Whatever wattage rating it is, it is still easily popped. Like I said, I wiped out a few. Of course, you are entitled to your opinion, and I respect that.

Actually, I do like Altec. I have some Altec 1205's in my possession that are equipped with 802 drivers. I use them on sound gigs with the radio station. They sound very good, and they do a good job if I don't hit them too hard on the high end. I have popped one driver in them, too.

As far as your question as what the CP-50 has to do with popping the drivers, page 7-13 of the CP-50 manual will give you an idea. The following is stated on that page:

"Above 8khz, allow the speaker to set the drop-off. CAUTION: Do not try to adjust the 1/3 octave controls 8khz and above."

Unfortunately, years ago I violated that caution ruling issued by Dolby in some theaters, and I lost some 802 drivers in a very short period of time.

My opinion about the CP-50 is still the same. That old unit is not worth spending money on. When they are removed from service, the best place for them is in the trash, or Ebay looking for a fish to buy them.

Does anyone have a spec sheet 802 drivers? I thought that it said 9 watts RMS, but I could be wrong. I am not going to pick the fly specks out of pepper arguing how many watts they are or are not. They worked very well with 25 watt sound systems in the past, but they just can't quite cut the mustard when used in true high power high SPL digital applications.

In an analog enviroment, they will probably be OK as long as the suggestions from the processor's manufacturer are followed when the house EQ is being accomplished.

I considered your last post a little offensive and insulting. I think this is getting a little out of hand, and if you would like to continue this discussion, let's do it via email. I am finished posting in this tread.

Paul

I figured you might take the last post a bit offensive...to the point I ran it by the moderator first. Some of it was tongue in cheek (mostly about the Altec stuff).

My main complaint with your posistion is that it isn't based on facts, just from the hip to the effect of ...it's old, don't bother with it. The other big objection I have is that you are basing your opinion on the effort it takes without having experienced it yourself yet you would have people believe that it is a long time and high-dollar. When compared to the CP-55, those are just simply not true.

On the Altec 802 front...I will get a spec sheet if it has a 34647 8-Ohm diaphragm or the 34852 16-Ohm diaphragm. The driver can take the 909 (Pascalite) series of diaphragms that will more than double it's power handling though without suffering in frequency response or timbre (part numbers 26420 and 26421). Once upon a time, people used the 808 (Symbiotic) driver since it handled double the power but suffered a bit in the extreme HF.

The CP-50 had nothing to do with popping the diaphragms though...only the technicians and exhibitors did and it wasn't even the EQ controls above 8KHz either. The 802 actually had an easier time with high frquencies that other drivers due to their small size...it is the 500Hz crossover frequency that would be more difficult. Also, in the day of the CP-50 and A-7...most theatres were passive crossover and relatively lower power amps...if an amp was over driven (remember the dynamics of an SVA film was greater than that of a Academy Mono film) then the amp could be over driven...any clipping or like distortion would be directed to the HF section of the speaker. The rational behind the not turning up beyond 8KHz is rather simple...with screen loss coming in around 9KHz and the typical A-chain of the day combined with that films were not mixed for above 12KHz...there simply was more noise up their than signal. And you would have to blast this noise through the screen. To this day, most theatre sound systems are bit phoney in the extreme HF since one is still trying to push through the screen...I find many systems sound artificially metallic above 10KHz.

Since you like to look at the book...The figure 7.2.7 shows the completed B-Chain response to the "X" curve ...note that it follows the curve up to 10KHz (but how could that be? we didn't touch above 8KHz...the treble control is the answer) then a fall off above where 12.5KHz looks to be about 4 dB down from the X curve.

But now lets look at the A-chain side's "after" picture on page 7.12, figure 7.2.6...10KHz is 2 dB down and 12.5KHz was a whopping 6dB down....there just wasn't anything up there to tune for but noise. Dolby uses "side-chains" in their EQ (Cat. 64) so by not turing an EQ pot saves one on noise plus you pick up a phase benefit too. The goal has always been, in any EQ, to turn the fewest number of controls. By stating not to turn the controls above 8KHz, one saved the technician from themselves and their flashy new (and way too heavy) analyzer.

Earlier I mentioned that exhibitors are also to blaim for popping of diaphragms...Exhibitors are always ready to believe they can spend less and get the same. The A-7 has its uses but if the room gets too big, then it is down right silly to think it should be able to do every bit as well as a speaker with a larger compression driver...say the A5. Most technicians, especially back then, didn't know how to calculate how much power they needed to handle based on a speaker's specification. One of the really nice things Dolby Labs has done in their "Technical Guidlines" document is to give a simple method of figuring it out without the complicated formulas. I'm pretty sure they even give the formulas too.

The bottom line though really isn't if the 802 can handle the power...but can the 802 handle the power given the room it is in...one can't have the answer without knowing both sides. Going to the 909 series of diaphragms will often put the 802 over the top if it is marginal. And those diaphragms are current production.

As to posting here vs e-mail here is my position on this (or other topics)...

When one states an opinion such as:...I hate the CP-50 and think the CP-55 is just fine.

I have no problem with that...we are all entitled to decide what we like or don't like be they processors, cars or what have you.

However when one proclaims uneducated opinions as facts (something to the effect that modifying a CP-50 takes a lot more time than a CP-55 or will take every penny you have , in public, that is when I may enter a response. Particulalary when the statements are coming from someone that hasn't done the job.

Now if you said something to the effect of "wow that CP-50 took me all day to modify and the CP-55 took me 10 minutes...I'll never do a CP-50 again!" I might have left that alone though I'll still be there with the stop watch on the CP-55 taking 10 minutes (or even the all day CP-50). That would be a personal experience.

Steve

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"Old projectionists never die, they just changeover!"

Paul, I had no intention of allowing an "offensive and insulting" post and I am quite positive that Steve did not either. I think if you will re-read Steve's post again, you will agree that it is not a direct attack on you personally.

Also for the record (if anyone is interested), I would take an unmodified CP50 over an unmodified CP55 any day...if for no other reason than the CP50 will accept SR cards without ANY modification to the processor whatsoever. Of course, the modifications required to upgrade a CP50 are much easier than upgrading a CP55 too. We don't throw out perfectly good projectionists just because of their age. There is no reason to do the same with a perfectly good processor.

Steve

I've got 4 CP-50's kicking around. Refresh my memory again about what those retrofit boards were for that you were making.

The 506T (as in CP-50 6-track) was a daughter board we made from 1993 to 1995) that would mount on the rear of the CP-50 (it will fit all vintages) that once the backplane is modified to accept it (takes about an hour on the frist one...about half an hour on the remaining ones) will allow one to upgrade (or downgrade in a pinch) the CP-50 with Dolby's cards without having to fuss over it multiple times.

It's birth was really out of the era when we were putting in roll around racks with DTS and Dolby digital racks. The criteria was...our roll around racks had to handle platter or changeover booths (yes we have a 5-plex and a 16 plex where there there may be either)...the processors we had to accomodate was the the entire Dolby line up...in 1996 we added the CP-500 as well). As such we had to have an interface wtih each type of processor and an interface with each type of digital (There were plans for dealing with SDDS-6 or 8 but thankfully none of ours are in rolling racks)...The nifty thing was no matter what host processor or what digital processor were mating up...the same connectors were used ...one for audio, one for control...we used the AMP circular connectors. The reader (and motor) connectors were broght out to the front panel for quick hook up...

Any way...the 506T was initially designed to accommodate the mobile digital issue and the first one resembled Dolby's Cat. 651 (go and look THAT one up!). It wasn't too fancy...just provided the all familair "JM-11 and JM-22" IDC connectors with some active level matching to provide a 300mV buss level. I think I had the optical surround get a 3dB boost on the first one too to mimick the Cat 441 on the CP-65.

Well then we noticed there should be some other features....

12th revisions later...there were some near misses along the way except the single source switch chip I was going to use got discontinued after prototype.

The 506T turned into the little fix it board for the CP-50.
First off you modify the CP-50's motherboard once and deal with any upgrades as they come.
The Mobile digital input was also a necessary item (the pinout doesn't conform to anyone eles standard on the DB-25 connector..there were reasons it was chosen).
What if you have a permanent digital processor...say a DA-20 but you have a moble DTS for those pesky Universal films (remember when Universal was DTS only...wouldn't want the big film to not play in digital). Therefore it can accomodate up to 3 digital inputs though one I call the pink noise jack (more on that later). So there is a terminal block to connect your DA-20 (pinout matches the CP-65 and can accept fanning strips or bare wire!)...the "JM-21" connector (since the DTS-6D wasn't out yet) but the DTS-6D can work with it since a simple ribbon connector with a DB-25 on one end and a IDC on the other is a direct pin out. So now you can have both digitals in the rack or one in and one out.
What about SR...well we got the connectors out for a quick and easy hook up to an SRA-5, SMART SR1 or USL SRM-10. Furthermore we put in a pair of line amps to bump up the optical level by 3-dB when in SR if the ouboard SR adapter didn't (the SR-1 didn't).
You say you don't want to blow money on an external card cage and would rather just shove some Cat. 280T's in place of the Cat. 22s? No problem...the 506T will sense which card (22 or 280T) is installed and bump up the optical level by 3dB to match the digital level
But wait, there's more! That pesky ADA...we put in a buffered line amp that is pre-fader, pre EQ with a trim pot. Hearing Assist output (47 Ohm output impedance). Center channel is emphasised the surround channels normally don't have their resistors stuffed since what do people that are trying to understand the film want to hear that garbage for? But if you disagree, the surrounds can be their too!
Then I put in a Pink Noise connector...not a standard one though..it uses the AMP MR style connector...it can be used as a third 6-channel input or with a Cat. 85C (or SG-1) with an appropriate adapter cable...it is your pink noise input jack...on you generator...Le is mapped to Subwoofer, Re is mapped to Right Surround, S remains Mono or Left surround...no more pulling and swapping cards.
If you wanted to be on the cheap and you had a Cat. 160 laying around, you could use the mag section of the Cat. 160 for digital subwoofer...though not entirely correct since the mag section has a downward expander...when you could get a proper Cat. 560...move the jumpers and everything is in business! (I'm pretty sure we implemented this feature).
Cat. 117? Cat. 517? No problem, we take either ...just move the jumpers to which card you have installed...the signal routing and capacitor/line amp issue is taken of.
Lastly, when using the Cat. 560 with the Cat. 517...watch out if done the factory way...the surrounds will be out of phase with each other on optical...we take care of that too...everything is in phase...just plug in whatcha got....including a Cat. 560 without a Cat. 517.

We had one accessory for it...the front panel module...two LEDs and a switch. The LEDs indicated "Digital" and "SR"...the switch could force optical sound in case of a digital problem or lock up (the 506T does take its commands from the DA-20 and or DTS in normal mode so it is automatic but what if the DA-20 doesn't drop out when everything sounds like it is under water and TITANIC isn't on the screen sinking?)

Man, you guys got me to think about this thing when it was put to bed almost 6 years ago!

Due to it's low volume, large size and hand builtness...it wasn't cheap...I wanna say it was $425 or $475 List. Again, it was designed and built in a day where an exisiting theatre wanted to be able to move a digital processor about and there was a mixture of processors and digital processors.

Oh and I only ever made a prototype PN cable (which has now turned into a Cat. 85C to Ultra JS series pink noise injector).

Steve

Let it be known that I stand corrected.

Many aplogies to Steve Guttag.

I have to admit I put on my cross-country shoes and waltzed all over my schwantz. Nothing like going to the bathroom in 5 different directions....Ouch! That hurts!

Thanks to all who tried to re-orentiate my thinking.

Paul

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Although, I've been told to do stuff I knew was wrong, and if anyone's been a tech for any length of time I'm sure they have, too.

Things like Paul recounting his experience with changing out CP-50 backplanes in mass due to a manufacturing defect under warranty. Also the bulk of Paul's CP-50s fell into the class of pre-1980 so it would have the older cards even side swinging doors and many without even the Cat. 150 (I believe the Cat. 150 was out in 1979...since there is an "S79" document that has it. In Dolby speak...S79 would mean SanFrancisco 1979.)

Cleary, if one lived through that...it would form an opinion. Now if you did a bulk of your work in the 1980s....the CP-50 was pretty much a reliable beast...however the CP-55 was the one with problems en mass...anyone remember the dreded "STC" relays for bypass? To this day we carry around bypass relays to pitch any of those white pieces of crap.

Neither of the above problems are indicative of a design flaw with either CP though...they were both unfortunate circumstances that caused grief to the field guys, like us.

Now as to the signal path of each....many find the CP-50 an easier path to deal with and it's upgrade path is more recent than the CP-55's and thus offers some improvement not offered to the CP-55...the Cat. 517/560 stuff came out in 1992 (at least that is the copyright on the card(s)). The VCAs on the 517/560 are all the dbx (now made by THAT corp) with better channel to channel tracking, lower noise and distortion...but, as Mark said...the movie goer isn't going to notice the difference and I claim they won't notice the shortcomings of the Cat. 117 either.

Next, we discussed the upgrade path for a CP-50 for DTS digital vs the CP-55. Paul asked I recount some for the benefit of others to understand better. After all, when respected people at Dolby say, don't bother...why challenge them? The fact that it is a bit easier to use DTS doesn't encourage Dolby to promote the idea either.

Ok...first...you just want digital....you order your DTS for a CP-50. One has to clip 4 resistors (I think only 4 need to be clipped, not all 7...but they are grouped so clipping a few more doesn't take any more time, really). If one clips one-end, they could be resoldered if needed in the future. Then solder the 8 wires from the D567 board to the solder pads where the resistors are on the CP-50 backplane...where to mount the D567? Simple, DTS has the screw holes that span the Cat. 560 card mounting holes...use some 4-40 hardware and standoffs and you are effectively done for 4.0 or 4.1 digital...no backplane butchering (no traces cut).

The DTS board has the 25-pin D connector for the DTS player and the contol connector to switch the relays on the D567 board. If one doesn't have a Cat. 560 yet, you have mono surrounds...for subwoofer, if you have one you can connect directly to the D567 board..no it won't track the fader this way but for features it will be within 3-dB in most houses since the volume level for most theatre normally floats no more than one number (6-7 or 5-6 depending on tuning).

If you get the Cat. 560, then you can feed the subwoofer with the fader included...there will need to be a few wires soldered to the backplane to route the surround lines, subwoofer line and the contol line. The D567 board has a dry contact to allow the logic switching of the Cat. 560 into digital mode. Overall...it is starting to resemble the appearance of the CP-55 upgraded with the Cat. 441. They are on par in terms of wires and effort at this point with the CP-55's backplane now having one trace cut for the subwoofer line to have a resistor installed.

The Cat. 517 is a bit more involved and some backplane mods are needed to cut out Left and Right signals from going to and from the noise reduction's line amps also there are some series blocking caps that should be jumped out. This one is probably the most time consuming and so far the only point where traces HAVE to be cut.

So one can see there is no real "butchering" of the backplane...some tack soldering to get the wires to the solder pads but the CP-50 and CP-55 are on par with either other in this manner.

For SR...one can conger up the butchering as described in the SRA-5 manual. But since the SRA-5 is gone (and so is Ultras and SMARTs outboard SR cages...Pana's may be coming soon though) but most CP-50 owners are just happy enough to plunck the Cat. 280Ts right in the CP-50 in place of the Cat. 22s...lets face it, all that is coming out right now is in SR so the Cat. 280s can just stay there. No mods are necessary but there is a level problem of 3-dB if used with Dolby Digital since SR is to be boosted 3-dB over A type...but with DTS...one merely has to calibrate the DTS player for 3-dB less and they match once again so no problem in this senerio...for Dolby Digital, you should get a line amp to boost Lt/Rt by 3-dB (or the 506T). Conversely, the CP-55 must have it's Cat. 243 modified by stuffing a couple of diodes (in non standard places) to make format 03 into format 05. The Backplane must then have a wire connected across the back to tell the Cat. 222SR/A switch modes.

Note, at this point the 222SR/A costs more than a pair of Cat. 280s...the Cat. 280s are THE reference SR card by Dolby...the Cat. 222SR/A is a poor imitation using the Dolby-S chip...listening to the HF information, the 222SR/A will sound spitty and be more apt to pump like other SR knockoffs...it may (or may not) be the best SR knockoff but a knockoff none the less. So for the CP-50...SR is not only cheaper but results in a superior SR reproduction and less work upgrading.

In short review...Upgrading the CP-50 is not the horror story Dolby would have one believe and in fact can go smoothly, and quickly to the degree the exhibitor wants. As compared to the CP-55...they are on par for full digital upgrade in time and effort.

Whether or not a CP-50 is a good candidate for upgrade really depends on the unit. If you have one where the edge connectors are flaky...thats it..it's done...but this isn't just an age thing...it is more of an environment thing and oxidation or the batch of edge connectors in the unit and how well they were plated. Also, if you have the cat 110/116 thing...it is also a bit too far back. But if you have a late model one or one that you have more or less kept up over the years..perhaps already has SR or subs...then it IS something to be considered. It is a judgement call that the exhibitor and his trusted service company should discuss between themselves...not an automatic decision either way.

Can I be done with this one now?

Steve

Now, I am off to Idaho Falls, Idaho to yank a DTS and send back to Karen because it died.

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...then again....

What's the problem Paul? One nice thing about all the digital systems that are outboard is that they unplug real easy even by the novice...I have done shop repairs for units in distant places by having them ship me the unit.

Steve