Amp power ratings and using twice the RMS

[NCcrashman]

I, like most, have always believed that you should always buy a amp that has twice the RMS rating of the speakers (in other words, if your speakers are rated @ 400 watt's, get a 800 watt amp). I'm assuming because I have always been told that driving a amp that has too low of power will damage the drivers. After reading the Faq's, it appears I have been wrong all these years. Look at what i've learned on 1 day 80-) Anyway, what is everyone's opinion on this?

Thanks,
Crash

[Chris_Allen]

Yes, it's completely unnecessary.

The limit of the voice coil in a driver is the same irrespective of the amp. If you exceed this voltage, you will damage the driver. On the other side, drivers are also displacement limited which often occurs way below rated power.

For example, if we were to say that a driver was displacement limited at *70% of its rated power, a 300 Watt speaker would stop giving additional output past 210W. So there is no point in giving it any more power.

It is nice to have a little headroom on the power amp so that you don't have to run them on full. They won't run as hot and greatly extend the life of the product.

(*70% is just a random figure in roughly the right area, each driver has a specific displacement limitation)

[Bill Fitzmaurice]

http://billfitzmaurice.info/forum/viewt ... =10&t=1886

[SeisTres]

While there is indeed no such thing as underpowering, I still try to power my speakers with bigger amps than their rms ratings. I like the extra head room for peaks and keep the amps from ever clipping or going into protect mode. So i do aroudn 1.5x of the spekear's rms, but if i had the money, i would still probably do 2x.