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Old 17th January 2006, 02:05 AM   #1
fan is offline fan  Sweden
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Default FE208EZ enclosure?

im thinking about putting together a pair of speakers using fostex FE208EZ sigma.
but i keep reading here they only work in backloaded horn configurations?
actually i prefer a "compact" version in my small room. are these drivers useless in a box bassreflex design?
also i have no experience building cases. so id like to keep it four-by-four.

i see "omage speakers" sell a standmount bassreflex with the 206 driver. is it completely different with 208?

thanks!
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Old 17th January 2006, 04:20 AM   #2
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i cant tell you which characteristics of these drivers determine their enclosure suitability (might be qts but im not sure), but Im fairly certain you dont want to use a fostex driver that is designed for horns in a bass reflex. The fe206 and the fe207 both have bass reflex designs. If you haven't seen it yet, Madisound has a list of enclosure designs published by Fostex. Look at the bottom of the info page for fostex in the cataloq. I think the fe206 is considered to be the better of the two and I believe its more efficient.

If you want a smaller cabinet you might want to look at the fe103. It has a small bass reflex design and theres something quite appealing to the sound. Lots of designs on the web too. There are some really neat folded quarter wave pipes somewhere out there. There floor standers but very narrow and shallow. If you want the design ask and Ill try and find it again.

Yes the 206 and the 208 are different drivers.
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Old 17th January 2006, 04:32 AM   #3
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here's the page with all the cabinet recommendations

link
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Old 17th January 2006, 02:51 PM   #4
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Hi Fan... this may not be exactly what you are looking for but...

Fostex published recomended enclosures for their older Sigma line. Typically these drivers are used in back horns. I will post the graphic when i get a chance but basically the measurements for a 208 Sigma (old style with wizzer):

45 L bass reflex box
Square port 3.25" wide x 2.5" wide x 5.5" deep

Check to see how similar or different the driver you have is compared to the older style 208S.

http://www.fostexinternational.com/d...fe208sigma.pdf

Peace,
Godzilla
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Old 17th January 2006, 03:08 PM   #5
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I don't think the new ESigma will work in the same enclosure unfortunately -too much changed, not least the fact that this thing really does need a tweeter as it rolls off strongly around 12KHz. Pity -I'm not quite sure why Fostex did that. The Mr Cynic in me suggests that it was so they could make more money selling tweeters and fancy caps... ahem.

However, as 'Zilla quite rightly oints out, it's a myth to think that low Q drivers won't work in anything other than a horn. you just either need to engineer the enclosure correctly, or add a bit of series resistance. Job done. The FE208ESigma will do very nicely in the Factory Horn design (I even think it looks good), but there's no reason why it shouldn't work in anything else. Give me a few minutes...
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Old 17th January 2006, 03:26 PM   #6
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Dead easy. Hardly had to think with this one. Here's a straight, Mass Loaded Transmission Line. If you haven't seen one of those before, they look like a nice, simple, floor-standing bass-reflex box, but they don't work in the same way. I won't go into theory here: have a look at Martin's site for more: www.quarter-wave.com Suffice to say they give you the bass of a reflex enclosure with that glorious midrange purity transmission lines are so justly renowned for.

This enclosure is 42" tall, 9.5" wide, 11" deep. The centre of the driver is 11.25" down from the internal top. The port is 4" wide, and 2" long, and is located 4" up from the internal bottom. 0.25lbs ft^3 stuffing is assumed from the top of the enclosure to 12" from the base. It might not even need this much. A 4 ohm resistor is placed in the + speaker lead to the driver. So it's not as efficient as a horn, but it's still around 91db 1w/1m, which is pretty good going: 5w will be more than ample. It'll need some baffle-step compensation too -give me a shout if you want the values.

Remember the 208ESigma doesn't reach very high so it'll need a tweeter / super-tweeter whatever enclosure you put it in.

Best
Scott
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Old 17th January 2006, 03:34 PM   #7
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Very cool Scott!

Just for curiosity do the WS's do ported boxes like the one fostex recomended?

45 L bass reflex box
Square port 3.25" wide x 2.5" wide x 5.5" deep

Im curious to see how it 'measures' compared to the box you just made... which looks pretty darn excellent if you ask me!
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Old 17th January 2006, 04:31 PM   #8
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Indeed they do: 1 reflex enclosure modelled at your request for the FE208ESigma good sir!

It's pretty good, though I cheated a bit and used a 3"x5.5" circular port as the worksheets can't yet model anything other than circular ports. Dimensions are exactly the same otherwise as those on the Fostex site for the BR box for the FE206E. There's more ripple than the MLTL, especially up in the 900Hz region -but for a reflex enclosure, this is one of the very best I've seen with a full-range unit. No kidding. Impressive. Also, it has a nicely damped roll-off below 100Hz, which should be useful when room-gain is factored in. Overall, I'd personally go with the MLTL, as it goes a touch lower, has that TL midrange I like (the stuffing I think prevents some reflections coming off the internal rearwall and through the driver cone) presents a milder impedence curve to the amp, and would also remove the necessity for a stand, but this is by no means a poor substitute. Very impressive.

BTW -are your 168Sigma enclosures built out of pine?

Cheers
Scott
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Old 17th January 2006, 05:31 PM   #9
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Fan,

I defer to the above opinions. Once again conventional wizdom proves more conventional then wise ;-).

Scott,

I had been blindly subscribing to the myth of low Q drivers. Any idea why its generally believed best to avoid bass reflex on low Q drivers. Why does Fostex recommend that the driver not be used in Bass reflex designs.

Im also wondering, given that the sigma is quite expensive, if this driver would be worth the expense for what Fan is looking for. I've never heard this driver so I'm not sure whats special about it, but I do have a feeling that if Fan is looking for a small BR, that there are probably more suitable drivers to do the job. Im pretty taken with the dayton RS designs that have been popping up since the distortion measurements are so impressive and the price so low.

Id be curious to hear what admirers of the Fostex have to say regarding its virtues.
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Old 17th January 2006, 06:35 PM   #10
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Thanks Scott!

Well, lookie there! Your box is bettah… see, all this modern technology can produce something good!

Thank you for modeling the ported box. Unfortunately, I will not be building it but thanks for quenching my curiosity. I really am amazed how the MathCad work sheets help maximize results… INCREDIBLE!

Basically, it seems even tho fostex recommends a certain box it’s not necessarily the most optimal solution. Doesn’t mean it’s a bad solution either.

As for my lovely Fostex 168S, yes, the box is 100% pine except for an inner baffle made from mdf to help the screws hold the driver in place.

http://www.zillaspeak.com/zillaspeakfostex24L168.asp

The 168S will end up in modified straight pipes. The internal volume is very close to the original ported box I built based on:

http://www2.nkansai.ne.jp/hotel/nakanou/bs-168.htm

2.5” x 8” wide at the top
8” x 8” at the bottom
60” tall

All inner dims…. Approx 1.5 cubic foot… but in the shape of a Voigt pipe. If it’s not too much trouble can a sim be done for this using the 168S? I am planning to build a powered sub to fill out the bottom… my basement is big.

I am nearly done with my Pioneer B20/Piezo redo and hope for nice sounds from it as well. The boxes are waiting for a couple coats of glossy poly. I can’t wait to hook them up and listen.

Peace,
Godzilla
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