In-line crossover needed

Kevin_W

Second Unit
Joined
Jun 22, 2000
Messages
261
I am trying to implement a passive subwoofer configuration into my bassment rig and I was handed a surprise today. My old work horse pioneer receiver passes a full range signal out the sub output.

Are there any inline crossovers that will only allow 80hz or so and under to pass? Something like the Harrison FMod would be nice, but I'm not sure if they are what I need. Look at this link and tell me if this would work. I guess I'm just not sure what that 12db slope does. I want clean unadulterated 80hz and under to pass and without any -12db/octave attenuation added.
Thanks in advance
 

ling_w

Second Unit
Joined
Sep 3, 2001
Messages
426
I don't even know how that is suppose to work, since for any type of passive crossover to work, the input impedence of the device it is connected to has to be factored into the equation in order to know what the crossover frequency is. If your input impedence is off by 5x from what the FMOD is designed for, the crossover freq would cross over either 5 times too high or too low.

This looks like some dirt cheap stuff used mostly for car subwoofers setups. But since it looks like you have a dirt cheap setup, you might not have too many other choice.

A better choice is an active crossover, but that might run much higher in price.

Anyway, 12dB/oct on the unit means at 80hz, it should be 3dB down, 15dB down at 160hz, 27dB down at 320hz...
 

Saurav

Senior HTF Member
Joined
Feb 15, 2001
Messages
2,174
I want clean unadulterated 80hz and under to pass and without any -12db/octave attenuation added.
You have to have some dB/octave attenuation. You cannot have everything below 80 Hz go through and then bam, nothing above 80 Hz gets through - that is physically not doable, as per the laws of physics (or electronics). Well, for splitting hairs, you could do it in the digital domain, which would involve digitizing the signal, then re-converting it to analog, and so on.

There's a $75 active crossover kit that I built which sounds pretty clean. I use it in front of my subwoofer. It has the advantage of letting you play with the frequency and slope (dB/octave) until you get the best blend between your speakers and your sub. Search for "John Pomann" on these boards, the thread should be here somewhere.

For a passive XO, ling_w is right, the values need to be chosen based on the input impedance of the destination (amp) component.
 

chung_sotheby

Supporting Actor
Joined
Apr 8, 2002
Messages
857
I fi were you, try to find a used Pardigm x10/20/30 module., These are pretty popular, and they are very coustically invisible, They are great little prices, and have settings for high pass crossover, low pass crossover, vlume and phase. Nice little pieces, gong for about $30-120 used, depending on the model
 

Kevin_W

Second Unit
Joined
Jun 22, 2000
Messages
261
Thanks for the good info guys.... gonna follow up on those leads.
Anyway, 12dB/oct on the unit means at 80hz, it should be 3dB down, 15dB down at 160hz, 27dB down at 320hz...
Duh! Gotchya... i was thinking the attenuation was happening the other way... kind of like it was designed for a midrange driver rolling it off 12db/octave starting at 80hz going down.
 

John H

Second Unit
Joined
Nov 27, 1998
Messages
472
i was thinking the attenuation was happening the other way... kind of like it was designed for a midrange driver rolling it off 12db/octave starting at 80hz going down.
That would be a "highpass" crossover circuit. Allowing the highsto pass and rolling off the lower frequencies.
 

Allen F

Grip
Joined
Mar 18, 2002
Messages
15
Audio Control makes a unit called a Phase Coupled Activator (PCA), which can be used as a crossover. It comes with a 90hz built in xover, but you can supposedly get different resistor packs for it in a variety of frequencies. I picked one up from ebay for $100.
 

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