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.
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.
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.
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.
Scottmoose said:
And made it out of MDF which has higher energy storage which will further exacerbate things.
dave
Thanks for the stuffing suggestions, any particular grade of wool?
BTW, I didn't pay $3700! (Thank goodness).
Richard
BTW, I didn't pay $3700! (Thank goodness).
Richard
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.
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.
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.
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.
You might read this thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=137103&perpage=25&pagenumber=1
You can try out the suggested method on your box, without adding any other materials. Using a clear, tack tape from the scrap book section in female hobby stores will be more than good enough for a trial. See Alex from Oz's posting a few into the thread, to get a calculator for the process.
Bud
http://www.diyaudio.com/forums/showthread.php?s=&threadid=137103&perpage=25&pagenumber=1
You can try out the suggested method on your box, without adding any other materials. Using a clear, tack tape from the scrap book section in female hobby stores will be more than good enough for a trial. See Alex from Oz's posting a few into the thread, to get a calculator for the process.
Bud
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