E-15 Single Driver Enclosure

Banff National Park, AL, Canada (Photo by Yuichi)


PARK Audio DCU-F131W Driver Catalogue Specifications
= Diaphragm Diameter : 13cm
= Diaphragm Material : Multi-layered wood
= Magnet : Ferrite
= Frequency range : 48.6Hz to 20KHz
= Impedance : 6 ohms
= Output : 87 dB/Wm
= Input : 70W (Peak)
= TS Parameters
@Fs : 48.6 Hz, Qts : 0.545, Vas : 9.395 L
This driver has unique multi-layered wooden made diaphragm.
This generates clear with very warm and soft sound.


E-15 Enclosure System Specifications

= Volume : 15 liters
= Size : W 250mm, H 450mm, D 270mm
= Type : Vented
= F(B) : 50Hz
= Frequency range : 50Hz to 10KHz
= Material : Cherry plywoods (21mm thickness) and a Chinese quince
laminated lumber for front decorations
= Finish : Oil based clear polyurethane
= Coloring : Dark oak.

.August 2008 issue, MJ Magazine, Tokyo

Design process


Aging process of the moving components of the driver
When I opened the driver carton, I measured impedance
curves. Red one is in the free air environment and black
one is with 10g added on the diaphragm.
Above is calculated TS parameters at time zero.
Fs=55.4Hz, Qts=0.4877 and Vas=10.74 Liters
After 120min with approx. 1W (RMS) 60Hz sin wave
applied, impedance curves are measured again.
After the aging process the parameters are........
Fs=51.8Hz, Qts=0.4519 and Vas=10.46 Liters.
Using TS parameters including
Fs=51.8Hz, Qts=0.4519 and
Vas=10.4554 Liters, I tried to
obtain optimum low frequency
property by using the Win Speakerz
simulator.


Left curve is the best one which
I obtained. The size of the
enclosure is as follows.

Box Volume: V(B)=15 Liter
BoxFrequency : F(B)=46Hz
Vents Area : S(v)=20cm^2
Vent Length : L(v)=15cm

Above Box Volume V(B) is logical volume,
"Net internal volume" in the window. To
obtain 15 Liters, I have to add some
factors such as the bracing and the vent
volume. Which may be approx. 15+1.4=16.4
litters physical enclosure volume.

On the other hand, I have to subtract
volume due to grass wool filling.
This is a little headaching matter. In this
simulation, we input number as %. The
grass wool filling lower the Q, which means
larger the effective volume.
However in this case, I used 5%.
As a result, both + and - factors cancels
each other. The result is in the "Gross internal Volume" in the system.

Please refer to the E-15 Drawing which is
in the download pages.


Building process

Cutting of 21mm thick
cherry plywood
Four top/bottom plates
and four side plates
Assembly of four pieces
of plates and bracing
Surface polish by a
rotary sander
Making a vent hole by a
5cm hole saw
Front baffle assembly Completed stereo system


Measurements

Frequency response curve Impedance curve
Base frequency response curve (red), 2nd (purple) and
4th (black) harmonic distortion
Base frequency response curve (red), 3rd (purple) and
5th (black) harmonic distortion
There is discussions with regard to super tweeter as a
supplement. When I observe the frequency response
curve, addition of a tweeter looks reasonable. However,
if I listen the music as is condition, this concern
disappeared. Advantage of the single cone performs nicer
sound positioning. This gives more realistic atmosphere
for the listeners, I feel. So, I decided to stay as is.
However, addition of a super tweeter is absolutely one of
options.
To control low frequency distortion, lower then 50Hz input
to the driver must be filtered out. Otherwise it has same
possibility to generates harmonic and / or IM distortions.

The WinSpeakerz simulation software and the Clio
measurement system were used for this craft.
Water fall (Cumulative spectrum analysis)

Enclosure Page...... ......Top Page

Banff National Park, AL, Canada (Photo by Yuichi)