Ashly Electronic Amplifier none - Manual (Page 27)

panel control tunes the cutoff frequency of both filters simultaneously. This
type of crossover is illustrated in figure 27.
dS
♦ 6 - -
frequency‘tuned
with single front'
panel control.
■20K
Frequency (Hz)
*«i t
Figure 27.
A typical Butterworth-response 2-way
electronic crossover, made by
combining a low-pass and high-pass
filter. Note that the crossover
frequency is at the "3dB-down" point
of each filter. This approach to
crossover design works fairly well,
but the'response shape of each filter
is fixed, and therefore there can be
no control over the summed response
of
the network at the crossover
frequency. The summed response will
.show,a +3dB "bump" at the crossover
frequency.
, Another popular approach.uses, the same two overlapped filters just shown, but
gives the operator independent, control of. each filter's cutoff frequency, ie.,
.two front-panel,-frequency adjustments ..for each .crossover point. This provides
an, opportunity to either, overlap ..the two pas,s, bands or pull them apart. The
result may not be quite what-you had in mind, as illustrated in figure 28.
dB
♦6- •
t4
+2
0
-2
-4
- 6 ‘
-8
-to
- 1 2
-M
-Ci
50
;r. ^
dB
■ li . •
' »4*
» 2
0
-2
-4
'^8
1 -^0
•
12
• -14
Mfs-
IK >0 500
. V * r “■ )S J?. ^ I'
5K 10K 20K
i- Ffeqwcn
iU\ i i':;;. *
Figure' 28.
5K 10K 20K
Frequcn
(b)
V 0 ^
Here,' the i bw-pass and'high-pass"' ' fh e two filters of (a), when
; fil ters, are shown, ovej;lapping by ..two, j electronical ly summed, will combine
octavq^, .in, each‘,dTr^^^^ the ' to giye. you a very uneven response
crossover'point'.' Tou'niight'logically ' curve with two peaks near the
expect a nice even boost in summed individual cutoff frequencies, and a
response throughout this overlap dip in the crossover region,
regipp., bu.t , .that's no,t...what. you'.l?.
actuai ly ge^^tV.
Athfy'electronic crossovers, uni ike the two'examples just given, do not use
25