[rcag_ils]

It may be a bit too much to ask.

With all the tonearms I have collected and plan on installing, I am in need of an template that would allow me to set the distance/position precisely, from arm to platter spindles of various tonearms and turntables. All the tonearms I have did not come with their mounting plates.

Any suggestions are welcome.

[neobop]

Hi,
A Dennesen arm hole locator is the only device I know of that might help. You could reverse engineer a Dennesen Protractor or a Clearaudio, to scribe an accurate arc for your center of the mounting hole.

I just wrote a long description. I got sidetracked and didn't get it posted in the alloted time.     I'll get back to you on this as soon as I'm able.
neo

[jimdgoulding]

Oh yeah, I hear ya.  There must be something about this we, or I, don't know.  Wayner?  Anyone?  Buy a TT without an arm and you have to coordinate the mounting plate setting, if you have the option, or drill a hole for your arm's optimum setting.  OMG, can't you hear the digital section belly laughing!  Shit, I don't blame them, but for my old empirical experience.  I nominate Warhol as the digital poster boy.  Dots can emulate reality, sure nuff.  But, they ain't vibration.  And what isn't.

[neobop]

Well, it's really not as hard as it seems, with or without a Dennesen arm mounting hole locator. If you google Dennesen Soundtractor or protractor, you'll get an explanation of the alignment device. It's one of the tools I use sometimes for alignment. It looks like a Clearaudio protractor that has an arm which is adjusted to to have a pointer which you located over the intersection of the arm pivots. That determines where on the platter the protractor rests. Unlike the Clearaudio, the Soundtractor will give you a perfect Baerwald alignment with 1 grid. Contingent of course, on being able to accurately sight the intersection of the pivots.

The mounting hole locator is a ruler like devise that fits over the spindle. It has a slot in the middle with a slider. The slider has a hole that is aligned with the calibration. It's easy to exactly locate the hole at a given mounting distance and lock the slider in position. A pencil or scribe is then inserted in the aligned hole and you can mark an arc on the armboard that will give you the exact center of the mounting hole. Any hole cut with the center anywhere along that arc will be at the correct distance.

I don't have a mounting hole locator. What I do is sort of reverse engineer the Soundtractor. I mount the arm of the Soundtractor upside down, so the arm is close to the platter. Then I use a ruler and locate the little hole for the pointer, exactly at the mounting distance (from center spindle). Then I use a pencil in the hole to mark the arc. Your measurement can be easily checked with a ruler, sighting from above.

You can use a similar technique without a Soundtractor, but it's difficult to get an arc. Figure out first where on a theoretical arc, you want the arm located. It's not too hard to mark a single point that has the correct distance. You might have to do this a few times to get the perfect spot.

One of the nice things about using a Soundtractor, Geodisc or 2 point alignment gauge, is that your alignment is based on where the arm is actually located. Using overhang or a dedicated protractor will only be correct if your arm is mounted at the perfect distance.
neo

[Wayner]

If you can say that most or all of your arms are generally considered 9" arms (as opposed to say a 10.5".  like from VPI, others), then the only concern is that the distance you pick will allow the proper overhang to set the cartridge to achive the null points of your choice (Loefgren B is popular). So, in my mind, there is not a universal mounting distance, because all arms are not made the same, distance wise. I believe most of this is influenced by the original design intent, by the arm designer, to achieve his desired "perfect" cartridge position. Baerwald, for example, came up with what he considered the ultra, ultimate "perfect" numbers, that later were challenged by others. His numbers were 228.60mm for platter spindle to tonearm pivot center. That would give you a 18.173 overhang with a 24.128 degree offset angle.

Other manufacturers have been using their own numbers. VPI on my Hw-19 has 210mm spacing, Technics uses 215mm, My Sony has a 200mm spacing. The problem is, if you were to take, for example, my Sony's arm and drill it for Baerwalds spacing, I might not have enough slot length in the headshell to achieve the correct alignment position.

This is the balance you must look for. In almost every case of turntable I own, I can achieve a correct alignment, so what I would do if I were you is to use the spacing recommended by the manufacturer.

Wayner 

[rcag_ils]

Most arms effective length are 9", S shape, or straight. But one time I mounted a S shape arm on a board drilled for a straight arm, it didn't work.

Then I used my Geodisc and my eyeballing technique, the first hole was off a bit, and I had to expand the hole to make the arm worked.

This time I bought a sheet of 4'X8', 3/4" thick MDF, that would allow me to make at least 20 armboards, so one of these days, I'll get it right.

I'll check on the ideas from you guys, and thank you for the inputs, keep them coming, I want to do it right.

[Wayner]

Most arms effective length are 9", S shape, or straight. But one time I mounted a S shape arm on a board drilled for a straight arm, it didn't work.
Then I used my Geodisc and my eyeballing technique, the first hole was off a bit, and I had to expand the hole to make the arm worked.

This time I bought a sheet of 4'X8', 3/4" thick MDF, that would allow me to make at least 20 armboards, so one of these days, I'll get it right.

I'll check on the ideas from you guys, and thank you for the inputs, keep them coming, I want to do it right.

That is probably because the pivot center to spindle center was incorrect. There is no other distinction to this between straight or S shaped arms. As an example, my Rega RB300 arm requires a 222mm spindle to pivot distance. That distance alone is longer then many tone arm's effective length, so that wouldn't work if I wanted to install the Sony's arm for example (that needs to be at 200mm). So yes, it wouldn't work, but it's not because it's a straight or S shaped arm, it was out of it's design constraints.

The only difference (geometrically) between straight and S shaped arms is their appearance. In theory, S shaped arms were to cancel out wave induction up the tone arm by it's physical shape. it also had better eyeball (and then mass) appeal to the general public. A straight tone arm "looks" wrong 'cause it's head is usually crooked at the end, and someone surely would think that it was  made wrong. The arm could look like an accordion or radiator, if it could be ridgid and put the cartridge where it belongs, at least geometrically.

Now, if you are going to mount an arm, let's use the Rega RB300 as an example, that needs to be 222mm from the center of the platter. This will sound funny, but I really don't care if you are off by a mm or 2. It could be drilled at 223 or 221, it really doesn't matter. What matters is that you know exactly where it was drilled at. That means that marking out an arm board or a plinth is the wrong approach to the project, and if you think you are going to do it yourself, that could be another mistake.I would take the table (with arm board, if it has one) to a machinist with a vertical end mill. Let him dial in the platter bearing so that it's position is X = .000, Y = .000, and then let him drill the tonearm hole at the required distance (in the case of the Rega RB300, 222mm). Tolerances of +/-.001" would be nice, and the hole tolerances are important too, so that the arm has no "slop" when it's installed into the mounting hole(s). This known distance is all important for the rest of the cartridge set-up. You will know the exact overhang required, the exact offset angle required, life will be good.

Editorial: For those that think the 2 point alignment system alone gets you there, I beg to differ. You can be off by 1mm using this technique alone, one way or another. You must first dial in the overhang. It will remove error. Going back and forth from overhang to null point locations will verify that the stylus is in the correct arc position to achieve the lowest fundamental tracking distortion. The most critical aspect of alignment is the cartridges offset angle (in relation to it's overhang), but mere decimal points of a degree will cause a rapid increase in tracking distortion. It is the most sensitive of all settings and the hardest one to set. That is why we are vinylphools, as John the chair (cart) Guy calls it.The more precise the alignment, the better the vinyl, IMHO.

Wayner 

[Ericus Rex]

If you get the correct spindle to pivot distance all else falls into place.  You don't need a fancy protractor.  Your arms all should list that distance in the manuals.  If you can find a way to fairly precisely mark that distance (+ or - 1mm) with digital calipers or a modified ruler with a pencil somehow attached that will make your life much easier.  Technically speaking, you can mount your arm anywhere on the table as long as the spindle to pivot is correct (remember some Micro Seiki tables can mount up to 4 arms depending on the model).  If you're way off from the manufacturer's intended position the only problem you might encounter is if you try to line up the arm (when at rest) parallel to the side of the table.  If you're WAY OFF you might hyper-extend the arm at rest.  Some manuals will show the angle of the arm at rest relative to spindle/pivot line to avoid this.  As Wayner mentioned, overhang should then be very carefully set.

[rcag_ils]

How do I go about to find the spindle to pivot distance for various arms?

[neobop]

Editorial: For those that think the 2 point alignment system alone gets you there, I beg to differ. You can be off by 1mm using this technique alone, one way or another. You must first dial in the overhang. It will remove error. Going back and forth from overhang to null point locations will verify that the stylus is in the correct arc position to achieve the lowest fundamental tracking distortion. The most critical aspect of alignment is the cartridges offset angle (in relation to it's overhang), but mere decimal points of a degree will cause a rapid increase in tracking distortion. It is the most sensitive of all settings and the hardest one to set. That is why we are vinylphools, as John the chair (cart) Guy calls it.The more precise the alignment, the better the vinyl, IMHO.

Wayner 

You're wrong about that Wayner. I'll explain why. Suppose you have a Rega arm. The factory inner null point is very close to a Stephenson alignment, (Rega 60.0 & 114.7mm). Suppose you want to use a Baerwald alignment. If the headshell slots are long enough for the cartridge, you would have to move the cart forward at least 2mm. It would be impossible to use overhang for alignment because the factory 14mm overhang would change to at least 16 or 17mm.

If a cart lines up on both grids, it is aligned properly for that given alignment, regardless of overhang and offset angle. The arc might be changed because of a different effective length, but geometry, that is tangency of the cartridge to the groove is a relationship that is defined by null points. Null points are the 2 places along that arc where the cart is precisely tangent to the groove, and there is 0 degree error.

Overhang is only relevant if the arm is mounted exactly at the prescribed distance, and you use the factory alignment. If you want to try a different alignment, then put away your overhang gauge. It will be wrong. No, you don't need a fancy schmancy expensive protractor. You can download  protractors of your choice at Vinyl Engine.com for free, or buy any one of a number of inexpensive 2 point protractors. 

Offset angle is the angle the cartridge is set, compared to the pivot. It is the reason that pivoting arms require anti-skate. It is also thought to cause a torsional effect on the arm or cantilever. But this has NOTHING to do with the geometry of the cartridge to the groove. If it changes a degree or two, it really won't matter if, and only if, your cantilever is aligned correctly for a given alignment.

I'm not recommending changing from factory mounting distances or alignments. But people do change alignments successfully, all the time. Any two point protractor will give you the correct alignment for that type, if your headshell will accommodate. This is regardless of mounting distance, or a difference in mounting distance from factory specified. It's simple geometry.

If anyone needs manufacturers specs, you can probably find them here:
 http://www.vinylengine.com/tonearm_database.php?make=Rega&sort=8&ascdesc=DESC&search=search&mdl=&eflo=&efhi=&mdlo=&mdhi=&ohlo=&ohhi=&amlo=&amhi=&cw=&mp=

[blakep]

How do I go about to find the spindle to pivot distance for various arms?

This should be of assistance:

http://www.vinylengine.com/tonearm_database.php

[blakep]

Hi Neobop: Wayne will have to speak for himself but I took his post to be much more of an advocacy for the use of an arc protractor (which really does focus first and foremost on overhang) as opposed to the simple 2 point protractors commonly used by many. If this is what he was saying, I would agree with him.

As you point out, the overhang will change with a different alignment protocol but once one is aware of this and, providing your headshell slots have the leeway to accomodate a different alignment, achieving that overhang using an arc protractor IMO is generally the quickest and easiest way to achieve an extremely accurate alignment. Get the overhang right on the two critical points of the arc and your alignment on the null points is pretty much a given. Quick and easy as opposed to the constant futzing back and forth with a standard 2 point protractor (I hate them!).

I know that you are probably well aware of Conrad Hoffman's software, but for those that are not, it is an outstanding (and free) program allowing anyone to create anumber of custom arc protractors for virtually any arm providing one knows the mounting distance. Different alignment methods (Stevenson, Lofgren, Baerwald) with varying nullpoints, overhang, effective length and offset. For anyone interested it can be downloaded at the Vinyl Engine or from Conrad's personal page. Thanks once again to Conrad!

And, from the department of redundancy department, I also posted a link to the Vinyl Engine tonearm database in the other thread by the same name before seeing it here .

[neobop]

Hi Blakep,
One of the main points I was trying to make is that overhang and a dedicated protractor are useless if you want to change alignments. Also, they only work if your arm is mounted at the exactly the right distance. A 2 point protractor, or a device like a Geodisc or Dennesen can give correct alignment even if the arm is not mounted exactly at manufacturers specified distance.

The fact is, even if you can't achieve a given alignment with a particular cartridge, if you can get null points between say, Stephenson and Baerwald, then you'll have a decent alignment. What I'm saying is that if your inner null is somewhere between 60 and 66mm, and your outer is 120mm or less, then you'll have a good alignment. You'll have to judge for yourself if it's your preferred alignment.

All the BS about offset angle vs alignment means that it's not understood. Offset angle does have implications, but not as far as this is concerned.
neo

[neobop]

One more thing. Changing alignments from Stephenson to Baerwald to Loefgren means that you increase the effective length of your arm by about 2mm with each change. That's why overhang and dedicated protractors  won't work in this case.

[blakep]

Hi Blakep,
One of the main points I was trying to make is that overhang and a dedicated protractor are useless if you want to change alignments. Also, they only work if your arm is mounted at the exactly the right distance. A 2 point protractor, or a device like a Geodisc or Dennesen can give correct alignment even if the arm is not mounted exactly at manufacturers specified distance.

The fact is, even if you can't achieve a given alignment with a particular cartridge, if you can get null points between say, Stephenson and Baerwald, then you'll have a decent alignment. What I'm saying is that if your inner null is somewhere between 60 and 66mm, and your outer is 120mm or less, then you'll have a good alignment. You'll have to judge for yourself if it's your preferred alignment.


neo

No problem, certainly all valid points; as you say (and as I alluded to with respect to Conrad's software) an arc protractor to be effective requires that the arm be mounted precisely at the manufacturer's recommended P to S distance.

I do think that Wayne's comment/point regarding the relationship between overhang and offset is a valid one though, at least when using an arc protractor and using an alignment different from that specified by the tonearm manufacturer (and there have been many reports from users who have done so and felt they heard improvements).

Change the alignment protocol (ie. from Stevenson to Baerwald) and hence the overhang (while still achieving an effective alignment) and the offset will change as well which is why the cartridge will not sit square in the headshell and be twisted or skewed. There seems to be an abundance of confusion on this particular aspect of alignment among many vinyl users. You can have a virtually perfect alignment without the cartridge being square in the headshell and that's because the offset changes to achieve alignment (along with all the other parameters-overhang, effective length etc.) at the different null points.

If the overhang changes, the offset has to change as well.

[neobop]

I do think that Wayne's comment/point regarding the relationship between overhang and offset is a valid one though, at least when using an arc protractor and using an alignment different from that specified by the tonearm manufacturer (and there have been many reports from users who have done so and felt they heard improvements).

Change the alignment protocol (ie. from Stevenson to Baerwald) and hence the overhang (while still achieving an effective alignment) and the offset will change as well which is why the cartridge will not sit square in the headshell and be twisted or skewed. There seems to be an abundance of confusion on this particular aspect of alignment among many vinyl users. You can have a virtually perfect alignment without the cartridge being square in the headshell and that's because the offset changes to achieve alignment (along with all the other parameters-overhang, effective length etc.) at the different null points.

If the overhang changes, the offset has to change as well.

I don't use an arc protractor. But it seems to me, that if your changing alignments, which necessitates changing overhang and effective length, then the prescribed arc will no longer be valid. It will only be valid for the prescribed alignment. Validating your results with a 2 point protractor is no big deal, once you have changed. There are many Rega users that prefer a Baerwald alignment, and report a significant change. I use Rega as an example because it is in wide use, with many of these reports.

In reality, the arc will change only slightly within the range of 60 to 120mm distance from the spindle, depending on eff length of the arm and amount of difference between alignments. But using a 2 point as the final analysis removes the guesswork. Wayners comments about offset and overhang are NOT valid when changing alignments. You can not change from one alignment to another without those parameters being changed as well.
neo

[Wayner]

One more thing. Changing alignments from Stephenson to Baerwald to Loefgren means that you increase the effective length of your arm by about 2mm with each change. That's why overhang and dedicated protractors  won't work in this case.

That statement is a loaded gun. Yes, and I was speaking of theoretical geometry, you do have to plan for which alignment you want before you start drilling. My point was that the dimension it's self it not as critical as knowing what the dimension is. My ARMod is drilled so I can achive Loefrens B curve which puts the null points at 70.285 and 116.604. I can also get the stylus in several other popular curves, like Baerwalds. I probably have 3 or 4 mm to go before I run out of slot distance. That's why in my now gone original post, I said you have to be in the ball park for the curve you want to use. Again, that is also why, in my missing post, that I recommended that the arm be located with the manufacturer's recommendations. Those positions usually allow the user to select several popular null point locations and be able to locate the stylus in the correct position. And that is, as I believe you will agree, that there is no such thing as a "universal tonearm mounting template".

Wayner 

[Ericus Rex]

I see on Conrad's free site there are three protractor options:  Lofgren A, Lofgren B and Stevenson A.  Which do you guys recommend and why?

[Wayner]

Lofgren B seems to be the most popular, because of it's lower overall average tracking distortion. The overall nature of any of the versions is where the shift is, on lead-in and exit distortions, going up at the beginning and end of the record. Each one of the guys have their own version of their perfect curve, but in reality they all trade off one element for another. I think that Baerwalds numbers are the same or dam close to Lofgrens A nulls.

Wayner 

[blakep]

Lofgren A and Baerwald are actually one and the same. I prefer Baerwald (or Lofgren A) because the distortion numbers in "the middle of the record" are pretty close (but very slightly higher) than those achieved by Lofgren (B) while providing superior distortion results which are pretty significant on both the outer and inner grooves. Seems to me to be the best, most balanced approach.

Stevenson, on the other hand is supposed to be the king with respect to the inner grooves but, from what I could glean from any research I did, falls apart relative to both Baerwald or Lofgren with much higher distortion numbers pretty much anywhere else on the record.

But there is no simple answer. It's quite possible that if a tonearm was designed using Stevenson (or something approaching Stevenson) numbers it might sound better with Stevenson.

The beauty of Contrad's software is that you can easily create a version of each protractor on high quality photo paper, have it laminated for a couple of bucks, choose the one you want to go with, tape it to a junk record and have a very high quality customized protractor for next to nothing.

http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=659984&highlight=baerwald+distortion&r=