In many cases i see topics about too small spkr for the room volume.

But, what's happen when spkr & Receiver are TOO BIG for the room ?

Ex: 8 x 10 room with M80 & EP500 (extreme example)w/ampl 200w.

You wouldn't use the volume knob much, that's for sure.

Seriously, I think placement might be a big problem.

The listener becomes a crack feind!

Or the room will become cracked.

Within reason, I don't know if there is a too big for the room. As Alan Lofft has said in other posts on the forum, speakers move air. My non technical take on speaker size is that, a larger speaker in a small room will sound great because you don't have to turn it up as much to have the same impact as a smaller speaker played louder in the same space. Also, you will probably change residences at some point and you may be able able to afford a bigger space. If you have large speakers already, you won't have to upgrade.

As far as amp power versus sound level, a 200w amp is not twice as loud as a 100w amp; the volume to power gain ratio is logarithmic. For example, to play twice as loud an amp would have to have 10 times the power. What a more powerful amp will get you is more clean headroom. If you listen to a movie soundtrack or music with a lot of dynamics, a well designed more powerful amp will handle the peaks better (with less compression and distortion).

All things being equal, if you have the money to spare, to me, bigger is better. Most of us have to compromise and balance what we can spend on the components that make up our systems (bigger speakers, versus better amp versus better source, etc.). Everyone is going to have a different take on this but I have always preferred tower speakers and higher powered amps even when I lived in a 12 x 12 room.

Aside from a bit of waste in under utilizing a more powerful speaker, I'd say volume is volume. 85db from a small speaker is 85db from a big speaker.

Caveats:
- Some large speakers work better at lower volumes than others while others seem to sound better at higher volumes.

- Larger speakers often tend to produce lower frequencies better. Size matters for LFE. LFE travels through walls and ceilings much easier than higher frequencies so it might create an illusion to your neighbor that the same db level is louder than if you used smaller speakers. However, since you included a sub in the equation, that will make more difference on the low end than the speakers and it's the sub that will give you the angry neighbors regardless of main speaker size.

You mean its ok to put M80s in the bathroom? I was worried for a second there.

Just be careful when you drill holes for the toilet paper holder.