What!? In THX Select modes, sub only used to 35 Hz.!?

Discussion in 'Speakers' started by Kenneth Harden, Jul 22, 2005.

  1. Kenneth Harden

    Kenneth Harden Screenwriter

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  2. ColinM

    ColinM Cinematographer

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    Maybe because room gain adds below 35 (200Cu ft vs 3000), and to curb amp clipping on deep bass?
     
  3. Arthur S

    Arthur S Cinematographer

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    Yep, Select calls only for the subwoofer to extend to 35 Hz. This simply means that for a manufacturer to get THX Select certification for a subwoofer, it must only go down to 35 Hz. This does not apply to the receiver or any other part of the system. The receiver will deliver the full bass signal but the subwoofer doesn't have to deliver below 35Hz.

    Anyone with different info, please chime in.

    Note that Ultra 2 certification requires that the subwoofer deliver down to 20Hz. Again, this applies to subwoofers seeking THX certification.
     
  4. JeremyErwin

    JeremyErwin Producer

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    Hmm. Seems that the THX subwoofer spec has been leaked


    I recall reading an audioholics article which implied that the Ultra2 spec was very hard to meet.
     
  5. Gregg Loewen

    Gregg Loewen Video Standards Instructor, THX Ltd.
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    hi guys

    Ultra2 spec is flat down to 20 without room gain.
     
  6. FeisalK

    FeisalK Screenwriter

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    I don't understand why THX is secretive about the certification requirements - surely if everyone knew that you'd have to have so and so specs to meet THX Select 2 or watever it would make it easier for consumers?

    unless of course it meant people would see that the cert is meaningless - e.g. why is the fact that the subwoofer is capable of going down to 35Hz part of the receiver certification test?

    the sub is an active sub with its own amp, and the receiver puts out whatever freq (below its xover) that is present in the LFE channel. whether a sub can do 35Hz -3dB is not dependent on the receiver, is it?
     
  7. PaulDA

    PaulDA Cinematographer

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    Speakers and subs can get independent ratings for THX, so that's probably why they have various specs for various levels of THX (Select, Ultra, etc).

    THX is superfluous for most people, I suspect. My receiver is THX Select rated, but the only advantage it gives me is knowing the test tones are calibrated to be 75dB on my SPL meter when the volume reads 0dB on the faceplate. Takes the guesswork out of setting my channels (not that I couldn't do it without this feature). Unless I had THX speakers that matched the xover slope requirements of THX, then the rest is meaningless to me. I experimented with using THX on DVD soundtracks and found it useless on most things, and detrimental on a few concert DVDs, so I never engage THX processing.
     

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