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Stuffed a 3015LF in a Peavey 115BW, need bigger port?

Discussion in 'Amps and Cabs [BG]' started by Ender_rpm, Dec 6, 2011.


  1. Ender_rpm

    Ender_rpm

    Apr 18, 2004
    St. Louis MO
    [​IMG]

    This is the same model cab. I lined it with 1 1/2" mattress padding, and it sounds MUCH better, but still seems like it get's "choked" on some lower notes. It has a simple 4" circular port in the front baffle, internal dimensions 25" tall, 22.5" wide, 9.75" deep. Would enlarging the port "open up" the sound? Or is it just a function of using a cab closer to the small end of the drivers range? (~3.15 Cu FT). I'm going for a strong almost reggae/dub thickness in the lows, FWIW.
     
  2. will33

    will33

    May 22, 2006
    austin,tx
    Likely a function of the smallish cab but it still needs at least one more 4" port. It won't "open up" the sound but it will allow you to send it more power and/or dial in a little boost to fatten up the lowend without getting the chuffing noises that come from not having enough port area.
     
  3. Ender_rpm

    Ender_rpm

    Apr 18, 2004
    St. Louis MO
    CAn you have TOO BIG a port? How would you know?
     
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    +1, the 3015LF needs at least two 4" ports. But the ducts must be three times as long to maintain the same box tuning.
    Yes.
    That's what cabinet modeling software is for.
     
  5. Ender_rpm

    Ender_rpm

    Apr 18, 2004
    St. Louis MO
    1. Ports- Ok, so drill another 4" hole in the baffle, but they need tubes? If the baffle is 3/4", I would need 2 1/4" tubes?

    2. Got it

    3. So you're saying the difference is not audible? Or that it only matters to a computer?

    ;)

    Seriously, I've DLed WinISD, and I just don't care to learn it.
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The alternative is formulas as long as your arm and endless calculations, typically done on a slide rule. :D
     
  7. Ender_rpm

    Ender_rpm

    Apr 18, 2004
    St. Louis MO
    Or you could just tell me.....

    :)
     
  8. You all don't sit around and talk wave guides with friends? :D
     
  9. Ok, according to BassBox 6 Pro you need another 4in (that is 2!) port and make both of them 13.42 in long. This is to avoid chuff and allow you to actually use the 450 RMS and keep the cone loaded down to 30hz before you reach xmax. Peak acoustic power with 450watts is predicted to be 123db, and that is all the way down to the tuning freq of approx 38hz. Even with 600 watts it stays loaded, but port noise will prevent it from cleanly taking any more. Models pretty well in that enclosure actually.
     
  10. "it get's "choked" on some lower notes"
    I don't know the exact meaning of this expression (non native English speaker), but I'd say a couple of things:

    • You need more port area with the 3015LF (agree with all).
    • You cannot notice you need extra port area unless at high power levels. Below you cannot hear any chuffing, then you'll hear no difference.
    • Peavey BW are less capable for lows, but they are good as full range speakers. 3015LF is poor for mid frequencies in comparison. I suspect the "chokeness" could be due to this difference in response above 1.5 kHz.

      If you plan to run your cab full range I think the 3015 "non LF" could be better for you. Still a huge improvement in lows, but your mids will be comparable to the older BW and you gain a small bit in efficiency.
     
  11. will33

    will33

    May 22, 2006
    austin,tx
    I don't think those boxes are deep enough for that. You'd need a minimum of a port diameters clearance between the end of the tube and the back wall. Likely getting into the point of no return trying to tune a small box low. Remember you have to take the port tube out of the net internal volume then recalculate.

    That thing might work tuned in the low 40's, meaning a little shorter tubes. OP, measure the internal depth (front to back) of the box, then subtract 4". That's the longest tubes you should put in there without an elbow in them. How long is that?
     
  12. rpsands

    rpsands

    Jul 6, 2007
    Phoenix, AZ
    The 3015LF actually behaves quite well in a sealed box, so don't rule that out as an option. Try plugging the port and see if you like it.

    If it doesn't, then I'd suggest filling the port and going with a shelf. Tube ports are really impractical for a 3015LF unless they're flared, and those are quite costly oftentimes.

    Two 4" ports is really the barest of minimums.
     
  13. will33

    will33

    May 22, 2006
    austin,tx
    Good points. I'd be inclined to try it sealed and try it with 2 port tubes as long as the box will allow. That much is quick and easy. If that doesn't get you what you want, it's probably time to just scratch build a proper 3.8-4 cu.ft. box for it.

    Good points from parapentep70 as well. A spikey midrange or just plain lack of midrange is going to greatly affect the percieved tone of the thing as well.
     
  14. Bass Unique

    Bass Unique

    Nov 3, 2011
    Wiltshire
    One thing that has not been discussed is that the port is firing behind the grille. This will increase the chuffing effect. Far better to have the port free of any obstructions (unless the grill is a couple of port diameters in front then you should be ok). There IS a reason why many good cabs dont have the grill in front!

    If you use Win ISD, it gives very little information on ports except peak port velocity at the signal level you add in. It does nothing else to discuss port size. If you want to model ports in more detail you need more sophisticated software.
     
  15. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    WinISD Alpha Pro gives you everything you need to know. You can instantly see the effect of varying the size, shape and number of ports on port velocity.
     
  16. To make the ports much longer than 5"-6" you will have to angle them, but it looks like you would have plenty of room to do that and still clear the speaker basket. Anything from 12"-14" will keep you in the 38-44Hz region. Sealed, you lose quite a bit of low end extension and sensitivity as is to be expected since most modern pro sound drivers are designed around a vented enclosure. BassBox 6 Pro takes into account port volume in the box. You have plenty of air space in your cab for the two 4" ports 13.82" long. I have modeled smaller boxes with a slot vent tuned about the same using the 3015LF. It really does not require a very large box. After your driver, acoustic treatment, and ports you still have close to 3 cuft, which is quite a lot for a modern 15.
     
  17. Would the above changes also benefit the speaker box with the BW speaker?? i have one of those boxes as well

    Thanking you

    Leslie
     
  18. rpsands

    rpsands

    Jul 6, 2007
    Phoenix, AZ
    Probably moreso, IIRC that box is like 5 cubic feet or somethign ridiculous and has a bigger port. Could be misremembering though :)
     
  19. Ender_rpm

    Ender_rpm

    Apr 18, 2004
    St. Louis MO
    Thanks for the input y'all. Took it as is to rehearsal last night and it sounds great. Deep, punchy, prolly not as low as it could go but as low as I need it right now. Running an LM2 into it, seemed to need a lot of power ( master gain both halfway up with a med output jazz, backed off on gain with SB2) but I was pretty hot in the mix last night too :) may still add a second port, but prolly after I redo my 215. Thanks!
     
  20. Its the same one as in the photo at the top of the page...


    Leslie
     

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