Fostex FE 108eS Backhorns

Richard1957 · 15th July 2009, 02:03 PM

I have a pair of Gemme Audio Concerti 108s that use Fostex FE108EZ drivers, backhorn loaded, a link to a full description is: http://www.6moons.com/audioreviews/gemmeaudio/108.html
I bought them in a moment of weakness because I like the single driver concept. However, they suffer badly from boxy sound, very woolly mid-bass which makes listening to orchestral music painful. I am not ready to give up on these (yet). Can anybody suggest some modifications that might work. From my (limited) reading, it seems as though the termination may be the problem. I am considering buying some 6" foam rollers (used for exercise) and making a 3" radius termination to go around the horn exit. Does anybody have any experience of trying this? Any other suggestions?
Thank You.

Scottmoose · 15th July 2009, 03:20 PM

The Concerti 108 is essentially Fostex's own FE108ESigma box design supplied free with the drivers, albeit smoothed out and (very prettily) built via the translam method. The basic Fostex design is OK, not great, & does suffer from a degree of boxiness, which the Gemme box inevitabley inherited (IIRC, when 6moons reviewed the Concerti, they noted this very trait). This might be compounded by the fact that they smoothed it out too: it's not usually a good idea to try smoothing manifold style horns, as they are usually designed specifically to take advantage of that style of construction.

FWIW, I'd look to add a little extra damping in the back-chamber & throat, and you might want to try adding some in the base of the cabinet (just stuff it to the bottom down the mouth). That should go some way to reducing any unwanted midrange output & might ease the boxiness a little too.

planet10 · 15th July 2009, 03:31 PM

Quote:

Originally posted by Scottmoose
This might be compounded by the fact that they smoothed it out too

And made it out of MDF which has higher energy storage which will further exacerbate things.

dave

chuyler1 · 15th July 2009, 06:02 PM

...for $3700??? Woah boy. Good thing I found diyaudio before anything else.

planet10 · 15th July 2009, 07:44 PM

Quote:

Originally posted by chuyler1
...for $3700???

That price was a major impetus for the Frugel-Horn.

dave

Richard1957 · 15th July 2009, 08:44 PM

Thanks for the stuffing suggestions, any particular grade of wool?
BTW, I didn't pay $3700! (Thank goodness).
Richard

Daze · 15th July 2009, 09:06 PM

The mouth opening of this horn is incorrect. If you look closely, you can see a large cavity at the mouth's opening which resonnates. It is not in check with a normal horn flare. This horn is also not a copy of the Fostex design.

The only remedy that I can see is adding a piece of wood (or whatever) that will smooth the flare opening and get rid of that large cavity.

The only other issue is that, supposedly, the interior of the horn is also a polished finish. Inserting damping inside the horn will reduce the midrange glare.

Good luck.

Scottmoose · 15th July 2009, 10:53 PM

Who said it was a copy of the Fostex design? Copy means something is identical. I didn't say that. I said it was effectively Fostex's cabinet, smoothed out (not especially well IMNSHO -trying to do that with a manifold style design as the basis is looking for trouble on many levels) with translam construction.

The terminus isn't ideal, I agree. Up side, it could be worse -the curve does continue round a ways, which will reduce the problem, and IIRC, many of these cabs. were damped around there with leather or similar.

Re the damping material, it's going to have to be a case of suck it & see I'm afraid Richard. They all have somewhat different properties, require different densities, and have slightly different detail characteristics. If you want to go with wool, look for long hair sheep wool (suitably washed & treated of course...) Otherwise, it's good old dacron, fiberglass, preferably of the non-allergic variety (although you still need to be careful of course) etc. FWIW, don't rush it -make a change & listen for a while before deciding what, if anything, to do next.

Cal Weldon · 15th July 2009, 11:55 PM

Quote:

Originally posted by planet10
And made it out of MDF

Ad says HDF.

planet10 · 16th July 2009, 01:26 AM

Quote:

This horn is also not a copy of the Fostex design.

Quote:

effectively Fostex's cabinet, smoothed out

I'll go with Scott.

dave

15th July 2009, 02:03 PM	#1
Richard1957 diyAudio Member Join Date: Jul 2009	Fostex FE 108EZ Backhorns I have a pair of Gemme Audio Concerti 108s that use Fostex FE108EZ drivers, backhorn loaded, a link to a full description is: http://www.6moons.com/audioreviews/gemmeaudio/108.html I bought them in a moment of weakness because I like the single driver concept. However, they suffer badly from boxy sound, very woolly mid-bass which makes listening to orchestral music painful. I am not ready to give up on these (yet). Can anybody suggest some modifications that might work. From my (limited) reading, it seems as though the termination may be the problem. I am considering buying some 6" foam rollers (used for exercise) and making a 3" radius termination to go around the horn exit. Does anybody have any experience of trying this? Any other suggestions? Thank You.

15th July 2009, 09:06 PM	#7
Daze diyAudio Member Join Date: Dec 2005 Location: Montreal	The mouth opening of this horn is incorrect. If you look closely, you can see a large cavity at the mouth's opening which resonnates. It is not in check with a normal horn flare. This horn is also not a copy of the Fostex design. The only remedy that I can see is adding a piece of wood (or whatever) that will smooth the flare opening and get rid of that large cavity. The only other issue is that, supposedly, the interior of the horn is also a polished finish. Inserting damping inside the horn will reduce the midrange glare. Good luck. __________________ Daze

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15th July 2009, 03:20 PM	#2
Scottmoose diyAudio Member Join Date: Mar 2005 Location: UK	The Concerti 108 is essentially Fostex's own FE108ESigma box design supplied free with the drivers, albeit smoothed out and (very prettily) built via the translam method. The basic Fostex design is OK, not great, & does suffer from a degree of boxiness, which the Gemme box inevitabley inherited (IIRC, when 6moons reviewed the Concerti, they noted this very trait). This might be compounded by the fact that they smoothed it out too: it's not usually a good idea to try smoothing manifold style horns, as they are usually designed specifically to take advantage of that style of construction. FWIW, I'd look to add a little extra damping in the back-chamber & throat, and you might want to try adding some in the base of the cabinet (just stuff it to the bottom down the mouth). That should go some way to reducing any unwanted midrange output & might ease the boxiness a little too.

15th July 2009, 06:02 PM	#4
chuyler1 diyAudio Member Join Date: Feb 2006 Location: Massachusetts	...for $3700??? Woah boy. Good thing I found diyaudio before anything else.

15th July 2009, 08:44 PM	#6
Richard1957 diyAudio Member Join Date: Jul 2009	Thanks for the stuffing suggestions, any particular grade of wool? BTW, I didn't pay $3700! (Thank goodness). Richard

15th July 2009, 10:53 PM	#8
Scottmoose diyAudio Member Join Date: Mar 2005 Location: UK	Who said it was a copy of the Fostex design? Copy means something is identical. I didn't say that. I said it was effectively Fostex's cabinet, smoothed out (not especially well IMNSHO -trying to do that with a manifold style design as the basis is looking for trouble on many levels) with translam construction. The terminus isn't ideal, I agree. Up side, it could be worse -the curve does continue round a ways, which will reduce the problem, and IIRC, many of these cabs. were damped around there with leather or similar. Re the damping material, it's going to have to be a case of suck it & see I'm afraid Richard. They all have somewhat different properties, require different densities, and have slightly different detail characteristics. If you want to go with wool, look for long hair sheep wool (suitably washed & treated of course...) Otherwise, it's good old dacron, fiberglass, preferably of the non-allergic variety (although you still need to be careful of course) etc. FWIW, don't rush it -make a change & listen for a while before deciding what, if anything, to do next.

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