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The Worlds ONLY Full Range Driver with Electromotive High Frequency Control
Delivering amazingly flat response - which means "No Shout!" and more realistic sound!

Imagine your speakers having such extreme speed and top-end detail that cymbals, bells, chimes, xylophones, horns,
instruments, drums and virtually ALL music SOUNDED REAL!  Instead of sounding
real peaky like so many
full range drivers,
the FRX2 just sounds real thanks to the super extended ultra smooth response made possible by
it's electromotive coupling technology and powerful neodymium magnet.

Model FRX

click here 1024px high res image


E x o t i c   F u l l - R a n g e
Single Point-Source Driver  for  Open Baffle Loudspeakers
37Hz ~ 22kHz  response 8 Inch driver /
94 dB 1 watt/meter

a pair


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We hand make these beauties in the USA

Model FRX


These drivers are available ONLY as long as the parts required to build them remain available.  These are constructed with donor drivers that we have no control over.  The donors' could be changed or discontinued at any point so each time we replenish our small inventory it could be the last.  We are hand building these drivers.  This is not a production run.

A 50% non-refundable deposit is taken at the time of ordering.  The balance due will be taken when your speakers ship.  They are guaranteed work perfectly when you receive them and for an additional 5 years against mechanical defects of any kind.  There are no returns accepted.

NOTE:  JULY 2014  We finally completed the 3 year waiting list for these drivers and are now attempting to keep them in stock.  FRX2 drivers are now able to be ordered from this page for the first time ever.  Your pair can ship within a few days of placing your order here.


The FRX2 represents an obsessive effort on my part to perfect the full-range point-source driver
for Open Baffle speakers at a sane cost. While the build quality of this driver will compete with with other brands costing many times the price, I don't believe any of them will hold up sonically because of the side effects of high flux low mass designs. Side effects like the occasional shouty mid-range and forward presentation or ringing that comes with the  tipped up response that is characteristic of these types of drivers. The FRX2 overcomes these side effects with a unique motor assembly that uses electromotive coupling between the amplifier and the voice coil. To my knowledge there is no other single driver in the world with this technology.

I personally hand build these drivers in small batches of 10 pairs at a time.


In the summer of 2011 (right after I released the original FRX) the donor drivers from Dayton become unavailable as Dayton worked to further improve the consistency of their product.  The changes, while subtle, left me little choice but to start over so we now have the second version of the FRX driver, the FRX2. 

By redesigning the tuning load I was able to eliminate the added (foam) surround further enhancing the driver's uncanny speed and gaining an even flatter frequency response.  In addition to the improved electromotive correction, I added DUAL TUNING loads selectable from a tiny switch on the rear of the driver.  This gives your choice of a mellower or more present sound... very much like having two drivers instead of one.  So in the end, perhaps it was a blessing...   I show comparisons in the measurements further down the page.

-Steve Deckert

Model FRX2

Model FRX2


The FRX2 design is about ultra high fidelity with lower powered amplifiers at sane listening levels.  It has limited power coupling around 15 watts or so.  That means power in excess of that amount will be compressed via the FRX2's novel electromotive coupling.  Point being - this is not a party speaker.  It was designed for critical listening using world class gear by audiophiles with golden ears.  It's SPL limitation is like the old QUAD 57 electrostatic speakers and in a proper enclosure/baffle the FRX2 has a similar albeit more dynamic sound. Unlike a panel speaker, the FRX2's high frequency dispersion exceeds most tweeters so off axis listening is superior.  It's higher total Q and 4.5mm x max makes it well suited for open baffle use.


  • High sensitivity/minimal distortion—an ideal match for lower powered amplifiers
  • Electromotive amplifier to voice coil coupling eliminates ringing and stabilizes response
  • Machined motor assembly with optimized neodymium magnet provides tighter control
  • Solid bass performance, thanks to usefully high excursion capability (>4 mm Xmax)
  • Cast frame with under spider venting for excellent cooling and low mechanical noise
  • Narrow spokes eliminate reflections behind the cone for cleaner response
  • Motor shape acts as a rear wave guide to enhance dispersion
  • Parasitic HF cone and carefully engineered phase plug extends on and off-axis response
  • Low-mass copper clad aluminum voice coil increases high frequency response and speed
  • Copper cap and copper ring on pole piece reduce voice coil inductance and distortion
  • Kevlar reinforced paper cone is lightweight yet rigid and well controlled for cleaner bass
  • Hand Built, tuned and tested one at a time for superior attention to detail and overall quality



The varying current entering the FRX2 motor from your amplifier creates a varying magnetic flux in an air gaped grain-oriented silicon steel laminated core via a primary coil winding and thus a magnetic field through a secondary winding is developed.  This varying magnetic field induces a varying electromotive force (EMF) in the secondary winding called mutual induction. Once this secondary winding is properly tuned with a resistive load, AC current is allowed to flow through this air-gaped circuit via the primary and out to the voice coil.  Since the EMF at a given flux density increases with frequency, the secondary (tuning coil) absorbs the artificial rise in response and ringing caused by the high strength motor assemblies used in this type of low mass driver.  Despite appearances, when the tuning load is removed no current can flow to the voice coil. 

This exotic approach to magnetically coupling current from the amplifier to the voice coil is what gives the FRX2 it's uniquely smooth and highly present sound.

This approach works by designing a driver that is over the top in high frequency projection and then offsetting it with electromotive force.  The result is smooth linear response without loosing the hyper speed and insane detail that comes from the overly strong neo magnet.

The FRX2 design also brings significant if not profound improvements to the overall phase angle and sense of timing and pace when compared to normal drivers. I believe it is part of what brings absolutely lucid imaging to the table when a pair of these are used with good tube amplification.


Some have suggested that using a digital EQ in the signal path would yield results just as good and cost a lot less.  I mention this because this represents a typical gross misunderstanding of what the FRX2 really does.

This system is about storing and releasing energy, and modifying feedback traveling from the speaker back into the amplifier.  It works with the amplifier to create a better more synergistic pairing between that amplifier and the loudspeaker.  A digital EQ in the signal path before the amplifier would have no effect on either one. Addressing frequency balance issues or phase angle with a digital EQ is not the same thing and must be considered a completely separate process.


This is the the effect of the electromotive correction.  Blue is without, Green is with.  Despite the Klippel analysis of the original FRX driver where it was claimed there was no difference in frequency response, they were wrong.  The plot below is the FRX2 taken at 1 meter zero degrees (on axis).

transformer effect

To see more clearly what corrections the electromotive coupling is actually making we can simply plot the difference between the two lines and zoom in a bit. (Grid is 1dB per div.)

See we have about 2.5dB of correction just before 2KHz, minor correction until just before 5KHz and then another nice correction at 7KHz.  No capacitors were used in the tuning load.
Of course we are not only electromotively making corrections to the frequency balance, but also the phase reponse.  Below is the same plot as above, but showing the minimum phase response of these corrections.

You can see that 650Hz a nearly 20 degree phase correction, followed by several more throughout the bandwidth of the driver.  Remember, this is not the phase response of the driver, this is the phase corrections being made to the driver relative to the stock donar driver.


The switch on the back of the FRX2 allows you to select from two different tuning loads inside the motor circuit of the driver.  While easy to hear, the difference on paper looks deceptively small.  Here is the FRX2 on axis plot with the switch in both positions.  To the left is green, to the right is red.

To see a little better what the switch does we can take the plot above and show the difference between the two lines as was done in the plot below where we zoomed into 1dB per div.  You can see the additional correction offered by the switch in the left position is less than 1dB.


Tests were performed at a one meter distance using a B&K calibrated microphone.  Below are the gated responses (200Hz to 22KHz) using the FRX2 driver in a
Zen Open Baffle:


FRX2 response at 15 degrees

Listening tests and measurements agree that this driver sounds best at 15 degrees off axis, the frequency response shown above is impressively flat.


FRX2 on axis

The point-blank measurement at 0 degrees isn't bad either and contributes nicely to the overall response of these drivers. 


FRX2 30 degrees off axis

The FRX2 response at 30 degrees off axis.


FRX2 averaged over 30 degrees

And here is the averaged response of all three which gives you a general sense of what the FRX2 will sound like overall from different locations... 


The FRX2 drivers clearly push the limitations of what is possible with a single point source driver.  By that we mean they have extreme speed and top end detail that makes cymbals, bells, chimes, xylophones, horns, stringed instruments sound real.  These drivers set a new benchmark for "in the room" presence.  The bass performance and timbre is spot on and electrifyingly fast and clean with surprising weight and power.

The impulse response of the FRX2 shown below clearly demonstrates how fast this driver is:

FRX Impulse response

"I could care less how they measure...I have a soft spot for hard rock...when it sounds live - and the attack from these speakers combined with their ultra controlled bass made me feel like it was live.  I felt every guitar note and as a drummer myself, I can tell you the drums sound more realistic on these than anything I've heard yet.  Very impressive."

-Dennis Hazen

Think of the FRX2 like a super high performance race car.  The car is designed to perform on a good quality track and does so better than anything else.  However, run it on a poor quality track and the cars very strengths become its weaknesses.  Recording quality is like the track. 

Recording quality is imperative with speakers like these.  The differences between poor recordings and great recordings on most speakers are easy to hear, but on the FRX2 that difference is magnified in two directions... that means the good recordings become great and bad recordings become horrible, thin and distorted.  I would say this magnification effect the FRX2 has is by a factor of at least 4 compared to normal speakers.  Literally, thin recordings will sound like someone removed the bass, yet warm recordings will have low bass with impressive weight, dynamics, and enough power to shake your room.  This is what happens when we design speakers that are fully honest vs. speakers that musically interpret the source... we hear only the recording as it was mixed.  Coloration's in speaker designs are what make all speakers sound different.  The FRX2 has none, so we recommend these drivers to the serious audiophile and experienced Do It Yourselfers who have top notch amplification and source components.

"I replaced my DFR-8S drivers simply because I couldn't see how it could get much better. My favorite part of the DFR8-S was the mid-range and while Steve will probably probably flinch... when I A/B'd the FRX2 against it, the difference was enough to make the mid-range of the DFR-8S sound broken.  It really caught me off guard.  These things are GOOD."

-John Waters


FRX2The FRX2 can be used by itself in an open baffle cabinet design, or used in an open baffle design together with a bass driver as is popular with so many open baffle designs.  In our Zen Open Baffle cabinet, the FRX is a drop in replacement for the original DFR8 or DFR8S drivers. 

Q) If I already own speakers that use Fostex or Lowther based 8 inch drivers will the FRX2 fit the existing cutout?

A) Yes, The only difference will be the screw hole pattern on the FRX2.  It has six screw holes vs. the Fostex and Lowther's four screw holes.

Q) I have Zen Open Baffles with the original DFR-8S drivers, can I install these myself and if I don't like them can I put my original drivers back in?

A) Yes, you can easily remove the original drivers by unhooking the two wires on the back, and removing the 4 screws.  Installing the FRX2 is a matter of having someone hold it in place while you install the 6 new self tapping screws that are included.  Just hook your speaker cables directly into the back of the FRX2 driver.

Q) What does FRX2 stand for?

A) It stands for "Full"-"Range" Project "X" Version 2.

Q) Besides open baffle designs is there anything else this driver will work in?

A) Of course this speaker will also work in infinite baffle applications.  One example is to mount it into the wall just below your projector screen as a center channel for movies.  The articulation and clarity of the FRX2 makes it unrivaled as a center channel speaker in custom home theaters.

And as illustrated below, it is possible to build large conventional cabinets with the FRX2 as well.


For reference both sealed and ported boxes are also modeled below:

Sealed Box volume 16 cubic feet   -3dB = 60Hz   -10dB = 32Hz

Ported Box volume 16 cubic feet  -3dB = 38Hz  - 10dB = 27Hz

94 dB with 1 watt at 1 meter
Response is 38Hz ~ 25kHz
8 ohm nominal impedance
15 watts RMS/30 watts MAX
Dimensions: A: 8.7", B: 7.2", C: 4.0"  D:
1 inch voice coil
machined copper phase guide and shorting ring
5 way machined gold plated binding posts on rear
Shipping weight 15 lbs ea.



7.36 ohms
70 Hz
4.22 mm
94dB 1w/1m
7.4 ohms
72 ohms

as they sound installed in our Zen Open Baffle Loudspeakers

Zen Open Baffle with FRX driver
  We also offer our Zen Open Baffle Loudspeakers with the FRX installed.

The Worlds ONLY Full Range Driver with Electromotive High Frequency Control
Model FRX

click here 1024px high res image


E x o t i c   F u l l - R a n g e
Single Point-Source Driver  for  Open Baffle Loudspeakers
37Hz ~ 22kHz  response 8 Inch driver /
94 dB 1 watt/meter

a pair


View Cart or Check Out

We hand make these beauties in the USA

© 1996 ~ 2014 by High Fidelity Engineering / Steve Deckert / All Rights Reserved