Home » Audio » Speaker » low pass/crossover and different ohms help
low pass/crossover and different ohms help [message #15769] Thu, 22 January 2009 18:34 Go to next message
Andrewskaterrr is currently offline  Andrewskaterrr
Messages: 2
Registered: May 2009
Esquire
OK so i have a the JBL Array 4893 sub. They are two 8 ohm subs and I have them wired together on a terminal so they're 4 ohm now. I want to buy a cheap crossover for them. I found this one

http://www.amazon.com/Eminence-PX-250-Pass-Crossover/dp/B000BBS5PU/ref=sr_1_1?ie=UTF8&s=electronics&qid=1232663219&sr=8-1

It's the cheapest crossover I could find (if you know of a cheaper way please tell me). This is at 8 ohm. So I would hook this up to the terminal to connect it to the subs. Now my amp is at 4 ohm and i plan on bridging the sub (2 ohm) so this is what it would look like.

amp crossover subs
2 ohm--->8 ohm---->4 ohm

So my questions are: 1. is my math right? 2. will this work? 3. the crossover freq is 250hz, will this change?

Re: low pass/crossover and different ohms help [message #15770 is a reply to message #15769] Fri, 23 January 2009 12:25 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18691
Registered: January 2001
Illuminati (33rd Degree)

A passive crossover requires a specific load to work with. Too large resistance and it is underdamped, making a peak near the crossover frequency. Too little resistance and it is overdamped, making a shallower slope than expected. In either case, the crossover frequency changes. And since the woofer isn't resistive but rather reactive, other strange interactions occur. Most people add a Zobel filter to mitigate this, but that requires a large power resistor. I use a 100 watt resistor for Zobels on the woofers in some loudspeakers with passive crossovers, for example.

Why not run an active crossover instead? For subs, I think it's a better option.

You could even do something like this, with a 12V wall wart supply:

It's cheap and configurable. It will work just fine for you, I think. But it will require separate amplifiers for subs and mains.

If you don't already have an amplifier for the subs, you can either purchase a separate discrete amplifier or you might want to use a plate amp instead. It has the sub crossover built-in, so you won't need the crossover above if you go this route.


Re: low pass/crossover and different ohms help [message #15771 is a reply to message #15770] Fri, 23 January 2009 16:05 Go to previous messageGo to next message
Andrewskaterrr is currently offline  Andrewskaterrr
Messages: 2
Registered: May 2009
Esquire
i dont have a lot of money and im working with a powered mixer so i dont have a lot of choices. if i went with this

http://www.amazon.com/PYRAMID-CR-79G-ELECTRONIC-3-WAY-CROSSOVER/dp/B0002BEYTK/ref=sr_1_548?ie=UTF8&s=electronics&qid=1232740907&sr=1-548

how would i power it in my house, which is where im using it?

Re: low pass/crossover and different ohms help [message #15773 is a reply to message #15771] Mon, 26 January 2009 12:50 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18691
Registered: January 2001
Illuminati (33rd Degree)

Power it with a 12v wall wart. Same as the $20 sub crossover from PE I mentioned in my last post.


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