Are subsonic filters important?

Really good post.

 

I my room I have little choice but to have my TT next to my speakers, Salk Soundtowers. In some cases woofer pumping may be due to poor speaker design but I doubt that's the case here. I had this problem and install the KAB filter. Problem solved and in A-B testing I can hear no difference in the audible sound at all. The only other solution I would have had is to move my system components to another room and run longer speaker wire, which would have been very inconvenient, so I'm glad this worked out.

 

Yup

 

Here is the problem. Below the low frequency response cut off frequency (35Hz in the case above), the acoustic output drops at 12dB per octave, but the amplitude of vibration becomes flat. So in fact as far as the driver is concerned it see the rumble at full whack.

Suggest you read around a bit about how low frequency drivers work; it has been known since the 1940's and is not rocket science.

Elements of Acoustical Engineering, Harry F Olson, 1940
Electroacoustics, Frederick V Hunt, 1954
Acoustics, Leo L Beranek, 1954

And later, Richard Small's seminal papers in JAES in the early 1970's.

 

I can do Haiku by the way. but Limericks are more fun to make up:

"A subsonic filter named Macon
was cleaning up bass that was shakin'
The dirt from this filter threw sonics off kilter
and made noises like frying bacon."

How's that?

 

I got rid of my subsonic filter by resolving isolation issues with the turntable. My KAB subsonic filter now sits in a drawer unused and unneeded. Good riddance to it. Using it was a compromise and negatively affected sound quality. Of some 3500+ LPs I have one that has rumble issues in the pressing itself.

 

Brain fart there, have modeled many drivers using WinISD and knew that, down in there somewhere. Won't need to read all the literature for the moment, little dry, but thanks for the correction!

 

Personally I´d rather much use a fluid damper than a subsonic filter.

 

I could see it being important if your system/setup needs it, but I’m good without one. I briefly tried a pair of inexpensive high-pass filters, and they seemed to roll off higher than intended, which I did not like.

I have a KAB fluid damper on my tonearm, but even before adding that I never saw woofer pumping (and I was looking for it). My turntable sits very close to my right channel speaker and within four feet of my subwoofer, yet I get absolutely no feedback, no pumping that I have ever observed. Perhaps I am just lucky, or perhaps Technics simply makes turntables that solid. I do like the idea of cutting below, say, 12 or 15 hz like some of the examples mentioned in this thread, so I would be open to checking one of those out, but, in general, I like the sound of less filtering.

 

Agreed! Even KAB, who makes the high quality subsonic filter praised by so many on here states clearly on their website:

In summary fluid damping does the following:
1. Attenuates peak amplitude at resonance.
2. Actually reduces the stress the cantilever sees riding up and down a warp.
3. Eliminates queue skipping at the beginning of the disc.
4. Reduces the sensitivity of the tonearm to external vibration.
5. Subjectively increases detail retrieval.

Damping has no effect on the Arm/Cartridge resonant frequency. It does not change the effective mass of the tonearm.
A good electrical analogy would be the onset of oscillation in a crystal oscillator. Study this and you can understand how damping merely changes the "Q" of the tuned circuit. Since damped resonance has a wider, less pronounced peak, it's frequency may appear to move slightly when compared to the before damping measurement, but it really has not changed at all.

The resonance issues are less of a problem with stiff cantilever suspensions because the stiffer the suspension, the lower the peak output at resonance. But the advantages gained from #2-#5 above are still beneficial to any cartridge design.

"Fluid damping offers benefits that cannot be achieved any other way. It is a necessary component of a hi quality tonearm design."

https://www.kabusa.com/damping.htm

 

that's just not right
subsonic filters - or "rumble" whichever you prefer - were installed on very fine equipment for decades
the whole industry didn't execute on such and involved circuit just to accommodate lacking in loudspeakers
but even if they did - doesn't change the fact that there is a very real need - and reason - for having and using a subsonic filters

 

Yeah, it isn’t magic. I wouldn’t expect you could just disregard cartridge/tonearm matching. It also certainly doesn’t make warps disappear, and I could see it still being beneficial to filter out subsonic frequencies if you’re going to play a lot of warped records. But I do prefer the idea of starting with a mechanical solution, and filtering the signal only if necessary.

 

because it's (the KAB device) a processor of sorts and not a passive filter
it is doing what it does after the fact - downstream, after the pre-amp (or phono stage)
not the same as the executions/implementations used by makers like Accuphase, Kenwood, Pioneer, Marantz and a 100 others
that KAB processor is also an active device as you obviously already know
I personally would only use one of those (the KAB box or similar) for 78 archiving and even then judiciously
Michael

 

Leave off unless there is an issue such as excessive cone flap.

 

I have a Iron Maiden-Powerslave 2014 Euro LP reissue with surface (oiled looking) pressing problems. i still have it because i use the lp to test subsonic filters. Playing this lp without filter the bass speaker wobbling is easy to see and i can check if the filter is also affecting the bass on the music. also the lp is good to test the arm/cartridge damping

 

For needledrops are not important. Rumble can be removed after recording with a good sound editor. For the classic analogue audio systems I think is important to reduce the LF noise.

 

The KAB is the most transparent filter out there IME.

DB Systems DB-12 filter is also an active unit. If there is a better way, I'd bet Hadaway would know it.

 

KAB is a good outfit - my point was only to explain, possibly, his complaint
nothing is more transparent than passive though
KAB doesn't sell junk
Michael

 

I've had passive filters in my system and they were far more detrimental. DB Systems offers both passive filters and an active unit, the active unit being the more transparent.

 

so?
I thought I was clear that I'm not debating/arguing this with anyone
My reference was to well designed filters that came in the amplifier from the original manufacturer and that's where it ended for me
from people who know/knew how to do it like Accuphase and KENWOOD
the "but what about" game is a losing one
everyone likes what they like, I mean cool
I'm not into outboard add on anything from anybody as far as signal processing of any sort goes (generally speaking)
and definitely not active
the only reason I use an active phono stage is because I use Denon 103s and don't want to get into the transformer thing (and my stage is chip based so it's quiet)
I'm happy you dig the KAB! : - )
Michael

 

My Accuphase phono amp has a rumble filter. I never use it as there is no need if one use a fluid damper. A rumble filter is what it is, but it doesn´t make the distortion lower.

 

Hey I'm not unhappy with the KAB.
It is the ultimate tool for removing rumble through cancellation algorithms AND processing AND filtering.
It is the most heavy duty bass rumble cone flap remover known to man...
It works great at totally cleaning up poor mastering groove rumble, floor shake, airborne bass and just about magic if you are being attacked by deep bass problems like the plague.
However it is pretty strong medicine if all you need to kill is mild floor bass feedback or groove rumble.
The alteration due to how it works is because it sums both channels into MONO below 150hZ PLUS it subtracts channel cross talk noises in the bass.
Or something.
Actually I have no idea HOW it does all this, somebody smarter can explain it better.
But when you NEED all this---get the KAB!
I can't explain how some audiophiles on here with dual subs CAN'T hear it working!
I hear it the second it is engaged.
I prefer to keep it ready on my switchable tape loop and only use it for drastically problematic situations as I can HEAR it working.
I would rather hear music!

 

The KAB has been in my system since before I acquired two subs, and I haven't bothered to do any comparison switching. I'm sure it's summing of the bass is why the bass gets so much louder when I listen to vinyl, but it doesn't really bother me. I still get good imaging. I'd probably notice it more if I listened to the same albums on both digital and vinyl. I run my subs in stereo but some claim it's better to run dual subs in mono anyhow for smoothing out bass modes. Bass tightness did improve a fair bit with the KAB.

 

I have dual subs and using it made things worse.

I solved my rumble problems by improving my TT isolation, and upgrading my tonearm. My previous arm had a magnetic bearing that included damping adjustment; however, it was ultimately the source of my problem causing woofer pumping. While it is a great arm it is unsuitable for my installation. I upgraded to a better arm that uses high precision ball bearings. That completely eliminated any need for a rumble filter, so now my KAB goes unused in a drawer.

 

A big part of the reason I sought to resolve my rumble problems at the cause is because using the KAB negatively affected bass definition, tightness/speed and soundstage. It made things sound worse.