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Downsizing - NROD port tuning question

Discussion in 'Amps and Cabs [BG]' started by Koeda, Mar 28, 2013.


  1. Koeda

    Koeda Supporting Member

    Aug 21, 2007
    Nashville
    SWR LA10 replacement rig for practice being designed. Am looking at using a pair of Alphalite 6A (http://www.eminence.com/speakers/speaker-detail/?model=Alphalite_6A) in an a la MiniMark 2x6 style cab. Recommended vented volume is .1 to .6 cu. ft. for the drivers. Being a bass cab - looking at a Vb of 1.1 cu ft for the pair. Been playing around in WINisd and am considering a port tuning of the box Fb at 53Hz.

    Trying to compromise between farting and drop off. Will be using with a G-K MB200 and a 4 stringer. MiniMark low is spec'd at 59Hz for similar cab design and similar speakers. 1/2" ply should bring this box in sub 20 lbs. Bracing not drawn.

    The Eminence site has a vented mid/bass design for a single driver with a Vb of .55 and an Fb at 82.51 (w/ HP at 75 Hz or higher). Figure this will fart out at the low E for sure with this design sans HP at 75Hz.

    Looking for opinions on what the best tuning frequency should be for a box using a pair of these 6A's?
     

    Attached Files:

  2. I own several Alpha 6a, and would never consider them for a full range bass.
    Even driven at a whisper volume.

    These drivers are simply not designed for bass.
    The Fs is 118 Hz, meaning they really aren't much good below this.
    Xmax is 3.5mm, which isn't half bad, but the Vd is so small it won't move much air.

    Combine Alpha 6a with an S2010 or BP102 and a passive 500 Hz crossover.
     
  3. Hi.

    I have no personal experience about 6a's, but no amount of quick modeling did make Your suggested cab to work well in sub 75Hz region.

    Since You're going to build a pretty big box anyway, why not stretch it a about an inch more and put a 10" Deltalite II in there?

    At least in paper/screen it smokes the 2x6 design on every detail.


    There is a reason why X6 bass cabs aren't more popular, there just isn't many (if any) drivers in the budget end of the price spectrum to slap in there.

    IMHO at the moment the point of diminishing returns in single size DIY bass cabs is 10". Smaller drivers just don't offer any advantage over their larger counterparts.
    To me anyway.

    2,3 or 4 way designs are a whole 'nother ballgame, obviously.

    Regards
    Sam
     
  4. What kind of practice? My practice amp has a cheesy little 6" can make enough 80hz to play with a saxophone in full song.
     
  5. Koeda

    Koeda Supporting Member

    Aug 21, 2007
    Nashville
    Thurs night weekly with a 5W Blackstar and v-drums. LA10 balanced out the coldpack well, but after 50, the weekly trip up and down 3 flights of non-ada narrow stairs isn't as fun (especially after the coldpack...). Light and narrow were key design objectives.

    Was looking at the PJ Briefcase or the MiniMark, but when Sweetwater had the MB200 @$259, the couple years of xmas giftcertificates from them had their excuse.

    Sam, I was shying away from the S2010 because of the typical box shape of the 1x10 cabs and its 8ohms (MB200). Also liked what I saw from the narrow shape and reviews of the PJ/MiniMark using ~2x6"s. If it did work, could have some fun looks with that shape box.

    Response looks much smoother and deeper w/the S2010 in a ~1 cu ft, so may have to consider. Saw "the Duke" had a decent budget design for the S2010 (hoping he may chime in). Guess I could use my same box but mount on a side instead of an end...
     
  6. Koeda

    Koeda Supporting Member

    Aug 21, 2007
    Nashville
    After comments was looking into the driver more, think I will abandon the 6A's.

    Now looking at the B&C 6NDL38 (same as MiniMark). Looks like a much better choice than that the Alphalite 6A. Fs is much better at 72Fs w/ Xmas at 6mm and recommended tuning to 62Hz. Adds a couple pounds and $$$ over the S2010 but alows the thin profile box was looking for.

    Still contemplating a design with the S2010 with a side mount rather than end mounting in the same basic box dimensions.

    Will keep playing around with the designer and checking the comments. Thanks so far,
    David
     
  7. will33

    will33

    May 22, 2006
    austin,tx
    With a 4 string and not needing much below 100hz, a pair of Emi. Beta 8's might do the trick. Could make the box just wide enough to house the speakers and port it either above and below them, or in the rear.

    If the LA 10 was doing the job for you, you really don't need to be concerned with getting much output below 80-100hz. Dukes coffeehouse cab would be a good solution for this. Don't worry about the 8 ohms thing, you'll never notice it. Just if you're OK with more of a "cube" box or if getting it really narrow is that high a priority.

    Of the really small speakers, the Beta 8's may sound a little more "like a bass", because of a little more displacement/output in the 100-300hz area and a slightly lower topend rolloff, though they'll still reach 4khz.
     
  8. Koeda

    Koeda Supporting Member

    Aug 21, 2007
    Nashville
    Thanks for the 8A suggestion -
    Would fit the bass end better - but for the extra width and extra 12 lbs, think the only benefit would be from the wallet (narrow 3 flights of stairs weekly).

    Looks like I am settling on the B&C 6NDL38's and will call in the order. Build an report to follow.

    Thanks again, David
     

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