Easiest cabinet for Fostex FE206en


2010-01-14 9:55 pm
Hello All, I have the oppertunity to get a used pair of Fostex FE206en drivers.

I used to have these drivers in some very elaborate cabinets & the fostex back loaded horn and absolutley loved them.

I am not in a position to have big speakers any more ( wife!) and I cant build anything complex.

Can any one recomend a very simple cabinet for a fostex fe206 please?

I`m not looking for the ultimate & bass extention isnt important - I just need something slim and easy to build that the wife wont hate.

Currently using frugal horn mk3 with 4inch drivers.

I had the same question a year or two ago from a friend and tested a lot of possiblities in simulation and some in real life in mdf (for testing) At the end the only real solution is use them as midtop in a small reflex and use a sub below. It's almost impossible to get below 100Hz on reasonable volume without a backloaded horn with this driver, above a lot is possible.

The cabinet we build was a 12l reflex with a 7cm diameter tube of 6,8cm long as port on the back and an active crossover at 90Hz to a 8" scansepaek subwoofer. The owner uses them as deskspeakers. with the sub at his feet. Amps are a diy 300B set amp and a hypex 400 kit for the subwoofer, crossover is also custom (the owner is an electronic engineer, he build those himself)
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OK, I'll bite as I've a spare minute. Assuming you're running a voltage-source amplifier, you can force it to work; with about 6.8ohm series resistance, max-flat is about 45 litres, Fb of 50Hz, assuming . With a 50mm diameter vent, that's an Lv of about 25mm assuming a cylindrical duct and the box lagged on opposing faces (top, back, one sidewall), 25mm bonded acoustic fibreglass board or a near equivalent (not acoustic foam). You can drop Fb to about 46Hz for a slightly better damped alignment by increasing duct length to 34mm.

For the sake of convenience, you can use the vented box Fostex show on their FE206En (and FE206E) data-sheet; just adjust the vent dimensions and add the damping & series R. Make sure it's a decent power-resistor rated to 50w or parallel, say, 4x 27ohm 10w rated resistors and place in series with the driver, in either the + or - lead; this is AC so it makes no difference. Job-jibbed.

If you want something a bit taller (and appreciating you can't accommodate very large speakers), then a relatively compact semi-MLTL (in Imperial), assuming the same ~6.8ohm series R is applied:
L = 40in
CSA = 99in^2
Zd = 13 31/32in
Zv = 33 15/16in
Dv = 3in
Lv = 2in
Lag opposing faces 1in bonded acoustic fibreglass board or equivalent (again, not acoustic foam)
Fb = 40Hz
F6 = 34Hz [nominal anechoic]

Both the above are assuming the published spec., with a small adjustment to Vas, which doesn't line up if the others are correct. A few words on series R. Yes, it / they will get hot hence it / they needs to be either a dedicated high wattage power resistor, or multiples to get the power handling up & improve heat dissipation. Don't place them in close proximity with either the damping, or the driver for obvious reasons. The 206En was nominally rated at 96dB 1m/2, or just over 97dB 1m/2.83v. The resistance will drop that to around 93dB 1m/2.83v. Note that power-handling on paper is limited as it's a short coil gap & coil, nominal Xmax is 0.8mm. Xmech is much longer though, and Xmax is just a rough & (to put it mildly) rather limited guide to distortion.
….the only real solution is use them as midtop in a small reflex ...
Such a small reflex exists. It does not go low. To do that well you really need a horn.

https://frugal-horn.com/downloads/centre/dFonken206-centre-190118.pdf (now free for personal use)

But sealed to a woofr probably makes more sense.


The vented box does not go much lower ultimately but will have more kick in the upper bass.

Both would XO to the woofers at 110-130 Hz.