help with a box for fostex fe83e

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looked on the fostex web sit and they have a drawing for a base reflex enclosure.i had the boxes constucted according to their plans.i want to know what to expect sound wise.would anyone be willing to look at the plans on their site ang give me some help on what to expect sound wise.i am using them on a desk with a t amp. thanks, larry
It'll be an uphill battle to get much in the way of SPL and extended bass from this driver in even the double bass reflex enclosure.

There are probably enclosures that could squeeze a bit more performance from this driver, particularly in the LF area - but eventually it'll hit the wall.

OTOH, it sounds as if you'll be using them in a very nearfield situation (computer speakers?), in which case you won't know the extent of the limitations until you plug them in.

GM's comment regarding BSC should also be considered
right now i use a amp6 basic an old rotel cd player and two minimus77 speakers.they sound pretty good .the center immage is realy nice.i hope these will beat them. full range are noted for thir mids right?as you can tell i know nothing about speaker building.any help would be great.

Don't remember doing it and if I did I apparently didn't save it. Did a ~32 Hz FF185K though with a 59.872" square mouth. Stretch it up and it'd be the size of a wide entrance door. ;) The sim says it's only good for one watt down low, but a big tweeter making 100 dB/35 Hz while barely moving would be a sight to behold if it can actually do it.

The trade-off though is that due to the ~257" path-length you'd need plenty of digital delay and a high gain front horn on it to balance it out with a tweeter horn to finish it off, so not worth the effort for such limited dynamic headroom.


During 2003, I have built a pair of these for a set of FE87E (see image). After reading all the reviews saying "a lot of bass for such a small speaker", I was a bit disappointed. Ther is no bass for me. However, voices sound nice, and small combo music is nice to llisten to. Very good imaging.

When combined with a pair of low-range speakers they sound very nice. They are one of the nicest mid/high units I have heard so far.

Further, I have tried them in a FRS-8 (Visaton) Buschhorn enclosure. This also delivered a very thin sound, much less body than the FRS-8. Also here - no bass for me. Even less balanced than in a BR. Note that this rear loaded horn was not designed fort this driver. The Fostex horn enclosure probably will do better.

Last but not least, I tested the FE87E in open baffle enclosures with more or less serious constructions. I have tried the baffle from the BR enclosure for example. The most funny one is seen in the other picture. There I have screwed a box to the BR baffle to obtain a lower tuning of the mid/high unit.

In open baffle, I love these drivers! Mainly because highs and mids are very coherent and sound well together. I am planning to build a nice enclosure and fit them to a nice set of 6-7" low range speakers that I will use in a TL enclosure. A passive filter to make a lowpass for the woofer and a highpass to lower the low frequency response of the FE87E and make them play cleaner.

Have fun with your little boxes! These are very nice drivers to experiment with!



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thezaman said:
thanks for your response that is what i was looking for did you stuff the boxes at all?and are there any mods that might giv a little more base

I think the short answer is "no, probably not even with a far more optimal performing enclosure" ( such as a BIB) This driver simply has too limited Xmax/power handling capabilities for anything much below 150-200Hz. With enough power and digital EQ or passive BSC, you could likely move some air into the upper 50's, but it would be too easy to breach its limits at anything approaching realistic levels.

BTW, for those contemplating a simple OB with a similar driver up top, there's another Fostex model that from a brief experiment I might suggest could work very well indeed - FF85K

What I think GM is getting at is - think of this as a decent wide-band mid/ tweeter good to lower midrange, but for true full range performance in anything less than very nearfield/small room venues, separate bass driver(s) will definitely be required..
Good luck! If the 77s are anything like my original 7s, they will embarrass the ~140 Hz 83 down low and up high (if you still have good HF hearing), though it will probably sound better through the critical mids/lower HF, which in a desk app is probably an acceptable trade-off.

Anyway, looking forward to a review.


an alternative would be the FLUTE,
indirect radiation, no colouration,

down to 100 Hz, a sub is needed,

Omnes Audio and Monacor and Tang Band
have driver with more than 1 mm Xmax.

Fostex FF85 K has a bit to light weight membran,
a bit hizz at 10kHz.


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Horst - we can all fall into the trap of suggesting something entirely different than the original inquiry, particularly if our favorites include drivers from a different manufacturer's catalog, and our own enclosure designs.

I'd agree that the FF85K or any low X-max, small FR driver would benefit from woofer, perhaps even higher than 100Hz (one could argue that's not really "sub" frequencies); but as to "a bit hizz at 10kHz", I'll differ with you - while the on-axis rise in HF does start around there, I've found it hardly as objectionable as many 3-5" metal cone FullRange drivers.

And, of course if allowed to espouse an individual preference, with careful "cone treatment" and application, the FF85K can give many much higher priced midrange & tweeters a run for their money.
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