Bass Localization Experiment

Discussion in 'Archived Threads 2001-2004' started by Gregory S, Sep 4, 2001.

  1. Gregory S

    Gregory S Stunt Coordinator

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    Hi,
    I've read quite a bit about receivers, such as the Marantz 7200 not offering low enough high pass filter choices. I am particularly interested in the Marantz 7200, but logically felt that the 100 Hz high pass frequency was too high, for fear that the resulting increased low pass frequency of the subwoofer would cause localization problems. If the subwoofer's low pass frequency was set too low to avoid localization issues, then a hole would result. I performed a small experiment to determine if I could localize bass when the subwoofer's low pass was set to high crossover frequencies.
    First, a description of my system...if you would call it that. I have no surround sound yet - not even Pro Logic! So when I get my first real system, I'll be going from straight vintage 70's stereo to the latest DPL II, etc. - WOW, what a leap.
    Sansui 771 stereo receiver
    ACI Sapphire III LE speakers - my most recent upgrade (from Infinity SM 210 speakers)
    M&K MX-80 subwoofer
    Denon DCM-460 CD player
    Toshiba VCR
    Hitachi 32" TV
    Because I have no choice, I run the speakers full range (65 Hz -3 db cutoff) with the subwoofer set to about 65 Hz. Also, the subwoofer is corner loaded and located behind and to the right of the listening position. One I get a real system, I'll start playing with ideal locations, but I notice no adverse effects with the present location.
    The experiment: I played various tracks from the Jurassic Park CD - low frequencies all over the place. First I played them with just the subwoofer - no main speakers. The result: no matter where I put the subwoofer's low pass filter, anywhere from 50 Hz to 125 Hz (full range of subwoofer), I COULD localize the bass.
    I then played the same tracks with both the subwoofer and the main speakers on and then COULD NOT localize the bass, with the low pass anywhere from 50 Hz to 125 Hz.
    The same experiment was performed with Stevie Ray Vaughan's "The Sky is Crying" and "Little Wing" - good bass guitar sequences for this kind of testing.
    I think I have shown, at least to my self, is that the 100 Hz crossover frequency of the SR7200 is not an issue. The subwoofer would probably be set from 80 Hz to 100 Hz - just a guess right now. The only thing I noticed was that as the crossover was increased, so was the loudness from the subwoofer. Probably due to the subwoofer playing higher frequencies, as well as the lower ones. I would imagine that the volume of the subwoofer would have to be reduced to get a smoother integration with the main speakers. In fact I did some more listening with the sub set at 100 Hz, but with the sub's volume turned down some and it did integrate better. Before turning the volume down, there was way too much bass - probably due to too much overlap.
    Hope this helps some people who are on the fence. If you have at least a basic system like mine, try this little experiment.
    Greg
     
  2. Chris PC

    Chris PC Producer

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    I should try that experiment AGAIN. I sort of tried to locate bass using test tones. I noticed that pure sine waves could not be localized very easily, but it was at 80-100 hz where they started to become localized.
    I must agree that listening to my subwoofer ALONE with the xover set to 100 hz does sound horrible. Perhaps there is more to it than we realize. Even when your subwoofer may have been fed sound cut-off at 50 hz, if there was distortion, it would have been most likely a first order harmonic which would be twice the frequency, or 100 hz. Possibly anyways.
    I think the fact that you could not localize bass when playing both the subwoofer and the front speakers was a good thing, of course. Blending the bass between 2 front speakers and a subwoofer seems to create a different sound.
     
  3. Kevin C Brown

    Kevin C Brown Producer

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    Whether or not you can localize your sub, also may depend on the cross-over *slopes* involved too. Steeper is probably better, because it drops off the signal faster above the actual crossover pt. But usually, you can't change the slope that the sub or receiver (pre/pro) gives you anyway.
    (But then even if you can't localize it using the subs crossover, the whichever receiver/pre/pro you get might be different because of the slope!)
    100 Hz is kind of high though. I thought 80 Hz was usually the highest I had seen. (Well, for using "full range" speakers anyway.) But, I use 80 Hz all around, and can't localize it, so 100 Hz might be OK too. Might also depend on your room and how "live" vs "dead" it is, speaker placement, etc.
    Neat experiment though!
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