pro amplifiers vs. home audio amplifiers

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This might seem like a strange question, but why do people seem to prefer to buy a home audio amplifier to use for their stereo as opposed to a pro audio amplifier, such as a Crown or Behringer? It seems that pro amplifiers are much better at playing low impedances, and are less expensive considering how much wattage they put out (i.e. The Behringer EP1500 puts out 260W X 2 into 8 ohms, whereas something in home audio with similar wattage, like the Parasound Halo A21 costs tremendously more money??) Is there any real difference in sound quality?? tia
 
Amp Shootout March 27-28 in Emeryville, California

Pro touring, install and cinema amplifiers are equipped with more protection mechanisms such as thermal, undervoltage, overcurrent, short circuit, too-low output impedance etc. Many people consider these circuits to be less than ideal for fidelity. Less is more, in other words. Straight wire with gain and all that.

I intend to measure the differences in late March when I perform an Amp Shootout. I'll compare 600wpc-into-4-ohm road-worthy amps with the Bryston 14B-SST dual monoblock amp, if Bryston is willing. The only protection I know of in the Bryston is thermal.

By the way, your Behringer amplifier example is a total 100% design rip-off of the QSC RMX line. Might as well spend the extra money and get an amp that is supported by the manufacturer. Behringer will let you twist in the wind if anything goes wrong. It's your choice...

-Bink
binkster@binkster.net

Amp Shootout details:
http://www.prosoundweb.com/news/0204/shootout.php
 
Hi,

Crown or Behringer

Ouch :smash: those two names just one word apart ;)

It seems that pro amplifiers are much better at playing low impedances

That's not true in general. But in particular there are more amps that are designed (and testet) to be used with lower load impedances. I assume we are speaking of class AB amplifiers here.

The problem is this: the power that an amplifier has to deliver is determined by the (complex) load impedance of the speaker and the output voltage of the amp only.

If the amp can deliver enough current into a connected load at it's nominal output voltage in order not to violate Ohm's law I=U/R and thus P=U*U*I, it is capable of powering a speaker with this impedance. And if it's not capable of delivering enough current, well, then it's just not. Actually it all depends on the power supply and the current capability of the used output transistors.

There are two well known "cheats" in (so called) professional amplifiers:

1. Exaggerating the output stage for much more current than is needed under normal load conditions (so that temperature rises not too much under heavy overcurrent).

2. Compensating the amplifier for high frequency stability in case the damping factor gets too low (e.g. so that the amp does not start to oscillate even when negative feedback is greatly reduced).

Both these steps will leave the whole issue to the power supply. As standard BJT or MOSFET transistors are relatively cheap, it's not very difficult to build many of them into the amp (e.g. twice as much as needed for just a couple of bucks).

The "cheat" is in the fact that a power supply will drop it's voltage under load. Just calculate for yourself: A significant drop of the maximum output voltage under heavy load will lead to an inherent reduction of the maximum output power.

This phenomenon is marketed by many (so called) pro manufacturers under the term "2 Ohm Stability" and does only mean that the amplifier won't break under a 2Ohm load. But it does not mean that the amp is usable with a 2Ohm load, as this power compression does sound absolutely awful and is what lets you recognise an amp as "overdriven" or "underpowered"...

and are less expensive considering how much wattage they put out

Mass production, expected price range in the pro audio community, saving on certain design criteria, etc.

In the (so called) high end audio scene, over-dimensioning is sometimes considered a must. Whatever one might think of that phenomenon, there are arguments pro and con.

But in pro audio gear manufacturing, as in every industry, every dollar counts! If a smaller toroid is sufficient to achieve design specifications, it is likely to be used. Same applies for supply capacitors, heatsinks, connector hardware etc.

It's not that all pro gear manufacturers do so, as you'll know, there's a wide price range, from ridiculously cheap to seriously expensive...

Is there any real difference in sound quality??

Sure. Actually any PA amp with the above considerations will need active cooling with fans, and for safety and reliability reasons they are usually kept running all the time. That's one thing that doesn't sound good!

OTOH, there are amps on the pro market that just don't sound very good, and only the designers know (or even don't) why there were neccessary things left out or flaws built in...

Despite that (e.g. let's imagine you've found an amp that has good sound up to good specs and that leaves it's fans off below a certain temperature), a PA amp can sound absolutely great with any kind of speakers. Building (very good) amplifiers is said to be an art, but that applies to all amps, independent of their intended use.

I've read of people who use PA amps at home where they just installed a temperature control unit for the fans. They are kept off until they are really needed. A very good approach, as it is very likely that one will be happy with those amps for a couple of decades :D

Greets,
Sebastian.
 
Disabled Account
Joined 2003
a lot of the problems Sebastian highlighted also exist for the home audio market, high-end or not. so I wouldn't say that they are unique to pro audio.

as to undersized transformers, i would say that it is more of a problem for home audio market as the pro audio gear buyers tend to be a little bit more sophisticated and the applications more demanding. in the home audio market, few will push the amp / avr to their rated capacity so an undersized transformer will do far less damage.

Having seen some pro audio gears, I wouldn't say that their transformers are undersized.
 
Having seen some pro audio gears, I wouldn't say that their transformers are undersized.

Great, You've seen some of the good pro audio gear :D

And in no way would I :cool:, I mean I, say that pro audio gear is worse than hifi stuff. Everytime I need some reference for a good implementation of a design concept, I search for schematics and applications on pro audio manufacturers' websites first, then on DIY hifi sources...
 
I think the principal advantages of (good) pro gear for home use are cost/watt, physical toughness (they are relativly resiliant to abuse by dumb humans) and flexability.

The disavantages tend to stem from the same considerations. They oftem achieve weight and cost reduction through the use fans and hum-drum appeareance, they often include protective circuitry (against those dumb and clumbsy humans) that unavoidably compromises noise and distortion to some degree, and they sometimes include features of little benefit for home use or which can result i home misuse.

Nonetheless, I would not dismiss them out of hand as there is a wide range of performance in home audio and there may be circumstances or work arounds offset the disadvantages of pro gear.
 
I think the Crown K1 and K2 work excellently in the home environment. They provide high output power, low power consumption, and no fan. my company has provided many of these amps to everyone from the Utah Symphony to high-end home theater enthusiasts to recording studios. Some other good pro amps that work in the home are the Hafler P series. They don't deliver as much power, but they sound very good. As for the lower end amps, i.e. Behringer, rate, Peavey etc., they don't belong in the home environment. They are designed for bands and D.J.'s that just can't afford a higher quality amp. The lower end amps tend to deliver less current, have more distortion, and are less reliable.

Now, the real question.......Would I use a pro amp for my citical listening? Sure I would, if it were a quality amp. Will it sound as good as a high powered Pass Labs amp? probably not. They are just different beasts. Keep in mind also, that many people consider Bryston to be pro gear. I've seen many Bryston amps in top-notch recording studios. Just my 2 cents (pence?)

Cheers,
Zach
 
information overload!

Hi everyone, thanks for the information about the amps. It sounds like in general there are circuits inside some of these amps which are unnecessary, and could create a difference in sound. The Crown K1 and K2 look very nice, but WAY too expensive! Part of the reason that pro amps seemed attractive was their relatively low cost for the wattage. Has anybody heard of a company called Inter-m? www.inter-m.com In particular, they have an Amp called the M2000 which looks really nice (you can find it on the site). Power output into 8 ohms is 710W X 2. I would like to run the following speaker system (passive):

Morel Mdt-30 Tweeters (200W power rating)
Morel MDM-55 Dome Mids (200W power rating)
Selenium WPU1207QCF 12" woofer (500W power rating)

This system would be used for home audio. Will this amp blow the tweeters and mids since they have a much lower power rating? Also, the amp costs about $699 U.S. dollars.. Is there a better amp out there in this price range? Tia

Dave
 
amp ratings vs. speaker ratings

Dave, you can get any amp for any speaker as long as you don't clip the amp or give the speaker too much voltage, heat or mechanical shock.

More speakers are blown from a too-weak amp than a too-strong amp. Strange, eh? Many, many more people have undersized amps and push them too hard which results in square waves being fed to the tweet. Ask any home stereo speaker repair shop which drivers are replaced more often for electrical failure and the answer will be HF drivers.

The professional sound reinforcement rule of thumb for buying amplifiers is to double the rms watt rating of the speaker. If your speaker can take 500w rms then you are shopping for a 1000w per channel amp. There's a bit of slop in this guide; you could settle for an 800w amp or splurge on a 1250w amp and still be safe. Call it 2x rms plus or minus 20%.

At home you are likely benefiting from a good deal of 'room gain' and are not listening to sustained loud music for hours. If you are primarily watchng DVDs and casually playing CDs for ambience, simply matching speaker rms to amplifier rms has made plenty of home listening rooms quite enjoyable.

If you get the bigger amp your music will sound cleaner -- the transients aren't being clipped. You will have more headroom. Typically in listening rooms there is (shhhhh) an acceptable percentage of very brief signal peaks that get clipped, limited or flattened. Going the budget route pretty much guarantees this occuring.

I say save up some extra money for the 2x rms solution. A side benefit is that your amplifier will last longer due to its not working as hard.

Regarding the Inter-M amplifiers, I have never heard one. I will be testing at least one and maybe three of the biggest models at my Amp Shootout March 27-28.
http://www.prosoundweb.com/news/0204/shootout.php

If you can wait until April 5 for your purchase, I'll have the test results for the Inter-M amplifiers available online and you can judge for yourself.

Good Luck -

-Bink
 
tweeter damage

Bink - how can you tell if you are giving the speaker too much voltage, heat or mechanical shock? This system will probably be played at a reasonable volume 80-90% of the time, so with the exception of transients, the speakers shouldn't see all that much power with a preamp, right? How does the preamp work? Say the power on the amplifier is turned all the way up. That would be 710W per side, regardless of how much the preamp is turned up, right?

As far as damaging speakers, someone here mentioned something about a square wave being the one that will damage a speaker driver. The inter-m seems to have a light on it saying when the amp is clipping. A clipped signal is a square wave right? So what would you do if the amp was clipping? Just turn it down or what? It wouldn't be fun to toast several hundred dollars of drivers (much less damage an amp!). Oh also you mentioned that the tweeters are the most likely speakers to be damaged.. How about the mids? The power dispersion between the speakers is very different too.. Is there a way to calculate what the maximum power each speaker would be receiving?

It sounds like the amount of power from the inter-m would be safe from what you're saying so far here.. Maybe that would be adequate. Rumor has it though, that these particular Selenium woofers need to be driven hard to work well.. But i definitely don't want to have to listen to music at blaringly loud volumes all the time. It's nice to have just ambient music most of the time.

I would like to hear about the results of your amplifier tests when they come out.. How many people are you using to compare the sound of these different amplifiers? It will be some time before these speakers are pieced together, so the amplifier purchase will be down the road a ways. Also, what criteria are you using to compare the various amplifiers? Clarity? Output power? Gain? etc etc.. TIA

Dave
 
IMHO - and based on experience - so-called "Pro" amplifiers are "better" simply because of the protection mechanisms built in. They tend to protect the stupid users (myself included :cool:... from alot of sins and keep working despite much abuse. Do they sound better? You wil have to listen and decide for yourself. But, I do know that you can drag a QSC or Crown behind vehicles, drop them off reasonable heights, stomp on them, and - generally - they continue to work! These are real benefits if you happen to be trying to make a living from their use :cool:.....!!!
 
Well, I have a Crown K1 for use with my basement PA/hi-fi speakers and a Crown K2 for use with my HT subwoofers.

I chose the Crowns because of their high efficiency, no fans, ruggedness, power and performance in the bass. But to keep the cost down, I bought them used. I understand that they are less sonically pristine at higher frequencies than some conventional AB SS amps, let alone tube amps of which I use the latter for my serious listening.

Btw, any opinions on how the Crown Class D amps stack up against Carver Pro Tripath amps sonically?
 
Wrong assumptions and more on Amp Shootout

bonsai171 said:
Bink - how can you tell if you are giving the speaker too much voltage, heat or mechanical shock?

Well, you burn some drivers up and find out! :dodgy: Or you could ask the factory what their speaker driver voltage limits are. Heat is probably not going to be a problem for you, so don't worry about it. Mechanical shock is the driver bottoming out and you can hear that as blats or farts at the point of a high-power kick drum hit or movie explosion or whatever. Back off the preamp if you hear the cones bottoming out. Before that point the distortion of your speaker will be increasing so you can listen for that as well.

This system will probably be played at a reasonable volume 80-90% of the time, so with the exception of transients, the speakers shouldn't see all that much power with a preamp, right?

Right.

How does the preamp work? Say the power on the amplifier is turned all the way up. That would be 710W per side, regardless of how much the preamp is turned up, right?

You make a couple of false assumptions. The speakers will see ~zero watts if there is no signal going to the amplifier. Also, the big knob on the front of the amplifier is not the POWER control or the VOLUME control, it is simply a means to match the sensitivity of the amplifier's input stage to the previous unit's output stage. Even if you turn your amp's 'volume' knob down to half, you can get maximum power out of your amplifier. It would take a much larger signal from the preamp to do so, though.

At any rate, you can power your speakers with a too-large amplifier and still be fine because you will have turned something down to compensate. If it is not too loud for your ears then it is probably going to be fine for your speakers.

As far as damaging speakers, someone here mentioned something about a square wave being the one that will damage a speaker driver. The inter-m seems to have a light on it saying when the amp is clipping. A clipped signal is a square wave right? So what would you do if the amp was clipping? Just turn it down or what?

In professional concert sound the clip lights are often engaged at every single kick drum hit. The smartest concert providers know that clipped transients add to the feeling of being loud. If you had a crazy clean and stupendously powerful concert system devoid of distortion, without that reference to the familiar concept of 'loud', the newbie band engineer will keep turning the super clean system up and up until they get the sense that it's loud. It has to have a bit of distortion or nobody will equate their auditory experience with the intense physical and emotional effort coming from the artist on stage.

Clipping the transients makes it sound loud.

Clip indicators on amps can mean you have 3dB of headroom left or they can mean there is absolutely no headroom left. You have to look at the amp specs or write to the manufacturer or test it on a bench to find out what level was selected for the indicator. Also, many pro amps have limiting or clip-softening circuits built in which means you can slam the hell out of them, make your speaker sound 'loud' and yet stay safely within speaker performance limits. HiFi home amps having some kind of soft limiting are more rare.

Clip lights at home? If you don't like the sound of clipped brief transients then turn it down and start planning for a bigger amp. If you can't hear anything wrong, then no problem. Don't do anything.

If the clip light stays mostly on you will be shopping for new speakers soon unless you turn down!

Oh also you mentioned that the tweeters are the most likely speakers to be damaged.. How about the mids? The power dispersion between the speakers is very different too.. Is there a way to calculate what the maximum power each speaker would be receiving?

Any wave can damage any speaker driver if it is too strong. The square waves are more evil because the little square corners contain a surplus of dog-whistle bat-echo HF energy that goes far beyond the freq response of the amp or the speaker. It's this aspect of square waves that fries HF drivers first. All that HF energy is turned into heat since the HF driver can't move that fast.

If you have a passive speaker crossover feeding your three bandpasses then the whole speaker system has to be examined as a whole. The passive crossover will burn up some amplifier power as heat meaning you need a bigger amplifier.

Calculating the max per driver has been done by the mfr. Adding a crossover and putting the drivers in a box complicates things. This is not my area of skill.

It sounds like the amount of power from the inter-m would be safe from what you're saying so far here.. Maybe that would be adequate. Rumor has it though, that these particular Selenium woofers need to be driven hard to work well.. But i definitely don't want to have to listen to music at blaringly loud volumes all the time. It's nice to have just ambient music most of the time.

Yes, if you can stand the fan noise then an amp that is rated like the Inter-M M2000 will do your speakers justice. Personally, I would go for a non-fan amp like the Crown K Series or their Studio Reference Series or similar known brands. Inter-M is a cheaper amp manufacturer whose gear is made in Korea. The model you are looking at may or may not be hiding audible problems. I hope to find out in late March.

If people say your woofers need to be driven hard then they are probably saying the woofers need more power to move the same amount. That is, they are less sensitive, possibly from having fewer wire turns in the voice coil or something like that. You don't have to make it loud to get the full benefit, you just have to have a bigger amp to get it the same volume.

I would like to hear about the results of your amplifier tests when they come out.. How many people are you using to compare the sound of these different amplifiers? It will be some time before these speakers are pieced together, so the amplifier purchase will be down the road a ways. Also, what criteria are you using to compare the various amplifiers? Clarity? Output power? Gain? etc etc.. TIA

I'll post the Amp Shootout results on or before April 5. The starting page I'll use currenty has my GEQ Shootout results but I'll scoot the GEQ Shootout over and make room for the Amp Shootout. Here's where you'll be able to see the Amp Shootout results when they are ready:
Bink's Shootout homepage

I'll be testing for a bunch of stuff. I'll be using a collection of really high quality test gear. The Audio Precision 2722 is the best piece there. It will test for noise floor, dyamic range, CMRR, IMD, THD+N, frequency response and much more. We'll be running the amplifiers into a resistive load so that they are working hard while they are being tested. We'll also look at power consumption via fast ammeter and we'll look at problems with AC waveform artifacts. We'll chart the maximum rms and peak output power levels attained and under what kind of distortion spectra. We'll also test under 90% and maybe 80% voltage conditions to emulate sagging AC supplies. We'll run burst tones into the amps to get an idea of their transient response and rise time. and we'll look at low-impedance protection circuit responses and at soft-limiting circuit results. We'll examine what happens with clipping and with limiting prior to clipping. Finally, we'll have the audience listen to different amplifiers under load and rate them in a randomized double-blind sequence. The room seats 200. Anybody at all who is interested can RSVP me for a seat. Attendance is free but limited.

-Bink
binkster@binkster.net
 
Any wave can damage any speaker driver if it is too strong. The square waves are more evil because the little square corners contain a surplus of dog-whistle bat-echo HF energy that goes far beyond the freq response of the amp or the speaker. It's this aspect of square waves that fries HF drivers first. All that HF energy is turned into heat since the HF driver can't move that fast.

This information above is the same claims written in that old JBL
document on how clipping can destroy speakers, etc. That was old
school thinking, but it has been proven by many that it's in slight
error. Many old school folks will not agree with the new because
that is all they've learned in the past. :hehe:

Exceeding power and mechanical limits is the main variables that
damages speakers. (fingers too) -- lol

A speaker doesn't care what waveform is playing, it just dissipates
heat. A clipped signal has the potential to drive the speaker with
2x more power than unclipped, hence the speaker blew up due to
extra power, not the waveform itself. I can listen to square waves
all day as long as I don't exceed the power or mechanical ratings of
the speaker. Music is a collection of complex waveforms, the speaker doesn't blow up when you play certain songs due to
unique waveforms produced by the music. /hehe

It's not good practice to clip your amplifiers, but many people do
clip on transients all the time. /hehe

If you analyze this statement
All that HF energy is turned into heat since the HF driver can't move that fast.

You have to wonder why a woofer doesn't blow up when
you send a 20khz tone. It's not going to be able to perform well
at this frequency - yet it doesn't blow up.... because you have
not exceeded it's power and mechanical rating.

Fun stuff.
 
thylantyr said:
If you analyze this statement
All that HF energy is turned into heat since the HF driver can't move that fast.

You have to wonder why a woofer doesn't blow up when
you send a 20khz tone. It's not going to be able to perform well
at this frequency - yet it doesn't blow up.... because you have
not exceeded it's power and mechanical rating.

At home your woofer is protected from 20k by the passive crossover which routes nearly all the 20k to the tweeter. If there were no crossover, you would simply be heating the woofer up. It would take a massive amount of 20kHz to make your woofer fail from the heat. In that respect, you are correct; a nominal amount of 20kHz is within the mechanical and power rating specs of the woofer and passive crossover combo.

I'm sure you know that I was talking about square waves as produced by clipped amplifiers, not square waves that might be a part of the input signal. Totally different scenario... The difference is that the square waves in your music that are within power spec are softly rounded by the frequency limits of the amplifier. The square wave which results from pushing your input signal past the amp's abilities has HF power completely unrelated to and higher than the amplifier's own freq response. An amp that has RFI LPF protection above say, 30kHz, will be able to put out much higher freqs like 40k, 50k and more if forced into square wave clipping.

But you knew that.

Me, I was talking about a tweeter, not a woofer. The tweeter is able to take some heat build up, but not nearly as much as the woofer since the tweeter build is smaller. Blowing tweets is what happens with running continued clipped-amp square waves.

-Bink
 
Again, the truth is probably somewhere in between, meaning both is true. A clipping amplifier produces squarewaves with sharp edges, and if you look at the spectrum (Fourier transformation) of a sharp edge, a lot of the energy is in the high frequency range, way above audible audio. That basically means that the tweeter gets more energy than it's supposed to get. The other thing is that an amplifier, while clipping, basically connects the output with the supply rails, without significant resistance - the transistors are fully switched through, and only the speaker limits the current.

A 100W RMS (8Ohm) Amplifier has +-40V supply rails. The RMS Wattage is calulated as follows: ( U*sqrt(2) / 2 )^2 / R_load, so in my example with 8 Ohm and 40V it's (40*0.707)^2 / 8 = 100 (W)
Now when the amp clips, it's basically DC for a short time, which means the correction factor of sqrt(2)/2 is gone. Note that this is inside the squared brackets! Basically that means the power doubles, so suddenly you have 200W DC into your speakers. Even worse, 8 Ohms means 8 Ohms impedance for AC in the audio range. The DC resistance may even be lower, again increasing the power. And, as already mentioned, if the loudspeaker can't reproduce the input frequency, then no energy can leave the system as sound, meaning it is dissipated as heat. Also, in most speakers, the tweeters have a much lower power rating. All these effects add up in the end, which has the result, that a clipping amplifier tends to destroy the tweeters first.
It is basically also possible to destroy the Woofers first (my brother tended to do that...). It's probably dependent on the speakers, and on how much you turn up the bass control.
I'm not sure how much my 'DC' argument really contributes to destroying tweeters, since they are usually coupled over a capacitor, which should keep DC away from them. It might though help to destroy woofers - suppose you crank up the bass, and clip a 20 Hz sine into a 20Hz square. That basically generates nice alternating DC pulses at 2 times full power, with 50ms duration (which is already rather long). These pulses easily travel through the woofer crossover coil, and put some stress onto the woofers.

This is my view on the whole topic. Concluding, clipping is bad. It is true, it adds to subjective loudness, but I rather prefer good sound quality, especially at home. And if I want to have the "loud" feeling, I can still use controlled compression, or better add some ground-shaking, clean bass - without clipping. And, yes, you need a lot of power for this :)
Comments on this are welcome :)
 
Me, I was talking about a tweeter, not a woofer. The tweeter is able to take some heat build up, but not nearly as much as the woofer since the tweeter build is smaller. Blowing tweets is what happens with running continued clipped-amp square waves.

-Bink


I can operate any tweeter continous clipped-amp square waves all day without blowing them up as long as I don't exceed
thermal and mechanical ratings of the tweeter. One very simple
example is listening to music with a hand held cd player and
ordinary headphones. I can boost the headphone volume
all the way up where there is massive signal clipping, yet
my headphones do not blow up -- because I have not
exceeded thermal or mechanical ratings :) :clown:
 
Hi

A couple of posts from the LAB:

http://www.live-audio.com/messages/archive7/85620.html
http://www.live-audio.com/messages/archive7/85641.html

They both concern the same original post, unfortunately I can't seem to navigate any more levels up in the thread.

And recently in the LAB lounge:

http://srforum.prosoundweb.com/viewtopic.php?t=392&sid=61e20940eaecbfd8ab2e6d62c37ed481

I am currently choosing between the Lab.Gruppen iP450 and the Crown CE1000 to drive my Dynaudio Audience 42 speakers. The speakers are rated at 150W long term, which is equal to the output power of the iP450, while the CE1000 is rated at 450W. The iP450 is passively cooled while the CE1000 has proportional speed fans. The CE1000 is slightly cheaper in the UK.

I am currently in favour of the iP450 since its distortion at full power is much lower than the Crown; 0.08% as compared to 0.5%. Also, I am concerned that any transients from loose connections, etc may destroy my speakers if used with the CE1000. Any opinions?

Thanks,
Tim Harrison

PS - Rod Elliott's site has a good description of power compression, here: http://www.sound.westhost.com/tweeters.htm
 
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