Has anyone run these on a pair of active monitor speakers to remove the extreme low end? Like for 4" bookshelf speakers? Did it color the sound?

I use them on a pair of 5" active studio monitors. The sound is not colored, they removed those low frequencies that caused the extensive woofer movement and "bottoming out" of the woofers. I did add a subwoofer to the set to make up for the lost low end below 100 hertz. Actually I am impressed by their performance. Don't forget the connectors you will need to use them.

Are these good to get rid of engine noise in my door speakers? Thanks

Antonio assuming you're using these on the signal inputs of a car power amp, they will remove all low frequency sounds below 100 hz. That would remove most of the low bass notes from your music. Engine noise is more likely to be an issue of cable shielding and/or grounding of devices.

When plugging them in, are these directional?

I didn’t see any indication of direction on them. The direction I’m using is source audio plugged into the female side, then make side plugged into amp. I haven’t tried the other direction.

Cheap active sub no crossover, running off line out of power amp. Do I need high or low pass 100hz to cut off all signal above 100hz?

Running it off a power amp - yes you do, otherwise you'll get the sub trying to reproduce the whole range; 100hz low pass (black writing filter will work (FMOD Crossover Pair 100 Hz Low Pass ).

ASIN	B0006N41KG
Best Sellers Rank	#38 in Audio & Video Crossover Parts
Customer Reviews	4.4 4.4 out of 5 stars (67)
Date First Available	December 28, 2006
Is Discontinued By Manufacturer	No
Item Weight	1.44 ounces
Item model number	1
Manufacturer	Harrison Labs
Package Dimensions	3.25 x 1.65 x 0.16 inches

FMOD Inline Satellite Electronic Crossover Pr 100 Hz High Pass RCA

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