john_the_bass Posted December 15, 2009 Share Posted December 15, 2009 I've been sent a spec sheet for a speaker I have - listed on the spec sheet is a figure for rated power and one for musical power. Sorry to sound like a div, but rated power = peak and musical power = constant? How would that be referred to in terms of RMS power? ie if a cab is marked 300w RMS, what would that relate to? I should listen more I know. Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted December 15, 2009 Share Posted December 15, 2009 [quote name='john_the_bass' post='685153' date='Dec 15 2009, 08:34 AM']I've been sent a spec sheet for a speaker I have - listed on the spec sheet is a figure for rated power and one for musical power. Sorry to sound like a div, but rated power = peak and musical power = constant? How would that be referred to in terms of RMS power? ie if a cab is marked 300w RMS, what would that relate to? I should listen more I know.[/quote] RMS is real world power, the only figure that should be considered with either speakers or amps. Anything and everything else is marketing piffel. Quote Link to comment Share on other sites More sharing options...
john_the_bass Posted December 15, 2009 Author Share Posted December 15, 2009 (edited) Thanks Bill In relation to the below spec sheet (or the snapshot of it here), which of those figures relate RMS power - Music Power or Rated Power? That's what I'm having trouble finding a definition for. Edited December 15, 2009 by john_the_bass Quote Link to comment Share on other sites More sharing options...
razze06 Posted December 15, 2009 Share Posted December 15, 2009 I would say that the "rated power" is close in concept to "RMS power", and music power refers to the maximum peak it can handle without clipping. RMS power can be obtained by testing the speaker with a sine wave of a certain Root Mean Square power X, where X is the maximum power the speaker can take without distorting (or with a small but acceptable amount of distortion). The manufacturer here says they do the test using pink noise, which I understand is another, possibly more realistic way of testing for power rating. Quote Link to comment Share on other sites More sharing options...
chris_b Posted December 15, 2009 Share Posted December 15, 2009 Imagine if all car manufacturers had their own version of MPH. How fast would you be travelling at any time and how would you stick to the speed limit? RMS is the only constant reference. Quote Link to comment Share on other sites More sharing options...
razze06 Posted December 15, 2009 Share Posted December 15, 2009 [quote name='chris_b' post='685236' date='Dec 15 2009, 02:42 PM']Imagine if all car manufacturers had their own version of MPH. How fast would you be travelling at any time and how would you stick to the speed limit? RMS is the only constant reference.[/quote] Even there you can have a certain level of variation. It doesn't say what level of distortion was deemed acceptable when taking measurement, for example. The speaker in question has a rating value obtained using using pink noise, I understand it's often sine wave or even square waves that are used. Quote Link to comment Share on other sites More sharing options...
john_the_bass Posted December 15, 2009 Author Share Posted December 15, 2009 Well - the reason I ask is this: I took the speaker out of my Ashdown cab when it failed. I looked at it again yesterday and spotted that it had a model number and a url for the company that made it printed on the magnet. I found the spec sheet which I've posted up there, which gives the two figures for rated and music power. Now, the back of the cab is marked 300W RMS - but if (in the real world) it only has a 250W speaker in the box, then would I be right in thinking that it's not up to the job? I got pretty much blanked by Ashdown when I told them I'd only had it a couple of years and had run it for about 100 hours of the course of those two years with less than 200W being pushed through it. What I want to do is get my facts straight before telling them I think that they've fitted something into the cab that they shouldn't have done and it's stopped working. Hence trying to establish which of the figures would be the one to argue with (or conversely mean I should just leave it alone!) Quote Link to comment Share on other sites More sharing options...
razze06 Posted December 15, 2009 Share Posted December 15, 2009 I think it's a different rating. It could be that the speaker is rated at 250w by the manufacturer using their own test, but could take 300W RMS. After all, the RMS power handling is not quoted explicitly in the data sheet. Maybe asking the manufacturer of the speakers could help? I see they are italian, I'll be happy to help with any language problem Quote Link to comment Share on other sites More sharing options...
john_the_bass Posted December 15, 2009 Author Share Posted December 15, 2009 Thanks for the info, I have email Sita and asked them what the differences are - it's probably worth sending them another and asking if they think the speaker should have been marked as 300W RMS. Quote Link to comment Share on other sites More sharing options...
john_the_bass Posted December 15, 2009 Author Share Posted December 15, 2009 Right - scratch all that - I should have paid more attention to this first!! The plate on the back of the cab has the word "Power" printed, with 300W in the gap where the power rating goes. No mention is made of RMS, Music or Rated power - so I guess I have to work that out on my own! Quote Link to comment Share on other sites More sharing options...
Moos3h Posted December 15, 2009 Share Posted December 15, 2009 [quote name='john_the_bass' post='685264' date='Dec 15 2009, 03:07 PM']Well - the reason I ask is this: I took the speaker out of my Ashdown cab when it failed. I looked at it again yesterday and spotted that it had a model number and a url for the company that made it printed on the magnet. I found the spec sheet which I've posted up there, which gives the two figures for rated and music power. Now, the back of the cab is marked 300W RMS - but if (in the real world) it only has a 250W speaker in the box, then would I be right in thinking that it's not up to the job? I got pretty much blanked by Ashdown when I told them I'd only had it a couple of years and had run it for about 100 hours of the course of those two years with less than 200W being pushed through it. What I want to do is get my facts straight before telling them I think that they've fitted something into the cab that they shouldn't have done and it's stopped working. Hence trying to establish which of the figures would be the one to argue with (or conversely mean I should just leave it alone!)[/quote] The trouble you will also have is that it's possible to damage a speaker with a rating of 300w, by only giving it 200w. Your ears would have told you, but underpowering can be just as deadly as overpowering! Good luck though - hope it works out for you! Cheers, James Quote Link to comment Share on other sites More sharing options...
john_the_bass Posted December 15, 2009 Author Share Posted December 15, 2009 Why's that James? I am a bit ignorant when it comes to these things! What happens if you underpower a speaker? It always sounded alright to me. Surely a company wouldn't make a product which isn't suitable to be used with one of it's other products without saying so?! Quote Link to comment Share on other sites More sharing options...
Moos3h Posted December 15, 2009 Share Posted December 15, 2009 Hi John, Someone with vastly more knowledge than me can help better here (and correct me if I'm wrong!), however it is very possible that by over-driving an amplifier that it can induce DC clipping and fry the voice coil- less likely in big, brutish speakers like we're talking about, but still possible. The graunching, crunchy sound that comes when you push the speaker in and out manually is often a good indication of voice coil damage as it can actually melt! That said, I think if you were clear that you analyze your sound carefully and didn't hear any distortion etc. then no-one is likely to complain that the speaker 'only' saw 200w when capable of taking 300w. Cheers, James Quote Link to comment Share on other sites More sharing options...
john_the_bass Posted December 15, 2009 Author Share Posted December 15, 2009 Cheers James - yeah it's definitely the coil that's gone as the crunchy sound is present when the cone is being pushed in manually. I always used this cab with my ABM300 head - I reckon it was pushing between 150 - 200W at 8 ohms and it was always clean and clear (except when I used a bit of fuzz or the dirty setting on the amp) when a clean tone was used, no distortion at all. Quote Link to comment Share on other sites More sharing options...
chris_b Posted December 15, 2009 Share Posted December 15, 2009 [quote name='Moos3h' post='685308' date='Dec 15 2009, 03:42 PM']....The trouble you will also have is that it's possible to damage a speaker with a rating of 300w, by only giving it 200w. Your ears would have told you, but underpowering can be just as deadly as overpowering!....[/quote] Not true. You cannot damage a speaker by under powering it! Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted December 15, 2009 Share Posted December 15, 2009 [quote name='john_the_bass' post='685184' date='Dec 15 2009, 08:59 AM']Thanks Bill In relation to the below spec sheet (or the snapshot of it here), which of those figures relate RMS power - Music Power or Rated Power? That's what I'm having trouble finding a definition for.[/quote] RMS will be the smallest figure, the one that many manufacturers would prefer not to reveal at all. BTW, that driver will be next to worthless for electric bass, 2mm xmax means it will fart out in the low end with no more than 50 watts input, making the thermal power rating rather moot. I wouldn't consider a driver with less than 4mm xmax. [quote]The trouble you will also have is that it's possible to damage a speaker with a rating of 300w, by only giving it 200w. Your ears would have told you, but underpowering can be just as deadly as overpowering[/quote]Speaking of piffel... Absolutely, positively untrue. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted December 16, 2009 Share Posted December 16, 2009 [quote name='Bill Fitzmaurice' post='685416' date='Dec 15 2009, 05:00 PM'][quote]The trouble you will also have is that it's possible to damage a speaker with a rating of 300w, by only giving it 200w. Your ears would have told you, but underpowering can be just as deadly as overpowering[/quote] Speaking of piffel... Absolutely, positively untrue. [/quote] First bit is sort of ok isn't it? You can break a 300w rated speaker with 200w, if that 200w is low enough to drive it past excursion limit. The under powering being damaging is the wrong part. If you are feeling voice coil rub, it has probably become distorted from becoming too hot, ur hitting something (thermal damage or mechanical damage). Quote Link to comment Share on other sites More sharing options...
Metal-Mariachi Posted December 23, 2009 Share Posted December 23, 2009 In amp rating, both Traynor and Ampeg measured the out put just before clipping to get the RMS, Max is the maximum the amp will put out. In speakers it is pretty much the same RMS= max signal before the speaker begins to break up, and max is the total amount you can push before damage. MM Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted December 23, 2009 Share Posted December 23, 2009 [quote name='Mr. Foxen' post='686219' date='Dec 16 2009, 07:20 AM']You can break a 300w rated speaker with 200w, if that 200w is low enough to drive it past excursion limit.[/quote] Not likely, you must exceed xlim to cause damage, not xmax. But an amp rated 200w at 1% THD may hit 400w at 10% THD, and that could exceed both xlim and Pe. [quote]In amp rating, both Traynor and Ampeg measured the out put just before clipping to get the RMS, Max is the maximum the amp will put out.[/quote]Amps are measured at a specific THD percentage, using Root Mean Square voltage. Clipping is not part of the equation. [quote]In speakers it is pretty much the same RMS= max signal before the speaker begins to break up, and max is the total amount you can push before damage.[/quote]Speakers are thermally rated according to specific EIA procedure, using power quantified by said Root Mean Square voltage. Quote Link to comment Share on other sites More sharing options...
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