Film-Tech Forum ARCHIVE: Marble Stereo Sound Processor Q

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Posted by Scott Norwood (Member # 30) on 02-16-2005, 07:29 AM:

Has anyone ever dealt with a Marble "Stereo Sound Processor"? This is a grey 1U box with a fader and switches for "film/music" and "mono/stereo". This particular unit sounds bad and doesn't output anything when switched to "mono".

A cursory look at it would indicate that there are no internal adjustments for preamp gain or EQ, but I haven't yet looked at the back of the unit (in this installation, it must be removed from the rack in order to access the back panel). I'm not sure of the vintage of this unit. This is patched into the house system at a live theatre (which sounds fine with other sources). They run film occasionally, and I've told their sound guy that I'd try to help him work on improving the film sound. It's not a physical alignment (exciter/lens/cell) issue, as that was done recently by a tech who is presumed to be competent (I don't know him).

If anyone could scan a manual for this, that would be great. (And if anyone wants to donate a CP-650, that would be better!) [Smile]

Posted by Richard Fowler (Member # 893) on 02-16-2005, 07:49 AM:

Picking my feeble memory the unit is a rebadged Smart stereo SR 135 unit. You will find the manual on the www.smartdev.com site

Posted by Gordon McLeod (Member # 33) on 02-16-2005, 08:58 AM:

It is a SR135 there is no slitloss correction circuitbut the gain pots are I believe accesed through holes in the back cover (it has been a long time) There is no house eq one used there standalone 6 channel eq box for that
It does have a very quiet time delay line though

Posted by Scott Norwood (Member # 30) on 02-16-2005, 04:19 PM:

Many thanks! I downloaded the manual and it does appear to be the correct unit.

What's the general consensus on this box? Can it be made to be reliable and sound good with proper setup, given outboard EQ and good speakers (which the venue has)? Or should they be looking at a used CP50 or something else? I assume that the budget (if there is one) is low.

Posted by Gordon McLeod (Member # 33) on 02-16-2005, 05:45 PM:

hook it up and listen
they are not a cp50 by a long shot but also some sounded suprisingly good

Posted by Scott Norwood (Member # 30) on 02-23-2005, 07:24 AM:

Due to lack of time and the fact that they're running an SR print this week, the temporary fix was to swap the Marble box out for a CP65 (on loan from me). I'm not convinced that the Marble unit was set up correctly, but the Dolby box sounds substantially better, especially with respect to dialogue intelligibility (which was always a complaint). I got to do a B-chain with an RTA (thanks, Chris!) for the first time, which was interesting. I'll replace the Marble in a couple of months and set it up according to the manual.

So what is the standard practice for a theatre without surround speakers? Should the surround information be discarded completely, or should it be mixed into the L and R channels somehow? If the latter, how would one do this with a CP65? It would be easy with a custom format on a CP500, but that's not an option here, unless someone wants to make a tax-deductable donation. [Smile]

Posted by Chris Trainor (Member # 9) on 02-23-2005, 12:00 PM:

Actually doing LCR without surround is pretty easy on a CP50 or 200 with an older Cat150 board. I don't know exactly when they dropped that ability but I know the 150E I have does not do it (if you select it the surrounds still run). I think it's Format 03.

What i'm not sure of is if the 150 just drops the surround or leaves it in L/R.

--Chris

Posted by Bruce Hansen (Member # 281) on 02-24-2005, 11:39 AM:

If I remember correctly, when a SR-135 is switched to mono, only the center channel is feed. Check the center channel amps and speakers (maybe there is no center channel, which could be why dialog sounds bad).

Posted by Chris Trainor (Member # 9) on 02-24-2005, 12:47 PM:

Bruce, the amps/speakers are all in place for LCR. When Scott put in his CP65 and we EQ'ed it everything sounded great.

The house (a performing arts theatre) has no surrounds, but has some pretty decent amps/speakers for the stage.

Personaly I'm not a fan of the old Marble/Smart stuff... they are OK for personal screening rooms but not for commercial use. I'd rather use an old Smart Mod II or Dolby CP50 over those SR135's.

--Chris

Posted by Scott Norwood (Member # 30) on 02-24-2005, 02:48 PM:

The Marble box was set up to do a straight L->L and R->R with no center. I don't have the manual here and don't remember if it was designed to do this or else perhaps the unit had been modified at some point. The center channel does not output anything in either "stereo" or "mono."

This is important because much of the material which this theatre is likely to show will be mono. I will delve into this more deeply when I reconnect the Marble unit in a couple of months.

I spoke with the theatre manager today and he commented that he was impressed with the improvements in sound quality.

Edit: Chris--that CP65 has a cat. 150E card, for whatever that is worth. I had been under the impression that format 03 (Dolby Stereo w/o surround) just didn't output the surround channel at all. Does it actually do something else with the out-of-phase information?

Posted by Gordon McLeod (Member # 33) on 02-24-2005, 03:18 PM:

In 03 the matrix should not remove the s signal from the L and R

Posted by Bruce Hansen (Member # 281) on 02-24-2005, 06:56 PM:

There is a "mono" adjustment on the back of the SR-135, could someone have turned it down?