The audio output if fed into the LM386 IC which is the audio amplifier. I am using an earphone from an old transistor radio but this circuit would have no problem driving a small speaker with plenty of output. It is a simple build with 30 or so components that runs off a 9 volt battery and includes a case. Assembly time is rather quick, an hour or so of soldering and now on to on the alignment stage with a few broadcast stations and digital signals received so far. I really need to hook up a speaker because with the very old earphones might be creating extra hissing pitch that is unpleasant to listen to.
Also will be hooking up a frequency counter as a helper and try to get 14.060 set up. The HR20 is a fun easy kit to mess around with and includes a instruction booklet with a few modification ideas.
Will keep you posted if I decided to change things around with this receiver.