ProAc must have received alot of complaints about the bass in the D25. This is my biggest problem with the speaker. The bass tends to boom and placement can be very tricky. Tyler probably decided to rework the D25 utilizing the cabinet structure of the D38 (side porting) to solve this problem. The D28 is now on my short list to audition. If anything like the D38, no doubt it will last a very long time. Just my 2cents.
