geoffstgermaine

The PRs are opposed from PRs and the active drivers from active drivers in Robert's design. I'd have to see calculations to be convinced that the fall off of pressure with distance within this cabinet was enough to be a significant worry. I'd be interested to see a subwoofer that supposedly took this into account. Most of the PR subwoofers I've seen are close to square boxes with PRs mounted on opposing faces.

I think that most people would feel that the square port is probably worse for distortion than a square port just from looking at the shape of it. A port with a square cross-section is much more susceptible to turbulence than a round port. In grad school I did extensive modelling of plasmas passing through differently shaped objects (and around objects). The purpose of this was to model the effect of inserting a probe into the plasma to measure various plasma parameters. Plasma flowing through a tube with a round cross-section produced far less turbulence than a tube with either a square or a rectangular cross-section with rectangles with high aspect ratios being the worst. Due to the similarity between the plasma being modeled and a fluid like air it is to be expected that the same would hold true for air moving through a port of either of the previously described cross-sections.

Inverting the cones (which could still be done) would only have the effect of reducing odd-order harmonics. Cabinet rocking would not be affected since the cabinet is already set up with the active drivers and PRs in an opposed-firing setup. I'm not sure if you're referring to standing waves with the statement about the pressure not being uniform at every frequency, but in the pass-band of the PRs the wavelengths are in tens of feet (more than 50 feet for the tuning frequency) and so I can't see what effect trying to position the PRs at the "pressure peaks" would have. At such low frequencies the pressure should be fairly uniform. Where would you have placed the PRs? Perhaps you mean something else and if so could you expand on your point? Could you expand on what you mean by the non-linear region of operation and how tweaking the tuning frequency is going to affect this?