In my opinion it is simply made for the DX-394. I hadn't realized before connecting the speaker, but afterwards it was evident that what I didn't like about the DX-394 audio was the fact it was somewhat muffled. It lack clarity and sharpness and isn't all that pleasant to listen to for any length of time.
And during fading there is quite a lot of hiss evident. But through the Radio Shack speaker, the audio is beautiful. I prefer it to my Yaesu FRG100 and Icom 703 both of which I would rate highly for audio in their own right. When there is QSB on the signal, the signal deterioration is far less marked on the Radio Shack speaker, and I find I can listen for hours through this speaker, when on the DX-394 alone I would long ago have switched off. Gone is that muffled, almost processed characteristic. It has nice bass tones, but not too much so. And the higher, treble tones are much more soothing on the ear. As you can see, I can't recommend the combination of DX-394 and Radio Shack speaker highly enough. This is nicely demonstrated on this nicely demonstrated You Tube video The DX-394 also has another really cool feature: it will tune below 150khz all the way down to VLF and ELF. This means you can hear time signals, submarine communications, beacons and all sorts of other interesting utility stations.
