What Information Should You Provide When Requesting a Custom Micro Speaker?
1. Why a Complete Package Is Not the Right Goal
Short answer: Waiting for a complete specification before asking delays the most useful feedback. The information that decides feasibility is a small subset, and it is usually available early.
Three of the items usually listed as prerequisites are, in practice, outcomes rather than inputs. The resonance frequency depends on the cavity volume, which depends on the structure. The power rating depends on the amplifier's voltage and impedance. The sensitivity figure depends on the measurement basis, which depends on what the product can accommodate. Asking a customer to supply all three before a conversation starts is asking them to make decisions that require the conversation in order to make.
The consequence is a familiar delay: the request waits several weeks for a complete package, and the reply is a quotation against numbers that were guesses. The alternative is to separate the information into what decides feasibility, what decides cost, and what can be settled during development. The first group is small and almost always available at first contact.
2. Tier One: What Decides Whether the Target Is Reachable
Short answer: Six items decide feasibility, and all six are facts rather than decisions. They are cheap to state and they are what makes an early answer possible.
1. The space available, stated as a mounting height the product must give up and a volume the structure can actually seal. These two numbers rule out entire driver families before any acoustic discussion.
2. The frequency band the product uses. This decides which driver is appropriate at all, and it is the item most often omitted.
3. The listening distance and the noise floor at that distance. These set the level the output has to clear.
4. The amplifier's usable voltage and the impedance it will drive. Together these set the reachable power, and a configuration the rail cannot drive is not a candidate.
5. The content type. Voice announcement, music and warning tones lead to different targets, and a voice-only product can often specify less than a music product of the same size.
6. Whether the requirement is a minimum level or a maximum. These two run in opposite directions, and a programme that has not decided which it is will change direction mid-development.
These six are facts about the product rather than decisions about the component, which is why they can be supplied early. They are also sufficient for a first answer: with the space, the band and the voltage known, a supplier can state whether the target is reachable, which parameter has to move, and whether the change is a parameter change or a tooling change.
3. Tier Two: What Decides Cost and Schedule
Short answer: Volume, schedule and tolerance requirements decide price and lead time, and they can usually follow the feasibility answer. They matter most when they change which platform is used.
7. Expected production volume and the timing of the first order. Volume decides whether a validated platform can be reused, which is the largest single cost lever in a custom programme.
8. Tolerance requirements beyond the published ones. A tighter tolerance is achievable, but it is a manufacturing decision with a cost, not a free specification.
9. The measurement basis required for acceptance. This determines whether the supplier's existing test conditions can be used or a new fixture is needed.
10. Compliance and environmental requirements. These decide whether the standard platform's qualification is sufficient or additional testing is needed.
11. Termination and mounting preferences. Normally a changeable parameter on an existing platform, but worth stating early because it affects the assembly sequence.
The reason these belong in a second tier is not that they are unimportant; it is that they rarely change the feasibility answer and they frequently change during a programme. A volume forecast that moves from 5,000 to 50,000 units changes the cost model substantially and the acoustic design not at all. Stating them early is useful, but waiting for them to be final before asking the first question is not.
4. Tier Three: What Gets Settled During Development
Short answer: Several figures that look like requirements are outcomes of the development process. Treating them as inputs is what causes specifications to be rewritten.
12. The exact resonance frequency. This follows from the driver and the cavity, and is normally agreed once the installed value has been measured.
13. The final sensitivity figure and its measurement basis. These settle when the test conditions are agreed, which is usually after the first sample.
14. Detailed distortion and bandwidth targets. These depend on the driver platform and are normally confirmed against measurements rather than stated in advance.
15. Final dimensions including tolerances. The nominal dimensions follow from the platform; the tolerances are a manufacturing decision with cost consequences.
None of this means these items are unimportant. It means they are negotiated rather than supplied, and a programme that treats them as inputs will rewrite its own specification at least once. Writing them as targets with a stated basis, rather than as fixed numbers, is what keeps the specification stable.
5. What Each Published Dimension Tells You
Short answer: A supplier's published range shows which dimensions are already available, which tells you which of your requirements are selections and which are developments.
Table 1 summarises the dimensions across one published sample catalogue. Reading it against your own requirement tells you immediately whether you are selecting from existing options or asking for something new, which is the difference between a short programme and a long one.
Table 1: Published dimensions across a sample catalogue, and what each one implies for a request.
Dimension | Published options in the range | If your requirement falls inside | If it falls outside |
Rated impedance | 4 Ω, 7 Ω, 8 Ω and 32 Ω | A selection; the drive voltage follows from the power you need | A development, and worth questioning whether the impedance is really the constraint |
Rated power | 0.05 W, 0.5 W, 0.8 W, 1.0 W, 2.0 W, 2.5 W, 3.0 W, 5.0 W, 10.0 W | A selection within a power class | A development; check first whether the amplifier can supply the voltage the class needs |
Test voltage in the published figures | 1.26 V, 2.0 V, 2.53 V, 2.83 V, 3.16 V, 3.46 V, 4.0 V, 4.47 V, 6.32 V | Directly comparable against your own measurement conditions | A request for a different basis, which has to be stated explicitly |
F0 tolerance as published | ±15% across the range | Directly usable | A tighter tolerance is achievable but is a manufacturing decision with cost |
Cavity volume in published BOX figures | 1 cc, 2 cc, 3 cc and 4 cc | Comparable against the volume your structure can seal | A development; check what the installed resonance becomes at your volume |
Termination | Solder type, leaf spring or spring contact, lead wire | A selection, normally changeable on an existing platform | A development, usually one of the cheaper ones |
Mounting configuration | Bare driver and cavity module (BOX) configurations | A selection | A development; note that cavity modules require a defined host cavity |
Project Case Study (Hongsheng) — A Request That Started With Six Facts
The requirement came from an outdoor driving-test ground, where units are installed in roadside posts and announcements have to be understood at 3 m in daylight. The customer's specification included long-term outdoor exposure, moisture resistance and a temperature rise under direct sun. What they brought to the first exchange was not a complete package: it was a size, an impedance, a power, and the statement that more than ten full-range 40 mm candidates had already been evaluated without meeting the requirement.
That last item was the most useful thing in the request, because it identified the tier-one information that was missing. Once the frequency band was established — roughly 1 to 4 kHz at a 3 m distance with outdoor noise present — the reason repeated substitution had failed became clear. General-purpose 40 mm drivers are full-range designs whose energy concentrates in the low midrange, so the share of output inside the speech band is low. At matched power the midrange level was insufficient, and no choice of full-range model changes that, because the constraint is the frequency band rather than the model.
With the band established, the tier-one facts were sufficient to proceed without the rest of the package. The driver was specified for the band rather than for the size. The diaphragm material was changed to a polyester film, raising level in the 1 to 4 kHz band. The free-air resonance was designed to 900 Hz, placing the resonance peak in the midrange rather than below it, which is the reverse of the usual expectation that a lower resonance is always better. Test points were placed inside the speech band at 0.5, 0.8, 1.0 and 1.2 kHz rather than at a conventional single 2 kHz point, so the published figures describe the band the product uses.
The tier-two and tier-three items were then settled during development rather than supplied in advance. The final sensitivity of 110 ± 3 dB average was measured at 10 cm at 0.1 W input, a basis chosen so the figure is not confused with power-driven measurements. The rating was reduced from 10 W to 5 W with a 6 W maximum. Environmental qualification followed the product definition: temperature shock between −20 and +70 °C, static damp heat for 48 h, a 0.75 m drop test repeated ten times, a 48 h load test, plus lead-pull checks at 3.0 N horizontal and 2.0 N vertical, with the acceptance baseline that all testing returns the response within a stated deviation of the baseline.
Three parameter changes on the same 40 mm platform delivered the remaining level without new tooling: a secondary magnet added 2 dB, a shim adjustment reducing the magnetic gap from 0.25 mm to 0.18 mm added 1 dB, and a copper-clad aluminium voice coil added 3 dB. The programme is in production with 15,000 units shipped, and the unit price moved from 10 RMB to 6 RMB, saving the customer 60,000 RMB across the shipped quantity while the measured level rose. The transferable point about the request itself is narrow: the information that unblocked it was a frequency band and a listening distance, not a complete specification.
The request arrived with a size, an impedance and a power, and the useful part was the note that ten full-range drivers had already failed. What unblocked it was a frequency band and a listening distance, not a complete package.
The distinction between the tiers matters because it determines when a programme can start. Hongsheng can evaluate the six tier-one facts against a published configuration and state which parameter has to move, before the remaining information is complete.
6. A Minimum Viable Request
Short answer: Six lines are enough to get a useful first answer, and none of them requires a decision that has not been made yet.
16. The mounting height the product can give up, including cover and tolerance stack.
17. The volume the structure can seal, and the dimensions it cannot give up.
18. The frequency band the product uses, as a range.
19. The listening distance and, if known, the noise floor there.
20. The amplifier's usable voltage and the impedance it will drive.
21. Whether the requirement is a minimum level or a maximum, and whether a reference unit exists.
With those six lines a supplier can state whether the target is reachable in the available space, which parameter has to move, and whether the change is a parameter adjustment or a tooling decision. Everything else can follow, and most of it should.
7. FAQ: Information for a Custom Speaker Request
Q1: Do I need a complete specification before I can ask for a quote?
No, and waiting for one usually costs time without improving the answer. Six facts are enough for a useful first response: mounting height, sealable volume, frequency band, listening distance, amplifier voltage and impedance, and whether the requirement is a minimum or a maximum.
Q2: Which single piece of information is most often missing?
The frequency band the product uses. Without it a supplier can match size and power but cannot know whether the driver suits the application, which is why programmes sometimes meet every stated number and still fail subjectively.
Q3: Should I specify the resonance frequency?
Specify the installed resonance you need and the band you use, not a free-air value. The installed resonance follows from the cavity through FC = Fs × √(1 + Vas / Vb), so it is normally agreed once the volume is known rather than stated in advance.
Q4: What if I do not know the cavity volume yet?
State the volume the structure could seal if it were reserved, and say that it is not yet committed. A supplier can then state what the installed resonance would be at that volume and at a smaller one, which is usually the information that gets the volume reserved.
Q5: How important is the measurement basis?
It decides whether any comparison is meaningful. Frequency, distance, drive voltage, cavity volume and mounting surface all have to match. In one published catalogue, two configurations state different cavity volumes for their sensitivity and resonance figures, so even two numbers from the same row may not describe the same condition.
Q6: My requirement is subjective. What do I send?
A reference unit, or a description of one. A subjective requirement becomes measurable when there is something to measure it against, and the comparison then becomes part of the specification.
Q7: What can wait until after the first sample?
The exact sensitivity figure and its basis, detailed distortion and bandwidth targets, final tolerances, and the compliance test plan. These are outcomes of the development process, and treating them as inputs is what causes specifications to be rewritten.
Hongsheng publishes configurations across impedance, power and termination classes with the measurement basis stated for each, so the six tier-one facts can be checked against existing options before anything is committed.
8. Summary: Give the Deciding Facts First
A request for a custom micro speaker does not need to be complete to be useful, and insisting on completeness usually delays the feedback that matters. The information that decides feasibility is six facts about the product — mounting height, sealable volume, frequency band, listening distance, amplifier voltage and impedance, and whether the requirement is a minimum or a maximum — and all six are available early because they are facts rather than decisions.
The remaining information sorts into what decides cost and schedule, which is worth stating but rarely changes the feasibility answer, and what is settled during development, which is negotiated rather than supplied. Reading a supplier's published dimensions against your own requirement tells you immediately which of your items are selections and which are developments, and that distinction is what separates a short programme from a long one. Hongsheng's published configurations state their termination, cavity condition and measurement basis, so the six facts can be checked against existing options before anything is committed.
Next step If you are preparing a request for a custom micro speaker, the shortest route to a useful first answer is to state five things: the space available for the driver and its cavity, the impedance the amplifier will drive, the power the rail can supply, the level required at the intended listening position, and the frequency band the product actually uses. With those specified, our engineering team can recommend a suitable configuration for evaluation, or state plainly which part of the acoustic design has to change first.
More in This Series
· Micro Speaker RFQ: Which Specs Actually Move Price and Lead Time →https://www.hsdz-spk.com/news/588.html
· Micro Speaker Sample Development: What OEM Buyers Should Expect →https://www.hsdz-spk.com/news/590.html