How buyers verify an audio order before the balance is paid: what to sample, what to test, how to classify defects and what to do when a lot fails.
AQL stands for Acceptable Quality Limit. It is the worst average defect level that you are willing to accept in a lot. The practical output is simple: for a given lot size, you inspect a defined number of random units, and if the number of defective units found is at or below the acceptance number, the lot passes. If it is at or above the rejection number, the lot fails.
The sampling tables most often used for consumer goods come from ISO 2859-1, closely related to ANSI/ASQ Z1.4. Because the sample is random, passing does not mean there are no defects in the lot; it means the defect level is within the agreed tolerance. That is why the choice of AQL and the definitions of each defect class matter more than the percentage itself.
| Class | Definition | Examples | Common AQL |
|---|---|---|---|
| Critical | Could cause injury or break safety or legal rules | Battery swelling or overheating, exposed live parts, missing certification marks on required products | 0 (none allowed) |
| Major | Makes the product unusable or likely to be returned | No power, no bluetooth pairing, distorted or rattling sound, a button that does not work, wrong color or logo | 2.5 |
| Minor | Cosmetic or small deviation that does not affect function | Small scratch, glue mark, slight color variation, minor print offset | 4.0 |
Write these definitions into the purchase order with photos of acceptable and unacceptable samples. Without a written standard, the same scratch can be "minor" to the factory and "major" to you.
The table below shows single sampling at General Inspection Level II, normal severity. "Ac" is the acceptance number and "Re" is the rejection number.
| Lot size (pcs) | Sample size | Major AQL 2.5 (Ac / Re) | Minor AQL 4.0 (Ac / Re) |
|---|---|---|---|
| 281 to 500 | 50 | 3 / 4 | 5 / 6 |
| 501 to 1,200 | 80 | 5 / 6 | 7 / 8 |
| 1,201 to 3,200 | 125 | 7 / 8 | 10 / 11 |
| 3,201 to 10,000 | 200 | 10 / 11 | 14 / 15 |
| 10,001 to 35,000 | 315 | 14 / 15 | 21 / 22 |
Example: a 3,000-piece lot needs 125 units inspected. With AQL 2.5 for major defects, the lot passes if no more than 7 units have a major defect and fails at 8. Critical defects are not traded off against the count: a single critical defect normally fails the lot. If you ship in several colors or models, sample each variant proportionally. Tables vary slightly by edition, so ask your inspection company to confirm the plan it will use.
Our own factory runs incoming, in-process, aging and final inspections, but an independent check adds a neutral view, particularly for a first order. You can also ask us to host an inspector or a video inspection before shipment.
A visual check is the smallest part of a speaker inspection. Include at least these functional tests, using the approved sample as the reference:
Packaging errors are among the most common reasons marketplaces reject inbound shipments, so spend time here. For shipping-related requirements for battery products, see our shipping guide.
Knowing where defects come from lets you ask sharper questions and target your inspection time. These are patterns that show up repeatedly in audio production:
| Defect | Likely cause | How to prevent |
|---|---|---|
| Rattle or buzz at high volume | Loose internal parts, glue gaps, poorly seated driver or passive radiator | Sweep test at maximum volume on every unit at the end of the line |
| Bluetooth drops or short range | Antenna placement, poor solder joint, shielding changes | Range test on sample units; compare against the golden sample |
| Short battery life | Lower-capacity cell substituted, firmware power settings | Verify cell model and run a timed playback on sampled units |
| Battery swelling after aging | Cell defect, overcharge, heat | Aging test and cell traceability records; treat as critical |
| Water ingress on rated models | Gasket pinched, adhesive gaps, port cover not seated | In-line leak test and sample immersion tests |
| Scratches or print offset | Handling, tray design, printing alignment | Limit samples and packing trays that separate units |
| Wrong accessory or manual | Packing-line mix-ups between models | Packing checklist and carton opening checks |
Ask the factory for defect statistics from earlier runs and what corrective actions it took. A supplier that tracks its own defect data usually fixes problems faster.
Agree the remedy before production, not after. Typical options are rework and re-inspection at the factory's cost, replacement of defective units, a price adjustment for minor issues, or rejection of the lot for critical or widespread defects. Keep inspection photos, the signed report and the sample references together; they are your evidence if there is a dispute. Do not release the balance payment until the report shows a pass or the agreed remedy is complete.
For more on vetting the factory itself before you inspect its output, read our 7-point supplier checklist.
A common starting point is zero for critical defects, 2.5 for major and 4.0 for minor defects at General Inspection Level II. Stricter levels such as 1.5 for major defects suit premium products but cost more.
No. AQL is a statistical test of a sample. It tells you the lot is within a tolerance, not that every unit is defect-free.
At General Inspection Level II, a lot of 501 to 1,200 pieces uses a sample of 80 units. With AQL 2.5 for major defects, up to 5 major defects are accepted and 6 fail the lot.
Book it when production is complete and at least 80 percent of cartons are packed, and before you pay the balance. For a new supplier, also add a during-production check.
Factory QC is essential but not independent. For first orders, large orders or new products, a third-party or buyer-led inspection gives a neutral confirmation.
Refer back to the written defect definitions, the golden sample and the photo report in your purchase order. Having these agreed in advance resolves most disputes.
Ask for a sample, our inspection report format or a live video factory tour. We reply within 12 hours.