We tried several BR ports from 3/4 to 2 1/2" deep. All sounded boomy. Sealed was better but then The Speakerman reached into a corner somewhere and came up with these foam discs and put them in the ports. Much better.

Who knows where Ron gets this stuff. I alternate between beleiving his house is a 'gate' to another dimension populated by speaker parts or he finds things nobody lost.

The drivers really mesh nicely with no attenuation on the tweeter. I'd say efficiencey is around 93.