Acoustic research ar 3 schematic

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acoustic research ar 3 schematic

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Page 1

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 Tysons 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.



6 uF (dual capacitor)

I 0.4 mH 0.06 mH


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.



l 0.4 mH

BK 3700

Page 2

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 (Sl-turn) coil in the
mid-range crossover.



I 0.4 mH


BK 3700 6 HF (dual capacitor)


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 Figs. A9 and A. 10, respectively, in
Restoring the AR-Sa.) This required a crossover change, as the AR-3 and AR-3a did not have the
same wooferimid-range crossover frequency. This crossover change consisted of the addition of
a 6-uF capacitor in parallel with the 24-pF (to make a total of 30 HF) and the addition of a 0.4-
mH (l43-turn) coil across the mid-range driver. These changes are illustrated below.


I a
I 0.4 mH BK +
2 3700 375

J. GN :J_ J_. BK

BK 6 uF 24 uFE l I E6 uF (dual capacitor)
1 C L___ ___'