P.A. Amp question

[zepremains]

I know very little about this topic, here's the question:
How far can you safely under power a P.A. cabinet. Example: P.A. cabinet is rated at 400watts, knowing that underpowering is bad for voicecoils, is 300watts safe?
Any experienced input would be appreciated.
thanks

[lowenzz]

I think the key to remember is clean power, sending distortion (not the good guitar amp kind) is what kills the speakers.

I would think you could run any underpowered amps as long as it was kept clean. This would not be very loud, because you would have low headroom though.

And you need to keep in mind the whole speaker/amp watts rated at so many ohms. mono stereo and such.

[pillagethesound]

Note: I am answer in reference to PA systems not guitar rigs, im not sure if the same rule applys in low wattage amplifiers.

Its not gonna be the worst for the speakers. Its actually gonna be bad for the amp which will end up being bad for your speakers. When the speaker wattage is more than the amp output wattage you will tend to run the amp way to hot and often peak/clip the amp. Continued peaks/clips of the amp wil cause voltage peaks and fluctuations that will blow horns and sometime weld the speaker's drivers. The general rule of thumb is to at least match if not overpower your speakers. When I do large scale shows, my stage monitor amps run 1.5-2x the wattage of the monitor speaker rating. There is no risk to your speakers in doing so i assure you. PAs is generally 2x. For mains we use EV XLC 127+ line array boxes, $5000 a speaker cabinet 16 speakers a side. We overpower those guys 2-2.5x the wattage of the speakers (except the horn). I say this to explain that I overpower expensive equipement without worry so its definately the route you are supposed to go.
And like lownezz said make sure your amps can handle the ohm load. Most PA amps that are mid level can only handle down to 4 ohm, some can do 2 ohm. If it can only handle 4 Ohm do not put more than two speakers jumped together, and only one sub (in general) and 2 ohm can handle three speakers or two subs (again in general)