Slaw - there are enough variations in the degree of trueness that leaves me extremely conscious of the importance of the ability to machine as true as possible. Richardkrebs - Getting accurate alignment when two components are brought together from different manufacturers, without the ability to adjust, would be pure luck. Slaw, RK, others... From my experience with 7 or 8 TT’s it is very difficult imo for a TT manufacturer (without naming brands) at certain cost points to reach a certain degree of trueness between the tonearm platform and the platter (all the way around it). What I have personally learned, when you come upon a serious manufactured TT design; a different standard/level of trueness is found among other good things. Just an observation. But then no two records are true....the source media.... and records provide a medium to reveal amazing things..... as long as the stylus is placed as correctly as possible in the groove. So how correct is correct ? What does correct mean. Some food for thought..... ************************************************************ From 25 years ago. Not much has changed..... “The angle that the cutterhead is placed at when a record is cut results in an included angle in the final disc. This included angle must be duplicated with the reproducing stylus or distortion will result. The problem today lies in standardization of the angle by record manufacturers and corresponding standardization by cartridge manufacturers. Presently most records are cut with resulting vertical angles between 16 and 20 degrees. The average vertical angles of cartridges manufactured today is slightly higher than 22 degrees. The result of this mismatch is less than optimum performance for many cartridges. Although the vertical energy contained in a record represents approximately 40% of the total energy on the record (60% lateral). The distortion levels we are dealing with are quite high. In some cases, the vertical performance with certain types of distortion can be improved from 2.5% to 1% or less.” Taken from Page 51 ET2 manual ************************************************************ Hi Bruce - a question from your past testing if you have the answer.
Did you find any relation between the included angle of vinyl records and their thickness.
Example -
Is it possible to assume that that you can have two same thickness records with different included angles?
Thanks Chris
Chris,
The standard was supposed to be 20 degrees, when you talk to people who cut records, they do not check, so it turns out to be random, close to 20 degrees, but not exact. Yes, two records of the same thickness could require different VTA settings. I hope this helps.
brucet
************************************************************ This tells me if we are going to be anal about level trueness we need to be anal about VTA because the records are cut with random included angles! Different records even if they are the same thickness, can have different included angles. This explains to me why same thickness records sound different (bass compression / HF’s ) with the same cartridge sometimes in my room. We really do need to trust our own ears with our own cartridges and not assume a certain degree of setup for cartridge X with all our records. So ? For me it is very good and desirable to therefore have a high degree of level trueness (tonearm platform and platter) but it is only half the battle. I have discovered the other half of the battle is the ability of the tonearm to adjust so that the stylus can be placed at different VTA angles in the black disc – conveniently. Meaning as the records is playing as I am listening ! Vinyl is a total mechanical process and I don’t want to stop my listening routine to adjust more parameters. So to me having with the ET2 unlike any other tonearm I have ever personally owned .........VTA on the fly that works (meaning it does not change cartridge VTF and overhang) while the records is spinning is very important. In the past I considered removing the ET2 VTA mechanism (I thought to make it more rigid/less resonant in effect). You see for me personally I don’t change VTA for every record. I am not that anal. But there are some records that are off compared to the other mediums digital and tape and it is noticeable in my room. I would not be without VTA on the fly with my tonearm. |
Chris.
Yes lifting off at record end is an interesting exercise after a few glases of fine NZ Pinot Gris.
Which end for the trough? The one with the least amount of joins and material changes before we get to the cartridge. In my most humble opinion :-)
Was it Townsend that put the paddle on the headshell itself? |
Slaw.
Wrong thread I know, but are you in a position to tell us about your "up coming tt project" ? |
Slaw – good to hear from you again.
You are the only music lover I am personally aware of that has the capability and makes his own custom listening chair!
Thanks for sharing the pics of your setup Richard. An obvious amount of time and passion went into your setup. Interesting the side the oil trough is on.
I have thought a couple of times of removing the back end of the ET2 that holds the railing and handle to raise and lower the ET2. My Dynavector DV505 is without a lift and I hate it; but it also at the back which makes it awkward. I like having my ET2 arm lift especially into those late listening sessions. Putting the cartridge down is not the problem – its lifting it at the end – knobby fingers and a 10 year habit with the luxury of that elegant lever – I am not taking a chance on an expensive cartridge.
I believe Dover posted that he inserted some material in the handle to decouple it more. |
Does your design allow enough adjustment for the differing heights of the various cartridges out there? How about overhang? Any adjustment for this? Of course, these two go hand in hand most of the time. |
Slaw.
"Variations in the degree of trueness"
Totally agree. Since I had the luxury of building the arm and TT, almost concurrently, I could deal with these topics in real time.
Getting accurate alignment when two components are brought together from different manufacturers, without the ability to adjust, would be pure luck. |
Richardkrebs: That is quite an unique design, so unique that it becomes very different from the standard ET design we are all using. In this respect there may be little use for any comparison. Therefore, I understand Ct0517's remark above. One thing I've been thinking about for some time for my upcoming tt project is machining tolerances. Checking my pricy platforms (Symposium, BDR) and even the acrylic top on my VPI plinth @ platter with a accurate level, there are enough variations in the degree of trueness that leaves me extremely conscious of the importance of the ability to machine as true as possible. This is one reason why I like the added flexability the stock ET design offers. |
Hello. There has been some private questions about the design of my modified ET2. I have included here some more photos for those who may be interested. The target design brief was to - eliminate all unneccesary joints. - minimise different material count - eliminate any unneccessary components that could move - make it as rigid as possible - make it as inert as possible. These took precidence over convienence of use. http://cgim.audiogon.com/i/vs/i/f/1370870032.jpgThe main pillar and manifold are acrylic, since the decission to make the TT plinth out of acrylic was already made. This allowed me to fuse the arm pillar to the TT chassis eliminating one joint. No allowance is made for making the spindle parallel to the platter, after the fact, but I decided to machine the bottom of the pillar should this be required. Measurements showed that this was not needed. Two cavities are milled into the pillar. In one is glued a lead billet, the other is filled with sand. 4 X M5 capscrews in machined slots pass thru to the manifold. These are loosened and the removable VTA screw is turned to raise or lower the manifold. One turn is approx 1/2 mm (20"). Tightening the cap screws creates a very strong joint. The manifold is indexed to the pillar with a lug each end to keep it level. The pillar manifold interface is not curved. This because I did not have the machining capability at the time of build. 2 x M2 grub screws pass thru the manifold and contact the bearing sleeve pushing it slightly towards the pillar. At 120 degree increments there are 2 small pieces of shim metal inserted in the gap between sleeve and manifold. Tightening the grub screws presses the sleeve against these shims removing the compliant o'rings from the loop. Arm lifting is done by hand and the wand rests on a piece of foam at the cartridge end, when off the record. The goose neck is solid aluminium made from the same grade as the spindle. The oil trough paddle is attached to the goose neck. This is a 15 year old design, if I did it today there would be a few changes, but the fundamental architecture would be the same. As you can see my ET has had a little surgery :-) |
Ct0517: an excellent description of the goings on with the leaf spring and how it works. I only wish Bruce would have mentioned the effects and the availability of the differing leaf springs years ago. A neccessity at this moment in time and should be included in future owner's manuals. |
Apologies for making this statement without reading all I've missed. (My father passed away and I had been his primary caregiver for several years, this has severely dampened my ability to give my (all) here for quite some time).
Just wanted to add... I've been using aftermarket 80W silicon fluid available at hobby stores with no sonic degredation,( paddle barely skimming the fluid)( I use an oral syringe to add/subtract fluid as needed, it's so much easier than fiddling with the paddle!), also using DuPont NLGI #2 w/ Teflon white lithium grease in my VPI bearing (ceramic ball bearing) to excellent effect. |
Richard - I find the word multi-spring can be misleading. We are actually joining (glueing) single leaf springs to make one thicker one. Think of a truck with a leaf spring in the back. leaf spring suspension I see this as similar physics except we are working in a horizontal fashion not a vertical one. The suspension becomes more compliant if we remove leaf springs from that truck. More firm if we add springs. As we add springs we need to add weight to the truck otherwise it becomes bouncy on the road. The ET2 is the same. As we add a leaf spring or two we need to increase VTF if using the same cartridge. We also need to keep the inert lead weights at the end of the I Beam for resonance control – away from the air bearing. MOST ET2 users go wrong with the lead weights - imo - because they are coming from developed habits with a pivot arm. What do you do to increase VTF with a pivot arm? You bring the weight in more toward the bearing. The ET2 is a unique tonearm unlike any other with a decoupled counterweight. The weight needs to stay at the end away from the air bearing to not impede it and for resonance control – away from the air bearing. So we just add a weight and keep it at the end. My direct experience – adding a leaf spring (glueing two together) to the ET2 or Et2.5 means it can carry a higher load (heavier less compliance cartridge) better. The result in sound with heavy MC is amazing. Bass is further tuned to your room by turning the counterweight cap downward or upward. This will depend on your actual room and how good your bass compression is with the speakers you are using. Thanks again to Frogman for bringing the double and triple leaf spring to the discussion here. Bruce has been shipping loose leaf springs out with his tonearms for years. His customers probably look at them and think - wth is this for - maybe a spare ? |
Chris.
I have added a multi spring test to the long agenda of things to try.
Liked you cartoon. How true.
Many thanks |
Ha-ha-he man – please tell me my last post brought a couple ha-ha’s to you? FWIW – the first time I saw that I almost soiled myself. I actually printed it off and put it on our fridge. I think it helped me to bring in one amp and one speaker. (grin) Fyi – Here is my ET2 and ET2.5 tuning information for various compliance cartridges from the last year. From a compliance high of 50 down to 10. And VTF’s of .8 gms to 2.1gms. ET2 and ET2.5 Cartridge SetupsRichard – fwiw - I am getting excellent early results in my room with my low compliance XV1 and triple leaf spring. 2 fat and 2 skinny weights setup according to Dorothy. :^) If you are the least bit curious I highly recommend you listen to your setup with a decoupled I-Beam – using a triple leaf spring and just the inert lead weights. You could try this with and without your now famous lead spindle slug? Two I Beams and 5 loose leaf springs to make up a double and triple leaf spring can be purchased from Bruce for a very nominal amount of money. Otherwise enjoy the tunes. Cheers |
Richardkrebs - Has anyone else thought that this hobby of ours is an addiction? A strange phenomena in my household. Family members seem to think that addictions can be treated; It forced me to use a different tact. I now use the word disease instead in our house. For some reason I can’t explain, it is more effective |
I must remember my lines
Richardkrebs .... has an increase of 6-12db at fundamental resonance
I must remember my lines
Richardkrebs .... has an increase of 6-12db at fundamental resonance
I must remember my lines
Richardkrebs .... has an increase of 6-12db at fundamental resonance
I must remember my lines ....................
Dover |
Chris and others.
I can see how our discussion has become tedious for other readers. I apologize for this and will be more considerate moving forward.
On a bit of a side path. What happens when a new better piece of gear is installed, say new speakers.
We set them up, friends come around and after they are run in, all listener's agree that it is a big improvement. We all hear better this and more of that,......for awhile. Then it becomes the new normal and we go on the quest again for "more". Has anyone else thought that this hobby of ours is an addiction?
BTW
When Goldilocks dipped her toe in the bath, she found the temperature to be just right. |
RK - Further I now consider an oil trough to be manditory for this rig. After some tweaking I am getting excellent results with the damping trough. When I used it years ago I was obviously slugging the paddle through too much oil ! I am only using 1 CC per Bruce’ instructions. Bruce is clear in the damping trough documentation that the damping trough should NOT BE USED until one becomes familiar with the operation of the ET2 and ET 2.5 without the use of one first. The added benefit I find is the visual confirmation of levelness in the trough. , as the oil in the trough is obviously affected by gravity. Richard - I don’t like words like mandatory and absolute in this hobby. What we are creating is make believe really? This is why I like to use words like Winnie the Pooh and Goldilocks in my system page :^) |
Dover - It would be helpful to move this thread forward if you acknowledged the issues related to adding mass and move away from using examples, maths and quotes that are irrelevant and taken out of context. Actually guys – RK and Dover. I say this with utmost respect. I don’t know about the others here but I am personally totally glazed over with these discussions – back and forth. I would prefer you take it offline? You see I trust my ears for sound not theory. I don’t need approval of somebody for enjoying my hobby. But as this is a public chat forum and there may be others here that like to dwell in theory I Ieave you as be - this is my opinion only. Dover - I am really looking forward to your direct experiences again with the the ET2. Or did you get a 2.5 ? What type of pump are you going to be using? Dover - ...........Stereophile testing. What review was that Dover – can you point it out please? From the one that I read. From the Stereophile review - "As for other cartridges, I would like to see very specific suggestions from the manufacturer as to the proper combination and location of weights for a given cartridge. The arm is now too adjustable for the consumer or dealer who does not measure low frequency resonance, and I still do not fully understand how the location of the counterweight package best interacts with a given type and compliance of cartridge." Or to narrow it down. The arm is now too adjustable for the consumer or dealer who does not measure low frequency resonance Well - to me it would seem a reviewer that doesn’t trust his own ears or maybe he was rushed on time? Or maybe he should just go see DorothyBased on that statement Dover they didn’t even get close. Like the review that John referenced. Some nice measurements and good reading, but no mention of weight location or how many; counterweight tuning. IMO – this ET2 and ET2.5 can be tuned to the rest of your room/gear. But you need to live with it for a while to build a reference point. Then you can start tuning. Most audiophile friends I know have no patience. This is a question for RK and Dover. Have either of you used a double and/or triple leaf spring with a Low Compliance cartridge on an ET2 with the weights positioned at the end of the decoupled IBeam? |
05-27-13: Richardkrebs
Dover says.
"....on an undamped standard ET with decoupled counterweight there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight."
I say.
"At 3x Fr the rise in response is almost zero."
In response to this question..
In the technical section you talk about phase shift beginning at 2 to 3 times the resonant frequency down to Fr.
Does this mean that there is a resonant peak at 3 x Fr or is this the point where the phase and response errors have reduced to low levels?
Bruce T says...
"This is the point where, above this frequency, the phase shift becomes minimal, as you approach the resonance frequency, the phase shift increases. I hope this helps, thank you very much." Richardkrebs, you continue to conflate apples and oranges and misrepresent statements. The technical section you refer to is for a standard ET, with a substantial rise in response below 20hz. FLUID DYNAMIC DAMPING FOR THE ET-II
If a tonearm/cartridge system has a substantial rise in response below 20 Hz as most do, the phase response at the low end will be shifted and phase shift will occur beginning at 2 to 3 times the resonant frequency down to Fr One can achieve a flat response by tuning the decoupled counterweight and keeping the horizontal mass and Q low as outlined in the ET manual and demonstrated in the Stereophile testing. Your ET is not standard. You have doubled the horizontal mass of your arm by adding lead and you have removed the counterweight decoupling mechanism. The effect of the 2 modifications you made to your arm is to increase the amplitude of the fundamental resonance by some 6-12db as shown by Bruce Thigpens testing. Bruce Thigpen:
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results The arm Bruce used for testing was deliberately set up with a high Q and very low compliance cartridge. The standard ET when used as outlined in the manual with a decoupled counterweight has a lower Q. A low frequency sweep was performed twice on the tonearm, once without the damping trough and once with the damping trough. The cartridge used was of very low compliance and the tonearm was set up so that a high amplitude high Q resonance existed. The results of the test show a reduction in the amplitude of the resonance of about 8 dB (horizontal). You continue to ignore Bruces stated view that increasing horizontal mass increases distortion Bruce Thigpen:
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge, Clearly the reduction of 8db is for a standard arm. In the case of your arm to which you have added lead, doubled the horizontal effective mass and removed the decoupling mechanism, all you are achieving is some reduction in the problems and distortions you have built into your arm. You have misrepresented Bruce’s view on eccentric records, 05-20-13: Richardkrebs
BT uses at 30cu cartridge in his manual to calculate horizontal Fr. The arm weight he uses is 30gm plus 7gm for the cartridge. We have to assume that he is ok with this combination and that he is not worried about cantilever deflection on eccentric records. This assumption again is just plain wrong. I quote from Bruce Thigpen’s ET website: ET2 Manual page 47 :
“if you like to play severely eccentric records, ones with run out greater than 1/8th of an inch, then we suggest you use a low mass pivoted arm.” It would be helpful to move this thread forward if you acknowledged the issues related to adding mass and move away from using examples, maths and quotes that are irrelevant and taken out of context. |
Dover says.
"....on an undamped standard ET with decoupled counterweight there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight."
I say.
"At 3x Fr the rise in response is almost zero."
In response to this question..
In the technical section you talk about phase shift beginning at 2 to 3 times the resonant frequency down to Fr.
Does this mean that there is a resonant peak at 3 x Fr or is this the point where the phase and response errors have reduced to low levels?
Bruce T says...
"This is the point where, above this frequency, the phase shift becomes minimal, as you approach the resonance frequency, the phase shift increases. I hope this helps, thank you very much."
brucet
Bruce uses the phrase "becomes minimal" I used the phrase "almost zero". Bruce and I are talking about the same phenomenon. Neither of us say it is zero because the curve is asymptotic to zero. It is this characteristic which causes designers in my industry to err on the side of caution and use 6xFr. A figure I have mentioned previously.
There is No resonant peak at 3x Fr. The amplitude and phase problems reduce the further we move above Fr. Exactly as shown on the transmissibility graph I posted, which is an accurate representation of what is happening with the arm at frequencies around Fr.
Ha_ha_he_man
Further to your request.
What I hear when making the counterweight arm solid with a suitably stiff structure and when using a low compliance cartridge is this...
The image is a little more focused. Individual elements within that image are a little more vivid.
I stress as Chris has quite corrctly pointed out, my arm is optomised for low compliance cartridges.
Further I now consider an oil trough to be manditory for this rig. |
Not Utter Nonsense Dover, tell me about a resonant peak at 3 x Fr. |
What other thread allows us to learn about fine wine from downunder and good English ?
Well I did enjoy that youtube video Dover. Not surprising that not much has changed with the actual record since 1958 when the film was made. I could say they don’t make records as good anymore....anyone disagree?
In 1958 - I was just a thought in my parents eyes till four years later. Does anyone listen to music in a shirt and tie anymore?
At the 4:40 mark is an excellent example imo of a speaker setup. Nearfield and eliminating room problems by taking the room out of the picture. I love those speakers spikes. We can learn lots from these films.
The fellow talking reminds me of my Grade 8 science teacher. The guy in the film does show a bit of a smile at the end however. My science teacher in middle school was a German fellow that never smiled. |
Do you know what PSI and Pump type your ET2 or ET2.5 was designed for ?
3.6 PSI - Original Takatsuki and ET-2 or 2.5
5.0- 7 PSI - WISA 300 air pump and ET-2 or 2.5 with high pressure manifolds
>10 PSI - users with shop compressors and ET-2 or 2.5 high pressure manifolds
Note, if the pressure readings are higher than those listed above, the manifold could be clogged, if the pressure readings are lower, this suggests that the pump may not be performing correctly.
(Taken from Bruce's website) |
John47,
my name is Dover, not Utter Nonsense Dover. I have in fact studied engineering and English as well at university.
Please see below the difference between “a” and “the”
"a" [uh; when stressed ey]
indefinite article
3.another; one typically resembling: a Cicero in eloquence; a Jonah.
"the" [stressed th ee; unstressed before a consonant th uh; unstressed before a vowel th ee]
definite article
1. (used, especially before a noun, with a specifying or particularizing effect, as opposed to the indefinite or generalizing force of the indefinite article a or an ): the book you gave me; Come into the house.
2. (used to mark a proper noun, natural phenomenon, ship, building, time, point of the compass, branch of endeavor, or field of study as something well-known or unique): the sun; the Alps; the Queen Elizabeth; the past; the West.
So, in the context of a “resonant peak” “a” does not represent “the”. |
Utter Nonsense Dover, and I quote you
"What Bruce Thigpen actually says on his website .......... there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight."
It would have been useful if you had done engineering.
The peak is at the resonant frequency, not 3x Fr. |
Thekong – The answer to your question regarding frequencies impacted by horizontal Fr from Richardkrebs are mostly wrong. It is important that they are addressed. Impact of Fundamental Resonance: 05-20-13: Richardkrebs
Thekong.
The answer to your question regarding frequencies impacted by horizontal Fr is shown in the attached graph. From memory your Horiziontal Fr was around 5hz with the A-90. So substitute 5 for 1 on the x axis and scale up from there. At 15 Hz (3) the rise in response is almost zero. This is what BT was talking about when he mentions 3xFr. This statement is not correct. I quote from Richardkrebs earlier post 05-15-13: Richardkrebs
In Bruce's paper on the oil trough he talks about the effect of Fr being apparent at 3x its frequency. Targeting say the 12 hz you mentioned would mean that it is causing phase and amplitude problems at 36 hz. This is not good. . As you can see Richardkrebs appears to be confused. On the 15/3 he cites Bruce Thigpen as saying that there are phase and amplitude problems at 3 times Fundamental Resonance, then on 20/5 he cites Bruce Thigpen as saying the rise in response is almost zero. Neither of these statements are correct. What Bruce Thigpen actually says on his website is that on an undamped standard ET with decoupled counterweight there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight. The other mistake that Richardkrebs continues to make is to use as a reference a graph for a single harmonic oscillator that plucked from Wikipedia. Wikipedia - http://en.wikipedia.org/wiki/Harmonic_oscillatorRichardkrebs - http://s1173.photobucket.com/user/CT-993/media/ResonanceGraph_zpsdd78e0f4.png.html?sort=2&o=7This graph does not represent the forces on the cantilever because the cantilever and cartridge is not a single harmonic oscillator. A cartridge tracking a record groove has a fulcrum point at both ends – the stylus in the groove, about which the cantilever pivots, and the cartridge end of the cantilever which has a suspension. Forces are exerted on BOTH ends of the cantilever. The graph represents a pendulum with only one fulcrum point at one end only. The mathematics that Richardkrebs uses does not apply. 05-20-13: Richardkrebs
Now look at frequencies below Fr. At say 0.25 Fr we get transmissibility of 1. What this means is that, with the compliance of the cartridge used, the whole arm moves sideways. The cantilever does not deflect. This is important for eccentric record issues. . This assertion is wrong on several fronts. The cantilever deflects. Firstly – the record grooves are cut at 45 degrees. The cantilever deflects. For a moving coil cartridge the cantilever deflection moves the moving coils within a magnetic field. That is how sound is reproduced from a record player. This video shows how RCA Living Stereo stereo playback is achieved. http://www.youtube.com/watch?v=Jq2sjGFvNnM If there is no deflection of the cantilever then Richardkrebs system cannot be producing any sound that resembles music. Secondly, the statement defies physics. I quote Bruce Thigpen directly: Bruce Thigpen
“the cartridge will "see" .55Hz mounted in any tonearm, more so in one with higher horizontal inertia. I don't think Kuzma means the stylus does not deflect at all at .55Hz, that would defy physics.” Furthermore, Richardkrebs assumption with regard to Bruce Thigpens views on eccentric records are not supported by what Bruce Thigpen actually says in the ET2 manual. 05-20-13: Richardkrebs
BT uses at 30cu cartridge in his manual to calculate horizontal Fr. The arm weight he uses is 30gm plus 7gm for the cartridge. We have to assume that he is ok with this combination and that he is not worried about cantilever deflection on eccentric records. This assumption again is just plain wrong. I quote from Bruce Thigpen’s ET website: ET2 Manual page 47 :
“if you like to play severely eccentric records, ones with run out greater than 1/8th of an inch, then we suggest you use a low mass pivoted arm.” In summary, Bruce Thigpen is very much of the view that the horizontal effective mass should be kept as low as possible, and the decoupling employed to minimsie fundamental resonant peaks at FR and 3xFR. He has also expressed his view that increasing mass increases distortion, and I quote Bruce Thigpen - Bruce Thigpen:
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge, Thekong , I trust this clarifies the queries you raised. |
Richard/John47 thanks for making me curious about the damping trough again. Arrived the in mail one kit from Bruce. This kit reminds me of my flu shot ?I don’t like needles and syringes. But it went on real smoothI think Frogman still has his paddle lifted not touching ? I think SLAW is however still liquified ? Added 1 CC per Bruce’ instructions – paddle just touching. Its been over 8 years for me in using one. Will report back later ... so far pretty good ! Cheers |
CT0517
Based on my direct experience I encourage both Richard and Dover to order some loose leaf springs and a Two I Beams from Bruce to make up a double and triple I-Beam setup.
I look forward to impressions of a low compliance cartridge with the double and triple leaf spring. I modify my recommendation. It applies to Dover only. RK you have come down too far a path with your Krebs arm. You are truly enjoying it. I would never ask you to do something unless you are curious yourself. If you did pursue it you would need to implement a wiring scheme similar to Frogmans - to be the least intrusive on the ET2 based on your plinth design. Dover is about to reacquaint himself with an ET2 and a sound that is very .. well I really like the word that Spock15 used alot ....persuasive. I am sure his system must have changed in the years that have passed. Cheers |
Welcome to the thread Ha_ha_he_man.
Not a bad moniker :^) |
05-19-13: Ha_ha_he_man
Hi,
I was wondering when someone will add something useful to this thread that is more in line with modifications with results as opposed to a subjective debate?
Regards
Alx
Ha_ha_he_man Alx – Much is covered at the beginning of the thread. Based on my 10 years now with the ET2 and ET2.5. The recently discussed aluminum gooseneck is very nice but it is unique and costs a lot to make (labor wise). A few hundred dollars. I received only a few emails of interest so far. I am willing to pursue reproductions if more interest is shown. The biggest mods in my 10 years with the ET2 and ET2.5 has been the quality pump, wiring loom and the leaf spring mod. For those reading who do not own this tonearm. The ET2 is like a race car. It can be tuned for our rooms/gear which represent the different tracks. For a plug and play audiophile this can represent disaster. A bad nightmare. If you are plug and play and your dealer sets up your cartridge for you or a friend does it – stay away. It must be obvious by now to anyone reading here that if your are using an ET2 or Et2.5; you need to be thinking about what you are doing. If not mistakes will happen; the poor cartridge is always the victim; even though we feel bad ourselves about it. So many adjustments can be made. RichardKrebs
This is very hard to reproduce and I do not hear this effect with light linear arms when carrying low compliance cartridges. Richard your arm started life as an ET 2.0. We have already discussed here how for a really low compliance cartridges the ET 2.5 works best with the double or triple leaf spring. 05-16-13: Dover
Spock15
I currently own an ET2, Naim Aro & Hadcock unipivot and have just sold off my Bluenote Borromeo ( Titanium tubed unipivot ). Congratulations Dover on reacquiring an ET2. Frogman introduced the leaf spring mod to us early on in this thread. One is able tune this tonearm with different leaf springs (single, double, triple) corresponding to the stiffness of the cantilever being used, and the reactions of the resonances in each of our rooms; and to stay within BT’s decoupled design. Based on my direct experience I encourage both Richard and Dover to order some loose leaf springs and a Two I Beams from Bruce to make up a double and triple I-Beam setup. I look forward to impressions of a low compliance cartridge with the double and triple leaf spring. I have already mentioned here I base my vinyl tuning on what I hear with master tape dubs at 15 IPS. I start the LP then 10 seconds later the tape. I toggle between the two. I don’t have any issues with my XV1 when I use the double and triple spring in my room. I believe you can have your cake and eat it too with the double and triple leaf springs and to stay within Bruce’ genius design. Chris,
The thicker spring results in a higher resonance frequency. Thanks
brucet Chris,
You always want the horizontal natural frequency of the counterweight to be less than the cartridge/arm resonance, this is the case 98% of the time.
The natural frequency of the I-beam/leaf spring depends on the thickness of the spring, the amount of weight, and where the weight is on the beam. The natural frequency goes down as the weight moves further out on the beam which is where we want it to be.
brucet Cheers |
Thank you all for the detailed explanation!
|
Thekong. The answer to your question regarding frequencies impacted by horizontal Fr is shown in the attached graph. From memory your Horiziontal Fr was around 5hz with the A-90. So substitute 5 for 1 on the x axis and scale up from there. At 15 Hz (3) the rise in response is almost zero. This is what BT was talking about when he mentions 3xFr. It could be that the perceived improvement in bass performance of subsequent Rockport arms has more to do with the wand, gooseneck and counterweight arm stiffness, rather than total weight. Different bearings make virtually no difference to this graph since it is the mass that the cartridge has to push sideways that counts. The flavour of different arm bearings, however, is another matter entirely. The various curves are showing different values of Q (damping) Note the level of damping makes virtually no difference at frequencies of 3x Fr and above. This does not mean that we can ignore the amplitude at resonance, since it is shaking the arm and this has an impact in the audio spectrum. FM and AM modulation. Bruce reduces this amplitude by decoupling the counterweight. It is an elegant, brilliant solution. Others damp the resonance as I have done. The oil trough, way less elegant, is also a very effective way of doing this. Both methods reduce FM and AM artefacts. http://s1173.photobucket.com/user/CT-993/media/ResonanceGraph_zpsdd78e0f4.png.html?sort=2&o=7What this means, as Spock15 says, at 3xFr and above the arm appears to be solid to the cartridge. We want the cantilever to move not the arm. Now look at frequencies below Fr. At say 0.25 Fr we get transmissibility of 1. What this means is that, with the compliance of the cartridge used, the whole arm moves sideways. The cantilever does not deflect. This is important for eccentric record issues. In other words stay above a horizontal Fr of 3hz. (4x 0.75hz) ) 0.75 Hz being the frequency seen with an eccentric record ay 45rpm. Putting this another way. BT uses at 30cu cartridge in his manual to calculate horizontal Fr. The arm weight he uses is 30gm plus 7gm for the cartridge. We have to assume that he is ok with this combination and that he is not worried about cantilever deflection on eccentric records. When using a 10cu cartridge we can increase the horizontal mass of the arm to 111 gm and have the same peace of mind about cantilever deflection with eccentric records. The cartridge is 3x stiffer so we can push around 3x the weight. It is that simple. Forces on the record groove wall are another thing. We use a stiff cartridge this is the price we pay. Don't play heavily eccentric records. Ha_ha_he_man. What I hear with a heavy linear arm is this... The music takes on mass. Individual notes are solid. This is not to be confused with "heavy" in the derogatory sense. A live struck triangle has this mass. One can imagine walking up to the sound of it and holding it. It would have mass and a textured surface. This is very hard to reproduce and I do not hear this effect with light linear arms when carrying low compliance cartridges. |
Oh dear, Andy Payor doesn't know what he's doing either.
He's just added distortion by incresing the weight of his arm.
The world according to Dover. |
Thekong, hi there, Hi Dover,
You have mentioned that too high a horizontal effective mass would result in a raised bass response by 6-12db. So, in what frequency range are we talking about (the Fr at below 12Hz?)?
I just wonder if the high horizontal effective mass is the only consideration here, and whether other factors, such as the design of the air-bearing, would make a considerable difference in the outcome. In short, does that only apply to the ET design, or also to the Rockport and Kuzma etc?
I asked because my Rockport 6000, already has a high horizontal effective mass of 80g (with the lightest counterweight, and excluding the cartridge), but yet MF found it lacking in the bass! The upgraded 7000 and Sirius III arms added even more mass to “cure” this problem! Just to clarify there are 2 separate issues with the Krebs set up - 1. Removing the decoupling of the counterweight This is where Bruce has tested extensively and posted his results on his website. The removal of the decoupling increases the amplitude of the fundamental resonance by 6-12db. Now if you read the Audio review posted by John47, bottom of page 5, you will see that with the Talisman they measured 2 resonances at 4hz & 9hz. This illustrates how the decoupling system works, by splitting the resonance it actually reduces the peak of the fundamental resonance and results in a flat response in the bottom end. Now Richard is saying that doesn't matter because the resonance is outside the audio band. That statement is not correct because a large resonance at the fundamental frequency will generate signal out of phase that imposes itself on the audible range, negatively impacting timing accuracy, imaging etc. A bass note for example will have harmonics that carry right through to the high frequencies. The preservation of phase at all frequencies is critical to presenting an accurate soundstage, harmonics etc. This is precisely why Frogman, Ct0517, Slaw and myself hear better timing with the counterweight decoupling tuned properly. Frogman has described hearing more bass notes. The other problem generated by the resonance is tracking and tracking distortion - if you have instability at very low frequencies there will be a negative impact on tracking, whether you hear it or not. 2. The other issue is adding significant mass. Now Richard is partially correct when he says that damping with oil, wire, air hoses etc will also help to control resonant peaks at FR. But the real issue is that there are 2 downsides to this approach of high mass - Firstly by carrying this additional mass the cantilever is now pushing a much higher weight. This means that on eccentric records the cantilever deflection will be much higher, and there is increased distortion from the coils moving into a non linear phase. This is one of the primary design considerations Bruce has endeavoured to address by keeping the mass as low as possible. It is wrong to think of this particular issue as a bass problem. The biggest negative is the phase distortion and tracking distortion which impacts the whole range. Secondly in my experience damping tends to slug the sound, as you heard at your friends place. There is a logical explanation for this - by loading up the cantilever it becomes less responsive, less nimble. By loading up the horizontal mass, you are increasing the inertia of the arm, it resists movement, the cartridge cant follow the groove, the cantilever flexes more, more distortion. In a nutshell you might get a more solid bottom end with more mass, but in my experience it comes at a cost - loss of speed and the preservation of accurate phase and time throughout the whole frequency range is compromised. Sometimes in audio less is more. Bottom end extension is not much good if it is muddy and out of phase. High frequency extension can tell you more about how hard a drum is hit than the actual fundamental. From this you can see that having the fundamental in phase with the upper harmonics is critical. In my early days of audio I reckon my Proac Tablettes, which rolled of from 70hz could tell you more about whats happening at 30hz simply because they were very quick compared to many full range speakers - and before the naysayers here get in - I had Proac Studio 3 EBS monitors at the same time. Bearings of course play a role, not just the pressure but the design and airflow etc. An air bearing can be stiffer than one at much higher pressure due to bearing surface area, etc. In the TAS review of the Kuzma/Walker clearly to the arms have different strengths and weaknesses. The Kuzma supposedly is very strong in the bottom end, the Walker appears to be more nimble presents timing better. Pretty hard to work out why these differences occur, because we dont have enough information. In my view given that you have both the Rockport and ET you should enjoy the benefits of both approaches - why anyone would try and convert the ET2 into something that it was never intended to be - a high mass arm - is beyond comprehension. I know at least one reviewer who considers the Kuzma is not as good as the ET2. With regard to Fremers comments on bass response, I dont take much notice. The chances of him getting the ET2 set up correctly are pretty remote, simply because he is time constricted. About the only reviewer that I would trust to ensure that the ET2 is set up correctly would be Martin Colloms due to his technical knowledge and insght, and in the early days of audio reviewers spent many months with gear, not days/weeks. |
Hi Halcro,
Thanks for the information again! As I can’t use wall mount in my room, I have never experience its effectiveness!
My room has suspended concrete floor. According to the specification, the pneumatic table could isolate up to 85-90% of the vibration at 5Hz, and 97% at 10 Hz, it has worked out very well for me! I certainly could hear the improvement in background blackness with its use!
Thanks! |
Dover wrote:
A conventional pivoted arm with an effective mass of 14g with a cartridge of 9g will have a total effective mass of 23g.
The standard ET2 has a horizontal effective mass of 34g or 52g with the damping mechanism.
With your addition of lead and removal of the decoupling, and added fluid damping, your altered ET2 has an effective mass of approximately 114g - 4 times the effective mass of a conventional pivoted arm.
Readers should try to imagine waking around with the weight of three adults sitting on their shoulders, and pretending the weight is of no consequence.
This is what the cantilever has to endure with the Krebs alterations to the ET2. Sorry Dover, with respect, I hear what you are saying but I don't think that this is what a cartr stylus really "sees". Static Mass is one thing but Effective Mass is something slightly different... the latter is the "inertia" or the reluctance of the tonearm (pivoted or sliding) to move, as seen by the stylus. ie. At frequencies above Res Freq, the tonearm is effectively an immobile/stationary object or load, as seen by the stylus...which is a good thing, because you want a stable platform to trace the groove, right? Referring to your analogy, for example, the tonearm should not be "walking around", it should be standing absolutely still... & having 3 adults sitting on your shoulder ;) ...is going to help hold the cartridge steady. (The only potential problem with ultra low Res Freqs is the danger of coinciding with TT suspension/support/floor modes.) |
Hi Thekong,
In a suspended reinforced concrete slab......there can be frequencies from 5-10Hz and higher.
In a suspended timber-framed floor they could get up to 10-16 Hz but would not normally get as low as the concrete.
Of course....the 'creaking' we can often hear in suspended floor structures as they 'move' whilst we are in bed at nights......are of a far higher frequency.
It's really the very low frequencies doing the damage as Structure-Borne Feedback as they are indicative of 'movement' within the floor structure. |
These stresses result in subsonic low-frequency Structure-Borne feedback which passes easily into equipment racks, support stands and into the turntable plinths sitting upon these racks/stands. Hi Halcro, Thanks for the information! So, any idea what is the frequency range of these structure-borne feedback? Thanks! |
The most extremely test of this sort that I have seen was that, while following your initial settings, instead of jumping around the TT, you kick on its stand! This is not a test for Structure-Borne Feedback. It merely places a Dynamic (hitting) sound source into a structure. I have never seen a scientic correlation between 'Impact' sound sources and Air or Structure Borne sound sources? It is like the ubiquitous "Boink Test" that some audio reviewers used to do........tapping on the plinths of their turntables to see how 'immune' the turntable is feedback? Chris' test of jumping on the floor around the turntable is a little more viable as it transfers the impact-induced source into Structure-Borne feedback within the floor........ however the form of that feedback is quite different to that which our systems are normally subjected. Any suspended floor system (timber or steel-framed or reinforced concrete) will be subjected to Structure-Borne Feedback because of the stresses and deflections caused by the structural spans.....as well as the materials used in the floor construction. These stresses result in subsonic low-frequency Structure-Borne feedback which passes easily into equipment racks, support stands and into the turntable plinths sitting upon these racks/stands. That's why a wall-mounted turntable shelf is the best way to minimise this. |
TEST FOR STRUCTURE FEEDBACK ……. Start jumping up and down right beside your TT……. Hi Ct, The most extremely test of this sort that I have seen was that, while following your initial settings, instead of jumping around the TT, you kick on its stand! :-) It was performed on a Rockport Sirius III at the agent, and yes, it was pretty much silent from the speakers! That stand was actually an OEM pneumatic table by TMC, and I am using a similar one under my Capella II. Unless you kick it hard enough that the whole stand / TT assembly (roughly 400-500 lbs.) moves over the floor, you can hardly hear any thumping from the speaker indeed! Hi Dover, You have mentioned that too high a horizontal effective mass would result in a raised bass response by 6-12db. So, in what frequency range are we talking about (the Fr at below 12Hz?)? I just wonder if the high horizontal effective mass is the only consideration here, and whether other factors, such as the design of the air-bearing, would make a considerable difference in the outcome. In short, does that only apply to the ET design, or also to the Rockport and Kuzma etc? I asked because my Rockport 6000, already has a high horizontal effective mass of 80g (with the lightest counterweight, and excluding the cartridge), but yet MF found it lacking in the bass! The upgraded 7000 and Sirius III arms added even more mass to “cure” this problem! Not meant to be argumentative, just want to learn more! Thanks! |
Dover has repetitiously stated richardkrebs ADVOCATES adding lead mass to ETs
This is incorrect.
Mr Krebs openly told the forum how he sets up HIS arm for his LOW compliance cartridge, and the reasoning behind it.
He (RK) suggested others could try it to educate/inform themslves, adding to the collective knowledge of posters, because IT IS EASILY REVERSED.
RK has not tried to CONVINCE others to follow his setup. |
Hi,
I was wondering when someone will add something useful to this thread that is more in line with modifications with results as opposed to a subjective debate?
Regards
Alx |
Dover.
- The error you repeat, is saying that my arm exhibits a rise in bass response of 6-12db. I'm pretty sure that most of the readers here would not call 5Hz bass. I can't hear that frequency and my system certainly cannot reproduce it. The arm has always had some method of damping. This reduces the amplitude of resonance at Fr. If you ask BT, he will say that the amplitude falls away to be benign at 3x Fr. Just over 15hz in my case. A frequency which some may call Bass, but one which I doubt my system can reach down to either.
-The change in shape of the resonance curve I refer to is clearly shown in the graph BT published with the oil trough manual. It is not a smooth standard deviation type curve. There are bumps and hollows on the slopes. This is caused by other structures resonating at frequencies near the fundamental.
-BT does not increase the horiz effective mass by 18gm when he adds his oil trough and nor do I with mine. He adds 18gm to the total weight of the arm. The effective mass is increased by the weight of the paddle. Well under 1 gram on mine. This makes my arm around 96 gm when carrying the Shelter, not 114 as you state.
You repeatedly try to paint the weight of my arm as being an outlier in linear arms and that my arm is singular in being so heavy. It is not, as we have seen in this thread. Some fellow posters own these heavier arms. Criticize my arm and you simultaenously criticize theirs.
-BT uses a very elegant method to reduce the FM and AM interfearance in the audio band caused by a high ampltude Fr. He decouples the counterweight which reduces the amplitude at Fr. Other designers use another method, they damp the arms horizontal movement which also significantly reduces the amplitude at Fr. This by using an oil trough, the lead out wires, the air line or a combination of these. It is simply another method of dealing with the problem. Both are valid, both have their advocates and detractors. This is the nature of our hobby.
-Chris has clearly enunciated the improvemmets in the bass articulation when he applied my goose neck design. Could it be that the problems you hear in the bass region when you locked the counterweight were simply due to the compliance of the gooseneck being laid bare, combined with maybe insufficient damping? |
Chris.
Brilliant test idea you used for checking the smoothness of the pump air flow.
I smoked my current pump running it at a higher pressure. Will definately be trying your idea out when it's replacement arrives. |
'Audio' review: further to my comment about enlarging individual pages on Chris's site.
I've found it better to use View(Toolbar)> Zoom > Zoom In, and Ctrl + or Ctrl- |
Re the 'Audio' review. When you call up the pages on Chris's site, I've been alerted to what can be confusing.
Call up one of the pages, then hit the + button at the bottom right of the page TWICE, and readable it will be. |
Holy multi-post Batman ! You guys are making the nice people on the audiogon help desk work overtime. |
This is how I test my vinyl setup for Structure Feedback and my ET2 (2.5) Pump for Noise and Vibrations.
I am interested to know what techniques others use. I’d like to learn different ways of doing this.
TEST FOR STRUCTURE FEEDBACK
Some people think that direct sound waves affect our cartridge. Some people put plastic shields around their turntable. If you think that direct air waves really affect your cartridge “trying yelling at your cartridge and see what happens” infamous quote from Audiogon user Halcro.
Can you hear yourself through your speakers when you do this?
Henry – if you see this I hope you don’t mind me quoting you.
My test for structure feedback is to set up the TT on mute and lower the stylus onto the lead in groove. Record not spinning. Unmute the phono and turn to a level that is considered high for your room.
Start jumping up and down right beside your TT. Pretend you are dancing with your spouse. Actually invite her/him in and jump together with no music. Just be prepared she may ask you to boogie to real music later as she gets warmed up. If your setup survives this test you should be good to go.
TESTING THE PUMP for NOISE and VIBRATIONS.
This test should actually be good for any air bearing linear tracker that uses a captured bearing like the ET2 and ET 2.5.
No jumping this time just listening.
Same as the above in regards to muting your phono with a still record and unmuting but with a BIG difference.
1st – DO NOT turn on your pump and lower your stylus onto the lead in groove. Unmute and turn the volume up. Listen to how quiet it is. When finished mute system and raise the ET2. I say raise the ET2 because I don’t know how good your pump and setup is. More on this later.
Now have a friend turn on your pump and repeat the above procedure and lower the stylus again. Is there any noise in the background now that has been transmitted down the airline into your system that was not there before?
Is it the same level of quietness, or is there now a little more background noise with the pump on. If you are using a regular aquarium type pump and no surge tank you will hear differences. For those with good pumps and a properly setup ET2, ET 2.5 there is no need to raise the stylus or unmute after listening with no pump. Have the friend turn your pump on and off while you have your ear on one of the speakers.
If you are introducing noise with your pump down the airline you are not hearing what the ET2 can do. The sound is being glazed over by air noise vibrations from the pump.
I came across this years ago – maybe 8? by accident. I had an actual small ground hum type noise and could not for the life of me figure out how to solve it. I tried for two days. I could just hear the pump at the time in the other room running faintly. It was a Medo AC110.
Finally after a couple of days of trying to fix the problem, I unplugged the pump and I tried the above test. No more noise. Damn! I substituted my backup Medo pump at the time and all was quiet again. The bad pump was still delivering PSI but had a piston problem sending noise and vibrations down. I also found back then that a long run of air tube coiled up also helps to minimize the vibrations.
I didn’t discover the above problem until I had swapped in cartridge, wires, amps, preamps, speakers first ! That set me on my pump journey the next few years and I ended up with the pump I use now.
So how do you guys test for structure feedback and airline noise/vibrations with an air bearing?
Cheers. |
This is the story of an audiophile called Dorothy and her ET2, a tonearm she has owned for many years.
For the first few years she used a light MM cartridge and used only 2 of the 4 lead weights supplied positioned in the middle of the I beam. “It looks visually balanced better this way to me”, Dorothy said. She did have a quick skim through the ET2 manual but ....oh!..... so many pages ....some really technical “guy” must have written that for sure she thought. Anyway.....how she set it up sounded good to her... so she left it this way for a few years.
Then one day she decided to buy an MC cartridge. She noticed it was quite a bit heavier. Instead of moving the existing weight further out on the ET2 I Beam (as the ET2 manual says to do) - she put on the other two weights she had stored in her drawer all this time; so they could meet up around the middle of the I-beam again. She was after all comfortable with this middle of the I Beam positioning. “It just looks visually better balanced this way” Dorothy said. It sounded good again. She was happy.
Then later on she was reading on the internet about some ET2 owners who just couldn’t stop fiddling with their ET2’s.
"Must be all guys for sure” Dorothy thought to herself.
But she was intrigued about how they were discussing the aspect of loading up the weight on the I-Beam. They were putting more thought into it; putting just enough weight on so that the weight was at the end of the Ibeam – no matter what cartridge. Some of these guys were even crazy enough to change cartridge screw sizes to accomplish this.
“Well” she thought to herself “maybe there was a screw loose somewhere else with some of them?”
But she was intrigued ....she could resist no longer. She tried it and did what was required to get the weight out at the end of that “pirate plank” even though it did just did not look right to her.
Lo and behold more music “sprang” forward ! She said to herself “all these years I was listening to my ET2 and I was loving it; But now... well I love my ET2 even more!”
She felt good about herself.
Does this story have a lesson ?
Yes, Dorothy felt good about herself, but it wasn’t because her favorite songs sounded even better to her.... which they did; no, it wasn’t the main reason. You see Dorothy always knew that she could listen to her favorite songs anywhere; even in the car and they would always put a smile on her face. It was about the music itself after all.
No, what made her feel real good – was that she had learned something and understood more about how her ET2 actually worked. That learning and knowledge is what made her really feel good. She then said to herself “maybe I should read the ET2 manual that guy called Bruce wrote? ”
Right after thinking that another thought came into her head. “If only my boyfriend was as easy to tune as this ET2” |
05-17-13: Richardkrebs
Dover
I do wish you would stop repeating your fundamental error ad nauseum. I am not aware of any errors on my part. Please read my last post. It outlines the errors you have made. Let’s address the fundamentals: The ET2 has a unique patented decoupled counterweight. The decoupled counterweight is damped at its natural resonant frequency of 2-5hz. This decreases the rise in frequency response at the fundamental resonance. ( page 9 of the ET2 manual ). So with your cartridge a standard arm would have a fundamental resonance at 8hz, and the decoupled counterweight reduces the amplitude or size of this resonance. Removing the decoupling as you have done will see an increase in the resonance of 6-12db – as shown in Bruce’s testing, documented on his website. Now you state you have added some 62+g of mass to your ET2 and removed the decoupling. So there are 2 points here: 1. Removing the decoupling increases the fundamental resonance by 6-12db. 2. Increasing the mass has reduced your FR to 5hz. One can see that by adding mass you have placed the fundamental resonance in the same zone as the natural resonance of the decoupled counterweight. This would be a disaster as the 2 resonances will likely sum together to create a large one. You can deduce from this that removing the decoupling not only takes out a fundamental design feature of this arm that provides a flat response in the bass, it actually compounds the problem of the FR peak and makes it doubly worse. Now let’s assume that your system has no response below 30hz, just for arguments sake, not that I’m suggesting it does. The reality is that phase shifts at fundamental resonance ( bass in my language ) will affect the rest of the frequency spectrum. In other words it affects the mid and highs. ET website
If a tonearm/cartridge system has a substantial rise in response below 20 Hz as most do, the phase response at the low end will be shifted and phase shift will occur beginning at 2 to 3 times the resonant frequency down to Fr. The time in which low frequency signals come from the tonearm will be shifted slightly with respect to mid-range frequencies within the audible range and substantially shifted up to several periods at resonance. One can clearly hear these distortions when adding mass to the ET2 and removing the decoupling spring. 05-17-13: Richardkrebs
Bruce measurements show that this rise in response is reduced by 8db with the addition of an oil trough. This in test conditions which used a deliberately high Q and a low compliance cart. The amplitude of resonance decreases the further you move away from Fr. BT suggests that resonance effects frequencies up to 3xFr. This testing is irrelevant in your case because of what you have done to your ET2. The testing was conducted with a standard ET2 with a decoupled counterweight and fluid damping added - the total horizontal effective mass was approx. 54g. You have altered your ET2 by removing the decoupling of the counterweight, which increases FR by 6-12db and increases the horizontal effective mass by 32g. You have also added 30g of lead to your tonearm. Your tonearm weighs approx. 114g compared to the 52g tested by Thigpen. Thigpens test results cannot be applied to support your argument that your arm does not have a rise in response in the bottom end because you have doubled the weight of your arm and removed the decoupling mechanism from the counterweight. What you have not addressed, other than the discussion on the impact of FR, is the tracking distortion that is generated by increasing the mass of the arm, in your case more than doubling it. I quote from Bruce Thigpen: If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge, You have doubled the weight as seen by the cantilever. A conventional pivoted arm with an effective mass of 14g with a cartridge of 9g will have a total effective mass of 23g. The standard ET2 has a horizontal effective mass of 34g or 52g with the damping mechanism. With your addition of lead and removal of the decoupling, and added fluid damping, your altered ET2 has an effective mass of approximately 114g - 4 times the effective mass of a conventional pivoted arm. Readers should try to imagine waking around with the weight of three adults sitting on their shoulders, and pretending the weight is of no consequence. This is what the cantilever has to endure with the Krebs alterations to the ET2. |
