Re: What's really the best way to "bedroom-ize" my peavey 6505+???
Assuming we're talking about getting a distorted sound (and there are good reasons to crank an amp that have little to do with anything most of us would call dirt/crunch/etc), you've got four things at work in a loud amp:
1) preamp tubes distorting
2) Power Tubes Distorting
3) Speaker cone(s) distorting -- this varies a lot by speaker model
4) the way your ears/brain process sounds of differing volumes.
Dropping the Master and cranking the Pre is one way to get a distorted sound quietly, and can be a GREAT sound, but it's a totally different sound to what that amp will sound like on 11, because you're taking out steps 2,3 and 4 up there.
Adding an attenuater gives you Step 2 back, but still leaves out 3 and 4.
An iso box will let you get 1, 2 and 3 into a mic, which then (eventually, at the end of a potentially long signal chain) is played back through headphones or monitors at a low level , which, because of both the mic/mixer/monitors/etc and Step 4, will make it sound different than you're used to hearing when you just crank it normally.
So if you want it to sound the same, only quieter...you're boned. But you can get some good sounds using those other techniques.