Thanks for your suggestions, but I still think the problem is more inherent to the medium than my setup.
My racks are about 200 lbs each. Each shelf is it's own seismic sink with 50 lbs of sand in them. They are spiked to a cement floor. My TT itself weighs about 30 lbs (plus the motor which is about another 30 lbs). I am also using a Mark Kelly designed motor controller (think SDS), which makes the motor dead quiet. That's not the source of any vibrations either.
See here: http://cgim.audiogon.com/i/vs/i/f/1155818474.jpg
and here: http://cgim.audiogon.com/i/vs/i/f/1155818602.jpg
(note: bubble wrap is replaced by squash balls which proved much better at isolation from the shelf)
The subsonics are definitely not due to speaker interaction, since it happens on the lead in groove right away, before anything is playing. It is visible on the regular speakers too, when the sub is on or off. This is not an isolation problem due to standing waves in the room, but a rumble problem due to low signal vinyl interaction with the cartridge and phono stage.
Therefore: standard subsonic issues with vinyl. I even tried damping the tonearm, with no affect on the subsonics but a lack of air and life to the music - so that's been reversed now.
I spoke with Jim Hagerman about this and he said he purposely did not limit any extension at either end, making the Trumpet very wide bandwidth. He suggested changing out the .22uF inter-stage coupling caps to .1uF as a possible partial solution. I did this with no obvious change (however they are now upgraded to RTX's).
Please keep the ideas coming. At this point I think the answer is going to be electrical (e.g. a rumble filter), but I'm open to trying other suggestions first.
Thanks,
Bob |
Thanks for the link Fap. Is this filter available in a kit form, or just the schematic as provided? Where does it plug in, between the cartridge and phono stage or after the phono?
I assume the whole signal rides through it ... if so then I assume the op-amps affect the entire signal. So I would expect that different op-amps might affect the overall sound in different ways - no?
You mentioned an increase in apparent available power, so maybe it adds a bit of gain also?
What phono stage are you using with it? Did you notice any affect on transparency or soundstaging or the top end?
Thanks,
Bob |
When I built it I was told that Corian is dense and fairly inert. It certainly is heavy (and pretty to look at), but I often question the same thing as you. I have toyed with the idea of applying a heavy piece of aluminum or some such to its bottom as an additional damping solution. But I have trouble trying to figure out how to attach it sufficiently and whether I should put some EAR Isodamp or some such between it and the Corian (e.g. constrained layer damping of sorts).
Bob |
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 |
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 :-) |
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 |
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 |
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). |
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 |
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 |
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 |
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 |
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 |
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 |
Bob#2 - as much as I don't like to say it, because it might hurt some feelings and because we all know the size of our system reflects the size of our audio-manhood :-), I have to agree with you.
The subsonic problems I seem to have now were not there in the past. The resolution of my system has improved greatly with a better phono stage, better arm, teflon caps in my preamp, etc. Yes, the music got better, yes the sound is better, and yes I now seem to have a new problem caused by this increase in resolution.
Bob #1 |
I got some 180gm Acoustic Sound LP's for christmas. I have to say the subsonic pumping is almost gone with these. yes, there's still a little cone movement, but not like a regular flimsy record.
So the problem I'm having seems to be more record dependent than anything else, or I would have the same level or problem on all records, right? I still think it is a problem with the media and not isolation or airborne vibrations and stuff (because it happens when music is NOT playing also, in the lead in/out grooves).
In any case, it still sounds good and is not a huge issue. It's just my completest nature that I would want to remove it if I can do so easily.
Enjoy,
Bob |
There is cone movement on both. 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 subwoofer is noticeably greater and sometimes very audible. You can hear it by ear, like a whoomp-whoomp air pressure feeling.
I've tried several different methods of reducing resonance to see if that would improve things. Adding mass to the headshell, damping the tonearm, taking the table off the rack and putting it directly on the concrete floor, etc. There is no noticeable difference from any of them, so I think it is subsonics fromnt he record itself in my case. |
When I say it's not audible I mean the woofers are pumping but I don't hear any thumping in my ears, the way I do if the subwoofer is on. Yes, it is definitely being driven by the amp and using up some power but it doesn't audibly interfear with the music.
The sub has a substantially bigger driver which moves more air and is designed to pump out those low frequencies. I hear the "whump" from the sub.
So based on my experience with thicker records vs flimsy vinyl I definitely see less of a problem with the thicker records. So I am leaning toward the belief that it's on the records and my system is resolving enough to bring out the flaws in the medium. Again, this was not as much of an issue before I got a better phonostage.
All in all, again, turning off the sub seems to resolve the worst of this to my ears and, short of building a subsonic filter, is the solution I'm going with for now. None of the mechanical solutions I've tried seems to make any difference at all.
On another note, I have been playing with string recently in place of the rubber VPI belt and have noticed a nice improvement overall. Yes, I have a speed controller and it is essential to getting this right. No, it doesn't change the subsonic issues.
Happy New Year,
Bob |
Just wondering ... the VPI platter is not supposed to be used with a record mat. It's design is intended to couple the record to the "vinyl like" composite platter.
What would a record mat do for me here? Might it help dampen these vibrations? What do they do for the sound (I would expect a dampening there as well, no)?
Any thoughts? Any recommendations on which ones to try? Anyone with practical experience using a mat on a VPI platter?
Thanks,
Bob |
My rumble went away when I decided to change out my cartridge, which on paper looked to be a great fit with on resonance issues. I went from a Dynavector XX-1 HO to a Transfiguration Temper LO. I didn;t change anything else, but I can now safely turn on my sub when I'm playing vinyl with no excessive pumping.
Go figure.
Bob |
This solved the problem on all the LP's that I have played since I upgraded. There is still some little movement on my woofers, but not the "huffing" that I was getting before very audibly on my Rel subwoofer.
And believe me, I tried everything mechanical, short of an electronic filter, to identify the cause of this problem and remove it. It must have been a cartridge/tonearm mismatch.
Good luck |
