Tweeter

This mechanical movement resembles the waveform of the electronic signal supplied from the amplifier's output to the voice coil.

Among the challenges in tweeter design and manufacture are: providing adequate damping, to stop the dome's motion rapidly when the signal ends; ensuring suspension linearity, allowing high output at the low end of its frequency range; ensuring freedom from contact with the magnet assembly, keeping the dome centered as it moves; and providing adequate power handling without adding excessive mass.

Nowadays other metals such as aluminium, titanium, magnesium, and beryllium, as well as various alloys thereof, are used, being both light and stiff but having low damping; their resonant modes occur above 20 kHz.

Polyethylene terephthalate film and woven silk suffer less ringing, but are not nearly as stiff, which can limit their very high frequency output.

A wide range of viscosity and magnetic density variants allow designers to add damping, cooling, or both.

If a tweeter has been subjected to elevated power levels, some thickening of the ferrofluid occurs, as a portion of the carrier liquid evaporates.

Key design requirement differences are: mountings built for repeated shipping and handling, drivers often mounted to horn structures to provide for higher sound levels and greater control of sound dispersion, and more robust voice coils to withstand the higher power levels typically encountered.

Various materials are used in the construction of compression driver diaphragms including titanium, aluminium, phenolic impregnated fabric, polyimide and PET film, each having its own characteristics.

The diaphragm is glued to a voice coil former, typically made from a different material from the dome, since it must cope with heat without tearing or significant dimensional change.

The suspension may be a continuation of the diaphragm and is glued to a mounting ring, which may fit into a groove, over locating pins, or be fastened with machine screws.

Cone tweeters today are often relatively cheap, but many of those in the past were of high quality, such as those made by Audax/Polydax, Bozak, CTS, JBL, Tonegen and SEAS.

Many designers therefore believed this made them a good match to cone midranges and woofers, allowing for superb stereo imaging.

Speakers with cone tweeters offered the best stereo imaging when positioned in the room's corners, a common practice in the 1950s, 1960s and early 1970s.

Cone tweeters are now rarely used in modern hi-fi usage and are routinely seen in low cost applications such as factory car speakers, compact stereo systems, and boom boxes.

Some boutique speaker manufacturers recently have returned to high-end cone tweeters, especially recreations of CTS phenolic ring models, to create a vintage-sounding product.

[citation needed] A ribbon tweeter uses a very thin diaphragm (often of aluminum, or perhaps metalized plastic film) that supports a planar coil frequently made by deposition of aluminium vapor, suspended in a powerful magnetic field (typically provided by neodymium magnets) to reproduce high frequencies.

But higher power versions of ribbon tweeters are becoming common in large-scale sound reinforcement line array systems, which can serve audiences of thousands.

Usually a thin piece of PET film or plastic with a voice coil wire running numerous times vertically on the material is used.

When an audio signal is applied to the primary of the transformer, the stators are electrically driven 180 degrees out of phase, alternately attracting and repelling the diaphragm.

An uncommon way of driving an electrostatic speaker without a transformer is to connect the plates of a push-pull vacuum tube amplifier directly to the stators, and the high voltage supply between the diaphragm and ground.

They are capable of considerable output levels and are rather more sturdy than electrostatics or ribbons, but have similar low-mass moving elements.

Most of the current AMT drivers in use today are similar in efficiency and frequency response to the original Oskar Heil designs of the 1970s.

They can be more complex than other tweeters (plasma generation is not required in other types), but offer the advantage that the moving mass is optimally low - if not relatively massless and so very responsive to the signal input.

One disadvantage is that the plasma arc can produce ozone and NOx, poison gases, in small quantities as a by-product.

In the past, the dominant manufacturer in the US was DuKane near St Louis, who made the Ionovac; also sold in a UK variant as the Ionophone.

In the 1980s, the Plasmatronics speaker also used a plasma tweeter, though the manufacturer did not stay in business very long and very few of these complex units were sold.