Fostex FF225K

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Excuse me for my english, I'm French.

Does somebody can speak to me about the sound of Fostex FF225K. I have two Fostex FT17H, and I think I will buy two Fostex FF225K for build two 2 way bass reflex speakers.
FF225K are not sell in France and I must buy these drivers by the net in deutchland. Before to do that I would have some informations about experiences of people who have build speakers with Fostex FF225K. I will connect these speakers with a double push of EL84 20W I have build myself or with a class A of KT88 40W I have build myself to. For the moment I use Infinity Alpha speakers. I listen different types of music like Rolling Stones, Beatles, Joe jackson,..... Verdi, Mozart, Maria Callas.

Thank you.

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The Ft 17h is a tweeter,
Pascal and I have been in touch, We both think the FF225 has a smoother response than the 208 so maybe doesn't need a notch filter. Also it has a smidge more bass. So we are interested in using it with a tweeter, crossed over really high (maybe 10k).
I am planning to use only 4uF cap as the crossover since the tweeter I'm planning to use (Vifa MG27TG29-04) has a 4 ohm impedence. This particular tweeter is a fabric dome, but has a wide peak between 10k and 22k where it's efficientcy rises to 96dB. I have no idea how it will sound at that freq, but the idea is mainly to add "air" to the sound. No crossover of any sort on the 225.

The 208 has a reputation for slightly greater detail than the 225 but we think it is due to it's greater high end, maybe not in the midrange. I think the extended response of the 208 comes at a cost of some resonances lower down.

No one seems to know anything about the 225 and the only plans we've seen are the bass reflex ones Fostex publishes, so we are excited about exploring new ground. The 225 cost about $90, so it isn't a cheapo driver.

I have finally ordered the plans for Dick Olsher's Basszilla, they might arrive today. I think that will give me a lot of insight into how wide range drivers work in general.

My plan is to first try out the concept with a bass reflex, then it it sounds great, and if I get the funds, convert to open baffle and big woofers like the Basszilla.

So...... I'll have a full range driver, 3 way speaker!!!
I think I'll call it the Oxymoron

I hope you don't call me something similar ;)

I am interested in any comments from anyone about this idea

Variac the Destroyer
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I did get the Basszilla info today.
The info is useful even if you aren't making that exact speaker.
It has a notch filter that tames the big peak in the
208 drivers response.

It uses a pro 15" speaker for the bass.
I'm tempted to use the Eminence 15" pro driver instead.
it costs $80 instead of the recommended one at over $250 ea.

Now something has come up that makes me wonder about the FF225

It has really smooth response, and claims to handle 30 watts continuous, but it's Xmax is 0.3mm (0.012 in.)
That's less than a third of a millimeter.

I had assumed that the 225 was basically a FE 204 without a whizzer cone, but the 204 has an xmax of 1.5mm

The FE 208 Xmax is .75mm

It's hard to believe that the 225 can handle about the same power as the 208 with such a limited travel

Maybe it severely compresses the sound above say 10 watts.
I sure don't know. I tried to model it and with 30 watts it doesn't seem to handle under 400 hz.

Now I'm not so sure if the 225 is the right driver.....

I don't know if the FF225K is the right driver to use, and I wonder if FE207 or FE204 could not be better ? These drivers could be use in Bass Reflex, Double Chamber Reflex, TQWT, horn loaded....
The Xmax is better and FE204 / 207 have good response. For using in a tree way loudspeaker with the medium in Fullrange, this could be a good solution (FE204 and FE207 seem to be good in medium). For basses we can use one or two subwoofer with Audax, Beyma, eminence, jbl, monacor.... pro drivers.

I'm in touch with a man who have build two loudspeakers with FF225K and FT17H in Fostex recommanded enclosure, but he use them for home theater with subwoofer. I have ask him questions about these drivers, I hope to have some indications. I will say it to you.

I think that we don't forget to think of what we are doing with FF225. For me I want to use it with an EL84 20W or KT88 class A 40W or 845 20W selfmade amplifiers in a small room (the room where I work in my house) and not in my living room, so i don't want to have an enormous loudspeaker (but with sufficient basses to listen some types of music like The Old Rolling Stones). There is a lot of fullrange drivers with good efficiency for a good price (Fostex, Audio Note, Supravox, ....) but not a lot with good basses that can be use with only a tweeter.

Often people who recommend fullrange driver use it for classic music and don't like basses. I like classic music, but, if somebody have an opinion about some fullrange drivers with just a tweeter addition (no crossover) for listen music like rolling stones, Joe jackson (not michael).... and old blues could you give me your opinion ? And recommend some drivers.

Thanks all.

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These folks seem to like the 204 a lot

They didn't like the 225 so much but I thought that since we were doing something dfferent, ( adding a tweeter) we might actually end up with something better.

The 204 has the greatest Xmax of the 225, 208, 204
The 208 was designed for horns I believe, so it's limited excursion isn't such a factor.

I think the 204 is the best for bass reflex alighment.
It's also pretty cheap, so what's to lose?

If I were going to use a 2 watt SET, the 225 with tweeter would be at the top of my list!, but my Son o zen will be in the 15 watt range.

Although the same people mentioned above don't like the 207
much because it doesn't have the same high end, it appears to be a 204 with a bucking magnet so it can be used for AV
The frequency curve is different though-maybe better for the tweeter idea? I haven't studyied it much yet. One thing to keep in mind is that the curves shown by Fostex are compressed in the vertical direction compared to many graphs. I expanded them vertically2x on my computer and the curves look a lot lumpier!

Interestingly, the 225 is rated as handling more power than the 204

I now deciding betweeen the 204 and 207

it's difficult to choose for me (and in France it's impossible to listen Fostex FE204, FE207 or FF225). One man who have build loudspeakers with FF225 and FT17H wrote this to me:

"Dear Pascal
Question of power: I read 30W continious as the RMS of a white noise signal. This is important, since you will not have all the power in one frequency (like 50 Hz). You handle the very same fact by using a 10W tweeter in an 50W system. But this time,
it referes to the bass. Having the standart cabinet will cause the air to force the woofer back into it's normal position.I never did simulations about displacements, but you hear it verry clearly if you are in the limits! (mechanical distortions sound very different from electrical amp distortions). Your ability to define a sound in it's sterophonic panoramic position is decreased, if the diafragm displaces too heavy (intermodulation).
FE204: No, the 204 is a verry different contruction. It has a less massive magnet an the moved mass is less. Yes, it displaces more. So it reaches the physical limits earlier. I used it in car hifi on the back board. The results are breathtaking...
The 225 "K" type is unknown to me, I used the FF225 without any suffix. You are right, the displacement is less, so it is able to work in bigger cabinets and have lower cut off feq..
Because the displacement is less, it has a wonderful panoramic definition in the midrange. This is an other reason why I choose to have the X-over as high like 4.5 kHz. (Which is generally too high for a diafragm of that diameter.)"

Very very difficult to choose for me. I hope that a japanese's man who i have contact tell me more about FF225. I have try to contact Fostex for having informations, but no reply. I'm "dubitatif" like we say in France.

Pascal TAJAN
Hi Mark,

If i understand good, you 'll use fostex driver like a medium in a 3 ways (tweeter+fostex+pro bass) with 15 watts amplifiers so the most important for you in my opinion, is the Medium response. You can use Fostex FE164 or FE167 and FE204 because they have good efficiency and good medium. For me it's little différent, i think i'll use fostex driver like 2 ways (small room) and i need good bass response. It's not sure that i'll build subwoofers, actualy I use good Infinity loudspeakers for my principal room.
It's why it's so hard to me to decide and if it's too much difficult to decide i think that i will study an other possibility like Audio Note. The best think to do it's to listen one driver before to decide, and i hope for you that you 'll can do it in your country (in France it's impossible). For me the only solution it's to find people who have listen the sound of Fostex drivers in a similar configuration and who can tell me about this driver.

Best regards.

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For those that stumble on this thread in the future, I thought I'd add some comments that Pascal sent me from people he has been in touch with:

"Now something has come up that makes me wonder about the FF225 It has really smooth response, and claims to handle 30 watts continuous, but it's Xmax is 0.3mm (0.012 in.) That's less than a third of a millimeter. I had assumed that the 225 was basically a FE 204 without a whizzer cone, but the 204 has an xmax of 1.5mm The FE 208 Xmax is .75mm
>The 225 is probably more like the 208 with a (thick) stamped frame and no whizzer. The FE xx4 series is pretty different. They are higher Q and lower in resolution but musical and laid back sounding, IME. The xmax is obviously higher.
>I worried a little about that spec too, but the factory xmax figure is conservative and probably indicative of it's linear travel. The actual excursion limit is very much greater than this. I wouldn't worry about it unless you plan on listening to heavy metal with solid state amps. Still, if it was me, I would put in a backloaded horn, a la Lowther. I like the sound better than BR and it limits cone movement to a great degree, thereby giving as much dynamic range as anyone could need for home use.

It's hard to believe that the 225 can handle the same power as the 208 with such limited travel Maybe it compresses the sound above say 10 watts
>I doubt it, but 10 watts with a 99db driver is quite loud.

I sure don't know. I tried to model it and with 30 watts it doesn't seem to handle under 400 hz.
> 30 watts? that's 114 db...

Now I'm not so sure if the 225 is the right driver....."
>It depends. I think people make too big a deal about excursion. Companies vary greatly in their honesty about the figure, so it's tough to tell what it really is. The coil may move out of its sweet spot from time to time if you play it very loud, but the distortion/compression will likely be inaudible. I found that the little 125k played moderately loudly before pooping out, about the same level as any other 4" driver. It really depends on you listening tastes. If you like mostly metal, you should just buy some used JBL L-100's and be done with it.

I agree completely with your summary, I feel that Xmax is a very soft limit and while it should not be ignored I do not let it dominate my thinking during the design process. I am driving my Fostex FE-164 and FE-208 Sigma drivers with a 200 watt/channel solid state amp. No heavy metal or rap music for me, mostly acoustic unamplified instrument recordings. I have never had a problem with to much power or played my system so loud that I felt that the distortion was becoming audible. I do not baby the speakers and have no complaints with respect to Xmax.
Can't comment on the Fostex, but I don't have any trouble hearing distortion at moderate levels on just about all of the RS drivers at what I consider very moderate volume, even when using EQ to drop the <80Hz BW.
-Since the Japanese love all things Altec, JBL, etc., I wonder if they use rising rate suspensions to 'soft clip' overexcursion like was/is done in prosound?
It seems like a strong possibility. The 125K has a normal half roll surround and average looking spider. I couldn't get it to hit the wall; it was more like the gradual compression onset of a MI driver.
Hello all,

I have spend two days of hollidays to study Fostex drivers and try to find good informations.
Finaly, I think seriously to build a "little special" 3 ways speaker that could have good efficiency (~95db) in a small room. In fact I think that the medium must be a full range use as a full range. For that I have retain FE207 or FE204 or one I have just discover, the FE167. This is a 95db full range, and it's seems to have a good response. I think that it will be very very good in medium. FF225K will be good but it's seems to me that it will be better alone and not in a 3 ways. The frequency seems to be good for what i want to do. With the addition of the FT17H out of the enclosure I think It'll be good. For the bass, I'll use Audax PR240MO or PR300MO (95db). For a "normal room" I don't think that I must be use a enormous PR380MO. At this moment I don't know what type of enclosure I will use for bass.
FT17H+FE167+PR240MO or PR300MO seems to me that it is a balanced solution. Using this with a 2 ways tube active filter and a class A tube amplifier for the medium/high + a more powered tube amplifier for bass, i think that i will have some good hours of pleasure.
I'm sure that Fostex drivers FE and FF series are good choice because with these drivers, the possibilities of evolutions are open. In a French magazine i see that Fostex drivers like FE204 has been use in Japan with a horn in front (the driver on the picture is a old FP163).

Best Regards. Opinions and ideas are wellcome.



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I think you are doing the right thing with a bass driver.
Without it I don't think you will be happy.

I am going for the FE204. I think I may add the woofer and tweeter later. Or who knows, I may like it as is.

A 3 way is usually very difficult to design. By crossing over
at the extremes, I think we can get around that AND get the coherent sound of a fullrange driver.

Good Luck


using a full range driver in the medium with tweeter and bass sub is a concept often use in France. CAF and Davis Acoustic have used it in popular "audiophile" loudspeaker. The problem with all these loudspeakers is that they are "enormous" and that they are for rooms higher 50m2. I would concept and building a loudspeaker for a more "raisonnable" little room. They must be used in a living room or in a special room (with acoustic treatment) and in that case the room that i can reserve for my passion can't be more than 30m2. A two much big loudspeaker high efficiency in a little room is tiring and agresive.
The concept that I'll use is the same, 3 drivers, each in a separately box, a full range in medium (90Hz-10KHz) with extended super tweeter over 10Khz (using only one capacitor for crossover) and bass sub (90-17Hz).
The crossover will be simply as possible or will be active crossover with 2 tube amplifiers.
If I will use FE167 the more good flat efficient response seems to be between 180Hz and 10Khz, with FE204 it seems between 200Hz and 10Khz. I'm not sure of what driver i'll be use because I want to have the best flat response. Closed or Bass Reflex enclosure ??? I don't know at this time, but I have eard that Fostex driver don't love closed box. Does someone have an idea ?
A little transmission line could be a solution.
For bass box, I will certainly use bass reflex enclosure, but If someone have an other idea i'll study all proposition.
I will give you knews, and the result will be on my site.

Best Regards



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I would suggest an open baffle for the mid.

Just mount the driver in a piece of MDF or Plywood of the correct size.

Then you get a frequency response very similar to the graph from Fostex. The size is probably about 60cm square, maybe a bit smaller.

To determine the size I think this would work:

Calculate the wood width with the baffle step formulas for cabinet width here:

so that the baffle step would correspond to the lowest frequency that you want the driver to handle. Then make the piece of MDF the "Cabinet width"

I'll buy the FE204 this week but delivery time is 6 week in deutchland, so that let me the time to study my loudspeaker.
I have saw on audax french site forum that PR300MO are not very good and that PR240MO are difficult to use in bass reflex (in 80Hz-100Hz). Does somebody know SEAS H368 CA25FEY ? It's seems to be a good driver for what i want to do. PR240MO or CA25FEY ?

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Variac said:
No one seems to know anything about the 225

I have seen a few positive comments on this driver on the Full-Range forum, but haven't seen or heard it myself.

So...... I'll have a full range driver, 3 way speaker!!!

That is like my "FR"* speaker. Active woofers below 125Hz, budget BD-Pipes above that, with a tweeter coming in at about 10k. Best tweeter i've had so far is a 2" alnico Isophon open-back cone.

*(mostly full-range is a more appropriate term)

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Hey, It's fun when an old thread comes back to life!

I found that dual chamber site later and the plans on the Fostex web site. Thanks KW

It is for a smaller (and less efficient driver) then we are using. I'm sure I could have scaled it up but Pascal and I have been keeping in touch, and we have gone the route of the big bass driver with 8" Fostex and maybe a tweeter.

I found out about that concept from the Basszilla plans, which I bought. As you can see from the pictures Pascal posted, a full range with big woofer and a tweeter was a common idea in France. The open baffle too.

For the bass driver I bought two 15" Selenium wpu1505 from Parts Express on sale for $100ea. They have a pretty smooth curve but a peak a little above the crossover that I want to chop off.

Pascal got the Eminence Delta 12LF I believe. Both claim to put out 97dB but I'm pretty sure they at least put out 95.

I'm using the passive crossover that Dick Olsher recommends for the Basszilla but at 180 hz instead of 200. This is about the lower limit that you can use a passive but it seems like it will barely work

I am using a steel core inductor from Erse that Zylatron sells. A cored inducter is the only kind that seems to work in this size(around 14Mh, 14 Ga wire) Nelson Pass says it will handle 6 amps DC in an amp. It should handle more AC amps in a speaker.

Since my Son of Zen will put out 25 watts max, I think I'll be OK.
Of course an active crossover is optimal, but I would want to spend the time and money to make a good one and the passive
approach is pretty reasonably priced. Also I need to make another amp to use it or I could fix the bad channel in my Adcom
Another project.....

The full range choice of the week changes weakly ;)

As you noticed I'm sure, Pascal and I got a little worried about the FF225's xmax. - half what the FE 208 has. I'm sure it would work, but might get stressed in an open baffle. The Fe 208 is what Dick uses in the Basszilla but it is reputed to be best for horns also. It definatly needsa notch filter to tame it.

There is some question if one can actually get a FF225 anyway.
Madisound seems to be the new Fostex distributer and they don't have it.

Pascal and I decided on the Fe 204 because it has more travel and is highly recommended- also cheaper than the 208!!

So when we went to order we discover that the 204 has been discontinued. They have a new driver- the Fe 206 This has the big magnet from the FF225 for more damping, which makes it very much like the Fe208, but the xmax of the old 204,which is double that of the 208 and 4 times that of the 225. Also it only costs $94
(it has a pressed frame-but heavy)

It does have a whizzer, which I had not wanted, but what the hell I'll give it a try. It also has that yummy banana pulp cone paper!!!

The response curve is as awful as the 208, but lots of people like the 208.It seems to not have the 2 huge peaks the 208 has so might be OK I might need to design a notch filter or try to talk Dick into buying a pair and testing them and developing a notch filter. He is somewhat interested in a half price Basszilla and has measurement software and mics.

It will be interesting to try out the new driver: It might be horrible-you guys hear anything about it?

PAscal is assembling his cabinet, I will start mine in 2 weeks.

Some have told me a tweeter with a first order filter might have phase problems with the tweeter. Planet 10: have you had much luck with a tweeter with a full range with whizzer cone or haven't you tried it?

(Fostex reeommends a single 1 mfd cap for addding a tweeter to the Fe 208 which I believe will roll off 6 db/octive starting at 19000 hz! ) so we are talking about just the very top end here.

We'll keep you informed, please tell me of any rumors regarding the fe206


but this is for FE168. I saw on madisound site, Fostex recommandations for new E series. Fostex give a double bass reflex enclosure for FE206E and 207E.

I have buy a pair of FE206E (not delivered at this time) and I will use them on open baffle upon a Eminence Delta 12LF bass enclosure.

Best regards



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Variac said:
Planet 10: have you had much luck with a tweeter with a full range with whizzer cone or haven't you tried it?

Not yet, but i have a box for a Pioneer 8" that will get a dustcapectomy and a phase-plug with a naked piezo on the tip (ala PHY-HP). The baffles need to be glued on and a couple coats of varathane and they will be ready to start playing. Based on the work done by Godzilla.

And when Chris gets finished renos he is building the boxes for our Bipolar RS 40-1354 experiment (the middle ones). It will probably get something up top. if the Pioneer phase plug trick works, i have another set of piezos ready.

Hello boys .:)
I have received my pair of FE206E today. I have try them on test open baffle and one of my tube selfmade amplifiers. The sound is beautifull, flat response. I have try to use a FT17H with them, it's better, more "brillant"(in french, sorry), more definition upon 10Khz. Of course I will work on crossover for having the best result. I think to use a 6db crossover, like Fostex recommendation for FE207. For FE206E and Delta 12LF, I think I will use a 6db first order crossover at 300Hz. So here in France some manufacturers have used a special calc for crossover (often on open baffle). We take the 6db crossover and use a 1,4 coef. For example if the theory say that for a 300Hz crossover we need C=66,25 µF and L=4,25mH, we try to use something like C=66,25/1,4=47,3µF and L=4,25*1,4=5,95mH and make some regulations ("reglages" et "ajustages" in french, i'm not sure of what you say in english :confused: )

Best regards.

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