The AOS Studio 24 BE (S24) is a closed box MTM loudspeaker (Photo 1). The S24 is sold as a kit by Axel Oberhage Starnberg (AOS) in Germany. The original AOS design is a “bookshelf” format box. However, free-standing operation of the S24 on a stand is acoustically better than stowing it away in a bookshelf. The S24 uses high-quality driver units made by ScanSpeak.
A unique feature of the S24 is that the woofers protrude by 18 mm from the front baffle, whereas the tweeter sits flush with the baffle. Most speaker designs lack this offset, which, due to the recessed woofer cone(s), causes a lag of the sound wave(s) emitted by the woofers relative to that of the tweeter. The additional offset used in the S24 therefore avoids the typical misalignment of the different drivers and therefore allows time-coherent sound emission from the woofers and the tweeter.
I decided to modify the original AOS design a little when I built my S24. In particular, I used a full-height floor-standing enclosure for the S24, revised the crossover filters a bit, and added an active subwoofer. A detailed description of my tests, modifications, and extensions to the S24 are available as a separate PDF document.