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My Kappalite 3012HO Twin 2-Way Build

Discussion in 'Amps and Cabs [BG]' started by 5StringPocket, Jan 14, 2012.

  1. 5StringPocket

    5StringPocket Supporting Member

    Jan 11, 2006
    The Eminence Kappalite 3012HO is not usually on the short list to use for a DIY 212 bass guitar cabinet because of its somewhat attenuated low end response and pronounced high mid peak. It is, however, a powerful light-weight woofer and I've been impressed for some time with its WinISD profile versus a number of other twelves. With the proper cab design, HF crossover, and matching amp this box should slam. I have cabs built around the 3015LF and 3012LF woofers which have all the low end extension I'll ever need. This is a different flavor I wanted to check out. Three things prompted me to go through with this build:
    1. The Genz Benz Streamliner 900 amp. I'm pretty fond of the tube sound and heft this little amp delivers. Its bottom heavy, mid-scooped profile matches up well with the attenuated lows and juiced up mids of the 3012HO. It should be able to fatten up the 3012HO's nicely while those drivers should keep the STM900 low end tight.
    2. I read that an inductor tuned at about 2kHz could be used to attenuate that pronounced 2.5 kHz peak to smooth the upper mids out (Bergantino AE212). I checked this out with the Eminence 3012HO frequency response and it looked like it should work.
    3. I wanted to test an "umbrella" bracing configuration which should prove quite strong and minimize cabinet vibration.

    Most sensible players looking for this sound would just contact Alex and order a Barefaced Super Twelve T but I enjoy the design and build process. For me this is a proof-of-concept build to put my speculation to the test. I considered a number of layouts and port configurations and then Jim Bergantino came out with the HD212. The symmetry and balance of this layout just struck me. It provided a compact format which would work well with my somewhat large HF waveguide and the triangular ports can be sized to the recommended dimensions. Here is the layout:
    I used WinISD alpha and Eminence Designer to evaluate the size and tuning for this box. WinISD has better graphics but I have more confidence in Eminence Designer's porting recommendations. It also has features that WinISD doesn't such as driver volume, the effect of cabinet insulation, and recommended port size at X-max to avoid chuffing. Together these provide a capable, low cost DIY toolset.

    From similar cabs on the market and WinISD models, an internal volume (Vb) between 3.3 and 3.4 cu-ft seemed to optimize low end response and excursion limited power. I've seen several 50 Hz tuning recommendations for the 3012HO but I figured Fb would be close to the large vented cabinet design on the Eminence website. After accounting for drivers, handles, port volume, and bracing the net internal volume came out to 3.37 cu-ft. Eminence Designer recommended a tuning frequency (Fb) of 53.0 Hz with 43.7 sq-in of port area to avoid chuffing. To make the dimensions easier to work with I ended up at 53.5 Hz. This moved the -10dB point up from 42.8 to 44.4 Hz, but lowered the -3dB point from 77.0 to 69.0 Hz and increased displacement limited max power from 601.8 to 647.9 watts versus the 50 Hz tuning. I liked what I saw and moved forward. Combining the WinISD response up to about 400 Hz with the Eminence website 3012HO response data and adding a -6dB/octave (1st order filter) at 2.0 kHz generated the following:
    Along with attenuating that 2.5 kHz peak this filter provides another benefit by lowering the crossover frequency by about 800 Hz. Crossing over at around 2.8 kHz should eliminate that upper mid/low treble hole often present with 212's crossed around 4.0kHz and provide a smoother mid/high transition.

    I like the high frequency extension a 2-way system provides but detest the harshness of a cheap tweeter. The JBL HPTF-99 is a very nice 90x90 deg short throw HF waveguide I had left over from my nEarful 15/6/1 builds which is good for crossovers down to 2.5 kHz. This is a good match with a quality 1" HF driver like the Selenium D202Ti. This handles 60 watts rms with a 106 dB/watt sensitivity and very even response between 3 to 10 kHz. I'm not a crossover designer but knew what I was looking for so I contacted Ralf Patterson who provided an outstanding crossover for my 1212/66 build. He has done several 3012HO crossovers and confirmed that a 1st order low pass around 2.0 kHz should work as expected. Drivers and crossover - the heart of the cab ($570):
    I was thinking about trying a composite build but didn't want to struggle through the learning curve so I decided on 12mm Oukume marine ply (aka Joubert) which worked out well with my 1212/66 build. This is high quality, high priced 9-ply wood with a good strength to weight ratio. It added $90 to the cost versus birch or Auraco but is lighter than either and stronger than the Auraco. Here is the cut sheet. Some of the final dimensions were adjusted for the wood's actual thickness of 7/16".
    This first construction shot provides a view of the internal bracing. Large holes for drivers, handles, and the jack plate are reinforced with double-thickness ply. This adds strength without too much extra weight and works well with Recex screw mounting which I much prefer to tee nuts. PL Premium and a nail gun with 1.25" finishing nails provide solid construction and don't require a large number of clamps.
    Here are front and rear shots of the unfinished cabinet. Holes were filled before sanding and edges were rounded to 1/2" radius. Cutouts and small housings were added for casters. The umbrella bracing is a set of six 45 degree angle braces 10.75" on the long side which tie adjacent side and back panels together. Two braces are provided for each side and one each for top and bottom panels along with a laminated front to back center brace which serves as the umbrella handle. The spline braces provide rigidity of their own and distribute the load of these angle braces over a larger area. I've never had vibration issues before with cabs but this is very solid. The weight of the empty cab at this point is 25.0 lbs.
    Three coats of roll-on Duratex were used to finish the cab. Corners, handles, casters, feet, and open-cell polyurethane foam batting were then installed. Cabinet weight is now 30.3 lbs.
    The crossover was mounted on the lower tri-port shelf and the jack cup fitted with two speakon connectors and a 100 watt 8-ohm mono L-pad for HF horn adjustment. One speakon was wired to the crossover input for 2-way operation and the other wired directly to the woofers for 1-way operation. This cab can't be in the middle of a daisy chain. Only one jack at a time can be in service. I'll be using the 2-way most of the time but thought full range to the twelves would add flexibility. All wiring is 14 or 16-gauge twisted pair. Finally, the drivers were mounted. Weight at this point is 55 lbs, same as the Berg AE212.
    The 28"H x 21"W x 15"D size is easy to move around. Here are front and rear views of the finished cab:
    Now it's time to check this little beast out. :bassist:
  2. GrowlerBox


    Feb 10, 2010
    Nude Zealand
    Beautiful build, man, and thanks for all the detail. I look forward to hearing your impressions of its performance. Completely unbiased, of course!
  3. puremusic


    Nov 1, 2009
    Saginaw, MI
    It was great to see this build.
  4. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Really nice work. That inside pic really shows your attention to detail. No big glops of glue everywhere etc.

    Looking forward to seeing a pic with the grill on.
  5. MontanaBassDude


    Sep 20, 2011
    Stunning cab. Awesome job.
  6. Mystic Michael

    Mystic Michael Hip No Ties

    Apr 1, 2004
    New York, NY
    Very impressive... :cool:

  7. Philonius

    Philonius Supporting Member

    Mar 22, 2009
    2k W of the Duwamsh
    That's really nice work. One thought that came to mind; would a top mounted handle work better with those rear mounted casters? 'Cause I'm a wimp about moving heavy cabs around.
  8. jnewmark

    jnewmark Just wanna play the groove. Supporting Member

    Aug 31, 2006
    Stax 1966
    Third St. Cigar Records staff musician.
    I really like the 3012HO's and had Don at LDS build me one, with everything vertical. Here it is.

    Attached Files:

    PawleeP likes this.
  9. 5StringPocket

    5StringPocket Supporting Member

    Jan 11, 2006
    Thanks for the kind words. I may put a strap handle at the top rear edge for rocking the cab back on its wheels, but for carrying, the 2 mid-mounted side handles are ideal. This box is small enough that if you hug it to your chest the lower edge rides high enough to let your legs move freely enough to climb stairs and the top is low enough that your vision isn't blocked. For longer transport I have a lightweight collapsable aluminum hand cart that works well.

    jnewmark, I like your vertical LDS build with the low HF crossover. I was looking for a little more compact format using the natural 3012HO frequency rolloff enhanced with that 1st order low pass to cross around 2.8 kHz. This allows some of that upper mid cone breakup in but reduces upper mid extension by the twelves and allows for a simpler crossover that would work with my JBL waveguide. Both good but different solutions.
  10. love it
  11. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Have you tried it out yet?

    I'm curious to think of those HOs.
  12. dog1


    Dec 30, 2008
    Wow! I gotta build me one of these!
  13. 5StringPocket

    5StringPocket Supporting Member

    Jan 11, 2006
    I've actually been putting this thing through its paces for about a week but had to break up my posts or my wife would have had my head. My two gigging basses are an alder/rosewood Valenti PJ5 with Nordie pickups and D'Addario chrome flats and an ash/maple Carvin SB5000 with their single coil pickups and nickel roundwounds. Even though they have nice active preamps I usually run them in passive mode, using their "vintage" tone control to dial in high frequency rolloff as needed. The STM900 treble control and bass VTC complement each other because of their different frequency points. I bring these basses up as a point of reference when considering subjective tone descriptions.

    Most of my time with the 3012HOT2 cab and STM900 amp has been with the SB5000. This has really turned out to be a superb match. I thought going into it that I'd use the bass knob to set how fat the low end is and set the mid control at 220 Hz to control the punch. This sounded rather dull but when I moved the mid to 600 Hz it came to life. The settings I ended up with were quite similar to my GB Uber 410 cab:
    3012HOT2: Gain 11:00, Volume 1:00, Bass 11:00, Mid 1:30@600 Hz, Treble 12:30 Master 12:00
    GB410TUB: Gain 11:00, Volume 1:00, Bass 10:30, Mid 2:00@600 Hz, Treble 12:00 Master 12:00

    The low end does not have the depth of the 3012LF as expected but it’s thick, solid, and percussive. It almost sounds like there is a little natural compression but it might just be the way I have the amp adjusted. The notes are solid all the way down to low B with no fade, farting out, or chuffing. As pointed out by KJung in the Streamliner thread, this amp has the ability to push a large amount of low end content to a driver without making it piston. I was counting on that with this design and this is what I’m seeing. The STM900 gives the 3012HO drivers a solid, beefy low end but the 3012HO voicing is effective at keeping that low end tight and under control. Think Jamiroquai. I love the slap tone of this rig, in large part because of this low end voicing.

    The mid control setting of 600 Hz shouldn’t have been unexpected given the Streamliner’s response curve. What I like is how interactive and responsive small adjustments of bass and mid are around the sweet spots. The amount of wool or clarity seems to live in these small adjustments.

    I plugged into the left speakon for a while which runs full range to the twelves. For playing with some heavy distortion that you don’t want a tweeter in the mix this should work fine, but that prominent 3012HO peak at 2.5 kHz is audible and adds some upper-mid gank which I’d want to EQ out. It adds variety but if this was the only voice on this cab it wouldn’t work for me.

    The right speakon feeds the 2-way crossover. Ralf worked his magic again with this crossover and the upper mid transition from the 3012HO woofer to the Selenium D202Ti horn is smooth with no audible dips or peaks. Without having played one, I’ll go out on a limb here from what I’ve read and venture that this would be somewhat similar to the AE212 voicing. That big set of coils which provides that high pass filter takes the upper mid gank out and sets up the HF crossover point well. The upper mids aren’t tame or overly aggressive, they’re just even and balanced. I don’t feel the need to fuss with them. With the right match of drivers, Ralf does a good job of balancing his crossovers so very little further adjustment is needed. I installed a 100 watt L-pad to adjust the HF level but I have it set around 80% and wouldn’t miss it if it weren’t there. This D202Ti is a good HF driver. It’s smooth and warm, with good clarity and an excellent match for that pair of 3012HO drivers.

    I’m primarily a finger style player and the 3012HOT2/STM900 tone is forward and percussive enough to sit nicely in a mix without getting lost. Notes articulate well so complex lines aren’t muddy but the tone is solid not thin, even on the high notes. I ran through the old Guns ‘n Roses classic Sweet Child of Mine and it was killer – nice rock voice. The amount of headroom provided by the STM900 is a good match for this cab. There is enough power in reserve to provide plenty of dynamic headroom but these drivers can handle what the amp has to give. Some of that upper mid grind with the string windings is there and when you dig in at the bridge that growl comes through but the Streamliner smooths it out so it’s not so in your face. I like that.

    Once the sweet spot is set the fine adjustments lie with gain/volume for drive, bass/mid for low end focus and mid clarity, and treble/VTC for the amount of brightness and air in the top end. Voicing is also quite responsive to string (right hand for me) technique, plucking toward the neck to round and fatten the notes or toward the bridge to tighten them up and cut through. I’m having a lot of fun with this and very pleased with way this 3012HO Twin 2-way matches with the STM900. I still have to install a grill but this one’s a keeper! :hyper:
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Not sure how you have your jack switching configured, but beware of backfeeding the low pass section of the crossover (ESPECIALLY if it's second order). It needs to be switched out of the circuit one way or another.

    The reason for the caution here is that if you look into the speaker from the LF driver's terminals (and not from the normal input configuratin), a second order filter will have a shunt cap across these terminals and some amps may explode (yes catastrophically) when presented with such a large illegal load. It's also because there may exist a resonant tank circuit (one that stores energy as a phase shifted signal in an inductor-capacitor network) and these too can cause disasterous effects.

    The effect may or may not be an issue with first order filters, but it would be prudent to isolate everything else from the woofers if this kind of full range operation is desired.
  15. open.eadg


    Jun 13, 2010
    Nice and clean build to the last details, I like it very much. :cool:
  16. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    DFW, Texas
    Looks very nice!
  17. will33


    May 22, 2006
    OP, I'd be following agedhorses advice before using this cab as a one-way, 12's only cab again, in the interest of preserving your nice new amp. In simplisitc terms, when running woofers only full range with the crossover still in the circuit, you're sort of "running power through the crossover backwards". This can present all kinds of messed up stuff, including dead shorts, to your amplifier. Work out a switching scheme that completely isolates the rest of the circuit from the woofers for operating like this. Running with the crossover and tweeter is no problem.

    Other than that, quite a nice build...well done.
    PawleeP likes this.
  18. 5StringPocket

    5StringPocket Supporting Member

    Jan 11, 2006
    Thanks for the warning. This is a valid concern. I understand the issue here and had an isolation switch in the original proposed wiring. Since the woofer low pass is a 1st order filter there is no shunt capacitor or there would have been trouble as pointed out. I agree it would be prudent to isolate everything else from the woofers if this kind of full range operation is desired. At this point after hearing full-range versus 2-way operation I'll probably just disconnect the full range. 2-way is the only way I'm going to use it and it's not worth leaving risk in the system.
  19. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I brought this up because other folks might try it on their cabinets unaware of the potential risk. Unless there is Zobel correction networks present, it's unlikely to be a problem with a first order filter on the woofer.
  20. 5StringPocket

    5StringPocket Supporting Member

    Jan 11, 2006
    There is no Zoebel correction network but for clarity here is the wiring diagram with a DPDT isolation switch. The switch should be mounted in the jack cup so that when it is flipped toward the 2-way jack, the signal travels through the 2-way crossover to the woofers and HF driver with the bypass jack isolated. When switched toward the bypass jack, the signal goes only to the woofers and the crossover is isolated. The woofer 1st order low pass, working with the 3012HO rolloff and the 3rd order high pass, seem to provide steep enough slopes to minimize interference between low and high frequency sections. Still really digging how smooth and transparent this crossover is.
    Also, the grill finally came in. I like the 5/32" hole grill with 1" bent edges from Reliable Hardware (thanks Greenboy). I use a 1/4" wide strip of adhesive foam gasket around the edge to prevent vibration. It added 3.4 lbs but I really like the way they look and hold up. Final weight of the finished cab with grill is 58.4 lbs. Here are a couple shots of the finished product. The sun came out right when I took the shot with Streamliner 900 on top but you get the idea...

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