Head-Fi.org › Forums › Equipment Forums › Sound Science › Testing audiophile claims and myths
New Posts  All Forums:Forum Nav:

Testing audiophile claims and myths - Page 202

post #3016 of 3264
Quote:
Originally Posted by esldude View Post
 


For the most part there is no point or need.  A DAC with flat response will accurately output any EQ changes to the signal.  A headphone amp should accurately portray those changes as well.  Now excessive EQ could overdrive the amp and cause clipping or high distortion.  It also could do that for the headphone itself.  Within reason, any EQ will get correctly transmitted out to the headphone response within the limits of the headphone.

+1. 

 

Only if it was not meant acoustical output measured with microphone/ear coupler/dummy head after the EQ has been applied - and how it compares to unequalized output. 

 

DAC alone should not have any audible deviation from flat. 

post #3017 of 3264
Quote:
Originally Posted by bigshot View Post
 

All of that has everything to do with the application of the tools and nothing to do with the tools themselves. A good engineer can easily get great sound with digital audio, equalization, etc. As the old saying goes... A bad craftsman blames his tools.

Partly agreed. Theorethically perfect equipment applied poorly will yield worse result than inferiour equipment applied excelently.

 

Then again - one can apply all the expertize in the world, if data acquisition provides only so much info, it can not record what is not provided in the first place.

post #3018 of 3264

This might be a silly question but can amplifiers affect pace, rythm and timing of music? I've heard the term PRAT being thown around on audiophile forums.

 

Is there any part of an amplifier that could possibly affect things like this, or is it totally bullcrap? My first thought is how can amplifiers change the timing and rhythm of music since it is a factor of the music, right?

post #3019 of 3264
Quote:
Originally Posted by Mezzo View Post
 

This might be a silly question but can amplifiers affect pace, rythm and timing of music? I've heard the term PRAT being thown around on audiophile forums.

 

Is there any part of an amplifier that could possibly affect things like this, or is it totally bullcrap? My first thought is how can amplifiers change the timing and rhythm of music since it is a factor of the music, right?


not satisfied with the answers on hydrogen?

post #3020 of 3264

Not really. You can inadvertently (or purposefully) affect the frequency response to roll off highs, or emphasize bass somewhat - and of course, impedance mis-matches can have all sorts of effects (flabby bass, etc.) - and harmonic distortion can seem to smooth things out by introducing artifacts... but actually change the pace, rhythm, timing? No. 

post #3021 of 3264
Quote:
Originally Posted by Mezzo View Post
 

This might be a silly question but can amplifiers affect pace, rythm and timing of music? I've heard the term PRAT being thown around on audiophile forums.

 

Is there any part of an amplifier that could possibly affect things like this, or is it totally bullcrap? My first thought is how can amplifiers change the timing and rhythm of music since it is a factor of the music, right?

In a competently designed amplifier, no. 

 

However, if frequency response is not extended enough beyond and below the officially accepted 20-20k limits,

it can have affect. More serious is defect in power supply - if it is modulated by the audio signal at ANY frequency, but particularly within 20-20k, it can have an effect on the so called PRAT. This also goes for particular points within the circuit that should be stable - not just main + - after the rectifiers and main capacitors. 

post #3022 of 3264

PRaT is complete hogwash. It's a does have a useful purpose though. It helps you sort out audiophile equipment reviewers who don't know what they're talking about.

post #3023 of 3264
Quote:
Originally Posted by bigshot View Post
 

PRaT is complete hogwash. It's a does have a useful purpose though. It helps you sort out audiophile equipment reviewers who don't know what they're talking about.


I was thinking just that, almost everytime a reviewer talks about PRAT he's in fact talking about the shape of the FR in the bass(or simply dreams the dream like they often do). often rolled off bass are called fast and controled with a great PRAT ^_^.

in a way it's true, if you don't don't hear 30 or 40hz as loud, you hear more of the faster frequencies :deadhorse:

post #3024 of 3264
Quote:
Originally Posted by analogsurviver View Post
 

In a competently designed amplifier, no. 

 

However, if frequency response is not extended enough beyond and below the officially accepted 20-20k limits,

 

I'm confused - why is it not a safer bet to have amps that cannot reproduce supersonic frequencies as you would be less likely to get IMD effects folding back into the audible range ?

 

 

it can have affect. More serious is defect in power supply - if it is modulated by the audio signal at ANY frequency, but particularly within 20-20k, it can have an effect on the so called PRAT.

 

I'm skeptical about the PRAT thing, I've yet to hear a definition that makes sense in terms of physics but I can understand why poor supplies might have an audible effect but would they not have to be really bad and would not the effects be gross such as distortion sidebands at the AC frequency points - can you expand on your answer ?

 

 

 

This also goes for particular points within the circuit that should be stable - not just main + - after the rectifiers and main capacitors. 

post #3025 of 3264
Quote:
Originally Posted by bigshot View Post

PRaT is complete hogwash. It's a does have a useful purpose though. It helps you sort out audiophile equipment reviewers who don't know what they're talking about.
PRaT was an invention of the UK Hi-Fi press in the late '70's/early '80's, when they spent their time fawning over the whole Linn/Naim mantra of "it's not the measurements stupid, they tell you nothing". A dam broke, leading to the purely anecdotal reviewing/subjective assessment bandwagon we've got.
post #3026 of 3264
Quote:
Originally Posted by nick_charles View Post
 

Well, it may well sound confusing at first - but really it isn't.  I am not fond of the term PRAT in the first place, but will offer my view on what might also be termed as PRAT.

 

Frequency response of any electronic , if not perfect ( DC to light ), is at its corners (defined as -3dB points in frequency response ) actually delayed in relation to input signal - and that delay definitely IS audible. Only the midrange is on spot regarding time or phase or whichever way one wants to describe it - at both low and high end of the response the deviations are ever greater.  No response at certain frequencies means they were delayed - forever. The narrower the response, the more in time the output deviates from the original sound wave - despite being more than satisfactory in amplitude . This effect also can be "lumped" into PRAT.

 

I agree that IM distortion can be a problem in wideband amplifiers. In competently designed amps/preamps it is NOT an issue - as a matter of fact, well designed wideband amps have usually lower IMD figures. However, higher up, usually well beyond 20 kHz, sources , be it analog or digital, can have significant spurious output;

if the high frequency part of the end transducer, be it headphone or speaker, is behaving well above 20 kHz, say at least to 40 kHz, usually there are no ill effects due to IMD.

We used to have an entire chain, from analog source to speaker, capable of essentially flat/useful response past 100 kHz. Then CD happened... - and 20 years after that, when SACD arrived, manufacturers were reinventing the wheel by boasting their amps can (again) reproduce 100 kHz. ...

 

Regarding "points" : one can measure only input and output of an amplifier ad nuseaum, it may well have superb measured values on all the standard measurements ( FR, S/N, THD, IMD ) - yet it can not sound "right" and will be sonically beaten by amps that measure worse - sometimes FAR worse. 

What is required is to go trough an entire amp and see where the "bottlenecks" are. There are, as usually, tradeoffs - be it actual design tradeoff, cost or simple decision by the manufacturer to offer different quality at different price points - despite the fact that it would cost not much more or no money to let the circuit be utilized to the full potential. Much of the Mark 1 trough Mark XY game can be "accused giulty as charged" on this count; manufacturers are usually only willing to up the ante to the approximate level of the competition, not the full potential of the circuit. Sad, but true.

post #3027 of 3264
Quote:
Originally Posted by castleofargh View Post
 


I was thinking just that, almost everytime a reviewer talks about PRAT he's in fact talking about the shape of the FR in the bass(or simply dreams the dream like they often do). often rolled off bass are called fast and controled with a great PRAT ^_^.

in a way it's true, if you don't don't hear 30 or 40hz as loud, you hear more of the faster frequencies :deadhorse:

Actually, the OPPOSITE is true. 

 

Any piece of electronics that limits low frequency response will sound LOUDER in the bass than truly well extended or ultimately DC capable equipment. This is VERY difficult to explain to an average and not-so-average listener. Significantly more than 90 % of all the audio equipment unfurtunately belongs to the limited LF response group - hence it de facto became the standard and all equipment is measured against.

Greater extension in the bass should mean louder bass - right ?

 

WRONG.

 

A truly neutral and well extended in LF electronics (say - 3 dB @ 2 Hz or lower) will have a far more precise bass - but not exaggerated in any way,. And definitely QUIETER than limited LF counterparts.  Regardless what headphone or speaker is being driven ( save those that have "no" bass to begin with ).  One could also term this as a part of the PRAT mantra.

 

The full effect is achieved with truly great bass transducers - if loudspeakers, these have to be used in a LARGE room, considerably so than the usual rooms most people use for listening; 20 Hz has an wavelenght of 17 metres, what should be 3D diagonal of the listening room - meaning that leaves most of us with headphones to explore LF.

 

One of the most revealing instruments for realism both in bass and TREBLE ( and everything in between ) is acoustic bass. Both in recording and in reproduction.

It is perhaps the best instrument to use for testing of "PRAT" - whatever one understands under this term. It will ruthlessly reveal any LF or HF limiting - and is something what redbook CD will never get right, due to the lack of the HF extension. Again, please listen to the acoustic bass live - particularly plucked strings. 

post #3028 of 3264
Quote:
Originally Posted by analogsurviver View Post
 
Quote:
Originally Posted by castleofargh View Post
 


I was thinking just that, almost everytime a reviewer talks about PRAT he's in fact talking about the shape of the FR in the bass(or simply dreams the dream like they often do). often rolled off bass are called fast and controled with a great PRAT ^_^.

in a way it's true, if you don't don't hear 30 or 40hz as loud, you hear more of the faster frequencies :deadhorse:

Actually, the OPPOSITE is true. 

 

Any piece of electronics that limits low frequency response will sound LOUDER in the bass than truly well extended or ultimately DC capable equipment. This is VERY difficult to explain to an average and not-so-average listener. Significantly more than 90 % of all the audio equipment unfurtunately belongs to the limited LF response group - hence it de facto became the standard and all equipment is measured against.

Greater extension in the bass should mean louder bass - right ?

 

WRONG.

 

A truly neutral and well extended in LF electronics (say - 3 dB @ 2 Hz or lower) will have a far more precise bass - but not exaggerated in any way,. And definitely QUIETER than limited LF counterparts.  Regardless what headphone or speaker is being driven ( save those that have "no" bass to begin with ).  One could also term this as a part of the PRAT mantra.

 

The full effect is achieved with truly great bass transducers - if loudspeakers, these have to be used in a LARGE room, considerably so than the usual rooms most people use for listening; 20 Hz has an wavelenght of 17 metres, what should be 3D diagonal of the listening room - meaning that leaves most of us with headphones to explore LF.

 

One of the most revealing instruments for realism both in bass and TREBLE ( and everything in between ) is acoustic bass. Both in recording and in reproduction.

It is perhaps the best instrument to use for testing of "PRAT" - whatever one understands under this term. It will ruthlessly reveal any LF or HF limiting - and is something what redbook CD will never get right, due to the lack of the HF extension. Again, please listen to the acoustic bass live - particularly plucked strings. 


I was talking about perceived "speed" not loudness. as more sub bass can feel like "slower" bass. and by extension some mistaking rolled off bass for great PRAT. at least that's how I understood the few reviews where it's mentioned and I was lucky to have auditioned the product.

 

about more extension in bass not sounding louder, I kind of agree. and my own theory that I'm very not sure at all about, is as follows:

-when we have several sine waves at several frequencies we kind of hear a mix of those as one tone. so with that idea extending the low frequencies would move that one perceived tone lower (if the lowest of the 3 sine moves to a lower freq, the perceived tone sounds lower).

- then I through fletcher munson in the mix and I come up with some kind of not super scientific intuition that pushing the perceived tone lower will sound quieter.

then I enforce that theory with very little confidence with music being but a lot of sine waves "et voila!"

even to me it looks like nyan cat science but I couldn't imagine better reason.

post #3029 of 3264
Quote:
Originally Posted by castleofargh View Post
 


I was talking about perceived "speed" not loudness. as more sub bass can feel like "slower" bass. and by extension some mistaking rolled off bass for great PRAT. at least that's how I understood the few reviews where it's mentioned and I was lucky to have auditioned the product.

 

about more extension in bass not sounding louder, I kind of agree. and my own theory that I'm very not sure at all about, is as follows:

-when we have several sine waves at several frequencies we kind of hear a mix of those as one tone. so with that idea extending the low frequencies would move that one perceived tone lower (if the lowest of the 3 sine moves to a lower freq, the perceived tone sounds lower).

- then I through fletcher munson in the mix and I come up with some kind of not super scientific intuition that pushing the perceived tone lower will sound quieter.

then I enforce that theory with very little confidence with music being but a lot of sine waves "et voila!"

even to me it looks like nyan cat science but I couldn't imagine better reason.

What is required for perceived speed in bass ?

 

Extension waaaay above 20 kHz - with sources and headphones/speakers that support it - a good amp should be the least of a problem.

 

I agree that rolled off bass can very easily be mistakenly perceived as having great PRAT - but now I hope the extent of mentioning PRAT is spent for some years to come - I doubt I thought or said or written it as many times as in few posts back - in my entire life. Far too loosely defined for my taste, actually mixing quite a few audible things in a single bag .

 

Why does the limited LF response sound louder than the correct one ? Simple - if one observes the square wave trough an amp on oscilloscope, it can be clearly seen that what should have an amplitude of + - so and so many volts , can have twice that on leading edge and half that on trailing edge - and typical sagging in beetween the two instead of tops being flat.. A perfect responce (DC amp ) would be +- so and so many volts, with flat tops, no sagging. An example of limited LF response can be seen from approx 16:00 in the following video:

 

 

The initial amplitude in limited LF response amp IS larger - and headphones/speakers will reproduce it and it will be ultimately perceived as louder.

 

Since louder is better ... - even if in fact is inaccurate !

post #3030 of 3264
Quote:
Originally Posted by analogsurviver View Post
 

What is required for perceived speed in bass ?

 

Extension waaaay above 20 kHz - with sources and headphones/speakers that support it - a good amp should be the least of a problem.

 

I agree that rolled off bass can very easily be mistakenly perceived as having great PRAT - but now I hope the extent of mentioning PRAT is spent for some years to come - I doubt I thought or said or written it as many times as in few posts back - in my entire life. Far too loosely defined for my taste, actually mixing quite a few audible things in a single bag .

 

Why does the limited LF response sound louder than the correct one ? Simple - if one observes the square wave trough an amp on oscilloscope, it can be clearly seen that what should have an amplitude of + - so and so many volts , can have twice that on leading edge and half that on trailing edge - and typical sagging in beetween the two instead of tops being flat.. A perfect responce (DC amp ) would be +- so and so many volts, with flat tops, no sagging. An example of limited LF response can be seen from approx 16:00 in the following video:

 

 

The initial amplitude in limited LF response amp IS larger - and headphones/speakers will reproduce it and it will be ultimately perceived as louder.

 

Since louder is better ... - even if in fact is inaccurate !


Actually the waveform you are referring to is caused by reduced low frequency content.  There is no initial LF response that is larger.  Square waves are sines with odd harmonics.  The initial edge is from higher harmonics.  So were this a low frequency part of music the amp won't respond with an initial higher level that fails to continue on.  It will simply respond at a lower level, and that is it.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Sound Science
Head-Fi.org › Forums › Equipment Forums › Sound Science › Testing audiophile claims and myths