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Author Topic: THX and Eighth Day Sound  (Read 5751 times)

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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Ivan Beaver
Danley Sound Labs

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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
Danley Sound Labs

PHYSICS- NOT FADS!

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
River Delta Audio is now:

Ghost Audio Visual Solutions, LLC
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