DAT-heads Digest #532

Contents:
  XM radio - how does it compare to FM? ("Kevin Kachel")
  Re: XM radio - how does it compare to FM? (Gary Gilliland)
  FT: U2 - Vienna 2 july 2005 (dpa4061 + M1 source) (Luigi Bagatella)


From: "Kevin Kachel" <crystalhaze@hotmail.com>
Subject: XM radio - how does it compare to FM?
Date: Sun, 03 Jul 2005 21:27:00 -0400

"There are already various tapes of XM's Live 8 broadcasts circulating on
the torrent sites.
I'm curious to know the opinion of US tapers about the quality of XM -
would a pure digital capture (if that's possible) of XM be considered a
better or worse source than a very good FM recording?"



There is nothing good about the quality of XM "digital" radio.  It is 
popular because of its convenience and diversity.  If you were to record XM 
digitally, you would not have what was present on the original cd because XM 
uses compression before it's transmitted.

Yes it is digital, but it is not lossless.  kind of analogous to mp3.  FM is 
also lossy, but if you are recording from a high quality station that uses 
little compression and actually cares about quality, an FM recording should 
be better than XM.

Kevin





From: Gary Gilliland <garyg@use-email.net>
Subject: Re: XM radio - how does it compare to FM?
Date: Mon, 4 Jul 2005 04:25:51 +0000 (GMT)

Dave wrote:

> I'm curious to know the opinion of US tapers about the quality of XM -
> would a pure digital capture (if that's possible) of XM be considered a
> better or worse source than a very good FM recording?

  It is pretty much impossible to compare XM (in the abstract) with
anything else as it utilizes proprietary variable bit rates which are
subject to channel-to-channel change without notice (except encoded to the
receivers) and notice without change (as found on some blogs).  Quality
seems to vary not only from channel-to-channel but also from hour-to-hour
and, perhaps, even from selection-to-selection.  Following the lead of the
closed-source vendor from Redmond WA, XM has made no announcement AFAIK
about bit rate(s), frequency response(s), dynamic range(s), harmonic
distortion(s), IM distortion(s), channel separation(s), S/N ratio(s) or
any other parameter one would normally expect to be able to compare from
source to source.

  XM receivers seem all to utilize the same (XM-proprietary) chipset, at
least as far as converting the XM to PCM (or something very like PCM).
The Polk XM receiver has S/P-DIF outputs (both RCA/Cinch & TOSLINK), so a
"pure digital capture" (of sorts) is possible, but all the smoke and
mirrors associated with XM's proprietary codec have already worked their
magic (mudgic?) on the original audio, albeit in the digital domain.

  My listening tests have been quite limited, but I have yet to hear
anything I identify as "FM quality," by which I mean what one would expect
to hear on a monitor-grade receiver with a good signal from an FCC-
licensed FM station passing its proof-of-performance measurements, playing
listening material directly from a CD to the transmitter.  (This may only
happen at about 3:00 to 4:00 AM of a Sunday morning, for about five
minutes, once a year.)

  It has been said that XM Channel 27 "Cinemagic" has a high-quality
program, but it seems no better to me than was common in motion picture
theatres after Dolby but before THX.  XM Channel 24 "Sunny" sounds like
elevator music (content) and about the quality that we used to broadcast
on a 67kHz subcarrier from huge 1/4" tape reels running at 3-3/4 ips.

  What is done today in broadcast (open air, cable, and direct-satellite)
is not pretty.  What is done in sound reinforcement is no prettier.  So my
bottom line, FWIW, is:  "You pays your money and you takes your chances."
An A/B, or preferably an A/B/C comparison (with C being a good live
recording bypassing all the sound reinforcement and post-production
gimmicks), would be very interesting, but likely of limited predictive
value for other events.

  Hope this helps.

Gary



From: Luigi Bagatella <luigi.bagatella@tin.it>
Subject: FT: U2 - Vienna 2 july 2005 (dpa4061 + M1 source)
Reply-To: luigi.bagatella@tin.it
Date: Mon, 04 Jul 2005 16:39:49 +0200

I taped U2 last saturday in Vienna, Austria:
Dpa4061s + Mps6030 + M1 (48khz, 135')
Excellent sound, right in front of the main left stack.
Looking for any other U2 show, except Popmart and Elevation tour.
Now I can do dat clones.
Tapers only, please.

ciao
Luigi


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