Fostex FE108E Sigma - Your thoughts? - diyAudio
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Old 19th October 2004, 06:29 AM   #1
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Default Fostex FE108E Sigma - Your thoughts?

Hi everybody,

I came across this driver recently and it has caught my attention

I plan on using this in a car audio application as a midrange (200Hz-6.3KHz) only. I have been searching long and hard for a reasonably affordable midrange unit that will play linearly from 200Hz to 6.3KHz at 30 degrees off axis for quite a while and so far i have finally, on paper at least, found something that just might work. The only worry for me is the low powerhandling of 24W music power(although its offset somewhat by the highish sensitivity and the fact that it will be bandpassed so i expect powerhandling will increase from its full range spec), and of course, its sound quality. Its a little pricey also, but if it does what i want it to do, i'll be more than willing to pay(about 90USD)

I was hoping i could get some opinions about how it sounds and how well i can expect it to work at the frequency range and off axis characteristics i'm considering. I will have a few(2-4) parametric bands of equalisation to work on the response dips at about 500Hz and 1KHz and any other in-car response anomalies.

Also, if anyone has any other drivers to recommend which fit the bill, feel free to suggest!

P.S Just thought i'd add: Up till i managed to find this driver, i was planning on using the SEAS Lotus(car audio version of SEAS Excel) 4 inch driver as a midrange. I am already using the SEAS Lotus 7 incher as a midbass/midrange unit in a 2 way setup and properly set up, i absolutely love it. The drawback of the 4 inch SEAS, however, is the fact that i cant hope to cross it any higher tha 3KHz because of its breakup. I am quite a stereo imaging addict, and am looking for a driver which will play the entire vocal range + harmonics, hence my search for a speaker which will play such a wide range. Off axis capability is a must as well since its car audio and the best i can do in terms of mounting is 30 degrees off and no less.

Best regards
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Old 19th October 2004, 04:46 PM   #2
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I think you would be very please with the fostex 108e sigma, I have owned my for a good little while now and have tried them in a couple of different cabinets have been quite impressed with this little driver. I have never heard the SEAS Lotus series so I can not make any comparisons there.
I don't have any measuring equipment so I cann't comment on the off axis response at 6kHz. I do however listen to mine from all location in my house and find the sound quite pleasing no matter where I am. If you do get them I would at least try running them open on the top end, you may find that you need a little more sparkle, but it cann't hurt to try. It just seems a shame to cut off the top end of this driver, which is so good, in my opinion.
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Old 19th October 2004, 05:30 PM   #3
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All the Fostex drivers that I have tried have a beautiful mid-range and rising response toward the high end which allows them to actually sound better off axis than on axis if no compensation filters are used. I've not used the FE108EZ but it has found it's way into Ed Schilling's Horn ( I've used the FE103E, FE127E, FE167E and FE207E and been very pleased with all of them.
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Old 19th October 2004, 05:35 PM   #4
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Ask over at and I'm sure you'll get more information. These guys are meant to be run full-range, maybe with the bottom lopped off, maybe with a tweeter crossed in with a capacitor. The goal is to avoid a crossover between the amp and your nice speaker. You get a very immidiate sound this way. I'm working on some 168esigma cabs right now, and I'm pretty excited. The word is that these Fostex full-range speakers need a few hundred hours of break-in. At first they sound screachy but then smooth out. My 168s are in a box facing each other, wired out of phase, playing the radio at about 2 watts for a week now. Even in their cardboard box, I can tell that they've warmed up, gotten louder, smoothed out. I built a pair of RS1197 (fostex 103 knock-offs) Tlines running full-range that are very listenable, although they don't rock. Good luck! /jd
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Old 19th October 2004, 07:00 PM   #5
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My buddy Chris has FE108e Sigmas (in a Buschorn II). He is using it full range. In the horn it is a bit bass shy but elsewhere it is sublime... should worl well. I'd make sure i braced the magnet in a car setup.

I wouldn't worry about the power handling spec (people worry about those numbers WAY too much)

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Old 19th October 2004, 11:18 PM   #6
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Hey thanks for the replies guys!

It seems this driver is definitely worth giving a try. How exciting!

Does it really make a difference to play the driver full range from 200Hz onwards? The main issue i have is directivity, because i will be mounting the driver 30 degrees off axis(any more on-axis is pretty much impossible in a car environment) which is why i plan on switching to a tweeter after 6KHz. I suppose its worth a shot since all it takes to try is is an adjustment on the electronic crossover but i'm not sure how well i'll hold up.

If there are any more opinions, feel free to contribute! Maybe you guys could also suggest a great small sized tweeter to take care of the highs from 6KHz onwards. Only requirement is that its small enough to install easily and performs reasonably well from 30 degrees off axis. At this point i am using a Morel MT-2 car tweeter and i must admit i do like it, but as we all know in audio, we can never be satisfied!

I like the look of the fostex super-tweeter range but they seem largish and dont perform very well off axis
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Old 19th October 2004, 11:38 PM   #7
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Does it really make a difference to play the driver full range from 200Hz onwards?
It's difficult for us lovers of quality full-range drivers to accept chopping off such a great speaker so early. I don't see the harm in bringing in your tweeter later than 6k. Think of it more as a helper tweeter rather than your sole source of HF. The 108 has excellent off-axis characteristics. IMHO, I don't think you'll miss anything.
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Old 20th October 2004, 06:02 AM   #8
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hehe thanks. I promise i will at least try playing the speaker full range before thinking of adding a tweeter into the mix. I seriously have doubts looking at the off axis response above 7KHz but if you guys think it'll work, i'll definitely give it a go at least.

On another note: has anyone heaard of the FE108E Sigma II speaker? I saw a website for it on the fostex japan site i think, and i noticed that the rising response is more pronounced on this model which makes it even better off axis(one would think, at least). It also has a much bigger magnet, although i am unsure how this will help, if it does at all.

I dont suppose anyone here knows how much it costs or how i could get my hands on a pair of those? If it's about 120USD or less a driver i might be willing to give them a try although i am exceeding my budget a little already(so what else is new???)

Oh yes, forgot to mention, the reason for me going for a 200Hz crossover point is because the fostex will probably be mounted in a custom kickpanel fibreglass enclosure , and since i drive a right hand drive car, space will be very very limited. I have at most about 1-2 litres of sealed space available. I plugged the driver's T/S specs in WinISD and in that kind of enclosure, rolloff will start to begin at 300Hz(-3db at about 250Hz). I do plan to compensate for the rolloff with an EQ but any lower than 200Hz doesnt seem feasible given these limitations. I could mount the driver in the dash but the pathlength differences will result in very poor imaging which defeats the purpose of my using a splendid full range driver like this in the first place

Now if i could fit a nice, low tuned TL enclosure somehow.... then we'd really be talking!
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Old 20th October 2004, 06:31 PM   #9
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I understand that Madisound has a single pair in anticipation
of a batch of several hundred. Silver wire, magnet diameter
bigger than the speaker, and some other tweaks. I believe
it will cost more than you want to pay....

Meanwhile, you may find that the FE108ES is adequate on the
top end by itself. Bit of a peak around 15 K, and while it doesn't
have a dip at 500 itself, it does have one at 1KHz, but it's only
a few dB. I'm not sure I would even bother with it.

I think it will work well down to below 200, but you'll probably
want to put in a shelving network to take the upper mid and
high frequencies down a few dB.
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Old 21st October 2004, 08:42 AM   #10
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Thanks Mr Pass!

I've got another final(hopefully) question. From the opinions i gather so far, it seems the Fostex is a very good driver, but how does it stand(in the 200+Hz region onwards) when stacked up against other, more expensive superdrivers like the revelators or the SEAS excels, or anything else in that bracket? I know i do have a limited budget, but i am hoping to build up a speaker system which will hopefully have very few equals, regardless of price. If the performance is not top notch(i'm hoping it is though), i would welcome alternative suggestions, regardless of cost, which i will hopefully be able to save up for in the long term. Of course if it costs more than about 250USD per driver, then i probably will never be able to afford it, period, but i thought i'd ask anyway.

I've already checked out other full range drivers like the jordans(off axis response too poor) and manger(too expensive), among others, but i might have left something out. I'm hoping for something about 4" or so of course

As long as the performance of the speaker justifies its price, i'll consider it.

Also, i just read that very long thread about the disadvantages of full range drivers. It was very interesting, and i'm wondering if the IM distortion will come into play if the speaker plays from 200 to as high as 8-9KHz. I saw a formula there that can calculate the answer to this question(it was a function of the xmax, wavelength of the highest frequency, and some other variables which escape me at this point in time) but have no idea how to calculate. Anyway its a little OT but i thought i'd bring it up

Best regards
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