Audio Engineering

Loudspeaker Enclosures 727

20

2WPXORZ1.CIR Temperature  27

10

Ohms

5

(^220100) 1 K
v(1) Frequency (Hz)
10 K 20 K
Impedance of 2 way passive crossover
loading all 8 ohm resistive
XOF
Figure 24.11 : If speakers were simply resistors, the load on the amplifi er might appear as
here, with the apparent 11-ohm load simply halving to 5.5 ohms at the one point where
the two drivers are both drawing substantial current, the crossover point. Note that the
crossover dip may as well be a resonance and, as such, adds to the amplifi er’s load stress.
loudspeaker in a particular way. The combined behavior or “ chemistry ” is complex and
can be unpredictable and frustratingly unrelated to the type or class of amplifi er.
Here is just one reason why the ideal high-performance power amplifi er/speaker
combination can be determinedonly by trying them together and why quite disparate
amplifi er designs and topologies may shine equally through a particular speaker.
Knowledgeable “ high-end ” loudspeaker designers and manufacturing companies employ
a well-chosen group of different power amplifi ers. One or two will be the best sounding
“ references ” ; some will be widely used models and not particularly good performers;
others will be niche models, discovered accidentally over the years, that expose
loudspeaker problems.