New Sub XO - Page 3

JensRasmussen · 18th December 2005, 09:11 AM

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

JensRasmussen · 18th December 2005, 05:52 PM

Also come to think of it I would use equal Rs and Cs and adjust the Q via the gain in the filter.

This makes component selection simpler.

\Jens

amplifierguru · 18th December 2005, 11:31 PM

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

amplifierguru · 22nd December 2005, 11:45 PM

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

Workhorse · 22nd December 2005, 11:51 PM

NICE Works Babe....

sagarverma · 24th December 2005, 05:03 AM

neat

amplifierguru · 24th December 2005, 05:36 AM

Thanks Kanwar and Sagarverma,

now all I have to do is package it in a block of machined Rhodium.

Merry X'mas to all
Greg

HiFiddle · 14th March 2006, 03:37 AM

Does anyone know if this crossover design is available or has built it?

It's not showing on Greg's website but should be a good match with his SKA amps.

22nd December 2005, 11:51 PM	#25
Workhorse diyAudio Member Join Date: Dec 2004	NICE Works Babe.... __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

24th December 2005, 05:03 AM	#26
sagarverma diyAudio Member Join Date: Feb 2005 Location: NEW DELHI	neat __________________ Never Underestimate The Bandwidth of A Station Wagon Full Of Magnetic Tapes Hurtling Down The Highway...................Andrew S Tanenbaum

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18th December 2005, 09:11 AM	#21
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	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

18th December 2005, 05:52 PM	#22
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Also come to think of it I would use equal Rs and Cs and adjust the Q via the gain in the filter. This makes component selection simpler. \Jens

18th December 2005, 11:31 PM	#23
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	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

24th December 2005, 05:36 AM	#27
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	Thanks Kanwar and Sagarverma, now all I have to do is package it in a block of machined Rhodium. Merry X'mas to all Greg

14th March 2006, 03:37 AM	#28
HiFiddle diyAudio Member Join Date: Feb 2006 Location: Qld Australia	Does anyone know if this crossover design is available or has built it? It's not showing on Greg's website but should be a good match with his SKA amps.