Timlub, I'm pretty sure you will need over 400 watts to drive an 84 db speaker to 111 db. Here's a useful web page for things like this: http://www.sengpielaudio.com/calculator-gainloss.htm take a look at the chart at the bottom of the page. |
I appologize, I had just run the numbers off the top of my head, but the formula is fact, not opinion, so 84 @1 watt 105 @256 87 @2 watts 111 @512 watts @ 84db sensitivity 90 @4 111 @ 64 watts @ 93db sensitivity 93 @8 I missed one line in figuring. 96 @16 110 @ 16 watts @ 98db sensitivity speakers 99 @32 102@64 105@128 Thanks Atmasphere, your chart is correct, but I was quoting how much power it took to achieve a 3db gain, not how much voltage it takes to double your volume. My numbers are correct with all things being equal. |
In any event-The question was about having an amp that exceeded specified wattage limits the speaker manufacturer stated. And if exceeding that predefined wattage limit would then cause harm? The answer is yes, - an amplifier rated as having wattage exceeding your speaker's capacity at full output if played "continously" would damage your speakers. BUT amplifiers typically deliver much much less wattage than full output during normal sane playback. As was already said the real problem is the sudden demand on an amp that doesn't have the "head room" to deliver the required wattage "cleanly" during short peaks or bursts in the music. If your amp is rated as a low output amp, it will be much more likely to deliver electricity (DC) to the speaker which is "clipping" as mentioned. It is this phenomena that suppsed burns up your speaker. I have also heard the limtation in the wave forms where they get cut off and demonstrate non linear highly distorted forms can also to a number on your speakers. |
Given a choice, I will take the bigger amp any day. You run less risk of damaging the speaker! A smaller amp, if overdriven, is how most tweeters in the world get damaged. In fact, if the tweeter is damaged in a speaker, the repair technician should always tell the user that the amplifier is under-powered. |
Although the conclusions and suggestions that have been expressed in this thread are generally correct, the explanations of why tweeters are commonly damaged by underpowered amps are not. Tweeters are not damaged by DC (it would be blocked from reaching them by the crossover network, if it were somehow generated in the first place), and amplifiers that are called upon to supply more power than they are capable of supplying do not output "raw electricity." What typically happens is that the amplifier will not have the ability to generate the output voltages that correspond to the peaks of high volume low frequency or mid-frequency signals. That will result in the output waveform abruptly transitioning from a gradually rising or falling sinusoidal waveshape to a flat level, until later in each cycle when the signal returns to an amplitude the amp can handle. That abrupt transition contains high frequency spectral components (frequency components) which are not present in the original music waveform. Since they are at high frequencies, the crossover network in the speaker routes them to the tweeter, which is therefore called upon to handle a greater amount of high frequency energy than a normal music signal would require. That is what does the damage. Best regards, -- Al |
