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 |
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
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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
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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 |
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 |
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. |
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 |
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 |
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 |
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 |
Koegz said, "the "rumbling" or "pumping" is not, i repeat, not a part of the vinyl medium that we must live with!"
I say that's true, only if your system is not able to reproduce it. Then you have nothing to worry about.
Bob |
Hi Koegz, I was indeed suggesting that your system is not reproducing below 20hz and perhaps not even below 30hz.
Thats OK, no problem there, I am sure it sounds great!
Bob |
Hi Koegz, I am sure your system is capable of great sound, you will not get an argument from me there. And I assure you I am reading the same post.
I dont believe Bob#1s (ptmconsulting) issue is his tt, but the fact that he is able to reproduce these unwanted freq, whether they are subsonic (ie not heard) or rumble (pumping and audible due to its freq).
Whether this is due to his ablity to reproduce below 20hz (subsonic) at a significant spl level, or if it is from 20hz up (rumble) and his systems ability to play down to 20hz. Most assuredly both, but I dont know I am not there.
It could be a bass peak in his room which is accentuating his "rumble" problem at perhaps over a certain freq, say if he has a broad 10db peak over from 30 to 50hz.
Conversly it could be someones system is not able to reproduce 20hz and below for subsonics to be a problem. Or his system is not able to reproduce 20-40hz where rumble generally resides. As well as it could be that someone have a 10db bass null over the range of 30-50hz which is preventing them from hearing the offending rumble.
It could be that he has a very good in room response that is allowing his system to reproduce all of the noise produced on the LPs. Just as well as someone else may have a falling respose over the range that all of these problems occur at. Ie; a falling response from 50hz down, which is not at all that uncommon.
I too don't own any LPs that have music below 20hz, but all LPs do have noise below this freq, it is a systems ability to reproduce these freq which is the "problem".
You are pretty much correct that you "don't hear" these freq. Especially if you your system is not able to play that "low" or if your system can do 20hz and below, the question then becomes how loud do you listen.
I believe it has nothing to do with the type of music you listen to. Some LPs do have more subsonics than other LPs. As well as some LPs have rumble at a significant level as well. Some LPs have rumble that perhaps goes up to 30 or 40hz at a low level while others can have rumble that goes up to or even over 100hz at quite a high level, though that is rare. But is has nothing to do with the style of music.
Many of my LPs have close to zero rumble, or at least insignificant enough that it is not a problem. Though I always keep my rumble filter in at all times. Many of my LPs have rumble at a high enough level and freq, that it is an audible problem.
I believe that all LP systems would benefit from 20z (subsonic filtering). Regardless if your system is reproducing (audible) this sound or not. You do not even want your amps to be trying to reproduce this. And even a little bit in your speakers is not desirable. My 20hz filter must be kept in at all times.
I do not hear rumble on all LPs as well as Bob#1 does not hear rumble on all LPs. This sound is not coming from our tables, or we would hear it equally on all LPs when all of the LPs are played back at the same gain setting.
Your comment on the Groucho is nonsequiter to this discussion. Please tell me what you thought could be felt.
Bob |
Hi Bob, I agree, I too have some lps that have lots of low freq abberations (rumble and high levels of 20hz and below noise) and others I play are "close to perfect", very little rumble but the 20hz and down "noise" is there no matter what. This is the first thing you should address, as it does give your amp fits and also, even if you do not hear it it is screwing up your speakers sound trying to reproduce it.
Yes, if it is your setup it would be there regardless of the LP. You said subsonic pumping is almost gone with these LPs, what I believe you meant to say or are heaing is rumble (above 20hz). Correct me if you disagree. It can always sound better:)
My thought is that one can live with the rumble especially if ones system is down a a few DBs in the lower freq, but a 20hz filter will be of benefit to any system.
Bob |
Hi Bob#1, you said, "It is not audible on my speakers (which go down to about 30Hz I would guess, but due to the slope is probably still putting out into the 20's but at a lower level). The pumping on the....
Not to be argumenative or anything, but when you said "it is not audible", do you think your speakers can move without making sound or using power from your amps.... just something to think about.
I do think you are going in the right direction:)
Bob#2 |
Markpao said "I just received a pair of those 20hz FMOD RCA filters."
Did this help with your subsonic problem? Does it sound OK? Are you using them? Do you recommend them?
Bob |
Hi Markpao, you said "Yes, I did receive the 20hz subsonic filters and installed them at my pre amp out. There was no question that the woofer pumping was reduced, but not gone."
Dont forget that the 20hz filter will only reduce the freq below 20 hz at a rate as specified by the manufacturer (usually 18-24db per octave). It is not a sharp cutoff that will totally eliminate 20hz and below.
Also don't forget that you have not addressed the other side of this coin, rumble. Not turntable rumble, but record rumble.
Bob |
Koegz said, "let's see, subsonic filter, rumble filter how about an air filter? to bright ad a tweeter filter. mids not right add a mid booster filter. how about, system sounds bad, get a better system."
Hey koegz, no need to worry about a subsonic filter when your speakers (B&W 800D) are allready down -3db at 35hz and are -6db at 25 hz!! You allready have a built in subsonic filter.And rumble, just think how much less rumble (and music) you are missing when your speaker is incapable of much below 50hz.
Ponder that for a moment and when you get full range capable speakers let us know.
Bob |
