Odp: [sdiy] Re: About this LC filter formula questions

[Roman Sowa]

Sound pipes are like wavegides in GHz range. If the pipe is big
enough, like 50mm, it can transmit soundwave in several modes from
certain frequency up. 50mm is wavelength of about 7kHz, so you might
expect some nonlinearities above, say 3-4kHz. Sound will bounce
between pipe walls and it influences frequency response and dispersion,
i.e. higher frequencies could take longer route along pipe. The result
is smeared out step response.

In narrow pipe, most of usable spectrum travels in single-mode,
so it gives lower dispersion and more flat response.
But smaller pipe might have bigger damping.

Roman

> I had always assumed that a larger diameter of pipe might yield better
> results, but I'm not certain. Does anyone know the answer to that? What is
> the optimum pipe internal diameter? Should it match your speaker cone
> diameter? I always assumed that the "garden hose" approach was simply to
> save space and money, not to tweak the line for optimum quality. Was I wrong?