Fostex fe168e sigma back loaded horn loudspeaker

Back loaded horn closeup Back loaded horn Fostex fe168e sigma

Horn enclosures are difficult to build, but the result is a very natural sounding speaker if built properly. The project is the recommended back loaded horn enclosure from Fostex.

The design can be downloaded from the following link:

link 168ez recommended enclosure



From marktplaats I bought some fe168e sigma's to upgrade my current fe164's in my self-designed tqwt enclosure. The first thing I saw was that it has a way bigger magnet, it weighs a lot more too. Fortunately they fitted in the very slim cabinet. After some listening impressions I concluded that the cabinet did not fit the unit very well. The mid-heights were very present and it lacked deep bass.

Full range

This project uses "full range speakers", this means that there is only one speaker per channel. The main advantage is that the electronics are very simple, there is no crossover. Also, full range speakers are relatively sensitive. The downside is that the enclosure needed is relatively big (okay... they are huge! 110x30x45cm).

Getting the materials

A fellow speaker builder recommended plywood from a firm called Jongeneel ('berken multiplex'), a wood-only company for professionals. I let a carpenter cut all the pieces of wood for me. 47 pieces per speaker as I recall!

The speaker terminals came from Speaker & Co.

I want to finish the speakers with a high gloss high quality laquer, I got it from "Verfkampioen".

Seperate pieces of wood.... Seperate pieces of wood....


Well you have almost 100 pieces of wood which will become 2 pieces! A lot of work and it has to be done accurately too! I started looking at all pieces and ordering them.. and I looked again, measuring all the pieces.

Finally I decided to place all the pieces roughly where they would be placed, so a horn-like object would appear. And I looked again...

Making the speaker hole

I made the speaker hole using many smaller holes (1.5 cm).

Making the speaker hole Making the speaker hole Making the speaker hole

Making internal parts

Seperate piece Putting it together Test assembling Big internal piece All internals

Putting it all together and finish

I finished the speaker using water based laquer. The middle part has 4 red layers, then a dark brown layer. Everything is then finished with 3 layers of transparent laquer. Dampening materials include "vilt" and "BAF".

Internals without sides Finishing the inner part Finishing the inner part Almost finished!

Listening impressions

This is a huge difference compared to the (lot smaller) tqwt enclosure! It sounds much bigger and the mid-heights are not accentuated as before. The bass is very dry, which is a good thing. The very sturdy (and heavy!) enclosure really pays off.

The overall sound is very natural. With some music howevery, the mid-heights are a little too present, imo.. I'll try a different amp and cables soon. The speakers fit acoustic / classic music best, but it will also rock your house too! They really sound good. I felt that the speakers broke in a lot more after installing, which was good for the bottom end.

Youtube video's

To give an impression I've made some video's! Off course this is absolutely not like the real thing, you get the point :)

btw: I used my EL84 PP amp in these movies

Possibly you're also interested in my Fostex FE167e TQWT

Last Updated on Sunday, 04 April 2010 14:16
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