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Old 8th July 2006, 06:03 AM   #1
mike.e is offline mike.e  New Zealand
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Default THX requirements (details required)??

Hi Im trying to find the exact THX requirements for subwoofers.

The only details I can see is the following

It doesnt actually mention any numbers.

Quote:
Metrics Tested on THX Speakers:

Axial Frequency Response Analysis
Directional Characteristics
Sensitivity
Impedance
Harmonic Distortion
Low Frequency Cut Off
Phase Angle
Stray Magnetic Flux
Maximum Output Level
Acoustic Noise Level
Polarity
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Old 8th July 2006, 06:31 AM   #2
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Come on Mike, you know better. The bottom line requirement is that your equipment has decent performance AND you pay to be able to stamp a THX certification on it. If you are talking about a cinema, then there are most likely some actual measured requirements, but again anyone who thinks the primary motivation isn't money is naive. It's all about selling equipment, with (in the case of consumer audio) only a cursory regard to actual performance.
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Old 8th July 2006, 11:33 AM   #3
mike.e is offline mike.e  New Zealand
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hey john.Didnt realise it was THAT useless a thing.

Whether its baloney or not,id like to know exactly what they think is good enough for THX
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Old 8th July 2006, 12:07 PM   #4
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I suspect you have to pay to get the THX specs, and probably sign a NDA.
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Old 8th July 2006, 03:31 PM   #5
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Mike,

For THX certification of a home theater the sound requirements are:

- Mid band pink noise < +/- 3dBC between any 2 seating positions.

- No audible distortion from subwoofer playing program material at 115dBC.

- No audible distortion from satellites playing program material at 108dBC.

- Background noise < NC22

- At least 4 surround speakers (2 side and 2 rear)

- Audio performance measurements taken using 1/12 octave RTA with four microphone spacial/temporal averaging or better.


THX is a vague target kind of thing and there are a number of different levels/types of certification. There's even one for computer multimedia setups.
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Old 8th July 2006, 05:08 PM   #6
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I remember seeing a number of 115dB at seating, with low distortion, and flat to 20Hz.

What they mean by low is anybodies guess.

I think it was in a review of a thx approved sub, so maybe have a search around the review sites and see if any more concrete info is leaked out.

Rob.
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Old 9th July 2006, 12:30 AM   #7
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Hi guys.Yes I saw the '115dB SPL' rating also, with 'no distortion' which is stupid.

It is pretty basic isnt it!
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