Why do audio manufacturers continually lie to us?

[StageLeft]

I have yet to come upon an audio system in which the speakers were rated along with the power source and the power source was unable to destroy the speakers. For instance my home theater receiver is 5 X 110 and my paradigm titans are rated at I think 100 watts each. This thing could blow them without even trying if I wanted to. In my car 17 X 4 RMS on my head unit rating is easily able to distort my 4 X 40 RMS speakers.

It seems to me that for mose audio equipment if you want it so that you can turn the volume on full, or near enough, - and yes this is speaker distortion not distortion from the source - you'd need speakers rated several times more powerful than the amplifier itself. Why is this?

 

[Hossenfeffer]

Because God wants it that way.

 

[FrogDog]

Yeah that is annoying. I blew out a set of computer speakers a while back by putting the volume up too high. That should not happen.

 

[StageLeft]

So nobody here knows? I'm quite shocked. :Q

 

[bizmark]

For one thing, you've got to define it well: at what frequency, or what frequency range, can the (speakers take) / (amplifier put out) that kind of wattage? There's no uniform standard. Plus, with home theatre receivers, the wattage with one channel driven can be vastly different from the wattage with all channels driven.

Are you sure that your receiver could blow out your Paradigms, without the receiver clipping? I doubt it. It would probably cause them to distort, but not destroy them.

Also, I wouldn't be so sure that the distortion you're hearing is from the speakers, esp. in your car. Have you tried a separate, more powerful amp? I used to swear up and down that the amplifier didn't make a difference in an audio system. Then a friend of mine upgraded the headunit in his car and the difference was HUGE. He immediately forgot about upgrading his speakers, which he had been planning on doing before.

Something to keep in mind is that even at very loud volumes, the average wattage is like 1W, and the 100W peaks only come transiently.

So the thing to take from all of this is that they're not lying, they're estimating. I'm no EE but I keep up with the audio scene, and this is what I've gleaned over several years. I could be wrong. I'm looking forward to seeing what others have to say on this, because my knowledge is very incomplete and I'd like a more detailed description of this stuff.

 

[jjones]

It's kind of like the hotdogs and buns thing. They sell hotdogs in packages of ten but buns in packages of eight. Why is that?

 

[StageLeft]

Well for what it's worth when i first got this setup in the car I was using some no name brand $30 speakers and the headunit easily blew them. I wasn't even testing - a song came on loud I wasn't expecting and it distorted. After that the speakers were blown and were rated by RMS about twice the headunit and for peak wattage about 2.5X. Now those were no-name, but still...

Currently when I hit "loud" on the headunit the speakers I have now ($70 pair of kenwoods in back and front) it's easy to distort them. You may be right that it couldn't blow them but the cd player has a bunch of room left on volume and distortion is the first step on the road to blowing

I'm not positive my receiver could blow my paradigms - send me $200 and I'll let you know for sure by blasting it up to 10 Although these are nice speakers when I'm at level 5 I can only hit level 5 without distortion if I have the bass all the way down. Now that's loud as HELL but still I do think the receiver could blow them if I jacked the bass up without much difficulty.

 

[Ornery]

"...turn the volume on full, or near enough..."

This is ass backward. You're supposed to decide how much SPL you ultimately want in a given size room, and match the components to that. They should be able to supply that SPL at less than half volume. That receiver must be clipping if it's run near full volume. There ought to be the equivalent of rev limiters on amps for certain people!

What you are doing is like running an engine at it's redline for extended periods. The speakers can handle power spikes at or above the rating, not constantly, but I doubt most speakers are properly rated at all. Just hype to appease the audio weenie masses. I don't see why you couldn't just return them if they aren't suitable. Buy from a company that more accurately rates it's equipment.

 

[StageLeft]

I've only once had my amp at 5 when I was testing and it hurt. Generally I'm not above about 3 on it.

<< I doubt most speakers are properly rated at all. Just hype to appease the audio weenie masses. I don't see why you couldn't just return them if they aren't suitable. Buy from a company that more accurately rates it's equipment. >>

Well I agree I think most are not rated properly such that you generally have to overcompensate knowing they may be under-rated. I think ALL companies lie though on this! At least the ones I've ever seen...not that I deal with super high-end stuff though.

 

[Nefrodite]

In my car 17 X 4 RMS on my head unit rating is easily able to distort my 4 X 40 RMS speakers.




actually i think your more likely to blow your speakers with an underpowered amp. i forgot the term but weak straining amps do some nasty things to speakers. 17x4 rms isn't good at all. and it doesn't sound good at all, i've tried the headunit only route for a while.. it was dissapointing your head units distorting, not the speakers. i used to power my infinity/polk(ones with silk tweeters) speakers using a 4x40(not sure on rms) headunit.. sounded like cr@p and would distort. now i run on a 200watts RMS amp and i can get to painful levels and still not distort go figure.

i guess the best way to describe the difference is that they don't sound muddy anymore

 

[bizmark]

Well, from what I can tell, there's two ways to blow speakers: 1) Blow them and 2) Clip the amp.

1) involves having way too much power for the speakers. The speakers don't have enough range of motion to take all of the power they're being given. They bottom out the magnets and the surround. This is the way to blow a woofer. I think it's pretty hard to do and most decent speakers have overload circuitry designed to protect against this. And you'd have to have like 3X the rated power to do it.

2) involves having the input signal to your amp bumping up against the maximum headroom of your amp. So what happens is like this. You have an imput signal (say, from your CD player) that's curvy:


................./^\............../
\............../.....\............/
.\............/.......\........../
------------------------------ etc. This is a nice, smooth curve with rounded peaks, although I can't draw them.
...\......../...........\....../
....\....../.............\..../
......\_/................\_/

Then, your amp basically wants to take that same graph and draw it a million times bigger. BUT, it runs out of headroom. Say the input signal peaks at, on some imaginary scale (I don't know all of the exact units involved), a 2. Then you want to amplify it by 1,000 (not unrealistic, I think) and that'll power your speakers. But your amp only has enough power to output 1,500 -- not the 2,000 required to draw the whole thing. So your amp outputs the following:


\............../^^\............./
.\............/.......\........../
------------------------------ etc. This is the same graph as before, but with the ends chopped off.
...\......../...........\....../
....\___/.............\_/

At the extreme levels of clipping, you get a square graph:

.........|^^^^^^^|..........|
|........|............|..........|
-----------------------------
|........|............|..........|
|___|.............|____|


It's this that can really wreak havoc on the speakers. Normally, speakers have a nice, smooth motion: they go one direction, then slow down, come to a nice, smooth stop, and accelerate in the other direction. (A few thousand times a second.) With clipping, the smoothness is taken out: They are in position X, they suddenly (almost instantaneously) accelerate and move to position -X, where they stop (almost) instantaneously, and they stay there for a split-second, when they suddenly move back to X, again coming to a screeching halt from a very fast movement. The forces put on the drivers are way beyond what they ordinarily take. This has destroyed several of my tweeters (when I lent my setup to some friends I had warned them but they still turned it up too loud).

The problem of clipping essentially comes down to not having a powerful enough amplifier. If the levels between the inputs of the amp and the outputs aren't really matched well (say you have a CD player that puts out way over-spec signals) then you can get this problem even if your amp is very powerful. The headphone jacks on portable CD players clip a lot when you turn them up to full volume. They simply can't play the signal loudly enough.

Anyway, this is like the sum of my knowledge on this subject. I may be wrong, but I have read from good sources that it's *MUCH* easier to damage speakers with an under-powered amp than with an over-powered amp.

[edit]: trying to pretty up my graphs ERG it's hard b/c they don't look the same when I hit "preview" as when they're actually posted... okay good enough now.

 

[kami]

Sony's are never rated their full watts when all 5 channels are being driven AFAIK. 110w? Probably more like 60-70 max. There is a site somewhere that tested a bunch of receivers and hardly any got even close to their advertised wattage...i can't find the link though.

my Yamaha RX-V496 is rated at 70 watts when all 5 channels are being driven, and according to the tests on it it is accurate (within 2-3 watts i think) but I'm never gonna blow my speakers out with it. I don't think I've ever turned the volume knob past HALF cause it was DAMN LOUD. Why would you want it on full? Like in U-571 for example in the depth charge scene when the water starts screeching out of the pipes I think I would actually cause real damage to my ears if I put my volume above halfway :Q I've never come close to distorting my stuff and I like my stuff **LOUD**!!! Anything over half is just too uncomfortable with full dynamic range.

And when you talk about you car speakers distorting, I think it's the 17w amp distorting, not the 40w speakers?

btw i'm no expert and don't know much about the science of audio, but I picked up quite a bit when i was researching before getting into home theater and that stuff. don't take anything as fact, just educated guesses.

p.s. turn the bass to neutral and i bet your titans will go very very very very very ear-shattering loud without any distortion. if they don't then i blame your receiver

 

[Soybomb]

Yeah I think you're going at it backwards, when you're getting at full volume on that head unit its clipping. Always make your amplifier more powerful than you're going to want. If you want to give the speakers 100w, get a 150 watt amp. The amp couldn't keep up I'm afriad. For instance I run a deck that has a max of 17 watts rms per channel as well, a little sony one (damn you sony, i will never buy your audio products again) and its driving some infinity kappa 6x9" speakers in the rear. If I turn the deck up to full volume the sound is terrible. So does this mean that Infinity (I really don't care for their audio quality anymore after hearing brands like focal anyway but....) was lying when they said the speakers could handle 110 watts rms power? No, at all, I'm underpowering the speakers.

This is whats happening :
Clipping: An undesirable over-drive condition that occurs when an amplifier runs out of power and creates a potentially dangerous wave-form distortion that can destroy loudspeaker voice coils, especially in tweeters. Clipping is a very audible and unpleasant distortion and always the result of output levels that are in excess of what the particular amplifier/speaker combination is capable of. Quickly turning down the volume remedies this condition. Incidentally, clipping occurs not because an amplifier is too powerful but because it is underpowered. Loudspeaker units damaged by clipping are usually not covered under manufacturer?s warranties and are considered abusive failures.

 

[Pacfanweb]

You always want an amp that's more powerful than the speakers are rated to handle.

Most home systems are at full power WAY before 10. If you're running it that high, then you're clipping the amp, period.

Skoorb, same thing is happening to you when you hit the loudness button. I doubt it's the speakers.

Example: when I was a kid, my dad had a McIntosh home system. (I still have it, actually, and the amp can still blow away nearly anything not made by McIntosh now)

He started off with the XR5 speakers, and a Mac 1900 receiver, rated at 75 per channel, as I recall. The speakers were rated MUCH higher.
He blew the fuses in the speakers constantly at high volumes( ok, I blew most of them).

Then he got an MC2205 amp, rated at 200 per channel. The McIntosh sound lab was in town at the time, and it tested to 277 per channel STEADILY before it exceeded its rated disortion. It can peak much higher.
The speakers took it fine. Hardly ever blew another fuse, and it was usually the tweeter fuse from my KISS Alive II album. (back in the day)
The amp had watt meters, and clipping lights, so if you kept the amp just below clipping level, it never blew the speakers.

 

[blahblah99]

There are a few reasons why signals distort in an audio system:

1. Your amplifier can't handle the low impedance. Either the amp is poorly designed or the speaker impedance is too low for the amp is intended for.

2. Your speakers are receiving the FULL range of frequencies (20hz - 22khz) and isn't designed to handle that. This is probably 90% of the cases out there as many unsuspecting consumers just hook up a speaker to their amps without any crossovers. A 4" coax can't handle anything lower than 80 and will distort the sound easily.

3. Cheap speakers. Speaker ratings mean nothing on cheap speakers as they will distort will little power no matter what.


In short, you always want an amplifier that is rated MORE than what your speakers can handle. You also want to add crossover networks (either passive or active) so that your speakers get only the ranges of frequencies they were designed for.

Take a look at those BOSE systems. Their cube speakers are only 2", yet they produce big, room filling sound. Why? Because their crossover networks filter out the low frequencies (lets say anything below 120Hz) gets cut off at a rate of -18dB/oct, for example and that allows the 2" speakers to go louder than it could if it received all frequencies.

 

[Maetryx]

Thanks for the graphs and the lesson, wbwither. Much appreciated, here.

 

[StageLeft]

Well this undermines all I'd ever thought (by this I mean assumed) about this but is pretty interesting. I think I'll re-read the thread again in fact.

My original setup in the car for instance was the 4 X 17 RMS and 30 RMS no-name speakers I bought from circuit city. One song in particular when I'd have the volume at 30 this is the particular time that one of the no-names blew. After this even at 15 I could tell the speaker was blown as it was moving weirdly when you look up close and made a god-awful buzzing sound.

So I replaced it with these new kenwoods that are rated at 40 RMS or so. On the same song as before that blew my old speakers at 30 I can now run at 35 without distortion. Now IF the no-names were properly rated since they blew at 30 volume it means the headunit was clipping and buggared them. But if that is the case wouldn't a volume of 35 make the headunit clip even more and thus put additional stress on the speakers? Since the kenwoods can handle it either the headunit was not clipping and the first speakers just sucked, or the headunit clips more than before (given the high volume), but the kenwoods are just way more capable at taking clipping-abuse.

that's weird about clipping - I'd like to have a couple of different powered stereos on the same speakers to test it out.

I only started using the "loud" button a few days ago and I LOVE it but it is SO damn bassy (all I have is the 4 6.5" speakers with no plans on getting a sub) that I can't turn it up loud before getting some wickedly bad distortion...I guess if I got a low-end amp I could start putting some real volume into these speakers with loud on then right?

 

[glen]

the commonly held belief is that an underpowered amp will blow the speakers.
However, this is not true according to members of the AES.

 

[CocaCola5]

Search the web, I am sure there are dozens of good articles on why the Watts/ch ratings are worthless.

 

[StageLeft]

<< Search the web, I am sure there are dozens of good articles on why the Watts/ch ratings are worthless. >>

For anyone interested I just found "Matching Amps to speaker ratings" Part I & Part II. I'm scared that if I learn anything else I'll feel almost uncontrollably compelled to buy an amp.

 

[tcsenter]

From the same website, here's a little FAQ/Guide to power ratings: Power Rating an Erroneous Quick Indicator of System Quality

 

[Squisher]

Not so much underpowered as having a propensity to distort at high volumn(headroom). Once that amp starts clipping its ability to blow up speakers goes way up, however you're not going to blow up my Cornwalls with a transistor radio no matter how much you turn it up.

 

[bizmark]

I would like to point everybody to what blahblah99 said. He is as much an expert at this stuff as anyone I know.

Skoorb - it depends on how they blew. I assume that the bass driver (I won't use the term woofer) blew? If so, it's probably just the overall cheapness of the speakers. The components weren't built with strict enough tolerances to play loudly, reliably. You said you just blew out one (not all of them at the same time) so I'd say that this was probably because the speakers were cheap and built to low tolerances. One out of four failed at 30 volume. Could you continue to play the others at higher volumes?

Also, one thing with cheap car speakers in particular is the surrounds (the part that holds the woofer to the frame). On cheap car speakers, they're almost always paper or something crappy. On better ones, they're rubber or something like that. Note the difference in pliability between rubber and paper. At low amplitudes, the difference isn't that great. The speaker is moving back and forth maybe .01 inch or something (not big enough to see), and the paper can handle that fine without distorting. But at higher amplitudes, say with visible cone movement, the paper is bending back and forth in a way that distorts the sound. Rubber wouldn't. That's one way that cheap speakers sound bad.

Another difference between very cheap speakers and decent speakers is the driver itself. On cheap ones, again, they're made out of paper. There's no way that cheap paper can be rigid enough to present a coherent surface at high amplitudes of complex waveforms. Think about it, you've got the speaker being moved back and forth by this magnet in the middle. What if the cone itself bends, so that when the magnet is fully forward, the outer edge of the cone is still in the original position, and the wave propagates outward on the cone? That's a huge problem and can make things sound terrible. Of course, the extent of this problem usually isn't as great as I just said, but you can never get perfect linearity on a moving cone. That's why high-end speakers use Kevlar and other exotic materials to try and increase the stiffness and reduce distortion.

So I'd say that the first speakers blew because they were crappy, not because the amp was clipping. Clipping tends to damage the tweeters before it damages the bass drivers. Now that you have decent speakers, the amp is coming close to its clipping point.

Something else that comes into play is impedence. This is really where I start to not know what I'm talking about, but I'll try to explain what I know. No speaker has a single impedence across all of its frequencies. So the impedence that a speaker is rated, is more or less a weighted average of the impedences across all frequencies. So a speaker that's rated at 4 ohms could have a minimum impedence of 2.7 ohms at 100Hz. In general, this isn't enough to cause problems. It's funny though, how this impedence effect occurs. Like, if you close the port on a speaker that's ported, it'll change the impedence of the speaker at certain frequencies. Freaky stuff and I can't explain it. The impedence of a speaker directly affects how hard of a time the amp has. So, in general, the interplay between amp and speaker gets very complex.

How this relates to Skoorb: Perhaps the newer speakers have some impedence characteristics that increase the compatability with the headunit, making for better sound and less of a chance that either will distort.

 

[StageLeft]

Yep it was just the single one that blew and the others were fine...they did have paper in them BtW They were profile name brand I remember now.

Off topic slightly and on to your impedence thing - my home receiver has a switch at back for 4 or 8 ohms. I think it says set to 4 for 4 or 8 ohm speakers, so why would I ever set to 8? Also what would I want it set at? I have two pairs of paradigm titans and a paradigm center as well but I don't know what to set for this.

Something weird just happened also - I was playing david gray's white ladder which is a very bassy song. I found that at a volume of 3 with bass boost on (which in fact doesn't make it super-bassy, it just adds some on top to make it sound nice) I was getting clear distortion. The receiver is a sony str de 945 or something - cost around $450 US last year and is rated at 5X110 like I said. I can't imagine it was clipping at such a low level, but on the other hand it seems funny that these paradigms would be the cause of the problem too...now the back of the speaker did feel like a fan shooting a whack of air at me but still! I suppose what I'd want to do is get a sub for the system and turn the overall bass in the system down and let the sub take up the slack to aleviate the other speakers the low frequency work.

 

[bizmark]

<< Off topic slightly and on to your impedence thing - my home receiver has a switch at back for 4 or 8 ohms. I think it says set to 4 for 4 or 8 ohm speakers, so why would I ever set to 8? Also what would I want it set at? I have two pairs of paradigm titans and a paradigm center as well but I don't know what to set for this. >>



I saw that the Paradigms are rated at 8 ohms. I found a good review of your speakers here. FYI the second graph on the page shows the impedence vs. frequency plot (also plotted on the same graph is the phase shift -- something about which I have no clue). The first graph shows the amplitude (dB) vs. frequency. You have some very nice speakers! +/-2dB is very flat. However, the lower end is 70Hz, which is above what most consider 'bass'. I would definitely buy a subwoofer if you want to hear any loud bass from your system. Trying to play anything under 70Hz loudly on your speakers will result in distortion, pure and simple. Every system has its limits. Anyway, to get back to your question, I think that you should just leave it at 8 ohms. AFAIK on most amps this doesn't really make a difference anyway.



<< Something weird just happened also - I was playing david gray's white ladder which is a very bassy song. I found that at a volume of 3 with bass boost on (which in fact doesn't make it super-bassy, it just adds some on top to make it sound nice) I was getting clear distortion. The receiver is a sony str de 945 or something - cost around $450 US last year and is rated at 5X110 like I said. I can't imagine it was clipping at such a low level, but on the other hand it seems funny that these paradigms would be the cause of the problem too...now the back of the speaker did feel like a fan shooting a whack of air at me but still! I suppose what I'd want to do is get a sub for the system and turn the overall bass in the system down and let the sub take up the slack to aleviate the other speakers the low frequency work. >>



Yeah, see what I wrote above. There is simply a physical limit as to how low a 6" driver can go. I'd definitely get a sub if I were you. 70dB is way too high for the low end of your sound. Most people are satisfied with something in the 40Hz-50Hz range, which most 'tower' speakers can reach. A good sub ought to have you down in the 30s