# Under and over powering speakers and it's affect on SQ?



## eso6686 (Apr 27, 2011)

Hi,

I would like to know the effect of under power or over powering a speaker and it affect on SQ.

I know loudness will be different and maybe a bit more distortion on the amp set because it is working so much hard to amp the signal.

But lets look at this example and tell we what the effect is on overall SQ at the same middle volume..not too soft and not to loud.

A pair of speakers rated at 100rms and 200 watt max

1. Running it with 50 watt rms?
2. Running it at 100 watt rms?
3. Running it at 150 watt rms?

Under normal hearing volume (NOT SPL) and enviroment.
Lets pretend there is not clipping and the distortion ratio is the same accross all 3.

Will there be a difference in the overall SQ? EX speaker response..etc


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## Pataforce8 (Feb 21, 2011)

My guess is that at normal listening levels, you won't hear a difference between the three. However, the 50 watt amp (assuming they're all the same class) should run a little more efficiently. It will most likely be putting out a slightly dirtier signal, but you won't hear it. You WILL hear it if you decide to turn it up though.


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

Volume and/or gain is not linear... so as stated above, at "normal" listening levels the difference isn't going to be great, although the 50w amp will be working a little harder and the 150w amp will hardly be awake.. 

Again as stated above, as you push it, the 50w amp will run out of steam WAY faster than the 150w amp... 

This lends itself to dynamics... the "50w amp running 100w components" won't have any headroom left at "full" volume, it's all already used up in essence... 

That "150w amp running 100w components" would still only be starting to maybe break a sweat as the 50w amp is falling apart...


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## rommelrommel (Apr 11, 2007)

The only way to "overpower" a driver is to run it past it's limits, mechanical or thermal. You can have 2000 watts a channel and not blow a speaker. 

You can't really "underpower" a speaker either, although you can not have enough power to drive it to it's limits.


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## Dremgragen (Jul 14, 2008)

I agree with above posters.

I run 235w rms to my 120w components. They love it and I love them. We're a happy family.

I feel like SQ improves, moreso at high volume than low volume (and I mostly listen high volume). I can't prove it though.


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## Pataforce8 (Feb 21, 2011)

^^ I'm running 100 watts RMS to my 60 watt speakers and they take it no sweat. I feel like it helps with the transients to "overpower" a speaker a little.


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## 60ndown (Feb 8, 2007)

eso6686 said:


> I would like to know the effect of under power or over powering a speaker and it affect on SQ.


its the same as an under or over powered car.

under powered is no good at all, 

over powered is great (as long as your careful)


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## computerjlt (Nov 29, 2010)

what i've noticed when you "underpower" a driver you get clipping/distortion/artifacts from the amplifier that make the sound bad way before the driver reaches its limits, so running a more powerful amp will make that particular driver more happy. at the same time most well built drivers can handle more power than they're rated for before they get too unhappy, especially if you have them crossed at a good frequency.

the way my system is setup i have about 3-4x more power per channel (3 way active) than the drivers are rated for so my gains stay super low making the noise floor a little lower and that way i have almost NO WAY to clip an amp before i reach the limits of a driver. 

i like having more power than is necessary for that reason; if you run an amp to clipping it can damage a driver faster, i think, than just slightly overpowering a driver; but at the same time my ears are sensitive to hear when a driver is being pushed to hard and i'll back off.

so my advice is get more amplifier than you really need


/edit: my example was mainly for my midrange; i'm running a dayton referance 2" midrange rated at 15w full range but i'm running it from 500hz-4khz and feeding it moer like 50w. it does get warm after a bit of hard playing but it wont distort until volume levels get well beyond comfortable listening levels or there is some really complicated music coming out of that range. the same drivers played off of the head unit with only a high pass passive filter did not get nearly as loud before sounding like garbage


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## BuickGN (May 29, 2009)

I can't explain why but I feel like my Dyns have lost some of the dynamics when I went from 220 watts bridged through passives to 75w active with each on it's own channel of the 6 channel. This goes for lower volumes as well. I thought it would make no difference at low volumes but in my case it does.


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## Jsracing (Apr 1, 2011)

BuickGN said:


> I can't explain why but I feel like my Dyns have lost some of the dynamics when I went from 220 watts bridged through passives to 75w active with each on it's own channel of the 6 channel. This goes for lower volumes as well. I thought it would make no difference at low volumes but in my case it does.


I believe dyn tweeters are 8 ohm so youre actually only driving the tweeters at about 35w or so, which may be what youre hearing. That also means the balance betweenmidbass and tweeter are off from what they were with the passive.

Regarding amp specs and drive, keep in mind just because the amp its rated to put out 200w per channel doesn't mean you're pushing 200w into the speaker. rarely do we listen to our systems at full volume, so youre only putting a fraction of the channels capable power to the speaker which is why you can power a 100w speaker with a500w channel without problems.


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## BuickGN (May 29, 2009)

Jsracing said:


> I believe dyn tweeters are 8 ohm so youre actually only driving the tweeters at about 35w or so, which may be what youre hearing. That also means the balance betweenmidbass and tweeter are off from what they were with the passive.
> 
> Regarding amp specs and drive, keep in mind just because the amp its rated to put out 200w per channel doesn't mean you're pushing 200w into the speaker. rarely do we listen to our systems at full volume, so youre only putting a fraction of the channels capable power to the speaker which is why you can power a 100w speaker with a500w channel without problems.


The balance is ok since they're going through the MS8 but overall volume is compromised. If I defeat the processor, the midbasses are quite a bit louder than the mids and tweets, both of which are 8 ohm. That I expected. What I didn't expect is at the same low volumes, the dynamics are gone with the lower powered setup. Or put another way, at the same output wattage, the weaker setup is less dynamic. I always thought that they would sound exactly the same until you hit the lower powered amp's limits.


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## antikryst (Feb 26, 2011)

i was actually about to post a very similar question. im on my first car audio setup. i just upgraded to focal v30 fronts and focal 21v2 sub running off the same 4 channel amp supposedly giving out 80W to the fronts, and 200W to the sub.

my amp is a "budget" amp though so im guessing they dont put out rated power. was wondering what type of difference i would get if i changed my amp to something better.

what happens when the amp uses up all its juice powering the speakers? muddiness? 

the v30s are rated at 80W rms and 160W max.... i believe my amp probably just gives out about 60W rms. im planning to get something with at least 120W of clean power. what differences would i hear?

at normal volume would it just be about the same?

how about for loud volumes?


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## nubz69 (Aug 27, 2005)

"overpowering" will give you better headroom and generally speaking better transient response.


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## cyberdraven (Oct 28, 2009)

nubz69 said:


> "overpowering" will give you better headroom and generally speaking better transient response.


that's a nail in the coffin.


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## antikryst (Feb 26, 2011)

nubz69 said:


> "overpowering" will give you better headroom and generally speaking better transient response.


but what happens when an amp runs out of power in terms of sound quality? will speakers start to distort at higher volumes?


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## tornaido_3927 (Nov 23, 2009)

Don't forget that just because you might have speakers rated for say, 100 watts, a 150 watt per channel amp powering them doesn't necessarily mean you're going to be sending all that power to them, or that you will ever overpower them.

You aren't running your amp gains and head unit volume at full tilt all the time are yas?


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## antikryst (Feb 26, 2011)

tornaido_3927 said:


> Don't forget that just because you might have speakers rated for say, 100 watts, a 150 watt per channel amp powering them doesn't necessarily mean you're going to be sending all that power to them, or that you will ever overpower them.
> 
> You aren't running your amp gains and head unit volume at full tilt all the time are yas?


i totally get that but i dont know how that translates into SQ.

scenario 1:

say the speakers are 100W RMS. then the amp is also 100W RMS. gains are also set accordingly. the amp wont use all its power at normal volumes. then you crank it up and needs more power.

scenario 2: same as 1 but with an amp giving 150W rms. ample headroom. 

im guessing they should sound similar at low volumes. but how about high volumes when more power is needed? scenario 2 is better with headroom right? but how different will it sound.

just curious as im still debating an amp upgrade on my first system.


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## tornaido_3927 (Nov 23, 2009)

That depends on the sensitivity of the driver in question, high volumes might not even necessitate sending a lot of power to them depending on the design of the speaker and the enclosure (and about a thousand other factors).

As far as how it will sound with more power? It will sound louder. Not much if any sonic signature is really left just by having more power, unless of course you get into distortion territory.

Generally, it seems people on here prefer to have more power on tap than their speaker/s are rated for (note I didn't say they are overpowering them) so that they have ample headroom, and so their amps don't have to work as hard and get as hot or introduce as much distortion into the signal.

I can tell you though, if you do send those 100W or 150W or however much more power than the speaker is thermally rated over a significant time, or if you clip it too hard, you'll probably smoke the voice coil!

In your specific example above, there is something to be said for having the amp only able to deliver that amount of power, and that is you won't fry the voice coil by sending it a clean signal. However you may damage it by clipping the signal from trying to turn it up past the limits of the amps output. With the 150W you'll probably not clip the amps output but if you do strive to get super loud or get too much out of the speaker then you may reach it's limits that way.

Personally, I'd take the 150W amp in that situation, but I'd make sure I'm not sending all that to the speaker.. However sending a bit more power than rated is fine for transients, ie. not constant power.

Sorry if I've talked too much and confused you more


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## nubz69 (Aug 27, 2005)

Power is a factor of sound quality only when an amp is asked to do more then it is designed for. Beyond that sound quality and power are not directly related. The best amp in the world is going to sound bad and possiy damage drivers when driven into clipping.


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## ZAKOH (Nov 26, 2010)

The term under and overpowering is so overused. If you run 50watt speakers off the 100watt amp, you're NOT overpowering them as long as the amplifier and head unit gains set right. You overpower them when you send more power that exceeds their mechanical and thermal limits. Likewise, as long as your "underpowered" amplifier is not driving into sending a clipped signal to the speakers, you're not "under powering" anything.


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## sqshoestring (Jun 19, 2007)

eso6686 said:


> Hi,
> 
> I would like to know the effect of under power or over powering a speaker and it affect on SQ.
> 
> ...


There are a whole lot of variables here but in general 100rms comp set at 50rms will sound great. Most people only use that much in normal listening where they could still hear a siren in traffic/etc.

100rms it should sound similar, but your hearing changes at higher volumes too, 100rms amp right at max is pretty loud. If you tried to run full bass on comps it might start to breakup at its rated power.

150rms, hard to say they might blow up they might not. The woofer/mid could bottom or reach xmax easily if you did not high pass it. Some speakers might work ok for a while overpowered, but understand a lot of people don't run their huge amp at full output just because they have it. The idea with headroom is if you hit a loud passage of music it does not exceed the capability of the amp and clip...it stays clean. It is not necessarily just to make it go really loud. A speaker will emit distortion when it gets near xmax, I doubt hardly any common comps are built like high end long throw subs are. Xmax issue is only going to be with bass/midbass.

Like said before you can have an amp with 50rms and another with 300rms, and at 1-50rms they should sound exactly the same. The rating of the amp is its capacity, you can't dog it for not doing more than what it is made to do and it will clip after that (if rating is true).

Far as speakers, we don't know much about what they do at high volume. They tend to do ok until the suspension starts to limit travel, or the VC get hot enough to change electrical properties (or they would sound different lol). In subwoofers they are exploring high output parameters it is pretty interesting to see what is happening. Most people that want super loud mid/highs put horns and pro sound drivers in to get louder.


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## Bluliner (May 16, 2011)

Since music is dynamic, a 100w per channel amp will never truly do that. Factor in things like impedance changing by frequency (voice COIL) and heat and you will not hear any difference between a 50w & 100w amp at normal listening levels. 

The thing that separates one amp from the next is how well they clip. All amps distort, the good ones just kinda hide it better. A few years ago I set the gains on some JL amps for a buddy using an O-scope...you'd be horrified on what I saw. 

Not a very clean amp nor was it very 'muscial'...but 99 out of 100 people would never notice. That's a good amp if you ask me. If the same gain settings were used on something that was assembled in a Chinese prison, it would have sounded like the audio equivalent to a Wendy's drive-thru speaker. 

Bigger amps give you headroom. This is the 'musical' aspect of amplification where a whisper sounds like a whisper and a close-mic'd kettle drum sounds like a bomb going off. That's a lot cooler than rattling the windows across the street if you ask me. Headroom is like horsepower and money...you always want just a little more. 

The speakers will not sound different, it's just the difference between the softest sounds and the loudest sounds on a recording will be a wee-bit more pronounced. However, if you listen to burned discs, MP3's, iPods, or poorly produced (over compressed) CDs...you'll never hear a difference. Unfortunately, most music produced today is made to sound decent on ear-buds and Wal-Mart PC speakers. A good sound system will expose poorly recorded music quite quickly.


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## nubz69 (Aug 27, 2005)

this all comes down to a good rule of thumb. Always power your drivers with an amp that has the same or preferably higher WRMS rating. Do this and you will never go wrong.

I have never heard anyone ever say, "man I wish this amp had less power"


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## cleansoundz (May 14, 2008)

This is useful and relevant informatiin for me. I run 120 watts to 80 watts rms speakers.


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