What are you guys using to calculate the final Q of a box?

Discussion in 'Archived Threads 2001-2004' started by Scott Parker, Jan 29, 2003.

  1. Scott Parker

    Scott Parker Agent

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    I've been using Lspcad but I don't think it can calculate the Q of a box. I've been thinking about the optimum height for my 24" diameter sonotube with my AV-15. What height would give me a Q of 0.5. I'm going for tight, accurate bass, and I think that's what you guys were recommending. I've got a sloppy EBS tempest which I've tried stuffing with no success, so I figured all try again. This time I'll brace the top and bottom endcaps.
     
  2. Pete Mazz

    Pete Mazz Supporting Actor

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    Winspeakerz gives me 9.5 cu.ft. for a .5Q box.

    Pete
     
  3. Scott Parker

    Scott Parker Agent

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    Thanx Pete, so I guess we're talking about 3'. I was hoping I could get away with 2' but I want the tightest sound possible, so that'll have to work.
     
  4. Tim Morton

    Tim Morton Stunt Coordinator

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    you should run the same formula to try and get to a .7 and see if it gives you the 2' that you are looking for, or better yet have him run the numbers and plug in the 2' box to find the Q at that size...
     
  5. Scott Parker

    Scott Parker Agent

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    I finally realized that the bigger the enclosure the lower the Q. So theoretically if I plug the port on my 320L tempest I should have a Q around .5, cause Adire says for a Q of .577 use 230L. Therefore I should have a very tight sub, but its been boomy ever since I built it. I've gotten my response, with corrected SPL ratings, within +/-6 db's trying different placements, etc. Is there anything I can do to make this sub perform better? I think I have a minor air leak where the terminal connects to the MDF, could this cause a problem?
     
  6. Scott Parker

    Scott Parker Agent

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    Okay, I downloaded the WinIsdPro version and I found out that it can calculate the Qtc of a sealed enclosure. So I put the AV-15 parameters in and it looks like I only need a 115 Liter enclosure to get a Qtc of .571 which is what Adire recommends. Just to clarify, 115 liters do calculate to .115 m^3 right? How many liters does Winspeakerz say I need to achieve a Qtc of .571? Thanks in advance Pete [​IMG]
     
  7. Pete Mazz

    Pete Mazz Supporting Actor

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  8. Peter_A_M

    Peter_A_M Stunt Coordinator

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    Pete,

    Why would you have to deduct the volume displaced by the stuffing if the stuffing itself makes the box think it's getting bigger, not smaller?

    Scott,

    For what it's worth, my version of WinISD Pro (alpha) predicts a 186 L enclosure for a .571 Q; the equation at Loudspeaker101.com predicts a 162 L enclosure.
     
  9. Pete Mazz

    Pete Mazz Supporting Actor

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    The sims usually give you net volume. This means you'd need to deduct for the apparant volume increase the stuffing provides.

    For your example:

    .57Q = 5.7 ft^3 net.

    5.7 / 1.25 = 4.5 ft^3 internal volume, stuffed.

    Pete
     
  10. Peter_A_M

    Peter_A_M Stunt Coordinator

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    Ah, I'm catching on. Thanks Pete.
     
  11. Scott Parker

    Scott Parker Agent

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    Thanks guys, I figured out my problem I was putting in .339 for the Qes when it was supposed to be .399. Now I'm getting the same as you Peter, 186L with WinIsdPro(alpha). Although it does seem kinda funny that the Qes value would matter cause Loudspeakers101 doesn't include that value in the calcuation. Any thoughts on what I can do to fix my sub. I tested for any air leakage last night but couldn't find any. One thing I did notice is that it doesn't come close to passing the knuckle wrap test, as probably most sonotubes this size don't. I was playing a 20hz tone last night at about 95db and I did notice the whole thing was vibrating (not audibly though) a good bit, of course everything else in the room was too [​IMG]

    I used a sonotube calculator and it looks I'll be right at 2' figuring in the plug depths and stuff. So it looks like a guessed right, cool.
     

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