Adding mass to a tonearm


I would like someone to explain to me why adding headshell weights doesn't really alter the mass of the tonearm that much when figuring cart vs tonearm compliance. I have a Denon DL-103r and I keep reading that's it's for high mass tonearms. I also hear that adding headshell weights doesn't really alter the mass. What gives?

I want to try a DIY on my Pioneer PL-530 turntable tonearm where I mask off the arm such that only the chrome arm on the headshell side is visible and spray it with Plastidip. This would seem to add mass and resonance control. If it doesn't work the I can just peel it off.  
last_lemming
If you add a headshell weight to the tonearm it will change the resonance frequency of the tonearm and cartridge.
Adding weights to the headshell DOES increase the effective mass of the arm. Not just because of the weight itself, but also because to then balance the arm, the counterweight on the back end will need to be moved further from the arm's pivot, which also increases the arms effective moving mass.
it doesn't really alter the mass of the tonearm that much because of the pivot

Agree with bdp 24. Probably contra-intuitive but moving the

counterweight nearer to the pivot decreses the arm mass.

Adding weight to the headshell on the other side ''obviously''

increases the arm mass.