Exponential Curved Backloaded Horn Speakers

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Backloaded horn speaker has a full-range speaker driver.
A full-range speaker driver is the ideal because it moves a lightweight
diaphragm with strong magnetic circuit.
For example, the drivers Mr.Tetsuo Nagaoka used for his designed
backloaded horn speakers were SPL 96.5dB Qo 0.26; FE-206,
SPL 98dB Qo 0.16; FE-208S and SPL 99dB Qo 0.15; FE-208SS.
However it doesn't play a practical bass if you mount it on the general
enclosures, like closed-box and bass-reflex.
For 2-way speaker, it has a woofer and a tweeter.
The woofer has a heavy diaphragm with weak magnetic circuit for
easier to play the bass. So, its SPL is low.
Therefore, the tweeter has a resistor/attenuator to suit the SPL of the
woofer; it reduces the SPL as speaker system. (see diagram below)
Crossover Network
2-way network 6dB/oct 2-way network 12dB/oct
6dB/oct 12dB/oct
high-pass impedance correction circuit
However you are able to derive a satisfactory bass through the long
horn from back side sound of the full-range speaker driver by back
loaded horn enclosure.
And a full-range speaker driver hasn't crossover network unlike 2-way
or 3-way speakers; it hasn't any circuit elements such as capacitors,
coils and resistors/attenuators. (see diagram above)
So, it expresses the sound source more real and the sound quality is
completely unaffected by the network and the resistors/attenuators.
Consequently, the backloaded horn enclosure is able to derive its full
ability from the ideal speaker driver.
Therefore, backloaded horn enclosure provides big speakers-like bass
and volume level even small speakers.


The design points for backloaded horn enclosure are the cubic capacity
of an air chamber, the cross-sectional area of its throat,
the horn flare rate, the horn length and the horn-opening area.
Fold up the horn and crate it.
principle of backloaded horn
principle of backloaded horn
One of the things it is highly-efficient system.
In other words, it has a high output sound pressure level;
the backloaded horn system is an energy-efficient design.
So it allows the driving by low-power amplifier, too.
Low-power amplifier is good from the point of view of sensitive sound.
It plays the fine sounds because the driver diaphragm can move easily
by backward opening of the speaker driver, like open back type
cabinet. So, it plays the realistic sound with overwhelming high quality
if its sound source is good, but that's not how it works if its sound
source is poor. Therefore, you may have trouble finding a good sound
You might hate the backloaded horn sound, but everyone will be
surprised at the difference between the sound of backloaded horn and
others. Furthermore, you will never believe the magnificent bass, the
powerful sound and the instantaneous force for small-diameter driver.


Reasonably-priced backloaded horn speakers are not many because of
internal complicated structure.
So, many audio nuts made that by oneself.
However, Hasehiro Audio achieved a low price.
Moreover, they succeeded to eliminate right-angled bend from horn
like below MM-161T.
Hasehiro Audio
MM-161T tallboy type
Designed by Tetsuo Nagaoka
D-58 tetsuo nagaoka
D-58 (in the making)
Conventional backloaded horn is a pseudo system such as conical horn
or combination of some straight ducts, like above Nagaoka D-58.
So, the systems don't have an intrinsic backloaded effects.
But Hasehiro backloaded system is exponential curved horn.
Hasehiro backloaded horn that you've known up until now
has changed completely in new backloaded horn speakers.
i.e.,Elimination of a hollow-gray sound by acoustic reflection
     at the folded
places of the horn (standing wave).
Therefore, Hasehiro backloaded horn system is not an indispensable
high SPL speaker drivers.
Dense MDF (Medium-Density Fiberboards) is extremely good
at listening characteristics because of low sympathetic vibration.
conical horn with exponential horn
You can get yearning exponential backloaded horn speakers at last.
Let's be intoxicated by a beautiful curve makes the ultimate back
loaded horn sound.
Backloaded horn system brings out undertone through the long horn from back side sound of the speaker driver.
As a result, backloaded horn system provides big speakers-like
undertone and volume level even small speakers.
Furthermore, Hasehiro backloaded horn is calculation-based design
and exponential curve.
That's exactly the wind instruments.
Exponential curved horn doesn't form strange peak value.
That means it is like open back type cabinet, but it guides undertone to the front through the horn.
So, the efficiency is high and it has a good balance among ranges.
That is one of Hasehiro backloaded horn's advantages.
And Hasehiro backloaded horn system doesn't get back pressure
beyond a certain level.
That means it keeps the balance better relatively under any volume
level because it doesn't have harmful effects on the cone motion.
That is one of Hasehiro backloaded horn's advantages, too.
If you learn the sound of the exponential curved backloaded horn
speaker more, you had better get into the 
"Fresh Voices" next.


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Tetsuo Nagaoka
audio critic
Tetsuo Nagaoka
Tetsuo Nagaoka published the designs as many as 600 kinds of his own speakers in his lifetime.
Particularly, he focused on the backloaded horn speaker design because the audio industry
had the conventional wisdom that "the backloaded horn speaker has a bad sound."
So, he wanted to prove the characteristics and the advantages of the backloaded horn speaker.
In 1980
Tetsuo Nagaoka published the matrix speaker: MX-1.

In 1986
Tetsuo Nagaoka published the point sound source systemed backloaded horn speaker: SWAN.

In 1992
Tetsuo Nagaoka published the point sound source systemed backloaded horn speaker: SUPER-SWAN.

Basic Knowledge Basic Knowledge:
 -Measured data from 253 drivers
 -Q&A for DIY speakers
 -Full list of original speakers by T.Nagaoka
(Japanese book)
Design Drawings #1 Design Drawings #1:
 -Back loaded horns / Matrixes
 -Nondirectional systems / AV systems
 -Separate systems / Ensemble systems
 -Super woofers
(Japanese book)
Design Drawings #2 Design Drawings #2:
 -Bookshelves / -Double bass reflexes
 -Floorstandings / -Wall-mounted systems
(Japanese book)
Publication: Ongaku no tomo sha corp.

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