fEARful 12/12/6/1 with T3W crossover

Discussion in 'Amps and Cabs [BG]' started by Gemtone, Oct 16, 2020.

  1. Gemtone


    May 20, 2018
    Denton, TX
    So, for a pandemic project i decided to build a fEARful 121261. My good friend Dr.Jim encouraged me to pursue the T3W crossover network. It seems like there had not been a T3W crossover designed for the 121261,so SClifts and some other great guys here on TalkBass came up with the schematic! I ordered the components, flat pack and drivers... and ... well.... this thing fEARful 121261 T3W.jpg 02 fEARful 121261 T3W finished.jpg sounds so amazing..... beyond accurate description..
    Foz, CharlieC, Basslice and 6 others like this.
  2. Very cool. Would you care to share the T3W schematic?
    Diegombass likes this.
  3. Blues Bass 2

    Blues Bass 2 Supporting Member

    Oct 3, 2001
    Davenport Iowa
    Looks really great . I'm sure it sounds that way too from my previous fEarful builds .
    Nice !
    Gemtone likes this.
  4. Foz


    Jul 26, 2008
    Jax FL USA
    delta7fred, Gemtone, Doufuss and 2 others like this.
  5. Gemtone


    May 20, 2018
    Denton, TX
    Foz posted it below. It was not that hard to build. I have built several CBG crosses for 1261 Cubes, so I had a bit of experience. I dont have anytning to really compare it to, but it is amazing...
  6. Kro


    May 7, 2003
    New Jersey
    These cabs (those with the t3w) have always fascinated me, as the amount of care that went into designing the crossover by the community I find very impressive. I've never been able to hear one in person though. :(

    I have a quick semi related question: does the crossover only affect the interplay between the mid and tweeter? As in, would there be a benefit to using aspects of the t3w design at all with one of the tweeterless Fearfuls?
  7. Wasnex


    Dec 25, 2011

    AFAIK the cheap but good crossover does not apply an LPF to the mid range, so you get a bit of a bump in the response and some phase nastiness between the mid range and tweeter.

    From fEARful passive crossovers by greenboy
    A high-pass filter is essentially half a crossover. The idea is to let the midrange driver (Alpha6A/Alphalite6A or 6ND410/6NM410) roll off naturally. The tweeter then just fills in the top of the spectrum. The difference in mid driver sensitivities and user tastes can be compensated for by using a variable L-pad.​

    The T3W adds an LPF so the mid and tweeter integrate better.

    Here is the response plot of the Alpha 6A

    Here is the response for the 18 Sound 6ND410

    The 6ND410 has been superseded by the 6NM410, but I can't find the new driver on 18 Sounds website :confused:.
    Kro likes this.
  8. Kro


    May 7, 2003
    New Jersey
    Awesome, thanks for that! So it seems like the mid has fairly even response on its own when not combined with the tweeter. Great, now my eyes are wandering to other Fearfuls...
    Wasnex likes this.
  9. Wasnex


    Dec 25, 2011
    From what I have read, the T3W tames the spikes/resonance of the mid driver's upper response. I couldn't find a good frequency response chart, but I remember seeing some in the past and there was a bump in the high mids with the CBG crossover.

    Another thing to keep in mind. If you use the L-pad to vary the level of the tweeter, you're shifting the effective crossover and most likely screwing up the phase response across the crossover region.

    Probably not generally a concer as most bass players don't put out enough energy in this frequency range for it to cause problems. I tend to use fairly hyped mids and highs, so it's noticeable to me....this is a general statement about the tweeter in bass speakers, I have never seen a fEARful.
    Kro likes this.
  10. sclift


    Oct 31, 2012
    LA outskirts
    The low/mid transition is roughly the same as with the CBG. The differences are above 1 kHz. Without a tweeter the response drops rapidly above 3 kHz. I sometimes use mine with the tweeter turned off, but wouldn't necessarily recommend building one without the tweeter.

    IIRC the 6NM410 is a 6ND410 with a different connector arrangement, made for Clair Bros. The published specs differ a bit, but they measure about the same. The 18sound plot above is somewhat optimistic - there is typically a ~5 dB peak around 4 kHz. Some measurements here high-efficiency_midrange-drivers except I don't recall a kink at 700 Hz.

    The phase match between the mid and tweeter around the crossover frequency is fairly good, so the L-pad works like a shelving control.
    Kro and Wasnex like this.
  11. BertDewa


    Mar 24, 2022
    Sorry to bump an older thread, does someone know where to get a crossover for a fearful 15/6 in europe?
  12. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    I bet it sounds great. I have the original 12/12/6/1 with the T3W, done in 2015. I honestly thought the plans have been online since then. @12bass worked with some folks to design the pre-amp then, it's all over my paygrade. It did make a huge difference over the CBG mid.

    True 3-way fEARful bass enclosures

    True 3-way fEARful bass enclosures
  13. kbakerde

    kbakerde Supporting Member

    Jan 24, 2012
    Really nice work there. Been feeling like I’ve been having a Fearful itch for a bit now. Had an idea to go with a Carbine/fEARful pairing, although I picked up a TT800 recently. Liking it so far. Pondering the idea of a pair of 12/6 cubes or a 1212/6.