Foster E100T10 ribbons - what quality?

I bought a pair of old speaker boxes with the plan of refitting them with a FR single driver. (The volume was right.)

The woofers and mids were shot - rotted foam.

There are however, two (2) Foster E100T10 ribbon tweeters, apparently in good condition.

I have found the tech specs, here:

What sort of quality were these ribbon units? Is it worth using them as a basis for another project?




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ok, the tweeters arrived from parts express
they look cute
they would look even better it the screws were other way around
four screw heads are in the back, nice an flat, and sharp screw tip is pointing to the front
but what's most important is how they sound
I am thinking of making short line array of eight 4" fullrange drivers with this tweeter in the middle
I got plenty of those aura fullranges, I got to use them :)
Hi @adason, it's most likely that you should mount them inside the cabinet. You could make a nice trim in the front that leads to the face place which is behind.

Often, the plane of the tweeter should be aligned with the back of the woofer's or mid-range anyway, so it makes sense to me they are back-side mounted.
Absolutely yes. They are meant to be a little back. I will make angled edge on the sides of baffle. Kind of like true ribbons have.
Those little aura i have are 16ohm, so i will have four above the tweeter, parallel to give 4ohms, and four below same way, and those two sections in series, resulting in 8ohms, matching the tweeter. Will see.
took me a week, but I finished the speakers, finally wired it and tested
no measurements yet, but they sound awesome, eight little fullranges with tweeter is good combo
I used 2.2uF MP cap on tweeter, in opposite phase, nothing on fullrange drivers so far, I will check phase to make sure tweeters polarity is right.
First I need to make a stand/foot, as this is very narrow speaker which needs solid footing.
Finally I can confirm, tweeters sound just fine.
More later.
here are some from the build
I started with the front baffles (just one coat of paint)
added sides, inside ribs for strength
all covered in gorilla glue, light but strong
glued the speakers, some more paint
today wired all together
playing on F1J (in progress) running with balancing trafo on input
F1J likes 8 ohms fullrange (8 for higher efficiency) with just one cap on tweeter
very promising, just the foot for stability and few more paint coats


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an old aura
dustcap was concave, but my fingers had other idea :)
seriously, those are the ones sold by parts express 50 per case for $20
dave, you have them likely too, they are good sounding
there is quite a few with scratching voice coils, so I had to test it by vigorous pushing in and out
hence dustcaps are pushed in


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Hi Andersonix, very happy with the tweeters, I measured them, they can be considered supertweeters. Very extended, quite wide beam, not beaming at all. I wish I paired them with better midrange. They deserve better. They sound like hiquphone.
I ordered another pair, since they are bargain.
However, dipole no.
If you want dipole, get GRS neo3 (without back cup), its direct copy of B&G (which is back on market, but expensive).
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Good score! Your post 5 makes it look like they're usable above 5k and quite flat to 40k too?

I'm using the PLA-114-6 planar tweeter. It went on sale at Madisound for $29 and has a removable back cup to make it a dipole, and I've been horsing about with a Peerless HDS and an old active xo, having a go at an Alon homage.
I reinforced the back side of the line array with small wooden sticks, since foam core was a little wobbly. I gave them nice big stands on the bottom. They still need some painting, but that can wait. They sound nice, big open soundstage, nice imaging, mainly because of the nice foster planar.
Considering this was just for fun project, they are pretty good. They are easy load 8 ohm for any amp. I am biamping the system. This used to be nice and clean guest room, now its pretty much stuffed with audio.


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Glad you are experimenting with the Fosters. I am looking to substitute these in place of a couple of old 2 inch, round, horn tweeters. My thoughts are to mount them on surface, building a 1/4 inch thick template and surface mounting it.
Do they need space behind them?