We have now up-versioned this board to v1.4 and added several new features: 

   
Description: Two-channel (stereo) Linkwitz-Riley 2-way active crossover filter with single sub-woofer output (PCB only).
Manufacturer: KMTech Design (UK).
Configuration: Circuit board only, no components, buyer must assemble, instructions included.
Noise-Cancelling  Method: Option for balanced differential-mode input.
Crossover  Frequencies: User-definable by changing resistor values.
Filter Gradient: 24dB/octave.
Operation  Amplifiers: 6 x OPA2134 op-amps or compatible(not included).
Power Supply  Filtering: Ceramic/electrolytic noise bypass capacitors.
Power Supply Type: 12v 1000mA "wall wart" or dual 5V-0V-5V DC to 12V-0V-12V DC.
Transformer Type: Recommended 6VA dual-voltage toroidal.
Filtering caps: 33nF polyester.
Port configuration: Two inputs, three outputs.
Power Connector: 3 Way 5mm terminal block for dual supply. 5.5mm x 2.1 mm PCB-mount DC socket for single-ended "wall wart" supply 
Input Signal  Connector: 3 Way 5mm terminal block.
Output Signal  Connector: 6 Way 5mm terminal block.
Physical  Dimensions: 100mm x 100mm x 1.6mm.
PCB Mounting: 4mm mounting hole each corner.
   
A high performance active crossover filter by  KMTech Design. This crossover filter is designed to run from a dual DC supply OR a single 12V supply. Please note for single supply use you will need a low noise "wall wart" of 12V and min 1000mA with positive tip.  . 

How it works.

The 2 x inputs are both filtered into 2 x low and 2 x high frequency channels. The 2 x high channels output via terminal blocks. The 2 x low channels are mixed, and exit the device via a terminal block for the sub-woofer. 

CIRCUIT BOARD ONLY, SOLDERING SKILLS REQUIRED!
Let us know what crossover frequencies you need  and we will get as close as possible by suggesting resistor values. The default crossover frequency is 125 Hz, using 27k resistors.
For your information, the formula for  calculating the filtering resistor values is:
R = 1 / (8.89 x C x f)
Where R = resistor value in Ohms
f = Desired crossover frequency in Hertz
C = 0.000000033

***You don't need to worry about the maths! We will do all the  calculations for you! Happy to help!
Please note there is no enclosure included with  this product, it is as shown in the first listing photo.

Components needed to complete this product:

6 x OPA2134 ultra-low noise dual audio grade op-amps or compatible.
6 x 8-way IC sockets.
5 x 5mm 3-way terminal blocks.
2 x 100k resistor (all resistors 1/4 Watt, metal film 1%) for unbalanced input.  
2 x 1k resistor for unbalanced input.
8 x 10k resistors for balanced input
3 x 20k resistors
20 x 27k resistor (for filtering, can supply different values depending on required crossover frequency).
3 x 100 ohm resistor.
3 x 6mm trimmer potentiometers.
6 x 100nF ceramic capacitor.
2 x 47uF electrolytic capacitors
20 x 33nF polyester capacitor.

FOR WALL WART POWER FEATURE:

1 x 5.5 x 2.1 PCB mounted DC socket.
2 x 2w 2.54 pin headers and jumper straps.
2 x 10k resistors for PWR2 potential divider sub-circuit.