Cabinet Building 101

Discussion in 'Amps and Cabs [BG]' started by bizzaro, Jun 23, 2001.

  1. bizzaro


    Aug 21, 2000
    I invested in some speakers and need to build cabs for them. How do I go about designing a box for them that is the correct size etc? Any good web sites on the subject? Or how about a mentor? bgavin? Joris? Mikeyd? I 've got 4 Eminence Pro Twelves. They have 80 oz magnets in them. I want to pair them up to use on each side of the stage when we play out. I would like to design them to tip back monitor style or flat/stack. Should I throw in tweeters? Ported? I have all the specs and parameters etc but don't know how to apply them to building a cabinet. HELP!!!!!
  2. Try here. Use the speaker designer WinISD online or download it. It has Eminence speakers parameters preloaded. Play with it and you'll figure out the best box volume, and whether you want to port it, whatever.

  3. MypartnerStinks


    Jun 19, 2001

    Thats a good place to start.
  4. From the description, these appear to be either Delta Pro or Kappa Pro models. Neither of these are stellar performers for electric bass in the lower ranges between low E and middle E, and both are awful below low E. They appear to be better suited for loud PA or other sound reinforcement above middle E (80 Hz).

    My concern with building cabs for these drivers would be expending a LOT of work and then being dissatisfied with the results. I would strongly suggest you find a source for pre constructed unfinished cabs if you can, such as or others.

    I have all the Eminence drivers worked out in the Perfect Box design program available on my site. It is a DOS program that runs under Windows. Nothing fancy, but it is pretty accurate.
  5. bizzaro


    Aug 21, 2000
    Thanks for your suggestions. I am overwhelmed at this point and have way more questions than answers. Like how to convert liters,(volume), to cubic inches. And the list goes on and on.
  6. caveman


    Nov 19, 2000
  7. Here's something you can use:

    Per speaker, use 2.3 to 3.5 cu.ft, put in a port of 4" diameter, 5" long. Of course, the more volume you use, the more low end response you'll get, but 3.5 cu.ft is rather large.

    The port tuning tracks the response perfectly when changing the internal volume between 2.3 and 3.5 cu.ft, so you won't have to change it in between those ranges.

    Remember, this is PER speaker, so a 2x12 would be twice the number, and have two ports. The speakers can be mounted in the same (twice as big) volume. A tweeter can be added, but has to be crossovered at 4-5 kHz, and will provide only very high frequencies. The 12s themselves will sound pretty bright, judging by the specs.

    Use 3/4 inch plywood for cabinet construction. Brace all panels, especially the front, in between the speakers, or use at least 1 inch thickness for the front. Use gaskets. Put in some recess handles, and put 2-3 inch casters underneath. This thing will be heavy.

    Hope this helps.

    peter-j likes this.
  8. Not really. Increasing the box size by 50% and leaving the port dimensions unchanged varies the tuning frequency from 43 Hz in the small box to 35 Hz in the larger box. This is a tuning variation of 1/3 octave. Will it work anyway? Yes, and you will probably never hear the difference. More important is that your port be tuned at 41 Hz or lower to protect your drivers. Since these Delta Pros are really not suitable for a 5-string bass, there is no reason to tune lower than 41 Hz. The only accurate way to do this is with a digital volt meter and a computer driven signal generator. Anything else is just guessing.

    Adding more volume above that required for the optimum produces a positive hump in the response at the port tuning frequency. For the Delta Pros, this is a good thing, as it improves the low end response. If I were designing for these drivers, each would go into 4.0 cubic feet tuned at 41 Hz. This would produce a usable response for a 4-string bass, and the cost would be large cabinets. Joris' advice about doubling the volume when adding a 2nd driver is 100% accurate.
  9. I just snagged a B25B cab with 2-15's in it. It originally had a kinda small port from the factory, and somewhere along the way someone added (2) 4" ports, just holes, no pipe. I want the original design so I'm gonna fill the 2 holes that were added.

    I tried to figure out what these extra holes would do, and I'm guessing it would tune the box to a higher frequency, given the original speaker specs, and this is not good since the drivers would be unloaded below that?

    Help me out here. Joris the Spider, BgavinMcleod? :D


  10. Please post the cabinet internal dimensions, and the dimensions of each port.
  11. bizzaro


    Aug 21, 2000
    Thanks again to all posts. All sites were very useful and I did use them all. I think I got scared out of using these speakers,(delta pro 12), for cabs. But all the info is a great help as I am going to build cabs someday soon. I need to find the right speakers. I just need to get a little more educated so I can make an intelligent purchase. bgavin-I tried to download your stuff from your site and I can't open it though it seems to have downloaded. And your perfect box info "page is unavailable". If you have a chance to see what is up with it I would love to see your info.
    So---How do you find a speakers that are good for bass cabs. These (delta pro 12),were advertised as good for bass guitar, but if they are weak from middle E down, I would have to emphatically disagree. Is there still hope to use them in a cab?
    I really don't want to drag around cabs larger than our P A cabs. I did find a site with a very specific design but it is old(1993). Is this still a valid design today?? Opinions??
  12. MikeyD


    Sep 9, 2000
    There is a range of philosophies about speaker and cabinet design relative to bass guitar. I'm not too sure that your 12" drivers are *inappropriate*, per se. They may be a little weak on the lowest notes, but (and this is the crux of my point), a very large number of commercial bass cabinets exhibit this same characteristic - probably most famously the Ampeg SVT 8x10 (which, as I recall, is flat down to only about 60 Hz.!). So, does one conclude the SVT shouldn't be used?? Of course not. It's all relative. If you demand an absolutely *flat* response down to 31 Hz. or lower (i.e., a hi-fi cabinet), you will pay for it (size, cost, inefficiency, and/or weight).

    There are some people that are obsessed with flat response out of cabinets. There are others who don't care to hear loud fundamentals, and would rather have a cabinet be loud without pumping 89 kW into it. I fall sort of in the middle. I need some serious fundamentals, but I'm willing to live with a low end that's not quite *flat* if it ensures that I can haul the cabinet up a flight of stairs and power it with something less than my own personal Hoover Dam.

    - Mike
  13. bizzaro


    Aug 21, 2000
    MikeyD,would you use these speakers for a bass cab? Why? Why not? Would 10's that produce a lower fundamental work better? I was going for the "more cone area = more volume" theory. Maybe a pair of 15's with smaller box demands would do it? I am currently playing through a Carvin R600 cyclops. It has 1x15,2x8w/tweeter.I would use this amp to power my new cabs. My goal is to increase my volume cleanly across all frequency's. And I do use a five string.
  14. Let's see, external, 39"x29"x11", so let's say 37"x27x8.5". The original port is rectangular, about 3"x5" with no tubing behind it, and the added ports were both 4" diameter circles, no tubing.

    Hopefully you're gonna tell me to fill them, because I just finished doing it. :D

    I'm also under the impression that driver specs have some effect on all these calculations, I'm using CTS square magnet 15's, probably real similar to an Eminence B-15 except lower power I'm sure.

  15. MikeyD


    Sep 9, 2000
    I don't have the specs of your 12's handy. In general, for a wide response, full-range bass amp, I'd choose a combination of 10's and 15's (which is mainly what I use). If, on the other hand, you wanted a classic, deep, boomy bass, 15's alone would handle it. If you wanted a punchier, jazz-fusion (or modern sound), I'd think some good 10's would be the ticket. I play both styles - and everything between - so I need the best of both worlds. I did consider getting a 2x12 before I bought my 2x15. I ruled it out because (and this is a generalization) I didn't feel that 12's would give me the deep bottom of the 15's, nor the punchiness (midrange) of 10's. IMO, of course.

    Yes, the cone area does often correlate to efficiency (or loudness). You can certainly get a 10"-loaded system that will give a fat bottom, but typically at the expense of efficiency. If you are willing to live with lower efficiency, then 10's can be fine. For the deepest notes, the bigger the drivers used, the better the overall efficiency, in general.

    The downside of bigger drivers (such as 15's) is that the required box volume is bigger. In this sense, 12's offer an advantage. It's the old tradeoff: small size, efficiency, deep low end. Pick any two, because you can't have all three. I also have the R600, and adding cabinets will certainly help, as long as you don't load the amp too low impedance-wise. Carvin's speakers aren't that efficient - and their low end isn't great, either. What you want is the bassist's worst nightmare: loud and low. This is the hardest thing to achieve. I'm running an R1000 into an Eden 2x15 and a Carvin 2x10. The roughly 600 watts going into them makes them fairly loud and low. But if I needed it to be louder, I'd replace the Carvin drivers (or get a more efficient 2x10 or 4x10). If I needed it to be MUCH louder, I'd add a folded horn on the bottom, and run my heads in bridged output.
    - Mike
    peter-j likes this.
  17. Yes. This is Len Moskowitz' design using a Peerless woofer that is still available today from Madisound at Len used a different type of mid-bass / tweeter than my personal choice, but his design works well. This design only varies about 5 db between 31 and 200 Hz. It is very usable for 5-string bass, but isn't very loud. It appears that 112 dB is about tops for this driver. The good part is, they run in 1.5 cubic feet and are easy to cart around. One could use a 2x10 configuration of this driver in 3 cubic feet, and still be able to carry the cabinet.

    The Delta Pro 12s calculate at -20 dB at 31 Hz and -11 dB at 41 Hz, which IMO is pretty useless for a bass driver, especially a 5-string.

    This Delta peforms nearly identical to the JBL E-145 driver. If you feeling like adding some EQ, the Delta and the JBL can both be boosted in the bass end. Use 2.2 cubic feet, tune to 31 Hz, and apply 2nd order EQ centered at 31 Hz. The trick is tuning the box at 31 Hz so you can use a 5-string with it.

    All said and done, what you are trying to accomplish is making a Loud driver into a Low one. It doesn't work. The Delta has a beautiful loud, flat response curve in its ideal alignment which is -3dB at 58 Hz and not usable below 55 Hz due to port unloading.
  18. Running the numbers, I got 4.91 cubic feet, subtract 0.5 cubic feet for displacement of two 15" drivers, 4.41 cubic feet total.

    The original port calculates to 48 Hz, and the original plus additional ports calculates to 64 Hz. This is much too high and would produce a pronounced boom in the mid bass. It also unloads your drivers below 64 Hz.

    Add a 1.5" duct to the 3x5" port to tune it to 41 Hz. Add a 5.6" duct for tuning at 31 Hz.

    Note this port is too small an area for a pair of 15" drivers, and you might get whistling noise from it. YMMV.

  19. Thanks for the knowledge, man. I'm trusting in 1970's Ampeg design that there will be no whistling. :D

  20. bizzaro


    Aug 21, 2000
    If the delta pro 12 can't give me low frequency's below 50hz, how do I tune it down to 31hz. I am guessing this will really kill the efficiency of the driver. And how do you tune your box to any specific frequency?
    Add EQ??Is that a device you build into your cab or is it using the EQ on my amp to boost the low end once my cab is built? I guess I have a lot of homework to do.
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