Bi-amp cab configurations

[calypsocoral302]

Hi all,

I just read the threads about mixing different cab formats, so now my eyes are bleeding as I post this...

... anyway, I'm wondering about bi-amp rigs-- the 4x10 + 1x15 seems to be the most common configuration. I'm wondering if anyone has tried it with a 2x15 instead of the more standard 1x15, and, if so, how has it worked for your sound?

[Son of Bovril]

Bi-amp if you really want but I think you will have better results just using both cabs full range. A decent 410 will generally produce better low end than a 115 anyways. by bi-amping you will essentially lose half the capabilities of each cab in favour of a debatable gain in clarity..

IMO you are better off finding a cab designed with a three way crossover like the Fearful designs etc. otherwise just go for a full range rig of the same type of speakers ie. two 410 cabs

what is your reason for wanting to bi-amp?

[tom-g]

The Fearfuls are designed for both biamping and/or for use with a crossover.

[lbwdog]

Unless there is an absolute need to bi-amp, I suggest using your cabs full-range. Virtually all bass guitar cabs these days are designed for full range.

For a true, effective bi-amp system you'll need a cab to handle lows only (115,118,215, etc. no tweeter) then another for mid to highs (1x6,1x8,1x10,etc. w/tweeter). Also required would be an external, active crossover plus two power amps and a preamp, or a head that has this all built in (such as a G-K 800RB). Problem is, finding dedicated cabs for this purpose.
Most commercial 4x10s actually have stronger low end than most 1x15s.

Imo one of the best designs is a fEarful type cab with a 15"+ 6.5"+ tweeter, and a built in passive crossover. Separate inputs and a switch to remove the xover from the system will then allow you to run it bi-amped.

First question I would ask myself is "Why do I need to bi-amp?"

edit: LOL, son & Tom beat me to the wire while I was typing!

[bgavin]

The primary reason for bi-amping is separating the band so each driver works in its optimal range.
This prevents bass frequencies from overloading the high frequency drivers.
It also avoids wasting HF energy in a woofer that cannot produce them.

Another reason for frequency optimization is beaming.
A 15" woofer begins to beam above 250 Hz.
For wide dispersion, this is the upper limit for the 15".

The typical 6" driver begins to beam above 650 Hz and is fully directional above 2700 Hz.
A 2" dome tweeter begins to beam above 1700 Hz.

3-way configurations are common in the HiFi world where sound quality is paramount.
Limiting response to a dome tweeter limits the overall system loudness level.
Sounds good... but doesn't make a lot of noise. Ask the Acme owners.

The problem with passive crossovers is the huge size and huge expense for 250 Hz or lower frequencies.
Active crossovers used in bi-amping have 24dB/octave or steeper slopes.
This is VERY pricey with a passive crossover.

A bi-amped system with active crossovers is immune to impedance mismatches at the drivers.
You can add a 2nd 15" cab to the LOW side and not disrupt the crossover characteristics. Not so, with a passive crossover.