faux bi-amping

Discussion in 'Amps and Cabs [BG]' started by CrackBass, Jul 20, 2005.

  1. CrackBass


    Aug 10, 2004
    i have been pondering building a tuba 24. don't need it by any means but... the thing is how to make it work with my rig. i know the optimal thing to do is to biamp with a crosover and a stereo amp or two bridged amps. i don't really want to do this cause basicly it's a hassle. i wouldn't use the tuba all the time i'm sure, so i would have to rewire a speakon connector every time i switched configurations plus put my crossover in my rack (it's already full so get a new rack) plus haul the tuba around. what i would like to do is maby find a passive crossover for the tuba with a high pass out so i could run one signal and power everything. then i could use the same cable with either configuration, adding a jumper from the tuba to my current cab when i wanted to run the tuba. would this work? does anyone make a crossover for such an application? what would be the resulting impeadance that the amp would see (4 ohm tuba +4 ohm cab) what are some potential problems of such an endevour.

    btw although i know a lot about bass gear, i don't know a lot about passive crossovers, so if this is impossible go easy on me guys.
  2. Put a low pass filter in the tuba and call it a day.

    This is a 20mH inductor in series with the driver as an 80 Hz 1st order low-pass filter. Plug the Tuba into the power amp in parallel with your other cabs, then rock 'n roll.
    cfsporn likes this.
  3. PubliclyViewable

    PubliclyViewable Supporting Member

    Jul 2, 2000
    Heya bgavin, care to revisit your 10 year old post? Haha

    I am in the process of acquiring a 4ohm Eminence HL-10C Tuba 24 to compliment my pair of 8ohm Deltalite II 2512 Jack 12's. Much like the OP I would like to keep my rig mobile and modular. But the catch is I generally run stereo, so that would mean

    CHANNEL A = bass//preamp 1-pedalboard//amp//top Jack 12,

    CHANNEL B = bass//preamp 2//amp//Tuba & bottom Jack 12.

    To keep it modular and versatile, I would need a passive crossover as stated by the OP. My issue is that I'm not entirely sure where to cross out of the Tuba with the Jack... I'm thinking 100-120hz? Or would you suppose that the Jack is good down to 80hz and mix well?

    I power the cabs with a Crest ProLite 2.0 DSP, so I can set my HPF at either 12dB or24dB slopes for the Tuba around 40hz and have a real nice punch :) I found a nice impedance/wattage calculator (LINK) and at 2.7ohm the Crest is at ~760w.

    Since the Tuba would be seeing just over a 500w potential, is there any specific components I should be looking into? As far as I'm aware, I can't find an L-pad or anything to even the perceived volume...

    Thank you in advance!
  4. rigtec


    Jan 30, 2012
    Hi CB,

    I use a Bi-Amp (sometimes) and the "Easy way" that you're hoping to find... may not always be the best way. To explain ...a passive X-over used as with the "high frequency section" of a system, isn't a problem because of the (short) wavelengths and (Relatively low) power involved. But you start using a passive X-over with a 'Low freq' load on it and you're asking for trouble. A passive X-over can get very hot above a nominal amount of power running through it. It will also be 'Subject to burn-out'; this is why pro-sound people don't use them for their subs or bass cabinets.

    They're also Extremely power hungry; creating a lot of heat instead of just passing the energy on through to the next component in the line. An Active X-over however, is a different story. They're already getting the power needed to operate from the "internal power supply" that they are built with, so they don't take away from the signal load. Another plus point regarding active X-overs is you don't have to build new 'Speakons' when you are not bi-amping. You only need not feed the portion of sound gear that you're not using e.g., amps, speakers... and run full range through the boxes that you are! Wiring it is simple, See below:

    This is Basically what I'm doing when using a bi-amp. PS: If you don't have any Blank space in your rack for another component to fit in, then it's probably time for a new 'larger rack' anyway... I always leave enough room at the top of my rack for 'at least' a single rack space 'grill cover' to allow warm air escape, :thumbsup: Cheers!