6ch anlog input reversed polarity on sub channel

I know that many of you on this board has experienced this,but I wonder if there was any official "reaction" from the Outlaws.
I did a search and came up with nothing.
The analog xover was one of the main reason I bought this unit,so it's kinda important to me.I use passive subs with pro amps,and they don't have any type of polarity switch on'em.
So what's the word?

If it's actually 'reversed' you really don't need a polarity switch, do you?

When the sub is out of phase with the mains........then yes some type of fix is in order!

[This message has been edited by The Hun (edited March 15, 2003).]

If using an outboard power amplifier, the easiest way to regain proper polarity would be to simply reverse the speaker leads at the power amp binding posts.

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The Soundhound Theater

Hun- I guess a slightly better way of putting this is: If you adjust the mains to be in phase with the sub with DD/DTS/CD digital signals with the digital crossover in the 950, then it will be out of phase using the 6 ch input and the 80 Hz analog crossover. I just see this as an example of the $899 price. I just change to the inverse polarity input on my sub when I play DVD-A and SACD material.

Oh yeah, a strange observation. I have a std and inverse input on my sub, along with a variable phase knob. For me, it is easier to just switch from the std to the inverse input. OK, so I bought an A/B switch to do this. Now, the A/B switch is really supposed to be for switching between 2 components input into one input. So I'm kind of using it in reverse: 1 component to switch between 2 outputs.

When I hooked everything up, the position of the switch didn't matter! Instead of easily seeing in phase vs out of phase signals between both positions of the switch, I got no difference at all. Either a bad switch (but something like this is so easy, that that doesn't really make sense), or I'm not understanding how one of these guys operate. Never did get motivated enough to open it and take a look at the wiring. I have another kind of A/B/C switch now someday I will try...
(Position C for no sub, for 2 ch bypass where the 950 also sums the bass to the sub if the speakers are set to small.)

It's only happening when I use the the 6ch input [listening DVD-A MC].
In all other operations it's fine.
So I would have to pull out my amps and reverse the speaker cables,anytime I pop in a DVD-A disc?
You kidding right?
Kevin,
I felt I didn't need to explain the whole scenario as it was discussed several times here before,looks like not everybody read it.
I don't think that this problem is oK for the $899 price, and I doubt the the Outlaws would agree with that "philosophy" either.
Was there any "acknowledgement" at all by them?

[This message has been edited by The Hun (edited March 15, 2003).]

[This message has been edited by The Hun (edited March 15, 2003).]

When it's in phase in 2.1 (stereo+sub), it's out of phase in 5.1 (DTS NEO/DPL II) in my system.

Perhaps if you are handy with a soldering iron, you could build a simple phase inverting stage for the 5.1 SUB output. All that would be required would be a TL071 op-amp and two 10Kohm resistors, not including the power supply and box etc. These parts could be purchased at RadioShack.

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The Soundhound Theater

If you're inclined, you could connect your subs to the amp with banana plugs and easily flip them over when listening to DVD-A. It would be almost as quick as flipping a phase switch.

My Crown amps use Nutrik connectors only!

Can someone please explain this issue in detail. Does this affect everyone who uses the 950 for DVDA or SACD? I have an active sub.

John

Exactly what I was thinking; The problem was stated as "they don't have any type of polarity switch on'em" which makes me think flipping a plug and flipping a switch aren't that different.

OTOH the solution from SH has a certain simplicity - I wonder if anywhere out there is a pro audio item that would invert polarity in a cost effective manner for those not inclined to roll their own?

when in digital modes, you have digital delay settings to time align the satellites (all 5 speakers). when you switch to analog, you lose the delay, causing different arrival times of satellite/redirected bass sound.

this means that the out-of-phase adjustment will be different in every setup.

if someone were so inclined to move their sub to a position that's equidistant with the mains, use 80hz for digital HP and test for phase that way, it might verify that it ain't the crossover. you would not be testing the best bass, but rather the phase difference between digital and analog modes.

in other words, i suspect that this problem isn't unique to the 950. phase is time. very few people place their subs with time/distance in mind, and every setup is different in that respect.

just a view from the peanut gallery.

This is not an acoustical problem,or placement issue, though those considerations are valid to set up "formidable" HT,it doesen't apply here,since the problem is fundamental to a electricalproblem[polarity].
Switching the speaker leads are curing the problem,but it is rather cumbersome way in my case.

if KCB had said his test revealed a 180 degree shift, i would lean toward the analog crossover as the problem and the switch flipping cure.

the 'possible' scenario i offered IS electrical (with delay, without delay)...not placement...as the problem. placement is a way to test the theory.

in repeating kevin's test, i found the phase difference (less difference than kevin's). i have 2 subs. i placed them equidistant with the front 3 speakers and the difference was reduced.

anyone is free to tell me why that is.

Moving the sub around can make it sound less displeasing when it's played out of phase.

That's what I'm telling ya too!
The subs are in "perfect" placement when I originaly set 'em up using the digital inputs,which is 99% of all my listening[movies, music]it's only when I switch to the 6ch input for the few DVD-A discs that I have[and love],would the problem manifast it self.Since there was no changing on any of the speakers locations[including the subs],it's obvious that the problem lies with the 950!

Maybe you oughta give me a hand,my sonosub is 7' tall,and my cube sub is over 150lbs!

Isn't a 7 foot tall sub a risky thing to have in earthquake country? I've arranged my speakers horizontal rather than vertical for that reason.

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The Soundhound Theater

Yeah maybe I should laydown my DefTech Towers too!Briliant!

There was a data point in HTF too. Dude with a Denon 3802 or 3803, added an ICBM. He actually found the same thing. Signal to the sub was "out of phase" between the digital crossover in the receiver vs the ICBM.

Yeah, you can move the sub around, but that's not practical. If the 950 did have a distance (delay) setting to the sub, that's where the solution would lie. Or even a setting in the 950's software for polarity to the sub (my Sony TA-E9000ES had this).

Sorry about the double post.

Haven't been here for a while due to looking for work (was laid off in Oct...still looking)

I think Bossobase DOES have the right idea here. When this "problem" originally was reported by KCB, I took the Chesky test DVD-A, and compared the DVD-A tracks (using the 6CH analog pass-throughs with bass summing on), to the Dolby Digital tracks using the 950's decoder and found NO phase difference.
KCB subsequently got the Chesky disc, did the same test, and STILL got a phase difference. I just went back last night ans checked it again, and still have NO PHASE DIFFERENCE.
I have all my speakers set at the same distance in the 950. In my player, I have all the speakers set to the same distance, EXCEPT the subwoofer, which is closer than all the other speakers (the player, a Pioneer DV47ai a sub distance whereas the 950 doesn't). Maybe this is why I DON'T have a phase difference.
Outlaws/Scott, could you please clear this up for us?
If there is a problem, it could be fixed at the same time as the DTS-ES problem.

The 47ai's sub distance setting only has an effect on the LFE channel, but *not* the info that the 950's analog crossover crosses over from the mains to the sub.

[Edited:] You do have all small speakers in the 950, sub "on" (all large in the player), and the 80 Hz analog crossover switch on the 950 "on", right? (You have to make sure to be using both the digital and analog crossover, repectively, when you do the test.)

[This message has been edited by Kevin C Brown (edited March 19, 2003).]

Yes, all 950 speakers set to small, analog bass management switch set to on, and distances set the same all speakers (which they physically are).
DV47ai all speakers set to large, and all speaker distance set the same except the subwoofer, which is physically much closer.

surroundophile's last post adds fuel to my theory.

he doesn't see the phase shift between analog and digital because his speakers are equidistant from the listening position.

this means that there is no time-arrival difference between the 2 modes of redirected bass to the sub.

the digital delay settings use the front speakers as a zero point, regardless of what distance you select. from that reference point, the delay is added to the difference of the closer speakers.

surroundophile (and anyone who has all sats placed equidistant) actually has no digital delay applied to his system, therefore, no difference when switching to 6 ch bypass.

as far as the ICBM using a 2nd order low pass, i don't understand the logic of that at all. that slope would not match anything in BM mode. OTOH, if using vented mains, the 6th order LP is correct.

if you have, say, vented mains, and you selected the 2nd order LP, you would have a 12DB/octave slope on your sub and a 36DB/octave slope on your mains (vented roll-off of 24DB/oct + 12DB/oct HP applied = 36DB/oct). this, plus the unknown Q of the HP filter and how it reacts to the vented mains, would likely cause a hump at crossover, which would have nothing to do with phase.

also note, the ICBM manual claims less than 1 degree phase shift at crossover.

someone needs to design a delay system that sets the SUB as the zero point and is analog, after D/A, and thus a set-it-and-leave-it system (or...maybe someone already has )

Hmmm. If I were the implementor I'd use the furthest speaker as zero and compensate the others. Are you certain the fronts are hardwired as the zero point, or does it just happen to work that way often? It seems the surrounds could often be furthest on bigger rooms.

i suspect that you are correct...the largest number is the zero point. i should have been more specific.

unfortunately, there is little in the way of specs that explain how digital delay is set up on pre/pros.

i wonder why the sub isn't included in the delay setup? it's 'usually' the farthest speaker. it still wouldn't solve the switch to analog, where no delay is offered.

There are some DSP boxes out with VERY configurable processing for pro (AES/EBU ?) digital connections - I'm hoping that once the consumer digital audio connection is finally standardized we as consumers start to see similar devices for that data-stream.

In that case analog processing could be finally obsoleted for most applications.

BoB- I'm not buying it.

The reason why, is that my sub is immediately to the left of my left main speaker. The left and right's themselves are identical distances from my listening position. (About 8 ft for the mains, and maybe 9.5 for my sub.) 1.5 ft isn't enough to explain the difference I get. At 80 Hz, it would have to be about 6.8 ft or so. (1/2 the 80 Hz wavelength.)

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. I still get the phase difference. Distances in the 950 are set identically to the player (except for the sub, which the 950 doesn't have).

OK, but now that I think about it, here's a question: I use the variable knob phase control on my sub to dial in the "phase" (i.e., time alignment) for DD/CD/DTS because the 950 does not have a distance setting for the sub. So maybe in the player, I should set the distance to the mains and sub as the same? (Because it's already compensated for?) *That* makes sense, but again the problem is that I only have 1 ft difference in the player for the mains and sub distance.

??

[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.

In the many measurements I've done, a 180 degree polarity reversal will cause a suckout of about 6db at the crossover frequency in cases where the woofers of the mains and subs are placed next to each other, when observed on a RTA. The farther apart the placement, the less the suckout will be, but depending on the place where you are measuring, there will be random peaks and nulls because of the acoustics of the room. These peaks and nulls will occur whether the woofers are in polarity or not; they will change in frequency somewhat from in polarity to out of polarity.

While all this is obvious on the screen of an RTA, the audibility with actual program material is generally much less. In addition, changing the polarity of the sub will yield flattest response in some locations and worse response in others.

Generally, I would determine the setting that yields flattest response at the listening position and call it good. Trying to find a setting that is valid in all parts of the room is difficult, and it will get harder the farther apart the sub is placed from the other speakers.

All of my measurements are at the listening position. (Finally got a tripod last year, so not even dependent on my left arm for holding it in the same spot! )

It *is* hard to explain the *more* out of phase result for DVD-A and the Chesky disc test, except that I am guessing that the test tone is sent to all 5 main speakers and then compared to either info that is crossed over to the sub from the 5, or a specific LFE signal sent there.

Also, on my system, the difference between in phase and out of phase is night and day. There is a specific music test for this also on the Chesky disc. Bass guitar notes. In phase, you can feel the rumble. Out of phase, you hear the notes, but no rumble. Same-o even when I play the Get Yer Ya Ya's Out SACD by the Stones. You wouldn't think that there's a lot of lower freq content on a disc like this, but there's enough that the difference is easily apparant.

The EFT software has phase stuff in it, I'll take a look and see if there's anything relevant.

My observation exactly!
I also used the listening position as "reference".

As I mentioned earlier I have a phase difference when switching between stereo (with sub) and 5.1 (with of course sub).

The difference I hear between in phase and out of phase is the virtual positioning of the sound is centered where it should be, when the speakers and subwoofer are in phase. But the virtual positioning moves away from being centered and sounds just plain wrong, when the subwoofer is out of phase with the speakers. YMMV.

Will

Did the Outlaws ever acknowledge any polarity problem with the fixed 950, as reported by KCB and others?

Please pardon my ignorance on this subject. But I have a couple of questions. Is it known if this phase reversal is ocurring on the input circuitry of the 950, or the output?
I am curious because I run a 4 satellite, one sub system and have the DVD player set up for all large, with no sub.
I do not use the sub output, I only run 5 analog inputs and let the bass manager in the 950 output any bass below 80Hz to my sub.
So I am not sure yet, if I am getting any 'suck-out' yet from phase reversal. Any comments would be appreciated.

One more thing, where is the best source for the Chesky test DVD..still looking, many are sold out.

The Outlaws never officially [or un]admitted to this,as they unable to "reproduce" this phenomonon. My ubderstanding is that it happens on the Sub in or out,so if you don't use that in/output then it won't affect you.

I apologize, my wording was incorrect. I do not use the sub output from the DVD PLAYER to the 950 SUB INPUT. But I do use the 950 SUB OUTPUT!

This guy saw it too:

http://www.audioholics.com/productreviews/avhardware/SherbournPT700072100.html

I don't actually think the Outlaws ever tested for it... It's a bugaboo, but there are ways around it.

DaleB:

What player do you use?

Apparently, it must do digital BM in DVD-A/SACD formats, in which case, to which 'large' speakers does your player route the LFE signal?

The 950 filters the low freqs (LFE included) and outputs a single bass signal to the SW output.

What happens to the center channel signal (you say it's input into the 950, but you run a 4 channel+sub setup)?

Sorry for the Q's, I'm just curious

No problem.
I am running a Panasonic CP-72. The configuration in the player is all 5 (sorry I did say 4) set for large. So all info including LFE is sent through those channels.
I 'eliminate' the sub out. (In the player menu as well as physically do not connect a Sub input to the 950 from the player).
So now, the crossover in the 950 (switch ON) splits at 80 Hz, anything lower rolling off to the 950 sub output. Anything higher, rolling up to the 5 satellites.
And they are satellites, this is an M&K 750 THX system. Sub is self-powered.
Back to my orignial question, is the phase reversal happening within the 950 Bass Management OUTPUT circuitry, or only on the BM input circuitry? Breaking it down futher, visualize a signal and ground at the sub input to the BM and a signal and ground to the Sub output. Where is the phase reversal actually happening? I am probably over-simplifying the anomaly.

I don't understand your question.

If you set the phase to be correct between the mains and sub using the digital crossover in the 950, via the digital inputs, more than likely, the phase between the mains and the sub will be out of phase if you use the 5.1 analog inputs. The difference in phase is probably being introduced by either the digital crossover circuitry itself, or the 80 Hz analog crossover.

I jumped into this subject with both feet without fully understanding the actual characterization.
Analog signals will be processed with the sub output being out of phase with the other channels. The sub output is in phase on digitally processed signals.

My question with regards to not using the analog sub input from my DVD player is inconsequential to this anomaly.

I think this happans at the analog section,and I have a feeling that if it's not the crossover itself,then it could be reversed wireing on either on the sub input or output.
Just for the record 2 out of 3 950's I had didn't exhibit this anomoly.

Dale, in order to find out that you have this problem play the identical disc say a music DD or DTS concert video for instance,and change the input from "6ch input" to DVD input,and vice versa.If there is phase shift you'll hear it.

Yes, listening to drums during the intro of Hotel California the bass was identically as prodigious in the 6ch analog mode as in the digital input mode. My 950 does not exhibit the reversal problem.
Seems like it could well be a miswire, and Outlaw should have a fix by now.




[This message has been edited by DaleB (edited June 29, 2003).]

Don't know if Outlaw fixed the out-of-phase problem or not, since Outlaw never acknowledged the problem existed, in the first place.

I have just read through this discussion thread quickly, so I am just barely informed. Perhaps someone with an A/B ‘scope and some RCA ‘Y’ connectors could do a simple test for us to determine if there is a 950 phase reversal problem. I would advocate this over “room listening” so that room effects are not a part of the test.

Source set-up: with either a sine-wave generator or a test disk playback set to play 60Hz, use a single output through a ‘Y’ adapter to give two in-phase signals. Add a second ‘Y’ adapter to the first ‘Y’ adapter to give three in-phase signals. Connect one of these signals to the Left Front input of the multi-channel inputs. Connect the second of these signals to the Sub input of the multi-channel inputs. Set the 950 to multi-channel mode with Analog Bass Management “off.”

Before testing the 950, directly connect the test signal to the ‘scope and check that the sine wave being used is ‘clean and nice.’ If any signal summing in the 950 or in the ‘A+B’ mode of the ‘scope shows and oddly shaped wave, then we are dealing with phasing other than at 0 or 180 degrees.

Tests 1 and 2, other connections: Connect the Sub output of the 950 to the ‘A’ input on the ‘scope. Connect the Left Front out of the 950 to the ‘B’ input on the ‘scope. First, look only the ‘A’ input on the scope (do not ‘A+B’ yet). Since the 950 will sum the 60Hz of the Left Front input with the Sub input, you will see the result of this summing on the ‘scope.

Test 1: Disconnect one of the ‘Y’ adapter inputs to the 950. If the amplitude on the scope drops, then you have shown that the two signals were in phase with each other as the inputs were summed. If the amplitude rises when one signal is disconnected, then the inputs were summed out-of-phase and disconnecting one of the inputs has taken away the cancellation effect, allowing the output level to rise. Assuming that with both inputs connected, the output is higher than with only one input connected, and that the sine wave still looks like a clean sine wave, Test 1 has a passing grade, meaning that the inputs are processed in phase with each other. If the output wave became oddly shaped (not a “nice” sine wave) when the two signals were summed, then the two signals are being summed somewhere between 0 and 180 degrees phasing with each other and we have found yet another problem.

Test 2: with the Analog Bass Management switch on the 950 set to “off” so that the 60Hz signal will be present on both the Left Front out and the Sub out of the 950, switch the ‘scope from ‘A’ only to ‘A+B.’ If the ‘A+B’ amplitude is higher than ‘A’ alone, without wave distortion, then we have shown that the outputs are also in phase. Test 2 is passed, meaning that the outputs are also in phase with each other.

Test 3, absolute phase: instead of the ‘B’ side of the ‘scope being connected to the Left Front output, connect the third leg of the ‘Y’ adapters to the ‘B’ input on the ‘scope. If the ‘A+B’ selection on the ‘scope provides a higher output than either ‘A’ or ‘B’ alone, then we have shown that the 950 provides an output that is in phase with the input while in the Multi-channel bypass mode.

If the inputs are in phase (Test 1), and the outputs are in phase (Test 2), then your listening will be OK regardless of whether there is any timing or phase shift seen in Test 3. Test 3 is only for the sake of “knowing.”

Why not test the difference between Multi-channel bypass and other modes? Because as long as any mode is in phase with itself, you only listen to one mode at a time, right? As long as the Sub remains in the same relative phase to the rest of the speakers in each mode, each mode by itself is OK. If one mode has a different phasing error within itself than another mode has, then “oops!,” we will not have consistency of speaker/sub phasing.

Oh, if you turned the analog bass management “off” for the testing, it may need to be turned back “on” again for your normal installation.

Remember, any phasing error between your regular speakers and your sub(s) produces problems only at frequencies being produced by both the regular speakers and the sub(s) simultaneously. Also remember, since the regular speakers are spread around the room, your subwoofer(s) can’t be exactly in phase with all your speakers at once anyway!

Bottom line: since we were here to talk about the 950 … if Tests 1 & 2 turn out OK, then any realized error is not because of the 950.

Mine did it with 2 different test discs. Chesky Ultimate DVD-A disc (has really good phase tests among other good tests), and you can also observe it with a simple discrete test tone CD. Play a tone at or near the crossover freq, then compare SPL measurements from the front 2 channels of the 6 ch input, vs a 2 ch input that is digitized. A couple of buddies of mine suggested it's due to the extra delay (i.e., processing) involved with the digital side and the crossing over of the mains to the sub. Not the same, but maybe the same, a dude on HTF spotted the same effect when using the ICBM with a Denon receiver. When one was in phase (digital or analog), the other was out.

Personally, I don't feel that listening to actual material necessarily reveals it on all systems. Not unless you specifically put the sub out of phase 1st so it's apparent what the effect is. You should know what to listen for 1st, to make it easier to tell betweeen 2 unknown signals.


[This message has been edited by Kevin C Brown (edited June 30, 2003).]

I would agree that it bears more testing. I recently ordered the Ultimate disk and plan to conduct more comparisons.
The phase test on the Avia disk may not be as revealing for the sub, but intentionally setting the sub out of phase may make any differences more apparent when changing form digital to analog modes. Something worth trying for sure.



[This message has been edited by DaleB (edited June 30, 2003).]

The Chesky disc has a very eye-opening music passage in addition to the test tones. For the music selection, it's a simple bass guitar. In phase, you can hear the bass notes the instrument is playing, but you can also feel the rumble too. When it is played out of phase, you can still very distinctly hear the notes. Absolutely no difference. But ..., the rumble is gone.

It seems the MGM Lion might be a good test too.


In any event, I shall check it out further. I was watching a DVD the other night with quite a bit of bass, but had expected to 'feel' more bass than I was. We shall see.

Using the Chesky disk, I was able to verify no difference in bass output whether processing digitally or analog.
When playing the test section (cut 33) I was able to detect definite voids in the out of phase tests, vs. impact from the bass guitar as each note was strummed when 'in phase'. I could feel the 'impact' in my gut. I have not checked it with the RS meter as of yet, but it obvious when listening.

Interesting... What player are you using? All large, sub on in the player? And, you're using the 5.1 analog inputs into the 950, with the 80 Hz switch ON in the back? A two channel input won't work right.

Dale,

I'm a little late on this, but does the BM in your DVD player redirect the sub channel to the mains when you set the mains to Large and the Sub to No? The reason I ask is because the Denon 2900 doesn't and, according to Denon's engineers, it's no supposed to.

I am using a Panasonic CP-72. I have all 5 speakers set to large, the sub turned off.
I only run 5 cables to the 950. I don't run the sub. I 'hang' my sub on the 950 sub output, analog switch set to 'ON'. Everything below 80 Hz is directed to the sub via the 950.
I do not understand why a DVD player would have a Large setting for the mains if it does not include bass information to the 'large' speakers.
I am getting the full spectrum to all outputs from the player. If I am missing something, I don't know what it is, unless it's something below 15 Hz that would crack the foundation of my house. We call those earthquakes in California.
BTW I have the digital output of the player turned off, and the standard stereo (analog) output from the player fed to the CD input of the 950.

Dale,

Believe me when I say that I'm not looking for a problem for you. The response that came back from Denon when I pursued the LFE redirect thing in the 2900 was that the redirect is performed in a pre/pro, not a DVD player. Once I knew that the unit was operating as designed (even though I wasn't pleased), I was able to move on and I hooked the sub out from the 2900 to the 950. The only reason I didn't in the first place was because I was hoping to run stereo subs.

It sounds like you're listening to movies by decoding the DD and/or DTS in the DVD player. Did you ever run a test to ensure that the LFE content is coming through and that what you're hearing out of the sub isn't just the redirected bass from the 950? Again, I'm not trying to raise doubt for you. It's just that this was something that frustrated me for a couple of weeks and could easily go unnoticed.

Regards,

Bill

That's quite all right. I was really addressing what appeared to be a phase problem when using digital vs. analog output, and which I do not seem to have.
I guess I would need to look at the programming in the DVD player again, but not sure what I would do different. I do have it's digital output turned off, but doubt that is the same as digital processing. And in fact I can usually see the symbol light up in the DVD player (DTS or DD) when playing a DVD. I also wondered if leaving the sub on in the DVD programming and hooking it up would add something more (LFE?)...I do need to experiment more it would seem and do not mind doing that.
What would be the right test for LFE out of analog outputs?

None of the Pioneer players redirect the LFE output either (47a, 45a, 47ai). So you'd lose the dedicated LFE output from any disc you listen too. Dale, how are you checking for phase again? Real content or a test disc?

The Chesky test disk. Either using my DVD player with the digital optical output into the 950, against only the analog input into the 950. I detect no difference. In phase is in phase as described on the disk, and out of phase is out of phase as described on the disk. I never change the phase switch on the sub. db level on the RS meter are the same, etc.
I have also done more subjective comparisons with action disks (Tears of the Sun a most recent).
My HT room has a slab floor. So most all bass is conducted through the air.
I get lots of artillery shots falling in my lap, no problem. Digital or analog, they sound (feel) the same.
So either there is something wrong in my test setup or technique, or not all 950's are created equal.

Kevin,
So what you are saying, LFE is digitally encoded (usually bitstream is selected), and would only be sent to the 950 when using the digital output from the DVD player and not analog?
But I don't understand why it would not go through a D/A in the player and directed to analog outputs when either a sub is selected, or other speakers are set to large. It sounds like you are saying it's bypassed when the player is in analog mode.
And is this true for all players with 6 channel analog outputs that support DVD-A an SACD?

Dale- If you have a slab floor, believe me, you will be getting a lot of reflected sound off of the floor.

Yes- I think! I.e., if you have all large and no sub in the player, that will *not* affect the digital feed from the player to the 950. But you are effectively eliminating the LFE portion from the analog output from the player to the 950. Actually, let me ammend this: Players are supposed to redirect the LFE to the mains with all large and no sub, but for whatever reason, neither the Denon or the Pioneer *universal* players do this *for SACD/DVD-A* sources. I actually don't know if this works or not for DD/DTS type sources.

I personally did not check to see if there was any change in the phase relationship after I upgraded my EEPROM. I think Scott said there were no changes, and it does sound like you are testing correctly, but again, I don't know if your results would change if you hooked up the LFE line from the player to the 950.

Some people have said that this may depend on an individual's setup, but try as I might, if you have the sub in phase, and all the distances correct in the 950, everyone's 950 should act the same way.

Here's a thought though. The estimate for the phase difference is 180 deg. I have a variable phase knob on my sub, so I can get my sub in perfect phase with the mains. If you only have a 180 deg phase *switch*, that means that you cannot get perfect phase. So if it's 90 deg out, and then with the 950's crossover difference, it would go to 270 deg out, and you actually wouldn't hear a difference in that case either. The other issue, is that I believe that the Chesky's phase test is not just between the mains and the sub. I believe that it send information to all 5 of the 5.1 channels in addition to the sub. So maybe in your case, even with the phase difference in the 950, you still have a majority of channels in phase in the digital case *and* in the analog case too, so again, no audible difference. Maybe BoB or SH can think about this, because my brain hurts now...

That's why I can always fall back on the discrete test tone CD test that I did. That only tests for phase of a 2.0 signal that is crossed over to the sub. Mains and sub only. I never really worried about the phase of the center and surrounds/rears, because I listen to more 2 ch music.

I do have to think on this some more. I will configure the player for all large + sub and connect the sub. I am not sure how to test the presence of LFE. Can this be done audibly?
Yes, a slab floor would be reflective, even though there is carpet, etc. But of course wood flooring will transmit bass more effectively (for better or worse).
Well, overall I am quite pleased with the performance, but want to learn more.
I would also like to experiment with 2 channels, as that is how I enjoy personal or more critical listening of CDs.
If just listening casually, when there's company, etc., I usually leave it in the PLII-M mode.
I sincerely appreciate the comments and suggsstions.

Isn't bass management wonderful?

KCB: Discrete test tone CD...what exactly does that mean? Do you disconnect the digital jack when switching to analog through the FR/FL of the 6 ch analog inputs (for the test)?

Using the Avia setup disc, which I believe is in DD, the Denon 2900 does not redirect the LFE to the mains if the mains are set to Large and the sub set to No. I think it's probably the same for DTS sources.

Dale, use the channel identification track you have on the Chesky disc. Keep your setup the way it is and, if the player is redirecting the LFE to the mains, you'll here the guy announce [RADIO COMMERCIAL VOICE]This is the subwoofer channel[/RADIO COMMERCIAL VOICE] through your main speakers. Try it in DVD-A and DVD-V (DD) if your player will allow you to play it both ways.

If it doesn't work, try hooking up your sub to the 950 and turning it on in the player, then set all your speakers to large in the player and let the 950's analog BM take care of the rest. See if you notice, like or dislike the difference.

BoB- Just a 2 ch CD with different freqs in different tracks. So for example to test phase, I can play an 80 Hz tone with an 80 Hz crossover, then swap the phase (input) on my sub and compare levels. (I use the Autosounds 2001 #101 disc. Has individual tracks for 10, 11, 12, ... 98 Hz.)

I test it either digitally to the 950 via coax (using the 950's digital crossover), or via the 5.1 inputs using the analog crossover. (But it's just a 2.0 signal that gets converted into a 2.1 signal by the 950's crossover.)

So with the digital input, using the positive polarity input on the sub, the sub is in phase with the mains. Then I switch to the analog input, and the positive polarity input goes out of phase, and I have to switch to the negative polarity input to get the sub back in phase with the mains.

Hello,

My 950 has the same problem as KCB's. The subwoofer's phase seems to invert 180 degrees when switching from 2 channel to multichannel.

Wish the Outlaws would mention if this is a problem with the original 950 design or not. If not, maybe KCB and I am doing something wrong to cause ours to act this way. But if all the original 950's have this problem, was it fixed in later production runs of the 950?

Best,

Will