I think the question is interesting. It's a reflection of how people look at a material and form assumptions or impressions on that basis. The reason for using aluminum, in the first place, was that aluminum has a very low resonance. That's also the reason for using mahogany. Yet a lot of people think the metal or wood is going to give their headphone a distinctive "wood" or "metal" sound. This is one reason people complain about the 325. Imagine how odd it is, now, for those same people to save up for a PS-1000, which has an aluminum hat. If anything, the use of the aluminum hat is to avoid coloration from a full mahogany shell - to the degree to which the wood in the shell colors the sound at all. On a cheap pair of SR60s I bought to tweak, I damped the plastic to cut down on the resonance. Doing so may not have created the stuff of dreams, but it went a long way toward damping some of those HF spikes. The result was a sound I found addicting.
My HF2s don't ring. They don't sound sharp or metallic. They're quite mellow. If anything, the wooden RS-1 has more of the upper mids and lower treble than the HF2, which is not because of the air chambers at all. It's because of the way in which the driver is doped. If anything, the wood may have been marketed as a method of "adding warmth" by absorbing some of that HF - or at least by not allowing resonance to echo back in from the walls of the air chambers. But anything the mahogany could do the aluminum should also do. If not, a little foam would fix the difference.