Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Dealing with very low QTS.

Discussion in 'Amps and Cabs [BG]' started by Petebass, Aug 26, 2003.


  1. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I'm looking to build a single cab that has one 12 and 2x10's in it. I've decided that the 10's will be the lightweight P.Audio Neodymium drivers, I've used them before and like them. So the obvious choice for the 12 would be the 12" version of the same driver. Click
    HERE for details.

    As you can see, the QTS is 0.16. I've been using the formulas and table from Vance Dickason's book to determine the correct cabinet size, but they don't account for a QTS that low. And WinISD seems a bit puzzled by it.

    All suggestions welcome.
     
  2. unharmed

    unharmed Iron Fishes

    May 19, 2003
    London, England
    Sorry, mate....wish I could help you on that one. Listening intently for the answer though 'cause I plugged that one into WinISD as well and got a bit confoozed :)
     
  3. Hi Pete, I don't claim to be anything of an expert on the technical side of speaker building, but the 12" speaker you have your eye on seems a strange choice to me. Although it's light and has excellent efficiency, the fs of 50 htz seems a bit high to satisfy a five string player.
    Have a look at these Peerless speakers over at WES Components at Ashfield, and tell me what you think. ( especially the 12" speaker, 2nd from the top ). They do have speakers available with better efficiency but, as usual, at the sacrifice of good cone excursion.
    They ( WES Components ) have a website ( The peerless links on it have some very helpful speaker building info http://www.wescomponents.com/Peerless.htm ) but it's not as comprehensive as their catalogue so I've scanned a page that I think you may find interesting. :)
     
  4. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I know WES components well. That's where I buy my crossover compnents. I've spotted that Peerless driver a while ago and will probably one day make a home theatre sub out of it. Excellent Xmax and a very low Fs of 18Hz. However I did run some calcs and it had a surprisingly high -3dB point, something like 55Hz from memory. And it's way too innefficient for the gigs that I do. From what I can tell that driver was designed to be used with the matching passive radiator.

    As for the Neo 12, I have a 5 string but spend very little time down there. I've never owned a 12" cab before. Actually I've never seen anyone use one here in Oz, though they're common overseas. I'm not too worried about the lack of sub 50Hz frequencies. Why? Because 100% of my gigs have PA support, usually with 4 or more 18" subs pushing those frequencies for me. I even find myself wining those frequencies out of my EQ, especially with a 15 as part of the rig. I like a punchy sound that cuts through the mix and through the overspill from the FOH and Drumfill.

    I haven't researched any other 12's yet but I probably will. First I want to know if the Neo 12" is an option. I have no idea how big a cab it needs............
     
  5. Low Qts drivers don't work in SBB4 alignments.

    This driver has an EBP of 294, meaning it is definitely oriented toward a vented box. The QB3 specs are 0.23 cubic feet tuned at 120.6 Hz. Optimal Flat is 0.14 cubic feet at 128.8 Hz.

    Published response curve is down -10 dB at 50 Hz.

    It's a PA driver.
     
  6. geshel

    geshel

    Oct 2, 2001
    Seattle
    Yup, a QTS that low and an FS that high point to mid-bass use, to me.
     
  7. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Thanks guys. I'll look around for alternitives.

    By my calcs, 0.23 cubic feet is a tiny 6.5 litres. Is it even possible to fit a 12" speaker into a box that small?
     
  8. geshel

    geshel

    Oct 2, 2001
    Seattle
    Not if it's more than 3.5" deep!

    I guess you could make a cone-shaped enclosure. . . :D
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    It's always about "cones" with you Geshel :)
     
  10. A 12" driver displaces 0.1 to 0.15 cubic feet, which is added to the required cabinet volume. Even then, the internal volume would be barely large enough to hold the driver diameter and its depth.

    The easy way is make the cab larger, and use non-compressible filler blocks on either side of the magnet to reduce the volume.
     
  11. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Bruce, your previous post brings up a question that I've been wondering about for a while. How much volume does the average 10, 12 or 15 displace... You said 0.1 to 0.15 cu. ft. for a 12, how about the other two?

    Do mfrs. publish this? Did you calculate/meausure the volume of some 12s etc.?

    Thanks!
     
  12. All the data in my spread sheet comes from published data. Most of it is on the reference section on my site under the various manufacturer directories. Some came directly from the manufacturer by email.

    Driver displacement isn't published all that much. A drag, for sure. One can average it out for a given driver size and make an educated guess. I have a column for displacement in my spread sheet.
     
  13. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago