Driver Information

There are a number of Kit and Driver Options available.

The tweeters I build are a direct descendant of the classic EPI "airspring" tweeter designed in the late sixties by Winslow Burhoe. Over the years it has improved, from the introduction of Ferrofluid™ magnetic cooling liquid, to better dome materials, through its use and further development at Genesis Physics, where the aluminum dome version that I have refined was first introduced.

Although this is really just a handful of different physical arrangements of the same tweeter, the various shapes and sizes can be useful.

The smallest, the original PRO 002 M, is great where size is a limiting factor. It is just big enough to allow for solid mounting and sealing to the cabinet face, and the easiest version to install in a constricted area like a car.

The PRO 002 M2 is a bit larger, about 4" in diameter, so not only is it a bit easier to work with when mounting, it can used as an easy upgrade to many, many speakers.

The PRO 002 ME1, 2, 3 and 4 were developed to replace certain EPI and Epicure tweeters. I present them here so you will know they exist, in case they fit a requirement you have.

This tweeter is a remarkable machine. The carefully designed magnet structure is the launching pad for an overlength voice coil to drive the aluminum dome with precise accuracy.

The concave dome allows a smaller diameter voice coil which is then better coupled to any given point on the dome. This concave shape also produces an almost perfect waveform (its main strength), reproducing the original signal with an accuracy that a convex dome never can. This accurate sound is also dispersed widely (its second main strength), down only a few dB at the highest frequencies even at 180 degrees off axis.

The electrical and physical resonances are both well below 1800 Hz, with a smooth frequency response starting around 1800 Hz and extending to 26 kHz. The distortion level is at or below 0.1% when driven with less than ten watts above 2.5 kHz. This gives a sweet, open, uncolored sound that you can really listen into.

The power handling capacity of the tweeter is roughly 40 watts. Remember that the tweeter sees only a small percentage of the total system power. They can comfortably be used in two way systems running up to 200 watts per channel.

With a 10% duty cycle I've seen it take 1000 (clean) watts at about 3 kHz. In spite of having six inches of sound absorbing material held over the face, it was like having a hammer hitting an anvil in the room with us.

The woofers are descended from those in the original EPI 100 and 50 models, which were accorded great esteem when they were new, and still earn the almost reverent respect of their owners to this day. They have small diameter cones to provide good dispersion and transient response, and very low resonances and long excursions for serious bass production.

I build both six and eight inch woofers. The "standard" long throw voice coil, as used in the PRO 001 and the PRO 007, has 3/4" of winding in a gap that is 1/4" tall. The PRO 005 8" has an even longer voice coil, and the PRO 003 6" is a slightly shorter version. Both two ohm woofers have 3/4" long voice coil windings, and are useful for speaker designs that require two drivers.

These woofers are best used in sealed boxes - I think it gives the most pleasing overall response - but they are unique, even a bit odd, in that most of them also perform very well in properly aligned vented systems. The PRO 001, for instance, works well in a sealed box from less than a cubic foot up to two and a half cubic feet, but can also be combined with the PRO 015 passive radiator in a 1.8 cubic foot box. The commercial viability of this design was demonstrated very well by the Genesis 2 and 2+.

Whether you build one of the suggested designs, taking advantage of these drivers' naturally complementary design, or work with one you like in a system of your own concoction, I am sure you will enjoy their ease of use and elegant lack of coloration.

All these woofers are normally built with a polyether foam surround material. Upon request they can also be made with a synthetic butyl rubber surround.

I build three sizes of passive radiator, which I make available to the experimenter who desires to build a vented system without the problems associated with port tubes. Although they can be finished cosmetically to match the woofers (treated cones with felt dust caps attached to the treated surface) this can make it difficult for you to set up the weighting correctly - unless you are building a HUMAN kit in the cabinet volume provided. For the D.I.Y.er working from scratch, it is better to have me ship them with the dustcaps unattached, so when you are done working out your mass loading, you can glue them on yourself.

The dimensions and specifications of each part are listed in their individual files.

These specifications were measured from batches of at least ten of the component in question.

They were broken in with a signal consisting of a varying sine wave sweeping over most of the drivers usable frequency range, at a level creating an excursion of at least 10% of Xmax at some point, for at least 20 hours.

The woofers were measured hanging in open space by a small chain hooked to one of their mounting holes. Tweeter measurements were made with them lying on their back in a flush baffle, on a thick wooden bench about 8 feet from the ceiling.