Originally Posted by mtn-tech
There have been many discussions on AVS about power handling, power ratings, and blowing drivers - the consensus is that only one thing blows up speakers: too much power.
If you are really cranking the volume until your amplifier starts clipping, it can actually put out significantly more (distorted) power than its rating - and that is what can blow your speakers. You should consider getting speakers with higher power rating - something with high sensitivity with high max SPL (high max volume) - maybe JBL or some other PA speakers.
I don't think we can make that assumption here. We should gather the data that I requested first.
I suspect that he's clipping his amp - yes, but firstly, he should stop clipping his amp because clipping can kill most any size, consumer voice coil. In the wattage range that he's provided, heavy clip could take them out, well under 30-minutes. Plus clipping is a direct enemy of fidelity.We need to gain an idea of his wattage.
If his speakers are rated in the 150 Watt range, he really shouldn't be putting much more than 75-Watts RMS into them anyway, we need data to be of any real value to him. Let's not just tell him to go buy a bigger amp, let's educate him on as many levels as he will permit. If his amplifier proves only to be 100-watts per channel (in theory), I would wager a large sum of money that he has less than 70-watts of actually usable power (under 1%THD).
In the spirit of that thought:
Clipping occurs when the amplifier power supply rails, run out of current, which causes the peaks of the transits to truncate and flatten out, over several degrees of a transit, which in turn increases the applied current to the voice coil, in a fashion similar to applying direct DC. The EIA standards for rating thermal tolerance of Voice coils, is base on pure AC tone bursts, not highly distorted clipped tones that resemble square waves more than a sine wave. The DC thermal tolerance of a speaker is often a mere 25% of it's EIA rating. In heavy clip, say a state that truncates 180 degrees of a transients wavelength: a 100-Watt/channel AVR would be able to burn most VC's in under 30-minutes, with ratings of 200-watts and under. Higher Wattage speaker would also fail, but it would take longer. Even a 400 Watt- VC would fail with a DC like input of 25-Watts, it would likely not last an hour. Heap on some bass boost and moments of current recovery creating peaks and these time can be cut in half.
99% of the time, RMA's relating to VC death are due to an amplifier being pushed beyond their intended range of operation, placing them in a state of being insufficiently heeled in current. Current is the root of Wattage. When the Voltage collapses, the waveform collapses and becomes less alternating and more of a direct current, when this occurs, the driver start to effectively receive DC. Once 500ms of a waveform has collapsed it's full burn time.
He may also be experiencing DC-offset issues, which will continue to burn VC's regardless of output levels.
Once we have the answers to the questions that I have requested, the field of assumptions will be narrowed.
PS Can you send us pictures of your burnt drivers?