New Sub XO

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Hi,

Why is it that a lot of manufactures insist to have only one SUB channel?

I know that surround systems only support one SUB at the moment but since the stereo signal sometimes has a large low frequency content differing in the left and right channel I think it is time to start working on stereo set of subwoofers.

I enjoy watching films with stereo and surround sound. But I find that the low frequency content is better represented when I use my stereo setup with the TV-monitor placed in the middle of the stereo speakers.

Why not make a filter where the both options are available? maybe this is already possible my means of different stuffing guides?

Also I would add a 100 ohm series resistor on the output of the board as there is a risk of shorting the output to ground.

I would make an off board PSU and use the extra space for more filter options.

\Jens
 
Hi Jens,

Yes, a single SUB channel seems to be in vogue on the basis there is no directional info in bass < about 150Hz, so a single amp can be used, albeit at extra power, for some economy.
If this is true then a centrally positioned single channel SUB out should be fine.The associated directional info ( >150Hz) would be
redirected by the XO to the respective main outs.

I have a Rout provision on the board (which can be 100 ohm). I didn't include it in the sime snapshot schematic posted as floating components aren't tolerated by the sim.

Yes a more elaborate unit could have the PSU on another board but some of it's Zout would be lost in the remoteness.

I think with so many variations possible, even, in this simple cct, keeping equal C's and unity main channel outputs, then varing the filter characteristics and SUB gain with simple low cost R's is the way to go. Imagine varying gain to vay Q, you would have interactive controls and gain all over the place.

I have since optimised values for the unit for -

-3DB 15Hz to 120Hz -6 dB (L-R ) for the SUB (covering 3 octaves).
and -6 dB (L-R) at 120Hz to 3MHz - 3 dB for the mains.

input Z is 10K output Z is 47R.

Cheers,
Greg
 
And here's the finished PCB - double sided with full top layer ground plane and through hole plated.
Just waiting to be populated with crossover frequency and filter characteristic determining resistors.


Cheers,
Greg
 

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