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#24835 - 12/09/03 11:31 AM Re: LFE polarity question
Keta Offline
Desperado

Registered: 12/29/02
Posts: 358
Loc: Central VA
Quote:
What are you using for mains and what is their published response (+/-3dB)?


Nht 2.5i's, 29Hz-25KHz +/- 3dB manufacturer spec. The speakers are biamped with NHT SA-2 amps which are fed with the front L/R signal and passed on to two channels of the 770 to power the upper portion of the mains. When running these tests I just turned down the amp feeding the lower section of the mains so that only the subs were playing. I did this to only hear the sub (I unplugged the other) while being fed the 60Hz tone in and out of phase. My thought (could be flawed so let me know if it is) was that a single speaker playing a single tone won't sound any different being in or out of phase since it's really not in or out of phase with anything else, and what I was noticing was the drastic change in SPL while listening to that one sub being fed a single frequency with the only change being phase. This only happens using the 6 channel input. The whole thing may mean nothing I was just looking for input from others on what they felt.

Quote:
Also, what 'dedicated sub controller' are you using?


They are a pair of NHT SubTwoi's with a SubTwoi controller which is needed since the subs only have an RCA input to the built in amp. All control ie: phase HP, LP, LFE gain, volume and such are handled by this controller. Right now the controller is only acting as a volume control since all filters are set to bypass and it's only connected to the sub out from the 950. This link will give you a quick look. http://www.nhthifi.com/scripts/nhttech.c...ated=1062965377

I will try your suggestion with running the LFE directly from the DVD player and see how that works.

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#24836 - 12/09/03 02:39 PM Re: LFE polarity question
curegeorg Offline
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Registered: 11/15/03
Posts: 1012
Loc: Raleigh, North Carolina, USA
im not sure exactly what you are trying to correct or figure out. a lot of subs have two phase adjustments (in/out), so one would play a sample with the phase being in and then out and see what they prefer to find the proper phase adjustment. the typical setup would have the phase in the position that produces a less boomy sound.
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#24837 - 12/09/03 02:56 PM Re: LFE polarity question
jgubman Offline
Gunslinger

Registered: 12/24/02
Posts: 49
Loc: San Mateo, CA
ok, I agree the crossover slope in not flawed.

What is flawed is having NO WAY to aviod getting 80Hz and below frequencies summed and sent the the subwoofer. Why can't I get the analog xo out of the way? You're saying that eastech designed the analog BM to ALWAYS send summed info to the sub, regardless of what's happening w/ the info sent to the other speakers? Ok, if that's the case, then the design isn't flawed, but whoever spec'd it that way was flawed. What's the point of having a switch if it's always supposed to be in the "On" position?

Regardless, I think the Outlaw is a great piece at this price point. I've been getting around the analog BM woes by setting all to Large and using an ICBM btwn my amp and preamp. In the DVD-A player's menu, I've set the sub to off. When I want to listen to a DVD-A, I set the outlaw's sub to off and let the ICBM do the filtering. Only problem is remembering to turn the sub back on when I'm done w/ the DVD-A.

I am a little disappointed to hear that the digital XO is now suspect as well.

I'm really looking forward to my next processor not having these quirks.

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#24838 - 12/09/03 03:11 PM Re: LFE polarity question
Keta Offline
Desperado

Registered: 12/29/02
Posts: 358
Loc: Central VA
curegeorg I'm just trying to figure out why I can't properly set the phase of my sub using the 6 channel inputs on the 950. Just imagine my the entire consisting of three components.
1. DVD-A player
2. Outlaw 950 connected to the DVD-A via 6 analog cables.
3. A single powered sub connected to the 950 using the 950's sub out. No other speakers.

In this phantom system if you were to play a 60Hz test tone that alternated every five seconds from "in phase" to "out of phase" the volume of that single sub will vary +/- 10dB. That should not be the case and I'm looking to see if anyone has any insight into why this is. In the above system if you did the same test tones using a digital connection you would not see the volume fluctuation. I'm trying to understand it so hopefully I can work around it. The reason this seems important to me is that if one speaker varies it's volume by 10dB based on the phase of the signal then it will be difficult to properly adjust it when you try and blend in the remaining speakers. Bosso may have the easiest workaround but I havn't tried yet.

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#24839 - 12/09/03 06:59 PM Re: LFE polarity question
bossobass Offline
Desperado

Registered: 08/19/02
Posts: 430
Loc: charlotte, nc usa
OK, I just repeated your tests, using the Chesky disc:

In-phase/out-of-phase, results were correct both in DD and in 6 CH BYPASS (without changing anything in my system).

I then shut all my monoblock amps off to the sats, set all speakers to 'large' and sub to 'on'.

Using the in phase-out of phase test #23, 60 Hz, in DD mode (BTW, the readings were identical for both in phase and out of phase, as you expected, with only the sub playing).

I got basically the same results as your test. This does NOT mean that summed bass is getting to your sub when all speakers are set to 'large' and sub 'on'. It means that the 950's x-over is working properly.

A Linkwitz/Riley 24 dB/octave crossover, which is what the BM consists of in the 950, causes the signal of both the HP filter and the LP filter to be attenuated 6 dB at crossover so that when the 2 signals sum, they are at unity.

When you play a 60 Hz tone and set the crossover to 40 Hz, the signal from only the LP should be down approx. 16 dB.

When you set the x-over at 60 Hz, it should be down 6 dB, as explained above.

When you set the x-over at 80 Hz, it should be down approx 3 dB.

When you set the x-over at 100 Hz, or higher, it no longer attenuates a 60 Hz tone, so it should play at full volume, which, in your case, is 6 dB higher than the reading you get with the x-over set at 60 Hz, playing a 60 Hz tone.

Look at your results and you'll see that the crossover is pretty deadly accurate, accounting for room interaction at 60 Hz at your LP.

What this test DOES prove, is that the so-called 120 Hz global LP filter on the LFE signal is governed by the crossover, and, as such, is NOT global.

It's moot to me, as my LFE is discrete and free of the 950's influence anyway, but Scott assured me in an e-mail that I was mistaken and offered to bench test my 950 to prove it.

If the LFE filter was a global 120 Hz, ALL the readings would be the same in this test.

Sorry for the side issue, and leaving it aside, I hope the explanation above helps you to understand your test results.

As far as the analog BM switch goes, it does NOT read 'in/out' (as in 'bypass'), it does NOT read 'on/on'...it reads 'on/off'. That refers to the sats as 'large' or 'small' and nothing more. The specific function of this switch is more than clearly explained in the manual on page 9.

You can disagree with the nomenclature of the switch for whatever reason, but that does not make the 'on/off' labeling by Outlaw a mistake.

As I said above and many times before...experiment with the switch vs say, a uni player's DVD-A/SACD BM and see if you don't get a better curve with the 950. This is a whole other story for another time, which I will be more than happy to aid and assist anyone who would like to understand Outlaw's engineering of this aspect of the 950 with.
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#24840 - 12/09/03 09:43 PM Re: LFE polarity question
Keta Offline
Desperado

Registered: 12/29/02
Posts: 358
Loc: Central VA
Bossobass I want to thank you for taking the time to run the tests and give an explanation. I'll give the "direct DVD to sub" a try and see how it works. Let us know if you discuss the global crossover issue with Scott and what Outlaws opinion is. For anyone else reading I hope no one got the impression that I was some how disappointed with how my setup was sounding wth the 950. I was just running through some calibrations and this issue just got me spinning my wheels.

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#24841 - 12/10/03 08:31 PM Re: LFE polarity question
bossobass Offline
Desperado

Registered: 08/19/02
Posts: 430
Loc: charlotte, nc usa
Quote:
Originally posted by Keta:
Bossobass I want to thank you for taking the time to run the tests and give an explanation. I'll give the "direct DVD to sub" a try and see how it works. Let us know if you discuss the global crossover issue with Scott and what Outlaws opinion is. For anyone else reading I hope no one got the impression that I was some how disappointed with how my setup was sounding wth the 950. I was just running through some calibrations and this issue just got me spinning my wheels.


I'm always glad to see someone who is willing to tear into his system with meters and tones and get to the bottom of how it all works.

This is how we all learn to optimize our setups, which is always rewarding, and I ALWAYS come away with new info.

I repeated your tests because you so clearly explained the tests you ran...made it easy!
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#24842 - 12/12/03 03:32 AM Re: LFE polarity question
Will Offline
Desperado

Registered: 05/28/02
Posts: 605
Loc: LA's The Place
Roger Dressler of Dolby recently wrote about low pass filters and phase shift in http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=332595&perpage=20&pagenumber=4 with regard to Center, Left and Right speakers, specifically:
Quote:

in a configuration where the C is set "small" and L/R are "large" with no subwoofer, the C bass will be extracted with a lowpass filter and summed with L/R. If the bass in L/R and C is common, then the sum will depend on the phase relationships of the LPF. Turns out that typical DSPs use 4th order LPF. This is fine for driving a sub, but when used in bass redirection as above, the phase shift causes substantial bass cancellation, thus sounding weaker than the 2-ch source played in stereo. We have been instructing the chip makers to switch to 2nd order filter for these specific redirection modes, and this solves the problem.

This is not isolated to PLII, but affects any decoder mode.

I don't know if the 950 uses 2nd or 4th order filters to redirect, but apparently, in some LFE cases, it matters.

Best,

Will

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