[john1970]

To anyone,

Can someone please explain the difference between the top and bottom woofer on the RM40s?  Also is the passive radiator surround rubber or foam?  I hope it is a rubber surround so I don't have to replace it.

I must say an excellent sounding speaker!  Vocal recordings sound as close to live as one can get in a stereo system.

Thanks,

John

[opnly bafld]

Hello John,
Brian's post about the new mid-bass driver is on page 18 of the VMPS circle.

Lin

[warnerwh]

The top and bottom woofers are both megawoofers. The one that covers the mid/upper bass has a 90% charge on the magnets so it won't cause problems.

The passive uses the latest generation foam which has been treated and should last at least 20 years.  Believe it or not foam is an excellent material for a surround and has gotten a bad rap because of it not lasting as long as rubber. The new foam will last longer than I suspect 99% of owner's need it to.

[Brian Cheney]

The top and bottom woofers of the RM40 are identical (80oz/4layer VC/woven carbon fiber cone/natural rubber surround) except for magnetization.

The top woofer is charged at 90% for a Qt of .3, and the bottom woofer is charged at 75% for a Qt of .45.  By slightly staggering their resonances there is less of a bass hump and impedance peak when both share one cabinet.  

You can do some neat tricks with the incremental magnetizer. Ours is an antique from the late 1950's.

The PR indeed is vitrified paper cone with a foam surround.  The basket (like the two active woofers) is damped with Dynamat.

[john1970]

Brian,

Thank you for the details.  I appreciate the technical details (my degree in science is showing   )

John