OK, what is the real truth about underpowering speakers?

[Telecruiser]

I hear it on here from time to time and instead of anyone giving a real reason they usually just side step the issue.

 

What is the truth? Can you damage/blow a speaker by underpowering it and if so how does this happen? Is it the clipping of the amp that cause it? I know you can blow them from over powering but that makes a little more sense to me.

 

Also, what is the proper method of matching the speakers power requirements with the right amplifier so under normal use you don't end up with blown components?

 

Thanks

[monkeyland]

you can't hurt a speaker by feeding it too few watts. you can hurt it by clipping an amp which can produce big power spikes. this isn't typically a problem with modern amps since most all of them include clip limiters.

 

a lot of people end up mating big amps with speakers that are not up to the challenge because they have fallen for this line. those people most likely also end up re-coning a lot of speakers.

[agedhorse]

Clipping an amp results in more than rated power... if you clip a 500 watt (RMS) amp it can deliver up to 1000 watts (RMS). Additionally, the clipped waveform contains a MUCH higher percentage of harmonics so you clip an amp at 500Hz, you get 1000, 2000, 3000 etc in varying levels below the 500 Hz fundamental. These harmonics primarily overpower the high frequency driver.

 

Hence, "underpowering" is really unintentional and selective overpowering.

[dennis a]

To add to what AH said "underpowering speakers" is just an expression like "EQing a room"...it is not a literal translation. When you try to feed 400 watts into a 1000 watt speaker with an amp rated for 100 watts, you will probably do damage and the popular term is "underpowering the speaker"...it's not an accurate term but it is not going away any time soon.

 

Dennis

[Craig Vecchione]

 

I hear it on here from time to time and instead of anyone giving a real reason they usually just side step the issue.

 

 

Bull{censored}. It's been fully explained here dozens of times over the years.

[agedhorse]

I certainly have

[Mogwix]

 

Also, what is the proper method of matching the speakers power requirements with the right amplifier so under normal use you don't end up with blown components?

 

By understanding the limits of the system and having realistic expectations of performance goals. So... it depends.

 

One can run a rig that's grossly overpowered for years without blowing any drivers, the problem is that a lot of people will try to push systems beyond their limits and then you've got smoke and blown drivers.

 

We try to idiot-proof systems by matching amplifiers, setting limiters, and adjusting the crossovers... but as they say, there will always be a better idiot.

[BillESC]

There will always be a better idiot.

 

Amen.

[tlbonehead]

Is it the clipping of the amp that cause it? I know you can blow them from over powering but that makes a little more sense to me. Also, what is the proper method of matching the speakers power requirements with the right amplifier so under normal use you don't end up with blown components? Thanks

you ever blow your stereo speakers from turning the volume down? As for matching speaker to amp, match them. That's about it.

[tlbonehead]

What is the truth? Can you damage/blow a speaker by underpowering it and if so how does this happen? Is it the clipping of the amp that cause it? I know you can blow them from over powering but that makes a little more sense to me. Also, what is the proper method of matching the speakers power requirements with the right amplifier so under normal use you don't end up with blown components? Thanks

It is answered every time it is asked. Do you just not like the answers?

[twostone]

Underpowering means:

Do women mean yes when they say no ?

Just kidding

I think Andy pretty much summed it up.

Underpowering just another term for clipping the amp.

Lot of speaker specs. read 1w@1meter when tested.

[Telecruiser]

As for matching speaker to amp, match them. That's about it.

 

Thank you for you technical expertise by providing an clear and consise answer to my question. I'll just assume that you just don't know the answer.

 

-------

 

BTW, thank you Andy for your answer. I have a better understanding now of what is going on. I am not on this forum all the time so I must have missed the prior discussions.

[Bobby1Note]

FWIW, I've been coming here for something like three years now, and I don't recall once, ever seeing as complete an explanation as Andy has delivered in this thread. Kudos to Andy.

 

On another note; the word "idiot" sure gets over-used around here sometimes. I wonder how many people would use the word "idiot" if it was one of their kids, or grand children asking the question. Why would/should a "noob" know any better?

[madjack]

FWIW, I've been coming here for something like three years now, and I don't recall once, ever seeing as complete an explanation as Andy has delivered in this thread. Kudos to Andy. On another note; the word "idiot" sure gets over-used around here sometimes. I wonder how many people would use the word "idiot" if it was one of their kids, or grand children asking the question. Why would/should a "noob" know any better?

 

Actually, the word "idiot" originally was used to denote someone with a Wechsler or related scale score of 0-25 points where 100 points denotes average intelligence. Modern terminology would be profoundly mentally handicapped. I think what is actually most often meant here is either "moron" or "ignoramus".

 

As for matching speakers to amps; I've always used the rule of thumb of 1-1.5 x rms value of speaker. A speaker rated at 100watt rms I would normally drive with an amp rated at 100-150 watts.

[Bobby1Note]

"ignoramus".

 

Heyyy,, that's what "Mom" used to call me,,,,, and I always thought she saw me as a Roman warrior. Maximus,,,, Ignoramus,,,, etc.

[Craig Vecchione]

Thank you for you technical expertise by providing an clear and consise answer to my question. I'll just assume that you just don't know the answer. ------- BTW, thank you Andy for your answer. I have a better understanding now of what is going on. I am not on this forum all the time so I must have missed the prior discussions.

 

Again, bull{censored}. You wrote that you "hear it on here from time to time". So you've read discussions enough to have determined that we "usually" do, which you claim is sidestepping the issue.

 

I'm hammering you on this because this topic comes up so often, and because at least one of us always gives a complete answer.

[Dogoth]

Think of it this way. If an amplifier has a voltage rails of 25 volts (total difference + to -). At 4 ohms that is 625 PEAK watts (or 442 watts RMS for a sine wave). There are other factors involved here but to be simplistic this will work for us. That 625 watt figure is the PEAK wattage (when the waveform hits 25 volts it momentarily clips). Think of the waveform as mountain tops and you have just chopped the tops off and graded them flat, all at the same elevation. You still have some valley's between them, right? The average amount of dirt under your feet in this mountain range is the AVERAGE wattage. If you had an earthquake that raised the whole mountain range by 100 meters (you turned up the input volume), you would have to re-excavate and chop off even more of the mountain top to maintain the same maximum elevation (your fixed voltage rails). The result would be steeper cliffs yet shallower valleys correct? the average amount of dirt under your feet would be even more than before (same PEAK wattage - more AVERAGE wattage). You just made your 442 watt amplifier put out maybe 1000+ AVERAGE watts. This is what will blow up your speaker.

 

The other factor here is the steep cliffs. The faster the rise time (or fall) the higher frequency it represents. By clipping your amplifier you have a LOT more high frequency information approaching that 625 watt peak mark. Tweeters are not made to handle this kind of power at all and they are usualy the first to go under this kind of duress.

 

This is a rough graphic representation (on a grand scale) of what happens when you "clip" an amplifier and it's effect on speakers.

 

I hope it helps

[Shaster]

The underpowering theory has been discussed here almost as much as the two dreaded "B" topics. I think in the parlance of TV, we can consider this myth busted.

[Coaster]

underpower megathread?

[Shaster]

There ya go!

[badhabit]

 

As for matching speakers to amps; I've always used the rule of thumb of 1-1.5 x rms value of speaker. A speaker rated at 100watt rms I would normally drive with an amp rated at 100-150 watts.

 

 

Based on this statement, then would an amp rated at 1100 watts RMS into 4 ohms (per side ) be adequate/good for (2) 400 watt RMS rated 8 ohm bass speakers ? Running both speakers on one side of the said amp would result in 550 watts RMS into each speaker, correct? Then would this be considered an appropriate amp/speaker match up?

[Coaster]

it depends.

 

 

 

but its probably going to be fine.

[Redbassman86]

 

Again, bull{censored}. You wrote that you "hear it on here from time to time". So you've read discussions enough to have determined that we "usually" do, which you claim is sidestepping the issue. I'm hammering you on this because this topic comes up so often, and because at least one of us always gives a complete answer.

 

 

Very true. May I suggest a "Sticky" about this subject?

[Dogoth]

underpower megathread?

 

Ha! Ha! Ha!

[GCDEF]

I'll try and put it out there again. There are a couple of flaws in the underpowering myth. For illustrative purposes, let's assume you have a 500 watt amp and two sets of speakers. One set handles 250 watts and the other 1,000.

 

Flaw #1 is that if you underpower your speakers, you're going go drive your amp to clipping.

 

Nobody has yet even attempted to explain how the speaker wattage affects whether you'll drive your amp to clipping. If you have the 250 watt speakers why would you be less likely to drive your amp to clipping than if you had the 1,000 watt speakers?

 

Flaw #2 says that you should have somewhere around twice the amp power available as speaker power.

 

The other question nobody has ever even tried to answer is if you do drive your 500 watt amp to clipping, which set of speakers would be more likely to survive? The 250 watt or the 1000 watt?

 

The whole nonsense seems to center around clipping the amp, and for some reason that's transmogrified into meaning you need twice the amp power your speakers can handle rather than getting the amp you need and speakers that can handle it, or just not pushing your equipment to the limits.

 

It makes sense to overpower your speakers if you're trying to squeeze every last drop of sound out of them and if you know what you're doing. For most people, it's just asking for trouble.