WHITE NOTES
Speaker Design Integration

This quick-start guide has five of the most common design considerations for integrating speakers.

The percentage of open space to closed space for a grille covering the output of a speaker should be set between 60-65%. Hole diameter will be dependent on the size of the speaker though a typical size of 3mm is recommended. The grille should be designed so as to not have a parallel plane to the speaker face.

Any speaker assembly has the potential to achieve an IP rating if an IP rated mesh is incorporated on the grille. Many speaker diaphragm and surround materials will of themselves achieve an IP rating though water drainage should be considered.

A designer has the option of many chamber types which will offer unique speaker performance. The design can be very complex and involved and only a basic approach will be provided here. The most common and straight forward design types are sealed and aperiodic. For a sealed chamber design, thrice the volume of the speaker should be included into the chamber. Thiele Small parameters can be provided for all speakers at customer request if a more advanced design methodology is desired.

Two mounting environments need to be considered, the speaker to the overall assembly and the chamber to the speaker.

A. Two methodologies can be used to mount the speaker to eliminate vibration either a gasket stack-up or a glue joint. This guide will only discuss the gasket design as this is the preferred methodology for customer application and provides enhanced reliability for a manufacturing environment not designed to produce speaker assemblies.

  • A typical gasket stack-up for the front face of the speaker uses a compressible gasket with a double-sided adhesive and pull tab mounted to the speaker front face. A typical gasket stack-up for the rear face of the speaker uses a compressible gasket mounted either to the speaker magnet or outer rear perimeter.
  • Speaker selection can be made to include screw bosses for mounting to create the needed compression.

B. The same two design concepts applied to the speaker can be applied to mounting the acoustic chamber. The main intent when mounting the chamber is create an air-tight seal along the mounting joint.

COMPRESSABLE GASKET

When designing methodology for wire exiting, the same methodologies employed for the speaker and speaker chamber can be applied. The design will incorporate a slot for the wires to be placed during assembly. The slot must then be air sealed either via a rubber boot placed around the wire, a compressible gasket placed over the slot or a glue joint.

Piezoelectric Elements Overview

This quick-start guide has some of the most common design considerations for integrating piezoelectric elements.

A Piezoelectric Element, or Disk (often called a ’Bender’) is the most basic type of electronic component used to produce sound.

  1. Low power consumption.
  2. Inexpensive.
  3. Used in many electronic products such as consumer, fire, & safety and medical applications.
  4. Typically are round using metallic disk with a layer of ceramic that is ’sandwiched’ by an electrode.

When voltage is applied, the disk vibrates at a given frequency and produces sound. More voltage means a louder disk. The sound can be:

  1. A steady ’Buzz’ or a ’Beep’.
  2. A series of several notes, often called ’Sing-Tones’.

The three basic types of metals used are Brass, Nickel Alloy and Stainless Steel.

1) BRASS is the most common and least expensive.
2) NICKEL ALLOY is used if exposed to high humidity and/or extreme temperatures changes.
3) STAINLESS STEEL withstands contact with harsh chemicals, solvents, salt water, etc.

For a piezoelectric to make sound, it needs to sit atop a housing called a ’Chamber’. If placed on a flat surface, it will not be able to properly flex to produce sound. The chamber (a ’Helmholtz Resonator’) is typically designed to match the resonant frequency of the piezoelectric disk.

  1. Metallic Disk
  2. Ceramic Disk
  3. Chamber
Can be glued to the chamber or come with a peel-off adhesive.
Can have lead wires and a connector.
Can have springs to increase reliability.
Can connect via contact pins on a mating PC board.

The best example of a piezoelectric application is a smoke detector.

Other examples:

Key Finders
Alarm Beacons
Handheld products
POS Terminals
GPS Trackers
Training Collars

Feedback Element

Piezoelectric disks with a third wire, also called ’Self Driven’, have a Feedback Electrode and can be driven with only a transistor and three resistors.

Bi-Morph

A ’Bi-Morph’ Piezoelectric disk has the electrode and ceramic layer on both sides of the metal disk. When pulsed, a ’Push-Pull’ effect is created making the piezoelectric slightly louder.

A piezoelectric disk can also be used as a low-cost switch. When ’stressed’, a piezoelectric disk creates a small amount of voltage that can trigger a microprocessor or microcontroller.

The smaller the piezoelectric, the higher the frequency. The larger the disk, the lower the frequency.

Approximate Ranges:

  • 9mm to 15mm — 6,000 Hz to 9,000 Hz
  • 19mm to 27mm — 3,600 Hz to 5,400 Hz
  • 27mm to 32mm — 2,300 Hz to 3,300 Hz
  • 35mm to 48mm — 1,900 Hz to 2,300 Hz
Sound Transducers Overview

This quick-start guide has some of the most common design considerations for integrating sound transducers.

There are two standard sound transducer types, Piezoelectric and Electromagnetic (’EM’). These transducers are a more robust solution for the customer from a piezo disk.

  1. Like a piezo disk, they need to be driven from a simple PC Board circuit
  2. They are packaged in SMD, Thru-Hole or wire leaded housings.
  3. They are optimized to perform best at specific frequencies.

Piezoelectric sound transducers use a piezo disk. When voltage is applied to the disk, the disk vibrated and makes a sound.

Electromagnetic sound transducers emit sound using magnetic material, a wire and a metal disk. When a current is passed through the wire, the magnetic material interacts with the disk and makes the disk vibrate to make sound.

PIEZOELECTRIC TRANSDUCER
  1. Outer Case
  2. Piezoelectric Device
  3. Internal Wiring
  4. Bottom Case
  5. Termination
ELECTROMAGNETIC TRANSDUCER
  1. Bottom Case
  2. Core
  3. Enameled Wire
  4. Magnet
  5. Diaphragm
  6. Top Case
  1. Low power and acheive as low as 1mA current draw at rated power, often even lower.
  2. Most designs are IP capable.
  3. Will operate at any low-level voltage
  4. Smaller packages can acheive up to 70 dB at 10 cm with rated voltage.
  5. The larger the package size, the lower the output frequency.
  6. Great in harsh environmental conditions.
9 to 17 mm ➭ 3.2 to 4.0 kHz
20 to 26 mm ➭ 4.0 to 5.5 kHz
30 to 65 mm ➭ 1.0 to 4.0 kHz

Most Piezoelectric Transducers are IP capable on the front diaphragm, some even up to IP68. IP67 means the transducer can be submerged into a body of water up to a meter deep for 30 minutes and still operate. IP68 guarantees protection in water up to 3 meters deep also for 30 minutes and still operate. Both IP ratings are dust proof.

Applications are endless! Focus should be on any hand-held / consumer products, medical and industrial devices. Also look at all keypad applications.

Portable WiFi
Handheld Products
Training Collars
Digital Door Locks

Electromagnetic Transducers are used when a design has tight width constraints or low frquency requirements. They consist of eight components that are quite small and are made with highly automated coil winding and assembly equipment.

  1. Upper Housing
  2. Magnetic Plate
  3. Diaphragm
  4. Permanent Magnet
  5. Coil
  6. Yolk Plate
  7. Lower Housing
  8. Terminals
  1. The minimum overall width can be as small as 3.2 x 3.2 mm.
  2. SPL’s range from 68 dB to 95 dB at 10 cm with rated power.
  3. Can acheive louder outputs at lower frequency ranges.
  4. Consume more power when compared to Piezoelectric transducers.
3x3 to 7x7 mm ➭ 1100 to 4000 Hz
8x8 to 12x12 mm ➭ 2100 to 4000 Hz
14x14 to 25x25 mm ➭ 950 to 3200 Hz

Applications are endless! Focus should be on any wall powered device where there is no limit on power, or a product with limited PCB space.

Home Controls
Gaming Consoles
POS Terminals

Most packages can be customized to achieve the desired form factor.

  1. Wire Leaded units can have the wire length, wire guage and connector customized. (All Volumes)
  2. SMD units can have the footprint updated to meet a specific landing pattern. (High Volume Opportunities; Minimum 400K Pieces EAU)
  3. Thru-Hole units can have the pin spacing modified. (High Volume Opportunities; Minimum 250K Pieces EAU)
SMD
Thru-Hole
Wire Leaded with Connector
Finding Safe Harbor for Electronic Audio Components

One of humanities greatest achievements is harnessing the power of aquatic environments for travel, commerce, and luxury. From engine heat indicators to GPS systems, the parameters to design a cutting-edge audio component for harsh aquatic environments requires meticulous calculations, material selection, and rigorous testing. This technical report provides an overview of how Challenge Electronics Engineering Team designs products with nature in mind, resulting in rugged, long lasting, and distinguishable audio components.

Click Here for Technical Report

Practicing Sound Medicine

Whether you are visitor or a medical professional, the incorporation of audio devices is critical for a health center to operate efficiently. From insulin pumps, timed medicine dispenses and cardiac emergency equipment, optimizing the right audio tone into your design will allow medical personnel to respond quicker to the situation. This technical article will outline the benefits of audio signal vs size, the differences in the industry standard signal tones, as well as Challenge Electronics innovative and proprietary sound bending tone, the PinPoint Alert System.

Click Here for Technical Report


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