I've built nearly twenty pair of speakers over the years. Many single driver, back loaded horn designs including the Frugal Horn Sachiko, Saburo and numerous Nagaoka Tetsuo models. The Frugal Horn XL designed by Scott Lindgren is likely the most successful full range, back loaded horn for it's size. The huge Sachiko double mouth horn, using a Fostex 206e has a larger presentation, but bass is equally as deep with the Alpair 10p in the XL cabinet. As with most single driver speakers, imaging is spooky real and the signal is incredibly pure with no baffle step correction needed. I built this pair using Baltic Birch 18mm ply and birch veneer. Internal wire is Dueland cotton insulated copper.