Speakers are the most important component in an audio chain. I can’t remember any other component that has influenced my home audio system  as much as speakers did. Speakers disperse the sound waves inside the room interacting with its boundaries and one shouldn’t think about them separately but in conjunction with the particular room.

It is known truth that room acoustic properties and dimensions have certain requirements of speakers. There is also relation between room and speaker volumes that needs to be consider and one of the most common mistakes one could make is to choose speakers that are far to big for the given room.

My back-loaded horn speakers based on Fostex FE 108 Sigma full-range driver in BK 108 enclosure, created by “Art of Sound” in Saarbrücken.
My back-loaded horn speakers based on Fostex FE 108 Sigma full-range driver in BK 108 enclosure, created by “Art of Sound” in Saarbrücken.

The other important thing about speakers is that their fine tuning and adjustment could bring as substantial improvement in the system as no other component tuning could. Alone the fine positioning that involves adjustment of the distances between speakers, speakers and back wall, speakers and listener and finally the toe-in angle could improve the whole system performance manyfold.

By choosing an appropriate speaker cable and tuning the crossovers or notch filters one can gain dramatic improvement. Some type of speakers like mine Fostex BK 108 back-loaded horns allows additionally adjustment of the damping material, both in the compression camera and inside the horn mouth, that could basically bring endless possibilities for fine tonal balance adjustments.

The aforementioned tuning possibilities at the end will affect the frequency response curve of the room that should be as flat as possible. One should not forget also that even a small component change in the system like interconnect cable may require speakers adjustment.

How I got into full-range horn speakers

Before I got into the full-range horn speakers I owned several 2 and 3 way bass reflex speakers. The problem I had with them was that the sound they delivered were not very convincing in terms of realistic portray of the fundamental aspects of music like timbre, tone colour, but also non-musical artefacts like transparency, soundstage and imaging. They have never managed to disappear fully and the illusion of the sound coming from musician’s instruments situated on the imaginary soundstage between them had never happened.

Fostex FE 108 Sigma full range speaker featuring paper cone made of banana plant’s fiber

It was in small Hi-Fi equipment shop in Hamburg when I first time stumbled upon a full-range back-loaded horn speakers. I listened to few relatively big bass reflex boxes first and they made me quite some impression with their deep bass and stringent heights. Towards the end of the session I noticed a pair of small, rather unusual looking speakers, sitting shyly at the corner behind all the others. They were having only one driver each which was one of the smallest full-range drivers produced by Japanese manufacturer Fostex – FE 103. I asked if I can listen to them and the guy tried to persuade me not to because they did not deliver any bass and I would probably be disappointed. But I insisted explaining that realistic and convincing presentation is what I am looking for rather than deep bass. The guy connected them to the amplifier and started some female vocal jazz music, I think it was Diana Krall.

Listening to these small Fostex horns came as quite a revelation. After listening exclusively to box speakers I suddenly realised how coloured the box speakers I had heard were. The horns stripped the boxy colouration away with a wonderfully organic sound. Being a single driver there is no crossover. This means there is no need of splitting the signal to feed each driver with particular bandwidth and eventually no phase shifts caused by the elements crossover consists of. Though the bass was not particularly deep or extended it was fast and clear. At that very moment I knew what type of speakers I would search for.

Fostex FE 108 Sigma drivers in BK 108 enclosure.
Fostex FE 108 Sigma drivers in BK 108 enclosure.

The problem was that such horn speakers are not easy to find in the Hi-Fi shops. They are very popular in Japan but here in Europe one have to build them himself or to find a specialised woodworker to build them. Usually the producer of the speaker broadband driver, in my case Fostex, provides a dedicated enclosure plan for free, so anyone interested in particular loudspeaker design could buy driver and build it himself. Here for example one can see the plan of the recommended back loaded horn type enclosure for my Fostex FE 108 Sigma drivers.

I had neither workshop nor the required skills, so I needed to find a solution. I started researching DIY resources in internet and bought an issue of Hobby HiFi magazine. On the pages of that magazine I became aware of a manufacturer called  Art of Sound based in Saarbrücken, Germany which is specialised in horn loudspeaker construction. I contacted Günter Damde, the owner of the company, and a pair of Fostex BK 108 back-loaded horn loudspeakers was instantly ordered. I waited nearly 2 months until the speakers were completed but since then I enjoy the organic flow of the music as I had never before.

3 thoughts on “Speakers”

  1. That’s a fantastic story and how you came into the full range driver camp. The first commercial full range driver speakers were the moth audio cicada speakers. I have had many drivers before that full range but, I asked the sales guy at the HiFi shop if I could listen to them. I fell in love with the very real micro detailed moth audio speakers. The highs and mid-range was really one of a kind. The bass was to be desired but was there. Never bought a pair. The company went out of business. So a few years later I bought a pair of the fostex Fe 108 sigma drivers used. They sounded great. My favorites were the fe126en drivers and I did a ( A&B) test between the two drivers. The fe126en had a little more bass and the mid-range was good and the highs rolled off. The fe108sigmas drivers beat the fe126en drivers in all areas. The thing I noticed the most was the clearly in voices and top end. The bass was a plumb and well it’s a 4 inch driver. I have never heard then in a horn box just a transmission line. Well thanks for the write up. I might have to get me a pair of drivers and build this box? Cheers Jm

    1. Hey Jm,

      Thanks for the nice feedback and sharing your experiences with single-driver speakers! I think a back-loaded horn can deliver even more drama than transmission line, but it depends on the particular design and the construction quality of course.


      1. Yes I agree a back loaded horn is ones of the best boxes your you can have. Transmission lines never sound right to me in the bass department. Like it added a extra db’s to it. The only Transmission line I like and the only one was meadowlark audio the shearwater speakers.. The hot rod version.. Well thanks for commenting on my post.. Cheers Jeff

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