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Author
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Topic: New Cross-over card for THX monitor
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Bill Purdy
Expert Film Handler
Posts: 139
From: Seattle, WA
Registered: Oct 1999
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posted 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? ------------------
Bill Purdy
Component Engineering
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 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. ------------------
"Old projectionists never die, they just changeover!"
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 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 ------------------
"Old projectionists never die, they just changeover!"
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Bill Purdy
Expert Film Handler
Posts: 139
From: Seattle, WA
Registered: Oct 1999
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posted 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. ------------------
Bill Purdy
Component Engineering
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Randy Stankey
Film God
Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99
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posted 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?
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