Crossover between pre and power amp for sub

[nile]

I'm trying to figure out what exactly I should be doing in this situation. I am using a NwAVguy Objective2 headphone amp as my pre-amp, and my NAD reciever as a power-amp. I have some bookshelf speakers at the moment but will be getting some new ones soon (if speaker impedance matters?). I also have an active sub that has it's own adjustable crossover (up to 80Hz). I am looking for something that I can put after my pre-amp that will send a signal to my sub, as well as provide a cut-off so that the bookshelf speakers aren't trying to drive low frequencies that my sub can do (partially to reduce stress to the speakers). I presume I should be building a passive crossover for this purpose?

 

[pantstain]

i suppose something like this would work if the subwoofer is a DVC sub Cerwin Vega Sub Woofer 200 watt Crossover

 

[nile]

Thanks for the reply. I don't believe it's a DVC sub (as it only has a single line input and 2 wires leading to the driver itself?)

 

[pantstain]

yeah thats not a DVC then if there is only 1 set of hookups on the driver. not sure how else to go about it...but its very late here...if i think of something ill post again

 

[pantstain]

Not sure what else we can do (that I can think of).....does your subwoofer have its own amp or is it powered by your receiver? If it isn't a powered sub it might be easiest to get a plate amp for it and run it off of your LFE output of your receiver. That would eliminate it from the chain wof your bookshelf speakers and solve the issue (if I'm understanding your setup correctly)

oh and then a simple passive crossover could eliminate the lower frequencies from your bookshelf speakers

 

[sofaspud]

I think this recent thread starter sought the exact same solution:
x'over for a sub?

 

[nile]

Pantstain, my sub is active with it's own filter and my reciever is being used soley as a power-amp. I think the thread sofaspud linked was quite relevant however it seems that the OP of that thread had a DVC sub? I think I need a way to get a mono(?) sub line out of the stereo line out of my pre-amp. Then simply a passive filter/crossover to cut out the low frequencies going into my speakers? Thanks for the consideration and replies.

 

[pantstain]

Yeah I'm not really sure.... but I did see a thing the other day surfin the web who knows where...but it was a module that converted 2 signals (from a stereo amp) and allowed them to be bridged (even if the amp wasn't bridgeable). But as to where I found it or how it would affect the audio signal I'm not sure

 

[sreten]

Hi,

One (or two) method(s) :

Reduce the power amplifiers input coupling caps to high pass the satellites.
(You can use external series caps wired into the phono plugs.)

If the preamp can drive the cables to the sub simply split the output cables.

(If it can't - my pre-amp lost too much quality driving the long sub cables :
From the power amplifier speaker outputs design attenuators for the
subwoofer line inputs, include in the attenuators a reverse low pass
passive filter that corrects the the roll-off off applied to the sats,
you can't do this to DC, so pick a low frequency like 10Hz.)

rgds, sreten.

 

[nile]

Thanks for the replies. srten, I am not sure how this would work as my sub has a single line in, not stereo? If I use input caps for a high pass filter into the power amp for the speakers, then I could [somehow?] design something to get the stereo line and feed it into a single line for the sub and let the sub controll what it's crossover point is (it has adjustment on it's own amp).

 

[nile]

I found this circuit which has a 200hz cut for the high and low pass filters, is it as simple as changing some capacitors from the shown values in the schematic to lower that down to 100Hz or 80Hz cut? Subwoofer filter - Electronic Circuits and Diagram-Electronics Projects and Design