Mono sum cable or device?

[Phantasm]

Is there a cable or box that I can buy to Mono Sum two low-pass channels from my crossover into one input for my sub amp?

[agedhorse]

Balanced or unbalanced?

 

Generally, x-over outputs are very low source impedance, and the build-out resistors are around 75 ohms, so jusy using a Y-cable won't work well. The other problem is that you need to drive a long line (if the x-over is out front) so high value build-out resistors may affect noise pick-up and some signal loss due to both cable loading (not significant for a sub out) and amp input loading (more of a problem, but still probably not a problem).

 

So, if the x-over is in your amp rack, then using 1k build-out resistors in series with each signal line (1 for each unbal, 2 for each bal source) before the sum point will probably work.

 

Another far simpler solution is to just use one of the sub out channels unless you do some goofy stuff panning instruments w/ lots of LF information. Generally, for keys as an example, unless the patch is set up for split bass, the software sums the LF information to mono anyway. Also, I would generally recommend against panning things like bass and kik.

[Phantasm]

Balanced outputs from a crossover. THe problem is that the subwoofer out on the crossover is broken (thanks Behringer!) so I was going to try summing the low from channels 1 and 2 into a single feed for the power amp. Unfortunately, I don't see anyone selling a part to do this... I did find this schematic but I'm not Mr. Crafty with the soldering iron.

 

 

Would I do just as well to have channel 1's lows go into sub amp channel 1, and channel 2's lows into sub amp channel 2?

 

Essentially I'm trying to put off buying a new crossover, unless i really need to do it now.

[Unalaska]

Just use the channel 1 and 2 low outputs to their respective amps. Not my fav but you're kinda stuck. Time for a new xover though: DBX, Rane, anything but Behr.

 

p

[agedhorse]

Not sure why you wouldn't use the low outs of ch 1 & ch 2 to the respective amps? That's probably the simplest solution.

 

The combiner schematic is fine, but I would use 1k resistors rather than 475 ohm due to output current limitations of the line drivers used in typical MI crossovers.

[Phantasm]

Thanks for the good advice guys, I think I know where I stand now. Probably time to look at a new crossover, but in the interim using both low feeds will work.

[agedhorse]

You know, the mono summed "sub out" is a relatively new feature. Many units do not have this "feature".

[Audiopyle Sound]

If you ever DO need it, Whirlwind makes a balanced line level combiner:

 

http://www.whirlwindusa.com/comb.html

[tlbonehead]

Originally posted by Audiopyle Sound If you ever DO need it, Whirlwind makes a balanced line level combiner: http://www.whirlwindusa.com/comb.html

Welcome to the forum. Now we have more stuff to keep straight.

[agedhorse]

A line level transformer combiner (magnetic circuit summing device) will also work, but you need to use a very good transformer for this due to the possibility of low frequency saturation of the transformer's core.

 

The Whirlwind device should be adequate.