Film-Tech Forum ARCHIVE: distorted sound from SH1000

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Posted by Steven J Hart (Member # 2340) on 11-19-2005, 08:22 AM:

Last night I took in the Harry Potter opener at a neighboring small town theater. The sound was horrible. Midrange was especially bad with women's voices and strings in the orchestral score garbled and distorted the worst. The theater is equipped with a Simplex 35 driven by an old SH1000 sound head. The head is fitted with a Kelmar reverse scan red light reader. The processor is a DTS 6A(without the D) The owner told me that the sound has been bad on that screen for years, but seems to be getting worse. He had a tech align the A chain within the last six months. After the show we listened to some CD's on the system and it sounded fine. Could there be a problem with the SH1000, like a bad bearing, that would not show up with the A chain alignment? Could the Red LED be set to bright and overdriving the pickup?

I've got a spare Century R3 head (timing belt style) in great shape I'd be willing to let the owner have. Can you drive a Simplex 35 with the R3?

Sorry about the many questions posed in this post.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 11-19-2005, 09:46 AM:

Ben,

Was it our tech that did the A chain alignment? If so please let us know as he should have caught that one.

Your problem could be caused by a number of things....
Bad bearings, hooked sprocket, bad flywheel that has leaked out all its damping fluid, lateral guide arm problems, gear box problems, etc. The SH-1000 is the best sound reproducer ever made and its not at all difficult to get them running correctly. Its better to repair it than switch it out. If it wasn't our tech that was there might I suggest that you call our tech as he may be in your area I this comming week...... he is very familiar with that reproducer.

As to the Century Sound head, yes its possible to run an X-L on one, it easy to set up, parts are off the shelf, and its actually a pretty good combination although a bit unorthodox, its just that the R-3 is no where near the reproducer that the SH-1000 is.

Also, I would trash that POS DTS and get a real processor... its also possible the problem might lay there...... While you're at it shoot the person that sold it to you...! Those processors just don't sound good no matter how well they're set up. Even a used USL JS processor would actually sound better that the DTS.

Mark @ CLACO

CLACO Equipment And Service
1212 South State St.
Salt LAke City, UT 84111

801-355-1250 Phone
801-355-1259 Fax

Posted by Steven J Hart (Member # 2340) on 11-19-2005, 10:43 AM:

Mark, thanks for the info. No it was not one of your techs that did the alignment. I think its got to be a mechanical problem, because we ran a DVD on the vid projector with audio routed through the B chain and it sounded pretty good. I'm going back over there next week to try to check out the sound head and see if I can figure out what the problem may be.

As to your thoughts on the SH1000 versus the R3. I'm running an R5 in my theater and really love it. I like the fact that no pad roller is in contact with the surface of the film and no gear box to wear out. Also, we've had our A chain aligned yearly since 1998 and the tech has never had to make a mechanical adjustment on the head. Thats what I call rock solid! Why do you feel the SH1000 is superior?

My buddy Tom, the owner of the theater in question bought the 6A 'cause he wanted to upgrade to digital shortly. I understand that this model never sold well in the States but that the export market was pretty good. Just hearsay. The person who sold it to him will remain un-named.
Steve

Posted by Monte L Fullmer (Member # 2797) on 11-19-2005, 02:21 PM:

quote: Steven J Hart
The processor is a DTS 6A

Yo-Mark, What kind of processor is this - never heard of it. thx-Monte

Posted by Steven J Hart (Member # 2340) on 11-19-2005, 02:57 PM:

quote: Monte L Fullmer
What kind of processor is this - never heard of it. thx-Monte

Here is the link to the DTS site: http://www.dts.com/cinema/products.php?ID=852563910

I don't know if they do anymore, but DTS used to sell this unit as just an analog processor that you could later ad the drives and circuit boards to upgrade to DTS digital.
Steve

Posted by Monte L Fullmer (Member # 2797) on 11-19-2005, 03:06 PM:

Thx Steve - Just never heard on an "A" model of this 6AD unit. They look better in that link than what they used to look like, but wonder if they got some of the bugs that these "AD" units were loaded with taken care of.

thx-Monte

Posted by Mark Gulbrandsen (Member # 72) on 11-19-2005, 09:59 PM:

The SH-1000 always specs out better than a Century R-type soundhead does. Your R type soundhead also has contact with the film around the scanning drum and they suffer from various bearing and bushing woes much like Simplex 5 Star sound reproducers do. Note that the SH-1000 can also have the same exact film contact path of you follow Brad's modification instructions for the lateral guide assy. Speaking of which the SH-1000 lateral guide does not allow and film weave like happens in all Century reproducers. Side weave is a bad thing for stereo decoding. The SH-1000 has lower wow and flutter mainly because of its dual sprocket-gear box design, the W&F spec can also be made even lower by changing the sprockets over to VKF type. The oil coupled rotary stabilizer flywheel in itself is also a much better design, also used by RCA in their sound reproducers and optical recorders. Century threw out their excellent design Academy Award winning rotary stabilizer with the R-2 sound reproducer, it used magnetic stabilization instead of an oil coupled flywheel, and also had dual sprockets. It was this soundhead not the later R-3 and on reproducers that Century won the Oscar for... but old Centuey ads would lead you to believe otherwise that it was the R-3 and later reproducers that won. But its simply not true.

Sorry but the DTS 6A/AD has the worst analog section of any processor designed in the last decade, even the Peavey stuff was better. It doesn't qualify to be an analog processor in my book... absolitely HORRIBLE moise reduction. As a digital processor it does suffice. If they are going to upgrade that 6A to a 6AD they'd better do it soon. DTS is discontinuing the 6AD and 6D at the end of the year and you may be stuck dealing with DTS in New York for parts IF they are available. Best to replace the thing with something better if this is a money making site [thumbsup]

.

Mark

Posted by Steven J Hart (Member # 2340) on 12-02-2005, 07:24 AM:

Yesterday I went back to this site and replaced the pad roller and bearings and the sound drum bearings. This did the trick. The felt pad roller was worn down about 1/8" in diameter compared to the new one so the film was not being held firmly against the drum. Pad roller bearings were noisey. Sound was much better after doing this, but I still was not really happy. I then moved to the speakers and found that the center channel EV horn had a bad diaphragm. Thanks for all the advice. I'm glad to be able to help my buddy at this location out now and then. He'll be the first to say that even after 40 years in the business he still does not have "the knack" for technical stuff.

Steve

Posted by Demetris Thoupis (Member # 833) on 12-03-2005, 12:29 PM:

It's strange no one suggested to check the speakers first and not the actual projector!! I did the same mistake once and really felt like a fool after I discovered two completely torn screen speakers + 1 subwoofer!!!! After that, this is the first thing I do when checking in on "bad sound".
D

Posted by Monte L Fullmer (Member # 2797) on 12-03-2005, 01:20 PM:

quote: Steven J Hart
I then moved to the speakers and found that the center channel EV horn had a bad diaphragm.

With this comment I have to present a interesting topic: I help open a 14 plex, then was booth manager/engineer here. Shortly we opened up this 14 screen, my highs started to get massive distorted like nobody's business in about half of the auditoriums. It was extremely nasty.

My HF driver diaphrams were all cracked and had to replace all of these defective drivers since at first, we thought we had a batch of bad drivers. Got them replaced, but soon, cracking diaphrams came back. Got a tech in and he was doing some EQ'ing and noticed that in the 500hz range that there was a dip in the display. During the install, the crossover settings weren't done right (for SR-D usage). Plus some of the switches were set to parallel instead of bridged (or other way around, I can't truly remember...)

My other side of the problems were with the DTS-6AD units where the units were sent out broadband instead of Bi-Amp, thus every freq from Sub info to HF's were heading in to the HF channel-why my HF diaphrams were busting like crazy. The crossover chips weren't installed on the top board and had to get those chips to send the units into Bi-Amp and correct this problem.

Was lotsa of fun with all of this... -Monte

Posted by Louis Bornwasser (Member # 3063) on 12-03-2005, 10:05 PM:

You would think all speakers would die if LF is sent to the HF driver. It would seem that some are better than others. EV seems to be unable to take any abuse; while JBL is a little bit more tolerant.

When I go into a strange, biamped theatre, the first order of business is to put up pink noise and then go to the speaker terminals and check to see what is fed to where. I signal trace with the analyzer and many times full range is fed everywhere. Louis

Posted by Monte L Fullmer (Member # 2797) on 12-04-2005, 02:00 AM:

quote: Louis Bornwasser
while JBL is a little bit more tolerant.

True, Louis. These were JBL drivers (can't remember the model no. of these units...). I think that the ones that were more tolerant where the ones that endured this flip-flop thing whereas the weaker ones that took the brunt that caused the diaphrams to split all around the circumference. One house, all three HF's driver's diaphrams did do the split.

Packing up those 35plus lb. drivers up a ladder up and inside the speaker baffle assemblies was TONS of fun...LOL

thx-Monte