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

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » CP50 Alignment questions (Page 1)

This topic comprises 2 pages: 1  2

Author Topic: CP50 Alignment questions Sam Hunter Jedi Master Film Handler Posts: 779 From: West Monroe, LA, USA Registered: Jan 2002 posted 03-12-2003 10:11 PM                     My CP50 project is getting down to the nitty gritty and I came across some things I am not sure of. 1st off, adjusting the equalization on the CAT64. The manual states that you turn down all CAT64 input controls to minimum. I have not found where you adjust them any more after that. Also, there are four adjustments on the front of the CAT64 marked HF, GAIN and the other set is marked INPUT, OUTPUT. I haven’t found any reference to GAIN, HF so what is it used for and should it even be touched? 2nd, I do not have a CAT85 Pink Noise card so could I use a PC based pink Noise Generator instead and just clip lead it into each input and would it need to be terminated? 3rd, I am considering purchasing a sound pressure meter from Radio shack that has an output on it that I think will serve as a MIC as well. Also, my screening room is around 20x20 so would there be any special considerations in setting the response and surround delays? Thanks!  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 03-12-2003 10:39 PM                    The Cat64 contains some vestigial circuitry that are not used in the CP50 (or any CP) inplementation. HF and Gain are part of a head EQ circuit (like the slit loss adjustment on the pre-amp card). You might be able to use PC pink noise. I don't know about termination needs. The RS SPL meter is good for setting levels but don't expect a flat response from the mic when connected to an RTA. If you are really desperate and have access to a properly tuned theatre you could take your setup there while someone runs pink noise and trace what odd graph you see displayed (knowing that it represents flat response) then go back home and try to match it. Very crude.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-12-2003 10:55 PM                     Sam, Yes, you can use the PC based PN generator as long as it is a good broadband pink noise. There are many inferior generators out there..... Mark  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 03-12-2003 10:59 PM                    Or simply download .wav file of pink noise.  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 03-12-2003 11:01 PM                     Something to consider about trying to use the mic from the Radio Shack meter with an RTA... You'd need to know if that output is before or after the built-in A-C weighting. Also, I'd think you ought to have a mic that is matched to your RTA unit.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-13-2003 08:55 AM                     Or simply download .wav file of pink noise." ____________________________________________________________ If one is doing important EQ work I would consider downloading an unknown WAV file for this use to be reckless and meaningless unless the PN is first tested for its quality. Especially from something like a heavily compressed wav file. Its doubtful that even the best WAV file decoding could properly reconstruct a really high quality PN signal which is a random signal in and of itself. It may sound like PN, but I guarantee you that its not really. Most audio PC cards are pretty lousy too. If one has to use a pre-recorded PN source at least use one from an SACD, or DVD audio disk that is capable of giving decent results. I fear that even PN from a regular CD is not even good enough. It would however be better than using a WAV file source.....see this link...... http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2515156091&category=23788 Again, like it was mentioned in another previous thread, supposed high quality PN such as everyone thought was in the Sony Processor can turn out to be not so good and you can end up with meaningless eq curves and having wasted alot of time. While many use the Cat 85 cards for Dolby EQ the PN out of the C.E. card is actually quite a bit better. Both are acceptable but I've always used the C.E. card at Dolbys reccomendation. I would definately reccomend that Sam aquire the C.E. card. Its a handy tool and he seems to want to take his hobby into the next higher realm anyway...If one has gone this far the rest of it is worth doing the right way!! Mark @ CLACO  |  IP: Logged Christopher Seo Jedi Master Film Handler Posts: 530 From: Los Angeles, CA Registered: Jun 99 posted 03-13-2003 11:05 AM                     Sam, I think the input controls on the Cat. 64s stay at minimum (with the "Head Equalizer" controls unused) and you only adjust the output controls, per section 7.2.5.e-g on page 7.12.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 03-13-2003 11:17 AM                    I wouldn't use the RS preasure meter for anything but a rough reading of the preasure levels. I couldn't find the instructions for it but if memory serves that output is for re calibration of the preasure meter. Not for sophisticated measurement of EQ cards.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 03-13-2003 02:06 PM                     THose two pots are also used in the alignement of a CP100  |  IP: Logged Fred Georges Master Film Handler Posts: 257 From: Lombard, IL, USA Registered: Jun 2000 posted 03-13-2003 03:13 PM                     Here's a link to a mod that will make the Rat Shack meter more accurate & usefull. Eric Wallin's Homepage  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-13-2003 07:30 PM                     Why not hunt around at Toronto Science and Surplus for a nice used Bruel & Kjer SPL meter like Gord and I did a few years aback.....They were only around 75 bucks if my memory serves me correctly. Mark @ CLACO  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 03-13-2003 09:59 PM                    Mark, if we're talking about an uncompressed .wav file it's going to be no different than running a software-based pink noise generator. Either is going to be delivering the same digitized PN to the soundcard's D to A circuitry and subject to the same limitations of that and the analog circuitry on the card. Such a file I downloaded sounded fine and looked fine on the RTA. I would think that ideally one would want a purely analog PN source but then again surely the current generation of digital CP's generate their PN in software too.  |  IP: Logged Sam Hunter Jedi Master Film Handler Posts: 779 From: West Monroe, LA, USA Registered: Jan 2002 posted 03-13-2003 10:44 PM                     I have seen circuits in articles showing how to make an PN generator. I will probably use the RS presure meter just for setting and comparing levels and use a good quality mic for my PC based RTA. Again, what effects or peculiarities should I expect in my 20x20 screening room? Should I make the responce brighter due to the smaller area or go by the book?  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 03-13-2003 11:40 PM                     The CP50 manual says to adjust the center Cat64 for 210Mv signal and the left and right Cat64's for a 150Mv signal while dolby tone film is running. Is this that important? If so, where do you get a millivolt meter to make this adjustment? What if the CP50 has Cat64B's which have no output adjustment on them?  |  IP: Logged Aaron Sisemore Flaming Ribs beat Reeses Peanut Butter Cups any day! Posts: 3061 From: Rockwall TX USA Registered: Sep 1999 posted 03-14-2003 02:08 AM                     quote: If so, where do you get a millivolt meter to make this adjustment? Most if not all modern multimeters have a millivolt range on them. quote: What if the CP50 has Cat64B's which have no output adjustment on them? In the case of 64B's I believe you can skip the parts concerning controls that the 64B doesn't have. -Aaron  |  IP: Logged

All times are Central (GMT -6:00)

This topic comprises 2 pages: 1  2

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

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.