Shahinian Obelisk vs VandersteenTreo

Jazz
 Please make sure if you switch amps in the system that you use Vandertones and nail the X 5s hi pass set up proper dip switches to confirmed its exact input impedance with a voltmeter as instructed in the Vandy owners manual.
 It is essential to not just take for granted the amps input impedance spec as it's a good place to start most likely off and it could push the x over to 80 Hz which doesn't allow the Lightning fast Quatro driver to be at its best.
  Best JohnnyR
 

JohnnyR,
Thanks.  Wil work on that. 

Well, after a while I finally decided to go for those Quatros and did so.
Got them a week ago and only now got home to update the battery and tune the HP filters and get a dedicated listen.
Unfortunately I discovered that midwoofer on one of the speakers produces distorted sound (especially audible on piano). I did all the fiddling with changing the wires, amps, sources, powering the speaker off, etc, but the middle speaker (right below the tweeter) sounds distorted no matter what I do. The other speaker sounds better.
The seller tells me that all was good with the speakers when he was listening to them last. Also, a week passed since I received them...
So. Has anyone had experience of this sort? What can be wrong with them?

Nuts!
Sorry to hear about your troubles. 
How were they shipped? In their boxes? 
I would call either Johnny R(or PM him), or Mr. V.- he calls back the next day. I believe the Quatro is designed so that you can remove and replace the affected driver with not too much problem- should it come to that.
Bob

One thing to be aware of, Vandersteen matches their drivers within the speaker pair.  One thing to check.  Is that driver tightly screwed into the front baffle?