Are subsonic filters important?

If you want to see if you have ULF (ultra low frequency ... say 3-15 Hz) energy in your vinyl output, just do a needledrop straight from the phono preamp into your digital recorder, and look at the waveforms. Audacity has a spectrum analyzer so you can figure out where the resonances are; I recommend recording the lead in and lead out grooves - you'll likely see more wobbling at the lead in.

You may get the filtering within the phono preamp - which would lead you to the incorrect conclusion that you have a wicked awesome setup that is immune to rumble; my phono preamp has a switch that turns it on, but I turn it off because I don't see problems with my system (filtering must be occurring elsewhere). Also, if you are using the IEC RIAA curve you are getting (some) rumble filtering whether you think you are or not. From RIAA equalization - Wikipedia :

Assuming there is no explicit or implicit high pass filter in the preamp, what you see on the Audacity screen is what is being fed into your line-level preamp. It is possible at every amplification stage that there is implicit or explicit high pass filtering... I suspect my SVS subwoofer has a built in rumble filter because I never see the cones flutter like I would expect with vinyl.

Every needledrop I do, FYI, gets a 20Hz HPF (the DeNoise LF software, made by the same guy who wrote ClickRepair). It's the kind of HP filter that does not mess up any of the phase for higher frequencies - that's my main concern with putting any filter in the audio signal path. I think preservation of phase is what makes a good system sound great.

ULF energy can really rob your amp of power - you don't want it arriving at your speakers, you really don't.

 

You're confusing frequency response with an undamped driver, a total oversimplification of speaker behavior.

 

Ok, doesn't change the fact that your speakers have a lot of cone area producing the bass, thereby reducing the required excursion for a relative SPL.

 

Just to clarify, this is one my pair of dual concentric loudspeakers
Follow the link and you'll find details.

 

This is a two way speaker system - don't be fooled by the number of drivers.
I do not have pair of these.

 

The reality is that most inexpensive TT setups can benefit from a subsonic filter - the higher end setups are less likely to need one, or at least not all the time. That's why you tend to see more of the lower cost phono preamps with the subsonic filter feature. Heck, the $299 Cambridge Audio Duo has a built-in, non-defeatable subsonic filter, (-3dB@12Hz 6dB/octave) mainly because they know that the market who would be buying a phono pre at this price point probably has a TT with setup issues and this is a really easy way to make the purchaser happy. The subsonic filter is a highly effective way to address the rumble without having to actually fix the most likely root of the problem. This makes sense...for folks in this range of the market they probably would rather just apply the bandaid, get good sound, and be off on their merry way. For me, I'm squarely in the camp of fixing your setup first, then use a filter only if needed. Higher-end phono stages like my Herron VTPH-2A I believe partly address the issue of not needing a subsonic filter because they apply passive RIAA equalization for accurate phase and amplitude response with no inductors for maximum emf noise immunity.

 

Gotcha, I thought you were referring to the latter speakers. I didn't think those looked anything like dual-concentric drivers but that term is often misused. Even so, a ported speaker is a ported speaker is a ported speaker - it still has potential for uncontrolled mechanical excursion below the port tuning, unless there is some filtering up the chain.

 

Huh?
Why raise subjects not being discussed as though THAT makes you RIGHT and me WRONG?
Are you trying to deflect from the issue at hand?
Please point out where ANYBODY (but YOU) was talking about frequency response versus undamped drivers...

Damped (sealed box) OR undamped (slot/line/port/open baffle) has a LOT to do with speaker "flapping" on deep out of control bass excursions.
The less your woofer cone is damped the more it can "flap."
These "flapping excursions" can be due to floor shake or airborne bass notes OR baked in groove rumble.
I have carefully set up my monster system to AVOID these issues.

My table is totally isolated from floor and bass shake.
100% inert. OK maybe only 99.99999% as i haven't tried to blow it up yet..just hit 105dB continuous for a half hour.
My arm is tracking below 9hZ without boosting any groove rumble.
My 2800 watts RMS of undistorted power does not oscillate.

Cone "flap" is typically an order of magnitude WORSE with an undamped speaker cone that makes large excursions---like my Velodynes.
My undamped slot tuned Velodynes move up to an inch excursion at 16hZ!
They can actually loosen my floor joists if I am not discrete about using them.
I am saying I see no "flutter" or "flap" on the Velodynes when playing vinyl.
No flutter from either rumble OR deep bass feedback loops---PERIOD.

In the last year I have engaged my KAB rumble filter exactly TWICE.
Once due to some obvious deep rumble cut into a poorly mastered record.
Once because the digital recording had unsurpressed rumble baked into the signal from who knows where...

Can't you just accept that others do not share your enthusiasm for rumble filters being engaged at all times?
In my experience ANY band-aid fix is wrong.
Band-aids and filters can degrade your sound real fast.

Go fix the setup FIRST.
Then you need band-aids a heck of a lot LESS.
Let it go, my friend.
I happen to KNOW what I am talking about.
I am the Doctor of all things HiFi.
This is my LIFE.
Can't we just be friends?
My two cents.

 

Almost a haiku...

Maybe try rap music, you could call yourself DJ Hifi.

 

I've been right up to the vertical array speakers when they've been pushing out serious dBs, and never seen any movement. Not even the tiniest of excursions.
There is what appears to be a complete lack drama, but obviously there must be some movement, otherwise there would be silence.

The DCs have a similar lack of visual drama about them.

Both just get on with playing music

 

You are the SECOND commentator to say I write in Haiku.
I HAVE studied Eastern Philosophy and Zen Buddhism to a greater extent than some have.
It was my major at one time.
Now I just adore the beauty of the natural world.
And my feeble attempts at "HiFi" are my way of putting this natural beauty into my own living environment.
The roaring power of an unrestrained Philharmonic Orchestra at full tilt still makes my toes curl up in ecstasy.
But I digress...(as usual).
Life is beautifully strange in my opinion.
Gosh I love music, don't YOU?

 

As far as digital music with ULF energy, if I recall correctly, the album Trinity Sessions by the Cowboy Junkies has a fair amount. Listen to the lead in to the first song, when it fades in there is something rumbly. I think the whole album has a bit. It was recorded in a basic way (in a church, and I think around a single microphone) with no filtering or mixing etc.

 

In playing certain albums, I can look over at the Zu, Omen Definitions, with their exposed drivers and see the them pumping vigorously. They don't make any sound, but the excursion of the drivers during the "pumping" is very noticable.

On other albums, you don't notice them pumping at all.

 

We can be friends but doesn't change the fact that your speakers are still susceptible to woofer pumping (and avoiding woofer pumping is the whole point of this thread) if ran full-range. It doesn't matter how your system is setup unless there is a high-pass filter somewhere upstream, either in the phono preamp or elsewhere.

 

Yes, with a vertical array, there are many woofers sharing the bass load, therefore they move less for a given bass load than single woofer speakers. The movement will be especially low in a ported speaker as the port is producing a large portion of the bass above the tuning frequency. Below the tuning frequency, anything goes, as long as it's loose. While a speaker may not produce much below 40Hz during a pink noise measurement in an anechoic chamber, it is under different conditions when playing ambient noise that was never intended for the mix. It will respond to high-amplitude subsonic noise, otherwise, one would never see woofer pumping in a ported speaker, never.

Even if a particular album has subsonic noise cut into the grooves, the relative (key word) woofer pumping of a line array or multi-woofer speaker will be far less visible than that of a single woofer speaker. But it's all relative, so even though it may not be obvious, the relative distortion is higher than it would be with a high-pass filter engaged.

Now, one might only have one out of twenty records with a subsonic noise problem. Is that person going to examine the woofers for pumping, with each of those twenty albums? No, more likely, the person is going to notice zero pumping for a handful of records and assume their system is immune to this issue.

 

Mine cuts at 15 hz and it's always ON.

 

My speaker covers are always off so I'm pretty aware of woofer movement. The only time I notice any movement that appears at all excessive is when first cueing up a warped record. This can be eliminated with an outer ring clamp. I will say when I first set up my TT I noted a little bit of woofer pump before realizing I had not completely filled my tonearm bearing cup to the specified line with bearing oil. The proper damping at the tonearm bearing was critical. Again, there may be instances where using a filter is unavoidable but the reality is a filter will introduce phase shift, and in a full range system, will be audible as less bass impact. You may never notice this in a less resolving setup that does not provide full range.

 

Isn't a mechanical filter via your tonearm damping just about the same as an electrical filter? Probably sounds better, I agree that some of the components used in audio electrical filters don't sound good, but a high pass filter is a high pass filter, whether it is mechanical or electrical.

 

I think the folks at KAB explain pretty well why your comparison isn't analogous. Mae no mistake, a phase shifting electrical filter degrades dynamics. Can we agree that it's better to prevent arm vibrations instead of letting the arm vibrate wildly and later filter out the noise electronically? Do you think the stylus is tracking well while it's bouncing?

All tonearms oscillate at the arm - cartridge resonant frequency. This causes the speakers to move in and out modulating the soundstage. Fluid damping stabilizes this behavior and brings greater stability to the soundstage. Your amplifiers are also over reacting to this very low frequency signal and that can cause even more problems.

It would be better if we could call this behavior "Dynamic Rigidity" for that better describes what is happening. Functionally when a tonearm reacts to the resonant frequency it produces a peak of output energy. This is seen as woofer pumping which is essentially the stylus over reacting to a small warp in the records surface. Fluid damping stops the stylus from over reacting. That is what is "damped". It all occurs at frequencies below 10 hz and has no impact whatsoever on audible dynamics. In other words, do not confuse damping of resonance with damping of dynamics they are not related in any way. In fact fluid damping enhances sonic dynamic behavior by allowing the stylus to follow the groove with greater accuracy.

Above 10 Hz the arm is seen to be even more rigid at any single point in time and as a result the stylus traces the groove with even more precision. The biggest sonic effect is to make the sound stage more "Still". This can be subtle to some, overwhelming to others. It all depends on your listening priorities.

In summary, reproduction is more lifelike with damping then without.

 

I have stereo subs in my system - plenty of low end reinforcement, and even with my rumble filter installed the bass is quite a lot stronger what I get with digital. Not all rumble filters are based on simple caps.

 

They are.

 

There are four effects.

The first is true warps, which are at the record rotation speed (or harmonics thereof). In other words at 33 1/3 rpm at 1.8Hz, 3.6Hz and possible a bit of third harmonic at 5.4Hz. These are at lower frequency than the main cartridge/effective mass resonance at 8Hz to 11Hz. They still cause stylus scrubbing because they are on the tail of the resonance. The only way of dealing with the direct audible effects (ignoring speakers) of stylus scrubbing is to use either a damper near the arm pivot (SME), or a trough further out (Townshend), or a damper at the cartridge (Shure V15 IV and V). Or a combination.

The second are vinyl ripples, which are at a higher frequency, and cannot sensibly be filtered out electronically without severe loss of low bass.

The third are footfall coupling to the deck and arm. The solution to that is down to deck siting.

the fourth is acoustic feedback. Deck siting and support structure is the only way around this.

Leaving aside the direct sonic effects of warps, there are several electronic ways of dealing with warp signals and stopping them getting to the speakers. It matters not whether they are reflex or sealed box, and how well they are "damped" (whatever that means) - there will still be significant cone movement from warp signals, which always gives rise to distortion ( Frontiers and https://www.klippel.de/fileadmin/klippel/Files/Know_How/Literature/Papers/Loudspeaker Nonlinearities_Causes,Parameters,Symptoms_06.pdf )

The first is an electonic filter. The problem is designing one that is fast enough fall off to stop warps getting through without having an effect on low bass. If you use something with a fast roll off like a third order Butterworth or Tchebychev , you get phase distortion in low bass. If you use a third order Bessel (which is linear phase) the fall off is more gradual, so you get amplitude distortion of low bass. There is no solution that is not a compromise.

The second is to use a cross-feed filter. This recognises that warps are vertical, and hence the L and R warp signals are antiphase. Now for low bass, the ear has no directionality - so you can sum L and R for frequencies less than say 50Hz, and the warps just cancel out without any effect on signal low bass at all. There is a commercial version of this (not my design) called the Devyniliser http://www.douglas-self.com/ampins/Paris 2016 devinyliser.ppt . I use this, and even switch it in sometimes for some CD's with the irritating ultralow frequency signals (as I said, possibly aircon systems in the recording studio).

 

If you have subs or woofers that go low, and/or you listen at high SPL, a high pass filter might be necessary. If you have bookshelfs or other speaks that naturally cut off substantially fast at 35hz or so, and especially if you listen at relatively low levels you could likely live a fine and satisfying life without ever having one of these filters.

 

So is that a “yes”?