Underpowered speakers?

hochpt21

I know you guys/gals are sick of lsi15 amp questions...but here's mine.

I found a good deal on some 15's, but the guy said he has been powering them with a Denon AVR 2310. It is rated at 6 and 8 ohms.

http://reviews.cnet.com/av-receivers/denon-avr-2310ci/4507-6466_7-33650440.html

Here is my question.
Could the speakers be damaged/weakened because he didn't power them with a 4 ohm amp?

Thanks,
Paul

jbooker82

No they will be damgaged by underpowering them. That will cause a distorted audio signal because the amp in your avr is strugleing to produce the current needed. So it gets slopy as it tries to keep up.

If anything pushing your LSI's to hard will burn up your AVR if it isnt rated for 4 ohms. There isnt engough resistance so it is like a short in the speaker, causing it to over load and cook.

tonyb

Short answer is yes, I would pass knowing that. Unless your up to replacing parts. You don't know this guy, therefore you don't know how hard he drove the speakers under powering them. Your taking a bigger risk than need be. I would normally suggest you get an ear on them first, but since the guy has nothing to properly power them with, whats the point.

62caddy

Too little power in itself cannot ruin a speaker. Rather it is amplifier clipping which results in overpowering the speakers (particularly the tweeters) that results in damage. Generally speaking the more underpowered the amp, the more likely clipping to occur but there are lots of variables that come into play. I've known many so called "8/6 ohm" units to be used for years in conjunction with two pair of 8 ohm speakers without incident or damage. It all depends on how the system was used. That said, I wouldn't be afraid to buy the speakers- however I'd first like to verify proper operation first as I would with any used speaker- whether used with a 20 or a 200 watt amplifier.

hochpt21

Thanks for the feedback.

I'll have to weigh the risks vs the price. He lives in an apartment and said he hasn't been able to turn them up very loud (I know what he said doesn't necessarily mean anything!) They are also less than a year old.

I am going to see them tomorrow and will try to get a better feel then.

I know its a risk either way and I appreciate the feedback.

Dennis Gardner

Just know that all gear sounds its best just before they burn up.......................I can't tell you how many times I've heard that from guitar players, sound techs, and audio enthusiasts throughout the years. Always looking for "just that sound"!!!

hochpt21

Is it just the tweeter that could be damaged? Anyone know how much replacement tweeters for the 15s would be?

He had them listed for $700 originally and has dropped the price a couple times and told me he would take $550. Would $550 be worth it even if the tweeters go out at some point?

Dennis Gardner

$550 is a good price if they are cosmetically nice. I would guess that the tweeters would be around $100 each. If you listen to them and they sound great, buy them if the price is right. Recently around here on the forum, a few LSi 15 owners have had crossover parts burn up on their speakers, not drivers.

62caddy

hochpt21 wrote: »

Is it just the tweeter that could be damaged? Anyone know how much replacement tweeters for the 15s would be?

He had them listed for $700 originally and has dropped the price a couple times and told me he would take $550. Would $550 be worth it even if the tweeters go out at some point?

I'd take the grilles off and placing your ear close, carefully listen to each driver- moving your ear as needed. They should not make a harsh, raspy or grainy sound. From everything you say- the owner is an apartment dweller and doesn't play loudly, they're under a year old- I'd be really suprised if they had an issue. Incidentally, they still may be under warranty so if you can obtain the original proof of purchase, it may be to your advantage. Crossover damage is relatively rare, generally speaking. Just use your good judgement and common sense- remain cautious but open minded. By the way, he didn't happen to volounteer what type of music he normally listens to, did he?

gp4jesus

Couldn't you demo them @ his place w/what you plan use if you buy them?

hochpt21

Yea, thats a good idea. I was hoping to just take the B & K, but his avr doesn't have pre-outs so I'll pull the HK out as well. Just have to take the door off the tv cabinet (tight fit), but small price to pay i guess.

Drenis

^ That's nice the seller will let you come over and use YOUR gear to power them. Lots of people don't do that.

There are some risks associated with that which would make me a bit cautious. Good luck and hope you find what your looking for.

62caddy

Seems a bit overkill from where I stand but very obliging of the speaker owner. Sounds like a real gentleman. Best of luck.

ravaneli

tonyb wrote: »

Short answer is yes,

My short reply is BULL.

I don't know who came up with this bull about underpowering speakers being harmful, but it is total bull. You, tonyb, should stop dispersing these obviously ridiculous personal opinions.

Listen, OP, I am not going to explain again why underpowering speakers is harmless, and I feel sorry for you coming here for advice and being fed myths for something that is not subjective, but absolutely objective. My advice to you is go grab these speakers right now, and if you still have any doubts call POLK instead of listening to master tony.

hochpt21

:eek:

tonyb

ravaneli wrote: »

My short reply is BULL.

I don't know who came up with this bull about underpowering speakers being harmful, but it is total bull. You, tonyb, should stop dispersing these obviously ridiculous personal opinions.

Listen, OP, I am not going to explain again why underpowering speakers is harmless, and I feel sorry for you coming here for advice and being fed myths for something that is not subjective, but absolutely objective. My advice to you is go grab these speakers right now, and if you still have any doubts call POLK instead of listening to master tony.

So says the man with no experience. Personal attacks like this will get you banned bro. But hey, keep it up if thats your game plan, I can wait.

hochpt21

Tony and many others have been extremely helpful to me in my time here. I have a lot to learn, but would be lost without much of the advice/opinions I have received so far.

Geoff4rfc

ravaneli wrote: »

call POLK instead of listening to master tony.

That's Mister Tony to you!

Btw Tony, you mean all that scientific evidence that shows how by trying to feed speakers an overabundance of current from a unit that doesn't have enough power to supply said current and causes clipping of the speaker is just a myth?

I'm telling Mr. Polk on you!

ravaneli

This is ridiculous. And you have the nerve to keep going.

Is there an actual engineer here? Preferably someone on the Polk staff?

I am no engineer, or speaker guru, but they did teach us some basic physics laws at school in my country. I know in this country things like physics and math are not mandatory and people prefer taking sociology instead, but this is no excuse here.

Does anyone here know what rated power means? W = V . I ? With lower impedance the current increases, and hence the power. So a 100W (@8ohm) amp can blow a 100W rated speaker, if the speaker is 4ohm, because the amp will actually be feeding more than 100W. But if the speaker is 250W rated, no damage can be done to the speaker, you are just going to smoke your amp if you push it.

This stuff about distorted or clipped signal being different to the speaker than normal signal is all in your head. The speaker doesn't know, doesn't care. The clipped signal does have higher power than the normal one would, but as long as that power is within the specs of the speaker all is good.

All of these impedances that are reported are nominal anyway. The impedance (and current accordingly) vary, and sometimes a lot. That's why things are rated for power, and as long as you stay within the power specs you are good.

It is really that simple, and the people with the jokes about me taking the short bus should really have enough muscle on the second floor to figure this out. After all, talking down means you are sitting higher.

steveinaz

If the tweeters haven't been blown (or ever replaced), you should be ok.

steveinaz

ravaneli wrote: »

This stuff about distorted or clipped signal being different to the speaker than normal signal is all in your head. The speaker doesn't know, doesn't care. The clipped signal does have higher power than the normal one would, but as long as that power is within the specs of the speaker all is good.

All of these impedances that are reported are nominal anyway. The impedance (and current accordingly) vary, and sometimes a lot. That's why things are rated for power, and as long as you stay within the power specs you are good.

You need to do some research. Clipping causing irregular frequencies being sent to the tweeters, thereby blowing them isn't "voo-doo" it is FACT. Under powered amps, especially with limited impedance capability is the number one cause for blown tweeters. Having said that, if you listen at conservative levels, you'll never clip the output of your amp section---so you'll never have the problem.

Do you have any concept of how impeadance affects power output/current flow?

heiney9

Clipping causes the sine wave of the audio signal to become entirely flat at the top when it should be a smooth curve. That flattening out of the perfect sine wave has a plethora of distortion properties that will damage speakers, most notably tweeters, but it can also heat up the voice coils of larger drivers and burn them out and then poof...............no more sound, or distorted sound even at low levels. It's always better.............ALWAYS better to provide speakers with more power than their nominal ratings, of course if you go insane with the power and hit a large transient you can damage speakers with to much power as well. But it's much less likely.

H9

heiney9

Clipping is caused by underpowering a speaker. Yes, the clipped signal originates at the power source but it's the interaction of the power source, source material and speakers that cause the scenario.

H9

jimbo1421

ravaneli wrote: »

...if you still have any doubts call POLK instead of listening to master tony.

Actually, Polk has already spoken on the issue:

All components have limits and exceeding the limits of either the speakers or the amplifier/receiver may result in speaker failure. Ironically, you are more likely to damage a speaker when using a low-power receiver than a high power one. An amplifier's power rating is the power output without distortion. Amplifiers will put out more power than their rating, but at higher distortion levels. Distortion breaks speakers. On most receivers, full power is usually achieved when the volume control is at the halfway or "12:00 o'clock" position. When you turn the volume knob past the full power point, the amplifier distorts. Sound that is harsh, strident, brittle or unpleasant in any way is an indicator of a distorting amplifier and is your signal to turn down the volume.
The wide dynamic range of today's action/adventure movies also plays a role in damaging speakers. Explosions and other sound effects are recorded at a MUCH higher level than dialog and average sound effects. If you set the system volume to a pretty high level during "normal" scenes, it's going to be way too loud during the bang-bang, boom-boom scenes. If you want your system to play louder than it currently does, without distortion and speaker damage, you will have to get a better, more powerful amplifier/receiver (see The Truth About Power Ratings) and/or bigger speakers.

More here: http://www.polkaudio.com/education/article.php?id=45

Jim

dekuda

ravaneli wrote: »

This is ridiculous. And you have the nerve to keep going.

Is there an actual engineer here? Preferably someone on the Polk staff?

I am no engineer, or speaker guru, but they did teach us some basic physics laws at school in my country. I know in this country things like physics and math are not mandatory and people prefer taking sociology instead, but this is no excuse here.

Does anyone here know what rated power means? W = V . I ? With lower impedance the current increases, and hence the power. So a 100W (@8ohm) amp can blow a 100W rated speaker, if the speaker is 4ohm, because the amp will actually be feeding more than 100W. But if the speaker is 250W rated, no damage can be done to the speaker, you are just going to smoke your amp if you push it.

This stuff about distorted or clipped signal being different to the speaker than normal signal is all in your head. The speaker doesn't know, doesn't care. The clipped signal does have higher power than the normal one would, but as long as that power is within the specs of the speaker all is good.

All of these impedances that are reported are nominal anyway. The impedance (and current accordingly) vary, and sometimes a lot. That's why things are rated for power, and as long as you stay within the power specs you are good.

It is really that simple, and the people with the jokes about me taking the short bus should really have enough muscle on the second floor to figure this out. After all, talking down means you are sitting higher.

You sir are ridiculous in criticizing a respected member here. Take Tony's advice. Some manufacturers of receivers will not rate their equipment at 4 ohms or recommend not driving that load. We know why. Running them at 4 ohms and you may have dipps down to 2 ohms at certain frequencies and feel how hot your receiver will be running. It is trying to keep up with the current needs. It may not distort but at higher volumes it can happen and it can damage your speakers. I've seen it. Never seen a problem overdriving and probably won't because of Ohm's law...... Enough said !

F1nut

Preferably someone on the Polk staff?

http://www.polkaudio.com/education/article.php?id=45

heiney9

This probably gets more to issue.

http://www.polkaudio.com/education/article.php?id=4

This is probably the best excerpt from the above article

Also, standard amplifier tests cannot mimic the same electrical conditions, or load, of an actual loudspeaker. But most of all, specifications cannot measure the quality of sound.

Therefore using constant values of I, V, R in an OHMS law formula means very little in real world settings.

H9

F1nut

hochpt21 wrote: »

He lives in an apartment and said he hasn't been able to turn them up very loud

In that case, chances are the speakers are fine.

Drenis

Incredible what's been posted here regarding under powering speakers...

Even my girlfriend who is audio-illiterate knows that under powering can damage with certain circumstances in place. She may not know all the reasons but it's common sense. Why? Because of one word... distortion.

heiney9

Scroll down to the heading "Reactive circuits with time-varying signals",

This explains very plainly why Ohms Law in it's basic formula can't be used for a source that is "variable" like a musical signal is.

http://en.wikipedia.org/wiki/Ohm%27s_law

heiney9

To the OP, if the speakers play fine at a moderate volume they are almost sure to be undamaged. I am assuming you will get to demo them before you take them, if not, the fact he lived in an apartment means they most likely weren't abused. Just have to go with your gut on the honesty of the seller.

H9