A U D I O... P A P E R
The DNA Horn
by Steve Deckert
If you've ever had the opportunity to listen to a small single driver
horn speaker you may have come away rather impressed with it's speed
but at the same time found it's bass response to be lacking to the
point of needing a sub-woofer, or a room corner, or both to make it
The design goal behind this speaker was to eliminate what I feel is the
main weakness of small horns, which is the lack of bass. Because
of this weakness, many similar sized horns are shoved into corners of a
room to somewhat re-enforce the low end. My experience has always
been that speakers image best when pulled out into a space, away from
walls. I place a high value on a belivably large and deep sound
stage and highly focused imaging. To me, that's a BIG part of the
thrill behind listening to good recordings on a hi-end stereo
system. I would say this is almost impossible to achieve in the
average room when your speakers are placed in the corners. Unless
there is a large opening to an adjacent room between the speakers, your
sound stage depth will be about 3 feet.
So because of this weak bass performance in many small horns we are
forced to sacrifice sound stage depth to get proper bass
performance. OR We are suckered into using a sub-woofer so
we can pull the speakers out into the room more and of course using a
sub-woofer disqualify s a large part of the reason we like a single
crossover-less full range point source in the first place. So
again another compromise from an absolute sense.
So that's the main goal, get real bass out of a small horn.
The sound that comes out of the horn mouth is often garbled or
congested and lacks articulation in many of the horns I've listened
to. When you stick your head at the opening of the horn and
listen to garbled sound, you can't help but think better clarity here
would be better clarity everywhere. So a fair amount of effort
went into the design of the horn flare and how it's coupled to keep
high frequencies that come through the horn flare at some 12 dB down,
clear and more articulate. This is the sound that will be hitting
the wall behind the speaker and is responsible for adding scale and
ambiance to the sound. Without this, the tiny horn speaker would
sound like a tiny speaker, and they do not. So let's get the
ambiance right, and remove the smearing.
Once it was determined what the minimum amount of power was required to
fill a 17 x 24 feet listening space with lofted ceilings ( 6
watts) I decided to make the speaker available with optional SET
amplifiers that are built-in. This presents some challenges in
the resonance control department but the resonant frequencies that
would aggravate an amplifier's clarity of imaging are surprisingly not
in the low bass regions, but rather start around 70Hz and migrate up
past 400 Hz. I can create a viceo-elastic laminated steel plate
for the amplifier that has a resonant frequency below the 70Hz range
and the ability to absorb and turn to heat the higher bands. This
effort combined with the limited SPL possible with only 6 watts will
make this a viable option for people who want to have built in
amplifiers. The vibration that makes it through the tube dampers
could easily be washed by the benefits of having no speaker wire.
That said, most people will prefer a stand alone amplifier which would
make it possible to have more than 6 watts and therefor take the
speaker to higher levels of SPL and excitement, so we expect 90% of
these speakers will be built without amplifiers.
The DECWARE HORN
(C)2011 by Steve Deckert
If we examine all the available 4 inch drivers out there to find ones
with extended high frequency response, a free air resonance below 80
Hz, and an efficiency that will get loud with 3 watts or more, our
choices are quickly narrowed down to the following candidates:
FE103En 4 inch driver by Fostex, used in the examples on this
page. It has an
efficiency of 89dB 1W/1M and an fs of 83Hz. However, it's
response starts rolling off at 200Hz meaning if you want flat bass to
50Hz your horn design will need around 8dB of gain... highly
The off axis response of this driver from 5kHz on up is really
poor. Power limit of this driver is rated at 15 watts.
FE103EZ 4 inch driver by Fostex, steps things up a small notch with
90dB 1W/1M and an fs of 77Hz, yet it has exactly the same bass roll off
as the FE103En and frankly horrible frequency response by
comparison. Too peaky and tipped up to be taken seriously.
It is rated at 8 watts (24 watts max). With it's almost 10dB
peaks in the treble this driver will sound deceptively loud.
FE126En 4 inch driver by Fostex, has the best efficiency at 93dB 1w/1m
with an fs of 83Hz. It's frequency response is similar to the
FE103EZ, but to get 50Hz your horn will need 15dB of gain. So
once again, we've got a loud little driver with weak bass and poor off
axis response. This driver is also rated at 15 watts.
we go for a 5 inch driver, such as the expensive F120A, rated at 89dB
1W/1M we have a 10dB roll off at 10kHz so a tweeter would need to be
used. However it does have the best frequency response of all the
drivers listed so far. Rated power 10 watts.
FX120 is the same basic driver as the F120A but with a different
magnet. The specs are identical as is the frequency response
except that this one gets out to 15kHz before it rolls off. 89dB
1W/1M Rated power 30 watts. This would be the best choice
Fountek driver, also a 5 inch, has an efficiency of 85dB, but good bass
output and extended treble closer to 90dB mark. This would a
problematic driver at best and not efficient enough for our 3 watt
/ This little gem rated at 88dB 1W/1M made by Tang Band with an fs of
45Hz has excellent response out past 20kHz and off axis response is the
best so far. It's under-hung motor design reduces 2nd and 3rd
harmonic distortion. This driver is also conservatively rated and
responds well to the gain structure of the Decware Horn flare making
it's 88dB rating more like 91dB. This is the driver that was
chosen for the Decware Horn.
Handles 30 watts.
No doubt a large part of the appeal with all of these horns is the
and the small driver. However, as shown below, the Decware Horn
is in line size wise to other popular designs but with nearly an octave
Having a performance shootout with the DNA
Horn would be futile. In the world of speaker design the final
measuring stick is performance vs. size. If you can get the same
size cabinet to do twice as much, it's twice as good. Those
who've owned these horns already know how addictive the speed is,
and if you ignore suggestions of corner placement, you also know about
their imaging potential.
Imagine having this size horn with
enough real bass to fool anyone into thinking you have a sub-woofer
on! Of course the bass will sound far superior to a sub-woofer.
Can it really get any better than that?
the approx outside dimensions of the Decware Horn.
view showing optional input plate for power cord and RCA cable
if cabinet is ordered with an internal amplifier.
amplifier placement shown above with tubes sticking out through the
And below the
actual cabinet being built with a radius front for minimal diffraction
(better imaging) and a window at the bottom for the optional amplifier.
In a natural cherry finish, the DECWARE HORN with
optional SET amplifier installed came out like this.
So there you have it. My reasons and motivations for designing
the DNA horn. It's based on my 1994 corner horn
flare design. As many have heard since, it's a design that creates
incredible bass output. The proof is in the listening. A/B
the DNA horn with any similar sized horn and you'll wonder what's wrong
with the similar sized horn.
Decware is a trademark of High Fidelity
Copyright © 1996
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
by Steve Deckert