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Help with DIY cabinet tuning...I know, I'm sorry... ;)

Discussion in 'Amps and Cabs [BG]' started by blastjv, Jan 3, 2013.

  1. blastjv


    Jan 8, 2010
    Philly Area

    I was hoping some of you would be willing to help me figure out a few things. I'm looking to build a 215 to replace my Ampeg 810, mainly to save on weight, and I figured I'll actually be able to sell the 810 and make a profit, so that's nice.

    Here are my proposed specs:

    - 48"x26"x16" exterior dimensions
    - (2) Faital Pro 15PR400 speakers

    I was planning to use plastic tube ports. The face of the cab is large enough to accomodate pretty much whatever configuration would be optimal, but I was thinking (4) 4" ports along the bottom would work, but need help figuring out the length of each port tube.

    Other relevant info:

    We play LOUD, aggressive metal (here's a sample: http://swarmofarrows.bandcamp.com/track/the-sky-will-save-us-all ). I push my Ampeg SVT-VR hard enough to get some good grind out of it. We often play with vocal-only PA support, a heavy-handed drummer and two full guitar stacks. I do love the tone through my current 810 (upgraded with (8) Eminence B810 Legends), but I would love some more thick, non-farty bottom end. We usually play in Drop C, and sometimes Drop A#. I guess I'd like the cab tuned as low as is practical.

    Talk to me. What do you recommend?


  2. will33


    May 22, 2006
    Are you using any modeling software like WinISD or any similair sort of box/port calculator? If not, you should be, that will answer your questions.

    Also, that's a pretty big box. I take it you are just thinking of an 810 size box? Those Faitals are quite nice drivers and don't need all that large a box to perform well. Putting them in an oversize box in an effort to reach really deep will limit their excursion capability in the lows. Anything with a -3db point in the low 50's on the model will already sound quite deep.
  3. I would take a look at the TL606 plans. Convert them to 1/2" and add bracing. two 4 Ohm 115's might give you more options with your VR.
  4. blastjv


    Jan 8, 2010
    Philly Area
    No, I have no software. I hoped it would be a simple thing for someone on here with the software to work out (if they don't mind). Yeah, I want the cab to be an 810-sized cab, but I can make it slightly less deep if that helps anything (I'd say 14" would be the minimum, but prefer more like 15" for a more stable footprint).

    Thanks for everyone's input so far,

  5. Two TL606's on their sides would be stable for what you are doing.
  6. will33


    May 22, 2006
    A pair of TL's is a good fit, or, if you want to keep it a single 215, I'd use your footprint and shrink it to somewhere 38-40" tall.

    Search "WinISD Alpha Pro". It's free box modeling software, there is a link somewhere up in the Stickies. Use that to juggle your tradeoffs between LF extension and real world power handling. It's good stuff to know if you're not just cloning an already existing design.
  7. Probably the same Faitals as JohnK's starliner. That is a monster.
  8. In case you didn't know, fundamentals are for the birds. Get the 2nd harmonic working and you will have all the lows without wasting performance.
  9. I don't think JK plays 5 string but it gives you an idea of the cab size and porting these new drivers get away with.

    Look into f-deck hpf also. It will let you slam on your bass with no fear of shoving your fancy cones out of the cab with infrasonic A# etc. You may be able to tune ~55hz strong, I don't know, with a really big cab. The fundamentals below your tuning will play merry hell with the excursion if you don't have the hpf.

    Earplugs eh.
  10. blastjv


    Jan 8, 2010
    Philly Area
    I downloaded WinISD and my head is spinning...

    I TRULY do appreciate everyone's input so far, and so I don't mean to sound like an ingrate, but what I'm hoping for is an answer like this:

    "In order to have a strong bass response from a 48"x26"x16" cab with (2) 15PR400's you should have X number of ports Y inches in diameter and Z inches long."

    I'm not trying to replicate the fundamental of a low A# (I know that's a losing battle). I just want a cab that sounds great. I'm considering just making it a sealed cab, since I'm coming from a sealed 810 anyway, and since JohnK (I have read his great Starliner thread) seemed to like that cab sealed, too...

  11. You would give up a lot of performance in a sealed version. If you play about with winISD for long enough it starts to gel. One would hope the latest version has the new drivers' specs already loaded. How far did you get?
  12. I plugged the plans I sent the op into winisd. With a 6" shelf and the center port plugged it should be just about right.
  13. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    Separating each speaker in its own compartment and having a set of 4 ports for each section.

    So 4x3" ports for each section would keep the port velocity more ideal and lower than using 2 4" ports per section, and also give you smaller openings and longer tubes. Making a much more accurate port. Since your cabinet is so wide you have plenty of room to place 4 ports symmetrical around each driver. So 2 ports on both sides of the speakers.

    The Acoustic 406 wide and the 406 narrow is a good designs dimension wise to lighten and modify for round ports instead of the center slot port.

    "chuffing" is when you dont have enough port area, or pretty much have to small of ports. That is what you need to worry about. So its common to use large 4" ports. But larger ports will have larger openings and shorter length which allows much more out of phase content to be heard. So using smaller openings with longer lengths will help improve this, you just need to use 4x3" ports instead of 2 x 4" ports. and that is per driver not for the whole cab. And 4 x3" ports will actually have lower velocity than 2 4" ports.

    Its slightly more ideal to keep port tuning at E 41hz fundamental or slightly lower. so hopefully the resonant frequency of the driver allows you do do this. tuning is recommended to be 5 to 7hz above or below resonant frequency (Fs) of the driver.
    In this case the Fs of the faitals is 35hz so tuning to 40hz will keep it slightly below 41hz fundamental.

    you could also tune to the Fs of the driver at 35hz and even 5hz below it at 30hz. this will keep the smearing and inaccuracy of a reflex cabinet as far away from the fundamental of the lowest note on a standard bass guitar. and within a reasonably amount of a low B at around 30hz

    as far as I can tell if you do use individual compartments with the size cabinet you plan on building. Volume for each section will vary between 4.3 to 4.7 cubic feet. If you do use 4x3" round ports per section. Then the shortest length of 9" will give you a tune around 42 hz within those volumes and the longest length of 15 inches will get you around 32hz. So using more and longer ports again gives you more playing room. The length can vary 4 to 5 inches and you will still be in ideal tuning. 9" being the min and 15" being max.

    Attached Files:

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