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sierra_gva 2nd August 2006 03:46 PM

Enclosures for Fostex FE206 ESR + T90A-EY

Sorry for the newbie questions, but I am trying to make sense of different pieces of information I have collected on the net and on this site regarding enclosures for Fostex FE206 drivers.

I recently received as a gift a pair of Fostex FE206 ESR and T90A -EY and I am trying to find relatively simple enclosures to build so I can use these speakers. I use different type of amps, mosfet and old (rebuild) quadII's. I haven't built any Hifi gear for the last 15 years and I am not very technically oriented.

1) Is the recommended enclosure for the FE206E as presented on the fostex site been tried with the FE206 ESR by someone ?

2) Would there be tested alternative and simple designs one might suggest ? WAF is not an issue.

3) My woodworking skills are somewhat limited. The most complex cabinets I ever built were a onken-mahul design with a set of Focal drivers. This was 15 years ago. Still working and enjoyable.

Kind regards,

DocLorren 2nd August 2006 05:17 PM

I would say that reading from the experience of some diyaudio members, especially No Xo, a noob may probably be best off with the recommended 206ESR enclosure since these drivers seem hard to tame but in the end fare pretty well after plenty of break-in time. For other enclosures expect a LOT of tweaking damping tweaking undamping tweaking redamping,...well you get the point right? It might be a lot of fun to do though.

Scottmoose 2nd August 2006 05:55 PM

Simple to build: look no further than here: and go to the projects section. You'll see the virtual project in there. Do not attempt this design without the circuit though, or you'll end up with 0 bass.

If you want a horn, then I'd go for the Dallas II, which you'll find in the horn gallery section of, or Onur's double horn, which is here:

Both are worth looking into -the latter will need some series resistance though. Bit harder to build, but better than the standard Fostex enclosure.

fred76 3rd August 2006 06:12 AM


I haven't heard the ES-R but If you have 'good' ceiling height you might want to try the BIB enclosure for the 206ES-R. Simpler to build than most other horns...


Scottmoose 3rd August 2006 08:30 AM

Sorry; I mis-read the fact that your drivers are 206ES-R. A gift? Wish someone would give me a pair! (though I was a little disappointed that they have a ferrite magnet, rather than an enlarged version of that wonderful cobalt-lathanum motor the 166ES-R had. Oh well.)

The Dallas II and Onur's horn would both need modifying to get the ES-R working with them, so I'd probably forget those, and go with either the Fostex factory ES-R horn (NOT the standard FE206E version), or the BIB if you have the ability to corner load the thing, or at least a rear wall, and don't mind a very tall enclosure. I've been fooling around with possible alternative horn ideas for this driver on and off as it's really very special, but I haven't finished them yet. Will try to get one completed today & get some suggested dimensions up here.


Scottmoose 3rd August 2006 10:42 AM

2 Attachment(s)
Right, here's one idea for the 206ES-R. It's of the type GM calls a Big Vent Reflex, similar to a Replikon, and is a double horn to reduce the footprint somewhat. I'll leave the exact layout to anyone mad enough to want to build it, as I'm lousy at drawing I'm afraid. It's a bit of a monster too, but I like the potential response. It won't be exactly like this, as the upper mouth will not see the same reflection boundary condition as the lower. Still, there seems some potential here.

Approximate external dimensions assuming 3/4in build material. It'll be about 12.25in wide, 14.25in deep & 75in tall, give or take.
CC is 12in deep, 23.75in tall, 10.75in wide. The horn throats are at the rear of the chamber, exiting in the vertical plane. Each throat =0.2Sd. Each horn is 40in long. Each mouth =8.2Sd. The FR plot assumes the enclosure is unstuffed. A little series resistance will be a good idea -not sure about baffle-step. Thoughts anyone?

Have fun

sierra_gva 3rd August 2006 02:22 PM


Thanks for your very prompt answers. I will probably do the ML-TL or the BIB enclosures before I start to play around with other designs. One of these simpler designs would also allow me to break-in the speaker until I move to more complex designs.

One question about the BIB enclosure you might be able to answer straight away : I have seen on the ZillaSpeak website the characteristics for my specific fostex driver and some formulas to calculate the dimension of the BIB box.

Fostex FE206ES-R
L = (Line length) 161.5"
Zdriver = Driver 32.5" down from sealed end of cabinet
Sm = 139.125"^2

From the drawings, it seems that Zdriver and So is the same variable but under two different names : distance from the center of the driver to the top end of the cabinet ? True ?

From the Sm variable also called terminal area (=width x depth), how do you calculate the other dimensions ?

Do you start by taking a reasonable width for the cabinet that allows you to fix the speaker properly (let's say 12" width) and then calculate the depth (in this case, using Sm=139.125, the depth would be around 11.6") ?

Then from the depth, how do you calculate the other dimensions ? The explanation for the line length is a bit unclear to me.

May be there are some sources of information you might know I could look up ?


Scottmoose 3rd August 2006 03:02 PM


The MLTL will probably need some modifying for the ES-R driver as it's parameters are different to the standard FE206E. If you want me to, I'll come up with one in MathCad for you. However, although it's perfectly possible to use these drivers in resonant TL enclosures, IMO, they're best in some form of horn.

Re the BIB.

The correct term is Zdriver (the 'So' labelling on the lower diagram is wrong, Jeff hasn't had time to change it yet), and you are quite correct: it's the distance of the driver centre from the sealed end of the line.

The WxD dimensions of Sm are an interesting question, as there is some room for experiment here. However, in your case, with ES-Rs, I'd stick as close as practical to the correct conical horn profile, so, rounding the dimensions GM's nifty little spreadhseet provides to the nearest sensible numbers, I'd go for an internal width of 10in, and an internal depth of 14in. Terminate the internal baffle 7in from the front and rear cabinet walls, & the same distance from the cabinet base. Greg and I when we calculate the area of the open end use nominally 'ideal' figures, which are not always practical in the real-world -you can round them to the nearest / easiest figure without audably affecting the response.

The exact height of the enclosure can be calulated using another spreadsheet which calculates the radius of the curve at the bottom of the enclosure. In your case, a box 82in tall, excluding the base, will get you spot-on. I keep meaning to ask Jeff if he could include these on the BIB pages he's hosting as they're useful little tools. An FE206ES-R BIB? That thing will thunder.

Hope that's of use

sapdog 4th August 2006 01:48 AM

FE206ES-R in ML-TL
Well I have some FE207E's in an ML-TL which I like a lot.
However I also have some FE206ES-R's waiting for me to build a cabinet. I was thinking about putting them into the ML-TL this weekend - and tweaking the BSC circuit a bit.

One concern is that I don't think the mounting holes are going to line up - and I would hate to bugger the ML-TL's just because I'm anxious to put the ES-R's to work.

I've been following the various conversations on these drivers across the full range forums - and really the design I want to try is the k-slot loaded horn design of RCA-Fans from the audio asylum. Just because they look so d**m good - and relatively simple to build.

Steve in Vancouver

sierra_gva 4th August 2006 10:10 AM

FE 206 ES-R in BIB

Since you are the official spreadsheet guru, I will go with your calculation for the FE 206 ES-R in the BIB :

In summary, for those who don't want to go through the whole thread, the internal dimensions are:

Total height = 82 inches
Z driver = 32.5 inches
Width = 10 inches
Depth = 14 inches
Distance from the bottom of the inclined panel to front panel, rear panel and base = 7 inches

I would welcome any feedback and experience on the best way to build the cabinet. I was thinking of birch plywood (30 mm thickness +/- 1.25 inches) with just "biscuits" and glue for the vertical and inclined panels and a removable "base box" fixed with screws to the cabinet and filled with a mixture of lead shots and a silicone type compound which - when dry- looks very similar like the sealant you use around your bathtub. I used this before. It has a good density and it is pretty stable with age.

I will look around for some posts on the type of filing you use and where.

But before starting the build, I have to figure out how and where to fix the T90 A-EX. Don't know if this needed at all. Probably better to experiment without it first and see what comes out before drilling the box again.

Greetings from Geneva,

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