OB with a small fostex and a large woofer

[Rafal]

Hi All,

I hope you can help me. I remember seeing last year a well documented design for the 2 way open baffle speaker using a full range Fostex FE126E or FE108EZ and a 15" OB suitable woofer. I am thinking of undertaking something like that but, unfortunately, can't seem to find that design anymore. Could someone point me to it or toward the thread discussing it?

Thanks,

Rafal

[Rudolf]

Perhaps you were looking for this one.
You may be interested in this new one too.

[adason]

this is closer
http://www.enjoythemusic.com/Magazin...er_project.htm

[adason]

or this
http://www.enjoythemusic.com/Magazin...oudspeaker.htm

[Rafal]

Thank you all.
Rudolf's first link is what I was looking for. The other designs are surely nice but the Jordan is bordering on too pricey and Feasterex on way our of my price range.

Now, has anyone built the fostex/woofer OB that may be able to comment on it's performance?

Thanks,

Rafal

[Godzilla]

How the heck does an OB woofer generate any bass at all? It's boggling my mind! I have a Fostex 168S (older style with wizzer) and could put it onto an OB... but should the bass support come from a boxed subwoofer or an OB woofer?

[ecir38]

Here is the thread that was started after MJK published the pdf. I am thinking of trying it out maybe early next year.

New MJK Baffle Article

[Rudolf]

Originally posted by Godzilla
How the heck does an OB woofer generate any bass at all? It's boggling my mind!

You simply throw away about 2/3 of the bass energy in the acoustical short cut, but live happily with the remaining.

I have a Fostex 168S (older style with wizzer) and could put it onto an OB... but should the bass support come from a boxed subwoofer or an OB woofer?

Depends: If you need that one note punch in your stomach you will be better off with a boxed sub. If you want to follow some delicate bass lines you never could resolve before - try a OB woofer (where I would recommend the H frame version).

[marec]

MJK's small OB's, using a 15A and 108ez has replaced all my other loudspeakers. In my small room (4m x 5m), I listen in the near field at lower levels. As others have said, the bass (down to about 40hz I guess), is more natural than any other speakers I have owned. The 108ez handles everything else with exceptional ease.
Rgds

[MJK]

Originally posted by Godzilla
How the heck does an OB woofer generate any bass at all? It's boggling my mind! I have a Fostex 168S (older style with wizzer) and could put it onto an OB... but should the bass support come from a boxed subwoofer or an OB woofer?

Like anything else, it is a series of design trade-offs and careful selection of appropriate drivers and dipole geometry.

If you use a single 8" or smaller full range driver on an OB chances are that the system will be rolling off at 100 Hz or higher and bass will be absent. Pair the same full range driver up with a high Qts 15" driver that is 6 to 10 dB more efficient and things start to come together. Getting down to 40 Hz on a moderately sized OB is not that unrealistic if the right design choices are made.

If you follow the same path using an H frame dipole, extending the bass down to 20 or 30 Hz is not that difficult. For dipoles that extend this low the design of the dipole is not that challenging and the distance to the rear wall starts to become the dominant variable for low bass output.