NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/rec/audio/15549

Internet Message Format | 1992-11-22 | 2.8 KB

Path: sparky!uunet!mcsun!uknet!gdt!bsmail!smee
From: [e-mail] (Paul Smee)
Newsgroups: rec.audio
Subject: Re: Pioneer LLC CD players
Message-ID: <[e-mail]>
Date: 23 Nov 92 10:32:42 GMT
References: <[e-mail]>
Reply-To: [e-mail] (Paul Smee)
Organization: University of Bristol
Lines: 48

In article <[e-mail]> [e-mail] (Deryk Barker) writes:
>Does anyone have any experience with the new Pioneer LLC (can't recall
>what it stands for) CD players? Reviews I've seen sound encouraging.
>
>Deryk Barker, Computer Science Dept., Camosun College, Victoria B.C.

Hey, hi there Deryk, fancy seeing you here.

One of our hifi mags did a short article about it last month.
Basically, the ads are mis-leading.  It does NOT 'faithfully reproduce
the freqs above 22 KHz' -- which, Nyquist would tell us, is impossible
anyway.  What it does is use a sort of weaker filtering, so that some
of the artifacts from the sampling and reconstruction process come
through.

In essence, with 44.1 kHz sampling, when you reconstruct you get the
original frequency spectrum, plus a 'reflection' off of 44.1 kHz.
(Plus higher order ones which we'll ignore.)  E.g. if the real music
contains 5kHz, 12kHz, and 20kHz signals, then with LLC the reconstructed
stuff contains that plus 39.1kHz (44.1 - 5), 32.1kHz (44.1 - 12) and
24.1kHz (you get the idea).

There's evidence to show that some people find that this extra
high-freq stuff helps make the thing sound 'better' in some strange
way, even though it's (a) theoretically beyond the range of hearing,
and (b) not the real harmonics you'd expect with those signals.
However, some people find it sounds worse.  (And, of course, some can't
tell the difference.)

One thing the article specifically warned about, though, is that the
presence of that super-audio signal can drive some amps into heavy
intermodulation distortion -- which you might not like.  Also, some of
those 'super-audio' freqs may approach the breakup frequency of your
speakers (specially if you have metal-dome tweeters) which again can
have 'interesting' effects on the sound.  (In fact, given that you
shouldn't be able to hear these freqs, seems to me that a plausible
explanation of the alleged audio effect might be that the unhearable
stuff drives the amps and speakers into a pathological condition which
might or might not be nicer, but which is has effects down in the
hearing range.

Or, in other words, for sure you shouldn't buy one unless you've tried
it with the same amp/speakers setup you plan to listen to it with, and
have decided that you personally like it.

--
Paul Smee, Computing Service, University of Bristol, Bristol BS8 1UD, UK
 [e-mail] - ..!uunet!uknet!bsmail!p.smee - Tel [phone]