I recently put together a Frugel-Horn kit I purchased from Planet10 Hi-fi in Victoria, British Columbia, quite a while ago. The four-inch drivers are from Mark Audio, they're Alpair 7 generation 3. I've since sanded the cabinets and will be applying red-oak veneer.
It's surprising the bass that comes from a 4" driver in this speaker configuration!
It's surprising the bass that comes from a 4" driver in this speaker configuration!