making bass reflex speaker

Japanese/English

Japanese version here.

listmarkintroduction


From the time I made a amp, I was not satisfied with my speaker.
So I decided to make my own speaker.
I'm worried about what I will make after speaker.



listmarkselecting speaker unit


I wanted to make speaker which would sound very deep and grand.
I decided to use only one full range unit.
Full range unit works all band from bass to treble.
It will rapture with natural and grand sound because it isn't composed of multi way speaker.
Multi way speaker can sound all frequency band powerfully because each units work for their parts.
But the laps of each parts spoil the naturalness.
Full range speaker sounds naturally but it is difficult to sound all band powerfully.

Then I chose the size of unit.
small in diameter be poor at bass, be good at treble. 8-10cm
big in diameter be good at bass, be poor at treble. over 16cm
These will be general opinion.
I like deep bass sound, so I wanted big unit.
But it is expensive and needs huge enclosure.
My house is small and I'm a poor person.
So I had to compromize.
As a result, I bought 12cm unit.

I planned to make bass reflex speaker which enabled to be small, so I looked for a unit which was high value of Qo.
FOSTEX FE-127E might be good for me.
I bought two for about $38 a unit.
It is protected from magnetism.
It is easier to sound bass than non-protected one.



Its cone is something retrospective because of its cream color.
I feel luxury.
I heard that it used ES cone which was fine fiber and high density.



It is heavy against its looks.



listmarkdesigning enclosure


There are many kinds of enclosures, such as Plane, Sealed type, Bass reflex, Double bass reflex, Back load phon and Resonance pipe.
Each kinks of enclosures have their own tones.
I chose a Bass feflex type because we can can expect it powerful bass and make it small.



Bass reflex type is like upper figure.
The bass sound are strengthen by its duct.
The frequency which will be strengthen is fixed by its shape.
(This is led by longitudinal waves in Helmholtz theory)
It was difficult for me to calculate, so I used free software "SPED".
But "SPED" is written in Japanese.

The unit is FE-127E, the size of enclosure is perfect size which have been calculated considering my small house.
I shaped it by adjasting by SPED.

I thought it would be difficult to make duct, so I purchased P-76 by FOSTEX.
FOSTEX P-76
two ducts are in it
installation size: 82mm in diameter
orifice size: 76mm in diameter
length: 114mm
about $10


I'm sorry these windows are written in Japanese.








These are the windows of SPED.

(If you click, the figure will expand.)


I designed that 70-100Hz would get to be powerful because FE-127E's Fs(lowerst resonance frequency) was 70Hz and I thought it was even high.
It is recommended that Fs and Fd(resonance frequency of duct) should be the same.

FOSTEX designs that the volume of enclosure of FE-127E is 10 litter.
I designed 16.4 litter and it was larger than FOSTEX did.
The reason for this is that the bigger enclosure will be able to sound more grand.




listmarkodering the wood for enclosure


I wanted to process wood for enclosure, but I didn't have tools and I was likely to fail.
So there was no choice but to oder from a craftsman.
I sended following plan via e-mail.
The plan was this.
It included the wood which I would bridge the speakers and use as desk.
The thickness of the wood was 15mm.

I ordered MDF.
MDF is a wood which crushed woods are gathered.
It is strong and suits for audio.
It is hard to warp.
It costed under $100 including postage.




listmarkcontsructing enclosure


Woods came three weeks later I had ordered.
It is wonderful that a speaker will be made by these fragments.




I respect professional.
I built them temporarily, then it fitted completely.
I was happy to get such nice woods.

I felt that MDF is like paper rather than wood.


Then I bonded them by woodwork bond.
If there is a gap, the efficiency of bass reflex will weaken.
So I put a lot of woodwork bond on it and I wiped lapped bond.



I mobilized all books in my house.



listmarkpainting inside, putting acoustic materials


I selected a 12cm unit, so the hole of wood was small.
Considering this, It would be difficult to put acoustic materials after enclosure was completely built.
So I put them before closing the back.

There are many speakers which are not painted their inside.
The reason for this is that painting inside cost so much.
But I heard that it is admired to be painted because of following reasons.
1: protecting from the insect sprang
2: priventing from the boarding would warp
3: it would be good for resonance
4: experimenting trial paint


I painted gel varnish.
The color was black, it was typical color of inside.
Gel varnish was about $6.



This was an epoch-making vrnish.
I rubbed it using a cloth, then it would finish very evenly and beautifully.





I painted negligently because it was inside.
The points where bond was left looked so dirty.
I had to paint outside enthusiastically.


Then I put acoustic materials.
If there are no something acoustic, standing waves will occure in enclosure and strange sound will go.
There are some kinds of acoustic materials. For example, glass wool, needle felt, micron wool and thermo wool.
The characteristic of Needle felt is warm sound, so I bought it. It costed about $8 per 500*930*10(mm).I purchased two rolls.




If we put them too much, the bass sound will be weaken.
But we should put them to the fellows of each sides in order to remove standing waves.
I put to three sides using double-faced tape.



It has benn gradually becoming like a speaker.



listmarkpainting


I closed the back of enclosure.

Now it was time to paint outside.
Looks mostly depend on painting.

I heard that it is important to polish carefully before painting.
So I polished enclosure whenever I was free, some days later it became mellow.
Of course no bond was lapped on it.

Because my house was united in the black and white, I decided to paint enclosure black.
I wanted to enjoy the grain, but MDF had no grain.
So I sprayed black lacquer on it.



I purchased two lacquers about $2 per a can.




I coverd my balcony with plastic bags, I called it my work place.
It was looked like the scene of murder.

Spray flew beyond expectation, so it would be necessary to prevent for the disaster.

When I sprayed, I was amazed at the sight that MDF suck black lacquer incredibly.

I couldn't make any film of paint on it, though I sprayed 4 times.
I used up three cans of lacqure.
It looked uneven and it stunk of organic medium.
It was as if I had been a gluesniffer.
In addition to this, my balcony was coverd with black snow.


I felt as if there were no tomorrow, I sprayed clear lacqure twice desperately.
Of course it became uneven and looked cheap because I couldn't complete black film of paint.
I had to prepare a fround.


I wanted throuw out everything any more.
But I thought of woods which craftsman cut and money which I paid, I tried again.

There were a lot of gel color varnish, so I rubbed it over enclosure.
I was scared that lacqure would dissolve into gel varnish, but I tried it negligently.




This picture is after painting gel varnish once.
Miracles happened.
It looked nice.
Gel color varnish was Messiah.

I rubbed it three times and filed the enclosure with #1200 sandpaper.

My speaker had a nice polish like piano had.
I was satisfied with it.
I was a happy man.



listmarksetting unit


Now the time to set unit and speaker terminal at last.



Its gold-plating looked cool.
It can recieve banana plug.

I united speaker unit and terminals.
The wire which connected them was SFC-80 by FOSTEX.
It was about two dollers per 1m.




Then I set duct.



I united it with double-faced tape.
Double-faced tape is useful.




Finally making bass reflex speaker was complete.



It was looked like a face of robot.
I like it.

I feel the duct is even larger than that of ideal comparing speaker unit, but it is charming.
It looks like the mouth of carp.



listmarkimpression




Now let's sound it.

I switched on.

My favorite reggae music had effused, but it was terrible, like paper, cheap and lached punch.
I was about to stick my finger into center cap. of the unit

I heard cheap reggae musics thinging about 200 dollers, I could eat many crabs, broiled meats, and other delicious foods.
What was this feeling of fool's errand...

Various things flashed back such as waiting woods arrived, polishing enclosure seriously, spraying lacqure many times and so on.


However, reggae musics got to be powerful gradually spending such a sad time.
I guess this would be so-called "aging" effects.
Human skin needs anti-aging, but speaker needs aging.
Now I expected it got nice.





Deep sound were roared from duct.

As the smell of paint fade out, the sound got more flavorful and deep one.


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