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No more subwoofer flutter! KAB RF1. This device really works.

ceylon said:
groovy.

have u built either of those by any chance?
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thats what I'm using. In theory it should hit -3db at 18hz based on the values used, but its actually -3db about 21hz. That could be measurement issues or accuracy issues with the signal generator but either way its low enough that its below where anything useful is happening.

works well though, I can't tell when its on or off other than the sub doesn't bottom out if I forget to mute it when starting a record. I screwed up a little bit when picking my RCA jacks and doing the initial placements. I had to re-drill the case and shove the filter board forward by the small fraction of an inch that remained to make it fit. Can't really tell unless you flip it over and find the extra set of holes, but whatever. Its fed from a AC wall wart that I got for a buck.

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gadget73 said:
thats what I'm using. In theory it should hit -3db at 18hz based on the values used, but its actually -3db about 21hz. That could be measurement issues or accuracy issues with the signal generator but either way its low enough that its below where anything useful is happening.

works well though, I can't tell when its on or off other than the sub doesn't bottom out if I forget to mute it when starting a record. I screwed up a little bit when picking my RCA jacks and doing the initial placements. I had to re-drill the case and shove the filter board forward by the small fraction of an inch that remained to make it fit. Can't really tell unless you flip it over and find the extra set of holes, but whatever. Its fed from a AC wall wart that I got for a buck.

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man that is so cool!
 
by coincidence I recently ordered an HL FMOD 30Hz high pass, I'll add my experiences once they arrive
I placed the order when I noticed the run-in/out tracks on some discs making the woofer flutter wildly

my previous speakers were all sealed boxes and/or were less sensitive to sub-sonic frequencies
 
ok I got the Harrison Lab FMOD 30Hz Hi Pass active crossover replacement 12DB per Octave filters in the mail and I can't recommend them for my intended purpose (act like a subsonic filter in an integrated receiver)
they did effectively reduce woofer flutter with inaudible frequencies from warped records
but they also muffled high frequency sounds, all of the snap and sizzle was gone -- the fast impact of a drum stick on the drum head before the bass note, sharp vocal consonants etc everything we softer and the volume level was reduced.

it was worth $30 to see if they would be a cheap solution, and I'll hang on to them in case I need tame a subwoofer or if I have a speaker with separate woofer and tweeter inputs.
 
beekeo said:
ok I got the Harrison Lab FMOD 30Hz Hi Pass active crossover replacement 12DB per Octave filters in the mail and I can't recommend them for my intended purpose (act like a subsonic filter in an integrated receiver)
they did effectively reduce woofer flutter with inaudible frequencies from warped records
but they also muffled high frequency sounds, all of the snap and sizzle was gone -- the fast impact of a drum stick on the drum head before the bass note, sharp vocal consonants etc everything we softer and the volume level was reduced.

it was worth $30 to see if they would be a cheap solution, and I'll hang on to them in case I need tame a subwoofer or if I have a speaker with separate woofer and tweeter inputs.
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yea maybe itll come in useful. i sure dig the hlabs attenuators
 
No wait! I found this post from @gadget73 and realized that my installation between the turntable and the phono preamp was the problem.

Shifted the filters after the phono preamp and it sounds good now. I’ll need to check both my most warped records for woofer-pumping dead wax
Well… now I need to test the vinyl against the digital file and figure out if I should have bought a 20Hz filter instead, might have lost the low kick

gadget73 said:
The Harrisons are passive, so they'd have to sit between the phono preamp and the main amp. Can't use those between the turntable and amp. Should be able to use them in the tape loop though.

The one I use is an active filter built on an Elliott Sound Products board that I put in a cheap case from Amazon. All DIY type stuff, which I realize not everyone is into. Active filters are much sharper than passives though, and response under 20hz falls off a cliff with that setup. I'm sure others exist, I just have no experience with any of them so I won't offer any opinions.

honestly if you feel like taking a trip across the bridge sometime, I can loan you my subsonic filter to see if that makes it behave. I can see Delaware City from my front door.

Might be worth investigating whether there is a hardware solution first though. Cartridge compliance mismatch, mechanical noise in the table, that kind of thing.
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yeah between the turntable and phono input the loading will get very funky with those. Need something with a sufficiently low source impedance that it won't screw up.
 
I have both the HL passives and the KAB RF1. The HL filters lasted about a week in my system, with sound degradation similar to what others have described previously in this thread. .
The KAB unit does what it says on the box. It just works. And, most people will never even notice that it's there.
 
I'll keep listening to the HL filters, give them a week or so on a variety of albums then switch back, see how I feel before I order the 20Hz
after shifting them to downstream of the phono preamp, I'm only noticing that the percussive feel of bass notes is reduced, and that's my fault for choosing the 30Hz filter instead of the 20.

but I'm also pondering if/when I'll order the updated mani preamp that includes a subsonic filter (mine is ~2 years old) or investigate a different phono preamp that includes a filter
 
Adding this device between the phono preamp output and the amplifier input does not alter the capacitive load (in pF) seen by the cartridge, correct?
 
It is always best to do as much at the source, meaning flat and centered records, tonearm type and last filter.

Below is Moerch UP-4 vs DP-8 tonearm where the DP-8 outshines the UP-4 when it comes to reduce the resonant peak.
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The RF-1 adds to this with lower noise below 100 Hz

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gadget73 said:
used properly a rumble filter ought to be transparent, except possibly not seeing your woofers / subwoofers pump.

if it dies out in mono I'd wonder if its not some mechanical resonance causing the arm to wobble back and forth a bit. Summed to mono that sort of thing would cancel since the wobble would produce an out of phase signal.
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Could well be that.
 
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