Risk using amp Wattage than speaker rating?

Rtrauthwein,

The wattage rating is the maximum wattage a speaker can handle before they burn out,
and has nothing to do with the Fidelity limit per wattage limit!

30 watts rms is all that most speakers can handle without causing distortion to the audio signal.

Why would you want to drive a speaker at 300 watts any way?

A distortion lesson...

A customer in Holland was having P.A. speakers blown out even when they were operated under the maximum wattage rate.
This speaker was damaged by having the spider separate from the cone after 2-3 days of use.
We did a frequency sweep on a new speaker to see where the cone would put out less acoustic energy.
By plotting the speakers output with a Microphone-amplifier then to a Vdc converter we could see at what frequency the speaker cone was frozen-mechanically due to cone surface aberrations.

That is, one part of the speaker was traveling in a different direction causing, in this case, enough force to rip the voice coil off from the cone. Speaker in use was a 12 inch woofer with 7 inch long slope to the spider.

The mechanics is then: Frequency of ~975 Hz, Feet = 1.17 and inches = 14.01:
7 inches one one side 7 inches up the other side of the cone center
- half of the woofer was going out the other half moving in.

This twisting motion tore the speaker apart at 23 watts input.

Distortion is our point here, anything over 30 watts into a speaker develops distortion, which is far above the Fidelity limits of most Speakers.

100 watt, 300 watts; if you want noise you will get it -
just as long as your speaker does not burn out !

That just sounds like a poorly engineered driver. That thing would tear itself apart eventually even at moderate levels. The main concern in over driving a speaker is exceeding it's X-Max rating.

Sounds more as though they were trying to produce low bass freqs, in a pro environment, with a 12" driver. Too much EQ, too small a driver, and(as Mr C intimated)exceeded it's X-Max. 12" make good mid-bass drivers, in pro applications. 30 Watts is virtually nothing, in a pro setting.

08-23-12: Cjl
>The wattage rating is the maximum wattage a speaker can handle before they burn out, and has nothing to do with the Fidelity limit per wattage limit!

To be pedantic it's a thermal limit if you feed the speaker pink noise (equal power in each octave) with a 6dB crest factor (difference between peak and average) with a 50Hz second-order high-pass and 5KHz second-order low-pass.

With about 7 octaves in that range the tweeter is seeing about 1/7 of that power and more than 30W of high frequency energy into a 200W rated speaker could fry it.

You can also reach the mechanical limits at much lower power levels at low frequencies.

Output at the maximum linear excursion into full space for various representative drivers at 3 feet is as follows at 120, 80, 40, and 20Hz. Mechanical limits are often 6dB higher although you can still run out with just a few Watts.

Size Driver Sd (cm^2) x xmax (mm) 120Hz 80Hz 40Hz 20Hz
4 1/2" Seas W12CY001 50 x 3 89dB 82dB 70dB 58dB
5 1/4" Peerless 830873 88 x 3.5 95dB 88dB 76dB 64dB
6 1/4" Seas L16RN-SL 104 x 6 101dB 94dB 82dB 70dB
7" Seas W18EX001 126 x 5 102dB 95dB 83dB 71dB
8.5" Seas W22EX001 220 x 5 106dB 99dB 87dB 75dB
10" Peerless 830452 352 x 12.5 118dB 111dB 99dB 87dB

>Why would you want to drive a speaker at 300 watts any way?

Nice jazz recordings yielding a pleasant 85dBC at the listening position can have listening position peaks of 103dB from each channel that could be 110dB at the speaker with 7dB of loss due to distance.

Although less than 3W RMS with a 85dB/1W/1 meter speaker that's 300W peak.

Of course, consumer power amplifiers are rated with a 3dB crest factor so an amplifier rated at 150 FTC Watts would do a fine job in that situation.