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DRCope 8th March 2005 04:08 PM

Buschhorn MkII w/ Foster W422, aka Fostex FE103A
I know a few of you have used the older Foster driver with alnico magnet in the BHorn II, and since I now have a pair coming my way, I was wondering what tweaks you have found work best with this particular driver. There's next to no specific info on this driver out there, and I do plan to do some experimenting of my own, but I'd love to do so with a base of information to stand on to begin with.

The speakers will be wired with Audio Note SPa silver cable and driven with a 2A3 stereo amp I have yet to build (Quest Silvers applied gently in the mean time), and an Audio Note Kit Pre or M3 Phono at various times. The front end is either an AN CDT Two MkII and DAC 3.1x Balanced or a Voyd Table, AN-1S arm and IQ3 or IO 1 cartridge and AN-S3 mc xfrmr.

chrisb 10th March 2005 01:20 AM

FE103"A" in BhornII
If you bought the drivers from Dave Dlugos (Planet10) without the wooden phase plugs, shame on you. :xeye:
If not, order a set of the plugs straight-way.

He and I have used this driver in various enclosures over the past few years, ranging from Bert D's cute little folded TQWP, Fostex's factory recommended ( Nagaoka designed) BLH "type", to the Buschorn. I may have missed a design or 3, but I think it's dafe to say that the best we've heard them is in the BHII.

Since you're reasonably assured the drivers are fully broken in (after only 30 or so years), there's really only a couple of tweaks needed;

1) Did I mention phase plugs? These made a huge difference in my system ( EL84 triode/PF monoblocks); opening up the midrange significantly and dramatically improving the off-axis dispersion, image stability and depth. We experimented with "helper" tweeters above 10K, but with any reasonably decent front end, and a SET as transparent and dynamic as EL84 or 2A3, it was hardly worth the trouble. (300B amps could be another story)

2) Apply a thin layer of Duct Seal ( Ideal Industries 31-601) to the stamped frame, in particularly filling the gap between the rear of the basket and magnet loop. The goal is to make as smooth a transition as possible. Maybe Dave can post a picture of a suitably modified driver.

The enclosures themselves benefit from sand filling of the large internal and lower fold voids - a little harder to install after the boxes are glued up, but where there's a will .... I used "Tru Grit" (really) sand-blasting abrasive.

If you haven't built the boxes yet, don't waste your time with any material other than Baltic Birch. Due to the amount of bracing from the internal folding panels, you could probably get by quite nicely with 15mm (approx 5/8"). A small hardwood or 3/4" brace across the final mouth of the horn doesn't hurt either, and makes for a convenient hand-hold when moving.

The trickiest part of voicing the speaker is damping the compression chamber. Some folks have experimented with blocking it off entirely when using the FE108E Sigmas, which I had myself, until very recently. I didn't care at all for the results, and went back to about 2/3 stuffing with 1/2" acoustic felt (also from the "frugo-phile" audio recycling guru), but YMMV.

As for placement, I have been happiest over the past 5 years or so with a placement diagonal across a room corner; i.e. the line forming the front baffle of the enclosures forming the base of an equilateral triangle, with the corner as the apex.

Due to the rear mouth of the BHII, you'll need to experiment with distance from the side walls ( I'd suggest starting around .5 - .75M) and toe-in.

Enjoy, and smile when your guests ask where the "other" speakers are

DRCope 10th March 2005 02:26 AM

Oops, not Foster - likely panasonic/matsushita
Actually, these aren't coming from Dave, but I tripped over his site, and it was in ordering the phase plugs that he informed me that the drivers weren't what I thought they were. Once the drivers get here, I'll measure and order up.

Nope, cabs aren't built yet, and I've read through your site, Dave's and a few others. Baltic birch was a given from the get go. I don't want my music to sound dead, which is what I always hear from MDF.

Sand is in the picture, as will be outrigger spikes since this speaker can't possibly be really stable on carpet.

Yeah, I can see from reading up that fine-tuning the size and damping of the cc will be critical. One side will be screwed on and finishing will have to wait a while. ;-)

Strangely enough, the speakers I sell in "real life" are designed for corner placement as well, which always gets the high end crowd's shorts in a knot.

These speakers will probably go with me to the Great Plains Audio Fest April 29 - May 1 in Tulsa OK. By tomorrow the beginnings of the site for the show will be up at

planet10 10th March 2005 02:29 AM

Re: Oops, not Foster - likely panasonic/matsushita
Welcome o the forum Dave.


Originally posted by DRCope
Strangely enough, the speakers I sell in "real life" are designed for corner placement as well, which always gets the high end crowd's shorts in a knot.
More later... gotta go fix a set of isophone coaxes...

It is syncronystic that the local hifi dealer is a big AN fan/seller... Chris has built up a couple of the boxes for the kits.


Cal's 10F3s with the major teaks....


planet10 10th March 2005 07:03 AM

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And speaking of Cal's FE103As.... here is a pic of them in his new "Jimmy Buffet" 4-ways (or maybe 3.5 way). They are actually just place holdng for a pair of Coral 103As which -- unmodified & with a bit of "stiff surround syndrome" -- he liked better than the tweaked Fosters. His Corals are over here for surround resurrection and tweaks including phase plugs.

Dave's 103As, to my best guess, are also Corals and very similar to Cal's, the prime difference being the baskets.

Also of note in Cal's JBs are the Foster inverted dme tweeters. These are the only ones i have ever seen and look really nice (and Cal says they sound really good too)


planet10 10th March 2005 07:20 AM

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Here is a pic of the Corals (i'm going to call them that, but still have some suspicions they may actually be Panasonic/Matsushita -- note that these were the guys that pushed FR tech the furthest of any of the big 3 OEMS)... note what looks like may be the points of ribs sticking out from under the dust cap)


planet10 10th March 2005 07:22 AM

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Here is a pic of a larger driver with clearer ribs... if after removal of the dustcap there are ribs in Dave's 103As that is a very good thing and makes them very special...


planet10 10th March 2005 07:24 AM

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And here for comparison are some known Coral 103As -- these are 8 ohm Sony labled ones, Cal's are 16 ohm Monarch labeled ones.


planet10 10th March 2005 07:26 AM

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And Chris' B-Horns (before finishing) with Foster FE103As


planet10 10th March 2005 07:27 AM

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And while showing variations, an Akai labeled Panasonic OEM.


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