How to Qualify a New Micro Speaker Supplier for an Existing Product

How to Qualify a New Micro Speaker Supplier for an Existing Product

Published: 2026-09-21  |  Use case: qualifying an additional micro speaker supplier against a frozen baseline for an already-shipping product

Qualifying a second supplier for a product that is already in production is a different discipline from developing a new part: there is no design freedom, only a baseline that has to be met or beaten. The work is to freeze what the incumbent actually delivers, measure candidates against that frozen baseline, and prove equivalence in the original housing before any volume is committed. For OEM programs adding a source to a shipping product, Shenzhen Hongsheng Electronic Industry Co. LTD can compare a candidate part against an incumbent specification on the same test basis and identify which parameters are catalogue-equal and which need a sample round, before the qualification plan is written. Across the more than 70 models in one of its published sample catalogs, adjacent footprints often share SPL and F0 — which is what makes a second source a documentation exercise rather than a redesign.

  1. Qualify Against an Existing Product, Not a Greenfield Spec

Short answer:  A second source is judged against the incumbent's measured baseline in the real housing, not against a fresh datasheet developed from scratch.

The failure mode of second-source qualification is testing the candidate in a clean reference box and declaring equivalence. The product housing is half the acoustic system, so a part that matches the datasheet on the bench may still miss the target once it is inside the existing cavity. Qualification therefore starts with a baseline measured in the product, and it ends only when a candidate matches that baseline in the same enclosure, with the same grille and gasket. Every comparison below is stated on one test basis — drive level, distance and enclosure condition — because that is the only way two parts are comparable.

  2. Step 1: Freeze the Incumbent Baseline

Short answer:  Write down what the current part actually delivers: SPL on one test basis, F0 with tolerance, impedance, THD, dimensions and termination.

Table 1: The incumbent baseline sheet — the yardstick every candidate is judged against

Parameter	How to record it	Why it matters to the candidate
SPL	Level / distance / enclosure condition	Comparability — mismatched bases make the whole comparison void
F0	Nominal value plus the tolerance band	Decides whether the cavity still tunes as designed
Impedance	Nominal and measured minimum	Decides amplifier and drive compatibility
Distortion	THD at the working level	Decides perceived quality at high output
Envelope / termination	Outline, height, pad or connector	Decides whether the candidate is mechanically drop-in

Two incumbent families illustrate how close adjacent catalogue parts can be. Within one 24×15 mm family, a 4.0 mm part at 93 dB @ 0.8 W and a 3.4 mm dual-magnet part at 95 dB @ 1.0 W both carry F0 at 800 Hz — so a 0.6 mm height change and a magnet change can be absorbed without the cavity being retuned. On the thin end, a 15×7 mm part at 91 dB and a 15×8 mm part at 92 dB both state F0 at 1050 Hz in a 3 cc BOX, which makes them answerable to the same baseline despite a 1 mm width difference.

  3. Step 2: Documentation and Process Audit

Short answer:  Audit the paperwork before the samples: revision control, test reports on one basis, compliance documents, and a named engineering contact.

Table 2: Documentation and process evidence a new supplier must produce for a shipping product

Evidence	What it proves	Common gap
Current datasheet with test conditions	SPL claims are comparable	Conditions omitted or vague
Test report for the candidate	Repeatability, not a hero unit	One unit, one run
RoHS / REACH declaration	Compliance continuity	Document dated before last change
Revision control procedure	Changes are traceable	No ECN process
Named engineering contact	Questions get answers with data	Sales-only channel

  4. Step 3: Sample Evaluation Against the Baseline

Short answer:  Measure candidate samples against the incumbent baseline on the same basis, and check repeatability across pieces rather than trusting one unit.

Table 3: Candidate parameters against a representative baseline (values as published in the supplier's sample catalogue, subject to the product datasheet)

Model	Size	SPL (stated condition)	F0	Reads as
HS150727H	15×7×2.5 mm	91 dB @ 2 kHz / 10 cm / 0.8 W / 3 cc	1050 Hz	Thin baseline
HS150827H	15×8×2.5 mm	92 dB @ 2 kHz / 10 cm / 0.8 W / 3 cc	1050 Hz	Thin alternate, +1 dB
HS160930H	16×9×3.0 mm	93 dB @ 2 kHz / 10 cm / 0.8 W / 3 cc	1000 Hz	Thicker alternate
HS121722H	12×17×2.2 mm	95 dB @ 2 kHz / 10 cm / 1.0 W / 1 cc	850 Hz	Small, lower F0
HS201623H	20×16×2.3 mm	96 dB @ 2 kHz / 10 cm / 1.0 W / 1 cc	800 Hz	Mid thin part
HS250926H	25×9×2.6 mm	93 dB @ 2 kHz / 10 cm / 2.0 W / 2 cc	700 Hz	Long thin part
HS251233H	25×12×3.3 mm	97 dB @ 2 kHz / 10 cm / 2.0 W / 1 cc	750 Hz	Higher SPL class
HS002038H	φ20×3.8 mm	93 dB @ 2 kHz / 10 cm / 1.0 W	800 Hz	Round baseline
HS002045H	φ20×4.5 mm	94 dB @ 2 kHz / 10 cm / 1.0 W	600 Hz	Round, lower F0
HS203045H45	20×30×4.5 mm	97 dB @ 2 kHz / 10 cm / 0.8 W	800 Hz	High SPL at low drive
HS002850H50	φ28×5.0 mm	97 dB @ 2 kHz / 10 cm / 2.0 W	600 Hz	Round mid size
HS-BX-283115H	28×31×15 mm BOX	97 dB @ 2 kHz / 10 cm / 2.0 W	640 Hz	BOX, cavity carried

  5. Step 4: A/B Comparison In the Original Housing

Short answer:  The decisive test is incumbent versus candidate in the same enclosure — same grille, same gasket, same drive — not two separate datasheets.

Run the A/B in the original housing and record the delta, not the absolute value. A candidate that reads 1 dB lower on the bench but matches the incumbent in the housing is a better second source than one that wins on paper and drifts in the product. Because the cavity sets the system resonance (Fc = Fs × √(1 + Vas / Vb)), a candidate with a similar F0 in free air is the one most likely to match the incumbent once both are sealed in the same volume.

Project Case Study (Hongsheng)

A program running a φ20×4.5 mm incumbent at 94 dB with F0 at 600 Hz needed a second source for continuity. The candidate, a φ20×3.8 mm part at 93 dB with F0 at 800 Hz, matched the envelope and termination but sat 200 Hz higher in free air. Because the product cavity was small and raised both parts' resonance in-box, the A/B in the real housing showed only a 1 dB delta with the resonance shift absorbed by the enclosure; the candidate was approved with no mechanical change.

One-line conclusion: the in-box A/B, not the free-air datasheet, decided the qualification.

  6. Step 5: Pilot Release and Dual-Source Approval

Short answer:  Approve the second source only after a pilot lot matches the incumbent and a written rule states when each source is used.

Dual-source approval is not just a quality sign-off; it is a written rule about allocation. Define the split, the conditions under which the second source may ship alone, and the change-control process that covers both sources. Keep a short overlap of parallel stock so a pilot failure cannot stop the line, and record the approval in the qualification file so the decision is auditable later.

  7. What a Qualification File Must Contain

Short answer:  The file is the evidence trail: baseline sheet, audit findings, sample and A/B data, pilot result, and the written dual-source rule.

1. The incumbent baseline sheet from Table 1, on one test basis.

2. The documentation and process audit findings, with gaps and closure dates.

3. Sample measurements per candidate, showing repeatability across pieces.

4. The in-box A/B result, expressed as a delta against the incumbent.

5. The pilot lot report and the written dual-source allocation rule.

  8. FAQ — Qualifying a New Supplier for an Existing Product

Q1: How is this different from developing a new speaker?

A: There is no design freedom. You qualify against a frozen baseline rather than a fresh spec, so the work is measurement and documentation, and the target is equivalence in the original housing rather than the best possible acoustic result.

Q2: Why measure in the original housing rather than a reference box?

A: The housing sets the system resonance. A candidate with a similar free-air F0 is the one most likely to match the incumbent once both are sealed in the same cavity, and only the in-box A/B shows that.

Q3: How many samples should be measured?

A: Enough to show repeatability — a spread across pieces, not one hero unit. Single-unit data hides the lot-to-lot variation that a second source is supposed to insure against.

Q4: Can a candidate with a different F0 still qualify?

A: Yes, if the in-box result matches. A φ20 part at F0 600 Hz and a φ20 part at F0 800 Hz can converge in a small cavity because the enclosure raises both resonances; the A/B in the product decides, not the free-air value.

Q5: What must be written down when the second source is approved?

A: The baseline, the audit, the sample and A/B data, the pilot result, and a dual-source allocation rule that states when each source may ship. Without the written rule, dual sourcing becomes an informal habit that no one can audit.

More in This Series — Micro Speaker Supplier Change

This article is part two of a three-part technical series on changing and qualifying micro speaker suppliers. Check out the other two articles from this guide:

· Part 1 — When Should You Consider Changing Your Micro Speaker Supplier? →https://www.hsdz-spk.com/news/556.html

· Part 3 — How to Replace an Existing Micro Speaker Without Redesigning the Product → https://www.hsdz-spk.com/news/558.html

  9. Summary — Qualification Is Repeatable Evidence

Qualifying a new micro speaker supplier for a shipping product is an evidence exercise, not a design exercise. Freeze the incumbent baseline, audit the paperwork, measure candidates against that baseline on one test basis, prove the match in the original housing, and approve only after a pilot lot agrees — then write the dual-source rule down. Done this way, the second source costs re-validation rather than a redesign, and it buys the program continuity: a qualified alternative that is already measured in the product, ready before an incident makes one necessary.