New box for the Fostex 103's

[Cal Weldon]

Actually I used the Foster 10F3 which according to my friend Dave is the precursor to the Fostex FE103. These drivers have had the full planet10 treatment on the cone, basket, magnet and phase plug.

The idea for the box came from Dave and Scottmoose from this thread:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=96937

I used extrapolation to design the cabinet and my ears to test. I am quite pleased with the results. I have listened to a lot of old favourites and I must say, for weeny little drivers they're great. I am thinking of matching these with the Shadow (2 X Extremis 6.8) that you can see in the other thread.

 

[Cal Weldon]

Here's the end opposite the horn. Don't worry about it not looking even. I took the pic before I tweeked the vent pieces into place. The vent length is 34" before it enters the step horn. Vent is 1/2" until it reaches the back where it becomes 3/4"

EDIT: OD is 24" X 6.5" X 6.5"

 

[Cal Weldon]

Brought them home to do a side by side comparison with some other sets and I have to say, this is an impressive driver when matched with the Shadow. Quite a good combination.

 

[gmilitano]

Cal, looks good. You guys seem to have too much fun building speakers in BC! Keep it up.

How is the low end? Those small vintage drivers often have a highish Fs.

 

[edjosh23]

Cal,

Any chance for a drawing? I'm a little confused.

Thanks,

Josh

 

[Cal Weldon]

How is the low end? Those small vintage drivers often have a highish Fs.

When Dave reworked the driver he said it actually rose and now sits at about 110 Hz IIRC. The addition of the Shadow woofer looks after what they can't do. I also have a 150 mfd cap on the Cal Jr's to help protect a bit.

Any chance for a drawing?

The drawing is down at Sonia's but I did a layout on the back of one unit. The zig zag vent at the top of the cabinet is 1/2" until it snakes it's way up and to the back where it opens to 3/4" and drops down the back into the horn.

To make sense of it, remember to turn it 90 degrees. The driver is on the righthand side.

 

[edjosh23]

Cal,

its a little hard to tell, is that a terminus at the top?

Thanks,

Josh

 

[gmilitano]

When Dave reworked the driver he said it actually rose and now sits at about 110 Hz IIRC. The addition of the Shadow woofer looks after what they can't do. I also have a 150 mfd cap on the Cal Jr's to help protect a bit.

At 150uF, I imagine electrolytic is the only practical choice. Have you found that cap affects the sound quality?

For the XO experts, will being 90 degrees out of phase with the woofer be noticeable?

 

[Cal Weldon]

Oops, I forgot to mention there's a back that butts up to the left side. That last 3/4" on the left is the vent.

 

[edjosh23]

Cal,

OHHH! Thanks, got it. I like!

Thanks,

Josh