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question about RMS ratings...

Old 01-28-2009, 05:33 PM
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question about RMS ratings...

ok guys, heres a question that i've been thinking about for quite some time but have never really be able to figure out. i know on most subs they're rated with rms and peak or max, so for instance the incriminator audio lethal injection 12'' can take 600 rms and 1200 watts max. that part i got and can understand. i also know that sending more than the rms to a sub can cook it. now i've heard that underpowering a subwoofer can damage the voice coil as well (whether or not this is true i don't know only because i figure volume plays a role is power, so someone who likes low volume could blow the sub just as fast as someone who played it a full volume).

my question then is, what about subwoofers that claim to have rms ratings with a range instead of dead on figure, for instance the sound splinter RL p-12 claims an rms rating of 500-1000 watts. so for me with an amp that can put out 1250 watts rms, two IAs seem to be the more accurate choice, but the sound splinters would also be a good choice because i would be able to pump between 1000 and 2000 watts rms to them, even though 1250 falls into the lower part of the spectrum.

sooo, i guess this a two parter. 1 is can you blow a sub with less than rms to it? and 2 how do you power a sub with a range of rms handling values?
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Old 01-28-2009, 05:56 PM
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when people say that low power can be more dangerous for speakers, it's because most people with low power amps or receivers tend to turn the volume up too much and this creates distortion(not enough power to amplify the signal) which can damage the speaker. Lower power than the RMS of the speaker can not damage the speaker. If that were true, then everyone would blow speakers every time they turned the volume down. As far as the RMS range, some powerful subs and speakers like to give a range that the speaker works best with. Some subs in particular employ very stiff surrounds, or spiders, and low power just doesn't motivate them as well.

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Old 01-28-2009, 06:38 PM
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that 500rms-1000rms rating is stating 500rms per voice coil. the RL-p is rated for 1000rms but can deffinatly take more.

as far as damaging a sub with less RMS... no. but you can clip the outta the signal using bass boost and boosted gains.
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Old 01-28-2009, 07:55 PM
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Efficiency comes in to play as well and that's part of the reason the manufactures sometimes give minimums, but sound quality is another. Related actually.

If you feed a sub rated 500 to 1000 RMS a lowly 200 watts it will probably make some sound, but then you would go around the rest of your life saying "brand x" subs sound like , when in reality you were barely feeding it enough power to tickle it.

100% agree with the others on why under powering can be bad.

John
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Old 01-28-2009, 08:21 PM
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Originally Posted by jalat View Post
that 500rms-1000rms rating is stating 500rms per voice coil. the RL-p is rated for 1000rms but can deffinatly take more.

as far as damaging a sub with less RMS... no. but you can clip the outta the signal using bass boost and boosted gains.
the 500 per voice coil makes sense Mike, but what about a sub like the RF p2 that says 50-250 rms? doubling the voice coils just brings it to 100, but thats less than half 250 rms you can (or should) give it.

Originally Posted by John__Taylor View Post
Efficiency comes in to play as well and that's part of the reason the manufactures sometimes give minimums, but sound quality is another. Related actually.

If you feed a sub rated 500 to 1000 RMS a lowly 200 watts it will probably make some sound, but then you would go around the rest of your life saying "brand x" subs sound like , when in reality you were barely feeding it enough power to tickle it.

100% agree with the others on why under powering can be bad.

John
i understand when taking to account what Mike said about clipping with bass boosts and such, but if you were to set all gains as you would on a regular sub but just power it with a smaller amp and then not send it the rms it could handle, even while thinking it sounds amazing, could you still cook it because you are sending 100 rms when its rated for 300?
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Old 01-28-2009, 08:24 PM
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I suppose that the most common headache for most people in sales, is trying to explain specifications to a client. (which is most all cases mean diddly)
Since a manufacturer has to publish specifications for their products, many will use various methods to achieve respectable specifications in order to sell THE MOST PRODUCT.
So, say you buy a speaker that is rated at 1000Watts Peak(max) and 700RMS (being that Root Mean Square is .7071 of Max)
We now must find out which method was used EI rating or DIN ?
Either way both are close enough not to cause too much of an argument.
So the manufacturer is saying that it's product will operate best under those conditions, anything beyond those specs may damage it, and void warranty.
Most all products will meet or exceed the posted specs, as an example, I tested an 18" guitar speaker rated for 150w., and eventually managed to put 1,800 watts into it, on a Peak, for a brief moment with no problems to the voice coil, This was dependant on the FREQUENCY the driver was producing, which was approx 50Hz.
Now, having said that, I could have blown the voice coil with 1 watt of distorted power. So it's not Lack of power that blows a speaker, it's when an in-adequate amplifier is pushed into distortion that you will always damage a speaker.
Equate this to a 4 cyl. and 8 cyl. car doing 60mph up hill carrying a trailer, one of them will have to work much harder to keep up, and probably burn oil(distortion).
The main reason I don't bother with most specifications is because I don't listen to test tones, and I don't have an anachoic chamber, and because my alarm clock radio has respectable specifications enough for my HUMAN ear.
Enjoy your music, if it sounds good, be happy.
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Old 01-28-2009, 10:13 PM
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Originally Posted by fresh1 View Post
ok guys, heres a question that i've been thinking about for quite some time but have never really be able to figure out. i know on most subs they're rated with rms and peak or max, so for instance the incriminator audio lethal injection 12'' can take 600 rms and 1200 watts max. that part i got and can understand. i also know that sending more than the rms to a sub can cook it. now i've heard that underpowering a subwoofer can damage the voice coil as well (whether or not this is true i don't know only because i figure volume plays a role is power, so someone who likes low volume could blow the sub just as fast as someone who played it a full volume).

my question then is, what about subwoofers that claim to have rms ratings with a range instead of dead on figure, for instance the sound splinter RL p-12 claims an rms rating of 500-1000 watts. so for me with an amp that can put out 1250 watts rms, two IAs seem to be the more accurate choice, but the sound splinters would also be a good choice because i would be able to pump between 1000 and 2000 watts rms to them, even though 1250 falls into the lower part of the spectrum.

sooo, i guess this a two parter. 1 is can you blow a sub with less than rms to it? and 2 how do you power a sub with a range of rms handling values?


Also remember that once a subwoofer is put into an enclosure that is outside of recomendation the power handling most likely goes to hell and also the impedence curve changes which just might blow the hell out of your amp!
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Old 01-29-2009, 01:30 AM
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Eli makes a tremendously good point (or more). So...your 6" mids are rated at 150 WRMS and specs say they go as low as 50Hz..hmmmm. Give that a try and tell me how it works out for you

I currently have the front mids H/P at 100 and sometimes I change to 125. They are getting over 200 WRMS per side (closer to 250). If I tried that at say 60 Hz I suspect they would last about 2 seconds.

Heres another point of interest. I had a different set of fronts, different amp putting out around 100 WRMS per side. Speakers were rated for 150 I think (RMS) and I had them passed at 100, amp gains were easily less than 50%

I was being dumb at the time. Couldnt resust going "just a little more" on the volume (I was new..what can I say) I heard about 2 seconds of distortion and before i could reach the head unit, POOF, smoke out of the door panels.

So I guess what I'm saying is that in my stupidity, I have actually proven the answer to your question

John
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Old 01-29-2009, 08:57 AM
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John_Taylor, don't forget about the filter's slope though. If you have a 12 or 24dB slope on a HPF, you wouldn't be amplifing those lower frequencies with a full 150W (or whatever one's amp outputs).

I prefer having less volume and allowing my MB Quart reference to dip into lower frequencies than most people would allow. It sounds better, to me, anyway. Though, with the Alpine deck I have, I'm able to cross-over at 80Hz, and change the slope to one of four options. The slope I use is 2nd least steep, so it doesn't cut the lower frequencies off too fast. The amp's gains are set at about 1/5th of full. HPF on the amp is at 60Hz. Obviously, I'm letting the head-unit do my filtering for me.

I always believed that the RMS range that certain brands apply to their speakers was the range of power that would yield "proper" sound from that particular speaker.
Anything below that range, and I think it's too little power to even get the speaker to "work" to reproduce the signal being sent to the amp, and anything above that range, and you're working the speaker too hard.

Keep in mind that you're rarely sending 600W from a 600W amplifier. And if you do, its only for a very short period of time, unless you're listening to test tones or something similar. So if your sub had an RMS of 500W, a 600W amplifier wouldn't pose too much of a threat if set up properly.
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Old 01-29-2009, 01:02 PM
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Power is one of the most confusing ratings on subwoofers. It doesn't help that most call them "RMS Power" ratings, when in fact there is no such thing.

A driver can be damaged either mechanically (parts smashing together or being pulled apart) or thermally (the coil or leads melting). These two conditions can only come from too much power over a given period of time. It is important to note the relation between the two: A driver may be able to take 10 kW for 1/2 second, but it might be hard pressed to do so for half an hour.

The power delivered to the driver by your amplifier also depends on the crest factor of the signal; music, with its lower crest factor, will not require that the amplifier deliver its full rated power, and if it ever does, it is usually for a very short duration. Sine waves have a lower crest factor than most music does (at 3 dB), and so it carries significantly more power. A fully clipped square wave has a crest factor of 0 dB, so these are the most powerful signals you can send your driver. It should be noted that there is inherently damaging about a clipped signal....it only becomes a problem when you turn up the volume and the driver receives more heat in a given time frame than its mass can hold.

The frequency of the signal also plays a role, although in subwoofers it is more significant in the mechanical realm than the thermal one.
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