Subsonic Filters: A Poll

orthobiz · « **on:** 21 Mar 2011, 07:20 pm »

There's a recent post about filtering. Instead of watching the subwoofer go crazy on certain LP's, I've typically left the subsonic filter on my VanAlstine preamp engaged.

Haven't seen a poll in a while, maybe we can "settle" this right here and now!

Paul

BobRex · « **Reply #1 on:** 21 Mar 2011, 08:43 pm »

Record clamps, vacuum systems, and the like negate the need for a filter. Besides, neither my phono stage (Herron) or my line stage (Joule Electra) offer it.

cstory · « **Reply #2 on:** 21 Mar 2011, 08:44 pm »

My Meridian 101 preamp (use it just as a phono pre amp these days) has a built in subsonic filter and no switch, so I have no choice, it's always on.

DaveyW · « **Reply #3 on:** 21 Mar 2011, 09:21 pm »

I've had my Sansui amp over 25 years.
In that time I've used it with 6 turntables, somewhere around 50 carts and four pairs of speakers.
I've never had any reason to hit the subsonic filter button.
Cheers
Dave

Wayner · « **Reply #4 on:** 21 Mar 2011, 10:08 pm »

If you need a filter, you have some issue, IMO. Platter not square to the stylus will make the stylus "roll" from side to side in the groove, resulting in woofer pumping. This is not azimuth, but rather bearing adjustment being skewed out of wack or (perhaps more correct) platter and spindle have an error with each other. Another cause is from the insistence of many here at AC to not use platter mats. This invites mechanical noise (which is usually in the lower fundamental frequencies) and is a total distraction from the music source.

Wayner

BPoletti · « **Reply #5 on:** 21 Mar 2011, 10:18 pm »

In many classical recordings from "the golden years" (particularly in some of the Reader's Digest gems and London recordings), there is significant low frequency that is either 1) part of the performance, or 2) incidental noise that is part of the venue (traffic, subway, air handlers, etc.). In both cases, for me it is desirable to reproduce the nuances of the performance in it's real space even if it is very low. If the lf is related to the cutting process, that's a different matter. That's just bad recording, but fortunately it seems pretty rare.

I agree that if a filter is needed, there are likely some system issues that need to be addressed. Typical woofer pumping is more often related to a table that need help, feedback from the system, poor table mounting, footfalls or other external source. It's better to fix the problem than to filter it.

TheChairGuy · « **Reply #6 on:** 21 Mar 2011, 10:27 pm »

+1 for BPoletti's post above.

It is a band-aid for other shortcomings in your set-up a lot of the time...however, it is often indispensable in aiding the recording/record itself that is plagued with out of bank low frequency crap in it.

It's best to have as an option to hear and use it as you see fit...but precious few phono preamps today are designed that way anymore.

John

SET Man · « **Reply #7 on:** 21 Mar 2011, 10:42 pm »

Hey!

With 18wch SET I don't I want to waste my power to see my 6" Single Driver speaker moving for nothing.

Luckily my preamp of which is an Audio Note M1 Phono got built-in sub sonic filter in the phono stage section. I don't know what frequency is set at but it work well.

Anyway, I'm sure some purist won't like this sub sonic filter thing. But I think it is more useful than not. Yes, I agreed that it would be nice to have option to turn it off and on on the fly if you run into some record that needed.

Take care,
Buddy

BPoletti · « **Reply #8 on:** 21 Mar 2011, 10:57 pm »

Oh, I don't think you need to be a purist. Just one that appreciates the entire performance including the nuances of the venue.

orthobiz · « **Reply #9 on:** 21 Mar 2011, 11:14 pm »

I've been messing with my tables recently. I will have to look more closely. Seems to me some records pump and flutter a lot, just the subwoofer that i am looking at. Other records don't at all.

Maybe my setup is awry...and it's often in the lead in groove so I thought it wasn't a table issue, seemed to be less between songs.

Hmmm....

Paul

SET Man · « **Reply #10 on:** 21 Mar 2011, 11:17 pm »

Hey!

Purist as in less stuff in electronic circuitry is what I meant.

I think if the subsonic filter is set way below the lowest note of the full organ of which is 16hz I think. With that you can still hear all nuances of the record.

Unless you want to enjoy the first few hertzs than subsonic filter would be a bad thing to have.

Take care,
Buddy

Wayner · « **Reply #11 on:** 22 Mar 2011, 12:45 am »

Subsonic filters are not a brick wall. In worst case they have a 6db per octave slope, others 24db. So they are in your face at frequencies like 20-30 hz or more. On other threads, we have folks worried about phase linearity, and this seems to me to be the first step in non-linearity. Search to find the mechanical problems before finding answers in electrical problems, problems that have dire consequences.

Wayner

Quiet Earth · « **Reply #12 on:** 22 Mar 2011, 02:01 am »

Well, I'll be a monkey's . . . .

I took a quick look at the manual for my phono pre and sure enough, it says "Subsonic filter roll-off: 20 Hz". I forgot that I was using a subsonic filter because there is no switch to remind me. I guess if it sounds good it is good, filter or no filter.

I voted for always because for the last 4 or 5 years I've been using one without even thinking about it.

You learn somethin' every day.

BPoletti · « **Reply #13 on:** 22 Mar 2011, 02:35 am »

Quote from: Wayner on 22 Mar 2011, 12:45 am

Subsonic filters are not a brick wall. In worst case they have a 6db per octave slope, others 24db. So they are in your face at frequencies like 20-30 hz or more. On other threads, we have folks worried about phase linearity, and this seems to me to be the first step in non-linearity. Search to find the mechanical problems before finding answers in electrical problems, problems that have dire consequences.

Wayner

+1

Delta Wave · « **Reply #14 on:** 22 Mar 2011, 04:15 am »

I have 2 records that go nuts, one an old London and the other an old RCA. Other than those 2, I have never needed one.

felixscerri · « **Reply #15 on:** 22 Mar 2011, 05:20 am »

G'day all, based on personal observation, record warp is probably the largest contributor to 'woofer pumping' and that has very little to do with whether the general set up is good or poor, in my opinion.

My experience is that 'ported' speakers are the most adversely affected by record warp induced woofer pumping. Regards, Felix.

orthobiz · « **Reply #16 on:** 22 Mar 2011, 02:17 pm »

The answers here have made me go back and look at this a bit more analytically. I have a TT shelf that I have not used because of the way my twin tower shelves stand between the speakers. I am amazed at how much the woofers pump if I bump the TT or the stand. Then it quiets down tremendously.

So maybe it's a combo of warp and vibration. Right now the low filter is off. We need more votes...the "ay" and "nay" votes are kinda close, especially when you add the "don't have it want it/don't want it" categories.

And I need to bite the bullet and mount my wall shelf!

Paul

blakep · « **Reply #17 on:** 22 Mar 2011, 11:22 pm »

As Felix has noted above, a good subsonic filter is pretty much a necessity for anyone spinning vinyl with ported loudspeakers (like me).

Believe me, there are 1) no problems with my setup ($6k worth of table, arm, cartridge and phono preamp very well set up with the table on a Target Wall Mount using a custom constrained layer shelf) and 2) the subsonic filter is completely inaudible. Actually I shouldn't say it's inaudible because IMO it improves the sound quality in my setup.

If you've addressed the issue of proper set up, including proper tonearm/cartridge matching relative to effective mass and compliance, ported speakers are still going to give you problems with woofer pumping in a vast majority of cases as a result of both minor record warps (there really are not many perfectly flat records) and subsonic information that has actually been cut into the groove. The clamp on my Gyrodec is very good at "flattening" most records with minor warps and creating a good record/platter interface, but the subsonic filter is still a necessity for me.

I've used the KAB subsonic in the past and it is a very good and extremely transparent subsonic filter and the subsonic filter (switchable) in my Aqvox phono preamp is -9dB @ 10 hz, -18dB @ 5 hz and -48dB @ 2hz. If anyone can hear that, they are a better man than I. As with many things audio, it is about the implementation. Clearly, there may be lesser subsonic filters or those that are poorly implemented that negatively affect sound quality. Mine is not one of them.

Having woofers pumping needlessly and having your amplifier struggling to reproduce absurdly low frequencies that are either inaudible or not even part of the musical performance is not a good idea, particularly if you value your equipment or your sound quality.

neobop · « **Reply #18 on:** 23 Mar 2011, 01:10 am »

Looks like the poll is pretty evenly divided. If you're experiencing subsonic problems, a "good" filter is a great fix. The conjecture about its not having negative consequences, along with the subsonic cure, is impossible to defend. The entire signal goes through that filter. How could it not degrade?

Acoustic feedback can be a contributing factor. It's not just isolation from footfalls that are a consideration. How is it that some people say they never experienced a problem, while others say a filter is mandatory with ported speakers? That said, I have 2 preamps with a switchable subsonic filter. I believe the -3dB point is 18Hz on both. In my main room, I don't have one. If I switch in the filter I can hear it. It's like switching in tone controls, without applying correction. It's really not that bad.

Acoustic feedback is a problem with record players. If your table is in the same room as the speakers, and you listen to big scale recordings at realistic volume, you're likely to have some sort of problem. Maybe you only have a problem with a couple of warped records. But it seems that those lucky enough to find a location for their table, that's relatively immune from both physical and acoustic feedback, have virtually no problem.
neo

Elizabeth · « **Reply #19 on:** 23 Mar 2011, 02:21 am »

I voted no. i really never have had problems over many years of Lp playback with very different systems. Starting in 1965...

Poll

Do you use subsonic filters for vinyl playback?

Subsonic Filters: A Poll