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Author Topic: THX and Eighth Day Sound  (Read 5749 times)

Stephen Kirby

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Re: THX and Eighth Day Sound
« Reply #1 on: November 10, 2016, 10:07:14 pm »

Great, slap a label on it and take some money.  Convince people it's somehow better (emperor's new clothes) because the label is there.

When I worked at Dolby the THX stuff was kind of comical.  All of the theater alignment parameters had already been established as part of the installation of the Dolby cinema processor and calibration.
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MikeHarris

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Re: THX and Eighth Day Sound
« Reply #2 on: November 11, 2016, 03:25:23 am »

Can we follow this up with THX certified mixing engineers ?
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Tim McCulloch

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Re: THX and Eighth Day Sound
« Reply #3 on: November 11, 2016, 04:26:42 am »

Can we follow this up with THX certified mixing engineers ?

^^^ This ^^^

Most nights I hear *sound* come out of our systems.  On a few nights I hear *music* come out of our systems. A couple times a year I hear an *experience* come out of our systems that raises the hair on the back of my neck, makes my stomach queasy, releases some adrenaline and reminds me of why I got into this business 30+ years ago.  That "oh fuck yeah!" moment that lasts a whole set or maybe, if we're lucky, a whole evening.

That means we'll need THX certified bands, too.   ::)
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Simon Ryder

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Re: THX and Eighth Day Sound
« Reply #4 on: November 11, 2016, 06:33:17 am »

Great, slap a label on it and take some money.  Convince people it's somehow better (emperor's new clothes) because the label is there.

When I worked at Dolby the THX stuff was kind of comical.  All of the theater alignment parameters had already been established as part of the installation of the Dolby cinema processor and calibration.

It is marketing only. There is no published technical standard for THX. You send them your product, pay your money and if they like it, you get to put THX on it.

The Emperor is suddenly feeling very cold indeed.
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Ivan Beaver

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Re: THX and Eighth Day Sound
« Reply #5 on: November 11, 2016, 07:25:07 am »

The whole THX certified (as far as I know) does not mean much of anything, except a minimum level of performance and you get to pay money to be "certified" and get to use the name-which some people associate with some level of performance.

I would LOVE to see the specs or details of how they think they could possibly do this with a live band with live engineers over a large area.

I don't think THX has anything to do with coverage of the speaker system or the balance of the actual mix.

To me (I could be wrong), it is nothing but a marketing gimmick with no real "result" for the audience.
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Ivan Beaver
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Stephen Kirby

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Re: THX and Eighth Day Sound
« Reply #6 on: November 11, 2016, 09:04:29 am »

The one element that THX added to cinema over the existing Dolby standards for SPL, FR and distortion, was some basic speaker directivity specs.  Ostensibly to reduce sidewall reflections and improve clarity.  I think some of this carried over into their home theater "certifications", although as Ivan often points out, directivity at some convenient frequency is not the whole picture.
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Hyam Sosnow

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Re: THX and Eighth Day Sound
« Reply #7 on: November 11, 2016, 05:05:53 pm »

The whole THX certified (as far as I know) does not mean much of anything, except a minimum level of performance and you get to pay money to be "certified" and get to use the name-which some people associate with some level of performance.

I would LOVE to see the specs or details of how they think they could possibly do this with a live band with live engineers over a large area.

I don't think THX has anything to do with coverage of the speaker system or the balance of the actual mix.

To me (I could be wrong), it is nothing but a marketing gimmick with no real "result" for the audience.

Back in the early 1990s when THX was part of Lucasfilm I worked for Kenwood, which manufactured THX-certified products. At that time there was indeed a set of very specific performance standards with which home theater products (back then it was limited to L/C/R speakers, surround speakers, subwoofers, surround processors and power amplifiers) were required to comply to earn THX-certification. I had a copy of this standards document at my desk (had to leave it behind when I left Kenwood in 2004), to which I continually referred when writing instruction manuals, brochures, training materials and other technical documents. I also passed several days of in-person training (Levels 1 and 2) at Skywalker Ranch. (The Level 1 training was supplied by Tomlinson Holman himself.)

I can tell you, at that time, the THX program was very serious about substantially raising the bar for home-theater performance. I think their ultimate success was limited by Lucasfilm's unwillingness to put enough of their cachet and marketing muscle behind the program, leaving it up to the product manufacturers and dealers to bear too large a part of the burden of educating the general public about the benefits of the program. (A Lucasfilm-sponsored TV campaign during the 1994-1995 timeframe could have done wonders to increase traffic into dealer showrooms, at a time when Lucasfilm's cachet and bankroll dwarfed that of the manufacturers and dealers.)

Eventually Lucasfilm eroded the program's credibility by relaxing certification standards and expanding the types of products they certified, and eventually Lucasfilm sold the program to outsiders. I was always saddened by what I considered a real missed opportunity that the original THX program had to get lots more people caring about superior sound reproduction, right at the very time when home theater was the fastest-growing segment of consumer audio.

And I'll add this: my properly-installed, THX-certified (original 1992-era THX specs) home theater system sounds so much better than a movie theater that I haven't seen a first-run movie in a theater in almost 20 years. (And there are no idiots in front of me yakking-away with their smartphones glowing, I get to control the volume and hit the pause button for bathroom breaks, and the popcorn is cheaper and it's fresh!)

Steven Kirby is right about directivity. The most difficult thing a speaker manufacturer had to comply with was the THX requirement for limited vertical directivity. Most manufacturers (including Kenwood) accomplished this by putting multiple dome tweeters between spaced woofers in a D'Appolito configuration, which limited directivity through destructive interference. (Sound familiar, Ivan?) Klipsch used a Tractrix horn to control directivity, which to my ears sounded light-years better, and those are the speakers I have in my home theater setup, along with a JBL 4641 THX-certified theater subwoofer.
« Last Edit: November 11, 2016, 06:16:16 pm by Hyam Sosnow »
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Scott Holtzman

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Re: THX and Eighth Day Sound
« Reply #8 on: November 12, 2016, 04:55:12 am »

Trivia the THX comes from a movie THX-1138, Lucas's Sci-fi debut.

Wikipedia says it made it's debut in the third Star Wars franchise.  Long before multichannel digital surround, the trick setup of that time was Dolby matrix encoded surround. 

I remember the excitement of my first surround device.  It was a trick Yamaha preamp that had a real channel amp built in.  I remember buying the Yamaha and a Hi-Fi VHS deck, crawling in the attic and mounting the rear channel speakers over the couch. 

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Ivan Beaver

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Re: THX and Eighth Day Sound
« Reply #9 on: November 12, 2016, 08:11:18 am »

Trivia the THX comes from a movie THX-1138, Lucas's Sci-fi debut.

Wikipedia says it made it's debut in the third Star Wars franchise.  Long before multichannel digital surround, the trick setup of that time was Dolby matrix encoded surround. 

I remember the excitement of my first surround device.  It was a trick Yamaha preamp that had a real channel amp built in.  I remember buying the Yamaha and a Hi-Fi VHS deck, crawling in the attic and mounting the rear channel speakers over the couch.
A "trick" I used in the 70s to get "surround sound" was to use 2 speakers (in the rear) and wire them in series, but out of polarity.  So the -'s would be hooked together.

The 2 +s would then go to the "hots" of the left and right main speakers.

So for all signals that were common to both left and right-no sound would come out of the surrounds.

But signals that were different would come out.  The bigger the difference-the more that came out of the surrounds.

Since they were out of polarity, the sound "appeared" to be different.

Nothing like true surround, but it did give a nice "effect" if you were trying to get a "big room sound" out of a small place.
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Ivan Beaver
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Keith Broughton

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Re: THX and Eighth Day Sound
« Reply #10 on: November 12, 2016, 09:47:20 am »

Quote
the program aims to deliver a wider "sweet spot" with improved vocal quality to every seat in the house.
Read more at http://www.soundandvision.com/content/thx-eighth-day-aim-improve-concert-sound#4EcTLXFXOcjHSKzo.99
Riiiight. And nobody has thought that might be a good idea before now  ::)
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Ivan Beaver

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Re: THX and Eighth Day Sound
« Reply #11 on: November 12, 2016, 10:10:33 am »

Riiiight. And nobody has thought that might be a good idea before now  ::)
I wonder if the "improved vocal quality" has anything to do with a STIpa measurement for vocal clarity?  I highly doubt it.

That is measurable-repeatable-definable etc.

NOT a "sounds good to me" opinion.

Probably not.
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Dennis Wiggins

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Re: THX and Eighth Day Sound
« Reply #12 on: November 12, 2016, 10:16:10 am »

A "trick" I used in the 70s to get "surround sound" was to use 2 speakers (in the rear) and wire them in series, but out of polarity.  So the -'s would be hooked together.

The 2 +s would then go to the "hots" of the left and right main speakers.

So for all signals that were common to both left and right-no sound would come out of the surrounds.

But signals that were different would come out.  The bigger the difference-the more that came out of the surrounds.

Since they were out of polarity, the sound "appeared" to be different.

Nothing like true surround, but it did give a nice "effect" if you were trying to get a "big room sound" out of a small place.

This method, to create a center channel from a L/R source, was in PWK's "Dope From Hope" publication.

For me (1978), it was Cornwalls for L/R with a Belle Klipsch for the center.  I was tops.

-Dennis

edit>  The THX cert goal of " the program aims to deliver a wider "sweet spot"... "  doesn't all seem all that ambitious.  That is what I was doing in 1978!
« Last Edit: November 12, 2016, 10:24:30 am by Dennis Wiggins »
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John Halliburton

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Re: THX and Eighth Day Sound
« Reply #13 on: November 12, 2016, 10:26:57 am »

A "trick" I used in the 70s to get "surround sound" was to use 2 speakers (in the rear) and wire them in series, but out of polarity.  So the -'s would be hooked together.

The 2 +s would then go to the "hots" of the left and right main speakers.

So for all signals that were common to both left and right-no sound would come out of the surrounds.

But signals that were different would come out.  The bigger the difference-the more that came out of the surrounds.

Since they were out of polarity, the sound "appeared" to be different.

Nothing like true surround, but it did give a nice "effect" if you were trying to get a "big room sound" out of a small place.

David Hafler published this method.  I also used it while in college on my small system.

Best regards,

John
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John Halliburton

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Re: THX and Eighth Day Sound
« Reply #14 on: November 12, 2016, 10:41:08 am »

Back in the THX heyday, we sent a pair of Servodrive subwoofers to them for certification.  The reply was almost comical.  Best thing they'd heard, very low distortion, except they could hear the  bit of brush noise off the motor in the quiet testing lab(and no full range speakers mated to it).  Consequently, no cert.  As I recall, it cost $2-3k for the privilege.

We went on to supply subs to some IMAX theaters though.

Best regards,

John
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Ivan Beaver

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Re: THX and Eighth Day Sound
« Reply #15 on: November 12, 2016, 11:08:30 am »

Back in the THX heyday, we sent a pair of Servodrive subwoofers to them for certification.  The reply was almost comical.  Best thing they'd heard, very low distortion, except they could hear the  bit of brush noise off the motor in the quiet testing lab(and no full range speakers mated to it).  Consequently, no cert.  As I recall, it cost $2-3k for the privilege.

We went on to supply subs to some IMAX theaters though.

Best regards,

John
It's amazing how many people can't see the forest for the trees.

They get "hung up" on little things that really don't matter at all when used in the context it should be used.
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Ivan Beaver
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Ivan Beaver

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Re: THX and Eighth Day Sound
« Reply #16 on: November 12, 2016, 11:12:46 am »

This method, to create a center channel from a L/R source, was in PWK's "Dope From Hope" publication.


I don't see how this could possibly create a "center channel".

Whatever is panned to the center would have equal output of both the left and right speakers.

Since the "other speakers" were hooked to the hots, there would be no voltage potential across the "special speakers".

You would only get a voltage potential (and sound) on signals that were NOT the same on both channels.

And if you DID have a voltage potential, the out of polarity wiring would make a mess and cancel anything in which you were in the middle and listening to.
For rear surrounds, yes, but maybe I am missing something on the "center channel" thing.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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Dennis Wiggins

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Re: THX and Eighth Day Sound
« Reply #17 on: November 12, 2016, 01:19:22 pm »

I don't see how this could possibly create a "center channel".

Whatever is panned to the center would have equal output of both the left and right speakers.

Since the "other speakers" were hooked to the hots, there would be no voltage potential across the "special speakers".

You would only get a voltage potential (and sound) on signals that were NOT the same on both channels.

And if you DID have a voltage potential, the out of polarity wiring would make a mess and cancel anything in which you were in the middle and listening to.
For rear surrounds, yes, but maybe I am missing something on the "center channel" thing.

You are correct in that the "center" effect was a bit underwhelming as it only played the "stereo effect" in the center.
It was the thing-of-the-day...

Here is another take on it.  http://kimdara.com/speakers/

I ended up taking L/R from the RCA outs and, using two 27k resistors, and developed a mono signal for the true "Center"..  Of course I had to buy another DC-150 to power that.

Mea Culpa: Maybe this (develop mono signal) is was what was suggested in "Dope from Hope" - I have to find that binder - it was quite some time ago.

1st the hair, then the... what was that again?

-Dennis
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Stephen Kirby

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Re: THX and Eighth Day Sound
« Reply #18 on: November 12, 2016, 04:08:37 pm »

Add in a bit of bandpass filtering and the sum difference Hafler thing is basically how surround was initially done.  I remember that the rear channel (which was mono although some systems added some decorrelation to simulate stereo) was LP'd at around 5k, can't remember what the HP was.  Probably around 100.  I think the band pass for the center was a bit further up so that it was built around the speech range for the dialog.
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Scott Holtzman

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Re: THX and Eighth Day Sound
« Reply #19 on: November 12, 2016, 11:39:17 pm »

Add in a bit of bandpass filtering and the sum difference Hafler thing is basically how surround was initially done.  I remember that the rear channel (which was mono although some systems added some decorrelation to simulate stereo) was LP'd at around 5k, can't remember what the HP was.  Probably around 100.  I think the band pass for the center was a bit further up so that it was built around the speech range for the dialog.

Yes,  the first surround was exactly what Stephen describes bandwidth limited and mono. 

Dolby Pro Logic came a few years later and was a four channel system with steering  logic though still matrix encoded (like stereo over commercial FM radio).  The signal has to play on Mono TV systems, stereo and surround sound.  The source was two channel. 

One thing about 1984 telling fun stories of my youth.  The new Corvette had just come out and I wanted one.  Really bad.   I had just gotten a contract to write some software that would program a pager in the paging terminal and reconcile the data with the billing system.  I pitched it to the largest paging company in town and then he asks me the price, I hadn't thought about that.  I just had some demo code that proved I could talk the communications protocol of the paging terminal and access the Burroughs data.

So I went to the Chevy dealer, priced the 'vette, added in the cost of the computer (an S-100 multiprocessor affair running TurboDos) and an extra 5k to cover my expenses. 

When we were done with the job I bet I made about $10.00 an hour, I didn't understand the concept of change orders at the time so the scope of the job was constantly changing.  But I learned the lesson and got the car.

The owner of the paging company ended up being a friend for life, was the best man at my first wedding, and I ended up working for him for quite a few years. 

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Scott AKA "Skyking" Holtzman
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Hyam Sosnow

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Re: THX and Eighth Day Sound
« Reply #20 on: November 14, 2016, 05:41:49 pm »

You are correct in that the "center" effect was a bit underwhelming as it only played the "stereo effect" in the center.
It was the thing-of-the-day...

Here is another take on it.  http://kimdara.com/speakers/

I ended up taking L/R from the RCA outs and, using two 27k resistors, and developed a mono signal for the true "Center"..  Of course I had to buy another DC-150 to power that.

Mea Culpa: Maybe this (develop mono signal) is was what was suggested in "Dope from Hope" - I have to find that binder - it was quite some time ago.

1st the hair, then the... what was that again?

-Dennis

Yes, this is the method Klipsch published. I built one with a volume control and used it to feed a mono amp running a Klipsch Cornwall center channel (I had a pair of Klipschorns for L/R). The volume control allowed me to adjust the center channel volume to achieve a seamless corner-to-corner sonic image with just about any recording (some produced better results than others). As long as the room had corners for the K-horns the results were extremely impressive.

I eventually moved into a home without natural corners in which the K-horns sounded pretty bad, so I went full-on Klipsch THX home theater and sold the K-horns (used the Cornwall as the theater subwoofer for a while).
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