FE206E enclosure

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How much is enough? A question that has puzzled many a human since mastodons called to each other across primeval swamps.
The answer is that there's no simple answer in all honesty. Sorry. However, a few views.

The Fostex horns are good. Very good. Much better than some might lead you to believe. But you're never going to get subterranean bass out of them -figure on about an F3 of 50Hz, with a bit more from room gain, depending on the size of your listening room. The Jerricho horn has also had some good comments, and looks superficially at least a little more attractive (the 206 horn doesn't have the looks of the 208esigma horn IMO) but I suspect the Fostex horn will put out more in the bass regions.

I'd forget reflex-loading with these drivers -the 45l box Fostex recommends is punchy, but has no real bass -reminds me of a pair of Linn Kans with the bonus of not requiring the output power of the Hoover Dam to say boo to a goose. Not much action under 120Hz in room.

Other designs -have a look at Martin King's site for a straight mass-loaded transmission-line using this or the FE207E driver. It won't work as well as the 207E -the 206 needs a heavy dose of contour filtering to bring the top end into line; it's just not as well suited to other cabinets as the 207E. But this is a good one. Probably the best you'll come across, though you'll sacrifice efficiency unless you use active rather than passive equilisation. Not a major issue unless you're running SET amps. This design would be my choice.

One other option for serious bass -bit of a wild-card this: you could try an enlarged version of Terry Cain's BIB TQWT box. Try this as a starting point: height 66", depth 16", width 9 1/2". External dimensions assuming 3/4" build material. Sm = 3Sd . Driver at 42" from the base. Stuff the area above the driver in the first portion of the line, and add a little wadding in the base. Internal sloped baffle ends 7" above base and 7" from inside of the rear baffle. I've kept So = 0 as I suspect the FE206E will need the extra gain. Use the filter from Martin's 206E / 207E MLTL. Frequency response on a sim will not be pretty. In fact, it's downright ugly. But these measure a lot better in room than MathCad predicts -I know, because I've tried it, in response to a challenge from Terry elsewhere, and they did. I had to eat a lot of humble pie. (chomp). Most impressive. I dislike So = 0, but with these drivers, you'll probably need it. Frequency response will have a bit of ripple though. Then again -you said you wanted bass? With these, I'd expect an F3 of about 25 - 30Hz with room gain, depending again on your room size. Deep enough? ;-)
Best
Scott
 
Toni,

I would go for the back loaded horn. Myself I finished monday a Back loaded horn with the FE108E Sigma. Great bass output. And this is only a 10cm driver. I was worried that the bass was to boomy, but that isn´t the case.
An alternative is a TQWT, but the output in the frequentie between 100-500 HZ is less then by a horn, so the mid wil sound to loud. Also you wil need a passive correction filter. Al these components wil give lost of clarety and detail ( or you will have to buy expensive components at almost the price of your units). Myself I never heard a TQWT, they say the base wil sound deeper, but the output is less. For example: a man who had the same horns with the FE108EZ compared those with his new TQWT´s whit the FE167E. The bass was less!!!! Realise that the unit is much bigger!!!
It´s funny because I also considerd building with the FE206E, but I decided for the FE108EZ, because I play in a small room and do not have to play loud. So I went for the most natural sounding unit in mid and high frequenties.
I have a link with another back loaded horn. it is a lot smaller than the fostex desing. If I have to pick a design other then the original Fostex plans, I would build those: http://home.hetnet.nl/~geenius/Solo206.html
Succes with your project

Alexander
 

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Some quick explanations! Sorry about making assuumptions there! (You'll probably know some of these) These are rough & ready comments, but they'll serve as a introductory guide.

F3 is the point below which response (ie volume) from a speaker falls away rapidly.

So is the area of the closed end of a transmission line. Sm is the area of the open end. (or rather, the end which has some form of opening in or near).

Contour filtering: it's a passive set of components -typically an inductor and a resistor that sit between the amplifier and the speaker drive-unit. It serves to smooth the sound by reducing levels in specific parts of the frequency range. Some people panic about putting passive components there; providing it's done properly; it's not a problem and will not corrupt or damage the sound. You won't need expensive 'audio-grade' components either: they're usually (not always) a con with no better (and frequently worse) measured performance over good-quality standard components. It sounds frightening, but really all you need is the two items per speaker: the inductor and resistor, which isn't difficult.

A TQWT is a Tapered Quarter Wave Tube. They're sometimes known as a Voigt Pipe. Have a look here:
http://kosat.consultit.no/~ketil/lowther/voigtpip.html

I'd normally say DO NOT build this design -oddly enough, the FE206E is probably a better match for it as it stands than than any other driver I can think of, including the Lowther's it was supposedly designed for, though it'd need some heavy filtering. I'd still reduce the port area a bit though. A 4" x 4" round port would probably be a start.

The BIB I was referring to in its original form resides here:
http://melhuish.org/audio/DIYTQ8.html
The pictures speak a thousand words. It's a tall rectangular box, open at the top, with a sloping internal baffle that extends from the top of the front panel to just beyond the centre-line of the box, near the bottom. However, you need to modify the dimensions to use the FE206E as the original design shown in the link is for smaller drivers up to about 6" Try the sizes I mentioned in the earlier post -these should be a good starting point; it's dead-easy to build and produces more bass than you'd believe (good quality bass too).

A straight MLTL is a straight Mass-Loaded Transmission Line. it looks like a bass-reflex (i.e. ported) floor-standing box externally, but it behaves differently. The design I was thinking about is here:
http://www.quarter-wave.com/Project05/Project05.html


Alexander -I suspect the reason that the man you mention comments on the poor bass of his TQWT is that they haven't a proper contour filter on them -a common problem I fear. Check Martin's site for his modification to his own ML-TQWT project with a different filter, and the sudden improvement in bass performance (if you haven't seen it; here's the link:
http://www.quarter-wave.com/Project02/Project02.html
See the 'recent design improvements' page.)

Best
Scott
 
Horn is the way

If you want to keep things simple, the Fostex design horn is way to go. It seems a bit daunting at first when you look at the plan, but it's really quite simple to put together.

You will not get really low bass (as in subwoofer), but you will have plenty of tight, punchy, fast bass (any acoustic instrument will sound lifelike, even the doublebass).

If its not enough, try a 4 to 10 Ohms non-inductive resistor in the circuit (between + out on the amp and the + in on the speaker). Makes for a cheap, simple and very inexpensive Eq circuit.
 
Thanks Mr Robertg. Most probably I'll go for the fostex design horn as recommended since that all enclosure detail are provided for simplicity but I'll still try other types of enclosure if it is better.

Scottmoose, What do you think of the back loaded horn recommended by fostex. Will I get a decent low freq. response from this enclosure. Construction of enclosure shouldn't be a problem since I had my carpenter getting it done. Another thing is that I do not intend to use other passive components with the driver. Hopefully I'm gettin' the right driver. what you think of the fe206e frankly? My first intention is go for the fe208 sigma but then I ended up gettin this fe206e which I found not much info on the net regarding good enclosure for this driver. Rather dissappointed. Thanks for the detail explaination.

Toni.
 
tonitze said:
Thanks Mr Robertg. Most probably I'll go for the fostex design horn as recommended since that all enclosure detail are provided for simplicity but I'll still try other types of enclosure if it is better.

Scottmoose, What do you think of the back loaded horn recommended by fostex. Will I get a decent low freq. response from this enclosure. Construction of enclosure shouldn't be a problem since I had my carpenter getting it done. Another thing is that I do not intend to use other passive components with the driver. Hopefully I'm gettin' the right driver. what you think of the fe206e frankly? My first intention is go for the fe208 sigma but then I ended up gettin this fe206e which I found not much info on the net regarding good enclosure for this driver. Rather dissappointed. Thanks for the detail explaination.

Toni.


The FE206E is a good driver. Very good as it happens. That large (OK, VERY large) motor and banana-pulp cone are extremely impressive, especially for the reasonable price. Relax in the knowledge you have one of the best 8" drivers available. I personally favour its FE207E cousin, simply because my major interest lies with transmission-line speakers not horns, and it's better suited to these than the 206E, which was designed from the outset for horn-enclosures, like the more expensive, and in some ways inferior 208ESigma.

Of the plans available on the web, bearing in mind your requirements, interest, drivers, and it being your first project, I'd go with the factory horn design. It's often unfairly dismissed because of all the right-angles in the construction: they're actually there for a reason, not just to ease construction - they act as diffusors, and also, as Terry Cain points out, to allow a longer horn-length for a given box-size. I expect you'll get around 50Hz out of it, depending on room-gain and room size. Not spectacularly deep, but not bad at all. I've built the FE103E horn in the past, and liked it a lot. Fostex know what they're doing.

Out of interest -anyone out there tried the 206E in the 208ESigma horn? If so; what mods were needed? If it works well, I'd go for that -its a little easier on the eye.

Best
Scott
 
Re: TL and Horn Comparison for FE-206E

Onur said:
Why don't you have a look at my TL and Horn comparison for Fostex FE-206Es. It may ease thing up fo you. You can reach them from the link below and then clicking Fostex FE-206E link.

http://www.yildiz.edu.tr/~ilkorur/

/Onur


I confess I like the horn design... some interesting things there, good stuff!
Best
Scott
 
One thing that has made me shy away from the fostex recommended horns is the squared horn contour with each segment being straight. I've seen reports from a couple of people who went to all the trouble of trying round all those square corners and they were disappointed in the end result, however, those who stuck straight to the plans seem to always be happy with the results. Could it be that the straight segments and square corners are essential to the proper functioning of these horns? If so, can someone point me to some more info to help me understand more about this type of horn and why it works?

It seems to be in direct opposition to Ron's Dallas horn for the FE206 over at the full range driver forum, http://fullrangedriver.com/tiki-view_forum.php?forumId=1 . His successive versions of the Dallas have become a smoother and smoother horn contour up to the current model Dallas II version F .
 
I want a pair of FE206E's so bad I can taste it. My spousal approval rating is almost high enough-they will be mine.
Of all the enclosure designs I've seen so far; the one I like the best is Ron Clarke's Dallas II . With my limited wood working skills and tools it looks like it might be easier to build. Almost all angles are 45* and the print seems understandable. The print is based on 3/4 Birch ply and expressed in inches for us stubborn amuricuns. The Big Fun is too big for my room and I fear the Solo 206 would not have enough low bass. The Nagaoka is too wide and boxy and the Jericho looks too hard to build. The Dallas seems to have some good design features too. The filter chamber is smaller and the surfaces seem to reflect away from the back of the cone. The throat is at the bottom front of the 206e. The baffle is narrow and may image better. The horn mouth flair is not as truncated. Fewer bends in the horn may mean fewer standing waves. Hollow areas behind the driver that can be sand filled.
Am I off base on any of these design assumptions ? I'm very new here and there is just so much I dont understand yet but I am an apt student and do 10 searches for every post I make.
Good luck on what ever you build Toni ! Bon musicom, ceil sur terre !
 
Dividing a horn into Segments, but how?

If you have examined my page you will see that there is a Finite Element Simulation of a Transmission Line enclosure. I have generated a pulse in the top line and I have simulated the pulse wave till it left from the opening of the line. When it passed through the elbow, some of the acoustic energy reflected backwards. This is the case with sudden area changes in horns or transmission line enclosures, where dramatical cross-section changes occur. When this happens, you realize the effects by means of blured highs, unpleasent midrange. This reflections will rise the distorsion level, causing all the unwanted chain of reactions.

As far as my trials are concerned, I have seen that making the horn cross-section as close to the mathematical function, which describes it, as possible, reduces this effect. I have generated my own set of rules to make it robust. I didn't dig into the maths but my numerical solution of hyperbolic wave equation on an unbounded domain gave me reasonable results which I could be able to decide between right and wrong by just observing the outcome. I am not critisizing which horn geometry has the lowest distorsion level, but I am talking about which application of the same geometry can have the lowest distorsion level.

I believe building the horn without smooth corners doesn't effect the sound in audiable levels, by keeping the area change ratio under a reasonable value, however, folding the horn do cause some back reflections, which is the case with all folded designs. There are ways to get around this though.
 
Onur,

Thanks for the reply. You mention blurred highs and midrange problems resulting from combining straight segments of increasing area to form a horn. You also mention energy reflections of the 90 degree folds which causes problems.

My gut feel is that the squared layout the Fostex designs use functions as a low pass acoustic filter and the reflected energy is only in the higher frequencies which is purposefully dissipated within the walls of the horn folds. Does that make sense or is that just a lazy noob not wanting to get into the math and physics enough to really understand what is happening ?
 
Fostex Sound Reflectors

I don't believe that they are the solution for what I have tried to say. At the first place, the dimension of those are smaller then the wavelength of any low frequency disturbance, which is causing the problem. I suspect those are on the market to reduce the unwanted reflections, which are caused by a small rear chamber, passing through the thin cone of the speaker unit.

I was trying to mention about horn or transmission line resonances, and unvanted reflections from elbows, bends and horn mouths or line terminus. You have to tame them before they move your cone backwards or forewards. Unwanted reflected energy may cause doppler distorsion besides distorsion in low frequency range.
 
what is really happening?

That is the question that I have been working on also. The math gets too complex when simulating these enclosures and you switch to finite element analysis or numerical solutions. I have generated my own code, which I will publish at the end of my PhD study, on my web page. This code simulates any geometry so that you can observe what is happening at a certain frequency. When you place a certain enclosure in the simulation field and generate some tones you can observe what is going on inside a horn or a TL. As for your question, I coudln't - yet - able to observe such a behaivour. When I examine Fostex designs, I see narrow labyrinths, sharp turns, which causes complex interferences in my simulation field. Psychologicaly speaking, my designs show a more relaxed and clean interior reflection as compared to those and I regard those results as close to the way how it supposed to be. It is a pity that my designs haven't been listened with many listeners therefore I do not know how they perform as compared to those ones.

I hope this could be an answer?
 
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