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Conference napalm::commusic_v1

Title:* * Computer Music, MIDI, and Related Topics * *
Notice:Conference has been write-locked. Use new version.
Moderator:DYPSS1::SCHAFER
Created:Thu Feb 20 1986
Last Modified:Mon Aug 29 1994
Last Successful Update:Fri Jun 06 1997
Number of topics:2852
Total number of notes:33157

2791.0. "CD's and phasing..." by PENUTS::RHAYES (Raymond F. Hayes, Jr. DTN 275-3628) Tue Dec 17 1991 14:42

    
	Here's a question for those with some audio engineering
	knowledge.

	I've got a friend that just put out her first CD. After it was
	out for a couple months, it was realized by the AM radio station
	DJ's that when broadcast in mono, the vocals disappeared almost
	completely. This also happens if it's broadcast in stereo but
	you're listening in mono. A DJ mentioned that Columbia Records was
	bitten by this problem in early releases of Laura Nyro's work and that
	it is a phasing problem. They're trying to track it down to where the
	problem occurred; at the studio in the production of the DAT masters or
	in the production of the CD's themselves. It happens on my home stereo
	if I change to mono; the vocals just disappear almost completely. Just
	barely audible. The cassette tapes are fine but there are two DAT tapes
	one for each company.

	I'd like to understand how this occurs in the recording process.


	Thanks
    
T.RTitleUserPersonal
Name
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2791.1DECWIN::FISHERI *hate* questionnaires--WorfTue Dec 17 1991 14:5417
My guess would be that someone somewhere somehow inverted the phase of one of the
channels.  When they are combined electronically (as in mono broadcast), and if
the vocal is more-or-less in the middle (left/right-wise) then they will cancel
each other out.  If they are combined acoustically (i.e. each channel is piped to
a speaker), they will cancel out somewhat, but your ears will probably hear them
ok.  Especially if you have headphones on like the recording engineers.

It's hard to imagine that someone would make this mistake, though.  If I remember
right from my FM Radio days, patch cords are not polarized left-to-right (you can
turn one end over and invert the channels), but they are polarized +/-.  Every-
thing in a stereo shop is color coded, and stereo folks are constantly on the
lookout for this sort of thing.

I can only imagine that someone lashed up some setup for the recording/mixing
session and did it wrong (and then tore it down afterwards).

Burns
2791.2SALSA::MOELLERtake it to the bridge...HIT ME !Tue Dec 17 1991 15:0230
    You really have to try to do this, or have some mic/mixer wiring that's
    really hosed.  Normally a solo voice would be recorded on a single
    track on the multitrack machine, and then during final mix to a stereo
    master, would be mixed with the pan control straight up - an equal
    amount of that signal coming from the left and right channel.
    
    Weirdness starts when the effects get put on.  One classic way of
    getting a signal to sound bigger is to run it dry (no effects) in one
    channel, and mix a delayed version of the signal in the opposite
    channel.  If the delay time is a multiple of the frequency/cycles per
    second of the original signal, you take the chance of the signals both
    disappearing when summed together, like when they come out a single 
    speaker.  Another possibility is that the azimuth (tape-to-head
    alignment) of the multitrack machine was off enough to cause phase
    cancellation of the voice track(s).  It could be a lot of things
    including a badly-wired mixing console.
    
    In fact, this phase cancellation phenomenon is widely used as a
    shielding technique in electronics - sum two shields together where one
    is 180' out of phase with the other, and you get... no induced hum.
    
    It must be a heartbreaker for your friend.. having just put out my own
    CD I know how expensive and lengthy the process is.  I really don't
    think the fault can be that of the CD manufacturing house, rather in
    the mix to the stereo master at the studio.. so the only way to remedy
    it is to go back and remix and remaster for CD... literally doubling
    the expense of the project.  Ouch !
    
    karl in tucson (still shirtsleeve weather here!)
    karl
2791.34GL::DICKSONTue Dec 17 1991 18:093
    The mixdown engineer should get some serious heat on this.  That is
    the only stage where I can see this happening.  The victim should
    consult their lawyer.  Check fine print in the contract.
2791.4Producers get Responsibility with Authority!ROULET::RAPHAELSONWed Dec 18 1991 17:3812
    I would guess that this falls somewhere in the gray area between the
    producer's and the mixdown engineer's responsibilities.  One or both
    should listen to test mixes during mixing in mono and in stereo before
    committing them to the mix down master tape, if mono playback/listening
    is a forcasted end user application.  If this was self produced, 
    it'll probably have to be expensed as tuition in that famous school of 
    hard knocks (Whatsa Matta U).  If not there may be some recourse in a
    producer's contract, as the producer is often the overall project
    manager, and the engineer's job is often to satisfy the producer's 
    concept of the project................................Jon.............
    
    ...............................Jon........................................  
2791.5SALSA::MOELLERSax and ViolinsWed Dec 18 1991 19:547
    sounds to me that this might have been a homegrown project with no
    producer except the artist.  I think going back to the studio where the
    stereo master was made would be a first step.  It's something they
    did during mixdown or xfer to RDAT for CD (or whatever medium drove the
    CD mastering).
    
    karl
2791.6Feature or bug?AZUR::DOTTIErnesto Dotti - EIC ValbonneThu Dec 19 1991 05:4225
    Cross-posted in audio_engineering 116.0 and not much to do with this
    topic, but maybe it is something that goes with it...
    
================================================================================
Note 116.0           Question on a feature of new CD players          No replies
AZUR::DOTTI "Ernesto Dotti - EIC Valbonne"           17 lines  18-DEC-1991 11:02
--------------------------------------------------------------------------------
    I have seen the brochure of some of the latest CD players (latest
    Pioneer models, another one included in a Casio digital piano).
    
    The latest feature they claim is that they can remove the vocals/solo
    with the touch of a button and the player will just play the background
    music and rythm which is on the CD with nothing in the foreground. 
    
    How does this work? is the result any good? does this work only with
    vocals or also with instruments as well (e.g. if it works with
    saxophones, I would not mind "practicing" with the group of J. Coltrane
    or S. Getz...)? Does this work with any CD or with only "special" ones?
    
    If the result is really good, or at least acceptable, then I see
    troubles for those who produce play-a-long records (the best invention
    of the '80 for musical education).
    
    thanks, E.
    
2791.7deja vuMAST::GRUNDMANNBillThu Dec 19 1991 10:564
    This sounded really familiar... So I looked around and found that note
    2551.2 mentioned this problem. Edd Cote had the same problem with his
    bass part on a Commusic VIII submission. Was the source of that problem
    ever discovered? Perhaps that would shed light on this situation.
2791.8reinvert?MIDI::CHADChad in Munich at RTO, DTN 865 3976Thu Dec 19 1991 13:007
	If that CD player really works just play the CD
	with the button pushed in to reinvert the signal???
	and have a DAT recorder there to remaster it?

	Chad who_knows_nothing_about_this

2791.9Never neglect the low end systemBSS::STPALY::MOLLERFix it before it breaksThu Dec 19 1991 13:4727
	My studio set up includes a $22.00 cassette deck that is mono.
	when I'm done with a mix, I make mono copy - when sounds disappear,
	it's usually the result of some sterio effect (like a sterio reverb
	unit - my Microverb is a good example) that introduced a sterio
	image that cancels itself out, or phases in and out when played
	in mono. You have to realize that often things get played on
	junk systems (this especially holds true for band demo tapes), and
	your mix needs to be tested in mono somewhere along the way (as
	well as on a cheap car sterio system) to make sure that you've mixed
	for the best possible sound. Everything sounds good on my high
	end sterio monitors, I find lots of flaws on my $25.00 (each)
	sterio monitors, and I find lots of problems on my garbage monitors
	(these are Radio Shack 2 inch speakers - 2 watts each - about $1.50
	each, glued onto a piece of particle board with a 1 1/2 in hole for
	rear mounting the speakers - ie, open backs). When I listen to top
	end CD's on my garbage monitors, I can hear every instrument clearly,
	and the music still has the right feel. If I can't do the same, the
	the mix is bad (usually too muddy - ie over emphasized bass & not
	bright/punchy enough low end in the original recording). Once I get
	it to this point, then I tape a sterio cassette & play it on my
	$22.00 cassette deck - It sould still sound ok, and I shouldn't
	lose any instruments. If all is well, then I have a finished product.

	This is all very time consuming, but you need to do it, since you
	don't know who might play this, or on what kind of system. 

							Jens
2791.10MIZZOU::SHERMANECADSR::Sherman DTN 223-3326Thu Dec 19 1991 14:127
    re: -.1   Amen, brother!  The acid test for me is copying to a $.50
    cassette and playing it in my car stereo while cruising to or from
    work.  I also listen to it over earphones and over home stereo.  All of
    this is cheap equipment.  I've become accustomed to being pleasantly
    surprised when I get to finally hear it on an expensive studio system.
    
    Steve
2791.11MANTHN::EDDWe fish ewe a mare egrets mooseThu Dec 19 1991 14:269
    I did discover the cause of my lost bass. I traced it back to an
    alignment problem on the tape deck in my studio. Tapes recorded and
    played back on that deck were OK, but tapes recorded on that deck
    and moved to a second deck lost the bass when played in MONO. Had I
    simply duped the tape from the studio deck to a second the problem 
    wouldn't have surfaced on C-8. Instead, I gave Brian the ORIGINAL
    tape, recorded on the bad studio deck...
    
    Edd
2791.12Outcome...PENUTS::RHAYESRaymond F. Hayes, Jr. DTN 275-3628Mon Dec 23 1991 13:4535
    
	Thanks for all the input. Sorry I haven't had a chance to draft
	any replies but I did want everyone to know the outcome.

	We took the DAT tapes into the studio with the original engineer.
	The producer gets lots of money for his time so he reviewed the CD
	at home and faxed his comments.  It took all of about 10 minutes to
	verify that the original DAT tapes created at the studio were 180
	degrees out of phase. Both the tape and the CD DAT tapes. This didn't
	explain why the cassettes came out OK and the CD's were flawed. We
	finally figured that out. In a small note on the inside of the 
	cassette DAT, the engineer who made the cassettes in California had
	noted that he discovered that the DAT was 180 degrees out and had 
	made the necessary correction. The CD manufacturer missed it
	completely.  The CD manufacturer and the studio explained that they
	used to check for this problem but over time because no one ever
	made this particular mistake, they stopped checking. The engineer in
	the studio explained and showed us that it was one small button that 
	he probably hit with his hand sometime during production of the DATs. 
	He was pretty depressed about the whole thing.

	To their credit, they didn't hedge taking full responsibility and
	opening up their checkbook to remedy the problem and replace the
	product. They are though, not making any promises about reimbursing
	for packaging,mailing,labor, etc. Aside from the fact that the 
	product was mailed to 75+ AM radio stations, where air play could
	have discouraged potential sales. Assigning a cost to this,the
	anxiety and grief are going to probably be what brings in the 
	lawyers to negotiate a settlement if they can't agree.

	Thanks again for all the input. I helped alot.

	Ray Hayes

    
2791.13MIZZOU::SHERMANECADSR::Sherman DTN 223-3326Mon Dec 23 1991 15:304
    Oooh.  Sad, sad story.  Guess the moral is, when you go to DAT, make
    sure you test for this problem.
    
    Steve