Unity free + buy filter , reverb etc ONLY (fmod)?

Hi, if i need only lp , hp filter, reverb, … (=fmod) in my game, is the only way: Buy Unity Pro$1.5k+ (iOS $1.5k)?
not real only for this feature $3k.

i remember there is a c# script for lp somewhere on the web. and hp could be something like hp = source - lp (im not sure here).
and there is a reverb in the free version of unity.