How loud does a sub need to be

Discussion in 'Archived Threads 2001-2004' started by Mark_E_Smith, Aug 31, 2002.

  1. Mark_E_Smith

    Mark_E_Smith Second Unit

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    If I listen to my system mostly at a max of 96 dB 3 meters from my speakers and my system is capable of 108 in the same position what should I target my sub to acheive? This is for both HT and music.
     
  2. Chris Carswell

    Chris Carswell Supporting Actor

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    LOUD MAN!!! PLAY IT LOUD!!! [​IMG]
    I remember reading somewhere (maybe Dolby or the THX page) that the sub is usually dialed in a few db higher than the main speakers. I forget the exact #'s though. I'll try to find it & get back with you.
    What's up Mark? How are things? Start building your sub yet or those mains with your killer ribbon tweeters?
     
  3. Mark_E_Smith

    Mark_E_Smith Second Unit

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    After rethinking the Tumult I might go that way, dont know yet. The Maelstrom with the LT will have about 108 dB max and I am flat to about 22 Hz. The Tumult with more power can go louder, alot, but I dont know if I really need it. I still want to focus on SQ which is why I am going LT instead of a ported or PR design, that would be easy to get loud but at the expense of tight bass, I really hate muddy bass. As far as the mains go maybe next year, I am pretty happy with what I have now. Redoing the mains is a loooong term project. Which will be accelerated if the surrounds go(they are 20 years old and fell kinda crispy) in the main speakers. I might use the Chinese made Ravens instead. They look real good. What I plan to do first is to measure the Heils and see what they really can do. To do that I need some more practice with the Clio as reflections can give you fits trying to see what you really have.

    Anyway the question is do I need a sub that will play louder than 108 dB if 99.9% of my listening is below 100 dB.
     
  4. Jack Gilvey

    Jack Gilvey Producer

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  5. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Jack, what do you look for in spl out of your sub(s) does the sub need to be allot louder than the rest of the system? I know this is probably VERY subjective but I have really no guide to start from though Im pretty sure I don't need 120 dB of spl at 20 Hz from my sub. (my wife squeaks when it rattles the house now) I have L of R but have not played it very loud yet. At lower volumes my M&K sub(75 watt) sounds real good. Though I think it has a limiter circuit in the amp as it will not bottom, the amp just starts clipping. I haven't used the rta in the Clio to see whats going on as I haven't had a free weekend to play with it.
    Also what would one do or not do to design a sub to sound muddy? Is it the group delay, port noise, box size, air leaks etc?
     
  6. Brian Bunge

    Brian Bunge Producer

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    Mark,

    I've heard some 111dB peaks watching the "Coming Mother" scene from The Haunting. I don't know exactly what frequency that peak is and I measured it with a Rat Shack meter but I imagine I could safely add 2-3dB to that number for a real world value. One thing's for sure, it's addictive!

    Brian
     
  7. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Yes thats another reason I'm considering the Tumult[​IMG] More power more fans[​IMG]
     
  8. Greg Monfort

    Greg Monfort Supporting Actor

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    Well, since your system is capable of meeting the 105dB peak/listening position DD reference then it seems reasonable to me to have a sub that can do DD's 115dB peak/20Hz/listening position also.
    Since we don't know how much room gain there is or whether its acoustics follows the 6dB roll off in the LF, a worst case scenario is:
    20log(3/1) = ~9.5dB + 115 = ~124dB/m/rated power. Chances are pretty good though that ~120dB will be sufficient, but better to have additional headroom than be caught short.
    WRT peaks, my RTA has a peak capture feature and has shown up to +20dB centered at 40Hz and +12dB centered at 25Hz on many of the movies I've recently rented, so they're serious about using the DD spec limit down pretty low. There was one movie (I've already forgotten) that was pretty mundane until the music during the credits. It had a high gain ~30Hz undertone that was sustained for the entire song track and you could hear my four cinema sound 15"ers flatten out as the VCs went into thermal overload, like when I play organ music that includes sustained 16-32Hz organ notes.
    My kind of soundtrack! [​IMG]
    GM
     
  9. Pete Mazz

    Pete Mazz Supporting Actor

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    For movies, Dolby specs reference at 105 dB for speakers and 115 for LFE, at the seats, I believe. Add a few more dB that the sub has to handle if all speakers are set to small. Not many folks listen at reference, however, so 10-15 dB less is probably more like it. So that still leaves ~100 dB for the LFE channel at the seats. If you sit 3 M away, figure ~109 dB.
    Pete
    Edit: Greg got here first. [​IMG]
     
  10. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Greg and Pete thanks thats kinda what I was looking for. I have noticed alot of people refer to reference, wht is this or could you point me in a direction to read up on it?
     
  11. Pete Mazz

    Pete Mazz Supporting Actor

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  12. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Thanks Pete and Greg you guys are great. Dolby is bookmarked[​IMG]
     
  13. Greg Monfort

    Greg Monfort Supporting Actor

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    >Add a few more dB that the sub has to handle if all speakers are set to small.
    ====
    It's actually 10*log(5) = ~7dB for DD 5.1. I forgot to factor this in, so in theory up to ~131dB/m/rated power is needed, though this would have to be a large room with no gain down to 20Hz, or >28ft long.

    Anyway, this is strictly to keep transients from clipping, and that due to the way SPL sums, even if all channels are peaking at the DD reference 105dB/122dB/listening position, then the total peak amplitude is only ~113.2dB plus any room gains due to reflections. During scenes with LF 'rumble', the one's I've measured are ~10dB less, so as loud as it is, it's not nearly as loud as the build numbers imply.

    GM
     
  14. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Reading on the Dolby site, is reference 85 dB with 105 dB peak for main speakers and additional 10 dB for the LFE?
     
  15. Greg Monfort

    Greg Monfort Supporting Actor

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    Right, just like Pete said. [​IMG]
    GM
     
  16. Mark_E_Smith

    Mark_E_Smith Second Unit

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    It seems I have backed into this question. Any recomendations on website(got dolby's) or books for HT set up and calibration? :b
     
  17. Greg Monfort

    Greg Monfort Supporting Actor

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  18. Mark_E_Smith

    Mark_E_Smith Second Unit

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    My manual (Onkyo TX-DS-787)is poor at best, thanks for the tip I think I over looked this article because I thought it was for pro studios(it is but it still applies to HT) any way out comes the RS spl meter for some samples. Thanks for your patients I'm on a learning curve here. [​IMG]
     
  19. Chris Carswell

    Chris Carswell Supporting Actor

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    Mark,
    If you need some test material LMK. I will make you a good cd with pink noise (I think that's what it's called), composite tones, fast & slow sweeps 20 HZ to 20,000 HZ, and my favorite sine waves 10 HZ to 90 HZ in 1 HZ increments (got to test that sub down low you know). I could make it 5 HZ increments if you like......... [​IMG]
     
  20. Mark_E_Smith

    Mark_E_Smith Second Unit

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    The Clio system has a good amount of tones, white noise pink, green [​IMG] . The tones are spaced by octave fractions 1/3,1/6,1/12,...to 1/48 the more I play with it the more Im impressed, Im just behind the curve on how to use it. I did use the RS spl meter real quick to do a set up using the test tone in the receiver, sounds much better now that I know how to use it. The sub I have, as I suspected is all done at 94 dB and does have some kind of limiter in the amp as it just stops at 94 dB no destortion no bottoming just not louder so looks like Im going to need the new sub, thats the next project. Now Im leaning to the Maelstrom again as I can get 108 dB with no room gain and a PE plate amp. Hows your speaker project coming?
     

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