Enhance 35mm optical mono sound?

[Jerry G. Axelsson]

Hello fellow colleagues,

I have thought about options to enhance the sound quality on 35mm prints with optical mono.

We use Kinoton rev.scan readers and a CP650/CP200 combo with QSC DCM-30D filters going to three way JBL speakers.

For the most part optical mono sound sound thin or unsatisfying on 35mm i think. (Dolby A/SR/SRD/DTS and 35mm & 70mm MAG sound fine). The installation of the equipment is done properly.

I am familiar with the idea of rebuild red light to white LED/IR. But beyond that, what about using an alternate EQ setting to make the mono sound fuller or less harsh?
The QSC filter gives you that option with alternate EQ setting.

Then there is also the discussion with going "off-spec." with the Academy curve and so on.
We play a lot of analog film in our cinemas. A great deal of the prints are mono.

Any suggestions welcome.

Thank you in advance.

[Gordon McLeod]

Find a used Kintek unit (aka the 3 yellow boxes) The KT21 has a dynamic range expander based on a DBX 3BX circuit and will do wonders on cleaning up older mono tracks the KT22 will generate a pseudo stereo effect across the screen that on many movies is effecive and the KT24 Surround generator will fake a surround channel based on signal level and spectrum. It will also generate a sub base channel that can get a bit better bottom end if used judiciously

[Leo Enticknap]

The Rosbeek dual light reader made a huge difference when we installed them at the Egyptian. With the white LED active, the signal-to-noise ratio on thin VD and unshuttered unilateral VA tracks improved by an order of magnitude. The bass sounded a lot better, too.

[Jerry G. Axelsson]

Hello Leo, I am familiar with Ronalds work for the Egyptian. Ronald was a close friend and did not find time to help us with this before his untimely passing...

[Sam Chavez]

Regards Kintek; It's a little late in the day to resurrect that sorry hot mess. Apart from perhaps and only occasional beneficial effects of expansion and pseudo stereo, the Kintek hardware was notoriously unreliable even when it was still in business ending in the early '90's. You'll have to pardon Gordon, he's in the grip of nostalgia. LOL

[Van Dalton]

Aren't IIRC the Dolby 699 and 700 white-LED or incandescent readers? It seems to me (hypothetically) that if you can find one of those* it could probably be mounted in an adjacent spot on the penthouse level and used for silver tracks.**

Could an old red-LED SR reader be refitted with a white LED or is the pickup not sensitive to the wider-bandwidth light?

* E-bay.
** I fully and truthfully believe I am talking out of my ass here.

[Leo Enticknap]

Hello Leo, I am familiar with Ronalds work for the Egyptian. Ronald was a close friend and did not find time to help us with this before his untimely passing...

I'm sorry - I had no idea that he had passed away. Looking more closely at the Rosbeek Techniek website, it appears to have last been updated in 2017. I hope the company is still in business.

Edit: Just found this page. Very sad news.

[Jerry G. Axelsson]

Thank you Leo. This matter was on my and Ronald´s "to do list". But we did not find time to do it in the end. The white LED/IR conversion was under development for the Kinoton DP70 reader, but was never implemented. What do you colleagues think about using an alternate EQ-setting for optical mono. "A flick of a switch on the QSC-filter"?

[Marcel Birgelen]

We did some post-work on digitized old 35mm mono prints, where we expanded the dynamic range and experimented with a bunch of filters to keep the noise down. The results were pretty stellar, but obviously nothing can really come close to the dynamic range and noise level of modern digital formats, even just in mono.

We did some experimental 3-channel pseudo-stereo in post on some old mono content using the DTS Neural plugins. They use a whole array of modern techniques, including some machine learning to create pseudo stereo or even surround. The results may vary between source material, but are pretty convincing.

Unfortunately, all of this was in post, which gives you a lot more options than during live playback... There are quite a few audio processors out there that can perform all kinds of noise reduction and can expand the dynamic range. While I've never tried it, I guess the cheapest way to get DTS Neural live decoding currently is via one of those home cinema AVRs...

[Steve Guttag]

Regards Kintek; It's a little late in the day to resurrect that sorry hot mess. Apart from perhaps and only occasional beneficial effects of expansion and pseudo stereo, the Kintek hardware was notoriously unreliable even when it was still in business ending in the early '90's. You'll have to pardon Gordon, he's in the grip of nostalgia. LOL

It went on a bit longer (I think it made it to the early 2000s)

As for psudostereo, they were the best at it. The original 3-box system (yellow or black faceplates) didn't have any particular reliability problems, that I recall. I don't recall any particular reliability problem with the KT-700.

More to the subject...the Kintek system could add a dimension to a mono track and definitely can clean it up a bit with the expander section, even if the fake-stereo stuff isn't used.

As for EQing mono tracks to provide a better quality sound...maybe. Who is the judge of when they sound "right" or even better. Probably having a 3 or 5 band "tone" control might not be a bad thing to have.

[Sam Chavez]

Nostalgia ain't what it used to be. The only place on the west coast where Kintek caught on was Hawaii. and they had nothing but problems sending one board or another back to Boston. Nothing I hate more than a nervous soundtrack that seems to change from one minute to the next. The people working in cinemas back then when we had someone in the booth tended to be aggressive with the settings. (Now of course we have no one.) And tis all assumes the optical soundhead was set up properly, illumination, flutter, etc. Both Italian brands had trouble with this back then. I agree most mono optical tracks could stand a little more HF and perhaps a tiny bit of expansion. But not user adjustable.

[Steve Guttag]

What I saw fail most was the Digimate power amps and their exciter supplies and their booth monitors would blow out (and couldn't deal with bridged mono amps. I didn't want to imply that Kintek was the model of quality but I can't claim to have EVER had a 3-box system fail and I just don't recall KT-700 board failures though there may have been. I never put in the KT-800 or the various "things" that were in the Digimate frame.

But for getting a bit more out of mono, I'm okay with old-school Kintek. I do come back to...okay so you put in some tone controls...who's golden ears are setting them? Or do you fiddle with them for each movie? If so, you get to be inconsistent from show to show.

At the AFI/Silver, the subject of mono and EQ came up and I did put in a "Mono EQ" DSP where the then Technical Director could go into the theatre and have a 5 band tone control...it never got used (a bit a story there but not for this forum).

[Jerry G. Axelsson]

Thank you all for your contributions to this thread. I wish you a good weekend.

[Vern Dias]

When I had my home theater setup (20 years ago) which had RCA MI-1040 sound heads, I used the DBX 3BX expander with good success for my optical sound. However, this was back in the day before optical sound tracks lost their silver.

[Gordon McLeod]

Never had a 3 box system or a failure in the 700 serries. The 800 serries seemed to have alot of failures as were the digmate amps. We had a few but not many failures with the BSR amps