This is topic New Cross-over card for THX monitor in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Bill Purdy (Member # 202) on 03-01-2001, 04:23 PM:
For many years people who wanted to quit their THX certification had the problem that THX wanted their leased cross-over cards returned. While we were still manufacturing the Model 3417 monitors for THX, we didn't feel it would be proper to make a version of the card. Now, however, it has been well over a year since we stopped making the 3417 and in addition, many more theatres are anxious to save the license fees. Therefore, we now have available a direct plug replacement for THX's cross-over card having the same cross-over point, the same delay characteristics, the same gain and so on. Actually, some of us think it is a better design than the original. These cards are available now through normal distribution channels at a List Price of $177.00. 
We will have these (and other neat stuff) to show you at ShoWest at our booth 815/817. Please drop by!!
Just for fun, a trivia question for the day:
What is the significance of "3417", the Model number of the Monitor?
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Bill Purdy
Component Engineering
Posted by Scott Norwood (Member # 30) on 03-01-2001, 04:28 PM:
Doesn't 3417 have some significance to "THX-1138"? I haven't seen the whole thing, but I'm pretty sure that there's something there...
Isn't there also a license plate in "American Graffiti" that says "THX-1138"?
Posted by Aaron Sisemore (Member # 145) on 03-01-2001, 05:26 PM:
The plate on the car in 'Graffiti' was THX-138, but the connection was the same, obviously.-AS
Posted by Gordon McLeod (Member # 33) on 03-02-2001, 09:15 PM:
I believe THX has a patent on the crossover design It is US4569076 it includes the use of a delay line and the filterslope and cd horn correction
Posted by Joe Redifer (Member # 3) on 03-02-2001, 09:22 PM:
I don't think you can patent delay settings and crossover points. Just as long as they aren't using any THX proprietary technology I think they'll be OK.
Posted by Randy Stankey (Member # 64) on 03-02-2001, 11:57 PM:
Wan't that the "name" of THX-1138's friend that helped him escape from the city?
Posted by Mark Gulbrandsen (Member # 72) on 03-03-2001, 10:40 AM:
I definately side with Joe on this. There is no way you can patent a cross over point,curve, or delay. You can only patent how it is done. The more power to you Bill. The THX thing is really turning into a farce anyway. Try to get them to do just a couple of screens in a plex anymore. Good luck! They seem to want all or none at all.
Mark @ GTS
Posted by Ken Layton (Member # 133) on 03-03-2001, 10:58 AM:
They sound just as good. Direct plugin replacement for the original (and it uses newer technology). The only thing I have noticed is that you have reset your house SPL's. I like these cards. They are excellent and at a very good price, too! 
Posted by Steve Guttag (Member # 268) on 03-03-2001, 01:59 PM:
It's been a while but I think the patent on the card has to do with how Thom Holman accomplished the crossover (24dB/Octave) that "just happened" to introduce the requisite amount of LF delay to the system to work with the JBL 4675B (and later). So the patent (and I haven't looked at it) probably deals not with the crossover point but the circuit that accomplishes both objectives at the same time. It is one of the reasons why the speaker must fit the mold...ie the approved speakers of the era all had the basic JBL 4675 look and size.
Now with DSP technology, it is easier to make the crossover be optimized for different speaker designs.
Good Luck with the new crossover board. I'm sure it works just fine.
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"Old projectionists never die, they just changeover!"
Posted by Steve Guttag (Member # 268) on 03-03-2001, 02:29 PM:
Gord:I just took a quickie web look at the patent you listed. It appears to be a methodology patent for the whole THX system rather than the card specifically though the gyrator circuit Mr. Holman used to achieve the 1.9msec delay is mentioned. I didn't see anything the prevents anyone from making a crossover card that does what is in the patent. Since there were crossovers that did what his did before and after the 3417 came out. About the only thing that would be a no-no would be simply building the same card/circuit. What are the life spans of Patents nowadays? 17 years? Didn't THX happen around 1983 with Jedi? If so it may be moot anyway.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Gordon McLeod (Member # 33) on 03-03-2001, 02:34 PM:
I am not knocking the product as it is a timely one and as always I am sure it is up to the high level of standards of other CE products.
I was just asking the question as the patent did embody the works of other which I did find odd
Most patents are 25 years but are renewable in some cases
Posted by Bill Purdy (Member # 202) on 03-03-2001, 04:55 PM:
We have not in any way infringed on their patent. As indicated above, the patent didn't even include the cross-over card. Holman himself suggested the we just use his circuit and merely do a new board layout to get around any copyright. We, however, decided to do a new circuit with newer lower noise op-amps and tighter slopes at cross-over.Randy is essentially correct about "3417". I don't remember, but one of the people at LucasFilm (no longer there) was the one who suggested the number as being 1138's girlfriend. Typical George Lucas.
See y'all at ShoWest---booth 815/817.
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Bill Purdy
Component Engineering
Posted by Randy Stankey (Member # 64) on 03-04-2001, 12:38 AM:
My guess about the number was a three way toss-up. I was thinking either the girlfriend the guy who helped him escape or Donald Pleasance's character. I just picked one.Did you ever notice in just about all of Lucas's movies any cops or cop-like authority figures all have distorted voices?
Cops in THX... Storm Troopers in Star Wars... Darth Vader... Storm Trooper Droids in SW:Ep1...
Is this a Freudian thing going on here?
Posted by System Notices (Member # 2357) on 09-08-2008, 12:49 PM:
It has been 2745 days since the last post.
Posted by John Walsh (Member # 168) on 09-08-2008, 12:49 PM:
I just 'fell' on this topic while looking for something else ... I thought THX wanted the entire monitor returned, not just the x-over cards. Is that true? If so, I know a place that kinda got screwed...!
Posted by Bill Gabel (Member # 1105) on 09-08-2008, 02:00 PM:
Three former Cineplex houses that I ran in Los Angeles that were THXed still had their monitors minus the x-over cards.
Posted by Louis Bornwasser (Member # 3063) on 09-08-2008, 06:17 PM:
No, the monitor/card cage was an outright purchase. The cards had to be returned.
BTW: I still have about 40 dbx 900 card cages, mostly from ex-thx National Amusement locations. In addition, I have an Ashly prototype card about the same as CE's. Louis
Posted by Dustin Mitchell (Member # 372) on 09-08-2008, 09:19 PM:
I have no idea about anything that went on 'upstairs', but we are no longer THX certified and all we had to to was pull down the signs and replace the card in question in the crossover.
Oh, and the little plate on the front of the monitor that said 'THX', had to pull that off too ![[Roll Eyes]](rolleyes.gif)
Posted by Steve Guttag (Member # 268) on 09-08-2008, 09:37 PM:
THX never owned the monitor...what a theatre "purchased" was the monitor. The Cards were merely licensed.
As such, the new CE cards effectively revitalize the monitor. Note one is also advised to go through them and change the volume control and such to keep it clean sounding.
Steve
Posted by Sam D. Chavez (Member # 1841) on 09-09-2008, 12:32 AM:
I believe the arrangement back then was you bought the frame but "leased" the cards.
(I see Steve beat me to the punch)
THX 3417 was THX 1138's wife or significant other in the film of the same name.
I manufactured the 3417's successor, the THX D1138. 991 units and it was a wrap. Already a long time ago.
Posted by Steve Guttag (Member # 268) on 09-09-2008, 01:21 AM:
I believe her name was LUR.
The THX D1138 did just fine in its time. I still have 4 of them that I directly care for in THX certified theatres.
Steve