1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
     
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Building a ported 1x15 cabinet

Discussion in 'Amps and Cabs [BG]' started by dubhnight, Jul 26, 2012.


  1. dubhnight

    dubhnight

    Jul 26, 2012
    Hi, this is my first post here, although I've been looking around for a good while now. Anyway, what I'm trying to do is build a cabinet for an Eminence Legend CA154 that I happen to have, and I've run into a few problems at the design stage. Mostly, I find WinISD to be somewhat confusing, and am having trouble coming up with a cabinet design that is within reasonable size limits without loosing too much sound quality. I have built speakers before a few times, my first being a very large set of transmission lines and recently a 1x12 guitar cabinet, which turned out pretty well. I don't, however, have any experience in building a bass cabinet, and I gather that it's much more reliant on theory.
    If anyone could lend me a hand in coming up with dimensions and port sizes for this cabinet, I would be very pleased. I'm going more for loudness than depth of bass, as I play a 4 string in standard tuning, but would like to get the most out of the 15" speaker. The only real parameter I would like to ensure is a 75cm width, as this is the width of my head unit. Thanks in advance.
    Also, here are the speaker parameters: www.eminence.com/pdf/Legend_CA154.pdf
     
  2. Passinwind

    Passinwind I am Passinwind and some of you are not. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Have you looked at the designs Eminence themselves suggest?
     
  3. Blues Bass 2

    Blues Bass 2 Supporting Member

    Oct 3, 2001
    Davenport Iowa
    Here are the Eminence designs .

    http://www.parts-express.com/pedocs/more-info/290-466-eminence-legend-ca154-more-info.pdf

    The medium cab looks like it might be a good choice .

    V is volume before adding the speaker , ports and bracing so about 4 cubic feet would be right . Just figure out how wide and tall you want it and then calculate how deep the inside needs to be to get that . It shows two 4" inside diameter ports at about 6.5" long . I've used the Eminence PDF for the CB158 and it came out great , these are very handy .
     
  4. dubhnight

    dubhnight

    Jul 26, 2012
    Actually, I hadn't realised they offered such detailed specifications. Just looking at them though, they seem so far from what WinISD said would be optimal, that I was wondering if these would actually be good designs to use, or would there be something much better if I didn't have to worry so much about size.
     
  5. Passinwind

    Passinwind I am Passinwind and some of you are not. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    WinISD does not actually automatically offer optimal designs, it's up to you to decide what compromises will work best for your situation and tweak various parameters to get there. Not worrying about size removes a whole series of compromises, for sure...;)
     
  6. mulchor

    mulchor

    Apr 21, 2010
    St Pete, FL
    Straight from the horse's mouth (eminence.com)

    Type: Vented Box
    Shape: Prism, square
    --Box Parameters--
    Vb = 5.666 cu.ft
    V(total) = 5.933 cu.ft
    Fb = 39.68 Hz
    QL = 7
    F3 = 45.71 Hz
    Fill = normal
    --Vents--
    No. of Vents = 2
    Vent shape = round
    Vent ends = one flush
    Dv = 4 in
    Lv = 2.848 in

    I wonder if they have a metric version of their website :meh:

    Anywho, you have the specs, 5.93 cu ft internal volume with 2 4" diameter ports. Set in the width 75 cm, and work out the rest.

    75 x 60 x 38 seems close depending if you'll have bracing or not

    Edit: the ports call for 4" diameter (10.16 cm) -- you can go rectangular instead of round if that' easier for you, surface area with eminence specs is 81 sq cm x 72 mm long
     
  7. will33

    will33

    May 22, 2006
    austin,tx
    You don't need anywhere near the 5.93,cu.ft. That's almost big enough for 2 of them if you don't need the sub lowend.

    OP, more power/output from an electric bass is at the 1st overtone than the fundamental. You need some lows to keep it from sounding thin/weak, but not nearly as much as some think.

    I find working things out so the model shows a -3db point somewhere in the low to mid 50's makes for a plenty deep sounding bass cab, and works well for a lowB/5-string should you get one someday. It also increases the real world power handling of your speaker when it doesn't have to try to reproduce the way deep, 30-40hz stuff.

    As an example, my little diy rig models out to have an f3 (-3db point) around 50-52hz. It does just fine with most any bass and when I go to rebuild it, I may shrink it a little more and move that f3 up to about 55hz. Basically, if your model shows you with a db or 2 of even at 60hz, it's a good sounding bass cab, IMO. Sounds plenty deep but doesn't have cones flapping around trying to be subwoofers.

    Watch you don't tune the box too high either. It loses control of the cones below the tuning frequency. I don't like to get much above 50hz for that reason.

    All IMO/IME there. You're going to have to come up with your own set of compromises. There is no 1 right way.

    This thread has good info about what our basses are really expecting our speakers to do.

    http://www.talkbass.com/forum/f15/bass-frequency-waterfall-plots-what-they-mean-rigs-510749/
     
  8. dubhnight

    dubhnight

    Jul 26, 2012
    Thanks guys, this has genuinely been really helpful. Learned more here than in 2 weeks of lurking.
     
  9. mulchor

    mulchor

    Apr 21, 2010
    St Pete, FL
    The Vb came from Eminence, selected for a particular tuning (the freqs given in the post above).

    The OP is looking for a box that's fairly wide to fit the amp, so making it still wider than it is tall or deep, I think the dimensions look ok. Any more than 5:4 width/height ratio is gonna look fat and squatty. If you shrink the volume to just a couple of inches of clearance around your speaker for height and depth, you *can* get a high-tuned box, but you don't want your driver butted up against the back of the enclosure. My approach given the desired width would be let's make the box big enough to look good and get the F3 low as a side-effect, is why I suggest the first Eminence suggested box.

    We don't even know what head this is going with. hmm...

    Lots of choices exist, but it doesn't need to involve guess-n-hope.

    Has anyone used the Eminence software?
    http://www.eminence.com/support/designing-enclosures/

    Did a quick calculation, and going with 75 x 50 x 30 would give ~4.0 ft^3, for F3 ~56 Hz. I'm afraid any shorter or shallower won't fit well. Fortunately there's lot of rooms laterally for the ports.
     
  10. will33

    will33

    May 22, 2006
    austin,tx
    All true.

    Just IMO, a lot of eminences biggest box designs for low extension come in a little bigger and a little deeper response than is really needed for a practical bass cab. The 4cu.ft. sounds about right. If he's building wide for a certain look, he'll have ample internal volume just to make everything fit.
     
  11. I keep seeing this over and again.

    The chart below is my analysis of a Fender MIM-P with DiMarzio DP146 in parallel.
    The sample is direct-in with a four second period.
    The string is a round wound, low E picked.

    Link to Low-E FFT
     
  12. will33

    will33

    May 22, 2006
    austin,tx
    Whoa.....how did that end up so much different than the waterfall plots I linked to? Of course different pickups and where they're placed under the strings will throw different balances of harmonics, but, when I run my P-bass through a mixer channel strip set even, I'm not hearing, or maybe percieving, that much bottom. That could be speakers or headphones that can't reproduce it as loud as the rest. It's entirely possible it's my ears playing tricks on me too.

    This is interesting. Got measurements of any other basses?

    I still don't like all that subwoofer bottom in my sound, but, my speakers also aren't pistoning like I think they would be with that much content down there. Even with amps that aren't filtered high.

    Mine is an MIM P, nickel roundwounds.
     
  13. mulchor

    mulchor

    Apr 21, 2010
    St Pete, FL
    Unfiltered, it has to fall off from the fundamental, whether it's a vibrating string, a tuning fork, or whatever.

    There are, of course, lots of filters between the instrument's string and your ears.
    And your ears are famously non-flat filters, themselves.
     
  14. Passinwind

    Passinwind I am Passinwind and some of you are not. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    That was all hashed through in that thread, with litle agreement or resolution. IMHO it's not nearly as simple as greenboy or Bruce or anyone else seems to want to make it. ;)
     
  15. will33

    will33

    May 22, 2006
    austin,tx
    Yeah, I don't have a big enough ego to think I have golden ears or anything. Was just surprised to see that compared to what I hear. Pretty sure string scale length has a lot to do with it as well. Why uprights sound so much deeper playing the same note.

    I don't mind being corrected or learning something new today.:smug:
     
  16. will33

    will33

    May 22, 2006
    austin,tx
    May have to read through that thread again then.
     
  17. Passinwind

    Passinwind I am Passinwind and some of you are not. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    I'd suggest that anyone interested do their own recording, analysis, and especially careful post-processing to remove just the fundamental, then decide how much it does or doesn't matter to you. You may notice that even though I posted a lot in that thread, I never really offered any opinions one way or the other.;)
     
  18. zenman

    zenman

    Jan 30, 2008
    St. Paul, MN
    75 cm seems pretty wide for a head. What are you running?
     
  19. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    I would imagine that right-hand position has an influence on how much fundamental and harmonics are present.
    If the string is struck closer to the 12th fret more fundamental is present.
    ...just a hunch.
     
  20. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I'm with you on that!
     

Share This Page