Acoustic Rearch公司AR-3音箱分频器电路图

AR-3 Crossover Schematics 2008 The Classic Speaker Pages

AR-3 Crossover Schematics

During its production cycle, AR modified the AR-3 crossover schematic veral times. This note

attempts to catalog tho changes bad on detailed information available in Tom Tyson’s files.

At 学习文言文的方法 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 rial number C1413:

The schematic shown here; dated 13 March 1959 and initialed by EMV, is the original AR-3.

T

STRAP

0.4 mH

2

R

BE

24 F6 F (dual capacitor)

GN

BK

0.06 mH

++

W16Ω

16Ω

3700

1

BK

B

+

M

4500

1

BK

B

Y

T

2

BK

2

Y

375

1

B. Serial numbers C1414 – C19467:

In 1960 the crossover was changed to rever the pha of the mid-range and tweeter with

respect to the woofer [1]. This was the only change made at this point in production.

T

STRAP

0.4 mH

2

R

2

Y2Y

BB

BKBK11

4500375

M

T

16Ω

16Ω

+

W

3700

0.06 mH

GN

BK

BK

24 F

BE

6 F (dual capacitor)

1

1

+

+

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

STRAP

0.4 mH

2

R

2

Y2Y

BB

BKBK11

4500375

M

T

16Ω

16Ω

+

W

GN

BK

BK

3700

24 F

BE

6 F (dual capacitor)

1

D. Serial numbers C70229 to end of production:

On 13 May 1970, AR ran out of the original phenolic-dome mid-range. This requ急性肠胃炎有哪些症状 ired the u 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. (The 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-F capacitor in parallel with the 24-F (to make a total of 30 F) and the addition of a 0.4-

mH (143-turn) coil across the mid-range driver. The changes are illustrated below.

T

0

.

4

m

H

STRAP

0.4 mH

2

R

2

Y

2

Y

B

BK

T

16Ω

1BK1

B

M

16Ω

3700

4500-3Mod

+

W

GN

BK

BK

6 F

24 F

BE

6 F (dual capacitor)

1

2

+

+

375

+

+

AR-3 Crossover Schematics 2008 The Classic Speaker Pages

E. Replacing the AR-3 mid-range with a rvice replacement:

After the original mid-range supplies were exhausted, the new driver described in Section D was

ud for both production and rvice replacement. So it is possible that an Internet-purchad

speaker contains a rvice replacement mid-range. Service replacement was not straightforward,

as the crossover had to be changed to that shown in Section D. Thus, speakers with rial

numbers of C19467 and lower needed to have their 51-turn coil removed before the parts for the

new rvice replacement were added. Speakers with rial numbers greater than C70228 would

not have needed the crossover modification, since the new style mid-range was installed when

originally asmbled.

F. Replacing the AR-3 high-range driver:

If an open-circuited, early high-range driver was not replaced with a new unit, then its

connections needed to be reverd to keep the correct pha relationship with the new mid-range

and woofer. By 1974 AR was supplying high range drivers with the pha reverd internally

and they were connected as the older models were, with no external reversal of the wiring. The

drivers all ud aluminum wire; aluminum solder and flux, or crimp connections are required.

G. Mid-range Magnet Structure:

At some point in the 30,xxx rial number range, AR changed the magnet structure from the

modified form of the AR-1W, to a potted type magnet. The two cross-ctional views are shown

here. The two styles are equivalent.

H. A Potentially Confusing Schematic:

In the AR Library under [original models (1954-1974)] [schematics/rvice]

[AR-3] will be found a drawing entitled: AR-3 Schematic with Notes. This is not an AR-3

schematic! It is the schematic AR ud at the factory to convert a customer’s AR-3 to an AR-3a! That

change required new mid-range and hi-range drivers, as well as all coils, and all except one of the

capacitors.

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AR-3 Crossover Schematics 2008 The Classic Speaker Pages

[1] Pha reversal was initially done manually by reversing the midrange/tweeter wiring with

respect to the woofer. At some point, AR either reverd magnet polarization or internal coil

wiring to change this pha internally. It is a daunting task to determine whether or not a

particular AR-3 is in-pha or out-of-pha. The acoustically measured effect is only slightly

noticeable and only barely audible—not to a great extent. Quite frankly, room-acoustic

artifacts can have a much greater influence on the output of the AR-3 than the simpl风娘 e dc

phasing reversal. If your AR-3 has never been opened or modified or repaired, it is almost

assured that the dc phasing is correct for that speaker, so do not worry about attempting to

change 心得体会200字 it. 镜花水月的意思 On the other hand, if a replacement driver of unknown pedigree was installed, then

all bets are off. In order to determine exactly the pha relationship, the speaker must be

electrically measured with a sine-wave oscillator and oscilloscope or with respon

measurements at the crossover frequencies, but this is quite difficult to determine accurately

without professional test equipment. In the end, its probably best not to worry about the

phasing. If the speaker sounds too bright around the midrange crossover frequency (around

1000 Hz), and it is noticeable, you may rever the l请假条 ead-in wires from the midrange driver to

the terminal strip (thus reversing the polarity of the midrange driver on the tweeter terminal

strip on the front speaker baffle board under the grill). Since nearly all AR-3s ud

aluminum wire from the tweeters, soldering the aluminum lead-in pigtails requires AlumiSol

aluminum solder to properly bond, so care must be ud when unsoldering and re-soldering

to insure a proper solder joint. An alternative technique for joining aluminum to copper by a

crimp connection is described in the AR restoration document.

08 July 2008; John O’Hanlon, Tom Tyson

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