Audio, hi-fi and car audio - If the cap fits

In article , Rob
wrote:
Jim Lesurf wrote:

Having worked in the 'ed biz' for many years, I share your concerns.

HFW has to be most poorly edited and written 'mainstream' magazine I
have come across. It is atrocious. And that's before I get to the
content ;-).

My own command of English is (alas) poor, so I tend to not be aware of that
side of HFW. However, see below... :-)

However for the same reasons I have my worries about what I have
started to think might be called "faith based engineering".

I am worried that there is a decline in the UK in the number of people
who have a genuine interest and understanding of both engineering and
physical science.

I think that's a shame - I've just read that a major university physics
department has closed down.

A number have done so in recent years. Others have done so in all but name
by 'combining' with other depts, etc. The difficulties are a fall in the
number of applicants, and being expected to provide lab-based science on a
capitation that makes this impossible unless you swipe funds from research
or other areas. Thus universities find they have to 'subsidise' physics
teaching from other areas. (The same is true for some other topics, of
course.)

Alas, my impression is that although audio can serve as an
excellent route for getting people into understanding these areas, it
often fails to do so. People become interested, but sometimes seem to
treat audio engineering as almost a branch of 'magic'. :-/

I'm not sure of your angle here. Audio engineering 'advances' appear to
me to be along the lines of digital amps, compression, multi-channel,
video enhanced, portability - I'd imagine little of the innovation is UK
based, but this may have as much to do with application opportunities
as having and nurturing the idea. Is this what you mean by 'faith based
engineering'?

Since you mentioned HFW I'll give an example from there.

If you've read HFW often enough, over a long enough period, you will find
that they sometimes make comments to the effect that, "As
the signal level is reduced below -60dBFS on CD the distortion level
rises." The implication (sometimes stated) is that this is an inherent
limit of CD-A.

The above statement is either misleading or incorrect. It seems to stem
from two flaws in the understanding/practice of NK and others at HFW. (And
at times elsewhere.)

1) A failure to understand and apply noise or dither prior to sampling.
This can be shown by reference to the standard texts, etc, on this matter.

2) A persistent tendency even when analysing dithered signals to assume
that the fraction of the power from the noise floor that falls in the
analysis 'bins' at harmonics of the test signal represents 'distortion'.
They tend to take 32k FFTs and assume that the noise is distortion. It
isn't. If you extend to longer sample lengths the level falls as you can
expect for random noise.

This has been pointed out to them by more than one person (including
myself) on more than one occasion. But they ignore this, I'm afraid.

FWIW I put up some webpages on this a while ago, and I'm hoping that a
forthcoming HFN article will also discuss this in passing.

Other statements like those attributed to various 'gurus' also appear at
times which are either misleading or nonsense, and can be shown to be so in
the same ways as above. The problem here is not that I disagree with them,
but that statements appear which cause engineers and academics who do
understand information theory, etc, to fall about laughing or dismiss audio
as a bunch of nutcases, and/or which can be shown to false by simple
measurements.

I can quite understand why readers of the magazines would not know why
their statement is unreliable as they'd need to be familiar with the
relevant areas of information theory, etc. But I do not regard this as an
excuse for the behaviour of those at HFW or others who adopt a professional
or expert status. They should know better in my opinion. They should
certainly be able to correct their misunderstandings once they have been
brought to their attention.

Hence my point here is directed at a specific group who readers should be
able to regard as giving reliable explanations, but who do not always seem
to live up to this reasonable expectation. Nor do they show that they
can recognise and correct the situation.

If it's a reference to valves (say) - I skim your exchanges with patrick
Turner (et al) and frankly it looks like semantics - I'd guess that
you're both 'right' (as if I'd know!).

I was thinking more generally of what seems to me to be an approach which I
think I've seen in various places - most commonly as exampled above. My
recent exchanges with Patrick and Andy have - in small part - made me think
about this, but I didn't have either of them primarily in mind for all the
comments I made. FWIW I largely think the recent discussions between
Patrick and myself are likely to be quibbling about matters that may well
be quite minor, and where he may well be correct. I'm pretty sure he is an
experienced and capable engineer. However I have much larger worries about
some other people/examples - of which HFW are a classic case in my view.

I admit, though, that I do find it odd that Patrick apparently bases his
comments on fuses on not on actually making some LF high current
measurements. Thus in one respect that I feel *might* be important for that
(minor) issue I feel he may be relying upon assumptions or beliefs as
opposed to a measurement I suspect might be relevant, and that these
assumptions and the measurements he has made may be misleading him.

Hence I have a suspicion that his assumptions about the physics involved
may cause him to mistakenly assume that measurements under some conditions
(e.g. at 1kHz) allow him to deduce things about LF which might not be
correct. In that sense, I'd say his approach - if I have understood it
correctly - might be "faith based". However this is in a rather more
limited sense than the HFW example, and is the kind of potential error any
working engineer might make. He may also be correct in assuming there is no
problem. It is just that I am not sure of that for reasons I have outlined,
and would prefer measured evidence I think would be more relevant.

OTOH it may well be that I have not been able to explain my point to him
clearly, and for that reason he continues to assume his measurements at
1kHz deal with the issue. My point, though, is that the references, and my
view of the basic physics implies/shows that the measurements he has made
may not have dealt with the question.

I suppose I take a particular view of such things as I, and my old research
group, specialised in measurement systems for supply to people like the old
NPL. One thing you learn from developing kit for National Standards work
is to assume everything is out to trip up your assumptions about the
reliability of measurements and what you think they are telling you. :-)

They're just different designs of the same thing. Now, whether one is
'better' than the other is the subject of some dispute. I wish we could
all settle on preference. The point, I suupose, from a design point of
view is that one *depends* on quantitative criteria, one doesn't. Are
you saying that Sony's designs of amplifiers are better than valve amps
designed by (say) Audio Innovations? Does one rely on 'science', and one
rely on 'faith'?

I can't say as I don't know much about what Audio Innovations do, or how
the proceed.

For both design paradigms I feel that a lot of nonsense comes into the
equation, with badge engineering and needlessly esoteric bits bolted
on/in. But this isn't 'faith based engineering' - it's marketing. I
don't believe that Ken Ishiwata has 'faith' in many of the things he
does - he just panders to a market. But I wouldn't say that he's a
designer reliant on mysticism.

However if he is pandering to a market with no evidence he may be
*exploiting* the 'faith based' approach of others. That said, I can't
really say as I don't have specific info on the area you mention.

For that reason I'm afraid that I do sometimes see some of the things
people say in newgroups like this one (and in magazines, and
elsewhere) as being engineering parallels with using an 'X' due to an
inability to write out their name!

That's quite extreme! A different dialect maybe, but illiterate, not
sure.

I don't regard it as a "different dialect" for audio writers to make
statements that are formally shown incorrect by the mathematical basis of
information theory, and easily shown to be false by relevant measurements.
The texts, etc, on the HFW example have been in common use for decades.
I'm sure my undergrad course isn't the only one to use them. Yet some
authors in HFW still seem to make misleading statements. My impression
is that they start off from a standpoint of disliking CD-A and then tend
to treat this issue as 'confirmation' of their beliefs.

I would also *not* apply the above to someone like Patrick as it seems
pretty clear that he would not fit in the same category as some of those
I've seen commenting on audio in magazines, etc.

I have doubts about status of some statements like Patrick's on fuses if
they are made on the basis I have described above. But this certainly does
not mean I'd then apply the above comment about writing an 'X' in such
cases. It would be too extreme a characterisation, and quite unfair and
inappropriate.

Consider the following contrast:

Whether there *is* a practical problem in the case of Patrick's amp I
have no idea. I lack the data that the relevant measurements would
provide. As I said above, though, this was not what I had in mind when I
made my earlier comments. Nor would I wish to try and single Patrick out
for a relatively minor matter like this as my real concerns were elsewhere
with problems I regard as more serious and more pervasive. My wish in this
area is simply that he should consider the references I've mentioned and
perhaps make a LF high current measurement to check the reliability of his
assumptions in one specific case.

I'd rate this as quibbling about an almost certainly minor detail which
could be resolved by a measurement, and where the person may well be quite
correct in their conclusions in practice.

This seems quite different to me from:

The HFW type of case where - so as I can tell - some writers who present
'authoratitive' opinions and statements in magazines, etc, persistently
and systematically say things which can shown to be unsatisfactory both in
terms of basic theory and measurement, and over a period of years take no
notice of attempts to point out their misunderstanding(s). Their
'technical' statements seem to stem from a misunderstanding founded on a
prejudice and hence seem not to be amenable to evidence from either theory
or measurement.

This I'd rate as a situation where those involved persistently seem to
misunderstand on a more fundamental level and refuse to twig that they are
misleading people, depite their error having quite serious implications for
the advice they give to people.

OK, in each case you could evoke "faith based" as a description of part of
the problem, but the differences between cases are as extreme those between
a paper boat and an Aircraft Carrier! :-)

Afraid the above came out a bit rambling and repetitive as I wrote it in a
hurry. However I'll let it stand as I hope it clarifies the points and
distinctions I wish to convey!

Slainte,

Jim

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