adding filler woofer

I posted this on Analog Line Level but only got one response.
Maybe there's more interest in help <100Hz here?


"HIFI Electronical 2 Way Crossover PCBA ClassA Power Linkwitz-Riley filter 4-Channel Output Crossover-point 2.2K Hz Free Shipping"

I've bought two of these with X-O points at 80 and 100hz for use with sub-woofers for my single driver MTLT systems.

Having frequencies down to a measured 30hz adds a subtle but valuable fullness to some music.

I used MathAudio's free plug in for FooBar to flatten out the peaks in my systems.

Anyway... Has anybody done testing on these $30 active X-Os?
Does the design look OK?
'Seems too inexpensive to be true ... less than passive X-Oers.
Am I losing something by putting this in front of my amps?

I swapped the NE5532s with TI Burr-Brown OPA2604s. I imaged it tighten the bass.

Thanks, Mack
Last edited:
Since you were wondering... Here's what the low side of the XO produces:


and the 80Hz and above side:


I've removed the baffle step correction from the full rangerer and use the Mathaudio plug in to flatten the response, The horizontal line is the level the frequency level is set to.

Here's the measurement with both amps on:


As you can see the biggest improvement is removing the thumping spike in the sub-woofers.

Using the plug-in to fatten out the Fostex FF225WK drivers makes up for removing the BSC.

Cheers, Mack