Mapman...A passive rumble filter would require large and expensive inductors and capacitors. And lots of them to yield the minimal 18 dB slope. Rumble filters are only practical for line level signals. |
FWIW, some speaker manufacturers build subsonic filters into their speaks as a way of tightening up the low end by filtering out low end frequencies that the speaks are not designed to reproduce accurately. That is another possible reason why some do not observe this phenomena on their system. It is a true statement though that it is inherent to the medium. For example, I believe Ohm does this with newer design speakers that employ their "sub bass activator" circuit internally. |
Here's an update. I bumped into Michael fremer. he suggested adding some Bluetac or Moretite to the headshell, effectively increasin the mass of the tonearm and changing the compliance. unfortunately this didn't change anything.
another suggestion was to take the TT off the rack and put it right on the floor, to see if there was some rack related issues. No dice.
Another friend, Wes Bender, has a VERY high end system (Hanson's, Redpoint TT, etc.) said he sees the pumping also, but figures it's just part of the medium and so ignores it. I'm afraid he's right and that some kind of subsonic filter would be the only real solution.
So, live with it or build a filter. Lets see what the New Year brings. There may be a project in my future.
Bob |
The solution I just got around to using is a good, and easy one, though somewhat expensive. I just a day or so ago changed the equalization from standard RIAA to IEC in my Simaudio LP 5.3 phono pre, which has the filter built in. What a difference! Needless to say, I recommend getting and using a subsonic filter.
Dan |
Maril,
Yes, it is a valid concern worth investigating. |
The pumping woofer does not just use up available amplifier power. It gives rise to "Dopler distortion" because the advancing and retreating cone is also reproducing higher frequencies, which are modulated by the cone movement.
Get a rumble filter. Cheap and easy. |
Mapman,
I posted a response earlier today, but for some reason it dissapeared.
My TT is essentially brand new, so I don't think it's the motor.
I suspect, that Shelter 501 MK II compliance is too high for the Technics arm, and that creates an unwanted resonance. Do you think, that's a valid concern? |
Yup it's the nature of the beast
My next phono stage will have an IEC Low pass roll off installed ..If I ever solve the woofer pumping for good I can easily reverse this by changing value of the caps
If the woofer pumping is excessive in the long run you can/will do damage IMHO
I will opt for the lesser of two evils and install a low pass filter |
Markpao,
Best to minimize it as much as possible through better isolation, clamps etc., in that large driver excursions from noise can cause damage more easily than otherwise, and it consumes power to produce noise that might result in amp clipping and tweeter damage sooner, , but it is normal, in lieu of filtering, to always have some of this present with records.
Its something to be aware of, keep an eye on, and manage, but not expect to do away with completely even with high pass filtering. |
Hello everyone, I also am experiencing, what I would consider, severe sub sonic woofer pumping. I hear no affect to the music and no noise whatsoever. It seams like many here are willing to just put up with it, which I have no problem with. Is anyone else here concerned about doing damage or premature wear and tear to your woofer and/or sub woofer from all that constant movement? |
Hi Mapman I re-read your post and saw "isn't" as opposed to "is" as I initally read it. Or something like that. And now that i re-read it........
Bob |
Hi guys, I guess you dind't see the smiley face after the "20 pound one square foot..."
Bob#1, if you can live with it ........cool. Dont worry about it! Why correct problems, that are not there?
Though I think for $30 give it a try! It will still reduce the amplification of said freq even though you do not hear them, most assuredly your amps are trying to reproduce them and using up available headroom and giving your amp fits. Whether or not you speakers are able to reproduce these freq..
I tried last night and today with the increase in weight of the tonearm mass, to change the compliance, to lower the resonant freq., and saw/heard no difference. That is not my "problem". At least one that did not "cure" mine.
Bob |
Simpler is usually better, IMO. I'm even bothered by the idea that I would need a step up device if I were to get a LOMC down the road. Somehow I wonder if any improvement over the 20X-H (a very good cartridge in its own right) would be lessened by the step up transformer.
Thanks,
Bob |
" I think I'm leaning more toward living with it than putting something else into the signal path that might negatively impact the rest of the sonic spectrum"
Sounds like a good approach.
I know the positive attributes of vinyl and analog is worshiped by many here, including me to a significant extent, but it is what it is, almost a form of antique collecting at this point, and like most things it ain't perfect.
It only bothers me when I have some old rare favorite record that has particular issues and can't be replaced easily, but in most cases, I can either find a decent fresh replacement that is better somewhere either on vinyl or CD. |
"Perhaps you would like them better if the came in a 20 pound one foot square box with a ton of wires and capacitors and resitors and tubes and...:)"
Isn't that necessary to qualify as high end? |
I have a Dynavector 20X-H cartridge on a Moerch DP6 red dot tonearm. Supposedly the correct tonearm for this cartridge (gotta love a Moerch, since you can buy and change armwands to match the compliance of the cartridge).
I was listening yesterday and, although there was some cone movement in the sub and woofer drivers, it didn't interfere with the music at all. I think I'm leaning more toward living with it than putting something else into the signal path that might negatively impact the rest of the sonic spectrum. Getting rid of this last little annoyance would not be worth compromizing any other part of the music.
Enjoy,
Bob |
Bob#1 said, "There's been a lot of talk about rumble and subsonics. How does one differ from the other?"
Subsonics is below 20hz and rumble is out of phase info above 20hz that is usually diminished by 40-50hz, though some lps have rumble up to a much higher freq., perhaps up to 100hz and even higher? And some have very little.
I don't know what is in the little filters. There cannot be much. Perhaps you would like them better if the came in a 20 pound one foot square box with a ton of wires and capacitors and resitors and tubes and...:)
I think the point here though would be to try them just to see if it affects your problem in a posative manner. Perhaps knowing that the little filters are not the best in terms of sonics. But if they do the job as intended a higher quality filter would be in order.
On the other front I spoke with my brother last night on this subject and his suggestion was to look into cartridge/tonearm compliance. I will work on this and post my findings. He suggested, after doing some research and calculations, that I add weight to my tonearm to lower the current calculated resonance of 14hz to 11hz.
Bob |
Maril,
I notice in your pic that the table sits close in from of on of the speakers. That may be a challenging location unless the floor in your listening room is extremely rigid, like a concrete foundation or such and same true for your stand.
If you can as a test , you might try locating the table behind the speakers for better isolation.
Unfiltered, on most good systems, most records will produce some movement in the woof and possibly the mid-range as well depending because few if any records are cut perfectly or are perfectly flat resulting in low frequency noise.
Relocating the table better and using a record clamp might be two easy things to try to reduce the effect.
Visible driver movement is often associated with the specific record itself. In this case, the patterns and magnitude of movement will vary from record to record.
If the problem is due to vibrations from the table motor system being picked up, I would expect little variability in pattern and magnitude from record to record.
If motor vibration is the source, it would probably persist the same regardless of tt location and specific record playing and this may require servicing of some sort for the table to fix if possible. |
There's been a lot of talk about rumble and subsonics. How does one differ from the other?
Another question about these little RCA filters - anyone guess what's inside them? They are sooo small there can't be much. The rest of the signal runs through them too, so I am concerned a bit.
BTW - I tried something a little different today. I think by now you've all heard of the Cartridge Man's isolator:
http://www.thecartridgeman.com/isolator.htm
I never liked the idea that it was squichy and compliant. Some time ago I tried putting a thin piece of EAR Isodamp between my cartridge and headshell and thought I noticed a difference. But I pulled it out again. Well this morning I put it back in and I can say that I think this makes a nice improvement in soundstage and smoothness of sound (Yes, I adjusted the balance and VTA afterwards).
Unfortunately it didn't cure any low frequency aberrations, but I do think it is going to stay. The good news (and you didn't hear it from me) is that you can contact EAR and they will send you free samples of Isodamp. It also works well under your motor as a vibration damping aid, or under any transformer in a power supply.
Enjoy,
Bob |
Mapman,
Thanks for your response. Yes, it is DD table, and I use Isoplat mat with cork backing. Driver pumping seems to happen only with the record playing, and with all types of record. As soon, as I lift up the tonearm, it stops.
Could that be an issue with the cartrige compliance mismatch with the arm? I have Shelter 501 MK II on silicone damped Technics arm.
Also stock Technics feet are replaced with Audiopoints. |
Maril555,
I'd start with the production quality of the record being played especially if the problem does not occur with the table running and no record playing or it is obviously variable from record to record.
If it is the table (is that a direct drive model?), maybe try a mat with better isolation. |
Hi Bob, I would most definatly go with the 20 hz filter, and I do believe 12db/octave cut is enough for you. Though my 20hz filter in the Marchand Basis is 18db/octave.
You do not want to start eliminating freq at 30hz. It is not necessary with todays great turntables and we DO want extension down to 20hz. Just not below it.
If the noise you are hearing is rumble, not subsonic, then a rumble filter is necessary. This is only necessary if you have stereo subs. Then you need to go to mono at a freq that eliminates most rumble which I believe (at least in my system) at 40hz. Some lps will still exhibit rumble above that freq, but they are far and few between and most is eliminated by the rumble filter at 40hz. A little higher is OK (up to 50hz, perhaps a tad higher). The Kab rumble filter which I believe was mentionend in this thread is set at 140hz. WAAAY to high, that is stereo there and includes voices instruments that would be mono'ed at 140hz and below, NO good.
With a 12db/octave 20hz filter you would be;
-12db at 0hz,
and -6db at 10hz,
and -3db at 15hz,
and -1.5db at 17.5hz.
With a 18db/octave 20hz filter (such as the one I employ) you would be;
-18db at 0hz
and -9db at 10hz,
and -4.5 at 15hz,
and -2.25 at 17hz.
A 30hz filter would get you -12db at 15hz and -6db at 22.5hz. You dont want that.
Bob |
Well, late for the discussion, as always.
It looks I'm having the same problem with my TT- woofers and even midrange driver pumping, start. with the lead in groove.
Subsonic filter aside for now, where do I start?
Cartridge?, TT support?, mat? subwoofer? |
Hey, those little RCA "Sub Sonic Filter pairs" looks cool, and may well be worth trying out for only $29.
There are 2 values: 20Hz and 30Hz. Both have a 12db slope to them - not very steep. So if I was looking for 3db down at 17Hz then the best choice would be the 30hZ ones, right? I mean, down that low on the scale a 12db per octave slope goes very slowly down.
I found a chart with note values on it, but it only goes to 27hZ: http://www.phys.unsw.edu.au/jw/notes.html
Bob |
Hi Bob, you could try these;
http://store.hlabs.com/pk4/store.pl?section=12
They are only $30 and would give you an idea of what would happen if you implemented a subsonic filter. I dont know the quality of the units or how they would sound. But it would give you a feel for a subsonic filter and an indication of what one would do for your system.
Please feel free to experiment with you tt/arm/cartridge and let me know if you come up with something that you think I should try.
Bob. |
Ptmconsulting... Your "beautiful analogue signal" has probably been generated out of a digital mixing consile :-( |
Ptmconsulting,
Not me, but I just thought it ironic that technically the most practical way to clean up a messy analog signal off a turntable were one so inclined might be to convert it to digital first before doing the processing.
The horror! The horror!
Still, DCS and other companies do some truly magical things in the digital domain!
Cheers! |
And why, in God's name, would one ever run a beautiful analogue signal from a turntable through anything digital, unless they were forced to upon pain of being drawn and quartered? :-)
I think I'll open a bottle of wine tonight and listen to something nice on the old-TT.
Enjoy,
Bob |
Ptmconsulting,
It hasn't been a burning issue for me either. It is what it is. You either live with it or there are ways to deal with it both physical (clamps, new records, CDs instead) or via signal processing (filters, etc.).
On the signal processing front, when it comes to dealing with complex signal processing issues like this, technically, a lot more can be done in the digital domain than in the analog, but it is a complex undertaking and not one I would recommend for the uninspired. |
I tend to agree with you Mapman. The less I have to put in the signal path the better I feel about it and the better the transparency/musicality. I would far prefer to find a mechanical solution that doesn't alter the rest of the sound, if possible.
If not, I could still be happy with my rig the way it is. This is not a burning issue, but just an investigation into options and potential solutions.
And in this economy I am less likely to get itchy fingers and spend $ on a trial and error kit that has zero resale value (unless, of course, I DO get itchy fingers after the holidays and need a project to keep me busy). |
Two good things (relatively) about low frequency noise playing records:
1) I find it less offensive during listening than high frequency noise
2) If you can see the woofs on speakers, you can be sure when it exists because you can see and/or feel it perhaps even easier than you might hear it. |
Eldartford,
I am in agreement with your perspective on these things. |
Rumble, due to turntable vibration or recorded in the vinyl has always been my second gripe about LPs, the first being HF surface noise. CDs have taken care of this problem.
Imagine my surprise to get a CD of theatre organ music (from Organ Stop Pizza, in Mesa AZ) which has what seems to be lots of LF noise. It took me a few plays to realize that this sound is exactly what you hear in the hall as you eat your pizza and drink your beer. It's the organ's air generation machinery. Once you realize that it is not a recording deficiency it ceases to be an annoyance.
In a similar vein, surface noise does not bother me when I play my LPs of Benny Goodman's 1938 broadcast recordings. Somehow it becomes part of that particular musical experience. |
"I say, why not put the filter in, if it is a problem. If you don't hear it, don't worry about it."
Agree. It's not illegal. If it works for the better for you, then you should do it.
BTW the other common negative effect I've seen with rumble and other types of low frequency noise, is that even if it is not audibly disturbing to someone , the fact is it uses up significant amplifier power to produce noise. This can result in the amp clipping and damaging the speaker. Ironically, the low frequency noise usually ends up damaging the tweeter first, at least in most cases that I have observed over the years. |
Mapman said, "I've seen or been able to feel (to the touch) unwanted low end woofer excursions in smaller bookshelf/monitor speaks I've owned in the past during record playback that on paper could not produce subsonic frequencies."
I say, yes, that's true but we are dealing with two different entities, though they may have the same mother. Subsonics is a different ball of wax from rumble.
Mapman said, "Despite having access to low in addition to subsonic filters available, my choice was most always to not apply low (high pass) filters that would also negatively impact the real music signal in that range of the audio spectrum.
Effective isolation, clamps, etc. are probably more effective ways of dealing with low end noise introduced during playback of warped records, etc. without impacting the music."
I say,I am so happy that that works for you, but it does not seem to be working for me or Bob#1. It seems to me that the more effective way is the two filters, for me. Without impacting the music.
Mapman said,"Low end noise, audible or not, is one of the inherent banes of vinyl.
That's just the way it is."
I say, why not put the filter in, if it is a problem. If you don't hear it, don't worry about it.
Bob#2 |
Bob#1 said, "I can say with some certainty that the woofer pumping is there on most LP's to one extent of the other."
I say, you are correct on your assesment.
Bob#1 said, "But my ears feel like they are popping on some, but not all, LP's."
Yep, no doubt some are worse than others and some have almost zero rumble, or less subsonic noise.
Bob#1 said, "If I turn the sub off on these I don't get that annoyance (my regular speakers probably drop down to about 30hZ).
Sure you are not reproducing it! But its still there!
Bob#2 |
If your record is warped or cut too poorly to deliver satisfactory sound, even with filters, clamps, etc., then you have two practical options:
1) get a better pressing of the record
2) buy the CD or digital equivalent if possible.
Unless the tt is not operating properly, that is seldom the cause IMHO.
Low end noise, audible or not, is one of the inherent banes of vinyl.
That's just the way it is. |
I've seen or been able to feel (to the touch) unwanted low end woofer excursions in smaller bookshelf/monitor speaks I've owned in the past during record playback that on paper could not produce subsonic frequencies.
This tells me that the unwanted signal was not subsonic, yet still undesirable in terms of reproducing unwanted low frequency noise often associated with record playback that one would ideally prefer to not exist.
Despite having access to low in addition to subsonic filters available, my choice was most always to not apply low (high pass) filters that would also negatively impact the real music signal in that range of the audio spectrum.
Effective isolation, clamps, etc. are probably more effective ways of dealing with low end noise introduced during playback of warped records, etc. without impacting the music. |
Hey Buddy-Bob 2,
I can say with some certainty that the woofer pumping is there on most LP's to one extent of the other. But my ears feel like they are popping on some, but not all, LP's. If I turn the sub off on these I don't get that annoyance (my regular speakers probably drop down to about 30hZ). It is most noticeable on the lead-in groove and 1st song or two, and less at the end of the record, but still there.
You are correct about the amp - less low frequency need means a more efficient presentation overall, helping both speakers and amp.
I don't have time for a new project right now, but I will probably get itchy after New Years and look at this possibility again. It also means adding another interconnect into the mix, since there's no room to incorporate this into an existing box.
Bob #1 |
Hi Bob#1, Keep us informed. Many times, people report a increased clarity to the music, as a result of removing unwanted cone movement (equals noise, wasted power from you amp and loss of control of the driver). And your amp will be happier.
You appear to have only one sub, so you are in mono at your crossover point. That would be your "rumble filter".
You now need to try a 20hz filter for the subsonics.
Albert had kindly offered to speak to me over the phone regarding this issue, but I think we should keep it in this thread so everyone can benefit. Albert if you have any suggestions or comments please post them here.
Bob#1, you are probably limiting your system if this is a problem in your system. It needs to be eliminated for your system to shine (if it is disturbing/loud enough). How you do it is up to you. Whether you can find a mechanical solution, adding a filter or roll off of your speakers low freq extension. All of these have benefit in not hearing rumble or subsonics. If you can live with a little "rumble" that is an option that is up to you.
My guess is it is not rumble (since you have a mono sub, OR it may be rumble that is above your crossover point!) so it is probably subsonics ie: below 20hz. And filters work very well for this.
You never did mention when you have this problem, is it at certain volume levels, LPs with low bass, certain records that otherwise appear quiet?
Of course there is one other problem that is not system related which I mentiond above, which is rumble pressed into the record. Some of this rumble can even be above 100hz. This you just have to live with, knowing that it is in the lp and not your system. But even this can be eliminated, with a filter. The problem with this is that you want to keep it stereo down to as low as you can. I think this means stereo down to at least 50hz or better yet 40hz. And these freq will do a very good job of elimininating most rumble.
Bob#2
We are not men , we are Devo
|
I received a reply from Rod Elliott on my questions about his filter (see below):
My question about using a lead acid battery or a laptop power supply: "The circuit is specifically designed to operate from a split (+/-) supply. While a single 12V supply could be used, I don't recommend it."
Op-amp related questions: "All the signal runs though the opamp all the time - there's no other way to do it. You can use any dual opamp that you like - despite its age, the NE5532 is a good choice, as is the OPA2134."
Gain related question: "The circuit is unity gain."
Thanks Rod. I will have to reassess after the holidays are over. I may try a few other things in the meantime. Maybe an experiment with resonance damping in the headshell just to make sure it's not a mechanical issue I'm having.
Thanks for everyone's replies,
Bob |
So I think I'm hearing what I kind of feared - that, given very good isolation, the final solution to subsonics lies in the signal path via a filter of some kind. I fear this because I would prefer to keep things as clean as possible. I fear this because I just know I will hear something missing in the top end, or the soundstage, or something like that that bothers me more than a little subsonic rumble once in a while.
I guess the only way to know is to try it myself. Well, I'm a DIY kind of guy, and the filter can probably be built for about $50 and a little time. I've got a few questions out to Elliott Sound Products about their filter and how I can implement it. I will share those on this thread when they reply.
Thanks,
The First Bob (#1 I guess, since I started the thread :-) |
Acoustat6...What you describe is ideal. All we could quibble about is the frequencies. |
Bob #2 (I like that! :-)), that is the measured natural roll-off of the horns. To further complicate things there is a +6dB gain with having two subs, or so I am told. But your reasoning is still valid and does explain how different systems may need different solutions. |
Hello, Bob and Dan, I believe we are of course looking at several different problems rolled into one. Turntable isolation, the turntable, system freq response, the recording/pressing, cartridge/arm compatibility etc.
Bob, most definatly it is not a "problem" with the Hagerman.
One of the things I see (and which Dan mentioned), in comparison with Dans system is that my system is 8db UP at 20hz as opposed to Dans which is down 6db at 20 hz. That is a 14db difference at 20 hz. This means my system is 4-5 times louder than Dans at 20hz! And my freq response is still climbing till 16hz (ie: 10db up at 16 hz, therefore perhaps a 20+db difference with Dans at 16hz). This is a huge difference and can certainly explain a need for a filter or for that matter not needing one.
Of course this does not address the question where does this "noise" come from. Though it may explain why some need a filter and others don't.
The other Bob,
Bob #2
|
Oh, great! Two Bob's. ;-)
Ptmconsulting, I think that at some point all you are left with is the groove thang and resonance from the table so there could be a need for an electronic solution for subsonics. I have my table sitting on two 1/4" aluminum plates that are bolted together. This plate sandwich is sitting on 3 Stillpoints. All of this is sitting on a 4" deep sandbox with granite shelf. Other than warped records I don't notice any problems.
But, as I said before, I am probably benefiting from the natural roll-off of my sub/bass horns. So maybe that answer's the other Bob's poll question. I don't think I need a sub filter at this point. Less is most always better, IMO.
However, I am open to trying it to see if I could benefit from using one. I'd probably shoot for a 16Hz cut-off. |
Bob (Acoustat6) - it seems that we both use a Hagerman Trumpet. This is a great phonostage but we both seem to suffer from a subsonic problem using this unit.
According to Jim H, he didn't limit bandwidth in any way, instead relying on the TT itself to provide the isolation.
2 questions:
- are there additional isolation solutions to eliminate this that can be implemented on the TT, like a constrained layer damped heavy sub-structure under the plinth, aka 1/4" Aluminum/lead/etc?
- is the problem inherently in the grooves where only an electronic solution would address it completely?
Bob |
Hello, I was the original poster in Alberts thread asking him about this. I had planned for a thread but PTMCONSULTING beat me to it:)!
I told Albert that I need a 20hz (subsonic) filter and a rumble filter at 40hz. I have stereo subs, they are stereo down to 40hz, below 40hz is mono and then the 20hz filter kicks in. This eliminats most of the unwanted noise.
My system consists of a Shelter 901 on a VPI TNT 3 with a Eminent Technology ET2 arm. A pair of Bent Audio step up transformers into a Hagerman Trumpet then into my electronics/speakers. The two filters are built into my Marchand Bassis.
A simple question for everyone reading this for an informal poll. Do you or do you not need or use a 20hz filter or a rumble filter?
Myself I use (obviously, need) a 20hz filter and a rumble filter at 40hz.
Bob |
Dan_ed and Fap...I am a strong proponent of multiple subs, but when playing LPs I have found summing of LF to be essential. Of course you can make a rumble filter which simply attenuates all LF, but why throw away the mono component which is relatively rumble-free? |
I wasn't that happy with the summing solution. Stereo subs have proven much better in my room. The bass is no longer boomy, LF details and directional clues are much better.
36 dB roll-off! That'll get the job done.
I'm curious about the phase issues mentioned on the page that Fab linked and wondered what some of you guys think. I was thinking of such a subsonic filter at the input of the sub's plate amp. My question regarding the low frequency phase variations with such a filter is this. If the mid-bass driver is feed by the line out of the sub's plate amp, would that alleviate any/most concerns about phasing?
Thanks |
