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Simulation of acoustic transmission line speaker　[ATL-Speaker] [編集]

2012/1/8

Simulation of ATL-Speaker

Fig.1

Outline
This time, the simulation of "Acoustic Transmission Line speaker (henceforth ATL-Speaker)" which is one of the resonance tube speakers was carried out.
This system has an inverted shape with folded horn. Back cavity is connected to the horn with no throat.
I do not understand clearly the technique of narrowing down horn toward the last part.
However, it thought that the design of ATL-Speaker was on the extension of the resonance tube made last time, and I was the design of the ATL-Speaker.
The image of ATL-Speaker is a resonance tube of reverse horn.
Three sorts of ATL-Speaker /Tapered-Quarter-Wave-Tube(TQWT)/Back-Loaded-Horn (BLH) are considered to be the speaker which belongs to the comparatively near category by the system which loads back pressure directly and earns low-pass.
For this reason, it is unavoidable that form is also alike.
Although this basic design was ATL-Speaker, there is no intention of making the dead copy, the value of ”a~g” was changed, and Fig.1 was written from the simulation result.

Simulation　of　ATL-Speaker
A clear result was not able to be obtained in the last simulation, it carried out in order to find outline.
The program has always used "speaker design your own program," was calculated, assuming unit FE108eσ.
The simulation program can be used as a parameter the amount of damping material.
Normally placed damping material on the left and put the results show a lot of damping material on the right.

(1) Full length operates as a resonance tube with taper.
　　　L=170cm r1=9.0cm r2=4.2cm

If the resonance length A + B, will be calculated λ / 4 is about 50Hz.
Although extended to 35 Hz also by the result of "The design program for its original work speakers", a sound pressure level is as low as 8db.

(2) B-tube resonates independently.
　　　L=70cm r1=5.5cm r2=4.2cm

λ / 4 of 70cm tube is 121Hz.
The resonance tube as a single "speaker design your own program," The results of the phase reversal is seen at 350Hz and 100Hz.

(3) From the simulation
Composite resonator speaker (CRTS1) to infer from the simulation of (1) to (2), ATL-Speaker at low frequency will fall gradually.
However, a little at the front of the mouth may earn low frequency. On the other hand, will inevitably increase the amount of sound-damping material for high-frequency leakage.
Simulation of low-frequency wave, close to the speaker (tube A) a lot of acoustic material, and also the outlet (tube B) is better and feel less absorbing material.

Design of ATL-Speaker
ATL-speaker is assumed reverse exponential in this calculation.
Folded portion of AB (d) is taken as greater than the calculated 5mm.

Fitting of numeric data

ATL-speaker Graph

Specifications of ATL-Speaker
Acoustic transmission line speaker specifications
Rendering type resonator was a tall boy speaker in Fig.1.
Board thickness：12mm
Size：16.4cm wide (lower plate: 24.0cm)
Depth：26.0cm (lower panel: 31.0cm)
Height：1.0m
Inside dimension：14.0cm width
　　　　　　　　　a = 18.0cm , b = 14.8cm, c = 8.0cm, d = 8.5cm,
　　　　　　　　　e = 6.8cm, f = 4.0cm, g=4.0cm
Tube length：1.7m
Folded time： Once
Target bass ： 50Hz
Speaker Unit Available
　　　　　　：FE103-En-S, Fe108Eσ, FE108S, FE88ES-R, etc.

Reference WEB
Acoustic transmission line（Wikipedia）
http://en.wikipedia.org/wiki/Acoustic_transmission_line

The design program for its original work speakers
http://www.asahi-net.or.jp/~ab6s-med/NORTH/SP/index.htm