THX speakers

Discussion in 'Loudspeakers' started by jmhc, Jan 7, 2010.

  1. jmhc Audioholic Intern

    jmhc
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    Hello there:

    My receiver (Onkyo TX-SR805) has an option in which you can specify if the subwoofer is THX certified or not.

    My question is, besides the certification what are the differences between a high quality THX subwoofer/speakers and a non certified high quality subwoofer/speakers?

    Thank you.
    jmhc,
  2. bandphan Banned

    bandphan
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  3. jmhc Audioholic Intern

    jmhc
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    jmhc,
  4. zhimbo Audioholic General

    zhimbo
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    I would guess that it defaults to some default THX bass management settings instead of computing them during auto-calibration...?
  5. sptrout Audioholic

    sptrout
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    Straight from THX (translation to English not provided):

    "THX Certified Subwoofer Performance
    THX Select2 and Ultra2 Certified subwoofers extend to 20Hz (-6dB), providing a rich bass response for multi-channel soundtracks. And, when combined with a THX Certified receiver or pre-amp using THX Boundary Gain Control technology, bass response is accurate with or without room boundaries - allowing consumers flexibility on subwoofer placement."

    Here is a link to a much better discussion about THX subwoofers, and THX in general: http://www.hometheaterhifi.com/technical-articles/165-what-it-means-and-how-to-use-it.html?start=3
    Last edited: Jan 7, 2010
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  6. BoredSysAdmin Audioholic Warlord

    BoredSysAdmin
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  7. krzywica Audioholic Samurai

    krzywica
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    Make sure you put a flux capacitor between your THX gear and your receiver if you get some. That way you aren't limited by placement and can put your speakers wherever you want with no audio penalties.
  8. BoredSysAdmin Audioholic Warlord

    BoredSysAdmin
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    you can get flux-capacitor here, just make sure to provide 1.21 Jigawatts to power it.
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  9. mtrycrafts Audioholic Slumlord

    mtrycrafts
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    Oh, is that why they print those? ;):D
  10. BoredSysAdmin Audioholic Warlord

    BoredSysAdmin
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  11. jmhc Audioholic Intern

    jmhc
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    Forgive me if I sound ignorant. I assume the 20hz (-6dB) extend reffers to the SW frequency response, but take a look at this:

    http://atlantictechnology.com/default.asp?NodeId=51
    http://www.teufel.eu/THX/Theater-8-THX-Ultra-2.cfm?show=technik#tab
    http://www.teufel.eu/THX/Theater-10-THX-Ultra-2.cfm?show=technik#tab

    All of them are 25hz (-3dB)
    jmhc,
  12. popotoys Audioholic

    popotoys
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    I think as well, if you choose this, all speakers are set to small and the crossover in your AVR is set to 80hz.
  13. BoredSysAdmin Audioholic Warlord

    BoredSysAdmin
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    Atlantic sub is not Ultra2/Select2, just regular THX Select certified,
    Teufel M 11000 -
    Teufel M 12000
  14. sptrout Audioholic

    sptrout
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    The THX spec is -6dB at 20Hz and most of the speakers you referenced show -3dB at 25Hz as you said (although I think the last one does mention -6 at 20Hz). The only reason that I can think of for the difference between THX and the listed speakers are that speakers are almost always rated down (or up) to their -3dB point. Why THX choose -6dB at 25Hz is something that they only know. My guess that all the speakers that you listed could do 20Hz at -6dB, but they choose to stay with the standard speaker specs. That is ALL a guess on my part.
  15. jmhc Audioholic Intern

    jmhc
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    I thought THX select and Ultra has the same certification standards and the only difference between them was the size of the room where the're gonna be used.
    jmhc,
  16. sptrout Audioholic

    sptrout
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  17. jmhc Audioholic Intern

    jmhc
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    I started reading the article you mentioned, about reference level it says:

    "Any single channel of the system is calibrated to play 0 dB FSD (the loudest sound the sound track can contain) at 105 dB (115 dB for the LFE channel). "

    Does this mean that in order to play movies at reference level I have to set my receiver volume to the 0.0dB mark??

    Does this means that if I set my receiver at -20.0 dB the loudest sound would be 85 dB and 95 dB for LFE??
    jmhc,
  18. JerryLove Audioholic Samurai

    JerryLove
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    If your receiver is THX, that's how I read it, and it fits my experience with my THX gear (though I've never pulled out an SPL meter, I routinely run movies at -10

    My THX Marantz does not top out at 0 however.
  19. jmhc Audioholic Intern

    jmhc
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    This is a quote from the article that SPTROUT mentioned above
    http://www.hometheaterhifi.com/technical-articles/165-what-it-means-and-how-to-use-it.html


    .

    My receiver's manual says that if I'm using a sound level meter to adjust the level of each speaker the device must read 75dB for each speaker at the listening position.

    What about subwoofer?? does the device must read 75dB for it or 85dB???.

    Thank you guys for all your help and commentaries.
    jmhc,
  20. sptrout Audioholic

    sptrout
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    Yes, when using an SPL meter all speakers should be set at 75dB SPL assuming that you are using a bass management system (BMS) either in your AVR or in a Blu-ray or DVD player that has its own BMS and you are using analog connections between them. It starts to get real confusing when no device is providing bass management (which is common when using analog interconnection between older devices), then you have to boost the LFE channel either 10dB (if using "large speakers") or 15dB (if you are using "small" speakers).

    Setting the LFE channel to exactly 75dB SPL with an SPL meter can be a real pain since the level meter typically jumps all over the place. Therefore, you have to kind of guess what the proper setting should be (try a setting and see if you like the results).

    Even though it is the recommendation that all speakers be set equally, some folks will add a couple dB to the LFE channel because they like the extra bass.

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