The Speaker Adhesive RFQ: Send Both Substrates, Not a Product Name

You send four Dongguan adhesive suppliers the same message: "Please quote your speaker surround adhesive, 500 kg, FOB Shenzhen." Three reply within the day with a price and a lead time. One replies with questions. You put the fast three in a spreadsheet and mentally file the fourth as slow.

You have just ranked the four suppliers in reverse order of competence. A speaker adhesive RFQ that names a product category and a quantity has not asked a question anyone can answer, because adhesion is not a property of the adhesive. It is a property of the joint — this polymer, against those two surfaces, in that geometry, cured on your line's clock. Send both substrates and the cure window, and the quotes come back comparable and, more usefully, correct. Here is what belongs in the enquiry and why each field changes the answer.

Why a product name is not a specification

A part number for a resistor is a specification. A part number for an adhesive is a starting point for a conversation, because the same product will hold one joint for ten years and fail another in six weeks depending entirely on what it is stuck to.

Three consequences follow, and they are the reason experienced adhesive buyers write long enquiries:

• There is no like-for-like across suppliers. "Water-based surround adhesive" from two houses can be a styrene-butadiene latex and an acrylic emulsion. Both are correct descriptions. They behave differently against a coated paper cone.
• A quote against a category is a quote against the supplier's assumption of your joint. If the assumption is wrong, the price is right and the product is wrong, and you will not find out until the pilot build.
• The information asymmetry runs the other way from most sourcing. Usually you know your product and the supplier knows their process. Here the supplier knows a great deal about what fails on a driver, and can only apply it if you tell them what your driver is made of.

Suppliers that specialise in this assembly say so directly. The CMH listing for Aosibo Adhesives, whose range covers lead-wire, damper, water-based foam and rubber surround and magnet-circuit adhesives, puts it in one line on its own product page: mix ratio, pot life, fixture time, full-cure schedule and substrate compatibility are all order-specific — send the two substrates and the cure window you have available. Its FAQ repeats it: viscosity, cure schedule, pot life and substrate data are shared at inquiry. That is not evasion. That is the correct order of operations.

The two-substrate rule

Both sides, named by material and grade

Every bond has two faces, and a supplier told about one of them is guessing about half the joint. For a driver, name both sides explicitly:

"Steel" is not a substrate. "Cold-rolled steel, e-coated" is. "Plastic" is worse than useless; a polypropylene basket and a glass-filled ABS basket are opposite problems, because untreated polyolefins are low-surface-energy and generally need flame, corona or plasma treatment or a primer before any adhesive is a fair test.

Surface condition is part of the substrate

This is the field that separates an RFQ written by someone who has debugged a bond failure from one written by someone who has not. The surface a supplier's chemist imagines is clean. The surface on your line usually is not.

Tell them:

• What is on the metal. Drawing or stamping oil, rust preventative, phosphate conversion coating, e-coat, plating. Then tell them the cleaning step, if there is one — solvent wipe, alkaline wash, or nothing.
• What is on the rubber. Moulded rubber surrounds carry mould release. If the parts are not washed or abraded, say so; the supplier's recommendation will differ.
• What is in the foam. Plasticiser migration out of a flexible foam or a PVC-adjacent part softens a cured film over months. This is a long-horizon failure, so it never shows up in a two-week sample test — it has to be designed out at quotation.
• What is on the paper. Cone sizing, damping compound and any surface coating change absorption behaviour, which is decisive for waterborne systems.
• What the parts have been through. Warehouse humidity, whether parts sit for days between operations, whether anything is handled bare-handed.

Also send the failure you are trying to prevent, not only the bond you are trying to make. "Spider adhesive" and "spider adhesive, because we are seeing the bond line craze after thermal cycling" produce different recommendations from the same supplier.

The process window your line can actually give

The second half of the enquiry is not about the joint at all. It is about the factory.

• Cure schedule available. Time and temperature you can actually run, and the ceiling set by the most heat-sensitive component in the assembly — often the voice-coil former's own adhesive coating, or the cone. If your ceiling is 80 °C for 20 minutes, say that. It eliminates half the catalogue before anyone wastes a week.
• Takt time. Seconds per unit at the station, and how long the part can sit before the next operation. This sets required fixture time, which is a completely different number from full cure.
• Open time needed. How long between dispensing and mating, in the worst case, including a supervisor walking over to look at something.
• Dispensing method. Hand syringe, needle valve, time-pressure dispenser, screen, roller, brush. This sets the viscosity and thixotropy window more tightly than anything else in the enquiry, and it is the field most often omitted.
• Bond line geometry. Gap, fillet, overlap area, whether the joint is clamped. Two-part systems with fillers have a minimum practical gap; a zero-gap joint eliminates them.
• Line environment. Ambient temperature and relative humidity ranges. This matters enormously for waterborne systems, where the drying rate is the process, and for moisture-cure chemistry, where humidity is a reactant.
• Volume and packaging. Annual volume, order frequency, and the pack format your dispensing equipment takes.

The reason for all of this is that a supplier can usually solve any one constraint and rarely all of them at once. Told the constraints, they will tell you which to relax. Told nothing, they will send you their most popular grade.

The RFQ field sheet, and what should come back

Fill every row before you send it

Copy this structure. Fill every row, or write "unknown" — "unknown" is a real answer and it tells the supplier where to be careful.

Two of those deserve a note. Material restrictions must be numeric. If a customer specification demands a halogen-free grade, "halogen-free" on its own is a description, not a claim you can check — ask for the test report and the threshold it was measured against. The limits commonly cited in electronics work are the IEC 61249-2-21 figures of 900 ppm chlorine, 900 ppm bromine and 1,500 ppm total halogen; confirm which threshold and which test method any given report is written against rather than assuming. The Aosibo listing offers its centring adhesive in one-part, epoxy and halogen-free versions and says exactly this — that the halogen-free claim is a number and you should ask for the number.

Destination market belongs in the RFQ, not in the shipping conversation. The Aosibo listing names the United States, Canada, the United Kingdom, Germany, France, the Netherlands, Indonesia and the UAE among its stated targets. Four of those sit under EU or UK chemical rules, where obligations attach to the mixture. Whether you or the supplier carries those duties is a commercial term with real cost, and it is cheaper to settle at quotation than after a container is held.

The seven things to ask for in return

Ask for these in the same message. A supplier who returns all of them has told you a great deal about how they operate.

1. A technical data sheet with named test methods and named substrates. A shear strength figure with no test method and no substrate is decoration. Lap shear on metal is commonly reported to ASTM D1002; peel on flexible substrates to ASTM D903 or D1876. What you want is the value on your substrates, which usually means asking whether they will test the parts you send.
2. A safety data sheet, in the destination language, for the actual grade quoted.
3. UN number, proper shipping name, class and packing group for that grade, so your forwarder can price the movement before you commit.
4. Shelf life from date of manufacture and storage temperature, plus what remaining shelf life will be guaranteed on arrival. On cyanoacrylates and two-part systems this matters more than transit time.
5. Price with the unit of measure spelled out, at three volumes. This is where quotes stop being comparable: a minimum stated in "units" is not a quantity until someone says whether a unit is a bottle, a cartridge, a syringe or a kilogram. The Aosibo listing states a 1,000-unit minimum and is explicit that the application does not define the unit — treat that as the normal state of an adhesive quote, not an outlier.
6. Sampling and production lead times in writing, with the day basis stated. The same listing gives 7 for sampling and 15 for production as bare numbers read as days. Working days or calendar days is a two-week difference on a quarter's planning.
7. Batch number and certificate of analysis with the sample, so the sample you test is traceable to something you can reorder.

Then normalise before you compare. Convert every price to cost per bond — grams per joint × price per gram — not price per container. A cheaper drum that lays down a thicker bead is not cheaper. This is the same discipline that explains most of the cases where quotes for the same spec come back far apart: the quotes are answering different questions.

Common questions

Should I send physical substrates, or is a description enough?

Send parts if you can. A description gets you a recommendation; parts get you a test. Twenty cones, twenty surrounds and twenty frames — untouched, in the condition they reach the bonding station — are worth more than any specification you can write, because they carry the contamination you forgot to mention. Ask before shipping whether the supplier will run adhesion testing on buyer-supplied parts and at whose cost; the answer varies and is worth knowing.

Do I really need to disclose my volume in the first message?

Yes, honestly, and send everything in one structured message rather than in fragments — enquiries that arrive in pieces get answered in pieces, and the supplier's engineer never sees the whole joint at once. The general rules for writing a spec sheet for a Chinese factory apply directly. On volume: an underquoted figure gets you sample-quantity pricing you then have to renegotiate, an inflated one gets you a price the supplier withdraws. Give a real annual figure and order frequency, and ask for a price at three volume steps.

The supplier answered with questions instead of a price. Is that a bad sign?

It is the best sign available in this category. The questions to look for are about your substrates, your cure ceiling and your dispensing method. Questions only about quantity and payment terms tell you something else.

The enquiry you can send tomorrow

Put this in one message, with the field sheet above attached as a table:

• The joint, named, with both substrates by material, grade and finish.
• The surface preparation you actually perform, and the contamination you know is there.
• Bond geometry, and whether the joint is clamped.
• Your cure ceiling, your takt, your required fixture time and your open time.
• Dispensing method and pack format your equipment accepts.
• Line ambient temperature and humidity; product service conditions and expected life.
• Any numeric material restriction, with the threshold and test method you need proved.
• Destination market, annual volume, order frequency.
• The failure mode you are trying to prevent, if you have one.
• The request list: TDS with test methods, SDS, UN number and packing group, shelf life from date of manufacture, price with unit of measure at three volumes, lead times with the day basis stated, sample with batch number.

Aosibo Adhesives is a reasonable place to see what a specialist enquiry looks like in practice, because its own listing asks for precisely this — both substrates, the bond you are trying to make, the cure window and the destination market, together with a request for the safety data sheet, the UN number and packing group and the shelf life from date of manufacture. Send that supplier, or any adhesive house, an enquiry built this way and the quote you get back is a technical answer rather than a catalogue page. Then run the samples as a planned test, not an impression — the general sample process discipline applies here with one addition: write down what "pass" means before the parcel arrives.