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How Many dB for Subs?

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  • How Many dB for Subs?

    What do you shoot for in your Home Theater designs, concerning dB capability on your subs?

  • #2
    Re: How Many dB for Subs?

    I have never measured my HT but if I did I'd want 3-6db more output capacity from the sub/s than the mains are capable of when they're all on.
    Paul O

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    • #3
      Re: How Many dB for Subs?

      Thanks, Paul.
      I just read on the THX site that reference is 85 dB, with 20 dB of headroom, which would mean 105 dB capability for the mains and using Paul's advice of 3-6 dB additional capacity on the subs, it would be something like 108-111 dB.

      Does this sound reasonable?

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      • #4
        Re: How Many dB for Subs?

        83 - 85db is a common target.
        "Not a Speaker Designer - Not even on the Internet"
        “Pride is your greatest enemy, humility is your greatest friend.”
        "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

        Comment


        • #5
          Re: How Many dB for Subs?

          Originally posted by PassingInterest View Post
          Thanks, Paul.
          I just read on the THX site that reference is 85 dB, with 20 dB of headroom, which would mean 105 dB capability for the mains and using Paul's advice of 3-6 dB additional capacity on the subs, it would be something like 108-111 dB.

          Does this sound reasonable?
          Sounds reasonable.

          Here are some old threads testing subwoofer outputs and their distortions.
          It should give you a good idea of what it takes to put out 108-111dB
          http://www.hometheatershack.com/foru...ests-archived/

          An example of the extreme end for most of us is a TC18" LMS 5400 with a pair of 18" PRs
          http://www.hometheatershack.com/foru...king-200l.html

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          • #6
            Re: How Many dB for Subs?

            Thanks, guys.
            Tony, I'm on my way to check the links you provided.

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            • #7
              Re: How Many dB for Subs?

              Originally posted by Tony G View Post

              An example of the extreme end for most of us is a TC18" LMS 5400 with a pair of 18" PRs
              http://www.hometheatershack.com/foru...king-200l.html
              That's actually pretty tame compared to my THT and Tom Danley's DTS-10, both of which have been extensively covered at
              http://www.avsforum.com/avs-vb/forumdisplay.php?f=155

              They both will do +120dB to 20 Hz, and the real HT nuts aren't satisfied with that. You need to do that to 10Hz to really impress them.
              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

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              • #8
                Re: How Many dB for Subs?

                i've always read that 115 db at the LP is the "official" reference for subs. i believe whichever specs say that the mains/surrounds need to each be capable of 105 db at LP, also say that there is an extra 10 db available for LFE. but, while reference may be a nice straight-forward goal to shoot for, it doesn't necessarily match up with a persons needs (sometimes more, sometimes less). for instance, in my theater i usually watch movies at about 10 db below reference (which is still quite loud to me and everyone i watch movies with). so when i build sub(s) all i need to design for is ~105 db down to 20hz or lower, in room. i emphasize "need" though, because that assumes that i don't want to build in any headroom, which would decrease distortion and bring less overall stress on the system. that's the key to the people bill is referring to (who do very much exist). if they were utilizing the full capability of their subs (assuming they've calibrated correctly and they're not running their subs hotter than fire), they'd have to be watching movies at levels so far above reference that the overall experience would be painful even with the best equipment in the best sounding room... which i very seriously doubt they're doing. but if their subs are capable of 120 db or more, that means the drivers and amps are just loafing along as clean as can be when playing at levels like 105 - 110 db, which coincides with an overall volume that you might actually be listening at.

                so, i guess long story short, my advice when it comes to overall sub output is: establish needs, decide on headroom, build sub. for me, that ends up being a total of 110 - 115 db. like everything else, YMMV.

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                • #9
                  Re: How Many dB for Subs?

                  Originally posted by PassingInterest View Post
                  What do you shoot for in your Home Theater designs, concerning dB capability on your subs?
                  1db more then I need. I know it sounds flippant, but as long as it's capable of satisfying you, forget what the 'experts' have to say. Bill's post is a great example, do you need 120db @10HZ? I sure wouldn't want to be in your house at the time. (nor would I want to repair your drywall)

                  You want a number, 105db. That is loud.

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                  • #10
                    Re: How Many dB for Subs?

                    If you are married and the HT is your living room, you don't need that much power at all, at least if you watch movies with your wife. Now if it's in your man cave.....lots!

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                    • #11
                      Re: How Many dB for Subs?

                      Wow, thanks for all the great answers, guys! All valid points.

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                      • #12
                        Re: How Many dB for Subs?

                        There appears to be focus on a top SPL number, but the quality of reproduction ( ie distortion products ) is a consideration.
                        http://www.avsforum.com/avs-vb/showt...7#post18402057
                        "Not a Speaker Designer - Not even on the Internet"
                        “Pride is your greatest enemy, humility is your greatest friend.”
                        "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                        Comment


                        • #13
                          Re: How Many dB for Subs?

                          Originally posted by Sydney View Post
                          There appears to be focus on a top SPL number, but the quality of reproduction ( ie distortion products ) is a consideration.
                          http://www.avsforum.com/avs-vb/showt...7#post18402057
                          What I like about the links I gave earlier, is that they do the harmonic distortion measurements (vs freq and at various sps levels).

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