SATOH Hirotaka Architects
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Backload horn speakers are musical instruments


2015.04.07

Back load horn speaker

Prototype 2 is a backload horn speaker.

[Motivation]

When I make a carpet speaker, what I care about is the back-road horn type speaker, which has many self-made people. There are many examples, so I wondered what kind of sound it would be, so I made my own.

[About backload horn]

On the Internet, the backroad horn that appears as an example is not a pure horn, even though it is a horn. Includes many elements of acoustic maze, resonance tube.
It is made of straight members and is folded back many times at 180 and 90 degrees to secure the horn length, and includes many parts parallel to the pipeline.
The sound is diffracted better at lower frequencies. If it is bent to 180 degrees, mid and high frequencies are easily absorbed when reflected, and low frequencies remain.
In other words, it will mean that only the bass will be taken out by bending. There should be several standing waves, and I think that the principle is different from the horn in the first place.

In the streets, it is often stated that the diaphragm can move freely and freely. However, as the word "load" means, it has a configuration with an air chamber and throat, so a certain amount of internal pressure is applied. Even if it's not as good as a bass reflex or a sealed one, it should have more load than a tubular speaker.

This time again, I wanted to make the conduit a horn shape because it was a back load horn.
The idea I came up with was to use a void tube that is familiar in architecture to make it close to a horn shape and compact.

Back load horn speaker

[Void tube spiral]

First cut the void tube in half. Then connect each void tube so that the radius gradually increases.
Since each void tube is halved, just two sets can be made.
The horn shape close to the ideal shape has now been realized, and the sound path is extremely compact with no waste.
After that we sandwich this between two boards.

Back load horn speaker

A gap was inevitably created due to the problem of accuracy, but I use the familiar stinori of the design office. Less slimming than wood bond and less expensive than epoxy.
However, since it is less sticky, it was used to fill the gap after bonding with a woodworking bond.

The painting is our standard ink. Extremely inexpensive and easy to apply paint.

Back load horn speaker

[Speaker unit, etc.]

The speaker unit is W3-881SJ from TangBand.
I loved the terribly thin diaphragm, the powerful neodymium magnet, and the unique shape that the sound seems to come out well on the back.
And this little unit sounds so low that you can hardly imagine it from its appearance.

The material is a part that sticks to many people, but I imagine that if the horn is firmly adhered to the enclosure, it will act as a rib and make the surface rigidity much stronger, so it may not matter much. You.

[Impression of sound]

Finally, sound the completed speaker.
Sounds good anyway. Higher speaker efficiency than carpet. (Sounds loud at the same volume)
This is natural, because it has a smooth horn shape and no sound absorbing material, so it can transmit sound without loss.
From the horn, not only the bass but also the middle and high frequencies are emitted with considerable volume.
The bass cannot be reproduced so far with a carpet speaker.
However, the female vocals seemed to be small, and the balance was not enough. Moreover, the sound is too muffled.

So I replaced the speaker unit with FOSTEX FE83en.
The mid-high range became clear, and at the same time the volume sense of the low range was more calm than that of the W3-881SJ.
Beginner's own speaker lectureAccording to the calculation, the throat area is too large, and the crossover frequency seems to be ideally close to about half, so the sound absorbing material is stuck all around the air chamber and the throat area is adjusted.
In addition, since the air chamber has a circular cross section, the sound is reflected repeatedly, which may cause the sound to be trapped. This is also effective as a countermeasure.
As a result, the sound is clearer and the volume of the bass is slightly reduced but sufficient.

It is a speaker that sounds very beautifully.
Here, I noticed grouper. This is not a speaker but an instrument.
If you remember the sound of the conch shell and the sound of the horn-shaped instrument, you can easily imagine the tendency of the sound.
It makes the sound source louder and creates reverberation.
You can nod that there are many fans of the back load horn with a pleasant sound.
However, when listening to English conversation and other sounds, it is difficult to hear the voice, and you can see that it is quite muffled compared to carpet. .

Of course, I think that the speaker I created has too much resonance, but more or less this personality is the fate of the backload horn, where the baffle surface is wide and resonance, resonance, and reverberation tend to occur inside.
The famous Tetsuo Nagaoka invented the swan-type back load horn, and it may be an answer to the same problem.
It's a matter of taste, but to me the backload horn seems to be a little different.

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