I came across this recent review for Bruce's speakers - ET LFT-8b. I owned 8a's at one time and regret letting them go. In the article I discovered something about Bruce that I found fascinating so I wanted to share. While my review of the LFT-8b was in progress, Thigpen went off to Africa to help with a study on the hearing of infrasound by elephants—he would be the man to go to for infra-sound all right. See rotarywoofer.com for more. The whole article. http://www.theabsolutesound.com/articles/eminent-technology-lft-8b-loudspeaker/ |
Chris, Bruce is indeed a fascinating individual and his talent is obviously never in question. After half a dozen, or so, phone conversations over the years I have gotten the sense that he is a kind of "mad scientist"; and, I say that in the most positive way possible. He has always been willing to speak on the phone and provide help with not a bit of impatience, but never touts or hypes any of his products or ideas; he has a sense about him of very quiet confidence with a bit of dryness. Speaking of his subwoofer: I have often wondered how a person does and funds r&d for a product like that. How many can he possibly have sold so far? Have you ever heard/seen this thing? I would love to.
I too have been a fan of his planars and came very close to buying a pair of one the very first models (model # escapes me) of them years ago. I first heard them at a local dealer and a little later at an audio show here in town where his speakers and Meitner (another genius) products were part of a system. As much as I love Meitner products (I still have the old MTR 101's and Pa6i in a second system) the sound at the show was a disaster due to their use of the Meitner turntable. Remember that one? It is a beautiful thing and has no platter to speak of so any warps of the vinyl surface become extremely audible; at least that's what I heard that day. I kept wanting to ask the guy: can't you hear that! I think that unfortunately that experience derailed my interest in the speakers at that particular time. |
Ct0517: I was currently listening to Nat King Cole, then I logged on and tuned in to your response regarding a female fan of the ET. Now, I'm in heaven!
Aguser: If you're still listening/reading, regarding my insistence on leveling. My earlier posts regarding differing manufacture's "varying degrees of trueness"...
Levels: There is a usefulness and a need for an accurate bubble level. However, when one considers the larger expanse of say an armboard or platter or the base, (in your case/and mine, the HW-19 series table), these larger areas are more accurately measured by a longer level because of these "varying degrees of trueness".
Challenge: Take a bubble level and place it anywhere you wish on any one part of your HW-19, (armboard, platter, base) then move it a few inches. I guarantee you, you'll get a different reading. This is the sole reason I'm posting here. Most people will take the manufacturer's table/it's individual parts, for granted as being true. A big mistake.
To get the most accurate reading, one needs to take the larger expanse of each individual part and then measure with an accurate level. I'm currently using a Bosch GPL3T laser level. It's about 10 inches long, has 3/D laser outputs and even has magnets on one side. It is nice that this level doubles it's effectiveness by playing a major role in my speaker set-up. Just don't get it close to your cartridge!
Ct0517: I think I could be bought for much less than that! LOL! |
Being anal has it's rewards.. at least in audio...
All my talk about "level", and other things....
When one gets to a certain level in audio, this becomes important! Somehow, all of this kind of this talk is somewhat "otherworldly" until, one get's to a certain level of audio reproduction. Then and only then, does one see the "lightbulb" go off. (Maybe this is why one has to pay $$$$ for an accurately machined tt!) Of coarse it is!
Frogman: I agree with your assessment of Bruce's personality. I wish I could be that way. The important thing is that we realize this and build upon it. |
Frogman & others: An example of how Bruce deals with his customers: Years ago, I called him on a Sat. I was having issues with air output. He (never) left me feeling my issue was not important. We talked for at least 30 minutes. I was the one that decided the conversation had reached it's end!
I hope and assume he's trained someone to "take over" when he's gone!?
He may be of a breed that we'll never see again? Let's support him/his products while he's here. |
I felt led to recommend another (lp). I've done very little record buying this year due to my focus on my tt project.
Nick Waterhouse "Holly". I hope you all audition this one on your favorite way to do so. This type of music just "moves" me. I submit, if you are not moved in any of these three basic ways, you are dead inside! (physically, emotionally, spiritually). For me.. it's all three. The sonics are very credible, not perfect. Here again, it's the overall interaction with the music that's important.
This record was pressed at Chad's Quality Record Pressing plant. I should say, I had to ream out the spindle hole (slightly) for proper tracking. Enjoy! |
My mentioning of having to "ream out the spindle hole", got me to thinking. (Sorry).
We spend thousands of dollars on equipment. Then we see a need for (tt owners) high priced speed controllers. I hear no one talking about the lps that we so cherish, being pressed in the very way that most of the time gives a market for these high priced accessories. If you pay attention, I'd say 80% (conservatively) of the lps we purchase today are "off center". This is (the) very basic issue, that we, (as people who spend a major part of our live's, by time and treasure and as lp listeners), should be more vocal about.
My audiophile "toolbox": I mentioned earlier the Bosch level, this should be in every audiophile's "toolbox" as should an Exacto knife,(lp players only), for reaming out the spindle holes of improperly pressed lps. There, I said it. I keep this knife very handy at every listening session.
If at some point in time, I put an lp up for sale, and that lp has gotten this treatment, you will be the beneficiary. |
"The Common Man"...(me)...
I'm here for you.. This is who I am. I'm an avid music lover. The exception.. (a music lover who enjoys reproduced music done "well").
I've always put my life's emphasis on high quality music reproduction. Myteen years, I was the guy with the "van", I escorted my friends around for all our "enjoyment"! I used to frequent music stores, purveying the latest speakers and such.I realize now,I was listening for the best sound.
Thirty years later, I'm still searching for the "pot of gold" the best sound. I've found that now.
There's a price point... the plateau were one realizes that to gain more musical satisfaction in any realistic/financial way, without spending "major bucks", you find a "resting place".
My "resting place" is with the EAR, using the MM phono stage w/ Telefunken/ Seimens tubes and high dissipation "underpinning", and a Grover power cord.
This, my friends, MAKES music. It doesn't make "audio gymnastics".
Yes, there's a lot of gear I'd like to try/build, but folks, I'm perfectly happy with this EAR and my Acutex cartridge!
What brought this issue to mind was, I was playing the Allman Brother's "Enlightened Rogues" lp. Yes, the very one that doesn't get any press! This spoke to me, to who I really am. Why? This lp has the very soul of the AB, it has the boogie factor... so why does it not resonate with the "public"? This may be what sets people like me apart from the 'crowd".
FWIW, I feel this lp, my choice of the EAR, my current cartridge (Acutex), really speaks to the "Soul" of music reproduction!
The Book will follow! |
"The Book", Chapter one...
Music.. what is it? How does it connect with us? What is it about people playing instruments, reaching deep into their souls that, somehow reaches into our souls and then makes us "clean"?
This very subject could have been a novel idea for a dissertation.
The instruments are an extension of our "very being". The very basic feelings that are within us all. So, what does it take for these very basic instincts, that are within us all, to "come out"?
This question is essential to our understanding of who we all are.
These are the very questions I should have been asking myself back in the late 60's early 70's.
Is it time for Chapter two?...
No matter... I think that many chapters later, Bruce has found a way for us all to experience these unasked question, whether we realize them or not. |
"Audio Gymnastics"... Definition: in audio reproduction terms, IMO, it means a "passing moment in time" where one enjoys the sound one is hearing, however, this "passing moment" doesn't please in the long term.
We are all willing to make these momentary audio pleasures a focus, while "in the moment" very compelling, in the long term, "uninvolving".
This is a very compelling aspect of how we are drawn in to buying very expensive audio components.
Upon evaluating our life long audio pleasing "moments", we, if we are being honest, "WAKE UP", to the fact that we are just "feeding" the "machine'.
All we need to do is please ourselves, not what we feel, (not by other's standards, saying we should please ourselves).
This, my friends, is how some audio companies, feed upon our most basic, true, feelings. Yet, without much thought, we succumb to their knowledge of this and we "line" their pockets with our hard earned money.
Is there a "Book" 3 in the works? |
"mad scientist" :^) I agree Frogman on your description of Bruce. I can also tell everyone that in talking to Bruce about this thread last year he was touched by it; I actually sensed some emotion in his voice, but he does not read this thread or any others. He is a seasoned manufacturer and provider of audio components and services for many years. He stays away from public chat forums. He is also very busy and travels alot; he does have his own plane I believe. Getting his review of the Acutex 420 str to post here ....was to me a bigger accomplishment for myself, than many work projects I have been involved with ! There are six of the rotary subs installed at Niagara Falls as part of the show that explains how the Falls was created. have not heard them, came close one time recently when we were there; but time did not permit and teenagers can be very unruly - you know ? If you have a look at this image and note the words hearing threshold in the legend on the right. http://www.eminent-tech.com/woofercomparison.htmlMe thinks Bruce will need to update the Legend with words - one for Human hearing threshold and one for "Elephant" when his study is complete ? Kind of gives new meaning to "Elephant in the Room" ? Frogman - that Meitner turntable you referenced... here is pic, http://www.museatex.com/at-2.jpgI don't get it. The record would need to be really thick and no warps to even work ? imo - vibrations would be headed to the center where the bearing lives. |
You ET-2 guys are the mad scientists `Ö´ you constantly and fearlessly keep experimenting. Fantastic hobby, very interesting reading. :-) |
Hi Harold
For me personally, I have been called mad, and other words I can't use here... many times; but never followed by the word scientist.
With the way the world has become so automated and digitized, IMO anyone into vinyl today who sets up his/her own table, tonearm and cartridge must have some scientist seed in their DNA ?
Cheers |
Slaw - I logged on and tuned in to your response regarding a female fan of the ET. Now, I'm in heaven! Not just any ET2 fan Slaw.....let me introduce you to .... DorothyI don't think I need to warn you if you read Frogman's post; that it appears u will have stiff competition from him for her attention. Appears we have similar great tastes ... beyond the ET2. She looks like a good runner to me.... |
Harold-not-the-barrel: I submit the following, I "needed" to get the above (out of me), you see, it's the on-going conversation I have within myself....
First & foremost... I love my ET arm, it will always be the mainstay of my system. The ET... for me, it's like some feel about the vinyl playing ritual itself. It's the CONECTION to the music, the connection to your system, the connection that brings so much enjoyment from this hobby, or dare I say, life.
For me, If I'm "involved" with my music playback system, I'm much more connected, much more (a part), much more invested.
Music IS emotion! |
Harold-not-the-barrel: I guess my diatribe was kind of my "swan song". I was kind of dreading any responses but was ultimately disappointed that there were really no responses.
For me, music reproduced well in my home is my life. It's what means the most to me. From other's non-response tells me I may be the only one with the passion I have deep within me. I am really sorry I am the only one here who feels this way. |
Everyone: I now see that, based on your non-response to the postings I made, I need to make my focus elsewhere. It's sad that others don't share my passion for music. I'm afraid... (and I eluded to it earlier)... that my fear was the majority of you were more interested in equipment to reproduce music well, than a passion for music reproduced well and the software needed. My friends, there is a difference! |
Harold-not-the-barrel: Here are the questions I should have asked...
(1) The marker you gave 'O'(I can't duplicate it), followed by mad scientists, .....
Why is it you and only you who have the courage to respond?
Why is it when (I), give from my heart, my feelings regarding the whole musical experience, regarding us , vinyl spinners,... no one, no one but you responds?
Is it the lack of passion for the musical experience?
Is it that others just want to respond to those who may have specific knowledge of equipment they own?
Maybe it's because no one really wants to address the main issue. That main issue is MUSIC. It's not equipment. It's not "mine is better than yours, it's not, who has listened to or had the opportunity to evaluate more eguipment...
Are any of you seeing my reason for this post?
There was a time, not long ago that I was intimidated by this whole process. No longer.
I think this is where I part ways with you all.
I just don't get it. |
Slaw.
Fear not your are not alone!
Way back in this thread, I think, I talked about the connection with music being the key. The way it makes us "FEEL"
I also talk about this on my web site.
A system is just a collection of machines, sometimes this menagerie comes together in such a way that we connect directly with the music. It is a wonderful sensation and I could not live without it!
cheers. |
Slaw, as Richard said, you are not alone. Its a bit presumptuous to assume that because there were no responses to your "diatribes" (your word) that you are the only one with passion for the music. You are clearly very passionate about your music and I admire and commend you for that. There are many reasons why some may not be able to post for a few days and those reasons should be obvious to someone like yourself who has previously taken protracted periods of "time off" from posting; it is not a personal slight nor indication of lack of passion.
Since you stated that you dreaded the responses I will oblige you and take you to task over the issue of passion for music. You have an obvious passion for music that you like; but, it seems, only if it sounds good ("audiophile-good"). A while back, and in response to your suggestion that we persue a common reference, I recommended an LP that you deemed "unlistenable" due to its sound. That came as a surprise to me since it was an LP that is highly regarded for its sound quality as well as its music. I would respectfully suggest that the strongest passion for music would allow us to ignore less than perfect sound and simply enjoy the music; yes, even on a table radio. Good music doesn't need the help of fancy equipment to make its point; as nice a the equipment is. |
****as nice a(s) the equipment is.****; and as the ET2'r babe so nicely demonstrates. I'll bet there's some passion for music there! Jazz, in particular. Huh, you say? Look up the original meaning of the word as used by musicians :-)
Slaw, I guess what I am trying to say is (and, apologies if my previous post came across as snippy) that passion is great; but, never stop having plain-ol fun with your music. Regards. |
I was kind of dreading any responses but was ultimately disappointed that there were really no responses. Slaw to add to Richard and Frogman's comments. imo - It is always better to give than to receive. Meaning rewarding - gut feel stuff. You gave "the gift" as far as this hobby is concerned to me. Music that touched you and you put it out there. IMO - you can't get more personal and giving to others than this in this hobby. Never expect anything back. I hope to see more recommendations from you. The marker you gave 'O'(I can't duplicate it), followed by mad scientists, ..... Copy and paste from Harold's post. `Ö´ In Windows: Start>>All Programs>>Accessories>>System Tools>>Character Map (Sometimes called 'Keyboard Map') select characters from different languages. ^Ö^ I changed it up. can't find the marks on either end that Harold used ? |
I'll bet there's some passion for music there! Jazz, in particular. Huh, you say? Look up the original meaning of the word as used by musicians :-) could this be the other thing I think of, other than running, :^) when I see Dorothy ? |
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Frogman can you provide us with a music selection that in your opinion exemplifies this... I'll bet there's some passion for music there! Jazz, in particular. Huh, you say? Look up the original meaning of the word as used by musicians :-) I am in big, big doo doo if my wife ever find this thread. |
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Frogman
I enjoyed the tracks very much.
Thank you! |
Frogman your Beth Hart & Joe Bonamassa videos had me looking for something to mix with my morning coffee (...and maybe a cigarette?)
only to find my liquor cabinet has been pillaged.
The Nancy Wilson video sure harken's back to a much simpler time imo - boy, times have changed.
I tell my 19 year old son, "the girls never approached you in clubs when I was your age"; "the guy had to have a plan and a good introduction to go up and approach a girl in a club". He doesn't believe me, as these days according to him, the woman have become the hunters. I wish I was 19 again. |
Richard, glad you enjoyed the tracks. Chris, times truly have changed; but, maybe it's all just less subtle now. Truth is that in many ways they have always had the power and control. They can turn us into mush with a look from those Beth Hart eyes. They have what we want; the "fire". More Beth Hart (those eyes!): http://m.youtube.com/watch?v=fALdOkf_eCMWifes, if you're sneaking around here, this one's for you (and don't be too hard on us). One the greatest singers of all time: http://m.youtube.com/watch?v=K-mI3k6YIFMand one of the most beautiful and, in its way, sexiest records ever: http://m.youtube.com/watch?v=7OtpZe_HSNg |
Further to the quality of the air supply.
My current air rig is.. Compressor with storage tank and built in regulator.. 4 feet of 1/4" tube, tee to bleed off needle valve and second regulator with filter/water trap.. 40 feet, soft clear PVC 1/4 " tube....arm.
Compressor cycles off at preset pressure.
The 4 foot tube was black hard plastic. What type of plastic? I don't know. I have just changed it to 1/4" PVC soft clear plastic.
Testing with the compressor cycled off showed an improvement with the clear PVC. This was a little surprising to me so as a backup I inlisted one of my sons to do an ABAB test.
I just asked him to tell me if he could hear a difference and if yes, which he preferred and why. He did not know what change I was making.
Note as above. The compressor pump had cycled off for these tests so the air was being drawn from the tank only.
He told me that he could hear a difference and he preferred the soft PVC. Stating it is "much clearer"
Regulator instability?
Go figure! |
The eyes have it Frogman. Also one very classy lady Shirley Horn. Truth is that in many ways they have always had the power and control. If I can add an observation. In regards to business power positions, my work field - IT Business Services, is one of those areas that has many women in the key power positions. I can honestly say the best bosses (fair and understanding) I have worked for, have been women. As consultants we worked for a number of women at companies who were our "boss" during engagements. One of the more interesting ladies I still remember well as we did a job for the IT shop at her organization. SOCAN (the Society of Composers, Authors and Music Publishers of Canada) Among the many facets of this company, their IT shop runs the actual computers that figure out and calculate which artists get paid performance royalties based on air play. A fascinating stint for me as a music lover and this lady boss we worked with was very colorful. If anyone has ever been curious to learn how the heck they figure out how an artist gets paid royalties for their music played on the air, here is a short animated introduction to it - from the SOCAN site. http://www.youtube.com/watch?v=0IJB6X-OGec |
Richard - I was thinking about what you posted. If using a run of 40 feet, there is enough "space" within that tubing to allow the tubing to act like a surge tank when used with a regulator at the other end. This was explained to me years ago by the shop where I got my fittings. When the tubing material is soft there is also a greater chance that the tubing will expand and contract to deal with changes in temp/humidity and the air supply. If you have a regulator at the end of it "prior" to the tonearm you can regulate it and thus the surge tank analogy. You don't need 40 feet of actual house space to get these benefits. You can just coil up the tubing in an area.
Now some I have known choose to have long runs, straight in to the tonearm manifold, meaning the tonearm air bearing spindle could be experiencing air flow changes as the record plays. Especially if the air source is not steady or in a different part of the house; different temp, humidity etc. I imagine this can make for some interesting music ?
I am using fairly rigid white poly for the main run to the in room regulator. Its a perilous journey around corners and through a wall. Its quite stiff and rigid, it won't kink and is very easy to feed through tight areas. Its the same tube material they use in house town water 3/4 inch plumbing with sharkbite connections. Its doesn't expand and contract with temperature/humidity changes. The short run from the in room regulator to the tonearm is clear tubing. Cheers |
Richard and Chris, I have always had a 50' spool of excess (unnecessary; length-wise) clear and fairly rigid tubing between the pump and my surge tank. Like Chris mentioned, the coil of tubing will act as a surge tank. I was able to confirm the benefits of doing this when my previous surge tank exploded and I needed something in the interim.
I am intrigued by the comments re soft vs rigid tubing. I have not experimented with the two versions and logic seems to suggest that rigid would be better as Chris says. However, might it be possible that the air pressure causes the soft tubing to expand and actually create an effectively wider-diameter tube, thus increasing the "surge tank effect"; and, why the soft/clear sounded better?
Like someone recently said, this is mad-scientist territory. |
Chris, thanks for the links. A very important topic and one that is not understood by many music consumers. Music is such a personal thing for most of us ("Those eyes!") that it causes most listeners to think of themselves as music lovers vs the more clinical "consumer". In fact, music is a product like any other, and it's creators are entitled to fair compensation for its consumption. I have never understood why many feel a sense of entitlement to essentially steal that product; no different than shoplifting. I remember well when the SNL band had to pull all the charts of Beatles tunes out of our book because it was simply too expensive to perform them. As with most things, what is ultimately paid is negotiable; and, The Beatles, being The Beatles, have no incentive to negotiate anything. It may seem unfortunate, but I say more power to them. |
Frogman et al,
There are many reasons why different tubes will affect the sound.
Depending upon the velocity, the air is likely to flow chaotically, forming vortexes and eddies as it moves down the pipe, it is not necessarily laminar.
The geometry of the tube, the roughness of the tube walls, the elasticity of the tube and the purity of the air all affect flow and chaotic behaviour.
Furthermore, air is compressible, which affects flow. And finally as air flows, compresses or decompresses, it can change temperature which affects pressure and therefore flow.
Keeping the tube as straight as possible will reduce turbulence, just like an optical cable with digital - oh the irony.
It is quite complex.
As an aside I would have thought it would be advantageous to have a regulator at the end of the long tube, just prior to the arm, as the length of tube after the regulator will, if my rusty memory on fluid dynamics is working, drop the flow rate going into the bearing.
In other words if 2 of you had the same regulator and 40ft of tube, and one places the regulator at the start of the tube, and the other places the regulator at the end of the tube, then I would expect that you would end up with different flow rates into the bearing. I would at the very least expect a significant impact on the "sound" from where you position the final regulator in relation to the arm bearing.
Suggested music for AB testing - JS Bach Air on the G String : Zoltan Rozsnyai/Philharmonia Hungarica on M&K Realtime for the audiophiles, perhaps Malcolm Sargent/New Symphony Orchestra for the purists on HMV ( 78rpm of course ). |
Very interesting, Dover. Thanks for the explanations and music recs.
Regards. |
The motivation for putting a soft tube between the two regulators was the finding that a small amount of bleed off between the regulators had a positive effect. This implied that the air pressure was not constant between the regulators. Or for that matter after the last regulator. More pressure equals more flow into the arm since it is not a compensated load and since a needle valve is not a compensated load either it will pass more or less air as the pressure increases or decreases. So the needle valve tends to smooth these pressure changes hence smooth out the air flow.
The soft walled tube acts slightly like a balloon, it tends to absorb small pressure perturbations by expanding with increased pressure. The surprising finding was that this positive effect was present even when the pump had turned off. This points towards the regulators themselves creating tiny pressure changes which the softer tube helped to reduce. Acting in a way like a surge tank.
If this is correct then it may be better to have the regulator remote from the arm. A long length of soft hose to the arm then helping to smooth out the regulator pressure irregularities. Obviously more testing is required. One test would be to fit a surge tank after the regulator in a rig with a regulator close to the arm. Or simply add another long length of soft tube which would be so easy to do....Chris. A small increase in regulator pressure may be required if this was done to compensate for the line losses.
It is fascinating stuff.
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Richardkrebs,
From your explanation I conclude that you are putting an argument forward that the more components that are in the process that are inherently unstable, then based on mathematical probability you are suggesting that this may increase the efficacy of the air flow. You might like to research chaos theory. Another solution may be to use a rigid tube, but put lots of pins through the tube - if you do the calculations and modelling, it would be possible to have a totally chaotic air flow rather than patterns of eddies, which may be preferable.
Last year you said that the ET2 air bearing is rigid. I assume since you now claim that you can hear a difference with different pumps and air supply configurations, that you would now concede that the air bearing is not rigid.
I have studied engineering including fluid dynamics and the way I view the ET2 is that the air bearing is not rigid, and what you are doing with all this experimenting on air pumps and tubing is in fact minimising instability within the bearing. That is why you hear a difference.
I note that you are now running 17psi whereas previously you said that 12psi was optimum ( and that your arm was perfectly rigid ). Can you explain why you have changed your view. Have you removed the lead and put your arm back to standard with the decoupled counterweight put back in now ? |
Dover
Below is a copy of a mail I received from Bruce T many months ago. You might find it enlightening reading.
"Richard,
The resonance of the air cavity is over 500Khz and does not manifest itself on the surface of the bearing, it is a well damped liquid bearing.
A statement - " the air gap allows movement at audio frequencies" - shows a lack of understanding regarding how a tonearm works.
In two out of three degrees of freedom (x,y, & z axis) a cartridge is completely free to move in any tonearm. How can it not move in the X & Y axis but magically pull and push in the constrained Z axis? The record is encoded in and the forcing functions greatest in the X (vertical) and Y (horizontal) axis.
A tonearm works because of mass present in all three axis with the forcing functions above the systems natural frequency. The tonearm components headshell, arm wand, are thousands of times heavier than the cantilever and stylus, so by a ratio of masses, they sit still.
To put this in perspective go run back and forth and jump up and down on a several hundred thousand pound untethered barge and watch the displacement of the barge, while it will move, its motion will be extremely small relative to yours and proportional to the ratio of masses.
I used three measurement methods when developing the tonearm, accelerometers, strain gages, and the simplest and most effective was the use of a second tonearm to play parts of the tonearm under test while playing a record. Measurements at the air bearing are more than 60dB (1 million times) below signal levels, lower than the pivoted tonearms I used for comparison. In reality the ET-2 has its highest inertia in the Z axis and appears rigid to the cartridge.
If a tonearm moved at audio frequencies it would reveal itself as dips in frequency response.
brucet"
The arm IS rigid at audio frequencies, however it is sensitive to supply pressure irregularities. These are two completely different phenomena.
re pressures. In my rig, I found 12 PSI to be optimum without an oil trough, 17 psi with one. There is no inconsistency.
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06-04-14: Richardkrebs
The arm IS rigid at audio frequencies, however it is sensitive to supply pressure irregularities. These are two completely different phenomena. Richardkrebs, your interpretation of Bruces email is interesting. Could you explain what you think happens when there are supply pressure irregularities. Conventional air bearing theory is that the dynamic stiffness of the bearing will be affected by the air pressure and the surface area of the bearing and other factors. Are you suggesting that the large diameter bearing tube upgrade and high pressure manifolds have no benefit and that users would be better off attending to supply pressure irregularities ? This would be a game changer for most participants on the thread if it were true. Are you using the 2.5 manifold and bearing tube or are you using the high pressure manifold on an ET2 ?? or are you using the original manifold on an ET2 ?? By the way, I agree with Bruce's observations - traditional tonearms with gimbal bearings are prone to chatter and noise, and the offset tracking angle introduces a raft of conflicting forces on both the cantilever and bearings. Notwithstanding that a unipivot is another story.. |
My thinking on why pressure irregularities have such a large effect is this. It is to do with the way the air enters the bearing manifold. This thru a small single hole. It then circulates around the sleeve and enters the 14, from memory, threaded and loosely plugged holes exiting around the spindle. Each bleed hole will see a slightly different inlet pressure because their is a dynamic flow around the manifold with associated pressure drops. If there are pulsations in the air stream this will be manifest as slightly different flow rates into the manifold and thus pressures seen by each of these holes and the flow rate thru them. This would cause the spindle to chatter. When I built the replacement manifold, I planned to interpose a finely sintered metal tube between the air inlet and the sleeve. The idea being to force the air to more approximately enter the sleeve area at all points simultaneously. I didn't do this because it made the diameter of the manifold too large and it would have fouled with the platter and I didn't think that it was a big deal. I do now.
The walker arm manifold has 4 air inlet points. Maybe they have looked at this issue and used multiple inlets to help reduce its effect. |
Richardkrebs, On the one hand you say that the air bearing is rigid at audio frequencies, but now you speculate that the arm is prone to chatter due to "pressure irregularities". You also claim that the pressure irregularities are audible. The two theories are mutually exclusive - they cannot both be true. 06-06-14: Richardkrebs
If there are pulsations in the air stream this will be manifest as slightly different flow rates into the manifold and thus pressures seen by each of these holes and the flow rate thru them. This would cause the spindle to chatter. You do Bruce Thigpen a disservice. 06-04-14: Richardkrebs
Below is a copy of a mail I received from Bruce T many months ago.
The resonance of the air cavity is over 500Khz and does not manifest itself on the surface of the bearing, it is a well damped liquid bearing.
I used three measurement methods when developing the tonearm, accelerometers, strain gages, and the simplest and most effective was the use of a second tonearm to play parts of the tonearm under test while playing a record. Please advise what testing you have done that would confirm your theory. The ET2 manual clearly states that Bruce goes through a design process, supported by principles of physics and sound engineering, includes mathematical modeling, the production of prototypes and thorough documented testing before his products go to market. There is no speculation or guesswork involved. The ET2 has evolved from the 1st incarnation that utilized low pressure low flow bearing, then with the advent of customers using higher pressure pumps ( the WISA300 for example) Bruce redesigned the bearing for high pressure low flow air supplies. Bruce will also custom build for specific air pumps and provide advice on cartridge compatibility with each of the options. It is abundantly clear that each bearing has an intended set of parameters with regard to pressure and flow. You have discarded the original ET manifold housing, discarded the decoupled counterweight, discarded the horizontal moving mass targets that the ET design is predicated upon, and may well be running a pump that is not optimised with your particular bearing. Unless you can provide some documented testing as Bruce does on his website, your comments can only be described as speculative at best. |
Dover wrote:
".... Bruce goes through a design process, supported by principles of physics and sound engineering, includes mathematical modeling, the production of prototypes and thorough documented testing before his products go to market. There is no speculation or guesswork involved."
You say "I agree with Bruce's observations."
Please advise what testing you have done to arrive at that conclusion.
It should be verifiable engineering: no speculation, guesswork, or internet regurgitation will suffice. |
RK - If this is correct then it may be better to have the regulator remote from the arm. A long length of soft hose to the arm then helping to smooth out the regulator pressure irregularities. Obviously more testing is required. One test would be to fit a surge tank after the regulator in a rig with a regulator close to the arm. Or simply add another long length of soft tube which would be so easy to do....Chris. Hi Richard - the extra in room regulator I use allows for AB testing of this at anytime. Long tube versus short going to the tonearm. All I have to do is open /disengage the in room regulator and it functions as a filter only, so in effect is a long tube to the pump. Let me explain something about my Timeter pump and it will make things more clear. From my experiences most pumps push air and the user is at the mercy of the environment as far as the quality of the air output goes. Meaning if the air has any moisture and particles, filters are needed to trap them. The ET tonearm's maker resides in Florida where it can get really humid. The ET 2.0, 2.5 tonearms if they had a choice would probably choose to live in Arizona; or in a room where there is forced air heating. They like the air dry ....very, very dry. My Timeter was designed for human use and has performance settings as far as how humid I choose to send air out at. Example: If you are in a room and want to be comfortable you would probably prefer air around 55-60 which is in the middle of the humidity scale to be really comfortable. The Timeter - with my T valve regulator at the pump (see pics on my virtual page) can be dialed down/tightened so that it exhales dry Arizona like air - even if the room it is in is at 80 % humidity. No other pump/compressor I am aware of does this and the ET 2.5 loves dry air. I have never seen a DROP of water in the in room regulator bulb other than the one time there was a blockage. Now the pump does need to work harder to produce moisture free air in a humid room. For three seasons late fall, winter, early spring the basement stays fairly dry with the natural gas heating. Once summer kicks in, it takes only 3 days for the basement to start feeling like a basement again - humid and damp. This is also the time when I make an adjustment to the Timeter by tightening down the regulator at pump's outlet so the performance gauge reads in the green zone. Green zone for this compressor/pump means the system is running efficiently and no moisture is being sent down the line. It expels the moisture like a car's AC at the bottom of the pump. It used to do 50 psi when new. It probably does around 45 now and I bought it used many years ago. With the in room regulator in engaged mode - I send down 21-22 psi from the pump and I steal 19 psi with the in room's regulator. So pressure drops at the arms location on purpose (Dover alluded to this in one of his posts) The excess air goes into the atmosphere beside the pump. So in fact I bleed out 25 + psi. I prefer to run with the in room regulator functioning as a regulator with the short run to the arm. It is I believe more precise and the long tubing just before it acts like a second, redundant surge tank in addition to the timeter's own built in surge tank . Redundancy is good. Remember I am in the business of contingency planning/risk mgmt - redundancy is ingrained in me. You can call this mad, or you can call this anal. The in room regulator is set for 19 psi. Along with being more precise/consistent, its bulb area also stabilizes the air (temperature) so it is same as in my room. Your average listening room goes up in temp as time goes by. Its important for the air imo going into the manifold being same temp as your room - just really dry. The in room regulator also gives me a visual of what is going on. Kind of like driving a car with real engine and radiator temperature gauges. I want to know what is going on. Sorry for the long post. Cheers |
You can call this mad, or you can call this anal. So go ahead and call me mad or call me anal.......just pls don't call me Dorothy.....I am not worthy. |
Chris.
You have now given us all another area to pine over. Humidity.....thanks a lot! :-)
I don't think that your test is quite representative of what I was suggesting, since you are disabling one regulator but leaving its body in circuit. If their is any instability in the regulator it could be caused by the its structure, since the air flow path is convoluted. For example the water separator function is achieved by creating a vortex in the bowl.
I will have a play this weekend where I move the regulator close to the arm, making the adjustment for line losses. This will keep the arm pressure the same.
I will use exactly the same hose and length so the only variable will be the reg position.
BTW, I have a pressure gauge very close to the arm, it reads in bar. Setting the pressure by ear results in a reading of 1.25 bar which is a little over 18 psi, not the 17 psi I mentioned earlier. That said how accurate are the gauges we are using anyway?
cheers.
|
don't think that your test is quite representative of what I was suggesting, since you are disabling one regulator but leaving its body in circuit. If their is any instability in the regulator it could be caused by the its structure, since the air flow path is convoluted. For example the water separator function is achieved by creating a vortex in the bowl. this is true Richard. not the best example - I could unplug both ends and just use a coupler. That said how accurate are the gauges we are using anyway? Even if these devices were perfect we know that no two records are identical. Always trust your own ears. Use measurement devices. PSI gauges, alignment devices, VTF scales to just get into the ball park. Fine tune with your ears. |
Chris.
Even if you use a joiner, you will still be removing one regulator from the air circuit so it will not be a true AB test.
Yep agree, measurements only take you so far.
We don't listen to numbers. |
Ok
Since I cooked dinner tonite, I got a leave pass afterwards...,
Have just finished trying the second regulator close to the arm.
There was just 3 feet of tube between it and the arm, the original configuration having 40 feet of tube. I adjusted the pressure to compensate for line losses.
With the regulator close, the soundstage shrunk both in width and depth. There is a subtle veil over the sound with attack and decay diminished.
The model of regulator I use is. Norgren B07-201-A1KG.
Looks like a pretty standard unit and appears similar to the photos posted here by various owners.
After an hour of going back and forth to confirm my findings, I couldn't wait to settle back to the original layout.......
Compressor with built in regulator- 4 ft PVC tube- needle valve bleed off- second regulator- 40 ft PVC tube- pressure gauge- arm.
The Norgren regulator does something to the air flow that the arm doesn't like. Having 40 ft of tube mitigates this.
I would be curious to read findings from others where a significant length of soft PVC tube was used between the reg and arm vs a short length of the same tube.
For my setup the long tube was clearly superior. |
thanks for sharing impressions Richard. With the regulator close, the soundstage shrunk both in width and depth. There is a subtle veil over the sound with attack and decay diminished. Just recollecting. When I was experimenting with PSI years ago, these are the same symptoms I encountered, when there was too much psi for the manifold and it caused the spindle to start resonating - affecting the cartridge. So out of pure curiosity my questions would be: 1)What PSI is your manifold designed for ? 2)Did you try different records that required different VTA's during the comparison ? 3)Did you try it with and without the damping trough. If you chose to compare again - I would go with a longer 6 foot section of tube to the arm and lower psi. Maybe I misunderstood what you were trying to compare so let me confirm. You went from this: pump--------40 feet hose-----tonearm manifold to this pump--------40 feet hose---regulator -----3 feet hose ---- tonearm manifold. If my crude flow chart is correct - you have imo introduced a more consistent air delivery into the manifold. The reason being alot can happen (changes)to the air in the 40 foot run. Here is something to think about. Sometimes when we introduce something that in theory should work better, for reasons described above, it ends up sounding worse. Well - what if better more consistent air delivery exposed a set up issue (i.e. too much psi) Again just thinking out loud - remote troubleshooting is difficult with a one sentence description. I do think its worth noting here again if anyone should pick up a used ET2 or ET2.5; and they do not know what PSI the manifold was set up for. One way to find out - put an old record on and start lowering pressure. When it starts skipping raise a few PSI. Fine tune final PSI by ear. ymmv - water deposits from the air could have clogged the capillaries requiring more PSI to even work ! The manifolds are easily cleaned - instructions in the manual. If I bought an Et2 from an unknown source I would clean them before setup. Cheers |
