fmod inline subsonic filter?

I am fixing to be replacing the two old pioneer 12's in my truck with 1 Sundown 8 in a ported box tuned to about 35 hz. The guy at the stereo store said I have to run it on an amp with a subsonic filter. I think he was just trying to sell me an amp, but I am very happy with my old school Pioneer GMX-922. Problem is he said without the subsonic filter the woofer would tear itself up trying to reproduce the ultimate low notes.

So with all that said has anyone had any experience with the inline subsonic filters like the ones in the ebay link? This way I can get a couple passive inline subsonic filters and still use my old school amp. http://www./itm/1-Harrison-Labs-FMOD-30Hz-Hi-Pass-Subsonic-Filter-Rumble-Reducer-RCA-USA-/390911171831?pt=US_Speaker_Parts_Components&hash=item5b041f1cf7

What amp are you running now. A lot of amps have the subsonic HP built in. The FMOD filters work great. You might want to consider the 20Hz HP filter so you don't lose too much bottom end - depending on your music prefs (i.e. if you listen to decaf, rap, hip-hop) I would get the FMODs. No need for a new amp if the one you have matches the power and impedance requirements of the new sub.My DIY Project Canvas is a 2012 Honda CR-V EX AWD

I'm running and old school Pioneer GM-X922 amp, it doesn't have a subsonic filter. Nice to know the FMODS will work, I appreciate it.

I have not recently looked at that product. In the past they were a 6dB per Octave device. If that is still so, I would think about looking into a 50Hz or so high pass. A 6dB per octave device is not real great at protecting drivers in a ported enclosure. Going up to a 50Hz device will be 9dB down at 25hz. The roll off is so gradual that with it being 3dB down at 50 you will not notice much of a difference till it gets down to 40 or so.

Looking on Parts Express it says the FMODS are 12db per octave. (see link below) Still glad to know they'll do what I need them to do. The other option I was looking at was one of the cheap knock off versions of an audio control epicenter. Those have subsonic filters built into them and I thought about maybe going with one of those, but the FMODS seem much simpler. LOL http://www.parts-express.com/harrison-labs-fmod-inline-crossover-pair-30-hz-high-pass-rca--266-248

I have used them in the past with great results.2013 Kia Rio -90a alternator

DDX470HD GTO14001 GTO1014D (x3)

Big3 in 1/0G

1/0G to GTO14001

I did end up going with the 30Hz set and they do work great. I'm very happy with them. Thanks