Blown Tweeter & midrange fuses Magnepan 3.6r

" open floor plan " this means your room is even larger than 15'x20'. Another thing to know is that your type of speaker does not sound as loud as you guess it is...a spl meter will show you this.

I don't know your Krell amp but I do own a couple of Krell's. My baby Krell (Kav-500) is rated in the same ball-park as yours at 240 watts/4 ohms. The power supply in these little Krells is not enough for your speakers. I have tried mine with my 4 0hm. Apogee Duetta Signatures, while it will play them and sounds very good...high spl's cause it to run out of steam very quickly.

I use a Krell Ksa-250 with my Apogees in my 25'x23' room, it has over 4 times more reserve for those loud moments (which don't sound that loud).

Dave

400+ watts into 4 ohm, pull the speakers out into the room. If you are watching movies this will happen even more so with this few watts.

I use a spectron Musician II amp that puts out 650 watts per channel. I can still blow fuses in my 3.6's at high volume intervals. I can only crank up to about eleven o'clock on the volume without having to replace fuses. i believe that excesive volume on any amp with cause your Maggies to blow off. I have found that using an amp with more clean power doesn't elliminate the problem that you've outlined here..........

Something isn't right about this picture. I've had over a dozen amps with my 3.6's and never blew a midrange fuse, despite playing quite loud (85db with 95db peaks measured on a RS SPL meter)and despite having a room over twice the size as yours. I suspect your definition of 'somewhat moderate' is compatible with my 'very loud'. You need to get an spl before you do anything else, measure what you think is moderate and go from there. You may find these speakers are not for you, they are not really designed for very high spl's. Incidentally, I used a Krell FPB 200 with 400w into 4 ohms and never blew a fuse in the 3.6

The problem with these speakers is that they play extremely clean with no sign of breakup. They really just start sounding good (to me) at 95db as I recall. At somewhere around that point, most amps run out of headroom, or perhaps there is a finite point to the amount of current they'll take. And then, zap goes the fuses and the tweeter (which makes little sense to me since the fuse should protect the tweeter from getting too much current whether the amp is clipping or not).
Don't get me wrong, I love the sound of these speakers and even sold them for an audio store twenty years ago, but to my mind, the 3.6s must have a flaw, since I owned the MG-IIIs for 15 years and never blew out a tweeter with the same equipment.
Magnepan was mistified and could not help me solve the problem, so I sold the speakers and bought a pair of Revel Salons.
There are times I'm tempted to try the Maggies again, (I loved the Typani 4s) but will stay away until Magnepan addresses these problems. With the high end equipment that I've owned (even biamping them) those tweets and fuses should not be a concern.
My advise is to look elsewhere for speakers as you will not get the volume you appear to like without many heartaches.