Acoustic Research AR-3 Schematic
AR-3 Crossover Schematics 2008 The Classic Speaker Pages
AR-3 Crossover Schematics
During its production cycle, AR modified the AR-3 crossover schematic several times. This note
attempts to catalog those changes based on detailed information available in Tom Tyson’s files.
At some point a complete description of the AR-3 will be written [TT]; at that time this should
become an appendix within that document.
A. Initial production through serial number C1413:
The schematic shown here; dated 13 March 1959 and initialed by EMV, is the original AR-3.
BE
T
T
BE
6 µF (dual capacitor)
6 µF (dual capacitor)
BK
BK
1
1
BK
BK
16 Ω
4500
4500
16 Ω
B
B
2
2
Y
Y
+
+
T
TT
375
375
2
2
1
1
STRAP
STRAP
0.4 mH
0.4 mH
R
R
BK
BK
+
+
W
WW
3700
3700
24 µF
24 µF
0.06 mH
0.06 mH
16 Ω
16 Ω
GN
GN
1
1
BK
BK
+
+
M
B
B
2
2
Y
Y
MM
B. Serial numbers C1414 – C19467:
In 1960 the crossover was changed to reverse the phase of the mid-range and tweeter with
respect to the woofer [1]. This was the only change made at this point in production.
T
T
4500 375
4500 375
M
MM
+
+
16 Ω
16 Ω
1
1
2
2
Y
Y
B
B
BK
BK
T
TT
+
+
STRAP
STRAP
0.4 mH
0.4 mH
16 Ω
16 Ω
2
2
1
1
B
B
BK
BK
Y
Y
2
2
R
R
+
+
W
WW
BK
BK
1
1
3700
3700
0.06 mH
0.06 mH
24 µF
24 µF
GN
GN
1
BE
BE
BK
BK
6 µF (dual capacitor)
6 µF (dual capacitor)
AR-3 Crossover Schematics 2008 The Classic Speaker Pages
C. Serial numbers C19468 – C70228:
The crossover was modified on 25 Aug. 1965 by removing the 0.06-mH (51-turn) coil in the
mid-range crossover.
T
T
4500 375
4500 375
M
MM
+
+
+
+
6 µF (dual capacitor)
6 µF (dual capacitor)
16 Ω
16 Ω
BK
BK
BK
BK
2
2
2
2
1
1
Y
Y
Y
Y
B
B
BK
BK
T
TT
+
+
+
+
2
2
1
1
STRAP
STRAP
STRAP
STRAP
0.4 mH
0.4 mH
R
R
BK
BK
+
+
+
+
W
W
WW
WW
3700
3700
3700
3700
16 Ω
16 Ω
2
2
1
1
GN
GN
24 µF
24 µF
B
B
BK
BK
Y
Y
BE
BE
BE
BE
D. Serial numbers C70229 to end of production:
On 13 May 1970, AR ran out of the original phenolic-dome mid-range. This required the use of a
version of the AR-3a mid-range identified by part number 4500-3MOD and later identified as
part number 200010-AR-3 or 200019-3. (These are Fig’s. A.9 and A.10, respectively, in
Restoring the AR-3a.) This required a crossover change, as the AR-3 and AR-3a did not have the
same woofer–mid-range crossover frequency. This crossover change consisted of the addition of
a 6-µF capacitor in parallel with the 24-µF (to make a total of 30 µF) and the addition of a 0.4mH (143-turn) coil across the mid-range driver. These changes are illustrated below.
T
T
Y
2
2
1
1
STRAP
STRAP
0.4 mH
0.4 mH
BK
BK
0.4 mH
0.4 mH
Y
16 Ω
M
MM
+
+
4500-3Mod
4500-3Mod
BK
BK
6 µF (dual capacitor)
6 µF (dual capacitor)
16 Ω
1
1
2
2
B
1
1
GN
GN
24 µF
24 µF
B
BK
BK
BE
BE
16 Ω
16 Ω
3700
3700
R
R
+
+
W
WW
6 µF
6 µF
Y
Y
2
2
B
B
BK
BK
T
TT
+
+
375
375
2
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