[Heathkit] Dumb speaker question

[Wayne Harrah]

Hello all.
 
This is going to be laughably dumb.  I apologize for that.  I just
purchased an SB-301 receiver and am waiting for the arrival of a HW-101
also.  The SB-301 got here, but lacking any speaker, I plugged in an
external speaker I had laying around into the phones jack.
 
Audio was extremely nasal (thin) and high-pitched. no depth or lows at
all.  When I turned up the volume, it got distorted and not all that
loud.  Is there something I need to know about the audio outputs on
these old rigs?
 
Thank you.  Sorry for the first-grade questions.
 
Wayne, ke0ms