Simple question, why not horn loaded speakers which seem to be a perfect match for low power tube amps?
As speakers they do tend be bigger size wise but small, low mass, fast, and efficient drivers easily match the attributes of a SET amp. The SET amp was developed to drive horn loaded speakers it wasn’t until much later that speaker design moved to a much smaller box adding much heavier drivers requiring much more power.
There are some high efficiency single driver open baffles but they usually require a sub.
As speakers they do tend be bigger size wise but small, low mass, fast, and efficient drivers easily match the attributes of a SET amp. The SET amp was developed to drive horn loaded speakers it wasn’t until much later that speaker design moved to a much smaller box adding much heavier drivers requiring much more power.
There are some high efficiency single driver open baffles but they usually require a sub.