Well crud, kind of a damper on the holiday season, but the midrange driver on one of my F12s started buzzing. Before taking it in to the dealer, I started poking around in the specifications and learning more about troubleshooting. This may or may not be helpful to others looking to go on this same path
On some types of music I would notice what sounded like a faint scratching or buzzing from my left speaker. I noticed it during a listening session where there were trumpets prevalent in the recording. Trying to isolate if it was a particular driver, I downloaded some test tones (this website
was what I used to generate some sweep tones ) and played them back. Sure enough, at around 700-900Hz the buzzing sound came in, confirming my suspicion that it was the midrange driver since the crossover in the F12 is at 575Hz from bass-to-midrange and then 3kHz from midrange-to-tweeter.
I guess I can just chalk it up to too spirited of a listening session at some point, but I can't put my finger on a specific time, and I don't usually run the system "that hot". My receiver (Integra DTR-7.8 a.k.a. the Onkyo 805) has a respectable amplifier that was "certified for 4 ohms" back in the day so I would think it shouldn't have any problem driving the speakers. The Stereophile measurements do show the F12s at their lowest impedance as 2.9 ohms in an area the midrange would likely cover. I dunno, I don't know what to make of all of it because I didn't think the F12s need an amp more "beefy or powerful" than my current one?
Just surprised me a bit that I had a driver go out on me. I run my speakers crossed over at 80Hz to a subwoofer too, so I'm not running them full steam, full range, and I only sit about 9 feet (3m) from the speakers.
Either way, it'll be a $100+ lesson learned, but if anyone has any similar experiences, I thought I'd share the resources I used to help narrow down the potential "problem driver" in a speaker.