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for those of us who build cabs

Discussion in 'Amps and Cabs [BG]' started by JacksonsMen, Feb 12, 2006.


  1. what do you use for ports? and do you go classic round, or for the solid build in type? for any specific reason?

    im planning to use 2 4"x4.5" round cardboard tubes (i stole from an empty spool of wire). but i was just curious as to what kind of stuff yall use?
     
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Truth be told, I cut a hole with a hole saw, and backed it up inside with a rectangular port made of plywood scraps.
     
  3. do you get port whistle? and did you use anything to calculate the port?
     
  4. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    I use the WIN-ISD cabinet tuning computer program , that you get download for free, and I just buy the round plastic ports, because their so cheap. And the WIN-ISD program compensates for them not being a true 3 inch port, but actually 2.68 inch. I have had good success with my cabs turning out to sound real good. Us broke guys on here need to stick together. In my years of playing, I find that if you push cheap speakers with alot of good clean power, and a good amp or preamp section, that you can get them to sound really good. I use for my 10's those cheap Chinese , Madison Warriors, and I think that they sound just as good as BP102's. And I've never blown one yet. But for 15's I get Eminence 15LF's cause their actually not too high in price. Good luck to ya!
     
  5. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    It is probably fair to say that I ran up against a Murphy's Law: "If you assume a cab design is temporary, you will end up using it forever." I took the port dimensions from WinISD, and estimated a rectangular box with the same air mass as a round port. In reality, I could have just squared the hole after cutting it with the hole saw, in which case it would have been a legitimate square port.

    I don't discern any whistling, but it would only be at the lowest frequencies in my design. Using WinISD, I did check the port air speed graph, and my rule of thumb is to keep the speed below 0.1 Mach units.

    Given that I just ordered a driver for a new cab, I will soon be able to report on anything I do differently.
     
  6. PVC for round ports, plywood for slot ports.

    Apply silicone sealant to the PVC ports and they will bind nicely in the wood cutouts. To get them out, you have to take a Sawzall to the plastic ports, then pry them out of the cabinet.

    Be *sure* to allow a long dry time for the silicone to cure. The outgassing (vinegar stink) is harmful to speaker surrounds, especially foam. Don't install the driver until all the smell is completely gone.
     
  7. good stuff to know. im usuing an eminence legend b15 for the cab im building now, aside from a very small xmax, it seems to be a solid speaker

    does anyone round over their port edges?
     
  8. I use slot ports. The benefit is that they also serve as bracings. Downside is that experimenting with port length is more difficult..
     
  9. the only way i was ever able to play with slot port lengths (when doing car audio) was to cut MDF into 1" wide slits and glue the ports in pieces, if it didnt work open the top and knock a piece off/add a piece till i got it tuned to the way i liked it, once i got there i would re-build the port out of a solid piece, tedious, but worth it
     
  10. I rounded-over my ports - but only on the outside of the cab. The inside i left as a sharp edge. Ditto for air-velocity as stated above.

    I remember reading somewhere that as long as the ports aren't too long, you should be able to stay away from huge amounts of mud - so i used two ports instead of one.
    Nice and Tight:)
    This way i can always block over one port if its booming (which it doesn't very often)
     
  11. thats exactly why im doing two 4" pors and not one