Sub construction: Okay - could y'all dumb it down a little?

Discussion in 'Archived Threads 2001-2004' started by Chuck Bogie, Jan 29, 2003.

  1. Chuck Bogie

    Chuck Bogie Second Unit

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    I understand that one has to buy a "good" speaker to start with... But then you add into the factor enclosure size, port size, how long you make the port inside the box, the *&%(*&^ shape of the port, where the port is located, and all that other fun stuff... This seems to affect something that folks call a "tuning point?" Can one take a sub speaker and effectively lower a tuning point, but the sub won't have the sound output that a higher tuning point would have?
     
  2. you can lower the running of any ported enclosure simply by elongating the port. When you do this, you end up with lower bass extension, but will trade off spl a little higher up above tunning. (that is the simple exlaination...i hope)

    most "bestbuys/circuit city" type comercial subs have a high tunning point that does gives an artificial bump. if you were to lower the tunning on these subs, you would have less "appearent" output, but they will extend lower. There are other side effects too, but then it starts to get more complicated.
     
  3. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Chuck,

    Everything in DIY (or in life, for that matter [​IMG] - separate thread for "After Hours") is a trade-off. Yes, with a decent Home Theater driver, generally, you can lower the tuning point to get more output down low, but you lose some output up higher. Also, you can tune higher for more output there, but, in a vented box, you quickly lose output below the tuning point, plus, with out a subsonic filter, you run the risk of the driver unloading.

    My suggestion would be for you to download WinISD or LspCAD and see exactly what the trade-offs are based on their models. Also, check out Andrew Low's website for some additional help. He has a LspCAD tutorial on there that I found helpful.

    JKS
     
  4. Chuck Bogie

    Chuck Bogie Second Unit

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    So, if I'm not worried about blowing the doors off, I can drop the overall frequency response down pretty low? About the loudest I've run my HT system is -15 (Denon 1803, Infinity Entra Twos, Entra center, and Studio Monitor 120s in the back).
     
  5. Tim Morton

    Tim Morton Stunt Coordinator

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    Generally speaking it might be best the first time out of the gate to build a sealed box. Then everything is controlled by only one factor...size of the box. You have room for error, and ( I might get beat down for this), but....lets say you biu a driver from madisound...they will give you the proper box size and the T/S specs and you can run your own formula from equations easily found on the net, but lets say madisound tells you that the optimum sealed box for driver "A" is 3.3 cu.ft...well if you build a well braced and truly SEALED box plus follow the recommended stuffing , your sub will sound "just about the same" in normal listening if you build it anywahere between 2.75( add a little extra stuffing) and 4.0(maybe remove a little stuffing)...but if it is braced and sealed it will sound good...not do the same thing with a ported box and all bets are off...you NEED to be accurate as can be when calculating box size and port length to achive great sound and possibly prevent ruining the driver. Will a ported sub sound better? Hard to say, there are people in both camps that swear by one or the other.
     
  6. Chuck Bogie

    Chuck Bogie Second Unit

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    What happens if you build a sealed box too large? Or too small?

    I mean, heck, I'll be spending $120 on an amp, and probably another $100 or so on the speaker... May as well get it to where I'll be happy with it...
     
  7. Andrus_R

    Andrus_R Stunt Coordinator

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    Or just forget everything and just follow the manufacturer's plan to a Tee. Adire gives out plans for their sub drivers for free. You can go either sealed or vented. Glue up a big square MDF box in a day or two. Easy enough.

    Why mess with it when they've done all the messing around 4 ya...[​IMG]
     
  8. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Well, yes, but at some point, you begin to lose the advantages that a vented enclosure provide. For most drivers, if you tune to lower than, say, 12-14 Hz, it might as well be sealed.
     

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