Outlaw ICBM and "Time Delay"

Discussion in 'Archived Threads 2001-2004' started by Ron Duca, Feb 10, 2003.

  1. Ron Duca

    Ron Duca Stunt Coordinator

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    I am interested in placing an Outlaw ICBM between my Yamaha RX-V995 (used as a pre/pro) and my Anthem MCA 50 five channel amplifier. However, I am a bit confused about what I have read in this forum regarding "time delay" and the inability to compensate for speaker placement.

    From my Yamaha, I can currently raise or lower the output from the Center and Surround speakers to compensate for varying distances from the primary listening position. Is this the functionality that will be lost or is it something entirely different?

    BTW...I just have a 5.1 setup. In addtion to the above units I have a CD player, DVD player, VCR, TV, 5 speakers and a sub. I do not have an SACD or DVD-Audio unit, nor do I plan to aquire one anytime soon.

    Thanks,

    Ron Duca
     
  2. Tyler DJW

    Tyler DJW Stunt Coordinator

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    Your pre/pro will have a speaker distance compensation, which is what Outlaw is "warning" against using. The problem with using this with the ICBM is that because the ICBM averages all of the low-pass information together, if you introduce a delay between two channels with the same signal, it could be problematic because the average of the two signals could be much smaller, and bass would go missing. I'd like to know if others have actually ever noticed this before when using the ICBM and distance compensation. If you look at it mathematically it could definitely cause a problem, but practically I'm not sure you'd notice.

    [MATH]
    A 20Hz sin wave takes 50ms to complete. The delay between the signal extremes is 25ms. If you shift another signal 25ms out of phase (25ft distance compensation, approx) and sum the two together, you get NO net signal.
    [/MATH]

    I imagine that as long as your distance compensation isn't more than a few feet, you won't ever really notice the difference.

    The speaker level adjustment won't be lost either, but by doing this before the ICBM it will be difficult to balance the bass response, because the sub will receive scaled bass for each channel. For example, if you set your center channel +3dB relative to you mains, then the bass from that channel will be +3dB relative to bass originating in the main channels.

    I hope this answers some questions and my monday morning math makes sense.[​IMG]
     
  3. Ron Duca

    Ron Duca Stunt Coordinator

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    Tyler DJW,

    Thanks for the information. I have a question for you though. You said, "For example, if you set your center channel +3dB relative to you mains, then the bass from that channel will be +3dB relative to bass originating in the main channels".

    Isn't that the same way it works now?
     
  4. Rich Malloy

    Rich Malloy Producer

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  5. Chuck Kent

    Chuck Kent Supporting Actor

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    Tyler, great job on the explanation of both issues.

    My 2 cents on the subject...

    It's worth pointing out that there are forum members here who are VERY concerned about the time alignment issue. I run an ICBM between my receiver and an external 5 channel amp and I just don't hear problems. I think room issues are more of a factor with bass sound troubles than the tiny amount of potential bass delay the ICBM may have. But on an absolute scale, it does exist.

    IMO, the level problem IS more likely to be trouble. I don't suffer from it because my 5 channel amp has input level controls. I run my 2 channel, DD/DPL II and DTS levels in my receiver as all zero (the same) and make the level adjustments (for speaker level matching) at the amp.

    Ron: The correct way to do level matching is after bass management, not before. Ron's example is correct. If you do the level changes before the ICBM, then the relative levels of bass will be different for the channels you changed. And if it's enough of a change, it WILL be audible.
     
  6. Ron Duca

    Ron Duca Stunt Coordinator

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    I went ahead and ordered the ICBM. I also checked the SPL meter calibrated speaker level settings for my environment. The Center is 0db, the Right Surround is 0db and the Left Surround is +1db. That tells me that the speakers are pretty evenly spaced and the volume levels are pretty level. Until I have a chance to tweak the various crossover settings using the ICBM, I'm not going to be too concerned about either the time delay or the speaker level issue.

    Thanks to all for the information provided and for your opinions. Once I receive the ICBM and have a chance to play with it, I'll come back here and post my results and thoughts.
     

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