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.

Cab Question for Bill F. and BruceG

Discussion in 'Amps and Cabs [BG]' started by joegeezer, Mar 15, 2006.


  1. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    Help me understand this if it's possible for my feeble brain to comprehend. I had an Avatar 112 cab, with the DeltaLFA in it. It was the newer, larger style one. It just didn't seem to have the SPL that I had expected from it, so I sold it. I had heard some guys say that the smaller, older one they made was really good, so I bought one from a fellow TBer. It has the Kappa 12A in it. Much better SPL, to my ear.And great sound!:eyebrow:
    Now I have a chance to get a 3cu ft box for 2-12s, so I tried WIN-ISD Beta, on it, with 2 Kappa's Just doesn't look like it will work. Then I thought , well check the Avatar. So I measured it up. It's about 1.5 cu ft, with 2- 4"X1" ports. WIN-ISD says thats tuned at about 110 hz! And, shouldn't work at all. But it does,and has pretty good low end. What's going on? And if so, what would I port the 3cuft box at with 2-Kappa's? I know that reflex box science is not something that can be absolute, and stuff that shouldn't work, sometimes does, but for a novice like myself, it leaves me pretty much in the dark about what to do here. If you have time to mess with it, can you shoot me what you would do here? Thanks Guys!
     
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    When the box is too small you get a response bump in the 80-120 Hz range, which to your ears sounds like solid deep bass. It isn't. Bass down in the first octave is more felt than heard, because your ears aren't as sensitive in the first octave (see Fletcher-Munson). For the most part what we associate with strong bass is actually the second octave, and bass cabs tend to be tuned to respond better there as it seems louder, and louder sells. Very few cabinets are actually capable of true chest-thumping-take-your-breath-away deep bass.
     
  3. The Kappa 12 is +3.1 dB more sensitive than the Delta LFa.
    Right out of the gate, the Kappa is noticeably louder. 3dB is the threshold of noticeable change for most folks.

    With a net volume of 1.5 each, the Delta Pro 12 in QB3, tuned at 58 Hz gives an F3 of 65 Hz. Sensitivity is nearly identical to the Kappa 12 you prefer. Wired in parallel for a 4-ohm load, you can expect a sensitivity right at 100.

    Two Kappa 12 in the same box is SBB4, tuned at 45 Hz has an F3 of 97 Hz. Sensitivity is 101 for the pair. This driver is designed for a smaller volume, higher F3, and corresponding higher sensitivity.

    None of these are solid performers in the bottom end. Low, Loud, Small.... pick two. In your case above you chose Loud and Small, and discarded Low.

    The Delta Pro 12 pair will give you deeper bass response due to the lower F3. It also has the same Xmax, and slightly better Xmech than the Kappa 12. High frequency rolloff is about the same for both drivers.
     
  4. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    A single 12 cab with one DeltaLF would be nice for gigs that aren't so loud if you want a rich and smooth tone, but where a DeltaLF or similar driver really begins to show you the difference is when you have a lot of wattage and a couple of them - since they are less efficient (but have a decent xmax and can really handle power even with a lot of demand for true lows). The DeltaLF also makes a pretty smooth frequency distribution (in the right size and tuning of cab), so it's not like a lot of 12s that have a lot of peaks and valleys up near the top of its response. It's a good basis for a PA-like cab design if the other components are chosen right.

    So. I'd say it's great in pairs with a big amp and especially for those who gig without PA support, with maybe a 210 or 410 on top if you also need more of the shrill directional upper peaks sound so many like ; } ... No doubt about it though: if you have the wattage behind it it'll make a LOT of low end, and in my experience can be less boomy than the midbass hump designs.
     
  5. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    I think I'm understanding now.From what Bill says then, it's like my days of racing motorcycles. In tuning a race engines intake and exhaust tract lengths. For practicallity in lenghths, use 1/2 or double the wave length, to take advantage of the returning wave, for a ram tuning effect, is how it's done there, and it stands to reason , that it would work in this case also. In intake tract lenghts, I know the constant is figured at 1100 ft per sec. Is it the same velocity figure in a speaker box? I think I'll go with the Delta Pro's as Bruce said, tuned at 58 hz. Thanks you guys!


    Looks like loud and small fits my ear the best. At least for practicallity for now. As time goes on, I think that a Tuba 24 and an Omni 2-10 are in my future.
     
  6. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Pardon my poor skimming, but what box are you wanting to fill? Because I don't recall a 3-cubic-foot two-by.
     
  7. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I believe intake tuning on internal combustion engines works on the basis that intake tracts are like an organ pipe, so they're tuned to 1/4 wavelength for a node at the valve and a peak at the entrance, so all that matters is the length (assuming the cross-section is sufficient to avoid turbulence/drag).

    Cabinet port tuning uses a different principle, a helmholtz resonator, where the mass of air in the port resonates against the spring provided by the volume of air in the box and cross-sectional area of the port, like a mass bouncing on a spring, so the port volume, port cross-section and cabinet volume all interact.

    Alex
     
  8. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    I was about to type a bit on pipe chamber tuning for two-strokes here but now... ; }
     
  9. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    Two strokes are a whole different animal, for ram tuning than a 4 stroke. I've raced both.
     
  10. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    Actually I'm trying to fill a 3 cu ft 2-12 cab.
     
  11. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    Using that then, Why does this Avatar box at 1.5 cu ft, tuned at about 100hz, work to my ear? Isn't that doubling or halfing the wave?
     
  12. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    What I'm saying is I wonder about your measurements of internal space, because last time I estimated the Avatar 212 cab it seems like I came up with something significantly larger than 3 cf. Or are you talking some other box?
     
  13. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    No, this is their older smaller, cube type cab, no longer available. Check the pic I put up on the cab wanted thread.
     
  14. 3 cubic feet makes for a very small 2x12. Too small to satisfy my need for low freq. using any of the (excellent) 12 inch speakers eminence makes.
     
  15. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5


    That may be, but that little Avatar cab, works for my ear, and back. And how about those Bergantino's everybody raves about. They are super small, and sound great. I've heard some guys using them and I was very impressed, but my wallet says no.
     
  16. There is nothing wrong with that of course. I have 2 questions for you:
    - do you boost the bass a lot on your amp?
    - How many watts is your amp?
     
  17. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    OK here's what I'm working with. An Eden WT-405 in a Behringer BX1200 combo cabinet,(Don't start bashing on me, it's just a box!), 1.5 cu. ft. tuned to about 50hz, with it's stock single port, with a Kappa in it. The little Avatar, with Kappa, looks to be tuned at 100 hz. I am going for the stacked line array set-up. The available cab is 3 Cu.ft. 2-12 empty for now, and no ports in it. 29.5X17X14. I thought I could use the Avatar on the bottom because it has the largest foot print, then the 2-12 cab, and the combo on top. Only for bigger gigs, otherwise one or 2 of the 12s is enough. They are all 8 ohms, and the amp is 250 at 8, 400 at 4 , and 600 at 2 ohms. Thats the plan. You see, I'm trying to figure out why that little Avatar sounds so good, tuned the way it is. It just didn't make sense to me. I thought I had it figured out by the wave doubling idea, but now I'm still stumped. I only boost the bass about 1 or 2 clicks from flat on the Eden. Otherwise, like most Eden users , the rest is flat.
     
  18. Are you sure the avatar is tuned at 100 hertz? how did you calculate?
     
  19. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Jumping into the middle of this, I play through a 1x12 in a very small DIY cab. My amp is not super powerful, and I boost the bass by anywhere from 3 to 6 dB. But when you boost the bass, you are mainly boosting the first harmonic. The first harmonic is only a fraction of the total signal amplitude.

    I have estimated that you lose about 2 to 3 dB in headroom for every 6 dB of bass boost, but if you gain the same 2 to 3 dB in overall sensitivity, then it's a dead heat. Building a small yet efficient speaker for portability, and then EQ'ing it to sound good, might be a reasonable strategy.

    Or it might not be, which is why I still refer to my speaker as "experimental."

    Note that if a speaker has a 12 dB per octave rolloff, then you can only get away with raising the cutoff frequency by 1/2 octave before my strategy becomes a losing game.

    At the same time, my rule should work in reverse. If your speaker has too much low end, and you end up EQ'ing the bass downward, then all you gain is a bigger speaker to haul around. That's why I remain skeptical of the large and inefficient cabs on the market with flat response down to the lowest fundamental.
     
  20. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I don't know how Eden is, but many amps are not flat when the EQ knobs are centered.

    If the Avatar sounds good, it's because the response curve is favorable to your sound, even if the curve is not what you originally expected.