Film-Tech Forum ARCHIVE: silabance (sp?) in Dolby A playback systems

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » silabance (sp?) in Dolby A playback systems (Page 1)

This topic comprises 2 pages: 1 2

Author

Topic: silabance (sp?) in Dolby A playback systems

Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 01-12-2002 03:23 PM

I have noticed a rather strange occurance when we run dolby "a" type films. the dialog seems to have an aweful lot of silabance or splatter on s's and other vowels. is this just the nature of the Dolby A system or is something misaligned?

Simplex 35/70, reverse scan, CP500 w/ 222SR/A card and EV stage speakers.

Josh

| IP: Logged

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 01-12-2002 06:28 PM

Check the hi freq slit loss and also the dolby level

| IP: Logged

John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 01-13-2002 12:03 AM

Could be the diaphram in a HF speaker, no? It happens only in "A"?

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 01-13-2002 12:34 AM

Dolby-A doesn't or shouldn't have any characteristic "S". The EV speaker is probably a bit twitchy on the high-end. Also, if the print was SR encoded and played in A it would be a bit spitty. This all presumes that everything is calibrated/aligned properly to begin with.

Steve

------------------
"Old projectionists never die, they just changeover!"

| IP: Logged

Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 01-13-2002 01:07 AM

we are running an old print of "Batman" 1986 or so. I only really noticed it last night when I watched the movie. put a little too much FG on thought, nice white circles around the dirt. aside from that, SR plays back nice and clear without any problem.

Josh

| IP: Logged

Ray Derrick
Master Film Handler

Posts: 310
From: Sydney, Australia
Registered: Sep 2001

posted 01-13-2002 01:57 AM

Josh

Sibilance is not characteristic of A-type NR (if the print is also A-type as you say). Do you have any spare A-Type NR cards? You may have a faulty one. If there is a fault it will usually be only in one channel which will cause the sibilance to constantly shoot across to the left or right speaker. Sit in the middle of the front row and you will easily hear this if it is happening.

------------------
Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

| IP: Logged

Craig Hanham
Film Handler

Posts: 79
From: Wellington, New Zealand
Registered: Oct 2001

posted 01-13-2002 01:50 PM

Your sibilence problem is most likely to be your EV speakers.
What model are they? What is the frequency respone like for HF (from manufacturer specs)
EV does have a bit of a rep for noisy high freq for some of their units.
If you can find time try different speakers, also look at the accoustic masking of your auditorium.

| IP: Logged

Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 01-13-2002 08:34 PM

I really doubt it is the speakers, SR and digital prints playback nicely. or could it be just that with the better bandwith of reverse scan, that would normally be covered up using a forward scan system. after all reverse scan wasnt around until the early 90's right? and like I said the print was struck in the 80's

Josh

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 01-13-2002 09:07 PM

Is it just that print? I have heard similar problems with the original BATMAN. Another thing I heard on BATMAN was an occasional crackling like it was overmodulated and possibly some application spatter (but that would seem more print related.

Steve

------------------
"Old projectionists never die, they just changeover!"

| IP: Logged

Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 01-13-2002 09:20 PM

"scrooged" also had the silibance to it. the exact processor we use is a CP500-70 meaning it has two more dolby a cards for 70MM, so in effect 6 channels of NR processing. preamps are Ultra Stereo and Teccon heads

Josh

| IP: Logged

Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 01-13-2002 11:50 PM

I have to agree with Steve Guttag.

When I watched the movie "Dazed and Confused" and that other POS you were running, I thought the sound was great! What I have heard in "Scrooged" that you speak of was something I heard being emitted from the HF drivers, but since the other movies sounded great, I just contributed it to the age of the print. It was so minor I didn't even think it was worth mentioning.

The only thing I noted was too much of a volume change when the system defaulted to SR "A", plus the dynamic range seemed to suffer a little more than what I was accustomed to hearing in other theaters equipped with reverse scan.

I think your system does need slight amount of tweeking. It might be worth the effort to call that to the attention of "TJ" the next time he is in town.

Paul

| IP: Logged

Ray Derrick
Master Film Handler

Posts: 310
From: Sydney, Australia
Registered: Sep 2001

posted 01-14-2002 01:34 AM

Sibilance is normal with human speech, varying in degree from one individual to another. But "sibilance distortion" is caused by distortion of upper mid-frequency sounds, usually around the 6kHz region. It causes a kind if slurring or spattering on "S" and "F" sounds. So Josh, are you talking about sibilance distortion or the sound just being excessively bright?

I agree with what others have said regarding EV HF systems. They have a natural (and significant) response peak at around 6kHz which is normally equalised out by the cinema technician. If the driver becomes faulty, this natural peak can turn really nasty, although as Josh says, this would normally show up on all formats.

------------------
Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

| IP: Logged

Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 01-14-2002 03:13 AM

Correct me if I am wrong, but I think the wider bandwidth the reverse scan can handle, the more it is going to "see" that a standard optical lens cannot. I would think that reverse scan would be very capable of reproducing harmonics to produce the sound Josh discribes.

Paul

| IP: Logged

Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 01-14-2002 07:42 AM

yes, that splattering is what I am talking about. it only occurs in dolby A.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 01-14-2002 09:16 AM

Also, what test film did you use to set up your "A-Chain"? Dolby's Cat. 69P (color film stock) is HF deficient and will cause one to boost the HF response too far if set up the traditional way (boost HF trim for flat response).

Steve

------------------
"Old projectionists never die, they just changeover!"

| IP: Logged

All times are Central (GMT -6:00)

This topic comprises 2 pages: 1 2

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.