Fostex 108 Small Enclosure

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chrisb said:



exactly why would it be "fruitless"? - many of the small diameter Fostex drivers, and particularly the FE108E Sigma, are excellent from the upper midbass on up - and most "regular 2-way designs" XO are at least several octaves above the 200 -300 region - many right in the middle of the mid-range (gee, could that be one of the reasons they're hard not to hear?) ,


We actually agree. My - less than eloquently expressed - point was that by pushing the crossover frequency up, say towards 1500 Hz, you would utilize the Fostex driver as a regular tweeter. This does not take advantage of the wide - if not full - range qualities of this driver. Maybe not "fruitless", but definitely not an effective use of that driver.

This is one of the reasons I played with the idea to cross the Fostex at 300 Hz with the Peerless 830874, as experiment. The enclosure could be small-ish (16 liter alltogether) and almost the entire range of the Fostex would be utilized. The other, secondary, reason would be to move the crossover point to a less audible position, which I thought 300 Hz to be, but was not sure about.

As I contribute more frequently I may be able to further improve upon my English skills - it is not my first language - and state my "case" more clearly.

chrisb said:


Of the frequent DIY contributors herein, Mr Dlugos and the Planet10 clan have some experience doing exactly that - i.e. with several models of Fostex "FR" drivers and various woofer arrangements.


A nudge in the right direction? Are any of these ideas/designs available to the public? I did search, but internet on board a ship can be an exruciating experience.

chrisb said:


and Ron, Bob - this is New Years (second 4 day week-end in a row in my case) , if ever a there was a time for a DIYer to get hammered (provided all the power tools are locked out) this would be it. :drink: :angel:

cheers, y'all

There we are, again in full agreement...

Cheers back at ya!
 
I don't know how much you like highs, but I like having a tweeter crossed in ~ 10K w/ the108.
Just a cap on the tweeter, and letting the 108 roll-off on its own.

That's one of the reasons I like the swans, the base is about the size of a small (14" x 15") woofer, and gives the bass of a small woofer, with no electronics in the way at all.
Just looks like a base, with a small riser and a very small speaker on top.
 
serenechaos said:
I don't know how much you like highs, but I like having a tweeter crossed in ~ 10K w/ the108.
Just a cap on the tweeter, and letting the 108 roll-off on its own.

That's one of the reasons I like the swans, the base is about the size of a small (14" x 15") woofer, and gives the bass of a small woofer, with no electronics in the way at all.
Just looks like a base, with a small riser and a very small speaker on top.

I'd like to have a closer look at this design. Can I view it online somewhere?
 
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Ronmeister said:
This is one of the reasons I played with the idea to cross the Fostex at 300 Hz with the Peerless 830874, as experiment. The enclosure could be small-ish (16 liter alltogether) and almost the entire range of the Fostex would be utilized. The other, secondary, reason would be to move the crossover point to a less audible position, which I thought 300 Hz to be, but was not sure about.
... A nudge in the right direction? Are any of these ideas/designs available to the public? I did search, but internet on board a ship can be an exruciating experience.

Tysen (FF85KeN + SDX7) XOs actively at 333 Hz. We are working on an MTM using the 5" SilverFlute with the FF85 with passive XO). My current system is a set of Fonken + stereo push-push SDX7 at 100 Hz.

dave
 
planet10 said:


Tysen (FF85KeN + SDX7) XOs actively at 333 Hz. We are working on an MTM using the 5" SilverFlute with the FF85 with passive XO). My current system is a set of Fonken + stereo push-push SDX7 at 100 Hz.

dave


Thanks Dave, more food for thought.

Reviewing all the options I guess I'll start with further exploring the possibilities of crossing the Fostex & Peerless with a passive XO at 300Hz or so. The Peerless will definitely be vented, for the Fostex I would have the option to do either. Subjectively I'm inclined to let the Fostex breathe... Maybe Open baffle? Oops, can of worms... sorry...

I'm not sure to what degree Xmax is a challenge with Scottmoose's small MLTL (I don't have that particular software), but it would seem an issue with this driver in small vented enclosures. I'm still inclined to build both the mFonken as well as the MLTL (as test-cabinets) to have a listen.

All interesting prospects, I'm going to have to make some choices once I get back home. Thanks everyone so far for the input!

Ron
 
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Ronmeister said:
Subjectively I'm inclined to let the Fostex breathe... Maybe Open baffle? Oops, can of worms... sorry...

We use a short 10:1 aperiodically damped TL in Tysen.

Tysen-conceptX.gif


dave
 
Looks good Dave, worth a new thread! I have not come across many of these types of designs. I wonder if that is because it's slightly outside the norm or if the niche for this type of design is too small?

The TL and associated theory is a little outside my comfort zone - I'm more of a BLH and ESL person - I did make an attempt with a BR calculation:

The Fostex in a 2.1 L enclosure with a 14cm port dia. 2cm and the Peerless in a 14.0 L enclosure with a 14 cm port dia. 5 cm seems to work. F3 for the Fostex would be fairly low, around 120 Hz. I've attached a preliminare rendering of it. A fairly small, narrow enclosure.

Something to consider?

So, still moving my Fostex FE108ESigma around in the realms of TL, BR, BLH, OB... in search of a small enclosure...
 

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Ronmeister said:
worth a new thread

Planned ... i'm not quite ready for it yet

The Fostex in a 2.1 L enclosure with a 14cm port dia. 2cm and the Peerless in a 14.0 L enclosure with a 14 cm port dia. 5 cm seems to work. F3 for the Fostex would be fairly low, around 120 Hz. I've attached a preliminare rendering of it. A fairly small, narrow enclosure.

If you need to get that low, a highly aperiodic BR is feasible. The aim of aperiodic TL is to "suck" the entire backwave away. Since the goal isn't bass extention, the methodoly for the TL doesn't require any modeling. Try to get it a 1/4 wl at the lowest frequency required, keep it about the volume needed for Q as close to 0.5-6 when sealed (since some of these small drivers start out will higher Q, i just use a convienient size.

The higher the XO the closer the woofer wants to be the mid-tweeter.

dave
 
Ron, your plan shows the Fostex quite low on the front baffle ( unless you do all your listening on a yoga mat :angel: ) . If you don't want to reconfigure the dimensions, you might want to consider tilting the box back a few degrees to get the front driver's horizontal axis meeting ear level at or just forward of your average listening position.
 
chrisb said:
Ron, your plan shows the Fostex quite low on the front baffle ( unless you do all your listening on a yoga mat :angel: ) . If you don't want to reconfigure the dimensions, you might want to consider tilting the box back a few degrees to get the front driver's horizontal axis meeting ear level at or just forward of your average listening position.

True, however I don't have any floorspace available so they'd be placed on top of some heavy furniture. Were this not the case I'd certainly have to heighten the design, tilt them back, put them on stands or buy a yoga mat...

My Acharya tells me the Makarasana is an excellent pose for enjoying Diane Krall... so to speak...
 
Hello All,

When I started this thread I was hoping for ideas about how to utilize a Fostex FE108E Sigma temporary. My hopes came to fruition, thanks for all the input. I believe I'll construct Scottmooses mini MLTL. I can have the units break in whilst enjoying them at normal listening levels, using my ECL82... which I'll pull out of that giant cupboard...

Over the years I've produced several horns, Electrostatic Loudspeakers as well as quite a few tube amps. They're all over the world... all unique and made of unique materials. For my latest creations I've utilized this forum - without contributing, bad, bad Ron - which has improved the end-result. So thanks! At the moment I'm working on a CD player based on the CDM12 and Audio Note DAC1, an Aspen Lifeforce 100 based Solid State Amplifier and a pair of self-designed Electrostatics. These are the 'guys' that are taking the final floor space in my already tiny apartment (why live 'large' when you're at sea for 8 months a year).

That leads me back to the Fostex108E Sigmas which I purchased to build a pair of Frugal Horns (using Corian). My curiosity in hearing this driver lead me to this question. My suspicion that this driver is not suitable for small enclosures has been confirmed. As it is temporary I don't think I'll pursue the two-way system, which will require a good XO, more parts, more time put in etc. Unless there are more simple suggestions as to the use of this driver in a small bookshelf cabinet I'm going to assume the idea-well has run dry. I've enjoyed the experience of posting, and hope I can do so more often, maybe helping some of you out in your projects.

Finally, a shame about Diane Krall, I never liked Elvis Costello (now I know why)...

Ron
 
planet10 said:


My current system is a set of Fonken + stereo push-push SDX7 at 100 Hz.

dave

Dave - I found the drawings on planet10 for the push-pull woofer but no design text / story - I'd like to know the intended orientation / sensitivity / response in particular the skinny varient.

Are the woofers side firing or is the design a bipole? How would the perceived response change by changing the cabinet orientation?

planet10 said:


Tysen (FF85KeN + SDX7)

dave

I saw a drawing of a Tysen varient elsewhere, if I recall with a 108 - what's the loading for the top driver with the tapered / rear slotted enclosure? How do you achieve BSC in such a narrow cabinet?

I was toying with the idea of scaling it up, for me a D9nf in the top position, 200Hz XO and a push-pull woofer below although I assume I'd want larger cones to reach a 93db sensitivity

Much obliged as always...
 
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dpaws said:
Dave - I found the drawings on planet10 for the push-pull woofer but no design text / story - I'd like to know the intended orientation / sensitivity / response in particular the skinny varient.

Push=push if the design is mine. Which one, i probably have 2 dozen to pick from.

Are the woofers side firing or is the design a bipole? How would the perceived response change by changing the cabinet orientation?

At the frequencies these woofers are omnipoles no matter how you orient them.

I saw a drawing of a Tysen varient elsewhere, if I recall with a 108 - what's the loading for the top driver with the tapered / rear slotted enclosure? How do you achieve BSC in such a narrow cabinet?

Tysen uses an FF85KeN (3"). Bafflestep is dealt with in the nature of the XO. With the side firing woofer, the bafflestep we have to worry about is ~800-900 Hz. The XO is 1st order on the woofer, so that it's fall-off is gentle... the woofer naturally plunges at 900-950 Hz so it fills in the 333~850 Hz theoretical BS dip

dave
 
planet10 said:


An externally hosted image should be here but it was not working when we last tested it.


dave

Ahh I didn't recognise it - it's the acoustic loading of the top driver that has me curious as to what's going on

planet10 said:


Push=push if the design is mine. Which one, i probably have 2 dozen to pick from.

dave

Sorry, I forgot your Mac was so prolific.. It's the Extremis 6.5 shown here

http://homepage.mac.com/tlinespeakers/FAL/box-plans/skinny-PP-extremis-woofer.pdf

I assume these drivers have now been superceded by the SDX7's which you've referred to elsewhere. I assume because of the overall efficiency being relatively low I'd be utilising a larger diameter more sensitive pair of drivers....
 
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dpaws said:
Ahh I didn't recognise it - it's the acoustic loading of the top driver that has me curious as to what's going on

An aperiodically damped high taper transmission line. Damping is light behind the driver and gets progressively denser towards the terminus.

Sorry, I forgot your Mac was so prolific.. It's the Extremis 6.5 shown here

Woofers were meant to be side-firing on that one. SDX7 should slot right in with appropriate changes to the holey driver brace & cutout.

dave
 

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