A U D I O... P A P E R

The DNA Horn

April 2011
by Steve Deckert

Design Goal

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 sound complete.

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. 

Secondary Goal

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:

The 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 frequency response starts rolling off at 200Hz meaning if you want flat bass to 50Hz your horn design will need around 8dB of gain... highly unlikely.  The off axis response of this driver from 5kHz on up is really poor.  Power limit of this driver is rated at 15 watts.

The 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.

The 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.

If 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.

The 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 so far.
This 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 amplifier target.
W5-1880 / 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 small size 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 more bass.

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?

Here are the approx outside dimensions of the Decware Horn.

Rear view showing optional input plate for power cord and RCA cable
if cabinet is ordered with an internal amplifier.

Internal amplifier placement shown above with tubes sticking out through the cabinet.
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.

-Steve Deckert


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