Backloaded horn speakers are musical instruments

Prototype No. 2 is a back load horn speaker.

[Motivation]

When I try to make a carpet speaker, I'm interested in the back load horn type speaker, which many people like to build themselves. There are many examples, and I was curious about what kind of sound it would make, so I made my own.

[About the backload horn]

If you look it up on the Internet, the backload horn that comes out as an example is not a pure horn even though it is called a horn. Includes many acoustic maze, resonator tube elements.
It is made of a straight member, and it is folded many times at 180 degrees and 90 degrees to secure the horn length, and many parts parallel to the pipeline are included.
The lower the sound, the better the sound diffracts. Also, if you bend it 180 degrees, the mid-to-high sound is easily absorbed when it is reflected, leaving a low-pitched sound.
In other words, it means that only the bass is extracted by bending. Multiple standing waves should also be generated, and I think that the principle different from the horn is strong in the first place.

In addition, there are many descriptions that the diaphragm can move freely, but as the word "load" suggests, it has an air chamber and a throat, so a certain amount of internal pressure is applied. Even if it's not as much as a bass reflex or a sealed speaker, it should have a higher load than a cylindrical speaker.

Since this time it is a back load horn, I wanted to make the pipe line a horn shape.
The idea I came up with was to use a void tube, which is familiar in architecture, to make it close to a horn shape and compact.

[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, you can make exactly two pairs.
With this, we were able to realize a horn shape that is close to the ideal shape, with no waste in the sound path, and an extremely compact shape.
Then sandwich it between two plates.

There was a gap due to the accuracy problem, but I used the familiar schinori of the design office. It is less thin than wood glue and cheaper than epoxy.
However, since it is not sticky, I used it to fill in the gaps after gluing it with wood glue.

The painting is our standard ink. It is a very cheap and easy paint to apply.

[Speaker units, etc.]

The speaker unit is TangBand W3-881SJ.
I chose it because I liked the extremely thin diaphragm, the powerful neodymium magnet, and the unique shape on the back that seemed to allow the sound to pass through.
And this little unit has more bass than you would expect from its appearance.

Many people are particular about the material, but I imagine that if the horn is firmly adhered to the enclosure, it will play the role of a rib and significantly increase the surface rigidity, so I don't think it matters much. increase.

[Impression of sound]

Now let's turn on the completed speaker.
It sounds good anyway. Speaker efficiency is higher than carpet. (sounds louder at the same volume)
This is of course because the smooth horn shape and no sound-absorbing material transmit sound without loss.
From the horn, not only the bass but also the mid-to-high tones are coming out with a considerable amount of volume.
A carpet speaker cannot reproduce bass to this extent.
However, the female vocals sound small, and the balance is not good enough. Moreover, the sound is too muffled and fluffy.

So I replaced the speaker unit with FOSTEX FE83en.
The mids and highs became clear, and at the same time, the volume of the bass was calm compared to the W3-881SJ.
The throat area is too large according to the calculations in the course for beginners to make their own speakers , and closing the throat halfway seems to be ideal for the crossover frequency.
In addition, since the air chamber has a circular cross section, the sound is reflected repeatedly, which may cause the sound to be muffled, so it is also effective as a countermeasure.
As a result, the sound became clearer, and the volume of the bass decreased a little, but it was enough.

It's a speaker with a very nice sound.
Here, I noticed a grouper. It's an instrument, not a speaker.
If you recall the sounds of conch shells and horn-shaped instruments, it is easy to imagine the tendencies of the sounds.
It makes the sound source resonate louder and creates a feeling of reverberation.
It is no wonder that there are many backload horn fans for its pleasant sound.
However, when listening to English conversation, the voice is muffled and difficult to hear. .

Of course, I think that the speaker I made has too much resonance, but more or less, I think this personality is the fate of a back load horn that has a wide baffle surface and is prone to resonance, resonance, and reverberation inside.
The famous Mr. Tetsuo Nagaoka invented the swan-type backload horn as an answer to a similar problem.
It's a matter of taste, but I think the direction of the backload horn is a little different.