What does 250W RMS (500W clean) mean?

[DGBass]

I suspect the meaning is that the cab will be ok if your amp has the clean headroom to provide a 500 watt 'clean peak'. What usually destroys speakers is the square wave distortion generated by an amp output when it is overdriven to oblivion. Back in the day, old Peavey 130 watt RMS MKIII 260C combos could generate almost 350 watts peak because of the inbuilt headroom in the amps design. Thats why Hartley put Black Widows (350 watts RMS) in his 130 watt amps to prevent them blowing up if players opted not to use the DDT compression switch. Modern amps including class D work very differently and most class d amp manufacturers rarely quote a peak 'clean' power output. I wouldn't use a BF one ten with anything more than a 250W class d amp (8 ohms). Or a 150 watt class AB amp and thats from experience. They are good cabs and sound great but the power ratings always seemed odd to me. I had two BF one tens, one was rated 200W RMS @ 8ohms and the other a few serial numbers down the road was rated 250W RMS. Both had the same custom high excursion driver so why the power rating label changed mid production was a mystery to me. Both cabs together (at 4 ohms) were fine with a class D 500W amp but with a 500W class AB amp, they really couldn't cope with peaks despite a very clean signal chain.   

 

[agedhorse]

Distortion and square waves don’t obliterate speakers any more than an undistorted signal of equivalent RMS power, and in fact is easier on a speaker mechanically.

 

A square wave of the same peak voltage as a sine wave has twice the thermal power but the same mechanical power. This is probably the root of most misunderstanding about the topic. 
 

Now peak power is something entirely different, a sine wave always has a peak power that’s double the RMS value, it’s purely two ways of using math to describe the same thing.