Any way to test for proper speaker delays?

Discussion in 'Home Theater Projects' started by Jeremy Anderson, Jul 9, 2003.

  1. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    I've got an Onkyo TX-SR600 with 5 Polk RTi28's and a CSi30 center channel, SVS 20-39CS+/Samson 1000/ART-351 subwoofer setup. The problem I have is this (if I can explain it clearly):

    My mains are both 12' from the listening position. My center channel is 10'. Setting the delays for that works great and pans across the front soundstage are tight. The problem I have is that my room is strange. My left surround is 8' away and my right surround is 10' away, with the center surround at 3'. Up until recently, I have been running the surrounds at 9' and the center surround at 3'. The problem was that pans across the rear soundstage never really sounded cohesive. So I changed the center surround to 2' and that seemed to bring things together.

    So the other day, I'm listening to Chris Cornell's END OF THE WORLD (from the Euphoria Morning album) in DPL-II Music with Panorama turned on. This song has an electronic pinging sound that goes first to the left channel and then to the right. The problem is... with panorama on at my given delay settings, you can't place those sounds. They almost sound reversed. So out of curiosity, I changed the surround delay to 10' and suddenly the sounds were placed perfectly between the speakers. I then ran through some DVD's that had both side pans and rear pans. I found that I had to change the center surround back to 3' to get the rear pans sounding right again... but dammit, now pans from mains to surrounds have lost that smooth transition.

    So I'm kinda' stumped. Is there some concrete way to find the right setting for this? 10' sounds better for music, but 9' seems to sound better for movies. Or are there some other DVD's that have good pans for detecting these transitions? Any advice would be appreciated.
     
  2. JamesHl

    JamesHl Supporting Actor

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    If I had to venture a guess, it would probably have something to do with the fact that you're going back and forth from two different surround modes. One solution to this would be to listen to music in stereo mode and leave your settings optimized for movies.
     
  3. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    Well, the point is... if DPL-II with Panorama on is causing that reversal or muddying effect, doesn't that obviously mean that those delay settings are incorrect? After all, Panorama mode spreads the sound to the surrounds... so if the same sound is playing in the left surround and left main and the delays are correct, it should appear to come from somewhere between the speakers, right? The speaker delays should be consistent no matter what surround mode you're using.

    Anyone else have any ideas?
     
  4. JamesHl

    JamesHl Supporting Actor

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    No, I would say that while they sound correct for one thing, the different way that something else, for instance DPL II, is processed, causes it to sound incorrect. Whereas with 5.1 some audio engineer mixed the soundtrack and pre-recorded it to make sure it has a coherent soundfield, your receiver is trying to do the same thing on the fly using one algorithm for everything. The results will be different.

    Like I said, though, I'm just guessing here. My rears are even more off than yours, and I have them set okay for movies, but I just defer to stereo mode for my music listening.
     
  5. Lee Bailey

    Lee Bailey Second Unit

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    If you use the Avia setup DVD, here is what Guy Kuo recommends for setting the delay up properly. Be aware you need an SPL meter to do this:

    Using AVIA Phase Tests to Fine Tune Speaker Distance and Delay
    AVIA's speaker phase testing signals are also useful for very accurate adjustment of speaker delays and distances. You'll need an analog RS SPL meter set to fast response in order to take advantage of this tidbit. This may seem a bizarre way to check delays and speaker distances but it is surprisingly accurate.
    The phasing tests work by playing noise in the two channels being tested in phase and 180 degree out of phase intermittently. If the speaker distances and delays are both set correctly, then the in phase sounds from both speakers reinforce each other at the prime listening positioning. During the out of phase (diffuse) portion of the test, the sounds cancel. An SPL meter set to fast response can readily show the magnitude of the cancellation/reinforcement.
    Start by playing the Phase left front/right front signal. Move your SPL meter slowly left and right at your listening position. If you have set distance and delays correctly the maximal SPL delta will occur in the middle of your sitting position. I get about a 6 dB needle bounce on my system. If it happens right of center, then your right speaker is either too farther away than the left speaker or delayed more than the left speaker. Conversely, if the peak SPL delta occurs left of your prime listening spot, the left speaker is too far or excessively delayed.
    Once you have the front left and right speaker distanced and delayed exactly right, the SPL meter position at peak delta will be in the middle of your prime listening position. Note that position carefully. You'll need to be able to refer to that point within half an inch during the next step.
    Now comes the trickery that gets the center speaker also precisely phased and delayed. The AVIA disc also has a Phase Left Front/Center test. We can take advantage of it to bring all three front speakers into very tight phase alignment. From the previous step we already know where the two front main speakers are in phase. Leave the left and right delays and speaker positions alone now. We'll next adjust the center speaker to be in phase with the left front. This places all three into phase.
    Play the Phase Left Front/Center test and once more move the SPL meter left and right to find the maximal SPL delta point. Compare this new position to the one for the front mains. If all is perfect, they exactly coincide. If the left/center maximal SPL delta point is left of the left/right point, then the center speaker is either too close or insufficiently delayed. If the left/center max delta point is right of the left/right max delta, then the center speaker is too far. Move or adjust CENTER channel delay as needed to get the left/center max SPL delta to occur at the exact same place as for the left/right channels.
    Your left, center, right speakers are now in phase. You'll probably note that a 1 msec adjustment in channel delay makes for a considerable shift in max SPL delta position. After all, that is about a 1 foot speaker distance equivalent. Use very small speaker movements to fine tune the center speaker into phase alignment.
    Put your head at the center of the max SPL delta position and listen to some stereo and 5 channel material. You will be pleased with what has happened to sound imaging in your system.
    Moving your speakers to achieve exact phase match isn't the entire story. One must also position the speakers with relation to room acoustics to smooth frequency response. Sometimes, moving speakers into exact phase also moves one or more of them into positions that yield uneven frequency response. In such cases, some compromise is needed to address both imaging and frequency response concerns. Happily, the home theater sound processor does have delays and these can sometimes help bring speakers into phase, while still keeping them closer to best tonal balance position.
     
  6. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    Well, using Avia with those instructions from Guy Kuo, I think I finally got my delay times straightened out. My mains and center remained the same (12' and 10'), but my surrounds ended up at 8'... which is strange because I was testing using the phase test between the right main and right surround (which is 10' away -- the left surround is the one that's 8'). Once I got that straight, I ran through Avia's 360 degree pans with EX turned off so I could evaluate it without the center surround and the transition to the surrounds was much improved. Then I turned EX on and played with the delay time for the center surround until I got the pan across the back sounding equally smooth when A/B'ing between EX on and off. It was the only way I could think of to judge the back surround delay, since there's no way to do that phase test on the center surround (outside of having phase tests in DTS-ES discrete). I ended up at 3' for the back surround. For some odd reason, when I put my tripod in place and rechecked the levels after doing all of this, I had to reduce my center surround from -4 to -6 on my channel trims... but it sounded just as loud during EX material.

    I then ran through a few DVD's I am familiar with and the difference was remarkable. I popped in the Travolta flick BASIC, which I had received late due to July 4th mail... and WOW! It was like listening to a whole new system. Maybe it was just because of how aggressive the surround usage is in that movie, but I was pretty happy. I then popped in the aforementioned Chris Cornell song in DPL-II to listen for the left and right pinging sounds... and they imaged correctly. So I guess I have it straightened out now. Thanks to all for the advice!
     
  7. DavidES

    DavidES Stunt Coordinator

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    Thanks Mr. Bailey for sharing that tip.

    Just FYI for everyone trying this, I had to set my meter to A-weighting to eliminate the reading of the bass present in the test signals in order to get a precise delta position and also make sure your trim levels are within 1 dB of each other; that does makes a big shift in the delta position.

    Now is it possible to apply this to rear monopole speakers or bipoles?
    I know it wouldn't work with dipoles due to their nature.
     
  8. Lee Bailey

    Lee Bailey Second Unit

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    You are entirely welcome. My thanks to Guy Kuo, for providing all this information. He really supports his product.
     
  9. DavidES

    DavidES Stunt Coordinator

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    md
     

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