Fostex FE208-SOL box?

[vcelkamaja]

Hi, I was lucky to get 2 Fostex FE208-SOL limited editor full range speakers What I want to do is to use them in a single driver BLH enclosure.

While I looked into Half Chang, Solo206 and Dallas II plans I'm not sure which one to pick - I think all 3 of them were originally designed for "standard" FE206 EN.

Can someone please help me to decide or even recommend a different box? What I'm looking for is a dynamic, wide space, balanced bass system for jazz and vocals.

Fostes FE208-SOL spec here: Fostex FE208-Sol - 8" Large bande

Thanks

 

[Scottmoose]

Definitely not the former (unless you have a high output impedance amplifier or the equivalent series R, either of which are pretty much mandatory for this unit if it's to be used without compound loading given the 573.33Hz mass-corner frequency). I designed it for the FE207E with the then-current FE206E as an option provided appropriate correction was made.

The Solo 206 ismore or less a stretched BK series horn; it's OK but not ideal for this unit. Dallas II would probably be the better bet of the three you mention. Otherwise -realistically you need a bigger horn, e.g. my Vulcan or Kirishima. A simple pipe-horn would also work, again assuming the necessary amplifier or series R, and that you can position them suitably in the room.

 

[vcelkamaja]

Thank you Scott. Unfortunately Vulcan and Kirishima are too big for me.
So I will likely proceed with Dallas II as you recommended.
Two questions:

1. Are there any thomgs you would recommend as mods of current Dallas II to fit to FE208 SOL. I think it was originally designed for FE206 EN.

2. Series resistor - this driver is 8 ohm and I plan to use with some SET amp based on 300B, 2A3 or so. Can you please elaborate on why do I need a resistor and how do I calculate its value?

I have to note that this is my first full range BLH speaker so any suggestion is more than welcome

 

[Scottmoose]

1/ It was designed for the FE206E (earlier version). Not really, I didn't design it and it won't function as well with the 208-SOL as with the design unit; technically you'd need to change the rear chamber volume and horn profile. But it's still likely a superior option as-is than the other two enclosures you mention with that driver.

2/ You're unlikely to benefit from any series R with a 300b amplifier; it will probably have a relatively high output impedance, and most of them don't have very much power in reserve so you'll want to keep system sensitivity up.

 

[zmajz]

Well, this is my experience:
I had built Dallas II strictly by the R. Clarke plans for FE 206e using that driver and must say that it is the best BLH for it (heard some other BLHs for 206e, not even close to it) and it happened on first Croatian Triode festival in 2010th compared it directly to FE208ez (sigma) in Jericho horn (Bernd Timmermans from Hobby Hifi) and must say that they were very close...
But, FE28ez used Fostex helper Tweeter (don't remember the model but the price: arond 200 US$) and it was great sounding speaker. 208ez is better speaker than 206e but needs tweeter and that is minus for me. On other hand, 206 in Dallas II was better in general (must be subjective, I think), no xover and tweeter, that's it. Fe208 in Dallas II was not good sounding (at list, not good as it can be), Jericho horn is great for it.
I do not know to which of this two drivers is FE208sol closer, but do not use it in Dallas II, it does not match to that BLH. Dallas II is projected for 206e and 206e only, not even for 206en!
My 2$ and 55 cents.

 

[GM]

FYI/FWIW/YMMV: a bog simple prosound type parabolic BVR [AKA 'scoop bin'] in ~49 L, sims plenty loud on two clean watts even in 2pi space with a total of 8 ohms output impedance and/or non inductive resistor, or less as it's moved near/at a wall or probably none if in a corner. Add more damping to 'taste' for a more HIFI/'girl and a guitar' presentation unless Joan Jett or similar is more your style .

GM

 

[vcelkamaja]

thanks for all comments and feedback. I won't be able to design specific box for for FE 208 SOL and I'm rather looking for something already available (that is why Dallas II, BK-20, Half Chang or Solo206) which would best fit to 208 SOL driver.

As it seems Dallas II seems to be the best option out of available designs I tend to prefer going forward with it. Not sure if any modifications to the current Dalls II would help (electrical or mechanical).

 

[vcelkamaja]

Ok so my FE 208 SOL arrived and hey are impressive - huga magned, quite heavy

There is an official Fostex recommended plan of BLH showing dimensions 900 x 350 x 450 mm:

ヤフオク! - ☆FE208-Sol推奨キャビネット「準両面シナ仕様」...

Also I found some kits (Japan only? )
Eg this one (900 x 265 x 425 mm)

Google Translate

Or this one (876 x 300 x 450 mm):

Google Translate

Google Translate

They seem to be more compact compared with Dallas II. Any idea what would it mean for the sounds? Less bass?

I like the smaller size and something around 900 x 300 x 450 mm would be great).

Any comment or suggestions?

 

[vcelkamaja]

Any opinion please?

 

[DrBoar]

There is a 2008 version of the Jericho horn very similar to the first but it has internal helmholtz resonators to remove some peaks.

 

[GM]

They seem to be more compact compared with Dallas II. Any idea what would it mean for the sounds? Less bass?

I like the smaller size and something around 900 x 300 x 450 mm would be great).

Any comment or suggestions?

Correct.

Your ~120 L net volume [Vb] is ~2% eff. = ~95 dB/m/40 Hz, so adequately sized for 40 Hz if corner loaded and driven with a matching impedance amp, i.e. has a damping factor = 1, so either the appropriate SET amp or an 8-10 ohm non inductive resistor in series.

Moved out of the corner and it will only load down to ~57 Hz.

I'm not familiar with designs on the net beyond some folks saying the Oriental designs in general don't perform all that well and some horn designers not being impressed with them overall and I'm not set up to convert my Hornresp sims to construction drawings, especially to try and fit it to a specific shape.

GM

 

[GM]

There is a 2008 version of the Jericho horn very similar to the first but it has internal helmholtz resonators to remove some peaks.

Could only find this one [other type Jericho horns are currently 'hogging' Google search]: Jericho Horn Speaker

GM

 

[planet10]

… Dallas II ... I think it was originally designed for FE206 EN.

Originally designed for the FE206e.

dave

 

[planet10]

 

[GM]

Which plan is this?

GM

 

[planet10]

That is the factory recommended one linked above.

dave

 

[Scottmoose]

It's not up to Dallas II but could be worse. The two other plans linked to don't have dimensions but roughly speaking -well, the first is dodgy, the second is tuned low, but given the limited volume gain is conspicuous by its absence. Contextually speaking possibly OK for the intended requirements; probably less so for most outside of Japan.

 

[vcelkamaja]

To GM:

“Your ~120 L net volume [Vb] is ~2% eff. = ~95 dB/m/40 Hz, so adequately sized for 40 Hz if corner loaded and driven with a matching impedance amp, i.e. has a damping factor = 1, so either the appropriate SET amp or an 8-10 ohm non inductive resistor in series.

Moved out of the corner and it will only load down to ~57 Hz.”

Can you please help me to inderstabd this? All those BLH are front firing so how does the corner loading influence it?

Also how is the amp impedance affecting this horn performance? My plan was to use it with SET amp with matching output transformer - 8 ohm in this case (FE208-SOL is 8 ohm)

 

[vcelkamaja]

I tend to prefer one of those designs due to dimensions now:

Google Translate

- 1000 x 290 x 450 mm
- horn legth 210 cm

Or smaller:

Google Translate

- 900 x 260 x 425 mm
- horn length 186 cm

Do you will they work? Is the bigger one worth of its dimensions? Better bass?

 

[DrBoar]

Most basshorns both work as pipe resonators and horns. To work as a horn it has to both be long enough and have bieg enough mouth area. The depicted horns are quite long but have small mouth area so the mouth area is the limiting factor for bass. To complicate things further: a horn placed close to a corner works as horn with twise the mouth area placed at a wall. So in this case placing the horn close to a corner will make the horn go a bit deeper in the bass.