A pair of speakers can look perfect in a listing and still have a dead tweeter, a crackly level control or one woofer from a different decade. Most of what goes wrong with vintage speakers is easy to find once you know where to look, and a lot of it shows up in the photos if you ask for the right ones. Here's how to check a pair, from the listing to the first evening at home.
Start with every driver
A three-way speaker like the AR-3a or the JBL L100A has a woofer, a midrange and a tweeter in each box, so a pair has six drivers that all need to play. A photo can't show you that. The best a remote listing can offer is a short video with sound, shot with the phone close to each driver in turn, so ask for one.
When the pair arrives, play music or pink noise at low volume and put your ear close to each tweeter, midrange and woofer in turn. If one speaker sounds duller than the other, swap the left and right cables at the amp. A fault that moves with the cable is in your amp or wiring. A fault that stays with the speaker is in the speaker.
No treble, or one side clearly duller than the other, usually points to a tired or dead tweeter. Scratchy distortion on low notes points to a voice coil rubbing in its gap. The Restoring the AR-3a guide on Classic Speaker Pages calls open tweeter voice coils a common problem, most often caused by very high volume or a small amp driven into clipping.
If you own a multimeter, measure the DC resistance at each driver's terminals with the driver disconnected from the crossover. This reading isn't the rated impedance. The industry standard says an 8-ohm driver should read at least 6.4 ohms, though plenty of 8-ohm drivers read about 5.5. No reading at all means a broken coil or lead. The two speakers should read about the same, driver for driver. The AR-3a guide uses this exact check to spot swapped domes, because the AR-5's 8-ohm domes look identical to the AR-3a's 4-ohm ones.
Crossovers and level controls
The crossover inside the box splits the signal between the drivers, and its capacitors are the part that ages. Electrolytic capacitors drift in value with age and heat, and Rod Elliott of Elliott Sound Products calls bipolar electrolytics simply unsuitable for passive crossovers. Crites Speakers, which sells Klipsch parts, gives a blunt rule of thumb. Caps over about 20 years old are due for replacement, and every speaker in this store is well past that. A recap isn't a red flag. Ask whether it's been done, who did it and whether they kept the original values. Inside photos showing new yellow, blue or film caps mean someone has already been in there.
Level controls are the other weak spot. Many vintage speakers have knobs or switches to trim the midrange and tweeter, and as a potentiometer ages, the wiper can lose contact with its track, which you hear as crackling. The AR-3a is the textbook case. Its continuously variable wire-wound pots have silver plating that wears through, and the copper underneath corrodes. The restoration guide lists crackling or intermittent sound while you turn a control as a common midrange and tweeter problem. Worn pots can be cleaned, swapped for refurbished originals or new 16-ohm pots, or replaced with L-pads.
Turn each control slowly through its full range while music plays and listen for crackle, dropouts or dead spots. Most owners start by working a scratchy control back and forth many times, often with a contact cleaner such as DeoxIT, which its maker CAIG says won't harm carbon pots. Switches need the same treatment. The AR-11 has two three-position toggles on its rear terminal plate, and the original Advent Loudspeaker has a three-position tweeter switch on the back. On a JBL 4311, the Presence and Brilliance knobs sit along the bottom of the front baffle.
Grilles
Cloth grilles tear and stretch, and foam grilles age the way any polyurethane foam does. The L100's grille is painted, sculpted foam, so ask whether it's still soft and whether it sheds at the edges. The AR-3a's grille is Irish linen on a tempered Masonite frame, and the Advent's panel is held on with six Velcro patches. Ask for daylight photos of both grille fronts and of the backs, where the pegs or fasteners are. Compare the two for fading, since grilles that lived in different light rarely match. A matching pair with even color and intact frames is what you want.
Is it a matched pair?
Factories changed parts during production, so two speakers with the same name aren't always the same speaker. AR's records show the older AR-3 went through at least four crossover revisions keyed to serial-number ranges, and its midrange driver changed in 1970. The AR-3a changed too, swapping an Alnico woofer with a cloth surround for a ceramic-magnet woofer with a foam surround in 1969. Ask for photos of both serial labels. Collectors look for close serials, often consecutive, and the same driver labels and part numbers on both sides. A pair with far-apart serials can still sound fine, but it may have different crossovers or drivers.
Real wood or vinyl?
Veneer is a thin slice of real wood glued over a core of particle board or MDF, and no two sheets look alike. Advent sold most of its speakers both ways, in wood veneer and in vinyl-covered "utility" cabinets that were acoustically identical. EPI did the same with the 100, in walnut veneer or wood-grain vinyl. Neither is a fault, but a listing that says walnut should mean real walnut. In photos, vinyl grain tends to repeat and look flat, and corners show a wrapped seam or a lifting plastic edge. Real veneer shows varied grain, with end grain or banding at the corners. Ask for close-ups of the corners and bottom edges too, since particle board swells and crumbles once it gets wet.
Original or replacement drivers
A different-looking driver isn't automatically a swap. AR changed the AR-3 midrange magnet from a ring type to a potted type partway through production, and both are original. Look-alikes are a real trap on the AR-3a, though. The restoration guide warns that AR-10π and AR-11 cloth domes, yellow-orange or black, won't work without a crossover change, that a ferrofluid replacement tweeter meant for the AR-11 sounds harsh on a stock AR-3a crossover, and that most online sellers can't identify these drivers correctly.
For JBL, part numbers do the work. A 4311 left the factory with a 2213 woofer, an LE5-2 midrange and an LE25 tweeter on a 3112-A network. On a Klipsch Heresy, the originals are the K-22 woofer, the K-55 midrange and the K-77 tweeter, and drop-in substitutes for all three are sold today, so ask which drivers are original. Other signs of a swap are different labels or date stamps between the two speakers, extra screw holes, and solder where the factory used something else. Advent spliced its woofer leads with wire nuts and sealed the drivers with Mortite putty, so soldered joints or missing putty mean someone has been inside.
What to ask for in the listing
- Grilles off. Ask for a straight-on photo of each speaker with the grille removed. Every driver should be there, intact and matching across the pair.
- Woofer edges. Ask for close-ups of each surround in light from the side. Our foam rot guide shows what good looks like.
- Back panels. Ask for both serial labels and the terminal plates. The serials should be close and the terminals clean.
- Sound video. Ask for a short clip of each driver playing at low volume. Each one should be clearly audible.
- Controls. Ask the seller to turn each level control while music plays. You shouldn't hear crackle or dropouts.
- Cabinet corners. Ask for close-ups of the corners and bottom edges. Look for crisp edges and no swelling.
Once a pair passes, check it suits your amp with our amp matching guide, read up on pickup and freight, or browse the speakers we track.