Once upon a time on usenet Jim Lesurf wrote:
In article , ~misfit~
wrote:
Once upon a time on usenet Jim Lesurf wrote:
In article , ~misfit~
wrote:
Once upon a time on usenet ~misfit~ wrote:

Interesting. I read the page and it seemed pretty clear to me. In
general I tend to think Xiph's work is recommendable.

Having read and re-read the article in question now I must say that,
despite a lot of factual information I disagree with the conclusions
he presents in the section "192kHz considered harmful".

(For the record I believe that, while we may not be able to 'hear'
frequencies above 20kHz we detect sound with more than just our
cochlea / Oragn of Conti. Also that there are detectable products
caused by intercation between high frequencies... Etc.... Too
complicated to get into here.)

Yes. The argument here is that the hearing system is inherently
nonlinear so the presence of sounds which - in isolation - would be
inaudible may alter our perception when they occur sumultaneously
with lower frequencies.

Yes. I find that very high frequencies tend to make bass (in particuler)
cleaner and better defined.

The snag being that devices like loudspeakers are also nonlinear.
Present when you reproduce the audio, but not in the original sound.

Yeah, this is why the whole field is disputed.

He offers as evidence as to why that arbitrary cut-off line should be
there a graph showing the effects of intermodulation distortion
caused by two notes at 30kHZ and 33kHz. If we take it at face value
than, sure there is IMD from the reproduction of those notes that
manifest in the audible range. However, as can be detected from his
graph they are at approximately -65"dbFS" (FFS - why not complicate
the issue?) compared to the original tones.

Again, if you examine 'high res' recordings, the amount of power above
about 30k Hz is also generally about three quarters of SFA compared
with what is below 10 kHz. So the same argument that this is too
small to matter can probably be deployed. :-)

I suspect this is why the MQA have changed tack and argue in terms of
'timing'. This lets them dodge the above awkward fact, and the way MQA
actually may alter and discard HF details.

I suspect that you are right.

I'm aware that this is a contentious issue so will leave it at that.
Suffice to say that in speakers of my own design and manufacture I
often use quasi-ribbon 'super tweeters' or tweeters capable of up to
at least 40kHz.

I tend to suspect that the main effect of 'super tweeters' is down to
them adding output at lower frequencies that then vector sums with
the main tweeter output to modulate the sounds at lower frequencies.

The 'super tweeters' that I make for my own use have Philips quasi-ribbon
drivers (aluminium 'voicecoil' printed onto Kapton film between four
neodymium bar magnets) and are run through high-pass filters of my own
devising and as such are 'inaudiable' when played on their own.

My 5.1 system uses Sony SS-K70EDs, SS-K30EDs and a SS-CNK10ED centre
speaker, the 'ED' is for 'Extended Definition'. using a 25mm carbon dome
tweeter supposedly accurate up to 40kHz. These were from a failed line (at
least economically) of speakers that Sony released to accompany their SACD
offerings. Sony make a slightly different version of them using the same
drivers but with better finish for sale in Japan where they are still very
popular.

Possibly in a way that is room dependent due to differences in
dispersion. So hearing any 'change' may be due to components that are
audible without the supertweeter or assuming we can all hear stuff
well above 20kHz.

It's hard to know exactly why they work as they do.

I did however learn a bit from the article once I got past the (to
me) confusing phrasing. Perhaps the author isn't a native English
speaker? That is an increasing occurance lately and I think that I
need to be more flexible. However 'old dog - new tricks' and all
that...

I thin Xiph is American.

Ok. I might look for more of his stuff.

Cheers,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)