics are doing. There might even be a free 'scope software that is good enough if you're interested in trying it.

I believe that True Audio's TrueRTA has a Dual Trace 22kHz Oscilloscope, even in the free level of the software.