Re: [Jack-Devel] Network Audio Transmission - Quality

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DateWed, 26 Jun 2013 05:36:54 +0100
From John Emmas <[hidden] at tiscali dot co dot uk>
Tojack-devel devel <[hidden] at lists dot jackaudio dot org>
In-Reply-ToJohn Rigg Re: [Jack-Devel] Network Audio Transmission - Quality
Follow-UpJohn Emmas Re: [Jack-Devel] Network Audio Transmission - Quality
On 25 Jun 2013, at 20:51, John Rigg wrote:

> On Tue, Jun 25, 2013 at 02:59:10PM +0100, John Emmas wrote:
>> Many years ago when I worked on AMS Neve's AudioFile DAW, our R&D guys  
>> came up with a new design to improve the phase response of its  
>> brick-wall filters, after countless complaints from BBC sound mixers.   
>> Subtleties in phase are notoriously difficult to detect and the guys  
>> were pretty confident that no-one would be able to hear the difference,  
>> even though the phase response was measurably more linear - but I could  
>> hear it.  In testing, I could tell with 100% reliability whether the old  
>> filter or the new filter was being used.  The tests were (literally)  
>> double-blind in the sense that I was forced to wear a blindfold AND to  
>> wear headphones, so that I couldn't be influenced by knowing which  
>> system was playing - nor by the direction or acoustic characteristics of  
>> the sound coming from different loudspeakers.  What's interesting is  
>> that out of an R&D dept of over 40 people, I was the only one who could  
>> hear the difference!
> 
> And it was quite likely a difference in the level of some side effect like
> pre-echo that you could hear, rather than the difference in phase response
> itself. That's what makes it so hard to convince those that don't hear the
> problem. The theory says something is inaudible, but they aren't looking
> at what else is going on.
> 

Exactly.  Too many people believe that if the frequency response is adequate to cover the range of human hearing and the dynamic range is similarly adequate, that's enough - whereas in fact, things can be audible without them being related to either of those things.  In this particular case the new filters gave a much more "defined" stereo image, instead of the slightly "muddy" image produced by our original filters.  I found it so easy to detect that I was genuinely surprised at how few others could hear it.

John
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