fostex FW208N and FF85K

[Rudolf]

looking "on axis":

[Greg B]

That's totally cool!

I bet it sounds good too!




GB

[navin]

so if i now understand this you have only 1 10" woofer per channel. The half dipole is very intersting. I never thought of this.

Greg, why do you not like OB for midrange / tweeter drivers?

Greg, the reasons why I am taking more than the usual time over this project

1. I have an existing project in the works (presently it is waiting for new 8" woofers) so I am I wont have time or space to build anything new this this project is done
2. I have an exisiting stereo that is very satisfying soI am not without music.
3. The apt we intend to house this system in is not built yet. The builder is still working on it and at the rate he is moving it will take a while
4. In India we have duties and taxes that more than double the prices of all imported components. In fact the fact I live in MUmbai (Bombay) makes imports about 7% more expensive than if I were living outside The duties are calculated at 50% of CIF, VAT (called CVD here) is 28% of CIF+duites, and then Bombay has a duty of 5.5% of CIF+duty+VAT. So everything we import has to carefully thought out. Compunding this is the fact that our earning power is not the same as Europe, US, and other more developed nations.

Sorry If I an trying your patience.

[Rudolf]

so if i now understand this you have only 1 10" woofer per channel. The half dipole is very intersting. I never thought of this.

My dipole sub is inspired by a construction by Axel Ridtahler. His RIPOL (backside see attached picture) features a very narrow front chamber. Axel claims that by „loading“ the driver with the compact air mass in the front chamber Fs will drop significantly.

I started cutting the W-frame in half, because I wanted to move from mono bass to stereo bass. While the bass response in my room has become audibly better by splitting the W-frame, bass still comes from the center between both channels. I haven´t listened to all my CDs yet, but there can´t be many recordings that place bass below 100 Hz on a single stereo channel.

My facit: Having two dipole subs in the room helps, but driving them with dedicated stereo channels instead of mono seems to make not much difference IMHO.

Rudolf

[Greg B]

Navin,

I understand, believe me. I think I'm trying to convince myself as much as anything, as I'm very prone to analyzing things to death before I even get started.

Open baffle mids/tweeters are a little too diffuse sounding for me. This is totally a personal taste thing. Also, with smaller drivers a bit of an airspring from a Q .7 box, or what not, helps give them some extra subjective oomph at the bottom of their range. I do know that Kurt Chang at the HE audioasylum was very happy with the FF85 on open baffles.

As long as you have something to listen to while you figure this out it will be OK! I often have 3-4 systems in various stages of completion, with none working 100%.

GB

[navin]

Originally posted by Rudolf
His RIPOL (backside see attached picture) features a very narrow front chamber.

agreed completely. I may have accidently done this already.....I built a sealed box speaker then due to WAF turned the box so that the woofer faced the rear wall and moved the box to within 3" of the rear wall. with the floor as one boundary and the cabinet touching the wall on 2 sides the only escape for the bass was up. you lower FS but also sens this way.

Originally posted by Greg B
I'm very prone to analyzing things to death before I even get started.

Open baffle mids/tweeters are a little too diffuse sounding for me. This is totally a personal taste thing. Also, with smaller drivers a bit of an airspring from a Q .7 box, or what not, helps give them some extra subjective oomph at the bottom of their range.

Me too. tht is why i start the design of a system so much befre i will actually need it.

the OB on the ff85 in my proposed system is to widen what I am told is a very tight sweet spot exhibited by fullrange drivers.

[Greg B]

the OB on the ff85 in my proposed system is to widen what I am told is a very tight sweet spot exhibited by fullrange drivers.

This is related to the width of the drivers. With a 3" full range, you're not going to have to worry about beaming. The 8" cones have much more noticeable beaming. This depends on the driver too. The shallow cone FX200, for example, has a fairly wide dispersion for a big driver. The worst is a full range through a front horn. While this can sound great, it's too tight for my taste.

You may as well try the open mounting. A back could always be added later. It is a good idea to save the final cabinet finishing etc until after the design tweaking is done. Don't ask me how I know this.

GB