Cogent True-To-Life Loudspeakers

Cogent True-To-Life Loudspeakers was formed by Steve Schell and Richard Drysdale with a simple, ambitious goal. To build a modern version of the field coil compression driver speaker designs pioneered by RCA in the late 1930's. These designs were never surpassed for sheer quality of musical reproduction.

DS 1428 Field Coil MidRange Compression Loudspeaker

DS 1448 Field Coil Bass Compression Loudspeaker

By employing space age materials (carbon fiber for diaphragms instead of resin impregnated linen, otherwise known as phenolic) and aerospace machining (Electrical Discharge Machining or EDM is used to fabricate the drivers, instead of sand casting) Cogent has succeeded in surpassing the original RCA designs and taking them to another level of performance. Cogent has patents pending on their improvements to the radial slit phase plug design.

Inside view of the patented phase plug of the DS 1428 Loudspeaker

DS 1428 Loudspeaker phase plug as seen from the front

A section of metal removed by the wire EDM machine in making the DS 1428's unique phase plug.

Both Cogent loudspeaker units, the DS 1428 midrange driver, and the DS1448 bass driver, use field coil or electromagnetic motors. These electromagnets were abandoned by the audio industry as soon as permanent magnets could be substituted, for one reason only- cost. In the 1920's and 30's, in the beginning of the motion picture sound era, loudspeaker mechanisms made by RCA, Western Electric, James Lansing, and others were forced to employ expensive electromagnets to obtain the flux density and thus efficiency necessary to produce enough sound for large cinemas out of a few watts of triode power amplification then available. The power supplies for these speakers were also very large, heavy and expensive. With the advent of Alnico, and then ferrite/ceramic magnets, and finally Neodymium and other rare earth materials, the field coil technology was abandoned and then almost forgotten.

Both of these drivers possess magnetic fields on the verge of limits imposed by physics. In other words, they are about as efficient as physically possible. But the real virtue of the field coil technology is not to be found solely in the brute strength of its magnetic field (neodymium magnets can be very powerful, too, for example.) People familiar with the best permanent magnet compression drivers will invariably notice something else in the sound of field coil powered drivers like Cogent, providing they are well designed in the first place. This certain "something" is an almost magical effortlessness, a naturalness that is haunting and not easily forgotten once heard. Much debate has ensued as to the exact technical reason for this superior field coil sound, but the only thing one can say definitively is that, once heard, the sound of such drivers will always be remembered.

Cogent's Steve Schell researched the entire history of field coil driver design, and understood the RCA approach as the ultimate for high quality sound reproduction. His partnership with Richard Drysdale, who has extensive experience with fabrication and machining in the Southern California aerospace and military industries, allowed Cogent to create a line of loudspeakers with technical specifications that exceed the original drivers, now in very short supply and also nearing 70 years in age. These new drivers, represented by the DS 1428 and the DS1448, also break new ground.

The DS1428 is superficially similar to its namesake RCA older sibling, the MI1428B. Both are capable of extending down to 300 hz on the correct horn. The extremely radical and ingenious phase plug of the RCA driver, which was a masterpiece of casting, has been replaced by a larger, more open phase plug (made via wire EDM), which allows much greater high frequency extension, and a more open sound. This new phase plug vents the voice coil diameter (where most of the high frequency energy is concentrated) directly into the horn throat, and provides a higher compression ratio in this region to effect an acoustical equalization of high frequency response. In short, no other driver in the world today is comparable in design or execution to the Cogent DS1428.

DS 1428 Electromagnet detail

All Cogent Loudspeakers use a 12 volt electromagnet, or field coil motor

Cogent supplied 12V cable

The DS1448 does not have any corresponding historical precedent. No such driver ever existed until now. It is the first cone diaphragm field coil bass compression driver ever made-period. Very few people even in the upper echelons of audio have ever heard a bass compression driver. Only a few companies, mainly in Japan, have ever attempted this, as it requires a large horn, and horns, especially bass horns, have been off the audiophile map in the West for 50 years. All such drivers have been permanent magnet. The DS1448 with a nearly 50 pound motor and carbon fiber cone diaphram is capable of producing bass to 60hz on the correct horn that will entirely redefine how one understands the lower octaves. Even the finest paper cone woofers cannot compare to the incredible immediacy of horn loaded bass from this driver.

The horn throat is cast in aluminum alloy, and available in a hand polished version

Views of the DS 1428 Loudspeaker with the AH Horn/Oswaldsmillaudio cast horn throat.

The throat casting is milled to accept a mounting ring that attaches to the DS1428

Oswaldsmillaudio has worked with Bill Woods of AH! Acoustic Horn Company and Cogent to develop horns specifically for Cogent drivers.

The AH300 is a 250hz flare conical horn for use with the DS1428 crossing over at approx. 350hz. This horn is comprised of an aluminum or bronze throat casting and solid, hand made wood horn. Each "petal" is splined to the next with wooden joinery, all done by hand. The horn is available in solid Pennsylvania walnut or cherry. Finish is hand rubbed crystal shellac or oil. Each horn is made to order.

300hz solid walnut horn with polished aluminum throat casting for the DS 1428

Oswaldsmillaudio AH300 hz horn in solid Pennsylvania walnut

Made entirely by hand, shown here with crystal shellac finish

The bass horn for the DS1448 driver is currently being prototyped, but will cover 60hz to the 350hz crossover point with the DS1428 driver and horn. The construction will also be in solid walnut or cherry, with aluminum or bronze castings for the throat section mating to the driver. It will be the aesthetic and acoustic match of the above AH300 horn. This Oswaldsmillaudio horn will be an exclusive design only for use with the Cogent DS 1448 field coil bass compression driver.

Every Cogent driver is made to order, assembled by hand by the two principals. Each is thoroughly tested and listened to before shipment. Please allow six weeks for delivery.

Oswaldsmillaudio is the exclusive East Coast sales agent for Cogent True-To-Life Loudspeakers. Prices available on request.

Photos © Cynthia van Elk