[Hartley118]

I wouldn't expect you to be too troubled by flexural panel resonances - with the dual open ended pipes, the internal pressures won't be very great compared with a closed box or reflex design and it looks to be a pretty rigid structure. The main colorations will arise from the air column resonances in the folded pipes, much like organ pipe resonances. You'll get a comprehensive range of harmonically related resonances, the lowest frequency resonance being where the pipe length is a quarter wavelength. That may account for the strong 60 Hz performance - generally good for disco, but a bit high in frequency for reggae bass!

Then of course you have the pipe cross-mode resonances, fairly well spread in frequency if the pipe is tapered, but prominent like a fat drainpipe if it has parallel sides. To control the air column resonances, a soft absorbent cushion in each of the open ends should help because the opening is the point of maximum sound 'particle velocity' where an absorbent has maximum effect. For the cross- mode resonances, an absorbent curtain hung down the middle of each pipe would be effective (particle velocity is a maximum away from the pipe walls). Of course, damping these resonances will make the character rather less exciting, but it should sound more realistic on a wider range of music material.

So, as you say, there's lots of scope for experiment! I suspect you'll get far more control over coloration with this use of absorbent materials than by changing the driver. However, I'd expect a driver with a strong top response to give you the best balanced sound because of all the LF reinforcement from Mr Gough's pipes.

Martin