Titanium Diaphragm Purchase Guide

A “titanium diaphragm” might be the moving dome in a loudspeaker or a thin metal element in a pressure device. Both can begin as titanium sheet. Their geometry, interfaces and acceptance tests are not interchangeable.

The purchase risk is not that one application is “more precise” than the other. It is that a component specification can be mistaken for system performance. A measured titanium dome does not prove a driver’s frequency response; a measured pressure diaphragm does not prove a transmitter’s accuracy or pressure rating.

1. Which product is the buyer actually ordering?

For an audio driver, the titanium diaphragm is a moving formed component joined to a voice coil or other assembly features. Its shape and moving mass affect a system designed around a magnetic gap, suspension and acoustic load. For an industrial device, a diaphragm may flex under pressure and form part of a sensor, seal or valve assembly. The medium, pressure direction, edge restraint and joining method then become central. A formed metal part is not a complete speaker driver, pump, valve or pressure transmitter.

If an RFQ says only “75 mm titanium diaphragm,” ask what that diameter means: outside blank, formed dome, active region, seating rim or mating assembly. The answer determines tooling and inspection. If a sample is supplied, identify which attributes should be copied and which require a drawing or target tolerance.

2. How do material and forming route affect the part?

ASTM B265 covers titanium and titanium-alloy strip, sheet and plate within its scope. If it is the specified feedstock route, the order must still identify grade, condition and thickness. A feedstock certificate is useful evidence of material identity; it does not certify that a formed diaphragm has the intended dome profile, residual stress, dynamic behavior or service life.

Forming a thin shell changes the material locally. Tooling, blank size, lubrication, forming sequence and springback can influence profile and thickness distribution. A supplier quoting from an image alone may need to build a new tool, while a supplier with an approved existing tool may quote a different cost and lead time. Ask whether the price includes tooling ownership, trial pieces, dimensional approval and any adjustment cycle.

Choose an acceptance boundary before ordering the first lot. The buyer can use a drawing, a measured master sample or both—but the contract should say which wins if they differ. A visually similar dome may not fit the voice-coil former or seal seat. Conversely, requiring every incidental mark on an old, used sample to be copied is neither realistic nor useful.

3. What matters in an audio diaphragm?

For an audio application, the supplier needs the formed diameter, crown height, profile, corrugation or surround features, rim dimensions and any tabs or bonding land. Thickness and grade affect the component, but the actual acoustic result also depends on the voice coil, adhesive, magnetic system, damping, horn or enclosure and the test fixture. The buyer should therefore describe the driver assembly and the mechanical interface without asking the diaphragm supplier to guarantee a complete driver response from a bare-part drawing.

• Fit: inner and outer diameters, rim flatness or curl, and clearance at the magnetic or mounting interface.
• Mass: whether target component mass or permissible variation is critical to the assembly.
• Profile: height and contour measurement method, including support of a thin flexible part during inspection.
• Bonding: surface state, cleaning, adhesive land and handling requirements set by the driver design.
• Appearance: the defects that matter, such as creases, splits or dents in a moving region.

A prototype should be assessed in the intended driver, not only on a bench. If the driver changes, an earlier acoustic result may not transfer. IEC 60268-21 describes acoustical output-based measurements for electro-acoustical transducers and sound systems; it does not make a loose titanium dome a fully tested speaker.

When a buyer asks for a particular resonance or output curve, clarify whether the target applies to the complete driver or to a controlled property of the diaphragm alone. The component supplier can hold thickness, profile and mass within agreed limits. The driver designer must confirm whether those limits produce the intended acoustic response in its assembly. A lot can pass component inspection while a change in adhesive or voice coil shifts the final response.

4. What changes for a pressure or process diaphragm?

Here the active diameter, corrugation, thickness distribution, edge restraint, weld or clamp and pressure direction govern the component discussion. The process medium and temperature matter to material selection and surface condition. A pressure element may be sensitive to residual stress or local thinning after forming, especially around a corrugation or joining land.

Provide both normal and upset conditions, including differential pressure direction and any cycling requirement. The buyer’s design authority should define allowable deflection, proof/burst requirements and fatigue qualification for the complete device. A supplier can manufacture and inspect a formed diaphragm to the approved drawing; it should not infer a system pressure rating from material thickness alone.

Where a diaphragm will be welded, give the mating part, weld land geometry, cleaning requirement and heat input constraints controlled by the joining procedure. A formed part that passes profile inspection can still fail the assembly if its rim is not suitable for the required joint.

A pressure-diaphragm replacement is easy to mis-specify from a removed sample. Formed height or corrugation can change after pressure cycling or during removal from its housing. If the original drawing is unavailable, measure the mating seat and housing separately, photograph installed orientation and identify dimensions on the old part that may have changed in service. Do not copy every measured feature of a damaged sample as the intended new-part geometry.

5. Which component measurements are worth buying?

Inspect the features that control assembly or function: material lot and thickness, formed contour, active diameter, rim position, defects and specified surface state. For a thin flexible part, the measurement fixture matters. A profile measured while the part is clamped can differ from its free state; specify the state used for acceptance.

Use a defined sample plan or first-article approval when tooling is new. If a critical shape is assessed optically, the report should identify reference points and allowable variation. A simple photograph is useful for discussion but cannot substitute for a dimensioned profile when fit is tight. The finished part should remain traceable to its material lot and forming batch.

Do not request an acoustic or pressure performance report from a supplier who is only delivering bare formed components unless the test fixture, mating assembly and responsibility have been supplied and agreed. The strongest report is one whose test subject is clearly identified: raw sheet, formed diaphragm or complete device.

For repeat supply, tie the approved first article to tool revision, material condition and inspection fixture. A later change of sheet source, forming tool or edge trimming can affect the part even when the purchase-order description stays unchanged. Ask how such changes are identified before a new production lot is accepted.

6. Where does component acceptance end and system qualification begin?

Audio response, resonance and distortion are measured in the assembled driver under stated conditions. Sensor accuracy, hysteresis, proof/burst response and cycle life are assessed in the completed pressure system or a representative qualified assembly. The diaphragm contributes to those outcomes, but the surrounding components and assembly process also matter. The buyer should reserve system-level targets for the party responsible for the system.

This boundary helps both sides compare quotes. A component supplier may include tooling, formed parts, dimensional inspection and material records. Another may include bonding or welding and assembly testing. Put those operations in separate line items; otherwise the cheaper offer may merely stop earlier in the process.

The HELE titanium diaphragm product page shows the component family. The quotation should name which application path and which delivered stage applies, not imply that one generic diaphragm serves every audio and industrial design.

7. What should the RFQ include?

• Audio or industrial application, mating assembly drawing and required delivered stage.
• Grade, feedstock standard/condition, thickness, blank size and formed profile.
• Critical diameters, rim/weld/bond interface, surface and accepted measurement state.
• Tooling, prototype/first article, production quantity and revision control.
• Component material/dimensional records and any separately agreed assembly tests.

A good RFQ tells a supplier what the component must be and tells the system designer which performance claims still require assembly testing. That is more useful than asking for “titanium diaphragm with excellent sound” or “high pressure resistance” without the assembly.

Questions buyers often ask