Very nice work RFZ.

The HDT's are now operational. There are only two things left to do with these.
Apply a finish, and LISTEN to them. I think that I will just put the finishing touches
off until another time so that I can get right into the listening part.

These are the remaining construction photo's of the build. I fired these up for the
first time about three hours ago, and I have to say that it was all worth it, as I
am very impressed by the performance of these speakers in every aspect.

The drivers were already broken-in, so they are past that point with very
good sound quality from the start.

And that brings the conclusion for HDT alternate tuning 101.

Ahead comes the evaluation period with a great deal of
listening time to transpire.

As my cables are quite large and heavy, they require
additional strain relief from stressing the terminal connections.
I added a set of dual springs and compression clamps
(ratcheting with quick release) to support the cables with ease.

Here is some data representing our perception to the musical form
and to what degree of range is optimal throughout the frequency spectrum.



This image shows the portion of the auditory region utilized
for typical music sounds.

Some final notes regarding  critical areas of the build.

As should be apparent by what is emphasized in the detailed
photo’s,  One would notice that I kept a keen eye on  all of the
smaller details that contribute significantly to the overall
performance of these speakers.

The sum of the whole equals the summation of all these
special details within their individual attributes.

It is absolutely critical that none of these important details
are to be excluded, as each of these modifications contribute
as mandatory steps to guarantee the performance that this
set of speakers have proven to provide.

The main focus throughout the build is centered around
the importance of decoupling and isolation from the
detrimental effects of vibration within the speaker
elements.

The performance gain is very much like that
of a high-tech turntable design, where no stone remains
unturned to extract every last bit of performance by
countering all of the issues which are known to limit
 maximum potential.

Everything done within this build had a substantial purpose.
To eliminate any of these steps would guarantee a
compromise in performance. I would not have gone to the
trouble of performing any of these modifications had I
been even the slightest bit unsure of the gain benefited
from doing so.

A word about cabinet assembly using screws.
 This is never a good idea.

You will notice that during the construction phase, the top
& bottom plates for the cabinet were prepared with a
pocket-jig to allow for the joining of the panels. This is very
helpful during the glue-up/clamping stage, as this speeds up
the assembly process with a guarantee that joints will be
held in proper alignment with tight holding potential. I also
used evenly spaced screws along the rear panel sides to
provide a stable platform to the outer shell as a base for the
gluing process.  No clamps are needed at the points where
temporary screws have been placed to maintain holding
pressure. From that point, only glue and clamps are used
to assemble the structure.

IMPORTANT: These screws do NOT remain in the cabinet
once the glue has set.

NEVER use nails or screws to permanently build
speaker cabinets. The fasteners will resonate at different
frequencies than the cabinet itself with eventual problems
resulting from the differential. The fasteners are ONLY
used  as an assembly aid.

All temporary screws used for this purpose have been
removed. The holes have been injected with wood glue
to fill them for maximum integrity. None of these screws
ever penetrated any internal points of the cabinet, so
no holes ever gained access for which to compromise
the cabinets internal integrity.

Most of these improvements implemented, were devised
through proven testing by Steve & Bob. Between them and
what my own proven tests have shown with this extensive
tuning package, we know that this works perfectly to the
point of where all maximum potential is extracted from
the DFR-8 based HDT.

The DFR-8 driver comes already treated with the best
possible dampening methods to extract the last bit of
potential from these drivers which are custom tailored
specifically for maximum performance within the HDT
designs. Every possible type of treatment that will make
a difference to these drivers has been applied to them.

Everything from reduced mass of the cones, to the
high-tech tuned phase plugs, to the well dampened
baskets & motor assembly, plus a few other critical
modifications, have transformed this Fostex  driver
into the perfect complement for the single driver HDT
designs with the alternate tuning approach.

One very critical detail that must be conformed to with
great care when installing this driver into the cabinet, is
that of total decoupling from the speaker surface
itself. You do not want cabinet energy transferring back
into the driver under load. This is countered by the
isolation barrier that acts as a shock absorber to dissipate
this detrimental energy before it has a chance to interfere
with the performance quality of the driver. I insured this
through a multi-step decoupling process which guarantees
total isolation from any unwanted energy disturbance.  

First, a thin primary barrier is provided by a properly
conforming gasket, fabricated from cork sheet and
adhered directly to the mounting area of the cabinet
itself. The next two areas of concern focus upon the
actual contact points of the driver where it attaches to
the cabinet. The last thing that you would want is to
have any direct contact between the driver basket
and the cabinet’s surface.

To insure total isolation which will keep everything as it
should be for optimal performance, the first thing is to
apply an adhesion seal made from sticky rope caulk
like that used for installing automotive glass.

This becomes the secondary base barrier which distributes
the load of the basket evenly and firmly to the cabinet
with a positive airtight seal. This acts also as a fully
effective absorption barrier which guarantees the
prevention of  interaction  from vibration.

You will notice that I integrated the rear X-panels which slant
aft of the passives, with a multi-composition acoustic barrier  
extending downward, just low enough to compress against the
upper portion of the port tubes for those chambers. You can
see that the tubes themselves have also been coated with a
dampening material to render them neutral against any
resonating effect that they may contribute without
the dampening.

Turbulent flow throughout these tubes stand a higher degree
of efficiency and stability due to the added stiffness and
absorption control. The direct absorption at the critical entry
points of these tubes created by the multi-composition foam,
acts as a flow regulator for which to guide the flow with less
differential at the port entrance. This flow concept relates to
proven aerodynamic advancements for air foils which interact
much more favorably with some type of  streamlining to the
air flow as it produces an effect upon the surface. This is a bit
like that of a gate control, to insure optimal flow with less
disturbance. This in turn results in increased efficiency.

There is not one single area within this cabinet that has not
undergone some degree of significant treatment which adds to
achieving this high level of enhancement. There is not one area
within the structural composition rendered  void of absolute
isolation, accomplished thru proper de-coupling techniques.

Every possible means to provide positive control and balance
within this structure has been instilled with extreme measure.

Listening evaluations clearly show that these speakers have
dead-on accuracy with stunning speed and ultra smooth
tone. This set of speakers does everything right. So right,
that they excel above and beyond anything that I’ve compared
them to, by a considerable margin across the entire
frequency spectrum.

RTA measurements verify what I hear, and I am not surprised
as to what these measurements reveal.

Three dimensional imaging produced by these speakers
 sets a new standard by which they are in a class of their
own. You can stand close to these speakers and still not be
able to lock on a direct projection of sound from the
speakers themselves. It is as though the sound  emanates
from a perimeter encircling the speakers rather than
actually coming out of them directly. This display of intense
imaging is so Omni -directional and seamless, that the mind
undergoes  an infusion of unique interplay while trying
to grasp the effect.

It takes a design with incredible speed and accuracy to pull
a trick like this off,  and I can tell you through experience
that I’ve yet to hear any contenders that compare on this
level.  Don’t let the box shape fool you. These speakers
may look like ordinary cabinets, but they absolutely sound
 nothing like that which ever came from an enclosed cabinet
design. The cabinets just simply disappear from existence,
as they truly do remain absolutely transparent.


IT IS UTTERLY CRUCIAL THAT A HIGH QUALITY ANALOG
SOURCE IS USED TO UNVEIL THIS DEGREE OF
PEFORMANCE!

DIGITAL WILL NOT PROVIDE THIS
LEVEL BY ANY OBTAINABLE MARGIN!!! PERIOD.

If you are still unfortunate enough to be plagued with the
substandard sound from that of a digital source, I can
guarantee you that the special qualities of this speaker
design will NEVER be exposed until mated with a high
quality amplifier capable of clean, unrestrained power
such as the TORIIMK2 with KT88’s, and a high-end analog
source with premium vinyl recordings.

Then, and ONLY then, will you have the opportunity to
experience what these great speakers really have to
offer!!! I don’t care if anyone believes me or not. This
is a proven fact.

When I switch over from the digital source to that of
vinyl, it is as though I’ve progressed from observing
the outdoors through the window to actually stepping
outside with total adornment by the natural surroundings
that were limited by the view from the window
pane. Everything becomes so alive and rich with
stunning presence that it makes you want to chuck the
digital source directly into the trash!

Digital is an absolute embarrassment to high-end
audio! The only type of source good enough for these
speakers, is that of pure analog when that analog
source is of a caliber worthy of the speakers
potential. The same holds true for the entire system
within the loop. This of course all corresponds to being
placed within an acoustical environment which is
tuned to optimal measures for which to make
the listening experience completely coherent
to the fullest extent.