Thread: Piezobuzzer and Horn Speaker

What is the difference between a normal speaker, piezobuzzer and horn speaker?

A loudspeaker,
or speaker system, is an electroacoustical transducer that converts an electrical Signal into sound. The term loudspeaker can refer to individual transducers
(known as drivers), or to complete systems consisting of an enclosure incorporating one or more drivers and electrical filter components as shown in. Loudspeakers, just as with other electroacoustic transducers, are the most variable elements in an audio system and responsible for the greatest degree of audible dIfferences between sound systems.

To adequately reproduce a wide range of frequencies, most loudspeaker systems require more than one driver, particularly for high sound pressure level or high accuracy. Individual drivers are used to reproduce different frequency ranges. The drivers are named subwoofers(for very low frequencies), " woofers (for low frequencies), mid-range speakers (for middle frequencies), tweeters (for high frequencies) and sometimes per-tweeters (optimised for the highest audible frequencies).

The piezoelectric sound components operate on an innovative principle utilising the natural oscillation of piezoelectric ceramics. These are applied widely in alarms, speakers, telephone ringers, receivers, transmitters or buzzers. You have asked about the normal speakers, piezobuzzers and horn speakers. Therefore we 'are describing both the piezo speakers as well as piezobuzzers for your understanding. Piezoelectric speakers. Piezoelectric speakers are frequently used as beepers in watches and other electronic devices, and sometimes as tweeters in less-expensive speaker systems, such as computer speakers and portable radios. Piezoelectric speakers have several advantages over conveqtional loudspeakers: these are resistant to overloads which would normally destroy most high-frequency drivers, and they can be used without a crossover due to their electrical properties. There are also disadvantages: some ampli¬fiers can oscillate when driving capacitive loads like most piezoelectrics, which results in distortion or damage to the amplifier. Additionally, their frequency response, in most cases, is inferior to that of the other technologies. This is why they are generally used in single-frequency (beeper) or non-critical applications.

Piezoelectric speakers can have extended high-frequency output, and this is useful in some specialised circum stances; for instance, sonar applications in which the piezoelectric variants are used as both the output devices (generating underwater sound) and the input devices (acting as the sensing components of underwater microphones). They have advantages in these applications, not the least of which is simple and solidstate construction which resists the effects of seawater better than, say, a ribbon-based device would.

Piezoelectric buzzers. Piezoelectric buzzers have a piezoelectric crystal mounted on a circular mounting plate as shown in. Supporting struts are integrally formed in the mounting plate by punching strut-shaped portions in the plate and bending these portions such that they are substantially perpendicular to the plate. The struts are positioned on the nodal circle of the transducer so that the vibration of the transducer is not substantially impaired by the mounting arrangement.

An oscillator circuit is connected to provide a potential between the mounting plate and a first electrode positioned on the surface of the crystal opposite the mounting plate. A second electrode, positioned on the surface of the piezoelectric crystal adjacent to the first electrode, provides a feedback signal to the oscillator circuit. The unique buzzer design allows the buzzer com¬ponents to be assembled by a one-step soldering process.

Horn speakers.
Horn speakers are the oldest form of loudspeaker systems, having been used from very early on for cylinder recording players. As shown in Fig. 5, the part of the horn next to the speaker-cone driver is called the throat and the large part farthest away from the speaker cone is called the mouth. These use a shaped waveguide in front of or behind the driver to increase the directivity of the loudspeaker and to transform a small diameter, high-pressure condition at the driver cone surface to a large diameter, low-pressure condition at the mouth of the horn. This increases the sensitivity of the loudspeaker and focuses the sound over a narrower area. The size of the throat, mouth, the length of the horn, as well as the expansion rate along it must be carefully chosen to match the drive to properly provide this transforming function over a range of freqqencies (every horn performs poorly outside its acoustic limits, at both high and low frequencies).

The length and cross-sectional mouth area required to create a bass or sub-bass horn require a long horn.
Horn speakers can also be defined as loudspeakers that use a horn to increase the overall efficiency of the driving element, typically a diaphragm driven by an electromagnet. The horn itself is a passive component and does not amplify the sound from the driving, element as such, but rather improves the coupling efficiency between the speaker driver and the air. The horn can be thought of as an acoustic transformer that provides impedance matching between the relatively dense diaphragm material (typically made of paper or, more recently, more exotic materials such as aluminium, titanium or PET film) and the air.

This is important because the dif¬ference in densities and motional char¬acteristics of the air and the driving element is a mismatch.