[Abby356]

Gents (and Ladies if you're out there),
     I'm in the midst of my first diy OB experiment and am looking for some advice from the "Darkstar" folks and other OB veterans. I am a constant "Lurker" (learner) and obviously infrequent poster, as i still think i have more to learn and little to contribute. Simple, elegant, wood speaker designs, single drivers and esoteric amps/sources seems to be my thing. Think Mid-Century modern. I own a few commercial fostex based speakers and chanced upon a pair of used Fostex F200A's about a year ago that I had planned on using in a 2-way crossed with a compression/waveguide. After researching OB's recently i woke-up one morning and decided to try the JE Labs baffles with the F200a's. A sheet of 3/4" alder plywood (which i had easy access to) and a couple of hours later i heard a remarkable speaker experiment underway.
     For Background the system in its current configuration:
     -Almarro A318a / Trends with PIO caps as power amp
     -Electraprint PVA
     -Sony PS1's / Sony CE595/ Paradisea+ Dac with Toshiba and other cheap transports
     -Speaker Cables WhiteLightening Patio cord / Guerrilla/MAC IC's / Zu and various PC's
     -The listening room is small (14'x12'ish) speakers are nearfield, 3.5' out-1.5' in and sharply toed-in
     -Room treatments are (6) diy fabric over 4" Rockwool panels in the typical places

I am looking for some advice tweeking the baffles. The back of the baffle has been lined with 3/16" cork and i have recently added Fostex FT96H supertweeters firing backwards currently crossed with a .22uf PIO cap (also have tried .47 and paralleled). Volume matching is via a RatShack transformer based mono volume control per speaker. My primary concern is with the typical Fostex style mounting of the driver. From the front with the stock gasket doesn't seem ideal. Especially with the extra thick cast flange on the F200A. Research seems to point to the middle (front to back) of the baffle as the best sonic solution but I'm not sure how to get there with this driver. An adjustable mounting plate for various drivers would seem to be a great future proof solution...magnet mount....hmmm. I probably have a million-and-one questions but I'll start with this one. Thanks in advance for your time and responses. The knowledge/experience i have gleaned from this forum (and others) has been a real steal for me. Regards, Daniel.

[DanTheMan]

Sounds like your off to a hell of a start.  Most OBers do prefer the magnet mount.  Hopefully you try it out and let us know what you think of the difference.

We need some pics.  Cheers!

Dan

[Rudolf]

I am looking for some advice tweeking the baffles. ... My primary concern is with the typical Fostex style mounting of the driver. From the front with the stock gasket doesn't seem ideal. Especially with the extra thick cast flange on the F200A. Research seems to point to the middle (front to back) of the baffle as the best sonic solution but I'm not sure how to get there with this driver.

Daniel,
don´t worry too much about that flange. Its influence will be restricted to wavelength smaller ten times the flange thickness - calculating with a very safe margin. If I estimate the flange thickness at 5 mm, this would lead to a frequency of 6800 Hz - where the F200A already is beaming heavily.
Countersinking the F200A is ia a good idea nevertheless. It would help to free the backside of the basket. May be you should double up the baffle with a board of the flange thickness.

[Abby356]

Sounds like your off to a hell of a start.  Most OBers do prefer the magnet mount.  Hopefully you try it out and let us know what you think of the difference.
We need some pics.  Cheers!
Dan

Thanks for the support Dan. On a new Vista based laptop that I'm still trying to figure out but will get some pics up ASAP. My concern with the magnet mount is all of the congestion it would add the the area behind the baffle. Would adding a baffle "floor" to tie into negate the benefit of the "infinite" baffle of the floor ?

don´t worry too much about that flange. Its influence will be restricted to wavelength smaller ten times the flange thickness - calculating with a very safe margin. If I estimate the flange thickness at 5 mm, this would lead to a frequency of 6800 Hz - where the F200A already is beaming heavily.
Countersinking the F200A is ia a good idea nevertheless. It would help to free the backside of the basket. May be you should double up the baffle with a board of the flange thickness.
 

Rudolph, that's exactly the kind of technical info,  beyond my current understanding, that i was hoping to get from this thread. I was thinking along the same lines of adding another layer to the front of the baffle the same thickness as the flange. Nice website too...unfortunately i took Spanish in college. Have any experience with the semi-affordable Supravox Sig Bicone on OB ???
Lets say i wanted to add a coil to the F200a and turn the FT96H's forward (to reduce the well known beaming)...how would i go about time aligning the drivers ???

Any OB Tone Tubby alnico experiments on the ground out there ???

Thanks guys. Daniel.