Rumble Filter - the little KAB RF1 - a hidden gem!

Mike

Mike

Audioshark
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Apr 2, 2013
Messages
30,484
Location
Sarasota, FL
With all of the tables/arms I’ve had in my room, I’ve struggled with rumble. My spongy subfloor is likely to blame.

I’ve tried everyone from SRA platforms to isolation devices. Nothing worked.

I recently added this little product and it’s a God send. Completely fixed any hint of rumble without any sonic degradation. I did multiple A/B’s with it in and out of the system. Even the subsonic filter on different Phonostages I tried had only a modest impact.

No, I don’t sell it! I bought it and yes, I will happily endorse it!

KAB Electro Acoustics http://www.kabusa.com

If you’re on a concrete slab, you can ignore and count yourself among the lucky ones!

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Were your cone speakers moving back and forth because of the rumble and now they aren't?
 
mep said:
Were your cone speakers moving back and forth because of the rumble and now they aren't?
Click to expand...

Yes. I have two tables, three arms, and they all did it. I have four dual 15 subs in a 14 x 22. The floor is a sponge.


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Mike said:
Yes. I have two tables, three arms, and they all did it. I have four dual 15 subs in a 14 x 22. The floor is a sponge.


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Click to expand...

Awesome this little rig solved your issue without any effects on the SQ! My listening room is similar to yours in that it is built on the top floor of the house. I'm lucky that I don't have any rumble issues.
 
mep said:
Awesome this little rig solved your issue without any effects on the SQ! My listening room is similar to yours in that it is built on the top floor of the house. I'm lucky that I don't have any rumble issues.
Click to expand...

Yes, works perfect. You’re lucky.


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Since January I've I struggled with turntable setup in a spare office room. Springy floors, walls, small size -- the works. And I listen loud, which makes everything exponentially worse. The KAB filter is the "easy button" solution - you put it in, and "most" problems go away. It won't cure skips caused by footfalls but at least it will protect your speakers from getting thrashed in those cases. Low frequency feedback can be deadly for the woofers by causing extreme excursion (flapping) and bad for the tweeters because it can push your amps into clipping (which can sound like a record surface pop, but way WAY louder).

Because footfall skips still bothered me, I kept at it and arrived at a combination of: 1) bracing my rack (a CMS Sotto Voce) firmly against the wall (with an Auralex 2'x2'x2" foam tile of all things) and 2) Townshend Seismic platform under the turntable (Clearaudio Innovation Wood) and 3) liberal application of hockey pucks which seemed to help at least a little where ISOAcoustics Oreas / Gaias, Herbie's gliders, and the CMS spike cups failed. My speakers and rack are now spiked directly into hockey pucks!

There was no single solution that worked. It had to be the right combination of elements. BUT it's now finally solved, to my great satisfaction. I can play without worry at ANY volume. The rack bracing alone made a huge difference. It you've got a tower rack and a nearby wall, try it. I didn't try a wall mount but believe this solution is superior because it combines the strength of the wall and floor -- plus it has no weight limits. The Townshend mops of any remaining energy, but of course costs money. Unfortunately, every room will be different so there's no turnkey solution for everyone.

I've also got a CMS Black Platinum filter atop my Sotto Voce. It does great work from the midrange on up, but it's not effective at absorbing the low frequency, very high displacement energy in these scenarios. The same would go for HRS, or SRA, or any other audiophile platforms. The Sotto Voce is a nice rack with great rigidity, but it doesn't have nearly the mass required to suppress the ripple shockwave from footfalls. But then I'm not sure even a Maxxum would work, in this particular room (Maxxum works great in my loft with better floors). The wall bracing finally allowed the Sotto Voce's rigidity to shine.
 
Here is what Wikipedia says about rumble.
Rumble (noise) - Wikipedia

Turntable design is a factor. Also it looks as if similar devices were developed and have been in use for over 45 years and some phono preamps may already have the circuitry internally to take care of this problem.
 
nicoff said:
Here is what Wikipedia says about rumble.
Rumble (noise) - Wikipedia

Turntable design is a factor. Also it looks as if similar devices were developed and have been in use for over 45 years and some phono preamps may already have the circuitry internally to take care of this problem.
Click to expand...

I’ve researched this for years, I’ve tried many Phonostages with a rumble filter. None did what this does,


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Sure, rumble filters have been around for ages. The KAB itself has probably been around at least 25 years, judging by the ancient HTML page it's sold on lol. The question is the slope of rolloff versus how much you need. In my difficult situation, before isolation fixes, I tried 5 different phono stages (Herron, Hagerman Trumpet MC, Benz PP-1, two VAC's) and none of them made a dent in the issue. The filters incorporated into phono stages are generally mild. A 6 or 12dB slope and -1dB at 20Hz is typical (down only 7dB or 13dB at 10Hz). The KAB is much more aggressive at 18dB slope and -3dB at 20Hz. This means it will be down 21dB at 10Hz, which is where many cartridge / tonearm systems have their resonance.
 
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