Harrison Labs FMOD Inline Crossover Pair 200 Hz Low Pass RCA

The effectiveness of this product is dubious, at best.Go with a more expensive subwoofer crossover by Rolls or JBL.

Used to actively bi-amp speakers. Made amp incredibly more efficient. On a side note, you do need some knowledge in how amps and speakers work to properly size your crossovers (and a good ear doesn't hurt). You may also need to try other sizes and/or combinations to get the sound curve you want.

I bought these to see if it would be worth bi-amping my speakers. From a positive result, I later replaced these with an active crossover for the added features it provides. The FMODs performed as expected (I can't attest to the absolute accuracy 200Hz roll off).The only issue is that they fit VERY tightly on the amp's RCA jacks and required significant twisting and pulling to remove them. So much so that, I was concerned about damage to the amp's RCA connections. On some of today's cheaper amps, especially those with cheap cases that flex, the removal force could compromise the amp's RCA connection. My amp was OK.

These are a great functional option and work as expected. Simple design, easy to use alternative to a crossover when all you need is a low pass.