I was just thinking about this again over the weekend working on a project.. windscreens I mean, not your alternative thread title.
Here's the full spiel, so appologies if you know some or all this suff.
The trade off of any windscreen is the degree of wind-protection vs sonic artifacts. From a 'do no sonic harm' perspective, obviously no screen at all is best. The important aspect of wind-protection effectiveness is trapping dead air space around the microphone capsule. As most realize, the primary artifact from any effective windscreen is reduction of level at high frequencies, but there can be other artifacts as well.
Basket style screens, including baby ball gag style small baskets, have a couple things going for them: they trap a lot of air without material in that airspace that absorb high frequencies and they are generally larger than foam screens so they trap more airspace. The drawbacks with them from a sonic artifact perspective is that they then have an outer perforated shell with a fabric screen on it and that screen structure can reflect sounds internally.
Foam's advantage is that the material is
isotropic (ie- uniform in all directions) and so are windscreens made from it for the most part- they may be slightly thicker in some dimensions but not usually enough to matter. It does not require a support structure that may cause reflections.
Fur covers work by reducing turbulence around the outside of the windscreen. They are a different material than foam, which isn't necessarily good, but the material they are made from doesn't reflect much sound so sonic artifacts other than even more reduction of high frequencies are minimal.
The reduction in highs is pretty much a linear function that can be compensated for with EQ. Internal reflections are complex and cannot be corrected for. That gives foam an advantage over baskets from a sonic perspective. I’m unsure of what the acoustical impact of sound traveling through layers of different density materials may have outside of the internal reflection issues. That may or may not play a roll in placing fur over foam.
There is an AES paper by J Wuttke of Schoeps that's available for free on the Schopes site which I’ve linked to here before (maybe in that thread you mentioned?) supporting the argument for foam over baskets wherever applicable for this reason. I’ll try and find it later and link it here again.
Of course the primary thing is wind noise reduction. Many great recordings have been made with basket windscreens and the internal reflection thing may not be that big of a problem in typical use. Plus there are other things to consider besides the degree of wind protection and sonic artifacts such as available configurations, mic protection, cable management, weight, cost, etc. Foam is generally far less expensive while baskets often include integrated cable management and mounting hardware for specific arrays.
What I take from all this is as guiding design principles is selecting materials with minimal high frequency loss, using the amount necessary but no more and designing the protection with the idea of
isotopy so as to be as sonically transparency in all directions as possible. I just sewed up a fur jacket to slip over a foam screen for a quite wind sensitive ambisonic mic to use at an outdoor festival next week and was very careful about tailoring it so that the base fabric of the fur presents the same ‘view’ to the mic in all directions. Because of the ‘capsules pointing in all directions aspect’ of the ambisonic mic I was particularly aware of all this and made efforts to not overlap the fabric edges, use minimal seam widths, include minimal extra fabric for the tuck, at the bottom, etc.
Topic: Wind protection options and preference? (Read 7758 times)