Film-Tech Forum ARCHIVE: Help with Learning A & B Chains

This is topic Help with Learning A & B Chains in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Jeremy Weigel (Member # 4208) on 03-25-2007, 11:25 PM:

Alright guys, after many years of doing mostly mechanical work on our projectors, I have decided to finally delve into the sound system side of things. I believe that I have a basic understanding, but of course have a few questions.

To start here is a list of the current processors I have:

3- CP-65's w/DA-20's
1- Kintek 700 Series (I know, I know, but it is still go'n strong) w/SDDS DFP-2000
SDDS DFP-3000
1- CP-500
1- DTS 6AD
2- CP-65's w/SDDS DFP-2000
All exciters have been converted to BACP visible red LED's.

Test equipment that I have:

Goldline DSP30 RTA
EPRAD SA-150 Solar Cell Alignment Indicator
Component Engineering SG-1 Generator
TENMA O-scope
MMP-10 Multiplexor (already calibrated to the original mic of the DSP30)
All Test Films

The only piece of test equipment that I don't have is the Dolby Cat. 67 extender. I have been informed that Dolby no longer makes the Cat. 67 extender so does anybody know of an aftermarket version availble? I checked on the Component Engineering site and they don't.

So far I have experimented with doing both A & B chains, but I am not 100% sure that I was doing things correctly. I am pretty confident that I should be using C weighting & slow decay with the scale set to 3db on the RTA when doing B-chains.

1) What specific settings (Horizontal/Vertical/Trigger) should I be using on the O-scope for the A-chains? So far I just find settings that give me a usable/visible image on the screen .

2) When using the RTA during B-chains should I initially use the auto leveling for getting a quick reference level after I already set the preliminary SPL to 80db to begin making any frequency adjustments?

Well I think I'll stop there for the moment. I'm sure that I will have many more questions as I get deeper in to this endeavor.

As a side note, I have already gone through all speakers to check for proper phase and I must say that I found quite a few of the surrounds out of phase with each other.

Posted by Frank Dubrois (Member # 3042) on 03-26-2007, 01:50 AM:

Doesn't the manual for each specific processor give you instructions on setup proceedure? The CP-500 manual I know does, as do some others.

Posted by Jeremy Weigel (Member # 4208) on 03-26-2007, 01:59 AM:

They do give step by step procedure, but they leave out small details like the settings on the O-scope. I believe the authors of these manuals made an assumption that there would be a certain level of existing knowledge and training.

Posted by Monte L Fullmer (Member # 2797) on 03-26-2007, 02:47 AM:

Yes, there are so many makes of O'scopes that no set instruction can be written on specifics in doing A/B chain alignments by each processor manufacturer..just general stuff, like setting the unit on dual trace option, switching to X-Y settings to check phasing on the camera when running the 1kz mono loop, and the general setups of the RTA in parallel with the O'scope when connecting up to the processor for B chain testing (course, this is just the optical end of things..).

Got an SPL meter as well..one of the most handiest tools in your tekkie toolbag to have..

Posted by Alban Birch (Member # 4121) on 03-26-2007, 09:38 AM:

There's a little Trick to make EQing on a CP55/65 without the Extender Card.
Remove all the 64s, open them up and then just put them in the Left channel-slot one at a time. Swap cabling on the Amps as you do EQing on the other channels. I hope you understood my bad explanation.

Posted by Louis Bornwasser (Member # 3063) on 03-26-2007, 11:54 AM:

Good trick! I use the right channel location with L & C out. More room this way. Louis

Posted by Mark Gulbrandsen (Member # 72) on 03-26-2007, 01:08 PM:

Sorry to post negative but I wouldn't trust the Gold Line no matter what!

Mark

Posted by Jeremy Weigel (Member # 4208) on 03-26-2007, 01:11 PM:

I will have to give that try for sure.

Posted by Gordon McLeod (Member # 33) on 03-26-2007, 01:53 PM:

I have found the dsp30 to be a very good and accurate analyzer but a little funky to get used to

Posted by Frank Dubrois (Member # 3042) on 03-26-2007, 02:50 PM:

quote: Jeremy Weigel
They do give step by step procedure, but they leave out small details like the settings on the O-scope. I believe the authors of these manuals made an assumption that there would be a certain level of existing knowledge and training.

This is so true. One comprehensive explanation would help a great deal. Otherwise, it seems that these proceedures can only be taught by doing...which is actually the best and easiest way.

Posted by Monte L Fullmer (Member # 2797) on 03-26-2007, 11:41 PM:

..as noticed above, there are no two tekkies alike - each has their own way of perfecting sound reproduction. Thus, if such a organized layout on how to align such devices were in print, each tekkie would tear that procedure apart and make it their own and say 'it sounds good'.

Also, since there are so many different shapes and layout of houses where one method would work for that one house, but would make the sound reproduction horrible for the other. This would be the task of that certain tekkie to get the numbers to add up to zero at the end and balance out when facing all of this variety - from home theatres, drive-ins, to huge 3000 seat houses.

(can you imagine what processes has to be accomplished to tune in the Radio City Music Hall house, or any of those leviathan behemoth palaces of yore that NYC used to have?)

Posted by Richard May (Member # 2627) on 03-28-2007, 07:51 AM:

I have also found the goldline DSP30 to be accurate. I have used them up against many peoples analysers and found the same results. And yes, it does take a bit getting used to.

Posted by Jeremy Weigel (Member # 4208) on 03-28-2007, 08:05 PM:

Anybody ever use the Eprad Solar Cell Alignment? The one I have is actually a piece of equipment that was left behind when Regal closed this theatre back in 2001. I'm just curious.

Posted by Jeremy Weigel (Member # 4208) on 03-29-2007, 09:58 PM:

I am in need of a manual for the Kintek KT-700 processor. I checked the manuals section, but no luck. Has anybody on here used this processor in the past? Or perhaps still using one and be willing to fax or e-mail me a copy of the manual? One of the previous GM's threw out all the equipment manuals several years ago, so I am now in need of one. Any help would be much appreciated.

Posted by Jeremy Weigel (Member # 4208) on 04-04-2007, 04:15 AM:

I need some help with setting the sub EQ on the DFP-3000. The directions in the manual are not adequate in that it does not provide step by step detail. It does not explain why there is "Band 1" and "Band 2" how to use the low pass, frequency, Q, and gain controls. I assume that the frequency and Q controls are the same as for Dolby, but what of the gain and low pass controls? Do one of these correlate to the CUT control on a Dolby? [Confused]

And what's up with the band 1 and band 2? [Confused]

Any help will be much appreciated. [Big Grin]