Fostex FE208 Sigma dual-cone full range loudspeaker in exponential horn
Used in my living room
Associated equipment: Last updated: December 19, 2012
Van Medevoort PA222 Power Amplifier
Sony ST-S370 FM Tuner
Sony Discman D-171 (Bitstream Portable CD-player)
Homemade MC Phono Preamp (designed by Stan Curtis, published in ETI magazine)
Homemade MD Phono Preamp (Clone of the NAD3020 preamplifier stages)
Sony PS-X3 Turntable (Heavy, Quarz-Controlled Direct Drive)
Audio Technica AT-OC30 MC Cartridge (with Sony step-up transformers)
The design of this horn loudspeaker was published in the German DIY magazine Klang & Ton 1. Each horn contains one Fostex FE 208 Sigma loudspeaker unit.
Efficiency of the horn is 100 dB (1W, 1m), impedance 8 Ohms, and the frequency response is 47 Hz...18 kHz within 3 dB (with correction filter, see the article in Klang & Ton).
Without the correction filter, the midrange is too loud (i.e., not in proportion to the treble and the bass). With filter, the speakers sound surprisingly neutral and very dynamic.
Old analog LPs with rock and folk music are beautifully presented, but the reproduction of classical music is also excellent.
On a good recording, harpsichords and pianos sound like the real thing (due to the strong magnetic field and the resulting speed of the drivers?).
Voices sound natural, and imaging is very good. Not as good as that of the Petite speakers, which really excel in this area, but much better than most multi-way speakers which I have heard.
The speakers can be used with fleapower tube amps. My own SE tube amplifier has an output power of 1.5 Watts per channel.
This is more than sufficient since one can reach sound pressures of > 106 dB (with a pair of speakers).
The Fostex FE208 Sigma can handle a lot of power (34 W rms, 100 W music signal), so one may use larger amplifiers as well.
With a commercial solid-state amplifier (Van Medevoort PA 222, 100 W per channel), one can reach ear-splitting volumes (about 120 dB).
If you want to hear the full potential of these speakers, the listening position is very important. A slight movement of your chair (eight inches back or forth) can make a big difference.
The acoustics of my living room are rather poor - there are some nasty reflections and standing wave modes. I have towed the speakers in, so that they are directed towards the listener.
Speakers and listener are at the corners of an equilateral triangle, and the speaker front is about 1 meter from the back wall.
With some kinds of music and with male voices, the upper bass region can be somewhat emphasized, causing excess warmth.
According to Ulrich Haumann (of the Plasma Tweeter site), this can be cured by putting a piece of felt on the bottom of the horn mouth.
The felt doesn’t need to be fixed or glued – it can be removed when the speakers are not in use.
Although this was not suggested in Klang & Ton, I filled all hollow spaces in the cabinets with dry sand. Of course the speakers are now very heavy (around 60 kilograms per channel).
The advantage of sand filling is that the cabinets are almost completely "dead" in acoustic terms. Only when one hits the center of the back panel, there is a slight resonance.
Since the back panel is near the end of the folded horn, where
sound pressures are relatively low, this panel does not resonate during normal
The speakers are on a very thin layer of felt, without any spikes. Because of their weight, they are very stable.
It is not a good idea to use spikes, since the horn mouth should acoustically couple to the floor to ensure proper reproduction of the bass region of the audio spectrum.
Moreover, spikes will ruin our inlaid floor!
The designer has called these monsters “Jericho horns”. Although this indicates that they are a threat to the fortifications of the goyim, the walls of our house have remained erect, even after many years.
Next, some pictures which were taken during construction. First, the inside of the horn (with six-year old Henk at the side just to show the size).
Then, a picture taken during filling of the empty spaces with sand.
1 Jericho: 100-dB-Exponentialhorn, Klang & Ton 2/96, pp.50-54, 1996.
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Finally, one of the finished speakers. My wife smoothened and painted the cabinets.
The peach color fits the color of the speaker cone which is made from banana fiber.