Nice measurements. What equip do you use?

Would be interesting to turn the horn down on the one that works and see the difference. Get rid of that 1KhZ peak a bit.
Of course that will turn down the highs too, a problem Altec addressed in later years with the A7x and model 19's dual shelved X-over.
But getting that peak down might make the sucky recordings more tolerable.

I've had several sets of A7's and have to say they do sound better flipped with the horn outside the box. You can build a removable top that you furniture finish to match sometime in the future. of course the wife won't like the horn look either.......ha!

You have a nice room for them!

Dire Straights "On Every Street" is another nicely recorded album to try.

Enjoy!

Ron