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How to check used speakers
Speakers age in two ways that photographs cannot show: the foam around the driver cone rots from the inside out, and the electrolytic capacitors in the amplifier dry up. Both are ordinary consequences of time rather than abuse, and both are entirely audible if you know what to play.
The short answer
Put your ear close to each driver with nothing playing, then play a low sine tone. Silence at idle and a clean tone at 40-60Hz rules out the two faults that account for most dead used speakers — amplifier hum and a perished surround.
Get these first
Two faults, and how to hear both in five minutes
- Power them on with nothing connected and put your ear to each driver. A healthy powered speaker is essentially silent at idle. A mains-frequency hum, a buzz, or a hiss that rises with the volume control points at failing capacitors in the power section — which is the most common end-of-life fault in powered monitors and in any amplifier over about fifteen years old.
- Inspect the foam surround around every driver, including the rear of the cone. Press gently at the edge of the cone and look for cracks, crumbling, or a surround that has gone hard and shiny. Foam surrounds perish with age and humidity whether the speakers were used or stored, and a perished surround is a rebuild rather than a repair.
- Play a slow low sweep from about 30Hz to 200Hz at moderate volume. Listen for a dry rasp, a ticking, or an abrupt rattle. That sound is the voice coil rubbing in its gap or a damaged surround letting the cone move off-axis. It is a distinct texture from the normal limit of a small driver running out of excursion, and once you have heard it you will always recognise it.
- Rotate every potentiometer through its full travel while audio plays. Crackling, cutting out, or a channel that jumps in level is dirty or worn pots. This is an easy and cheap repair with contact cleaner on most designs — so it is a bargaining point rather than a reason to walk, provided the knobs are accessible.
- Test every input, not just the one that is connected. RCA, TRS, XLR, optical and Bluetooth all go through different circuitry, and it is entirely normal for one to have failed while the others work. The seller will have tested whichever one they used.
- Check channel balance with a mono signal, sitting equidistant from both. Play a centred mono tone and confirm the image sits in the middle. A drifting or off-centre image means one amplifier channel or one driver is down, which on a matched pair is worse than it sounds — you cannot replace one and keep them matched.
- On multi-driver speakers, confirm the tweeter is actually working. Play something with sustained high-frequency content, or a tone around 10kHz, and put your ear near the tweeter specifically. A dead tweeter is easy to miss in a quick listen because the woofer keeps producing most of what you notice, and it is the single most common silent fault on used bookshelf speakers.
- Ask for the original cables, remote and power supply. Active monitors frequently use proprietary inter-speaker cabling, and subwoofer systems often route everything through the sub with a captive lead. A missing remote on a system whose volume can only be set by remote is a far bigger problem than it sounds.
The one nobody checks
The tweeter. A speaker with a dead tweeter still plays, still sounds loud, and still sounds broadly like a speaker — the woofer covers everything you notice in a quick demonstration. Buyers listen to a track, hear sound from both boxes, and conclude that both boxes work. Put your ear within a few centimetres of each tweeter specifically, with high-frequency content playing.
Note
Age matters more than hours in this category, which is the opposite of most of the marketplace. A lightly used pair that has sat in a humid store room for twelve years can have worse surrounds and worse capacitors than a heavily used pair from five years ago. Ask when they were made, not how much they were played.
What to measure
Higher is better▲Higher is betterLower is better▼Lower is betterMust be zero∅Must be zeroMust match the spec=Must match the spec
What you are listening for
| Metric | Which way | What it tells you | Healthy looks like |
|---|---|---|---|
| Idle hum or buzz | Must be zero | Ageing electrolytic capacitors in the power section. | Silent with your ear at the driver and nothing playing. |
| Surround condition | Must be zero | Foam that perishes with time regardless of use. | Supple, no cracking or crumbling at the cone edge. |
| Low sweep cleanliness | Must be zero | Voice coil rub or a cone moving off-axis. | Clean tone with no rasp or tick through 30-200Hz. |
| Potentiometer behaviour | Must be zero | Wear in the only moving controls. | Smooth through full travel. Crackle is cheap to fix but worth a discount. |
| All inputs working | Must be zero | Separate circuitry that fails separately. | Every input tested, including the ones you do not plan to use. |
| Mono image centred | Must match the spec | Whether both channels are equally healthy. | Image sits centre. Drift means a channel or driver is down. |
| Tweeter output | Must be zero | The most commonly missed silent fault. | Clearly audible at the tweeter on high-frequency content. |
| Cables, remote, PSU present | Higher is better | Frequently proprietary and sometimes essential. | All present. A volume-by-remote-only system without its remote is unusable. |
Walk away if
Walk away if
- Hum or buzz at idle with your ear at the driver.
- Cracked, crumbling or hardened foam surrounds.
- Rasp or tick on a low sweep.
- A tweeter producing nothing.
- An off-centre image on a mono signal.
- A missing remote on a system with no physical volume control.
- A seller who has only ever used one input.
What each fault is worth
Bring the measurement, not the opinion. Name the fault, name the fix, name what the fix costs — that is a solvable problem with two acceptable answers, which is what makes it work.
| What you found | What it actually costs | What to ask for |
|---|---|---|
| Idle hum | A recap, or a short remaining life. | A large discount unless you are willing to solder. |
| Perished surrounds | A driver rebuild. | The cost of a re-foam kit plus the afternoon it takes. |
| Dead tweeter | A matched-pair problem. | Walk away on a pair; you cannot replace one and stay matched. |
| Crackly pots | Contact cleaner and twenty minutes. | A small discount — this one is genuinely easy. |
| Missing proprietary cable or remote | Possibly an unusable system. | Confirm a replacement exists before you buy at any price. |
Ready to go looking?
Take the checklist with you, then browse what is listed. Everything on this page works just as well the other way round when you are the one selling.
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