Has anyone heard or built an Axel Ridtahler (Ridtahler dipole) sub woofer?

Hmmmm, W, and H are both used by GR.  They are good from 20-250hz + or - 3 db.  I use them at around 60 and below, if at all.

Good yes, the best no. WHY. Well come to find out the servo amp works because of a program that written by "whoever". If whoever, wrote the program could predict all the overshoot cone issues it would be fine, BUT they can't. The system is faster than accelerometer, servo systems, but nowhere near as accurate. 

The older accelerometer, Bass Bins were the BOMB, close to 3 times the price too.. You get what you pay for.. OB is tough, then ADD servo...
Sure looks good though...

Regards

@oldhvymec - are you saying that the measurements the amp module are fed coming back from the subs are inaccurate?

<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>

I'm saying you need to be aware of how the system works AND work with it. Depending on the size of the room it can take a few 12" drivers to really impact a room. I say impact because of the way they load the room and also how the room is vented..  IB rooms vs OB with OB subs. Sometimes it's better to mix more than one type of bass unit. Depending on the music or the effect you want.. HT for an example.

I use both, Band pass bass columns and servo controlled subs. 60hz <

The Band pass cabinets are direct coupled to the amp. No XO in the way.. Great cone control. That is a great option for ME..

Ripole are kinda'  strange the way they load a room too.

I saw 3 on either side of the seated position in a warehouse environment.. WOW.. all 12" I think. All Mac gear too.

A GREAT accelerometer and amp system is the best.. BUT the cost.

 With today's DSP, and or Active crossovers with all the goodies for bass management and BIG class D amps.  I say have fun... I sure am..:-)

Regards