Fostex Horns and compression drivers

OMG - got it B A D!! Got the rest of the stack tonight ... I just won the
used, faded pieces in the first 3 images, and have the refreshed horns in the 4th.
I included the last image of a completed stack just for comparison.
but I have all the parts to do the full Fostex stack now!


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That's awesome! I'm really enjoying this thread, congrats on some cool gear.
 
Those supertweeters look like some that Radio Shack sold as well. I'm not sure if they were made by Foster, or if they were clones.
 
The rest of the Fostex parts have arrived. I assembled the stack (sans horns, for now) -
I have some minor fixes left to do on the horns, and need to build a crossover
before I can feed signal to the super-rare drivers.
God, the drivers are SUPER heavy!!

FOSTEX Driver - Horn Drivers D252
FOSTEX Driver - Super Tweeters T825


Fostex-Stack_5990.jpg

Yes, they are sitting on top of one of the recently new-to-me Heath "Valencias" -
thats another project for another time. I figure I'll pair the Fostex stack on top of
an ALTEC Model 15 Cabinet I have with a JBL 2214H for the woofer.
 
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All you need now is the Fostex L475 lab series woofers.
And finding Fostex cabinets and crossovers to do it in full would help, too!

But being frugal and not having the opportunity to source woofers, crossovers or cabinets,
I'll just have to make do with the compromises I have chosen!
 
And finding Fostex cabinets and crossovers to do it in full would help, too!

The LS/3 woofer cabinet is just huge 9 foot internal volume box,(8.82 cubic feet) with two huge ports tuned to 30Hz. If one had the resources to build a pair of cabinets, it would seem rather easy other than the cost of material.
You're doing what I've been wanting to do for some time, clone a Fostex LS series monitor. Except I was going to start from the woofers and go from there. I have the L475s, but I don't have the resources or the room to park a pair 9 foot cabinets. So that idea is scratched...

If you find cabinets, you'll also know where a pair of L475s are at. ;)

A guy can probably cobble up the proper crossover networks.
 
The LS/3 woofer cabinet is just huge 9 foot internal volume box,(8.82 cubic feet) with two huge ports tuned to 30Hz. If one had the resources to build a pair of cabinets, it would seem rather easy other than the cost of material.
You're doing what I've been wanting to do for some time, clone a Fostex LS series monitor. Except I was going to start from the woofers and go from there. I have the L475s, but I don't have the resources or the room to park a pair 9 foot cabinets. So that idea is scratched...

If you find cabinets, you'll also know where a pair of L475s are at. ;)

A guy can probably cobble up the proper crossover networks.

A gal probably could too! ;)

I just finished ordering parts from madisound and ... suprisingly, Radioshack.com (for 100 ohm wirewound resistors and 12-row euro type barrier strips for the ins and outs) ...
I'll mock it up on some plywood or such, with hot glue and tiedowns to secure the caps.
With any luck I'll have some sound by mid-march.

Hopefully, my wife will continue to be understanding, with the Von Schweikert VR-4s, the L212 (and Volkswoofer), the Heath AS-101s, and this Altec Model 15 Fostex project in the living room ...!!!
Never had any idea I'd have this many cubic feet of big boxes pending at once!

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I believe you already have 2/3's of it in front of you.

:)
Sure - but its the missing 1/3 that's critical for the woofie!

(I did presume the Mid and tweeter legs were basically the original design)
 
Sure - but its the missing 1/3 that's critical for the woofie!

(I did presume the Mid and tweeter legs were basically the original design)

But you don't own that woofie .

Here's a good thread for reference purposes ( re; using your 2214H woofer ).

Yet Another 4425 DIY

The salient info there is that jerv ( the OP ) ended up with a 1.5mH coil on the woofer ( instead of the 3.8mH that he started with ).

It's food for thought ( since large coils can get expensive quite quickly ).

FYI, stacking (2) Solen 1.3 mH ( 16 gauge air-cores ) gave me a final mH value of 3.6 mH ( due to the magic of mutual inductance ).
- Measured with Woofer Tester 2.

ie; Owning a bunch of smaller value coils ( & then knowing how to combine them to make larger values ) is a tinkers approach to the problem.

BTW; I was able to turn those (2) 1.3 mH air-cores into an @ 16 mH coil ( simply by inserting 1 bar of laminated transformer grade, grain-oriented stacked silicon-steel , through the combined coils' centers ).
 
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The salient info there is that jerv ( the OP ) ended up with a 1.5mH coil on the woofer ( instead of the 3.8mH that he started with ).

It's food for thought ( since large coils can get expensive quite quickly ).

FYI, stacking (2) Solen 1.3 mH ( 16 gauge air-cores ) gave me a final mH value of 3.6 mH ( due to the magic of mutual inductance ).
- Measured with Woofer Tester 2.

ie; Owning a bunch of smaller value coils ( & then knowing how to combine them to make larger values ) is a tinkers approach the problem.

BTW; I was able to turn those (2) 1.3 mH air-cores into an @ 16 mH coil ( simply by inserting 1 bar of laminated transformer grade, grain-oriented stacked silicon-steel , through both coils' centers ).


When I stack three Rockford Fosgate 2.0 mH, 16-gauge, air core coils, I get 8 mH due to inductive coupling. This provides a 160 Hz crossover to the 8 ohm 2241H 18". But it sounds better using less mH even though the mid is crossed over lower than that.

The moral here is that depending on the speakers and coils, and way they are stacked, YMMV.
 
Okay, after being NAGGED to give it a try, I popped the back covers of the Heath speakers, unhooked the internal horns,
(Remember I said I dumped a pillowfull of polyfill in and extended the bass response on the Heaths). Anyway, I
ran the HiPass crossover leads out the back, closed them up, slipped the Teak horns on top and connected them in ...
Then put on Joni Mitchell again - Amelia, then Hejira - - VERY SWEET - these are staying hooked up like this for a while!

Great Holy moly!! What excellent sounding horns!!

Going back to listen some more!


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When I stack three Rockford Fosgate 2.0 mH, 16-gauge, air core coils, I get 8 mH due to inductive coupling.
This provides a 160 Hz crossover to the 8 ohm 2241H 18". But it sounds better using less mH even though the mid is crossed over lower than that.

The moral here is that depending on the speakers and coils, and way they are stacked, YMMV.

That sounds like a great approach - so - how do I measure the inductance of a coil so I can stack them and know what I have - or -
unwind some turns to hit a desire value?
For example - how can I detune a 2.0mH coil to 1.8mH ?
 
For example - how can I detune a 2.0mH coil to 1.8mH

I bought a fairly cheap LCR meter...you can measure inductance and slowly unwind cutting segments, measuring for the value you want. Just don't go too far...but even then if it's 1.78mH compared to 1.8mH, that's still rather close. I did the same thing unwinding a 2.0mH coil to 1.8mH.
 
I bought a fairly cheap LCR meter...you can measure inductance and slowly unwind cutting segments, measuring for the value you want. Just don't go too far...but even then if it's 1.78mH compared to 1.8mH, that's still rather close. I did the same thing unwinding a 2.0mH coil to 1.8mH.

Amazon has a "Proster" LCR meter for $30 - is that price in line with the "cheap one" you bought?

https://smile.amazon.com/Proster-Capacitance-Inductance-Resistance-Self-discharge/dp/B071WNNYQT/
 
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