New Cain & Cain IM Ben Fostex/double horn - help

The Cardas speaker placement has always worked very well for me, but it recommends that the speakers are further from the rear wall than from the side walls. There's a simple formula for calculating the distances at www.cardas.com under one of the sub-headings.

The only drawback I've found is that the speakers end up quite far into the room, which can cause some friction with SWMBO.

I had a similar problem with my Lowther drivers in my Voigt Pipe cabinets.
The fix was to use a set of SP-004 Sistrum Platforms under them. Like magic. Boxy sound gone, smear eliminated. I've posted this numerous times in the past, and also emailed several people about it who experienced similar problems. It is even written into the Voigt Pipe construction plans that appear on the Lowther America website. I know the Double Bens are not Voigt Pipes, but I know about this problem.

Yes, I'm the Sistrum internet sales rep, and yes it really did work as I said.

As someone said earlier, try moving the speakers a little. It's cheap and you can do it immediately. I've read the worst place for a speaker is when it's placed the same distance from the side & backwall. I know you wrote 3 - 3.5 feet on one of your measurements, but sometimes even a few inches can matter, so try increasing the ratio. If you ever want to try another cable, I just got some Cardas SE-15 that Terry recommended for up to 12 feet. Great synergy with SET/single driver combos. Good luck.

You are hearing cabinet resonances.Thats why you dont hear farther back.All back horns produce these to some extent.You could cork line the horn.But as others have said ask TC .

It's a combination of your speaker location and your listening position in the BIG problem called, your ROOM. As you mentioned, when you are against the wall (at a boundry) the problem goes away. So if possible, consider re-arranging your room so your listening position is AT the rear wall.
If rearrangement is possible, also consider placing the speakers across the 24' wall. If that is doable, start with bringing each speaker 6' from the side wall to the center of the driver. That will give you 12' between the speakers.
Locate them mid-way into the room and your listening location against the rear wall. Be sure your ears are ABOVE the back of the chair/sofa you are using.
Start there and move your head forward and backward and notice the difference in the soundstage and imaging. When you find the point that sounds best, place your seat so that you are AT that point when you sit naturally.
Also, play with the toe-in on the speakers. A $20 laser level is good for proper alignment there.
Do this with the Dakron stuffing removed from the Cains.
You'll know it when you find the magic spot!
There's more you can do with cheap tweaks to the room, but this will be a good start to "work with what you've got".
Good luck and let's hear back from you with the results?