I think we are all learning a lot from this discussion. Esp. since TQWT seems to be so favored by DIYers.

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.

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.
What does that mean: not well suppressed? Does it mean that there is a tendency for there to be a peak there, becuase 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 becuase the math cad model shows a dip for the Voigt pipe, whereas the argument is that it will have excessive peaks.
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?
thanks
-akhilesh

Bob

Harmonics are multiples of the fundamental, so F3 (aka F2 in a stopped pipe) = 40*3 = 120 Hz........

GM

I think that this simple relationship is only true for straight constant area pipes. If the pipe is tapered or expanding, like a TQWT, the frequency of the harmonics will not be simple multiples of the fundamental frequency.

Martin

Perhaps this will make things more obvious. This is a plot of driver and port response on a linear X-axis. This is a straight MLTL.

The system is tuned to 40 Hz, which is the first spike. The next spike is the 3rd harmonic. Note that is is up at about 180 Hz, not the expected 120 Hz. The 5th harmonic is missing because the driver is placed at the first node of this harmonic.There is a minor spike in the port response, but it is 30dB down. The 7th and 9th harmonics are present, but the remainder of the series below 1000 Hz is suppressed by the port placement.

Now, why is the harmonic series shifted to the right? I suspect that there is interaction between the cavity resonance and the pipe resonance, but I have never been able to prove that. I would like to see some double humping at the tuning point, but I have never seen it. Someone with more mat/physics horsepower than I might discover something.

Bob

?! Considering the ~accuracy of your horn math models, I'm flabbergasted that you could think this. If true, then a horn could only produce discordant sounds. What changes is the harmonic structure's fundamental (F0) and number of harmonics since horns are 1/2 WL resonators, ergo below this frequency their resonance structure is non-harmonic as a function of its flare rate ('M', aka 'T' factor) and frequency (Fc).

GM