sinesweep - can tweeters take harm?

Discussion in 'Official REW (Room EQ Wizard) Support Forum' started by Frank Lautenbach, Jan 2, 2019.

  1. Frank Lautenbach

    Frank Lautenbach New Member
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    Hi guys,

    I am using REW for a while now and successfully optimized low-end frequencies in my HT in combination with the awesome MSO multi-subwoofer optimization tool. I take measurements @about 75db as recommended, however, I am wondering if the sine sweep can potentially damage tweeters because the sweep concentrates complete energy at a single frequency at a time while real music or e.g. pink noise distributes energy across a wide range. Is it safe to run sweeps up to 20kHz? If yes, is there a maximum length of the sweep that should not be exceeded? By the way, is it correct that REW internally sweeps up to the double of the configured frequency?

    Thanks for your help!
     
  2. Wayne A. Pflughaupt

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    There’s no danger of frying the tweeter during a full-range sweep, especially if it’s done at a reasonable volume. In the 12-13 years I’ve been involved with REW on various forums, I’ve never heard a report of anyone blowing a tweeter during a measurement.

    Regards,
    Wayne
     
  3. John Mulcahy

    John Mulcahy REW Author

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    The log sweep progresses at a constant time per octave so it gets faster as frequency increases - it takes the same time to go from 10 kHz to 20 kHz as it does to go from 20 Hz to 40 Hz. Because of that it has a pink frequency profile, dropping at 10 dB/decade or about 3 dB per octave as frequency increases. The longer the sweep the more energy is delivered of course, so risk increases with sweep length, but whether any particular sweep length or level poses a risk to your tweeters is probably a question for your speaker manufacturer. It is unlikely for sweeps at a comfortable listening level, but not impossible.

    The generated sweep goes to twice the measurement end frequency, or to half the sample rate, whichever is lower.
     
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  4. Matthew J Poes

    Matthew J Poes Staff Writer
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    Wayne didn’t someone complain to @John Mulcahy about wanting some kind of protection built in because he fried his speakers with an overly loud sweep? I feel like that is how that feature was added.

    In any case I’ve not really heard of it happening either, but i certainly think it’s possible if someone isn’t careful.

    Now the Stepped Sine distortion test! That can blow a tweeter if you aren’t careful.
     
  5. Frank Lautenbach

    Frank Lautenbach New Member
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    Hi John, thanks for your answer - it's pretty clear now. When you say "comfortable listening level" I guess you mean about 75db as recommended? What about the sweep length? I would assume the longer the sweep the better the resolution in frequency, correct? Or is it just about improving SNR with longer sweeps?

    My speakers are Dynaudio Excite series - AFAIK they have a very good reputation when it comes to robustness of tweeters so I guess I don't have to worry about it that much.
     
  6. Matthew J Poes

    Matthew J Poes Staff Writer
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    Dynaudio has very robust tweeters with very high power handling. I would not be overly concerned.

    I have been doing sweep based measurements for 15 years or more on 100’s of speakers and I’ve never damaged a speaker in my life.
     

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