Sonus faber Cremona Auditor and Jeff Rowland??

>I placed my auditor more than 3.5 ft away from the wall and 4ft from the side wall.

Conventional wisdom seems to be that these two distances should not be as similar as you have them (3.5 and 4 feet). Try moving the speakers around.

Dear Brain74: About the best placement of your Auditor my advise is that you ask directly to Sumiko people, they can help you.

Now, you feel that have a bass booming sound, other than room placement, please analyse as follows: the Auditor is a medium efficiency speaker ( 88db ), it has a 4 Ohm nominal impedance ( low one ) that tell us that maybe it go down to near 2 Ohms in some frecuencies ( maybe in the bass ones ), its usuable bass frecuency is around 50 Hz.

All these specs tell us that the Auditors need a high current amplifier with very low output impedance that can put high current below 4 Ohms: your Concentra 1 can't do it, your Auditors needs a better match amplifier, maybe the Concentra 2 or other Rowland model. Again, ask to the Sumiko people: they have to help you.
Btw, don't wait to much in the low bass: 50 Hz are " only " 50 Hz, nothing more.

Regards and enjoy the music.
Raul.

I second Raul, above. I have enjoyed auditioning Mahler & blues on SF (Amati, Cremona & Strad) -- using hi-current design amps.
Unfortunately, I only listened to these speakers paired with European amps (i.e. expensive), and therefore can only recommend YBA Passion, Goldmund (the mid-level stereo, can't remember the number), and Symphonic Line RG4. The latter made the nicest music to my taste (I auditioned with Mahler & blues, cd source).
Again, this isn;t to say the Rowland is bad in any way...

I have been using the SF Auditors with the JRDG new Concerto int. amp. with great results. Placement is tricky however. I find even after months of use I still cannot find the optimal placement.

i have heard the Pass Labs X250.5 with great results too. No Bass Boom. just music!