Posted by Bob Brines [ 148.63.220.187 ] on December 15, 2005 at 00:51:48:
In Reply to: How much do the harmonics matter? posted by akhilesh on December 13, 2005 at 08:30:05:
>>BTW, my impression is that these harmonics may not matter, except in the raw Voigt pipe, where the dip is pretty bad. The frequency curves in the fostex & Lowther drivers (the F200A I suppose being an exception, and the FE166/Fe167 also I suppose) is so raggedy that a few db here and there are not that big a deal. THe raw voigt pipe does look pretty bad though. <<
Except for the 5th harmonic in the TQWT, it is no big deal to get the response within +/- 3dB, And most of us cannot hear that degree of roughness. Remember, though, our discussion of pipes only applies below ~1000 Hz. Above that, the internals of the box has no effect on the sound of a speaker. Most of the fundamental frequencies in music are below 1000 Hz. As long as the fundamentals are properly reproduced, any roughness above that will be heard as coloration. As rough as the Lowther DX2 is, it comes off pretty much uncolored, doesn't it?
>> Let me clarfiy what you are saying for my own benefit.
I guess you are saying, if a Voigt pipe is tuned to, say, 40 HZ, then the F0 = 40 Hz, and the F2, which is 160 Hz is not well suppressed.<<
That's it.
>> What does that mean: not well suppressed? Does it mean that there is a tendency for there to be a peak there, because of the box, and this peak is not well suppressed? Whereas in a non tapered QWT, the 160 HZ is better suppressed?
I guess I am confused because the math cad model shows a dip for the Voigt pipe, whereas the argument is that it will have excessive peaks. <<
You have to also look at the phase of the driver and port. The third harmonic is out of phase with the driver, therefore, there is a dip at that position.
>> In general, are we saying that the TQWT (hat we are loosely calling a voigt pipe here) produces more of a comb effect than a Non Tapered qwt?<<
It is my experience that TQWT's produce stronger harmonics than straight pipes and require more stuffing to smooth out the response.
Bob
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