filters for Fostex 208 in BLH

[brady]

Hi All.

I saw in a German site a speaker box looking like the standard Fostex design and using a Fostex 208 and T90.

The parts list showed :

1 x 0.68mH
2 x 0.22mH
1 x 0.05mH
1 x 1.00uF
1 x 68.0uF
1 x 8.20uF
3 x 6.8 ohms

But I couldn't understand the language and there were no skema. Does anyone have any idea of what goes where? I would imagine a notch filter somewhere 3kHz to 4kHz, perhaps... and a zobel to bring down low freq impedance a bit.

TIA for any guidance.

[talaerts]

Can you post a link?

[brady]

Strassacker: Lautsprecher - Boxen - Selbstbau

and thanks for taking the bother. i have this driver in a backload. but just using a notch at around 3300 - 3500 Hz

[planet10]

<rant>Those guys make it impossible to post a link to something, any link gets redirect to the home page. They must loose a huge amount of traffic because its not worth wading thru their site to find what the goasl was.</rant>

dave

[adamt]

Interesting.

I built a horn with that driver 3 years ago that I still enjoy today. I have tried just about every passive crossover to pad the peak with varying degrees of success.

My conclusion is that any filter just sucks the life out of the music. Sure, I have a filter for the tweeter, but nothing for the driver. I put up with the occasional cd that causes a bit of boom, or some sibilance.

In the end none of the variations of filters I tried improved the overall musicality of the speaker. They might control the bass, or pad the trebble, or give a more even frequency spread, but none that sounded like good music to me.

Just my 2c

good luck

[planet10]

My philosophy is to try to fix the driver, not bandaid with filters.

dave

[talaerts]

The direct link is here: Lautsprecherbausatz BK208 von Hobby HiFi
(For this website, you have to open the link in another page to see the direct link)

It's from the very good Hobby Hifi magazine.
Now, it is currently not easy for me to find the magazine back, but I do remember that they tested this horn speaker and found the fostex recommended filtering of the supertweeter with only a capacitor not satisfying enough. Hence, they also rolled off the full range speaker at the high end, tamed the sensitivity difference, and I seem to remember they did another correction as well - all using high quality filter components.
In contrast with the full range purists, I have no problem with (well-chosen) filter components.

[brady]

Talaertes, Dave ... thanks

Lookingg at the number of caps and coils, a suspect a wide band notch filter. Not just centered on one specific freq.

Dave, yap, I applied damarr varnish to the whizzer and that helped. Am sure your method is far superior. But taking outmy 208 and shipping it outside the country is outof the question...

I had to go for a notch to tamp down a "shout" somewhere past 3kHz. Eva Cassidy's Blues In The Night, Janis J's summertime, etc

[tubemax]

HI Brady, I have one drawing of this xover...

Regards, Max

[talaerts]

For those with rusty German:

I remember the picture of L1: a very high quality copper foil/strip coil, for maximum transparency.
R2,R3,C3,C4,L3,L4 are for impedance correction to make life easier on tube amplifiers. The quality of them is less crucial, and not necessary for solid state amps.

The difference between Hobby Hifi magazine and the Art of Sound kit dealer filters is that HH adds R1. HH clearly found the sound too bright. The table shows the difference for different values of R1.

The fostex fliter was only C1 on the tweeter.