Film-Tech Forum ARCHIVE: CP-50 VS. Home Theatre Receiver with Dolby Pro Logic decoder + Preamp

This is topic CP-50 VS. Home Theatre Receiver with Dolby Pro Logic decoder + Preamp in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=007782

Posted by Marin Zorica (Member # 1716) on 01-27-2006, 04:21 PM:

I was considering to base sound system for on low budget theatre around some receiver who has Dolby Pro Logic Decoder inside, for pre amp i would use mine own pre amp with input for sound heads from both projector, HF setting, Gain setting..and after Pro Logic Decoder i would use 32Band EQ's for each channel and then power amps for each channel.

Considering that sound from pre amp is very good and level is OK can i get better decoding than with CP-50? Because i saw on CP-500 signal flow chart that analog Dolby SR is decoded by Pro Logic Decoder?

Also I'm considering to put Dolby SRA5 SR Decoder between mine pre amp output and Decoder input to get Dolby SR noise reduction, but this is only option because is hard to find SRA5.

Posted by Demetris Thoupis (Member # 833) on 01-28-2006, 06:01 AM:

I'll recon that the cost to get a Home Theater Amplifier and 5 32band eq's will be the same that getting a new CP45!!! or even a Smart Dev or a DTS or a USL Processor. Since you will be using power amps to power all speakers. Have in mind that you will need a phono to line pre-amp/mixer with Hi-Mid-Low eq on either channel to be able to correctly trim the HF level input from your projectors' sollar cell or reverse scan reader. Also grounding is very important since 99% you will have buzzing unless you use a common ground for all equipment and maybe even the sound reader (if it is a reverse scan reader). You will need to ground the mixer/pre-amp VERY IMPORTANT. I believe it does not worth the hustle if you will use external power amps and external eqs. If you want to save costs though I would reccomend going with a YAMAHA RXV-1600 or 2600 which have 9 band eq built in for each channel (It's not 32 but still is good enough if saving cost) and therefore eliminate the need for external eqs. Also how many speakers will you be driving? The above mentioned Yamaha are quite powerfull for a small theater using 4-6 surrounds.
D

Posted by Marin Zorica (Member # 1716) on 01-28-2006, 11:03 AM:

Today i calculate price of mine system, and including all taxes i must pay $5300 for all equipment (including pre amp, receiver/processor, EQ's, power amps's, cables, connectors, speakers..) and CP45 is $5400 including all taxes i must pay to get it, don't mention that i must buy all other things....

And i making mine own preamplifier for cells which has got:

balanced input for stereo cell's from two projectors,
GAIN and HF controls
automatic changeover between projectors and auxiliary inputs, and aditional bass-mid-high EQ.

so after this pre amp i connecting pro logic processor, also i think to connect Dolby SRA 5 to get SR noise reduction.

Posted by Greg Mueller (Member # 17) on 01-28-2006, 11:15 AM:

I did a similar thing with my first setup, except I used a Dolby A301 unit from a recording studio. It worked! I used an NEC Dolby Pro Logic decoder which had a remote control. I could sit in the audience and change balance etc. The only problem I never addressed well was the equalizers, (I used stereo units) but today they have a bunch of them that would probably work to give you the 1/3 octave adjustments you need.

All things considered, I'd go with a Dolby CP unit of somekind. But it was fun getting it all to work

Posted by Mark Gulbrandsen (Member # 72) on 01-28-2006, 11:23 AM:

There is a theatre in Heber, Utah that used an A-301 up till just a few years ago. I think the place is closed now and obviously these owners coulda cared less about playing proper sound formats. The system in there was originally installed by Jim Fosgate of FOsgate Audio fame who lives in that part of Utah. I believe that it was Peter Scheiber and Jim Fosgate that actually invented the Surround Sound encode-decode process and it may even be that Dolby and USL still pay these guys royalties on the patents. Being clear it was Jack Cashin that invented and added to that system the idea and technology of stering audio channels to eliminate bleed thorough between channels.

Mark

Posted by Greg Mueller (Member # 17) on 01-28-2006, 12:22 PM:

I had forgotten all about Fosgate. Boy that brings back some memories

Posted by Christos Mitsakis (Member # 143) on 01-28-2006, 12:24 PM:

Marin,
It can be done, considering some factors:
1) External noise. Such a set up, even without NR, or even in stereo only, used to be the "norm" (hopefully now is in demise)for summer open air theatres where audience is subject not only to movie sound, but of that of the external environment (nearby traffic, music from adjacent taverns etc.) In these cinemas people ar interested (or used to be) in the whole experience of watching a movie under the stars with the evening "aroma" and light food and drink. Sound quality (except for extreme bad sounding situations) was not a problem. Worth to note that at late hours fader stil is turned down at heavy inhabited areas.
2) If cost is indeed an issue, and you are using 60 year or so projection equipment. (In this case it is advisable to abandon busines)
3)If you are trying to built a personal screening room.

In any case a cinema processor is still preferable. Using CP50 though, cat 150 is an issue. Recent home decoders heve better steering then the older Cat150 (B-C) cards. Pro logic II preferably. Slit loss Eq also is better in a dedicated cell preamp than "fakeing" it with a console or mic preamp.

Christos.

Posted by Marin Zorica (Member # 1716) on 01-28-2006, 04:14 PM:

In setup with mine own pre amps i got sound to noise ratio about of 60 dB when 0% modulated film is played without any kind of noise reduction. Also i got reader flat up to 14 KHz with slit loss eq..... and i think this pre amp of mine is good.

Also i think that pro logic decoder are better than cat 150's in CP-50.

A Dolby Model 363 has A/SR system and is also good and is may bee easily to find that SRA5.

But i think this version with Dolby SR attached to system (SRA5 or Model 363) is pretty good and i think also including some good pro logic processor, 32 band EQ's you won't get much better from CP45 than this system?

Posted by Greg Mueller (Member # 17) on 01-28-2006, 05:01 PM:

I don't think I would use a CP45. They are pretty limited. (EQ and such)

The thing about a CP system is it's all nice and compact and has everything you need. All the junk I had plugged together took up a ton of space. I think the 301 unit was about 12 or 15" tall.
Wasn't the 363 just a single channel version of the 301? Or am I thinking of something else?

Posted by Marin Zorica (Member # 1716) on 01-28-2006, 11:37 PM:

No 363 is two channel unit and 361 is single channel unit. Both are having Dolby SR or A type noise reduction. Also Both are using Cat. 300 modules.

Is A301 unit is Dolby A noise reduction system or what?

Posted by Greg Mueller (Member # 17) on 01-29-2006, 12:38 AM:

The A301 unit is a 2 channel Dolby A processor used for recording and play back. I got mine from a New York recording studio. Probably some really famous folks recorded something through it. At least that's what I'd like to believe

Posted by Paul Trimboli (Member # 1509) on 01-29-2006, 01:36 AM:

Hi Marin

I have worked in a cinema that used a home theater processor and it sounded very good, the surrounds had a much nicer sound then the other auditorium that used a CP 50. The only problem was it had no NR and on a few prints background noise was apparent. Have you though of just using an LM1894 Dynamic Noise Reduction IC which are made by National, they only need a few external components and the one IC does both left and right. I have never used one so I can't coment on how well they will work with film sound.

Posted by Gordon McLeod (Member # 33) on 01-29-2006, 06:08 AM:

the one week point is that the consumer prologic usually do not have a sufficient delay line

Posted by Paul Trimboli (Member # 1509) on 01-29-2006, 06:38 AM:

Good point Gordon, forgot about that. The Yamaha processor I used allowed for a good time delay, can't remember what nor can I remember what model it was. You could of course add an extra delay cct for the surround channel..... after all this effort just go and buy a second hand processor. I kept looking and finally found one that was cheap and had all the features I needed. Its an Assosiated Sound processor made here in Australia.

Posted by Marin Zorica (Member # 1716) on 01-29-2006, 07:33 AM:

quote:
Have you though of just using an LM 1894 Dynamic Noise Reduction IC which are made by National

Yes i worked with this but isn't much improving, also has some degrading to sound, is used in Smart processors for mono format.

quote:
the one week point is that the consumer pro logic usually do not have a sufficient delay line

Yes i think on this also, and Behringer DSP8024 32 band digital graphic eqlaizer has delay option, so you can set delay! So i will use this one for surround speakers eq.

quote: Paul Trimboli
after all this effort just go and buy a second hand processor

NO!!, when i calculate price of whole system is $100 than CP45 here!!!!!!

For front system i will use Wharfedale LX-15 spekers with LX-15B subwoofer.

Posted by Mark Gulbrandsen (Member # 72) on 01-29-2006, 08:29 AM:

quote: Gordon McLeod
the one week point is that the consumer prologic usually do not have a sufficient delay line

There are a number of home decoders that actually give pretty long delay time if needed. The main thing to condsider when stating that is that most "home setups" don't require long delays like we use in some cinema apps.

Mark