a Trademark of High Fidelity Engineering Co.
Zen Designed Single Ended Triodes
Model  RL-1.5


From what started out as a wild d.i.y. project in the mad science lab at High Fidelity Engineering Co. aka DECWARE in 1996 - the Radial Loudspeakers are now shipping to enthusiasts around the world! Introduced at the VSAC2001 show, the Radial Loudspeakers were able to demonstrate the holographic properties of our Zen Triode amplifiers in even the most adverse conditions.


    From 38 Hz ~ 3 kHz these speakers disperse sound in a hemisphere that floats above each cabinet.  The energy is evenly dispersed across 360 degrees so wall reflections are already diffused!  This is the same effect of having a room treated on all 4 walls with quadratic theory diffusers!
    From 3kHz on up these speakers using a floating tweeter become a point source with amazing coherency. We found the main flaw in other radial speaker designs is that they try to shoot high frequencies all around the room.  This compounds room acoustic problems and should be avoided.
    The cone of the radial driver weighs only 4 grams.  The suspension is very stiff and driven by a high mass cast frame and motor assembly.  The speed of this driver when compared to conventional box speakers is MORE than apparent.  It will have you shaking your head in disbelief.
    The Radial loudspeakers are easy to drive two-way speakers with a sensitivity of around 93 dB with 1 watt.  This makes them ideal for lower powered amps including some SET (Single Ended Triodes).



    Read the White Paper to find out how it works!  DIRECT vs. REFLECTED ENERGY
    A paper getting into the concept of the radial design that was
    written after the very first prototype in 1997.


    Read the White Paper to find out how it works!  OFFICIAL WHITE PAPER
    A paper documenting features of the production  version
    of the original RL-1.  A good overview. Written in 2001.


    Read the White Paper to find out how it works! EARLY DRIVER DEVELOPMENT
    A paper written during the assembly of the first prototype
    radial driver.  Written in 1996


The Radials have two sets of binding posts - the top set holds a  resistor to attenuate the tweeter.

Pictured above, a mahogany RL-1 cabinet (center) the removable steel grill with an actual feather weight cone sitting on it (left) and the radial driver (right).



    We had a steel die machined to the inside diameter we needed by a large US manufacturer who wrap the die with pulp under high pressure to effect a thickness to within 0.030 of an inch.  These high density cardboard cylinders are then cut to length and sealed inside and out.  Rings are machined out of MDF and installed into each end to receive the driver and base assembly.


    The next step in the main cylinder is the veneering.  We use a rather expensive solid cherry veneer as the default finish.  We do make many other woods available such as walnut, mahogany, maple, birch, and some exotics for custom orders.


    Damping is accomplished by using combinations of different densities of foam inside the cylinder.   Every step of the assembly process is done by hand using jigs for accuracy and consistency.


    The final result is then finished with clear lacquer and allowed to cure for between 1 and 2 weeks.  These enclosures have tremendous strength and are considerably more inert than an equivalent 3/4 MDF cabinet.


    The tweeter is crossed with a high grade polypropylene cap and attenuated by the user via interchangeable resistors installed on the top set of binding posts.  This was done to allow the greatest flexibility in dialing in the tweeter for any given room without the fidelity robbing side effects of an L-Pad. There is no crossover on the Radial Driver.




    Dear Audiophile,

    It is important to understand that there are many things that make the Radial Loudspeakers superior to conventional box and even planar type speakers.

    The Radial Loudspeaker (based on an inverted 4 gram paper cone) is a project that has evolved through well over 100 variations.  It became obvious about half-way through the development why no other manufactures have built one.  It was a problematic concept.  With exhaustive R&D we were able to overcome these obstacles and make the dream a reality.

    How many other inverted cone drivers exist today ... NONE.

    I designed these speakers for serious audiophiles who want something that sounds obviously superior to conventional box speakers. Spoiled by well designed horns and panel speakers I myself have become allergic to the slow & muddy sound of what I used to think were killer audiophile speakers.

    The problem is that both panels and horns require significant setup hassles to get a coherent sound stage. Even when your room acoustics don't prevent success you still have to listen with your head in a vise to get the 3D effect. The radials solve these problems and are my new reference speakers for imaging.  

    - Steve Deckert



Shown on the left, the original RL-1 Radial Loudspeaker

On the right, the RL-2 loudspeaker.


The Radial Loudspeaker for 2005 is a perfect blend of the strong points between the RL-1 and RL-2.  Like the RL-2, the new RL1.5 has an excellent ribbon tweeter.  The biggest difference between the RL-2 and the new RL-1.5 is the cabinet design. The RL-2 cabinet base design has been replaced with a more streamline design similar to the RL-1 but with more mass, heavy cone spikes and a flat passive radiator.  This has a few advantages over the previous models.  The cabinet height is now ideal, where the RL-1 was a touch short, the RL-2 a touch tall.  


The bass response is now ideal, with no need for adjustment.

Like the RL-1 it can be adjusted somewhat by the floor surface it fires against, and the height of the floor spikes.  Like the RL-2, the adjustment range is limited so that the user can not miss-adjust it beyond a nominal range.

The main 8 inch radial driver was redesigned to match the improved transient response of the passive radiator in the cabinet base.  The idea being that they should match.  The closer they match, the closer together in time will be the primary transient and reactionary echo from the passive.  If you look at the impulse response from the RL-1 seen below, since there is only an active driver in an open bottom cabinet there is no reactionary echo, whereas in the RL-2 while still less then 1ms the echo is clearly there.

The RL-2 uses a second woofer passively located in the cabinet base.  The additional peak in this chart shows the shadow of the second driver.

RL-1 and RL-1.5 impulse response

RL-2 impulse response with clearly visible echo from passive driver.


The basic difference between the RL-1 and RL-2 impulse response echo showed up in the speakers overall sense of speed in the bass.  RL-1's were a touch faster then RL-2's.   RL-2's had more weight in the bass.  Now the new RL-1.5's have the speed of RL-1's and the weight of RL-2's.

Since the main driver had to be redesigned with even less moving mass to match the new passive radiator a few opportunities presented themselves. The result was a driver that has an obvious increase in midrange presence over all previous designs and because of the lighter more linear voice coil it enjoys an increase in efficiency and coherency.   When you combine all these things you have a new Radial loudspeaker that sounds so much better then the two previous models we had to discontinue them.  Now if you consider how incredibly good the previous models sounded, this is an amazing accomplishment.  


Copyright 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 by High Fidelity Engineering Co.
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