# How to match RMS power of Amps to speakers



## ak2366 (Dec 27, 2010)

My question is how do i match Amps to speakers in terms of RMS value, is it better to run higher RMS or to underpower your speakers and run with lower RMS. I am currently running PDX-f4 that gives out 100W per channel and i was thinking of upgrading to PDX-F6 that gives out 150W per channel..would this decision be SAFE??!

I am running the following :

(front) focal krx2 - Max. power 200W
- Nom. power 100W (2 way component kit)


(behind) Focal 165 cvx - Max. power 140W
- Nom. power 70W ( 2 way co-axial kit)


Amplifier- Alpine PDX-F4 

100 watts x 4 chan @ 2 ohms, Total RMS: 400 watts, Signal-to-Noise Ratio: 76dBA,


Alpine PDX-F6 

150 watts RMS x 4 at 4 ohms (150 watts RMS x 4 at 2 ohms)


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## The Baron Groog (Mar 15, 2010)

Having more power will give greater headroom and allow the system to be louder before you hit the clipping region of the amp. It's unlikely you'll ever need all 150wrms per ch. 

Is your current set up loud enough? Why do you want more power? If you're never stressing your system atm the upgrade will likely gain you zero dfiference-except a larger hole in your bank balance.

If you find you are continuously having to knock down the volume as you hear your amps clipping then the upgrade would be worth it.


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## ak2366 (Dec 27, 2010)

The Baron Groog said:


> Having more power will give greater headroom and allow the system to be louder before you hit the clipping region of the amp. It's unlikely you'll ever need all 150wrms per ch.
> 
> Is your current set up loud enough? Why do you want more power? If you're never stressing your system atm the upgrade will likely gain you zero dfiference-except a larger hole in your bank balance.
> 
> If you find you are continuously having to knock down the volume as you hear your amps clipping then the upgrade would be worth it.


I want to change because i have had to set my gains to 1/4 (one quarter) of the dial because when i increase the volume from my head unit i get distortion very quickly. System is actually loud and okay but i have to crank my pioneer AVH-4300 to volume 25-30 /40 ( 40 is the highest volume on head unit). I was just wondering why i have to increase head unit volume so high and if that is safe for the HU. But i have gone low on the gains because i get distortion very easily and tweeter hissss very easy whenever i go up to 1/2 or 3/4 of the Amp gains. So was looking for your opinions and advice


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## Lars Ulriched (Oct 31, 2009)

I have exactly the same question...My Vifa Pl11 is 85 RMS...would it be safe to drive it using Tru T03 4.150? Isnt that too much power for it? Will it burn the speaker? Im also thinking to change the Vifa to the PRS mid....but my worry is even more becos the PRS mid is just somewhere below 50 RMS (not sure about this)....


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## The Baron Groog (Mar 15, 2010)

ak2366 said:


> I want to change because i have had to set my gains to 1/4 (one quarter) of the dial because when i increase the volume from my head unit i get distortion very quickly. System is actually loud and okay but i have to crank my pioneer AVH-4300 to volume 25-30 /40 ( 40 is the highest volume on head unit).


Is it loud enough? If yes then no need to buy another amp




ak2366 said:


> I was just wondering why i have to increase head unit volume so high and if that is safe for the HU. But i have gone low on the gains because i get distortion very easily and tweeter hissss very easy whenever i go up to 1/2 or 3/4 of the Amp gains. So was looking for your opinions and advice


That's safe for the HU and your amps (providing the HU isn't clipping the signal fine for your speakers too) the reason you have to crank high on the HU is becasue the gain is down on the amp, raise the gain and you'll have to turn the HU "less"-but then suffer noise floor problems!


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## minbari (Mar 3, 2011)

never been a big fan of the alpine amps, but some people love them. as for the distortion, I would say that you are hitting the wall on the HU, that is why you get distortion. with the amplifiers set to 1/4 (I have to guess that means they are set to 5V+?) so you are trying to over drive the HU to make up for the difference.

as for the noise level issue, if your amplifiers are seriously 76dB signal to noise, then that is the problem. that is a rediculous signal to noise figure.


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## ak2366 (Dec 27, 2010)

minbari said:


> never been a big fan of the alpine amps, but some people love them. as for the distortion, I would say that you are hitting the wall on the HU, that is why you get distortion. with the amplifiers set to 1/4 (I have to guess that means they are set to 5V+?) so you are trying to over drive the HU to make up for the difference.
> 
> as for the noise level issue, if your amplifiers are seriously 76dB signal to noise, then that is the problem. that is a rediculous signal to noise figure.


really? so why arent you a fan of Alpines almost everyone has something good to say about them. So please tell me what Amp are you a fan of and would personally recommend for me based on your personal experience. Now back to the Alpine amp, they specs says it has a very very low distortion here check out

Alpine Electronics of America, Inc.


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## 14642 (May 19, 2008)

minbari said:


> never been a big fan of the alpine amps, but some people love them. as for the distortion, I would say that you are hitting the wall on the HU, that is why you get distortion. with the amplifiers set to 1/4 (I have to guess that means they are set to 5V+?) so you are trying to over drive the HU to make up for the difference.
> 
> as for the noise level issue, if your amplifiers are seriously 76dB signal to noise, then that is the problem. that is a rediculous signal to noise figure.


 
It's only ridiculous if that rating uses rated power as the reference. 76 at 1 watt, which is how Alpine rates the amps and so do many other companies (according to CEA2006) isn't so bad. That's the same as 96 at rated power, for a 100 watt amplifier or 106 for a 1000 watt amplifier. This is precisely why the rating was changed to use 1 watt rather than rated power. If you use rated power, then a larger amp will always show a higher signal to noise ratio. However, no one cares how much noise there is when the amp is providing 1000 watts--you can't hear the noise when there's so much signal. Noise is an issue when the amplifier is providing little or no power (when the music is quiet), and that's why a 1-watt rating is much more useful.


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## bertholomey (Dec 27, 2007)

I saw this comment on a review site for Quad 12l home drivers. Probably not technically accurate, but might be useful. I have seen that well made speakers can play very well with amps producing well above the speakers rated power. I think there is truth in that worse things happen when users are trying to get more out of an amp then what it can cleanly produce (not stating that you are having this issue, just in general). 

"You are looking at the power the speaker can handle in the wrong way. When a speaker says it can handle 100 watts you can drive 400 watts into it no problem (as long as it's not 30hz's or something rediculas) 4,000 watts might blow it, but when you blow a speaker it's the amp that is at fault. When an amp can't handle the power it shorts out sending raw heat to the driver, this melts the driver causing your speaker to blow.

So the question is not how much can the speaker handle, it is how much can the amp handle. Most people think you should get a 60 watt amp if you get a 100 watt speaker. It is the opposite you should get a 200 watt amp for a 100 watt speaker. If you send more wattage to a speaker than it can handle it will not get any louder. The speaker cannot go any louder."


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## Brian Steele (Jun 1, 2007)

Andy Wehmeyer said:


> It's only ridiculous if that rating uses rated power as the reference. 76 at 1 watt, which is how Alpine rates the amps and so do many other companies (according to CEA2006) isn't so bad. That's the same as 96 at rated power, for a 100 watt amplifier or 106 for a 1000 watt amplifier.



The PDX-F4's S/N is actually rated at 95dB (1W into 4 Ohms)
according to its specifications sheet.


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## Brian Steele (Jun 1, 2007)

ak2366 said:


> My question is how do i match Amps to speakers in terms of RMS value, is it better to run higher RMS or to underpower your speakers and run with lower RMS. I am currently running PDX-f4 that gives out 100W per channel and i was thinking of upgrading to PDX-F6 that gives out 150W per channel..would this decision be SAFE??!


As long as you're not running the system at so high a volume that you're hearing serious distortion from the speakers, you should be fine.

I wouldn't suggest upgrading from 100 to 150W though. that's only a 1.76dB increase. You likely won't notice very much difference.


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## 14642 (May 19, 2008)

Brian Steele said:


> The PDX-F4's S/N is actually rated at 95dB (1W into 4 Ohms)
> according to its specifications sheet.


 
Well there you go. I think the older ones had a lower rating. In any case, this is almost a non-issue.


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## 14642 (May 19, 2008)

On nother note, speaker power ratings are stated as RMS, this is stupid, as there's no such thing as RMS power. The appropriate rating, and the one that is implied in the misnomer is "continuous average". Continuous average, stated in the simplest terms would be continuous sine wave, and that's not music. Amplifiers are designed to provide continuous power and that's not music.

This is what makes this so difficult--and it is difficult if you want a straight answer. Some music more closely approaches continuous sine wave-techno, dance, rap, music that is made using synthesizers, for example. Acoustic music is nowhere close to continuous sine wave. Newer recordings that include tons of dynamic range compression also have a much higher average level-that's what DRC does. this should not be confused with data compression. MP3 doesn't inherently include DRC. 

There are two kinds of power handling for a speaker--thermal and mechanical. Thermal is reflected in the RMS rating, and mechanical ought to be reflected in the "peak" power, but sadly, it isn't. 

Furthermore, the RMS rating is often inflated in order to get people to buy speakers. A speaker that's rated at 100 WRMS, may handle only a few watts playing a continuous sine wave.

Speakers are like tires. They may be rated to deliver 40,00 miles and they may under specific conditions. Depending on how you drive, you may get fewer miles. 

My suggestion? Hmmm...it's all guesswork. Just buy the amp that looks nice and is easy to use. If you want your music loud, get a big one. If not, get a less powerful one. If you hear distortion and your amp is small, then you probably need a bigger one. If you hear distortion and your amp is big, you may need better speakers. If you hear popping, raise your crossover point or get better speakers.


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## Brian Steele (Jun 1, 2007)

Andy Wehmeyer said:


> My suggestion? Hmmm...it's all guesswork. Just buy the amp that looks nice and is easy to use. If you want your music loud, get a big one. If not, get a less powerful one. If you hear distortion and your amp is small, then you probably need a bigger one. If you hear distortion and your amp is big, you may need better speakers. If you hear popping, raise your crossover point or get better speakers.


Good suggestion, though to nitpick I'd replace "big" with "powerful". There are quite a few little amps out there that can pack a serious punch .


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## 14642 (May 19, 2008)

Brian Steele said:


> Good suggestion, though to nitpick I'd replace "big" with "powerful". There are quite a few little amps out there that can pack a serious punch .


Yeah, that's what I meant. Thanks for the clarification.


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## BuickGN (May 29, 2009)

bertholomey said:


> I saw this comment on a review site for Quad 12l home drivers. Probably not technically accurate, but might be useful. I have seen that well made speakers can play very well with amps producing well above the speakers rated power. I think there is truth in that worse things happen when users are trying to get more out of an amp then what it can cleanly produce (not stating that you are having this issue, just in general).
> 
> "You are looking at the power the speaker can handle in the wrong way. When a speaker says it can handle 100 watts you can drive 400 watts into it no problem (as long as it's not 30hz's or something rediculas) 4,000 watts might blow it, but when you blow a speaker it's the amp that is at fault. When an amp can't handle the power it shorts out sending raw heat to the driver, this melts the driver causing your speaker to blow.
> 
> So the question is not how much can the speaker handle, it is how much can the amp handle. Most people think you should get a 60 watt amp if you get a 100 watt speaker. It is the opposite you should get a 200 watt amp for a 100 watt speaker. If you send more wattage to a speaker than it can handle it will not get any louder. The speaker cannot go any louder."


That is one of the all time worst bits of info I've ever seen on the internet.


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## minbari (Mar 3, 2011)

Andy Wehmeyer said:


> It's only ridiculous if that rating uses rated power as the reference. 76 at 1 watt, which is how Alpine rates the amps and so do many other companies (according to CEA2006) isn't so bad. That's the same as 96 at rated power, for a 100 watt amplifier or 106 for a 1000 watt amplifier. This is precisely why the rating was changed to use 1 watt rather than rated power. If you use rated power, then a larger amp will always show a higher signal to noise ratio. However, no one cares how much noise there is when the amp is providing 1000 watts--you can't hear the noise when there's so much signal. Noise is an issue when the amplifier is providing little or no power (when the music is quiet), and that's why a 1-watt rating is much more useful.


got it. ya 96 or 106 is more what I am used to seeing.


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## bertholomey (Dec 27, 2007)

Thanks Buick for the reminder to stay in my lane and not provide unsolicited information (or miss-information). OP - disregard my post, and good luck with your system.


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## BuickGN (May 29, 2009)

bertholomey said:


> Thanks Buick for the reminder to stay in my lane and not provide unsolicited information (or miss-information). OP - disregard my post, and good luck with your system.


I didn't mean that toward you at all. I thought the post you quoted was a joke lol.


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