Amp design.

[PENG]

Actually I'm not worried about any distortion hurting my speakers and I don't even know what the THD value is on my amp. I was stating a point that I've read in the past that distortion is the main reason for driver failure which gave me the impression that it wasn't limited to clipping, but any kind of distortion. Again, that is just based on something I've read in the past and don't really know much about so by all means correct me if I'm wrong.

No problem, it is good to have forums like this so people can discuss interesting things. As mtry said, it's clipping that damages speaker, not harmonics. Harmonic of a signal is the component frequency of the signal that is an integer multiple of the fundamental frequency. A clipped signal will have a d.c. component, in addition to harmonics. The d.c. component is the main culprit that could damage a tweeter. As long the signal remain unclipped, the speaker doesn't care if there are harmonics or not. It is the listeners who have trouble dealing with the unpleasant sound of harmonics, especially odd (3r, 5th, 7th) harmonics, but not at <0.1% level.

 

[PENG]

Too much emphasis is being put on the rail voltage being limited,the only time this happens is when the distortion level reaches 0.005% & then it only takes 1/1,000th of a second to correct the distortion back to the standard.

When the rail voltage is adjusted the effect is visual not audible,the amp tells you when its doing this,keep in mind that you need to be pushing the speaker way harder than with a krell amp (used as example only) to make this happen ,when the adjustments happen you loose no output from the amp & the sound never changes nor do the spl's & no impact is lost.

When the power guard does its job the results can be compared directly against output using the output meters on the amp,ive yet to hear a difference but just incase im going to measure spl's at the same time the power guard comes into action.

Results to follow.

I agree with you. That's why I stated in my previous post that I prefer a 250W/500W/8/4 ohms amp to a 300W/8/4/2 ohms Mc amp (e.g. the 250W MC252), and I would love to have the MC602 that does 600W no matter what. Your 1200W mono are too much, so no thanks.

This volt/amp limitation thing only matters if you need say 250W continuous and frequently peak to 500W. In that case, the 250W Krell will edge out the MC252. I guess we are saying the same thing again?

 

[Ampdog]

I have just posted something similar under the thread "Please explain about ohms" in the forum General AV Discussions. (Don't seem to be able to post a direct transfer caption here - apology). I hope I can ask members to read there.

I could not read through all posts here, but my point there amounted to the original question being a bit of a non-question. Is a 500W amplifier better than a 200W amplifier? (apart from all the true arguments posted here regarding distortion, etc.) Basically I don't see a valid comparison - obviously it is better, but it depends on what one wants! As folks correctly said here, distortion comes into it, but 0,07% at 500W is not worse than 0,05% at 300W. What is the distortion of the 500W unit at 300W? It amounts to defining what is meant by "better", as was also raised here.

I also mentioned there that I have increasing irritation with someone being "forced" to buy a "300W into 4 ohm" amp if he needs 150W into 8 ohm, just because the loudspeaker impedance varies all over the chart. In this day and age it is not difficult to design loudspeakers with a fairly constant impedance over the audio frequency spectrum. Even then (and I apologise if I overlooked an earlier mention), one needs to take power supply time constants into consideration. I can put a 100 000uF storage capacitor in my 100W amplifier and rate it as 800 watt into 1 ohm (for 5 mS, which I conveniently do not state) - that is then a truthful statement but not an honest "up-rate". Not all such specs are stated as continuous.

 

[zumbo]

Well, it looks as though this thread has ran it's course!

 

[highfihoney]

I took some basic measurements,i stated in an earlier post that my speakers were rated for no more than 300 watts but after a quick glance at the manual i see i was mistaken,they are rated for 250 watts max.

I used the mcintosh mc1201 monoblocks,dynaco pat 6 preamp,mcintosh mvp 841 cd/dvd player,mcintosh xrt 22 line arrays,source material was pantera "far beyond driven".

I let the speakers warm up a bit before putting real power to them then took the power up to a constant 800 watts with peaks hitting over 1,000 watts,no indication of audible distortion or visual indication that the amps were limiting the distortion,pushed the power up to 900 watts & still no distortion,pushed a bit further to 925 watts with peaks comming close to 1,200 watts & noticed the amps were limiting the distortion,pushed even harder up to 1,000 watts constant & power gaurd lights were showing that distortion was being limited atleast 50% of the time.

At no time did i hear the sound smear nor did i hear a drop in spl's while the power guard was working,insert spl meter here.

Started out with the power level at 900 watts continuous with db levels at 117 & no distortion,pushed amps up to 1,000 watts constant & again distortion was being corrected atleast 50% of the time with db levels still in the 117 range,no drop in spl's seen on meter or heard & speakers were driven to their limit.

 

[Nuglets]

I used the mcintosh mc1201 monoblocks,dynaco pat 6 preamp,mcintosh mvp 841 cd/dvd player,mcintosh xrt 22 line arrays,source material was pantera "far beyond driven".

I let the speakers warm up a bit before putting real power to them then took the power up to a constant 800 watts with peaks hitting over 1,000 watts,no indication of audible distortion or visual indication that the amps were limiting the distortion,pushed the power up to 900 watts & still no distortion,pushed a bit further to 925 watts with peaks comming close to 1,200 watts & noticed the amps were limiting the distortion,pushed even harder up to 1,000 watts constant & power gaurd lights were showing that distortion was being limited atleast 50% of the time.


Started out with the power level at 900 watts continuous with db levels at 117 & no distortion,pushed amps up to 1,000 watts constant & again distortion was being corrected atleast 50% of the time with db levels still in the 117 range,no drop in spl's seen on meter or heard & speakers were driven to their limit.

I wish I had that kind of equipment to play with. That has to be fun.

 

[MDS]

It takes 900 watts to reach 117 dB in your room?

 

[PENG]

I don't know what to say, it seems like your 250W max speakers are indestructible!

 

[highfihoney]

It takes 900 watts to reach 117 dB in your room?

My current room is very large & my line array's contain 52 drivers & are not efficient,they crave power.

 

[highfihoney]

I don't know what to say, it seems like your 250W max speakers are indestructible!

Hi peng,i think it relates more to the quality of the power than it does to the speaker being indestructable,ive driven all my other speakers well beyond their rated limits using mac amps,for the longest time i was driving klipsch corner horns rated at 100 watts max with 500 watts & they would eat it up.

 

[mtrycrafts]

It is the listeners who have trouble dealing with the unpleasant sound of harmonics, especially odd (3r, 5th, 7th) harmonics, but not at <0.1% level.

Yep, so right The speaker doesn't care one iota. It is just another signal to reproduce.

 

[mtrycrafts]

Ahha! Clipping. An amp that resists ohm load resists this as well.

Like I said, this is not all about distortion.

Actually, an amp that resists but forced, will clip, including that Mc. Try to get it to double up on power as impedance is dropped. It cannot and must clip, or forced to turn off and not deliver.

 

[mtrycrafts]

I guess that makes sense considering somebody I know has a Marshall stack setup from the 50's for his guitar and it's still perfectly fine even with a bunch of distortion from effect pedals.

Certainly. Subs are measured for output performance to 10% distortion all the time. Difficult to hear that much in the sub, if not impossible.

 

[MichaelJHuman]

Actually I'm not worried about any distortion hurting my speakers and I don't even know what the THD value is on my amp. I was stating a point that I've read in the past that distortion is the main reason for driver failure which gave me the impression that it wasn't limited to clipping, but any kind of distortion. Again, that is just based on something I've read in the past and don't really know much about so by all means correct me if I'm wrong.

Driver damage is caused by exceeding their mechanical limits, especially their ability to deal with heat. Most of the power you send into a driver is converted to heat (I have seen estimations of 1% efficiency for drivers.) I suggest reading Rod Elliots excellent article on why drivers fail. It addresses some of the common misconceptions on why drivers blow.

http://sound.westhost.com/tweeters.htm

 

[highfihoney]

My current room is very large & my line array's contain 52 drivers & are not efficient,at 87 db they crave power.

I couldnt edit so i had to quote,i should also mention that my db measurements were taken from my listening position at 15.5 ft instead of the standard 3 ft.

 

[Nuglets]

Driver damage is caused by exceeding their mechanical limits, especially their ability to deal with heat. Most of the power you send into a driver is converted to heat (I have seen estimations of 1% efficiency for drivers.) I suggest reading Rod Elliots excellent article on why drivers fail. It addresses some of the common misconceptions on why drivers blow.

http://sound.westhost.com/tweeters.htm

Seems like a good read but I'm not quite sure that I understand it correctly. I have a 300WRMS amplifier and I have at quite a few instances driven it to a point where the clipping lights blink for very short periods of time with my current speakers and even more with my old CV's and they are still perfectly fine. I'm confused because he uses a 100W 'peak power' amplifier as an example but I hardly see amplifiers measured using peak power and most that I see are more than 100WRMS and if I remember right the peak power is double the RMS right? So with my amp that's 600W peak at 8Ohms and even higher when my speaker's impedance dips down. Now say I'm listening to music right around the amplifiers maximum(slightly below the level when the lights flash) and assume that the average is 10dB lower that would mean the average is 180W or less right around clipping and reaches peaks of 600W or less. And if I use the graph that assumes that with average music material, 15% of that is to the tweeter with a crossover at 3kHz which would be 27W continuous to that tweeter with my amp. My crossover in my speakers is at 2kHz so my tweeter would see even more than 27W continuous with peaks greater than 90W, right? Then when it clips slightly, since a square wave can be reproduce at double the maximum that would be 180W of clipped power. If no hi-fi tweeter can withstand more than 15W continuous why haven't I ever had to replace a tweeter? What am I missing?

 

[zumbo]

Actually, an amp that resists but forced, will clip, including that Mc. Try to get it to double up on power as impedance is dropped. It cannot and must clip, or forced to turn off and not deliver.

It doesn't try to double. How did you miss that point. If your statement were true, McIntosh would be the laughing stock of the audio world, and they certainly wouldn't be held in such high regard.

From the McIntosh site:

Unlike other high-current designs, The MC205 delivers the same 200 watts per channel into both 4-ohm and 8-ohm loudspeakers. The Dynamic Power Manager automatically controls and optimizes the power supply’s voltage and current balance delivering higher voltage that 8 ohm speakers require, and automatically adjusting for current-hungry 4 ohm speakers.


Power Guard
Power guard is another patented McIntosh innovation. When an amplifier is overdriven, by a sudden music peak, for instance, it can "clip" and send a burst of damaging energy to your speakers. This is the most common cause of damage to the "tweeter" element of speakers. Power Guard, on optical-electronic circuit, prevents clipping by instinctively turning the volume down, and then back up, in as little as 1/1000 of a second. Hard clipping is avoided, and speakers are safe while ensuring maximum safe power output.

 

[Nuglets]

I believe I did the math wrong in my previous post and my numbers now come out to be 13.5W continuous to a tweeter with a 3kHz crossover using my amp. That is if I'm doing the math correctly this time. I am taking my peak value and dividing it by 2(10/3) to get the -10dB average to get 90W and then take 15% of that to get the approximate peak power to the tweeter. A 3dB increase/decrease is will double/half the amount of power correct? Where does he get 10W average if the average is 10dB below the peak which is 100W? Wouldn't the correct value be 15W?

EDIT: I think I'm wrong again...I take the peak value and divide it by 2^(10/3) right? If so, I get around 60W average to the entire speaker and 15% of that gives me 9W continuous to the example tweeter and probably a bit more to mine. I think I'm slowly answering my own questions about the article but if anybody can help clarify my understanding it will be much appreciated.

 

[PENG]

Hi peng,i think it relates more to the quality of the power than it does to the speaker being indestructable,ive driven all my other speakers well beyond their rated limits using mac amps,for the longest time i was driving klipsch corner horns rated at 100 watts max with 500 watts & they would eat it up.

I understand you point but 900W continuous should still fry a speaker that is rated for 250W max. There is no way out to this.

There may be another explanation, if that 900W continuous you referred to was read off the MC1201's wattmeter, then depend on the position selected, it may be reading either the instantaneous peaks when in the watts position or the peaks of a sequence of peaks if in the hold position. In either case, that meter does not seem (not 100% sure) to be for indicating rms watts. For a pure sine wave, V or I pk=sqrt2*V, or Irms so peak power will be 2 times rms power. Music waveforms are not sinusoidal so the 2 to 1 ratio may not hold true and is likely much higher. So the true rms power into you speakers may be nowhere near the 900W indicated on the 1201's wattmeter. I am thinking of emailing McIntosh and ask them to clarify a little more how those wattcmeters work and what exactly do they indicate.

As a sidebar, I know you did not say that in you post but others had in the past, about the inverse square rule for SPL vs distance. That rule is only true for open field condition. In a room it depends on the acoustic environment. In my listening environment, whether I place my meter at 6 ft away or 16 ft away, the SPL level does not change much, in some position it actually goes up slightly with distance.

 

[PENG]

Hi peng,i think it relates more to the quality of the power than it does to the speaker being indestructable,ive driven all my other speakers well beyond their rated limits using mac amps,for the longest time i was driving klipsch corner horns rated at 100 watts max with 500 watts & they would eat it up.

I understand you point but 900W continuous should still fry a speaker that is rated for 250W max. There is no way out to this.

There may be another explanation, if that 900W continuous you referred to was read off the MC1201's wattmeter, then depend on the position selected, it may be reading either the instantaneous peaks when in the watts position or the peaks of a sequence of peaks if in the hold position. In either case, that meter does not seem (not 100% sure) to be for indicating rms watts. For a pure sine wave, V or I pk=sqrt2*V, or Irms so peak power will be 2 times rms power. Music waveforms are not sinusoidal so the 2 to 1 ratio may not hold true and is likely higher. So the true rms power into you speakers may be nowhere near the 900W indicated on the 1201's wattmeter. I am thinking of emailing McIntosh and ask them to clarify a little more how those wattcmeters work and what exactly do they indicate.

As a sidebar, I know you did not say that in you post but others had in the past, about the inverse square rule for SPL vs distance. That rule is only true for open field condition. In a room it depends on the acoustic environment. In my listening environment, whether I place my meter at 6 ft away or 16 ft away, the SPL level does not change much, in some position it actually goes up slightly with distance.