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The 9×4.5mm SMD Magnetic Passive Buzzerfamily brings together three electromagnetic passive buzzers in a 9.0 mm circular SMD package with a 4.5 mm cavity height, the deepest in MEIDI’s 9 mm range. Two standard coil resistances cover 3.6 V and 5 V rails, while an F‑16R variant adds a copper ring to the magnetic circuit for greater acoustic efficiency at the same drive level. The common 2700 Hz resonance cuts through low‑frequency machinery noise, and the black LCP housing is compatible with lead‑free reflow soldering.
Circular 9.0 mm diameter with 4.5 mm profile — tallest cavity in the 9.0 mm series for maximum low-frequency resonance efficiency
Triple configuration: dual-impedance standard models (16Ω / 32Ω) plus copper-ring enhanced variant (F-16R) for elevated magnetic flux density
Low-frequency 2700 ± 300 Hz resonance — superior ambient noise penetration versus 4 kHz alternatives
16R: 3.6V rated, 2.5–4.5V range, ≤80 mA; 32R: 5V rated, 4.5–6.5V range, ≤80 mA; F-16R: copper-ring enhanced magnetic circuit
Extended thermal envelope: -30 °C to +70 °C operating, -40 °C to +85 °C storage
Reflow-compatible black LCP housing: rated for 255 ± 5 °C peak temperature, up to 3 passes
Maximum cavity height in 9.0 mm series: the 4.5 mm profile provides larger internal resonance volume than lower-height alternatives, supporting efficient 2.7 kHz acoustic output.
Triple-configuration flexibility: 16Ω and 32Ω standard variants for voltage architecture selection, plus F-16R copper-ring enhanced model for applications demanding maximum acoustic output from identical footprint.
Copper-ring magnetic enhancement (F-16R): a copper shorting ring in the magnetic circuit improves acoustic output at equivalent drive conditions by reducing eddy current losses.
Low-frequency noise penetration: 2700 Hz resonant centre targets the 2–3 kHz band where industrial ambient noise spectral density diminishes, improving alert perceptibility in heavy machinery and vehicle environments.
Voltage-optimised impedance pairing: 16R for 3.6V Li-ion/logic systems with ≤80 mA draw; 32R for 5V automotive/industrial buses with ≤80 mA draw; F-16R maintains 16Ω impedance with enhanced magnetic circuit for superior output at equivalent power.
Extended cold-weather storage: -40 °C storage rating supports arctic logistics, high-altitude equipment, and winter-stored machinery without parametric degradation.
| Parameter | MLT-9045-16R | MLT-9045-32R | MLT-9045F-16R |
| Product Type | Electromagnetic SMD Passive Buzzer | Electromagnetic SMD Passive Buzzer | Electromagnetic SMD Passive Buzzer |
| Rated Voltage | 3.6 V (o-p) | 5.0 V (o-p) | 3.6 V (o-p) |
| Operating Voltage | 2.5 – 4.5 V (o-p) | 4.5 – 6.5 V (o-p) | 2.5 – 4.5 V (o-p) |
| Sound Output at 10 cm | ≥ 85 dB | ≥ 85 dB | ≥ 85 dB (enhanced) |
| Operating Current | ≤ 80 mA | ≤ 80 mA | ≤ 100 mA |
| Resonant Frequency | 2700 ± 300 Hz | 2700 ± 300 Hz | 2700 ± 300 Hz |
| Coil Resistance | 16 ± 3 Ω | 32 ± 3 Ω | 16 ± 3 Ω |
| Operating Temperature | -30 °C ~ +70 °C | -30 °C ~ +70 °C | -30 °C ~ +70 °C |
| Storage Temperature | -40 °C ~ +85 °C | -40 °C ~ +85 °C | -40 °C ~ +85 °C |
| Dimensions (Dia × H) | 9.0 × 4.5 mm | 9.0 × 4.5 mm | 9.0 × 4.5 mm |
| Weight | 0.8 g | 0.8 g | 0.8 g |
| Housing Material | Black LCP | Black LCP | Black LCP |
| Magnetic Enhancement | Standard | Standard | Copper Ring |
| Soldering Method (Recommended) | Reflow: 255 ± 5 °C, 3 s; Preheat 180 °C, 40–70 s | Reflow: 255 ± 5 °C, 3 s; Preheat 180 °C, 40–70 s | Reflow: 255 ± 5 °C, 3 s; Preheat 180 °C, 40–70 s |
The 9×4.5mm SMD Magnetic Passive Buzzer represents the acoustic apex of MEIDI’s 9.0 mm circular SMD buzzer portfolio. The 4.5 mm profile — tallest in the series — delivers 80% more internal resonance volume than the 2.5 mm MLT-9025 and 12.5% more than the 4.0 mm MLT-8540, translating into superior low-frequency efficiency and sound pressure generation at 2700 Hz.
The triple-configuration architecture addresses three distinct procurement scenarios. The MLT-9045-16R (16 ± 3 Ω, 2.5–4.5V) serves battery-powered and 3.3V logic-based designs where direct GPIO drive feasibility is prioritized. The MLT-9045-32R (32 ± 3 Ω, 4.5–6.5V) targets 5V automotive accessory buses and industrial PLC outputs where higher rail voltage reduces current-induced EMI and conductor losses. The MLT-9045F-16R introduces a copper-ring magnetic enhancement — a conductive shorting ring integrated into the magnetic circuit that suppresses eddy current losses in the pole piece, increasing effective magnetic flux density in the air gap without increasing coil turns or resistance.
The F-16R variant provides enhanced acoustic output compared to the standard 16R at equivalent voltage and current ratings, due to improved magnetic circuit efficiency. For applications where every decibel matters — such as emergency evacuation systems, heavy machinery collision avoidance, or maritime safety alerts — the F-16R provides an upgrade path without revising voltage architecture or PCB layout.
The 0.8 g mass provides mechanical stability under vibration and shock conditions. This stability is critical in mining equipment, agricultural harvesters, and commercial vehicle chassis where sustained vibration would degrade output consistency in lighter transducers. The circular footprint simplifies enclosure acoustic modeling compared to square alternatives, with predictable radial sound radiation patterns that facilitate grille and port design. Request samples of all three variants to evaluate voltage compatibility and magnetic enhancement benefits in your target acoustic environment.
MEIDI applies uniform reliability protocols across all MLT series production. All MLT-9045 variants undergo identical stress verification:
Climatic endurance screening — 48-hour high-temperature storage at +80 ± 2 °C, 48-hour low-temperature storage at -30 ± 2 °C, and 5-cycle thermal shock (-30 °C ↔ +80 °C, 30-minute dwell per extreme)
Mechanical stress validation — sinusoidal vibration (10–55 Hz, 1.0 mm amplitude, XYZ axes, 0.5 hours cumulative) and 75 cm free-fall drop onto 10 mm hardwood (3 impacts)
Humidity resistance verification — 48-hour exposure to 50 ± 5 °C / 90–95% RH followed by 2-hour ambient recovery and full electrical characterization
Soldering integrity confirmation — solder heat resistance at 250 ± 5 °C for 10 ± 0.5 seconds (2.0 mm body-to-solder clearance), plus full reflow profile compliance
These tests are carried out in MEIDI’s own reliability laboratory, which supports the development and validation of all acoustic components produced since 2011. The factory in Jiangsu, China, operates under an ISO 9001‑certified quality system and integrates in‑house LCP moulding, automated coil winding and SMD assembly lines. This vertical integration allows close control over the entire manufacturing chain, from raw material inspection to final acoustic testing.
Sample batch test results demonstrate exceptional consistency across all configurations:
| Variant | SPL Range (dB) | Current Range (mA) | Frequency (Hz) | Impedance (Ω) |
| MLT-9045-16R | 97.5–99.4 | 68.3–71.2 | 2700 (all samples) | 15.2–16.9 |
| MLT-9045-32R | 97.5–99.7 | 61.7–64.8 | 2700 (all samples) | 30.4–32.1 |
| MLT-9045F-16R | 97.5–99.4 | 68.3–71.2 | 2700 (all samples) | 15.2–16.9 |
All parameters tightly clustered within specification windows. Individual batch test reports available upon request.
Heavy industrial alarm systems — emergency stop, crane movement, and press overload alerts in steel mills, foundries, and forging plants where ambient noise exceeds 90 dB and low-frequency penetration is critical
Commercial vehicle cabin and chassis — seatbelt warnings, door-ajar alerts, and reverse proximity tones in heavy trucks, buses, and construction equipment with 24V-to-5V regulated subsystems
Mining and tunneling operations — gas detection, ventilation failure, and evacuation alarms in confined underground spaces with high reverberation and machinery interference
Marine deck and engine room equipment — winch operation, bilge pump, and fire suppression alerts in high-humidity, high-vibration maritime environments
Agricultural processing machinery — grain dryer, silo level, and harvester blockage alerts in dust-laden outdoor conditions with significant background noise
Public address and emergency broadcast — backup audible notification in PA systems, school intercoms, and building evacuation networks requiring reliable tonal consistency
1. What is the difference between the MLT-9045-16R and MLT-9045F-16R?
Both share identical electrical parameters (16 ± 3 Ω, 2.5--4.5V, ≤100 mA) and mechanical dimensions (9.0 × 4.5 mm). The F-16R incorporates a copper shorting ring in the magnetic circuit for improved acoustic output at equivalent drive power. The F-16R is recommended for applications where maximum acoustic output is critical and the modest cost premium is justified by performance requirements.
2. How does the 4.5 mm MLT-9045 compare to the 4.0 mm MLT-8540 and 2.5 mm MLT-9025?
The MLT-9045's 4.5 mm height delivers increased internal resonance volume compared to lower-profile alternatives in the same diameter series, supporting low-frequency efficiency and acoustic output at 2700 Hz. The trade-off is z-axis clearance: the 4.5 mm profile requires more vertical space than slimmer alternatives. Select the MLT-9025 for ultra-slim enclosures, the MLT-8540 for balanced clearance, and the MLT-9045 for maximum acoustic performance where height is not constrained.
3. What drive circuit is recommended for each variant?
The 16R and F-16R at 3.6V draw ≤100 mA and can be driven directly from capable MCU GPIO pins (verify pin current rating ≥100 mA) or through a simple NPN transistor switch with 180 Ω base resistor. The 32R at 5V draws ≤80 mA but requires a driver stage from 3.3V logic; from 5V logic, a 330 Ω base resistor with general-purpose transistor (HF ≥ 200) provides adequate drive. A flyback diode across the coil is mandatory for all variants to protect against inductive kickback.
4. Can the MLT-9045 replace through-hole magnetic buzzers in existing designs?
Yes, with PCB layout revision from through-hole to SMD pads. The 9.0 mm circular footprint occupies less board area than typical 12 mm through-hole buzzers while eliminating drilled holes and manual insertion. Acoustic output (≥85 dB, with empirical data showing 97–99 dB) substantially exceeds many 12 mm through-hole equivalents. The primary design consideration is drive circuit migration: through-hole buzzers often operate at 12V with internal oscillators, while the MLT-9045 requires external 2.7 kHz excitation at 3.6V or 5V. A microcontroller PWM output or simple oscillator replaces the self-oscillating drive.
5. Are custom magnetic enhancements or impedance values available for OEM programs?
Yes. MEIDI supports OEM/ODM customization including alternative copper-ring geometries for specific frequency tuning, intermediate impedance values (20–24 Ω for split-voltage architectures), modified resonant frequencies (2.0–3.5 kHz range), alternative housing colors for visual identification, and custom tape-and-reel packaging. Minimum order quantities and lead times apply. Contact our sales team to discuss specific requirements and request a quotation for custom configurations.
Contact MEIDI for competitive quotations, free engineering samples of all three MLT-9045 variants, and dedicated OEM/ODM support. Our applications team can assist with copper-ring magnetic circuit evaluation, 3.3V/5V drive circuit optimization, and acoustic integration for heavy industrial and vehicle enclosure profiles.
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