Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

A prelude to the anxiously awaiting PS Audio loudspeaker line.

How electrostatic loudspeakers work

Of all the speaker types we’re going to discuss in these three posts the electrostat is the oddest because it does not employ magnetic fields to move the diaphragm. Instead, it uses static electricity.

An electrostatic speaker consists of a thin flat diaphragm usually consisting of a plastic sheet coated with a conductive material like graphite sandwiched between two electrically conductive grids—also called stators—with a small air gap between the diaphragm and grids.

The grids and diaphragm are charged with high voltage, typically several thousand volts, and when the output of your power amplifier is applied, the center diaphragm is attracted or repulsed from the stators and we hear music.

Electrostatic attraction is nothing new to us. Rub your feet on a dry carpet and watch your hair stand on end or a sweater cling to you. And before you think this electrostatic field is a weak novelty for attracting hair and balloons, consider that it is responsible for the attractive force between the atomic nucleus and electrons that holds atoms together, and the forces between atoms that cause chemicals to bond together. This electric field is basically what holds the physical universe together.

One thing common to electrostatic loudspeaker designs is the use of extremely high voltage. These kilovolts of energy are connected via a transformer, allowing your amplifier to controls thousands of volts of weak energy.

Note the step-up transformer on the left of the drawing. Remembering that transformers haven’t any physical connection between their input and output, transferring energy by magnetic forces only, the input coil safely connects any size power amplifier to the speaker’s high voltage. On the output side of the transformer, a very high voltage is applied, and this is what generates the electric field that eventually moves the speaker’s diaphragm and makes music.

Electrostats can offer a clarity and transparency to the sound unlike just about any other technology. This is because the moving membrane is so incredibly light that transients pass through with little more than a yawn. First-time listeners to an electrostatic loudspeaker generally describe the experience as listing through an opened window.

Though they are quick they are not perfect. Because their diaphragms move so little they require lots of surface area to be efficient and loud. The large surface area causes beaming, which translates in practical terms to a classic phenomenon associated with electrostat’s known as “head in a vice” syndrome. They are definitely one person speakers.

Tomorrow I’ll wrap up this mini-series on speakers offering my opinion on the best of all worlds.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

This is on the technical side, as Paul explains what makes a  speaker driver a “ribbon” type.  This is probably the tweeter in the soon to come PS Audio loudspeaker line.

How a ribbon speaker works

Before we get to today’s subject I wanted to share a discovery. If you have an Amazon Echo (my favorite) or the poorer sounding Google Home, you can listen to my podcast by just asking. If Echo, “Alexa, play Ohms Law Podcast” and she will. If Mrs. Google, “Hey Google, play Ohms Law Podcast”. So far they will only play the latest show. I am hoping to figure out how you can request a specific day or show.

On to our regularly scheduled blog post.

One of the most challenging loudspeakers of all time was the infamous Apogee from the late Jason Bloom. These were full range ribbon speakers that gave pause to just about any amplifier. If you could find one powerful enough to drive the Apogees, ignoring their silly low impedance of 1Ω, you could get some pretty magnificent sound.

Ribbons move air by means of their namesake. The moving ribbon is typically made from very thin and light aluminum foil—a simple strip that is either straight or pleated (a traditional ribbon) or folded (an AMT). The ribbon is held tight on its top and bottom and free to move along its edges. Those edges are surrounded by powerful magnets. Like the voice coil of a conventional driver, power from the amplifier is applied across the metal ribbon, which in turn develops a magnetic field. As we remember, this moving magnetic field opposes and attracts the permanent magnets along the side and thus it moves, pressurizing the air and we hear music.

Here’s a picture of the setup of a ribbon.

The “pole plates” are the magnets. Note the transformer fed by the amplifier. This transformer is needed to eliminate the Apogee problem of low impedance. You see, the ribbon is a very short piece of metal with low resistance. Using a matching transformer raises the impedance to a more acceptable level for power amplifiers.

Years ago one of the most famous ribbon drivers was made by the British company, Decca. Here’s a picture of the actual ribbon used in a Decca tweeter.

The ribbon is the pleated center strip. The top and bottom lugs with holes are where the wires connecting a power amplifier would be soldered to.

The advantage of ribbons is their low mass. Because the ribbon is very thin, typically about the width of a human hair, it is quick to move and thus both transients and higher frequencies are reproduced with speed and alacrity. Ribbons are among our favorites and are likely what we’ll use in the