Steve Thomas Posted October 10, 2010 Share Posted October 10, 2010 I currently have a (new) pair of 8ohm 12" full range speakers that are spec'd at 750w 8ohm's. My amp currently puts out 400w at 8ohms. Will I be doing any damage to either the speakers or (more likely the amp). The application would be stage monitoring for vocals/live music. Until I can upgrade the amp is it advisable to not use this configuration. Thanks Link to comment Share on other sites More sharing options...
widowgobo Posted October 10, 2010 Share Posted October 10, 2010 so long as you dont clip the amp, no problem. Link to comment Share on other sites More sharing options...
TonyMitchell Posted October 10, 2010 Share Posted October 10, 2010 The difference between feeding them 400w and 750w only amounts to ~-2dB reduction in output, which is insignificant. To reiterate what's already been said, ensure you don't clip the amplifier and be aware that you have very little headroom, then you should be just fine. Link to comment Share on other sites More sharing options...
Jivemaster Posted October 10, 2010 Share Posted October 10, 2010 IF you drive the amp to clipping then (as clippling usually adds lots of HF noise) you will likely blow the treble units. In most cases the answer is to listen to the sound, if the speakers are complaining you will kill them, if the sound is sweet and undistorted then they should have a normal life. Link to comment Share on other sites More sharing options...
dboomer Posted October 10, 2010 Share Posted October 10, 2010 "Underpowering" speakers will NOT damage them and clipped signals (as a waveform) will not damage speakers. Speakers are damaged because they receive too much power (either average or peak or both) or by exceeding the mechanical limitations (over-excursion). They don't care about waveform. Understanding exactly how much power your speakers can handle might be a different problem as the number means different things from different manufacturers. this explains it in more detail ...http://www.peavey.com/support/technotes/po..._MUCH_POWER.pdf Speakers put out about 95% of their maximum capability with about 50% of their rated power. More power means shorter life and increased distortion. Link to comment Share on other sites More sharing options...
Stan Hope-Streeter Posted October 10, 2010 Share Posted October 10, 2010 Underpowering speakers will NOT damage them and clipped signals (as a waveform) will not damage speakers. Speakers are damaged because they receive too much power (either average or peak or both) or by exceeding the mechanical limitations (over-excursion). They don't care about waveform. This is true of an individual drive unit, but you are forgetting what happens in a speaker (system) with a passive crossover. The tweeter is only rated to handle the proportion of system power that is expected in normal use, which is a lot less than the overall rated power.Consequently it is possible to overdrive the tweeter, and perhaps damage it, at levels which will cause no harm to the low frequency unit. A signal with an unusually large proportion of high frequency energy will do this. The spectral balance of the output of a heavily clipped amplifier is shifted upwards. This is because the low frequencies are clipped and limited in level whilst the high frequencies are not, and the harmonics that result from clipping also increase the relative amount of high frequency energy. That is why a clipped signal sounds "harsh" and "toppy" compared with a clean undistorted signal. Note that some musical sounds are naturally like this; square waves are part of life's rich tapestry! The output power of a heavily clipped amplifier can be anything up to twice its quoted sine wave rating (the difference between the power in a square wave and a sine wave of equal peak anplitude). In the OP's case this might be up to 800 watts; although in practice, with a sustained signal, the amplifier's power supply will limit the output to less than that theoretical figure. So whilst clipped signals (per se) won't damage the speakers, the output of a heavily clipping amplifier might well do - and even if it is within the rating of the bass driver, it could still burn out the tweeters. That's why a set of blown tweeters on the hi-fi often results from a loud house party... Link to comment Share on other sites More sharing options...
dboomer Posted October 11, 2010 Share Posted October 11, 2010 So whilst clipped signals (per se) won't damage the speakers, the output of a heavily clipping amplifier might well do - and even if it is within the rating of the bass driver, it could still burn out the tweeters. That's why a set of blown tweeters on the hi-fi often results from a loud house party... Yes ... but that is the "power" not the "waveform" As a general rule an amplifier could double its rated "average" power if you managed sustained hard clipping. This would be difficult to do with program material and easier with operator malfunction. You also have to be in a position to supply current (which IS easier on your side of the pond). In my experience it is not excessive power that kills speakers ... it's people that kill speakers. But it is never "underpowering" Link to comment Share on other sites More sharing options...
Stan Hope-Streeter Posted October 11, 2010 Share Posted October 11, 2010 In my experience it is not excessive power that kills speakers ... it's people that kill speakers. But it is never "underpowering" Hi Don, I think we are in agreement! The detail in my message was for the OP's information. It is always the power that causes the burnout, square waves are just another signal (and won't look like square waves any more, after they have been through the crossover filters). All I'm saying is that it is possible, under some conditions, to overdrive the tweeters whilst underpowering "the system" according to its ratings. Also that a heavily clipping amplifier can create those conditions - and yes, of course that is the result of operator error. Link to comment Share on other sites More sharing options...
Sound In Gloucestershire Posted October 12, 2010 Share Posted October 12, 2010 one thing that hasnt been mentioned is how unlikely it is that your speakers are genuinely 750watts RMS at 8 ohms, you sure thats not max, peak or any other rating? Link to comment Share on other sites More sharing options...
Chappie Posted October 12, 2010 Share Posted October 12, 2010 So whilst clipped signals (per se) won't damage the speakers, the output of a heavily clipping amplifier might well do - and even if it is within the rating of the bass driver, it could still burn out the tweeters.Yes ... but that is the "power" not the "waveform"Seeing as the "power" and the "waveform" are directly correlated, both posts are describing the same processes, just differing in semantics. It may well be that "underpowering" in its most literal sense does not damage components, but an "underpowered" amplifier can easily damage components, dependent on its use. I believe it to be far easier to explain to someone with little knowledge of sound system structure that as a general rule-of-thumb an underpowered amplifier is generally a bad thing, without having to describe why in too much detail, as the potential flurry of following statements can be more confusing than the original question warrants, even if they are accurate. Link to comment Share on other sites More sharing options...
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