Ever Created Your Own Test Tones?

Discussion in 'Speakers' started by Richard Little, Jul 22, 2003.

  1. Richard Little

    Richard Little Stunt Coordinator

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    I have searched fruitlessly for a guide on how to create test tones. I want to make 1/12 octave test tones starting at 10 Hz up to 120 Hz or so. I have got the base frequencies by multiplying 10 by 10^(1/40), then that answer by the same 10^(1/40) repeatedly till I have past 120hz. This is where it gets blurry. I tried using this site for Warble Tones but I don’t think warble tones is what is really wanted for plotting the frequency response of a sub? Has anybody ever made their own test tones? What kind of wave form should be used (sine, triangular, box), what "modulate by" and "modulation frequency", mono or stereo, sample rate and bit rate? I've spent a couple of days worth of “free time” trying to figure it out but nothing. As always, Any help would be much appreciated.
    Richard
     
  2. Edward J M

    Edward J M Cinematographer

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  3. Richard Little

    Richard Little Stunt Coordinator

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    Thanks Ed, you could change your name to Johnny on the spot. I've used the ones from gomer's (Thank You Anthony and Mark) site but end up with clicks after converting to .wav and burning to cd. I dont know if it is true but thought I had read that using straight Sine waves could dammage the drivers coil by overheating it and they were a lot less forgiving of room modes? Is there any truth to that.
     
  4. Edward J M

    Edward J M Cinematographer

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    I had clicks too. Could be nature of the beast. The clicks are quite disruptive at loud volumes, possibly even dangerous.

    I'm working on burning some new stuff from snapbug.

    Sine waves can fry a VC very quickly unless you are careful. If you are running continuous tones for several minutes (like Anthony's 1/12 octave tones), do it at a pretty low volume, maybe 80-85 dB.

    If you want to run high level sine waves (100-105 dB), run a burst only long enough to get a steady reading on the meter (maybe 2-3 seconds), and then shut down for a while to let the VC cool.

    Sine waves are less forgiving of room modes, that's why I run 1/12 octave resolution. Warble tones can work better of you have bad room modes. Talk to MingL and Wayne A. Pflughaupt for more on that subject.

    Regards,

    Ed
     
  5. MingL

    MingL Stunt Coordinator

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    I've generated some warble tones at almost 1/6 octave spacings all the way to 500hz. (10,11,12,14,16,18,20,22,25,28,30..........)Its tough work! There are charts on the net which shows frequency points at 1, 1/3 , 1/6, 1/12, 1/24.

    I set tones with the following parameters:
    -> Warble between octave limits (ie a 20 hz warble tone would warble between 19 and 21hz). This is set with the "Modulate by parameter". So, for the 20hz base frequency, modulate by 1hz, would mean the the 20hz tone would warble between 19hz and 21hz.

    -> Modulate frequency would mean how fast the warble be warbling, ie the 20hz would be warbling between 19hz and 21hz at the rate set by the modulate freq. I usually set them to be 5hz.

    -> Always use sine tones if making your own test tones.

    I prefer to use warble tones over pure sine tones as they tend to approximate better our hearing abilities when measuring with a SPL meter. By nature, our hearing tends towards frequency averaging which is similar to what the warble tone does when read thru the SPL meter. I always use warble tones only with a SPL meter.

    Warble tones are suitable for plotting freq response. Sine tones are also suitable, but beware of burning out the VCs. The problem I faced with using pure tones were that they gave very different results within a meter radius. Warble tones (with their averaging nature) were better for me.

    I prefer sine tones when I'm doing a slow sweep from 10hz and above in conjuction with a RTA. With a RTA, sine sweeps have better resolution and easier to understand. I never use warble tones when using a RTA. Besides, on an RTA, THD can only be measured with pure tones. Can't measure THD on SPL meters.

    For making test tones, I suggest making both pure sine tones and warble tones. Plot both out and compare.

    Oh, never run pure sine tones continuously for long periods of time at loud volumes. Run them long enough just to get a good reading, not any longer. If need to test at louder volumes(if you really must), use white or pink noise and wear ear plugs.
     
  6. Richard Little

    Richard Little Stunt Coordinator

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    Thank you Ming, this little mystery is starting to unravel [​IMG]
     
  7. MingL

    MingL Stunt Coordinator

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    I wouldn't say that warble tones are not as damaging as pure tones. However, as with sine tones or any narrow band tones, play the tone long enough to get you a stable reading.

    Warble tones at say 10hz are almost similar to pure sine tone, due to the narrow octave spacings. The only diff is that at higher freq, the octave spacings are wider.
     

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