Pioneer SX-1050 speaker problems


Hi,

total noob here. I recently purchased a pioneer sx-1050. I have an Audio Technica AT-LP120 and DALI Zensor 3 speakers. The receiver is in great condition and sounds fantastic. However, at higher volumes (especially if I have the bass positive) the cones on the speakers vibrate crazily. 

I have tried reconnecting the speakers. I have also tried an external pre-amp but if I turn up the bass even a little (I like heavy bass) then at higher volume the speakers have a fit. I presume I am doing something stupid. Any ideas?
M.
128x128schmada
A few options that I can think of...
If your a bass head and like to crank...
Cerwin Vega,  if you want a bit more refinement
Klipsch and if you want to stay in big boy territory
Legacy...... or add a subwoofer and cross your Dali's so that they see 100hz and above and let the sub do the bass duties.
I hope this helps, Tim
I had the same fluttering/pumping woofers in my system and no amount of placing the turntable, different platforms and shelving helped.  I ended up buying a KAB rumble filter and the problem has vanished.  I can not hear any negative effects.
Invaluable advice here. I have been looking at Pioneer Hpm-100s as a solution and this now confirms what I need to do. Stellar community here! 
Wow, this is incredible ...I m still using my SX-780, the HPM-40 speakers (sometimes switch to my JBL L40s bought in 1977) and my Dual 1257 turntable that I bought all brand new back, I think 1976, in my upstairs study. Two entire side walls are covered with LPs literally from floor to the ceiling. Those SX Pioneers are definitely keepers.