KAMAKURA

　Introduction

　　FE103 is a really good speaker when we don't care about defect of
low frequency, especially when we listen to female chorus or acapella flute.
　Because they have no low-frequency spectrum.

　　 But is it possible to design hi-fi vented system for this unit which has
extreme low Qo?


　　Frequency response at plane baffle ( data by T.Nagaoka)


　　The response at 64Hz is low by -23dB from the response at middle
range. So if fd is 64 Hz the port resonance system will hardly contribute
to acoustic radiation.

　　　Frequency response (1m)
　　

　　This is the frequency response level of BS-3 by T.Nagaoka. This may be
an unsuccessful work because the level from 100 to 300 Hz is very important
to popular music.

　　Look at these systems.

FE103 periscope


　　fd=90Hz with current positive feedback and low boost.

　 This time I'm going to make a small sized vented system(Helmholz resonator)
and try a fine tuning.

　　In bare FE103 fo is 80Hz but in a box foc increses to 120-150Hz.
The cone is light but it is suspended by an ultra high compliance edge.
　This is the reason why FE103 describes fine tone and has long decay.

　　Playing pioneer 8cm and FE103 simultaneusly suggests some knowledge
　that FE103 speaks "shaka-shaka" and plays electric bass well, and
bass drum is heard from pioneer 8cm. It is heard "pata-pata" from FE103.
　FE103 clips early because of its high compliance and make sound of paper.
FE103 can discriminate the quality of amplifier well, so if the quality of
amplifier is not so good, its fact reveals.
　　Thus FE103 is truly not for general use, but for mania who owns high
quality amplifier and sources.

　　
　　Though this is a virgin unit, fo=86Hz.




　duct length=6cm


　　foc1=180Hz、fd=110Hz This is ordinary data.



　　Resonance by Pon-tataki method


　　fo1=183Hz, fd=90Hz
　　In this case fd is lower than that of pioneer's 8cm but this may be a
critical point.

　　Here I'm looking back　the enclosures of FE103.

　　FE103 periscope seems to have long duct and small cabinet for its balance.
I think this enclosure is orthodoxy.

　　Test discs for FE103 are

　　　Steve Reich "Electric counterpoint"
　 　 Handbell clover friends "tone"
　　　Yumi Arai "Cobalt hour"

　　These discs reveal transient characteristics of the system. Especially Kanzen
amp plays roll as an oral exiter, it's good for ultrasonic voice of Yumin.

　Ultimate drive by Kanzen amp III



　Enclosures were finished with Japanese vanish Kamakura Red. After they
were dried for long time, I listened to them in my reference system.
Amplifier was Knzen amp III which out put impedance is reduced from
8.28ohm(Kanzen amp) to 5.7ohm by means of current positive feedback.

　　In an article Mr.Matsumoto saids current PFB MFB has a problem of
current distortion, so adquate level of current PFB is desirable. Kanzen
amp III has an adquate current PFB.

　　Hearing test
　I listened to Cindy Lauper, Steely Dan, Manhattan Tranfer on it. I felt
massiveness and high-speed bass. Quality of mid-high range is by far
superior to maker's products. This may be a masterpiece.

　　　　(November 22, 2000)