[rcag_ils]

So what are the difference between a straight, S-shape, and J-shape tonearm, when their distance from pivot to headshell are the same (9 inches)?

[Wayner]

I believe there are two main reasons for the "S" or "J" shaped tone arms. One is to help reduce resonances of the arm, the other is for looks. With the sweeping curve of the arm, the head usually was in the proper offset angle, giving an appearance of a natural "correctness" of the whole mechanism, if you will.

To a novice or newbee, the straight tone arm with the "crooked" cartridge just doesn't look right and invites foolery.

Wayner 

[rcag_ils]

My armboard cut for straight tonearms will not accept S-shape tonearms even if they are in the same family, that really sucks. Now I have to build a new armboard.

[BobM]

There should be absolutely no difference between a straight vs an S shaped tonearm mounting if they are the same effective length. As long as you can put it in the right spot accommodating the spindle distance and overhang the shape is irrelevant., unless it is bumping into something that it shouldn't be bumping into.

[Wayner]

There should be absolutely no difference between a straight vs an S shaped tonearm mounting if they are the same effective length. As long as you can put it in the right spot accommodating the spindle distance and overhang the shape is irrelevant., unless it is bumping into something that it shouldn't be bumping into.

Agreed, but he may have a separate arm rest that may not now fit so nice with a straight arm. The spindle center to tonearm pivot center are identical, as Bob has stated.

Wayner