Acoustic research ar 3 service manual

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Page 1

Restoring the AR-3a © 2007 The Classic Speaker Pages

Restoring the AR-3a

Roy Champagne, Ken Kanmr, Minh Luong, John O'Hanlon (Ed. ), Bret Thiel, and Tom Tyson
6 December 2007

Welcome fellow AR traveler! If you are reading this, you are probably considering repairing or
restoring an old AR-3a pair. For some, this restoration process is an afternoon of effort and a few
dollars in suppliesijust to get some reasonable sounds going. For others, it is a consuming quest
for perfect authenticity. Either way, it's a lot of fun and a good learning experience. Only you can
decide how much time and money you want to devote, and the job also depends on the physical
and electrical condition of your speakers. As a first step, take a look at the flow-chart included
here to get an idea of the task at hand. Many of us are very passionate about the 3a and consider
it a landmark product in the history of loudspeaker development. A properly restored pair can
sonically rival the best modern speakers and will reward the investment of effort put into them.
However, even a basically repaired pair will be capable of providing much listening pleasure for
years to come. [KK]

Table of Contents

1 What is it? 2 3.9 Replace the Capacitors? Options 16
2 Identifying and Checking Components 2 3.10 Early Woofer Inductor Replacement 17
2.1 Useful Tools 2 3.11 Grilles and Badges 17
2.2 Getting Started 3 4 Re-assembly 19
2.3 Removing the Grille 4 4.1 Gasket Materials 19
2.4 Check for Visible Damage 4 4.2 Installing Mid- and Hi-range Drivers 20
2.5 Low-Level Listening 5 4.3 Stuffing the Cabinet 21
2.6 Woofer Diagnosis: Low Level Audio 5 4.4 Installing the Woofer 21
2.7 Mid-Range Diagnosis: Low Level Audio 6 4.5 Testing for Acoustic Leaks 22
2.8 Hi-Range Diagnosis: Low Level Audio 6 4.6 Remounting Grilles and Badges 22
2.9 Play it Again, Sam 6 4.7 Testing Your Speakers 22
2.10 All Systems -Go" 7 4.8 Finished! 23
3 How to Fix It 7 Acknowledgement 23
3.1 Removing Woofer 8 Appendix: Driver Identification 23
3.2 Removing Mid-range and Hi-range 8 A.1 Woofers 23
3.3 Repair or Replace the Woofer? 8 A.2 Mid-range Drivers 24
3.4 Removing the Stuffing 9 A3 Hi-Range Drivers 25
3.5 What-s Inside? 9 A.4 Driver Images 26
3.6 Replace the Mid-range driver? 11 Woofer 27
3.7 Replace the Hi-range driver? 11 Mid-Range 29
3.8 Replace or Restore Potentiometers 13 Hi-Range 31

Page 2

Restoring the AR-3a © 2007 The Classic Speaker Pages

1. What is it?

The AR-3a is a three-way acoustic suspension loudspeaker manufactured from 196771975. Its
specifications are: External cabinet size: 14><25> kg.). Drivers: 12- woofer, 1-1/2- mid-range, 3/4- hi-range. Average woofer free-air resonance:
18721 Hz. Average resonance with cabinet stuffed: 42 Hz. Crossover frequencies: Mid-range,
575 Hz; Hi-range, 5000 Hz. Internal volume: 1.48 ft3 (41.8 liters). Impedance: 4 S2. Independent
mid-range and hi-range driver level controls.

Each of us has their own reason to restore and enjoy the AR-3a. Here-s one person-s view:
-In those years the AR-3a was considered to be the best made in the US. They had been
crowned the king of speakers in South East Asia, where they were well known in Vietnam, Hong
Kong, and Taiwan. In 1972 I first encountered the AR-3a in Vietnam in my Uncle-s house and in
my Father's best friend-s music room. I loved them for many reasons. They were expensive and
owning a pair was like owning a Corvette; it was a symbol of high class and good taste. They
were built like a tank and meant to last forever, which we have proven to be true 40 years later.
The sound quality was superb and for the price, there was no other speaker that could come
close. The signature solid deep bass made it one of a kind. The uncolored mid-range and the
ability to deliver music and vocals as close to the real thing made the AR-3a as one of my all
time favorite speakers. They are small enough to stuff into an area where other speakers may
have problems. The wide dispersion drivers set them free from sweet spot listening. Regardless
of their simple and primitive crossover and drivers, they still remain very accurate compared to
other speakers that were designed with computer aided programs. After experiencing the AR-3a, I
tumed into a real -AR fanatic.- I am still trying to break my habit.- [ML]

2. Identifying and Checking Components

Figure 2.1 identifies the major components of an AR-3a. Early models used -front-wired- or
-hard-wired- mid- and hi-range drivers, so named because their lead wires were soldered to a
terminal strip on the baffle board. The late model used push-on connectors that mated with back
mounted male tabs. Amplifier connections for full range operation are made to posts 1(7) and
2(+) on the rear, provided that a jumper wire is connected between posts 2 and T. The jumper
wire is removed for use as a woofer only. The cabinet was acoustically sealed with gaskets under
each of the three drivers. Air leaking around level control shafts and amplifier terminals provides
a small amount of air permeation needed to prevent the cabinet from becoming too tightly sealed.

2.1 Useful Tools
Some tools are necessary; others are useful. Here are some recommended items:

Soldering iron; 30750 W. Volt-Ohm meter (very helpful)

Solder; 0.032- or 0.065-in. diameter rosin core Capacitance-inductance meter (optional)
Solder wick (finely braided copper) Small, wide-blade putty knife

Long nosed pliers Rubber gloves

Side cutting pliers Dust mask

Phillips screwdriver; #3 (or #2) Plastic or paper bags to hold stuffing
Flat-blade screwdrivers; 4-in. and 2-in. Padding to protect the cabinet-s finish
l.5-V AA cell, battery holder, and leads Digital camera

Small magnet (helpful) 3/4-in. adjustable end wrench