Good Analog EQ

ditto Rives. What about speaker placement and listening position. You can make huge differences with such adjustments. Can you describe you positioning?

Also, best to start with an optimized setting so as to minimized required corrections.

IMHO, the Aeria; 9s were designed for powerful bass, not "thick" bass. As speakers go, they are very flat. Any speaker, especially ones that go as low as the 9s, need to be positioned carefully to avoid the issue your describing.

It is never advisable to position speakers the same distance from both walls as it creates strong standing waves. Moving them out from the back wall and/or closer to the side walls, even a few inches, will help. Moving them out from the back wall will increase your soundstage depth dramatically. The more you do it the better it gets; and it WILL help your bass problem not matter what your Ariels were designed for. One ideal would be 8'4" from the back wall and 2'4" from the side walls. This puts the speakers 1/3 of the way from the back wall and 1/6 of the way from the side walls. This will be a good start at minimizing standing waves. All dimensions calculated from the center of the port, or alternatively, from the voice coil of the woofers, depending on which frequencies are the most problematic.

Your listening position is a few inches from the center of the room, also not good. Again, 8'4" from the rear wall would be one ideal if you followed the above suggestions. If not, you might try moving forward even a few inches. Moving back a few inches will put you right in a hot spot.

If you implemented the above ideals, this would also put you closer to your speakers which would give you a higher ratio of direct to reflected sound, affording you the same volume at the listening position with a lower volume setting on your preamp, which would also help. Towing the speakers in will help with perceived detail.

You could also try plugging the ports with open cell foam, or for more damping, closed cell, but those drivers are not designed for sealed boxes. Mounting the speaker on good brass or steel cones will help as well, and not only the bass. The optional feet you mentioned, of course, would be one option.

These suggestions will be more effective and do less harm, IMHO. If this is not sufficient, Rives specializes in calculating specific recommendations based on your dimensions, etc. Good luck!

correction to my last post: it should read "optimized setup".

Measurements should be made from just behind the center of the woofer cone. The Aeriels shouldn't have a dip in the midrange. It's more likely that the room nodes in the bass are eclipsing it. 15db humps in the mid bass due to room/positioning are not uncommon. And as you noted, that hump is way above where the port kicks in. Moving the speakers to 8'4" from the back wall and 2'4" from the side walls will put the speakers about 6' from your 12' listening position, which, although a little extreme, should be a very interesting change for you, as long as you toe them in to point about a foot or so behind your head. Of course experimentation is the key. Avoid 6'3" as this is 1/4 of the room length. 4'2" would be 1/6 but would still be very close to your back wall. 5' mightn't be too bad. How high is your ceiling?

3'8" from you to the axis of the speakers but 6' to each speaker. How did the bass improve? If this is too disconcerting try 5 feet from the back wall. This'll probably work very well for you if the other was too much.

Kal, perhaps I'm using the wrong words. In any case, the same frequency will be supported by both walls creating a larger bump up at that frequency. The ideal is to distribute the supported room induced frequency anomalies so none get too far out of wack. Thanks for the correction.

That's very true, but the pro audio community usually thinks nothing of putting all kinds of things in the signal path for the convenience of manipulability, and are often looking for pleasing colorations rather than maintaining ultimate transparency. IME, you can hear an additional solder joint, let alone a volume pot, active circuit, tube or transistor, coupling capacitors, resistors, etc.. Just because they have already been used in the signal path of the recording, mixing and mastering doesn't mean they wouldn't further degrade the sound. The question is whether what you gain from the device is worth the degradation to YOU. There's no question the Manley EQ is a good one. There's also no question that you could hear its presence in the signal path on a resolving system with its settings set to flat. Some may remember the EQ offered by Cello about 15 years ago, although I believe that was marketed primarily to make EQed recordings iistenable rather than to correct for the room.

Rives might be the heavy artillary you need. They do good work.