Air core are the best inductors for any inductance value. The iron core coils have a tendency to saturate at high power levels.
A simple 2-way bookshelf speaker probably isn't going to be driven to such high power levels that the inductor would saturate.
Again, you missed the point of my comments. As I said, this isn't about parts, but shoddy build quality.
"Pretty" is not the same thing as "build quality." The Yamaha uses large gauge wire leading from every X-over component. It uses a Mundorf cap and a high-precision resistor. I don't know why you guys are getting hung up on the board. That doesn't affect performance at all. It is handmade and likely hand-tested. PCB looks cleaner but it necessarily uses much thinner gauge for the traces. You would be nuts to think that the RSL circuit is better built; it's not, it's just machine-stamped.
In fact, one thing I see on the Yamaha board that I don't on the RSL board is lots of glue holding the components in place. Is it pretty, no, but I have had cases where crossover components came loose because they didn't have sufficient adhesion. The Yamaha definitely does have good adhesion. That, to me, is build quality. As for attention to detail, my guess is that the QC testing for the Yamaha speaker is well above that of the RSL speaker. I am not knocking the RSL speaker since it is much less expensive. Also, per attention to detail, the gloss finish on the Yamaha is the best I have ever seen. It's truly a mirror-like effect, no orange peeling or uneveness whatsoever.
