i have firewire 410 and bx5 m audio speakers but can't afford their sub woofer- can anyone suggest how to rout throug calkwalk 3 sonar a powered subwoofer
You would need to buy a crossover. This would allow you to plug in both your monitors and the sub and specify a frequency crossover range where the monitors stopped producing low frequencies and handed it straight over to the sub. Similarly, you should get a sub which allows you to roll off it's top end at a definable spot.
I haven't used this, but it is an example of what would do it for you -
most of the powered subwoofers come with built in cross overs which you can set the frequencies of your desire, since you have bx5 (small speakers) you may need to set it at 150 hz to let more frequency. A Samson is a great investment, sounds good and pretty decent price, http://www.zzounds.com/a--2676837/item--SAMSUB120A
Most cheap subs only have a crossover to define where the bass starts rolling off higher frequencies.
The standalone crossover I linked will define where the nearfields start rolling off their, (notoriously patchy), low end response. Granted, some subs have this feature also, but you normally pay for it.