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EMOTIVA Thread Q&A [TECHNICAL TALK ONLY] - Page 559

post #16741 of 17194
Quote:
Originally Posted by RichB View Post


The trouble with the all amps sound the same and most have enough power is they are right, except when they are wrong.

The trouble with the all amps sound different vuewpoint postings is that they are invariably based on sighted, casual evaluations.

Quote:
My experience with Receivers" is that " They sound flat long before they sound bad due to excessive clipping.

Please see former comments about sighted evaluations. The above is the sort of thing for which finding applicable reliable evidence for can be very hard.
Quote:
There is data out there that supports the notion that amps when driven compress before they produce enough objectionable distortion.

Really. Got any evidence to share? Links?
Quote:
Each persons speakers, room, and listening preferences differ.

That's undeniably true but if you consider the logical implications of that, why do we share opinions about gear? You are a person, no? If so. then your speakers, room, and listening preferences differ from mine and there is no logical reason for your experiences to be indicative or predictive of mine should I be foolhardy enough to follow your advice.

The other problem is that you have made claims that if true should be widely observable by technical means. Where are the reliable technical observations that confirm the above claims about amplifier compression?
Quote:
I can tell when the A51 is running out of gas driving my Salons and I am not hearing distortion.
Amps can simply fail to produce the power for a demanding peak and then sail along after that.
In fact, that is a good design choice for an AVR.

Here is a thread on AH that discusses compression:

http://forums.audioholics.com/forums/amps-pre-pros-receivers/88388-do-modern-amplifiers-compress-before-clipping.html

Which kicks off with the following comment:

"The answer is no, they don't compress before clipping. The linked article also said so, it clipped, then compressed if the user continue to turn the volume up beyond the clipping point. If you us Fourier analysis to breakdown the clipped waveform into individual harmonics, the low frequencies would be clipping long before the high frequency components do, so until then the amp would be compressing, as the author called it."

Obviously, not reliable evidence to support the claim made above. Fail!

The above reference is well known and also completely denies the claim made above about amplifiers commonly compressing before clipping.

Instead it shows how clipping has the unexpected result of allowing power delivered to loudspeakers to continue to increase as equipment is pushed further and further into clipping. It might be subtitled "How to get 500 watts out of a 100 watt amplifier". The answer lies in the relatively high crest factor of music, not any undocumented property of audio amplifiers.
post #16742 of 17194
Quote:
Originally Posted by Tong Chia View Post

Could be either or both, the best way is to measure it and find out.
The most basic measurement setup requires a 1kHz sinewave signal source, an ac voltmeter and a SPL meter such as the ones Radioshack sells.
The sinewave signal source can be wav files or test tones from a cd played back from a PC or Smartphone/Tablet.

Under normal conditions, a doubling in the input voltage will result in a doubling of the voltage at the amp's output and a 6dB increase in SPL
Keep doubling the input voltage from the signal source to the amp until compression occurs.

Under compression this will no longer hold true, if the amp output doubles and the SPL shows less than a 6dB change, take a closer look at the speaker.

That's a good way to ge the power usage and use to compute power usage.
However, a bookshelf speaker might be rated at 80 DB at 1 watt 50 to 20K +/- 3 DB.
However, at 100 DB those woofers are not going to cut it. They may not even cut it if you are using a sub.

- Rich
post #16743 of 17194
Quote:
Originally Posted by arnyk View Post

The trouble with the all amps sound different vuewpoint postings is that they are invariably based on sighted, casual evaluations.
Please see former comments about sighted evaluations. The above is the sort of thing for which finding applicable reliable evidence for can be very hard.
Of course they do because the caviats are big enough to drive a car through.
At what volume level, with what speaker efficiency and phase angle, and in what room.
Quote:
Originally Posted by arnyk View Post

Really. Got any evidence to share? Links?
I did.
Quote:
Originally Posted by arnyk View Post

That's undeniably true but if you consider the logical implications of that, why do we share opinions about gear? You are a person, no? If so. then your speakers, room, and listening preferences differ from mine and there is no logical reason for your experiences to be indicative or predictive of mine should I be foolhardy enough to follow your advice.
I offer no advice, just my experience.
Quote:
Originally Posted by arnyk View Post

"The answer is no, they don't compress before clipping. The linked article also said so, it clipped, then compressed if the user continue to turn the volume up beyond the clipping point. If you us Fourier analysis to breakdown the clipped waveform into individual harmonics, the low frequencies would be clipping long before the high frequency components do, so until then the amp would be compressing, as the author called it."

Obviously, not reliable evidence to support the claim made above. Fail!
The above reference is well known and also completely denies the claim made above about amplifiers commonly compressing before clipping.
The measurements are conceptually very simple. When there is insufficient power, the amplifier will clip that part of the signal. The listener is not going to hear that missing sound. The rest of the signal is produced. Newer amps do this well.

You cannot fail be because I am not your student. tongue.gif
Quote:
Originally Posted by arnyk View Post

Instead it shows how clipping has the unexpected result of allowing power delivered to loudspeakers to continue to increase as equipment is pushed further and further into clipping. It might be subtitled "How to get 500 watts out of a 100 watt amplifier". The answer lies in the relatively high crest factor of music, not any undocumented property of audio amplifiers.

Show me how that amplifier could ever produce 500 watts.

I am here to share experiences and data because all of systems are different.
I have no interest in changing your opinion.

- Rich
Edited by RichB - 1/2/14 at 6:40am
post #16744 of 17194
Quote:
Originally Posted by RichB View Post

Quote:
Originally Posted by arnyk View Post

The trouble with the all amps sound different vuewpoint postings is that they are invariably based on sighted, casual evaluations.
Please see former comments about sighted evaluations. The above is the sort of thing for which finding applicable reliable evidence for can be very hard.
Of course they do because the caviats are big enough to drive a car through.
At what volume level, with what speaker efficiency and phase angle, and in what room.

Obviously I was hoping that you would find, data points chosen to strengthen your claims, and not weaken them. It appears to me that you can't find any relevant data points at all because the ones you provided weakened what appeared to me to be your primary claims.
Quote:
Quote:
Originally Posted by arnyk View Post

Really. Got any evidence to share? Links?
I did.

Not if your goal was to make your account of your experiences relevant to others. They all went against your claims.
Quote:
Quote:
Originally Posted by arnyk View Post

That's undeniably true but if you consider the logical implications of that, why do we share opinions about gear? You are a person, no? If so. then your speakers, room, and listening preferences differ from mine and there is no logical reason for your experiences to be indicative or predictive of mine should I be foolhardy enough to follow your advice.
I offer no advice, just my experience.

OK, the name of the game seems to be hide behind the exact words chosen, and ignore the ones that detract from your claims.

To rephrase my questioin to get around an obvious attempt to avoid the question, why should anybody want to read about your experiences if they are meaningless to anybody but their writer?
Quote:
Quote:
Originally Posted by arnyk View Post

"The answer is no, they don't compress before clipping. The linked article also said so, it clipped, then compressed if the user continue to turn the volume up beyond the clipping point. If you us Fourier analysis to breakdown the clipped waveform into individual harmonics, the low frequencies would be clipping long before the high frequency components do, so until then the amp would be compressing, as the author called it."

Obviously, not reliable evidence to support the claim made above. Fail!
The above reference is well known and also completely denies the claim made above about amplifiers commonly compressing before clipping.

The measurements are conceptually very simple. When there is insufficient power, the amplifier will clip that part of the signal.

That's not compression, its umm, errr, clipping. ;-)
Quote:
The listener is not going to hear that missing sound.

Of course the listener hears the potential sound that is lost due to clipping, or are you going to further demolish your claims and make your experiences seem even more irrelevant by claiming that clipping is not audible?
Quote:
Quote:
Originally Posted by arnyk View Post

Instead it shows how clipping has the unexpected result of allowing power delivered to loudspeakers to continue to increase as equipment is pushed further and further into clipping. It might be subtitled "How to get 500 watts out of a 100 watt amplifier". The answer lies in the relatively high crest factor of music, not any undocumented property of audio amplifiers.

Show me how that amplifier could ever produce 500 watts.

An amplifier is insufficient for the desired SPL levels such that a music signal with a THX standard peak to average ratio or crest factor of 20 dB is barely under clipping. The volume is further increased and clipping becomes far more severe.

When the music was barely less than clipping the so-called 100 watt amplifier was producing 100 watts on the peaks and it cannot produce any more clean power than that. We call that 100 watts of undistorted power. Due to the crest factor of music of 20 dB, the average power level is 20 dB less than 100 watts or 1 watt. None of this is any surprise to even poorly informed audiophiles, which neither of us appears to be.

When the music was significantly clipping the so-called 100 watt amplifier would still only producing 100 watts on the peaks and it still cannot produce any more power than that. However, since the peaks were now the result of heavy clipping the average power of the signal has increased dramatically to perhaps 5 watts If we relate this 5 watts of distorted power to its equivalent undistorted power would be, the 5 watts of average power would be the equivalent of what we would expect from a 500 watt amplifier.

This would be a surprise to many well informed audiophiles.

I admit and would even stipulate that my initial comments could be interpreted as being misleading and perhaps even poorly formed, but the real-world point stands. By allowing nominal amounts of clipping we can get average power levels that we would expect from a 500 watt amplifier, only out of a 100 watt amplifier.
Quote:
I am here to share experiences and data because all of systems are different.
I have no interest in changing your opinion.

I think that the gist of your post may be an attempt to change the laws of physics. ;-)

I don't think that was your intention, but that may have been a logical consequence.
post #16745 of 17194
Quote:
Originally Posted by Knucklehead90 View Post


...And if you think people are eager to help you spend your money read some of the amp recommendation threads on the Emotiva Lounge. Guys mulling over the idea of buying the Mini-X amp vs the UPA-200 to power their 101db Klipsch are soon being urged to buy the XPR-1 mono-block amps because "you can never have too much headroom!" For the most part its just absurd.

I've never been to the Emotiva Lounge but found it interesting that several people who made this claim here and started posting over there have gone on to more expensive amps claiming they sound even better with their Klipsch RF-7s.
post #16746 of 17194
From this article:

http://www.adx.co.nz/techinfo/audio/note128.pdf
Quote:
Well, it was reasoned, if there is enough low frequency
energy to clip the amplifier, then it perhaps would produce
enough high frequency distortion products (as a result of
clipping) to blow up the tweeter.
This theory convinced many in the early 70’s and slowly
evolved into “fact”. While doing research into the reliability
and protection of power amplifiers,
I had to study how the typical consumer used amplifiers and speakers.
I found that clipping is a common occurrence and is not as audible as most people think.
Quote:
Let’s look at the square wave example shown in Table 1
(at left). Fourier analysis shows the harmonic structure.
As you can see, the total amount of power left to make it
through an ideal 1kHz crossover (and on to the tweeter) is less
than two watts (0.83 + 0.589 = 1.419W). Hardly a problem.
And remember, this simulates severe overdrive of a 100 watt
amplifier with a sine wave to make an ideal square wave.
Driving it harder will not increase the harmonics.
This analysis shows if a small tweeter that only handles 5
or 10 watts is used in a 100 watt speaker system it would not
blow out, even under square wave conditions. Yet it does.
It takes a lot more than this to cause major failure. So
what’s happening?
Compression is what’s happening [3].
Today’s newer higher quality amplifiers have greater
dynamic range and sound better when clipped with musical
transients than older amplifier designs. So it is more likely for
a user to overdrive and clip newer amplifiers on low frequency
dynamic peaks because of lower audible distortion.
This results in compression of the dynamics of the music.[/B
]The[high frequencies get louder but the low frequencies can’t. This
may be heard as an increase in brightness of the sound. Some
may simply interpret it as louder with no change in tonal
balance.

For example, in a 100 watt amplifier, as you turn up the
level, the low frequency components will limit (clip) at 100
watts. Meanwhile the high frequency components continue to
increase until they (the high frequencies) approach the 100
watt clipping point.
Quote:
Let’s assume a musical signal with low and high frequency
components driving a 100 watt (8 ohms) amplifier. We use a
low level/high frequency sinewave mixed with a high level/
low frequency sinewave burst. (See Fig.2). The high frequencies
reproduced by the tweeter are at least 10dB lower in level
than the low frequencies. Now as we turn up the amplifier to
clip the signal (3dB overdrive—See Fig.3). Notice that only
the low frequency burst portion of the waveform clips but the
high frequency portion increases in level. The clipping, of
course, produces harmonics but not nearly as much as the
square waves discussed earlier. The amplitude of the high
frequencies went up by 3dB in relation to the low frequency
fundamental. (3dB compression).
Quote:
Now it is easy to see how the high frequency portion
exceeds the 5 or 10 watts tweeter rating. Sure, clipping is
producing extra harmonics but they never approach the levels
of the amplified high frequency source signals.
It may be argued that the signal’s distortion would be
intolerable. Don’t fool yourself. It really surprises people how
much clipping they tolerate before they cannot listen anymore.

Just disconnect the clipping indicator on a power amplifier
and see how loud someone drives it. Watch the amplifier
output with an oscilloscope. There will be a surprising level of
clipping. 10 dB clipped off the top of low frequency transients
is not an uncommon occurrence when the purpose is to
impress your neighbors.
Quote:
WHAT CAN WE DO ABOUT IT?
If we can prevent an amplifier from clipping, we could
better utilize our loudspeakers. Limiters play an important role
in preventing clipping and the resulting amplitude compression.

I think it is a well written and sensible argument.
It is likely that many listening to AVR's at near reference levels with full range speakers are actually clipping their amps into compression while not realizing it.

Some class A/B amps contain limiters.
Class D amps have soft clipping circuits...
Not everyone needs an external amp, but some do.

- Rich
post #16747 of 17194
Quote:
Originally Posted by RichB View Post


I think it is a well written and sensible argument.

It is, until it is misrepresented and misinterpreted.

The article above was written about amplifiers in general, not just AVR amps.

FAIL general application to AVRs

Reality is that many audiophiles are buying external amps that have less power at clipping with music than the AVR that they are hoping to "upgrade".
Quote:
It is likely that many listening to AVR's at near reference levels with full range speakers are actually clipping their amps into compression while not realizing it.

So what. As I showed, many AVR/Speaker/Room combinations can reach peak levels (Reference+20dB) without clipping:



If a 50 wpc amp can exceed Peak THX level with dBs to spare where is your agument now?
Quote:
Some class A/B amps contain limiters.

True for many pro sound amps, but no known AVRs. The limiters in pro audio amps are typically optional.

FAIL any application to AVRs,
Quote:
Class D amps have soft clipping circuits...

Very few AVRs have class D amps.

FAIL general application to AVRs,
Quote:
Not everyone needs an external amp, but some do.


Of course. The only question is when.

After what 12+ years of experience with AVS and other consumer forums, IME the leading stimulus for external amplifiers is flaming cash in the wallet.
post #16748 of 17194
Quote:
Originally Posted by arnyk View Post


The trouble with the all amps sound different vuewpoint postings is that they are invariably based on sighted, casual evaluations.
Please see former comments about sighted evaluations. The above is the sort of thing for which finding applicable reliable evidence for can be very hard.
Really...

 

But that's the thing, those in the amps sound different camp do not insist that all amps sound different, just that it's possible for amps to sound different.

The trouble with DBT is that they do not prove all amps sound the same.  Here's part of a post that discusses this:


 

Quote:

A DBT can never prove that A=B. It can only statistically conclude that a person under test conditions could not differentiate A and B within (and ONLY within) the confines of that particular test.

 

The problem just in the statistics is that the more subtle something is (harder to differentiate) the more reliability and validity is needed. So if I have a test set up where I want someone to differentiate the colour Red versus Green (assuming the person isn't colour blind and the room is lit) then I only need one trial - hold up the colour card - the subject says Green correct. 

If however the test is between say 3 cards and all three are variations of red and I am asking which variation of Red it is - I will need to show the cards more than once to get reliable findings.

In audio statistical significance to the .05 level would be 9 correct out of 10. So if the subject correctly identifies the Krell amp over the Crown amp then he will be deemed to get the result better than chance. (This meets the statistical requirement and some would then say "he can hear audible differences therefore the Krell sounds different that the Crown). These some people would be wrong. The Krell has not been proven to sound different - the SUBJECT has been proven to be able to differentiate better than chance is all.

 

if you had a subject who got 6/10 he would be deemed a failure statistically. The problem with this notion is that if the subject scored 6/10 ten times with one miss for 59/100 he would meet statistical significance to the exact same 0.5 level (equal to 9/10). In both cases the subject would be deemed to be able to differentiate A from B and thus PASS the DBT. More trials increases reliability of the test. Like I say the issue here is most of thes trials are small - John got 6/10 he can't hear the difference - if he scored that or better 10 times - in fact he would be deemed to be able to tell the difference. It's quite a glaring issue.

Just food for thought.

post #16749 of 17194
Quote:
Originally Posted by Zen Traveler View Post

Quote:
Originally Posted by Knucklehead90 View Post


...And if you think people are eager to help you spend your money read some of the amp recommendation threads on the Emotiva Lounge. Guys mulling over the idea of buying the Mini-X amp vs the UPA-200 to power their 101db Klipsch are soon being urged to buy the XPR-1 mono-block amps because "you can never have too much headroom!" For the most part its just absurd.

I've never been to the Emotiva Lounge but found it interesting that several people who made this claim here and started posting over there have gone on to more expensive amps claiming they sound even better with their Klipsch RF-7s.
And their reason for putting a 1 mega watt amp on each of those RF-7's? Because those speakers dip all the way down to 3.7ohms in the lower midrange! Getting someone to listen to reason in the face of 6 or 10 guys telling the guy he 'needs' that 1 mega watt amp vs one or two saying slow down and think about how much you 'really' need... Well - you know the end of that story.

Amp headroom is best illustrated by a car analogy IMO. Think of the guy who has this one big hill to climb on his way home each day from work. His current car 'just' makes the hill - the accelerator pedal is 90% to the floor. He crests the hill each day without slowing down - and is entirely happy with the cars performance. When it comes time to buy a new car he is looking for a car with similar performance and states that to the salesman - the salesman keeps steering him to the higher HP (and more $'s) cars - the guy questions why he needs that much power. The answer: "You can never have too much HP." Of course all his buddies approve! All the guy needs (all he *wants*) is enough HP to get over that hill at speed. The Emotiva Lounge guys would have him in a Corvette at the least - and a Ferrari if they can convince - but all he needs/wants is the Toyota Corolla.

And how do those new 1 mega watt mono's sound with the 101db efficient speakers? I think the 'McGurk effect' can best answer that one:
post #16750 of 17194
Quote:
Originally Posted by arnyk View Post

It is, until it is misrepresented and misinterpreted.

The article above was written about amplifiers in general, not just AVR amps.

FAIL general application to AVRs

Reality is that many audiophiles are buying external amps that have less power at clipping with music than the AVR that they are hoping to "upgrade".

AVRs have amps which may or maynot be powerful enough for the individuals system.
This is the Emotiva thread, the XPA and above amps can handly out perform most any AVR.
I read the article very carefully and others can do so and draw their own conclusions.
Quote:
Originally Posted by arnyk View Post

So what. As I showed, many AVR/Speaker/Room combinations can reach peak levels (Reference+20dB) without clipping:



If a 50 wpc amp can exceed Peak THX level with dBs to spare where is your agument now?
True for many pro sound amps, but no known AVRs. The limiters in pro audio amps are typically optional.

FAIL any application to AVRs,

FAIL general application to AVRs,

Oh no, what will this do to my grade-point-average? tongue.gif
Quote:
Originally Posted by arnyk View Post

Of course. The only question is when.

After what 12+ years of experience with AVS and other consumer forums, IME the leading stimulus for external amplifiers is flaming cash in the wallet.

Well with almost 15 years of experience on AVS... tongue.gif

Emotiva is amoung the lighter of the wallet lifters, however, lower-back issues are another subject smile.gif

And speakers with 4 ohm impedance and a 45 degree phase angle require 4 times the power and some serious heat sinks.
Unfortunately, all amplififiers are not equally gifted at driving reactive loads.

I do not feel comfortable with zero data insisting that those who purchased these affordable amps and experienced a benefit are deluded.

I think you are confusing me with someone interested in an argument. wink.gif

- Rich
Edited by RichB - 1/3/14 at 12:55pm
post #16751 of 17194
Quote:
Originally Posted by Knucklehead90 View Post

And their reason for putting a 1 mega watt amp on each of those RF-7's? Because those speakers dip all the way down to 3.7ohms in the lower midrange! Getting someone to listen to reason in the face of 6 or 10 guys telling the guy he 'needs' that 1 mega watt amp vs one or two saying slow down and think about how much you 'really' need... Well - you know the end of that story.


Believe me, I understand. Again, the great thing about this being a written forum is that you can see the claims made several years ago and then where some of them go from there. Fwiw, it's not about Watts per channel as much as the power supply being able to handle the impedance dips at the volume one wants to listen with an RF-7s based Home Theater.
post #16752 of 17194
Quote:
Originally Posted by cwt View Post

Thats true but there is one coming very soon ; not the reference line though cool.gif

I'd be interested in an XPR-3!biggrin.gif
post #16753 of 17194
Quote:
Originally Posted by audio4life View Post

Quote:
Originally Posted by arnyk View Post

The trouble with the all amps sound different vuewpoint postings is that they are invariably based on sighted, casual evaluations.

Please see former comments about sighted evaluations. The above is the sort of thing for which finding applicable reliable evidence for can be very hard.

Really...

But that's the thing, those in the amps sound different camp do not insist that all amps sound different, just that it's possible for amps to sound different.

Then there is no controversy because the "good amps sound the same" school accepts that bad amps sound different and exist, which is why the limit their claims to good amps.

But there obviously is a controversy, so there must be a lot of people insisting that good amps sound different. IME, its everybody who has money burning a hole in their pockets, because their old amp has to sound bad and the new amp has to sound good (IOW different) or there would be no logical reason for them to waste spend their money!
Quote:
The trouble with DBT is that they do not prove all amps sound the same.\

You're sadly misinformed because proving that all amps sound the same is not anybody's goal, at least not anybody with a brain. You must not be well-informed in this area to make this sort of a mistake.
Quote:
 Here's part of a post that discusses this:

Initial caveat - just because it was posted by some potentially technically illiterate audiophile eggspurt means absolutely nothing.

Quote:
A DBT can never prove that A=B. It can only statistically conclude that a person under test conditions could not differentiate A and B within (and ONLY within) the confines of that particular test.

The problem just in the statistics is that the more subtle something is (harder to differentiate) the more reliability and validity is needed. So if I have a test set up where I want someone to differentiate the colour Red versus Green (assuming the person isn't colour blind and the room is lit) then I only need one trial - hold up the colour card - the subject says Green correct. 


If however the test is between say 3 cards and all three are variations of red and I am asking which variation of Red it is - I will need to show the cards more than once to get reliable findings.


In audio statistical significance to the .05 level would be 9 correct out of 10. So if the subject correctly identifies the Krell amp over the Crown amp then he will be deemed to get the result better than chance. (This meets the statistical requirement and some would then say "he can hear audible differences therefore the Krell sounds different that the Crown). These some people would be wrong. The Krell has not been proven to sound different - the SUBJECT has been proven to be able to differentiate better than chance is all.

if you had a subject who got 6/10 he would be deemed a failure statistically. The problem with this notion is that if the subject scored 6/10 ten times with one miss for 59/100 he would meet statistical significance to the exact same 0.5 level (equal to 9/10). In both cases the subject would be deemed to be able to differentiate A from B and thus PASS the DBT. More trials increases reliability of the test. Like I say the issue here is most of thes trials are small - John got 6/10 he can't hear the difference - if he scored that or better 10 times - in fact he would be deemed to be able to tell the difference. It's quite a glaring issue.

Just food for thought.

Only food for thought for people who don't understand the issues. The above post was obviously written someone who was making up his knowledge base about audio DBTs as he went along. I could tear it apart line by line, but I strongly suspect that I'm dealing with a true believer...

BTW just so you can do things right the next time, its good form to give some kind of footnote for a long quote that is key to your claims.

The actual source of that quote appears to be:

http://www.audiokarma.org/forums/showpost.php?s=78677ba6f018537bf17ae8857c65f6bc&p=7342915&postcount=234

Not exactly a paragon of great technical expertise or unbiased opinions. The author is for all intents and purposes that well known person "Anonymous poster hiding behind a nonsense handle"
post #16754 of 17194
Quote:
Originally Posted by RichB View Post

AVRs have amps which may or maynot be powerful enough for the individuals system.
This is the Emotiva thread, the XPA and above amps can handly out perform most any AVR.
I read the article very carefully and others can do so and draw their own conclusions.
Oh no, what will this do to my grade-point-average? tongue.gif
Well with almost 15 years of experience on AVS... tongue.gif

Emotiva is amoung the lighter of the wallet lifters, however, lower-back issues are another subject smile.gif

And speakers with 4 ohm impedance and a 45 degree phase angle require 4 times the power and some serious heat sinks.
Unfortunately, all amplififiers are equally gifted at driving reactive loads.

I do not feel comfortable with zero data insisting that those who purchased these affordable amps and experienced a benefit are deluded.

I think you are confusing me with someone interested in an argument. wink.gif

- Rich


I been reading this chain of posts. They are interesting. To generate some discussion I've written the following:


One of the paragraphs in this post needs some clarification by the author:

'And speakers with 4 ohm impedance and a 45 degree phase angle require 4 times the power and some serious heat sinks.
Unfortunately, all amplififiers are equally gifted at driving reactive loads.'

1) Does the author states that, "All amplifiers are equally gifted in driving reactive loads.?"

This doesn't fit with my experience with amplifiers. It may be a typo. I make a lot of those; likely some below.

2) Does the speaker in the example have a constant 45 degree phase angle with an impedance of 4 ohms at all frequencies?

That seems like a very unusual speaker. Typically the value of impedance and phase angle vary with frequency. That make calculation of the effective impedance and phase angle seen by the amplifier at any point in time, with complex music signals at different frequencies and with different phase angles, to be a harder task than with sine waves.

The minimum value of the impedance seen by the amplifier, which may not be seen depending on the design of the crossover, will be the impedance of the speaker at a zero phase angle, that is, the resistance. In this example I guess that the minimum impedance would be 2.8 ohms if the 4 ohm figure is the magnitude of the impedance at a 45 degree phase angle. Of course if 4 ohms is the minimum impedance (the pure resistance of the load) then the impedance at the 45 degree phase angle will be about 5.7 ohms. If the 4 ohms impedance is some nominal impedance given by the manufacturer then who knows?

Large phase angles will not lower the minimum impedance because this is set by the impedance seen at a zero phase angle. Any phase angle over zero degrees increases the magnitude of the impedance. Large phase angles, and 45 degrees is large, will increase the instantaneous power dissipation in the output stage of a typical class b (or a/b depending on how you label amplifier classes) amplifier which may lead to reliability problems. This is because such large phase angles cause the maximums of the voltage across and current through the output transistors to be more closely aligned than when driving a pure resistance, and thus the power dissipation in the output transistors to increase at some instants in time. The dissipation falls at other points in the cycle however vs. the dissipation encountered in driving a resistive load. The average power dissipation at a non-zero phase angle over a sine wave cycle will actually theoretically drop a little versus that into a purely resistive load.

3) Is the phase angle minus or plus, that is, capacitive or inductive?

A capacitive phase angle is likely to lead to more stability concerns with typical amplifiers that use feedback.
post #16755 of 17194
Quote:
Originally Posted by bigguyca View Post

I been reading this chain of posts. They are interesting. To generate some discussion I've written the following:


One of the paragraphs in this post needs some clarification by the author:

'And speakers with 4 ohm impedance and a 45 degree phase angle require 4 times the power and some serious heat sinks.
Unfortunately, all amplififiers are equally gifted at driving reactive loads.'

1) Does the author states that, "All amplifiers are equally gifted in driving reactive loads.?"

This doesn't fit with my experience with amplifiers. It may be a typo. I make a lot of those; likely some below.

2) Does the speaker in the example have a constant 45 degree phase angle with an impedance of 4 ohms at all frequencies?

That seems like a very unusual speaker. Typically the value of impedance and phase angle vary with frequency. That make calculation of the effective impedance and phase angle seen by the amplifier at any point in time, with complex music signals at different frequencies and with different phase angles, to be a harder task than with sine waves.

The minimum value of the impedance seen by the amplifier, which may not be seen depending on the design of the crossover, will be the impedance of the speaker at a zero phase angle, that is, the resistance. In this example I guess that the minimum impedance would be 2.8 ohms if the 4 ohm figure is the magnitude of the impedance at a 45 degree phase angle. Of course if 4 ohms is the minimum impedance (the pure resistance of the load) then the impedance at the 45 degree phase angle will be about 5.7 ohms. If the 4 ohms impedance is some nominal impedance given by the manufacturer then who knows?

Large phase angles will not lower the minimum impedance because this is set by the impedance seen at a zero phase angle. Any phase angle over zero degrees increases the magnitude of the impedance. Large phase angles, and 45 degrees is large, will increase the instantaneous power dissipation in the output stage of a typical class b (or a/b depending on how you label amplifier classes) amplifier which may lead to reliability problems. This is because such large phase angles cause the maximums of the voltage across and current through the output transistors to be more closely aligned than when driving a pure resistance, and thus the power dissipation in the output transistors to increase at some instants in time. The dissipation falls at other points in the cycle however vs. the dissipation encountered in driving a resistive load. The average power dissipation at a non-zero phase angle over a sine wave cycle will actually theoretically drop a little versus that into a purely resistive load.

3) Is the phase angle minus or plus, that is, capacitive or inductive?

A capacitive phase angle is likely to lead to more stability concerns with typical amplifiers that use feedback.

That was I type. I meant "not equally gifted" tongue.gif

Sometimes I think the word but it does not make it to the keyboard.

Very interesting post.

Amplifier and real world load issues are not easily factored into a amplifier power calculator.
For those interested, there are some interesting articles on phase angles and amplifier design:

http://www.audioholics.com/loudspeaker-design/understanding-impedance-electrical-phase/page-2

From this article:

http://sound.westhost.com/patd.htm
Quote:
The thing that saves some amplifiers is the power supply impedance, and careful design (hint - the cheapest alternative) ensures that there is enough power available for transients, but it will collapse sufficiently to allow for worst case conditions. This is not a good method to rely on.

Some commercial amplifiers use a tapped power transformer, and have settings for 8 and 4 ohms. The voltage is reduced for 4 ohm operation to make sure that the transistor SOA is not exceeded. Others take a more simplistic approach (many subwoofer amps fall into this category), where the transformer is simply too small for the job. If loaded heavily and driven hard, the supply voltage will collapse because of the under-rated transformer, and the amp will survive. Fortunately, music is dynamic, so the transformer will not have to suffer a sustained overload, and will usually live a long and happy life.

Difficult loads may explain some difference in how amplifiers sound.

- Rich
post #16756 of 17194
Quote:
Originally Posted by RichB View Post

...
Difficult loads may explain some difference in how amplifiers sound.

- Rich

More food for thought, and explains things as well as anything else!  

post #16757 of 17194
This is abstracted from a previous post by arnyk:

Reality is that many audiophiles are buying external amps that have less power at clipping with music than the AVR that they are hoping to "upgrade".
So what. As I showed, many AVR/Speaker/Room combinations can reach peak levels (Reference+20dB) without clipping:



If a 50 wpc amp can exceed Peak THX level with dBs to spare where is your agument now?
True for many pro sound amps, but no known AVRs. The limiters in pro audio amps are typically optional.

_______________________________________________________


Here are some alternative figures for the chart:


My speakers are 86 dB per efficient (2.83v at 1 meter) according to Stereophile (Salon2)

The speaker's impedance dips to about 3 ohms in the lower bass. That means the speakers use 2.83 squared / 3 ohms = 2.67 watts to produce 86 dB if we use the Stereophile measurement.

Finding efficiency per watt: log of 2.67 = .426 this times 10 = 4.3 dB so efficiency is 86 - 4.3 = 81.7 dB per watt


50 watts is 17 dB not 20 dB. (dBW?) I found a calculator online which looks much like the one above and got 17 dB for an answer.

To check: log 50 = 1.70 times 10 = 17 dB


I sit a 11 feet. The online calculator gave an answer of -10.5 for that distance.

As a check 11 feet is about 3.35 meters. The volume is likely assume to drop 6 dB with each doubling of distance. For a change from 1 meter to 3.35 meters, a drop of 10.5 dB seems about right. 2 meters would be -6 dB and 4 meters would be -12 dB. (10 x log(1/3.35 squared))


Let's use the 4.8 dB and 3.0 dB values from the rest of the figure.


I get the following assuming no errors until this point:

81.7 + 17 -10.5 + 4.8 + 3.0 = 96.0 dB

Other than the correction of 3 dB in the calculation of amplifier output the rather large ultimate difference in required power in watts between the two calculations is due to what seem like small differences in several variables.

To hit 105 dB peaks I would need another 9 dB of amplifier power. That takes the 50 watts to about 400 watts required at around 3 ohms.
post #16758 of 17194
Quote:
Originally Posted by arnyk View Post

Not exactly a paragon of great technical expertise or unbiased opinions. The author is for all intents and purposes that well known person "Anonymous poster hiding behind a nonsense handle"

 

Hi Arnyk.  Your post responding to me exhibited passive aggressive behaviour, and I went over what I posted to insure I wasn't guilty of some kind of personal insult, which I wasn't.    But you'll notice all I was doing was attempting to provide "food for thought".  Your responses seems to indicate you felt attacked and I was not attacking you!  Can we not exchange thoughts here without insults such as this:  " potentially technically illiterate audiophile eggspurt"?  Surely you can show a minimum of respect for people reading your posts?  Directly calling me "sadly misinformed" does not further the discussion.

 

I simply shared the idea that good amps can sound different, not that they all do, or that they have to or must.  Feel free to disagree with anything anybody says, but at least stay classy(The idea that those on forums who have a handle instead of their real name are hiding, and are not exactly a trustworthy source, ignores that fact that 95% of posters choose to not use their name for various reasons.  Many offer excellent advice and the reverse can be true, that some 'real name' posters can offer bad advice).

 

At any rate, I've seen you behave this way repeatedly and find it tiresome, so welcome to my ignore list.


Edited by audio4life - 1/4/14 at 8:53am
post #16759 of 17194
So, here is my situation. I also have very low sensitivity speakers (86db), NHT Classic Fours, 6 ohm nominal impedance. My AVR puts out 140W/channel (Denon AVRA100/4311). At reference the 140 is not enough power for these speakers. Room is not large, but heavily treated with broadband traps (the whole wall behind the speakers is treated as is the wall behind the seating area), plus tri-corners. So I calculated speakers as being 'away' from the walls due to the traps. Also, my seating position is just between 9 and 10 feet, I used 9. Putting my specs in the calculation, using an outboard amp - yes, I needed it anyway since running 11.1 and the AVR only provides 9 channels of amplification). Calculation taken from:

http://myhometheater.homestead.com/splcalculator.html







Notice that even with 300 watts of power I can only get 105 db (which is fine as that fits the THX recommendation of 85db for normal listening with 105db peaks). The Subs do hit louder (they are 94db efficient). Using the same calculator, my subs can hit 113db.

Bottom line is that in my room I do need more amplification if I want to hit reference levels. If I only used the AVR's power (and that's if it can actually provide the 140 watts since I'm using all the amps), I would only hit 101.7db, which falls short of THX requirements.

I guess that's what I get for having inefficient speakers, but I like their sound and it works well in my room/setup. I am using an outboard Emotiva amp (was great bang for the buck, especially on sale).
post #16760 of 17194
Quote:
Originally Posted by audio4life View Post

Hi Arnyk.  Your post responding to me exhibited passive aggressive behaviour, and I went over what I posted to insure I wasn't guilty of some kind of personal insult, which I wasn't.    But you'll notice all I was doing was attempting to provide "food for thought".  Your responses seems to indicate you felt attacked and I was not attacking you!  Can we not exchange thoughts here without insults such as this:  " potentially technically illiterate audiophile eggspurt"?  Surely you can show a minimum of respect for people reading your posts?

I simply shared the idea that good amps can sound different, not that they all do, or that they have to or must.  Feel free to disagree with anything anybody says, but at least stay classy(The idea that those on forums who have a handle instead of their real name are hiding, and are not exactly a trustworthy source, ignores that fact that 95% of posters choose to not use their name for various reasons.  Many offer excellent advice and the reverse can be true, that some 'real name' posters can offer bad advice).

At any rate, I've seen you behave this way repeatedly and find it tiresome, so welcome to my ignore list.

Yeah, that guy loooves to argue. Just picks apart posts trying to stir **** up. He had an exhaustive back and forth a while back with another obnoxious member in the paradigm owner's thread. Think they were both asked to leave, but know the other guy was. All that was needed was for them to agree to disagree, but that dude loves a dead horse😒
post #16761 of 17194
Quote:
Originally Posted by cavchameleon View Post

Bottom line is that in my room I do need more amplification if I want to hit reference levels. If I only used the AVR's power (and that's if it can actually provide the 140 watts since I'm using all the amps), I would only hit 101.7db, which falls short of THX requirements.
THX requirements are for products that bear their logo. They have no requirements for how loud you play movies in your home. IMHO, reference level is highly overrated as a goal. wink.gif
post #16762 of 17194
Quote:
Originally Posted by Roger Dressler View Post

THX requirements are for products that bear their logo. They have no requirements for how loud you play movies in your home. IMHO, reference level is highly overrated as a goal. wink.gif

I agree. I just turn up the volume until the dialog is where I want it and let the chips fall where they may.
For Music, mostly I listen very low, but every so often, I crank it.

I have measured peaks for 110 DB.
A great recording, a good amp, nice speakers all make it easier to turn up the volume.

- Rich
post #16763 of 17194
Quote:
Originally Posted by Roger Dressler View Post

THX requirements are for products that bear their logo. They have no requirements for how loud you play movies in your home. IMHO, reference level is highly overrated as a goal. wink.gif

I totally agree, no argument there. I don't own any equipment with the 'THX Logo". I do like to play at or near reference levels at times though, but usually listen at -10. But, when I do push the system to the limits, it's probably good to have the extra power. I sometimes play multi-channel music at loud levels which also taxes the system.
post #16764 of 17194
Quote:
Originally Posted by RichB View Post


And speakers with 4 ohm impedance and a 45 degree phase angle require 4 times the power and some serious heat sinks.

I'd like to see that explained more fully. There are three questions about the claims above that seem obvious to me:

(1) Are there any significant numbers of mainstream speakers with 4 ohm impedance and a 45 degree phase angle?

(2) Are there any significant numbers of mainstream amplfiiers that misbehave with 4 ohm impedance and a 45 degree phase angle or whatever tought loads that there are?

(3) Where that that 4x number come from?
Quote:
Unfortunately, all amplifiers are not equally gifted at driving reactive loads.

I'm willing to stipulate that every amplifier is different from its brothers in this regard. But that's an artificial test - the relevant issue relates to whether or not amps that are inadequate in this regard are common. Every rock on the beach is different, but nobody seems to worry about that, because the differences are generally insignificant.
Quote:
I do not feel comfortable with zero data insisting that those who purchased these affordable amps and experienced a benefit are deluded.

I don't see any evidence that finding and reviewing that data was any kind of a priority.
Quote:
I think you are confusing me with someone interested in an argument. wink.gif

Oh, that looks to me like hit-and-run conferencing which is not conferencing at all, It's dive bombing. The strategy is to make a number of exceptional claims and then run away before making good on them. :-(
post #16765 of 17194
Quote:
Originally Posted by audio4life View Post

Quote:
Originally Posted by arnyk View Post

Not exactly a paragon of great technical expertise or unbiased opinions. The author is for all intents and purposes that well known person "Anonymous poster hiding behind a nonsense handle"

Hi Arnyk.  Your post responding to me exhibited passive aggressive behaviour, and I went over what I posted to insure I wasn't guilty of some kind of personal insult, which I wasn't.

Please interpret my post as commenting on your post, not you. Actually it wasn't even about your post but rather about a reference that your post contained.
post #16766 of 17194
Quote:
Originally Posted by cavchameleon View Post


I totally agree, no argument there. I don't own any equipment with the 'THX Logo". I do like to play at or near reference levels at times though, but usually listen at -10. But, when I do push the system to the limits, it's probably good to have the extra power. I sometimes play multi-channel music at loud levels which also taxes the system.

Yep, I've got THX and none THX gear, both play at insanely loud levels!

post #16767 of 17194
Quote:
Originally Posted by arnyk View Post

I'd like to see that explained more fully. There are three questions about the claims above that seem obvious to me:

(1) Are there any significant numbers of mainstream speakers with 4 ohm impedance and a 45 degree phase angle?

Yes. You have to look at a speakers impedance curve and phase angle across the frequency range.
Quote:
Originally Posted by arnyk View Post

(2) Are there any significant numbers of mainstream amplfiiers that misbehave with 4 ohm impedance and a 45 degree phase angle or whatever tought loads that there are?

1206 smile.gif Prove me wrong. Where is your evidence wink.gif
Quote:
Originally Posted by arnyk View Post

(3) Where that that 4x number come from?

8 ohms to 4 ohms doubles the power required by the speaker. 45 degree phase angle results in 50% of the power disapated by the transistors.

http://www.audioholics.com/loudspeaker-design/understanding-impedance-electrical-phase/page-2
Quote:
Originally Posted by arnyk View Post

I'm willing to stipulate that every amplifier is different from its brothers in this regard. But that's an artificial test - the relevant issue relates to whether or not amps that are inadequate in this regard are common. Every rock on the beach is different, but nobody seems to worry about that, because the differences are generally insignificant.

Except in Florida, where the difference can destory your house and occassionally kill you.
Quote:
Originally Posted by arnyk View Post

I don't see any evidence that finding and reviewing that data was any kind of a priority.
Oh, that looks to me like hit-and-run conferencing which is not conferencing at all, It's dive bombing. The strategy is to make a number of exceptional claims and then run away before making good on them. :-(

I pointed you to some significant work on the nature of clipping and the resulting compression.
I cannot make you understand it, that is up to you.

Try as I might I do not get an honest respectful engagement.
You demand data an provide very little. A simple SPL calculator is insufficient data.
You snipe, dodge, and change the subject. It is pointless.

However, I hope that folks who want their speakers to perform up to their capabilities try to find some measurements of their true impedance and phase response and take that into account.

- Rich
Edited by RichB - 1/4/14 at 8:34am
post #16768 of 17194
Quote:
Originally Posted by RichB View Post

Quote:
Originally Posted by arnyk View Post

I'd like to see that explained more fully. There are three questions about the claims above that seem obvious to me:

(1) Are there any significant numbers of mainstream speakers with 4 ohm impedance and a 45 degree phase angle?

Yes. You have to look at a speakers impedance curve and phase angle across the frequency range.

The apparent suggestiion that I've never done such a thing is overlooked. ;-)

OK, lets do that::



This is a speaker that has been pointed out as being potentially problematical, but it fails to support the claim.



This is another speaker that has been pointed out as being potentially problematical, but it fails to support the claim.

A comment about the physics of the situation. When a speaker's impedance curve is minimum, the minimum impedance value is usually set by the DC resistance of the voice coil. But the DC resistance being a DC resistance is low on reactance so the phase angle is rapidly decreasing around this point.
post #16769 of 17194
Quote:
Originally Posted by arnyk View Post

The apparent suggestiion that I've never done such a thing is overlooked. ;-)

OK, lets do that::



This is a speaker that has been pointed out as being potentially problematical, but it fails to support the claim.



This is another speaker that has been pointed out as being potentially problematical, but it fails to support the claim.

A comment about the physics of the situation. When a speaker's impedance curve is minimum, the minimum impedance value is usually set by the DC resistance of the voice coil. But the DC resistance being a DC resistance is low on reactance so the phase angle is rapidly decreasing around this point.

When sizing an amp you provided a simple calculator and what is common may not be applicable to an individual's system.
The fact that other people systems and habits do not require an amp is insufficient and may be misleading.

Here is the Stereophile review of Thiel 3.7 speakers with a 90 DB efficiency specification.

http://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements



Quote:
The Thiel CS3.7's voltage sensitivity is specified as 90dB/2.83V/m. My B-weighted estimate on its tweeter axis, assessed with DRA Labs' MLSSA system, was slightly above that figure, at 90.7dB(B)/2.83V/m. This may well have been affected by the Thiel's frequency response (see below). The sensitivity is usefully higher than average, which is a good thing considering that the CS3.7's impedance remains between 2 and 3 ohms over much of the audioband (fig.1), and that there is a demanding combination of 3.8 ohms and –40° capacitive phase angle at 60Hz. Thiel specifies the impedance being nominally 4 ohms, with a minimum of 2.8 ohms. I actually found the minimum impedance to be 2.4 ohms at 125Hz. The difference between 2.8 and 2.4 ohms is academic, either mandating use of an amplifier that has no problem delivering high currents.

AVR's for example, do have difficulties delivering high currents.
External amps like many of those sold by Emotiva, have high current capability.

- Rich
post #16770 of 17194
Quote:
Originally Posted by RichB View Post


External amps like many of those sold by Emotiva, have high current capability.

- Rich

But as long as the current delivery capability of the AVR is not exceeded (It rarely is in typical home theaters) it simply isn't an issue.
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