Cab Material + Port Questions

Discussion in 'Amps and Cabs [BG]' started by Cúl-Báire, May 2, 2005.

  1. Well My new cab construction project is set to start any day now- Becasue my hartke's are officially flogged out :bawl: I do have a few questions regarding the construction and tuning of the cab however.

    Firstly the cab will be a ported 1x12" internally braced and such- I was just wondering what the best material would be to make it out of. I was looking at using 3/4" Marine- A A/B grade Plywood. But I read in Bass Player that Plywood cabs are a bit brighter than pressed wood cabs- Would using MDF sound all that much different other than making the cab weigh a ton?

    I'd prefer lighter weight but if the MDF is going to give a lower end to the tone, I would probably consider that abit more...

    Also This question related to changing the speakers in my Hartke 2x10" with Emienece Delta 10B's- Now the Cab is sealed but I would prefer a ported cab, as according to winSID it gives a much better responce. It says I need tow ports @ 82mm in diameter and 116mm in length. I was wondering... Since I have no room on the fornt of the cab, can these be put on the back? (Sorces on here say yes)... But I was really worried about does the dimentions change?

    Will the length of the port need to change if it's on the back wall... I.e from the rear opening to 116mm from the Front baffle- as opposed to from the front... 116mm away from the fornt baffle?

    Thanx for any advice you guys can give, it will be greatly appreciated :)
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The material doesn't particularly affect the sound, but the construction does. I personally use 1/2" Baltic Birch plywood for most of my cabs, but they are extensively cross-braced. Commercial boxes tend to use 3/4" as it's less expensive to use a heavier material than it is to pay the additional labor expense incurred with installing crossbracing. I'd avoid MDF, as beyond the weight issues it doesn't have the durability of plywood. Marine ply is great if you plan on using the cab as a boat, but otherwise Baltic Birch (European, not Asian) is the best way to go.

    You can put ports anywhere you want to, the sound coming from them is omni-directional. In fact, rear porting can work better than front porting if you typically have your cab set up in front of a wall, as the boundary loading of the port output can increase low frequency sensitivity. WinISD does allow you to specify the size, shape and number of ports to allow you to find a workable combination. Making rectangular ports that double as bracing is a very good practice.

    You might want to reconsider your 2x10 scenario. Delta 10s have a high fs and small xmax and are best suited as guitar drivers, unless you have another box loaded with something sufficient to handle the low end. If your 1x12 is going to be loaded with, say, a Delta 12 LF then you'd be OK, as long as the Delta 10s are loaded in a sealed box to limit their excursion. If you use Delta 10s in a ported box excursion is going to be a problem.
  3. My version of WinISD only provides the Flat alignment, which IMO is usually not the ideal. I'm a big fan of the SBB4 alignment, due to its lower tuning and tight bass. You can obtain SBB4, QB3, and Flat alignment calculations from the spread sheet in my signature.

    First, you have to decide which drivers to use. IMO, the Delta 10 are better suited for a PA system than electric bass. None for me, thanks.

    The driver is selected based on alignment, cabinet volume, and tuning. I like a tuning near the bottom of the lowest note, to prevent over excursing the cone. This is 41 Hz for the typical 4-string bass, or 31 Hz for a 5-string.

    You mentioned a 1x12 cabinet. The Omega Pro 12 with Alpha 6 is an ideal combination for this requirement. Both drivers are equally matched in output. The 12" runs in a modest 1.23 cubic feet at 39 Hz (SBB4) and the 6" in a sealed (B2) 0.28 cubic foot subchamber.

    If the cabinet wood is contributing to the sound, it is not properly braced. A resonating panel wastes acoustic power and colors the tone in an unpredictable manner.
  4. Thanx for the info guys.

    I was considering the Delta 12's as they are easily available in Australia, not many others are unfortunatly... I wanted to use the Delta LF's but they are unavailable in Australia. The LF is clearly better and my look at importing them even though it will be very expencive to do so :-(

    Simarly with the 10's, I cant find anything with a decent frequincy responce that will fit in the cab the same size as the hartke- I'd like to keep the speakers the same range so they have similar tone- Will they be ok with the Delta 12LF under them?
  5. Petebass


    Dec 22, 2002
    QLD Australia
    Can you wait a bit longer? I've heard a rumour that the importer of Eminence into Australia has just let go of the reigns and no-one has yet jumped in to take over as importers/distributors. The unavailability problems you're speaking of might disappear once all this is sorted out.
  6. Hi Pete,

    Greatings fellow australian bassist :) I added you to msn messenger btw. :)

    Ummm I cant really wait any longer- my Hartke is getting worse and I sound like total ass running though that cab- Warrenty isnt likely to happen as
    1) No serial number that I can find...
    2) ELFA wants to keep it for a while, this is my only cab! :help:

    So I am faced with building a new cab- or buying a lovely Aguilar or Eden 2x12", very expencive option also- and money thats reserved for my new amp...

    I'm going to import the Delta 12LF first, I will debate the 2x10's futher while building my new cabinet... :)
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    If you can easily get the Delta 10s fine, do so, just don't port the box, and still get the Delta 12LF to handle the bottom end where the Delta 10s fear to tread.