Because I could not download a specific plugin due technical reasons for beefing up my Kickdrum with a resonant lowcut (LC) filter I tried numerous others and found SWEEP the finest sounding of them all.
For those who don't know the technique: a resonant filter does not only cut the frequencies above/under a specific point but also emphasizes them at the given cut off frequency. That said, if you lowcut eg. your Kickdrum at 50Hz all frequencies below will drop rapidly in amplitude (=getting quieter) according to the slope that has been used which is the main task of a LC filter: getting rid of the unwanted low frequency stuff. But another thing happens if you raise resonance slowly: all your frequencies around 50Hz will be emphasized until the filter starts selfoscillating which results in a brutally loud sinewave. So beware not to turn up resonance too quickly or otherwise you can damage your ears and speakers. For safety reason unexperienced producers should use a brickwall limiter with proper settings at the end of the chain to minimize damage.
Anyways, the timbre of the resonance is pure gold. Via the drive knob and setting the "Q range" from safe to full ( CAUTION !!!!!!!!!!) the resonance sounds so sweeeeeet. Exactly. Lots of "eeeees". I tried numerous others and I liked some of them but nothing came even close to SWEEP.
If you missed the 2013 xmas giveaway from Waves (RBass for free) or could not download "Bark Of The Dog" from boz Digital Labs (which is free also) or if you are just looking for another nifty tool with a certain tmbre then SWEEP is highly recommended.
I give it 9/10 because its free and has a really great sound, clear layout and is a joy to use. Like all the other products from this dev. They have some real "Soul".