The Talking Machine Forum — For All Antique Phonographs & Recordings

It is currently Fri Oct 23, 2020 9:07 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 91 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 10  Next
Author Message
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 6:07 am 
Offline
Victor V
Joined: Wed Jan 07, 2009 4:21 pm
Posts: 2834
Location: Biggenden, Queensland, Australia
I think you're asking a question that's impossible to answer.
Even if all tonearms were the same design but of different lengths, then the longer the arm was, the further back from the turntable it would need to be mounted if the needle was to align with the centre spindle.
Whether the tonearm was mounted directly behind the turntable (as they are on most uprights) or to the left or right of that position (as on many portables) would also effect tracking. Tracking would be effected even if all tonearms were exactly the same design and length, depending on the position they were mounted.
Is it a one piece, gooseneck or swan neck tonearm?
There's just too many variables that come into play.

I think the best you could hope for is to work out tracking error according to a particular tonearm type, position and length, and do what you can to minimise it.


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 7:02 am 
Offline
Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
gramophoneshane wrote:
Whether the tonearm was mounted directly behind the turntable (as they are on most uprights) or to the left or right of that position (as on many portables) would also effect tracking.


Shane, I don't think mounting to left or right or center effects tracking error. Logically mounting to the left or right is simply a matter of viewpoint as it relates to the position of the viewer. But the viewer can stand anywhere relative to the machine and certainly the position of the viewer does not effect tracking error. For example, if I stand in front of the machine and the tonearm is directly behind the turntable all I have to do is step to my left and now the tonearm mounting position is to the right of the turntable. My taking a step to the left does not effect tracking error.


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 8:17 am 
Offline
Victor V
Joined: Wed Jan 07, 2009 4:21 pm
Posts: 2834
Location: Biggenden, Queensland, Australia
Lol, well no, side stepping obviously doesn't change anything except your view.
The arch of a particular tonearm doesn't change either, and provided the needle is always falling on the centre spindle, the position of the tonearm base makes no difference either.
But mounting the tonearm with disregard to the needle falling onto the spindle will alter the angle the soundbox/needle rides the groove.

Most original machines were designed so the needle aligns with the centre spindle, but an awful lot do not.
The only real choice to improve an original machines tracking is an adaptor of some sort between the tonearm and sound box.

If however you were building a Frankenphone with existing parts, some tonearm designs may actually provide better tracking by mounting them so the needle falls slightly short or past the centre spindle to achieve the best possible tracking without an adaptor.
Lots of variables that really needs to be accessed according to tonearm design, position and length.


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 8:47 am 
Offline
Victor IV
User avatar
Keep'em well oiled
Joined: Mon Dec 18, 2017 2:51 am
Posts: 1015
Location: Madrid, Spain
Let's state one thing clear, that seems to be floating around as an axiom. The needle falling on the spindle is part of the solution for minimal tracking error only in one particular case of tonearm length against distance to spindle values. All other of the infinite solutions depending on these variables don't require the needle falling on the spindle. Usually the best results are obtained with tonearm lengths slightly larger than the spindle distance, so there's an overlap, together with an angular deviation of the diaphragm plane outwards the tonearm theoretical line to the needle point. Read the articles on the matter that someone else has posted in this and other related threads. And definitely the Percy Wilson book of 1929 Modern gramophones and electrical reproducers, with an entire chapter devoted to this geometric problem and how to solve it. If you do a search on the forum, i believe someone posted scans of these pages...
And I support the assertion that the best is to conform with what you have on your machine, and try to improve it. Slight changes can be done with great results, adjusting the needle length, the soundbox vertical angle (which can be varied between, let's say, 55 and 70 degrees), and the soundbox outwards correction angle by means of an adaptor inserted on the neck connection. The best results are obtained with the longer tonearms. With the big tonearms of the EMGs and Experts, or the big hmv reentrant machines 193/202, you can get a very small tracking error. Shorter arms like the hmv 102 portable are almost impossible, you always get a big error at one end. It's designed to minimize the error at the inner grooves, the most packed and the worst place.
Inigo


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 9:02 am 
Offline
Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
gramophoneshane wrote:
provided the needle is always falling on the centre spindle, the position of the tonearm base makes no difference either.


Exactly my point. It doesn't matter what position the tonearm pivot is at in the 360 degree circle around the turntable provided the needle is designed to fall in the same position relative to the spindle. So it doesn't matter if the tonearm is pivoted from the left, right or center, all other aspects being equal. However the length of the tonearm does matter. A 12ft tonearm will have almost no tracking error, but it won't fit in the room, my room, its a small room. Likewise a 6 inch tonearm will definitely have a greater degree of inherent tracking error than a 9 inch, all other things being equal because the arch described by the 6 inch tone arm is tighter than that described by the 9 inch.


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 9:03 am 
Offline
Victor II
Joined: Sat Aug 11, 2018 12:14 pm
Posts: 230
Location: Plainfield, NJ
Just wondering...as I wrote in another context, the needle both on my Victor 8-12 and on my Credenza with the turntable offset to the right falls about ½” short of the center spindle. Is it likely that Victor didn’t care much about this after modifying the design from the original Credenza where the needle does line up with the spindle?

Bill


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 9:12 am 
Offline
Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
Inigo wrote:
The best results are obtained with the longer tonearms. With the big tonearms of the EMGs and Experts, or the big hmv reentrant machines 193/202, you can get a very small tracking error. Shorter arms like the hmv 102 portable are almost impossible, you always get a big error at one end.


This is what I have been trying to say. I plan on building a machine from scratch using available parts and manufactured parts, not modify an existing machine. This gives me some degree of flexibility. Hence my original question. What tonearm length is optimum and practical for reducing tracking error as much as possible?


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 9:33 am 
Offline
Victor IV
User avatar
F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
Posts: 1049
Location: Italy
I will repeat once more - and for the very last time - that the length of the tonearm is less important than its position relative to the spindle and the offset angle / linear offset. Moreover, there is not "one solution best for all" to this problem, but infinite solutions that depend on what you consider being "best" to your case: minimize tracking error at the inner grooves, keep it low and approximately constant over the whole arch, zero it in one specific point, zero it in two points, and so on and so on and so on. None of these is "best" in all cases and all records, but have pros and cons.

You are asking to other people a quick solution to a problem that involves geometry, algebra, trigonometry and a specific language about which you have no idea about. Open a book, study, master the subject and then come back here for advice if still needed.


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 9:39 am 
Offline
Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
Marco Gilardetti wrote:
the length of the tonearm is less important than its position relative to the spindle and the offset angle / linear offset.


Okay Marco, I'l take your advice and use a 3 inch tonearm and adjust all other parameters accordingly since as you say, tonearm length is less important.


Top
 Profile  
 
 Post subject: Re: Ideal tonearm length ?
PostPosted: Wed Feb 12, 2020 2:03 pm 
Offline
Victor II
User avatar
Joined: Tue Sep 21, 2010 5:52 am
Posts: 354
Location: St. Albans, UK
Marco said tonearm length was less important and not of no importance. Don't take offence :) it can be a complicated subject.

After the introduction of electrically recorded records around 1925, most manufacturers had to improve tracking alignment to reproduce the new frequencies. New soundboxes were introduced but it wasn't practical to make the tonearms any longer to reduce the tracking error so they introduced the offset angle, as mentioned previously, this is a tilt of the soundbox to the length of the tonearm, The tilt angle will vary depending on tonearm length and position.

Some pre 1925 tonearms can have a length in excess of 10 inches but provide a very poor tracking error because there is no offset angle. The link below provided by 'emgcr' helps to understand the subject and offset angles and overlaps relative to tonearm length.

viewtopic.php?f=11&t=15253&hilit=questions+regarding+Expert+Senior+motor


Last edited by jamiegramo on Thu Feb 13, 2020 6:35 am, edited 3 times in total.

Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 91 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 10  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Content © 2009-2020 by The Talking Machine Forum and the respective posters.
Americanized by Maël Soucaze.