[Luigi]

I had my DIY Penguin speakers stolen in a break in recently (Hempcones in a bass reflex cylinder). So now want to create some new transducers, but would like to try some open baffle speakers.

I have a pair of FE206E Fostex on hand, so will use them initially. Have a pair of 12 inch open baffle bass units to supplement.

Cutting to the chase, could anyone recommend an approximate baffle size for these 8 inch drivers? I want to make the baffle as narrow as possible, but am happy to do wings both to aid baffle size and support the baffle.

Can the wings be fixed at a predetermined angle or do they need to be on piano hinges?

Does the front baffle need to be angled at all or is vertical just fine?

Hope this isn't covering ground already trampled to death.

I have a friend with a CNC miller so he can do just about anything with wood. Just want to get some music going again.

TIA for any advice given. I intend to replace the Fostex drivers in the end with more appropriate units for open baffle use. I guess Visatons or Hempcones.

Cheers

Luigi

[JohninCR]

Luigi,

Sorry to hear about the break in.  I used my 206's on OB for almost a year.  They have such a low Q that their baffle makes little difference except in the higher frequencies, so it's easiest just to experiment using a minimal baffle to mount the driver and tape pieces of cardboard on to help decide on the size and shape.  How you integrate the bass augmentation is the key, and it will need to run up to 200-300hz depending on your XO slope.  I never could get past that one ear piercing spike in frequency around 3khz that made my 206's fatiguing.  Some day I plan to attempt serious whizzer and cone mods to correct it, because it's a great driver otherwise, and like any driver, it sounds even sweeter on OB.

[Luigi]

Thanks for the reply JohninCR.

The reason I ask about baffle and wing dimensions is that I intend to replace the Fostex 206E with Hempcone FR8 full range drivers in the near future, and these are meant to work better in open baffle format. They also slot into the same hole as the 206Es.

So again, anyone have any idea on minimum baffle size with the FR8 full ranger (or the Visaton B200s) in mind? Or know where I might be able to find such information?

Thanks
Luigi

[SET Man]

Hey!
   Luigi, sorry to hear about your break in man.

   I see OB  FE206E eh? I would never though of using that driver since it got such a low Qts. But than again you'll never know.

  Let's us know how it turn out okay.

Luigi,

 ...I never could get past that one ear piercing spike in frequency around 3khz that made my 206's fatiguing.  Some day I plan to attempt serious whizzer and cone mods to correct it, because it's a great driver otherwise, and like any driver, it sounds even sweeter on OB.

Hey!

   I have Fostex 167E driver I stuffed in 0.5g of Acousta-stuf around the whizzer cone and it help with that annoying peak

   Just puff it up make it into a long thread and than use stick to put it in. I pack it in pretty tightly. I think you need a bit more with bigger driver.

Take care,
Buddy

[JohninCR]

Luigi,

The same applies, only the hemp should be able to be XO'd lower.  The issues in the higher frequencies are the same with the same size driver.  You can use software such as the edge to see the effects of baffle size and driver position.  Use the wings and stuffing for your bass augmenter.  If you put your main driver in some cavity to the rear, then test baffles are needed in order to optimize your sound, since modelling can't predict it.  It can sound good that way.  I use big roundovers on the front and fold right at the driver cutout in back, with tapered wings and the outside wing 2-3cm deeper than the inside.

[Rudolf]

I want to make the baffle as narrow as possible, but am happy to do wings both to aid baffle size and support the baffle.

It very much depends on the crossover frequency. At 300 Hz a 30-40 cm wide baffle without wings should be sufficient - almost regardless of the driver. Below that the Qts of the driver will come into play. I believe that for 100 Hz xover the baffle for the Fostex would have to be much wider than a baffle for the Hemp driver.

[JLM]

The best design I've heard for the FE206E was 0.75 cu. ft bass reflex.  Bigger boxes offered deeper bass, but  it was muddy.  The 0.75 cf BR crossed over very nicely to a sub.  If I had FE207E laying around that's what I'd build.  But I'd like to hear a comparison between that and a Fostex 167E in BR (deeper bass, less midrange emphasis, and cheaper).

[Luigi]

Hi JLM

Actually, that's what my Penguins started off as; bass reflex cylinder, with a 90 degree bend at the top into which was mounted the FE206E. Bass reflex tube out the bottom. They started off as "periscopes" for obvious reasons, but once I carpeted the exterior and put black feet on the bottom the kids renamed them the Penguins.

Anyhoo, they had sod all bass. But the change to Hempcone FR8s changed all that, and they slotted into exactly the same cutout. Plus, they imaged much better.

After the break in (house, not speakers!), I decided to try an open baffle design because I had already turned my sealed subs into open baffle (U-shaped) subs. What an improvement that was!

So looking forward to my first ever OB speaker, and will eventually get round to replacing those drive units with the Hempcones(probably) or Visatons b200s perhaps.

The signif other never liked the look of the Penguins, so perhaps the OB might be more to her liking. She reckons invisible speakers would be best, like in wall, so perhaps I might eventually make the OB out of perspex, which could be a hoot.

[Luigi]

Finally got my act together. Went out and bought a skillsaw, cheapest I could find was $59. Money well spent I felt, in retrospect. Good for chopping firewood too

Anyhoo, my boy had scrounged a piece of plywood for his skateboarding obsession. I waited til he was out banging himself up with some of his mates, and ripped into it with a new meter long aluminium ruler - so cool; gotta love that hardware store - and the skilly, quickly banging out some 12 inch wide 40inch tall open baffles, and a couple of sets of wings. Having been outside, the plywood quickly began delaminating so had to screw some of the pieces back together. It looks real jimmy.

Found the old FE206Es I had put aside after upgrading to FR8s - later stolen - and made some holes for these, and bunged them all together with screws and piano hinges.

The sound was instantly rubbish. Hands cupped over mouth effect, no imaging, no extension. And the whole thing looked too big. So out with the skilly again, and knocked 4 inchs off height, and a couple of inches off width. Now looking much more acceptable for the little woman who is conveniently away for 2 weeks while I create these ugly SOBs.

Still rubbish sound. So down to the art supply shop for a scalpel, and out with the dustcaps, something Id been threatening to do. Easy as, and a 15/16ths socket fitted snugly in the gap.

Slightly better but still rubbish. Then it dawned on me that the whole thing sounded phasey, so I switched the red and black terminals on the back of the amp, and suddenly it all came together. No more head in vice imaging, a solid central image, complete disappearance of speakers themselves, and this overwhelming sense of dynamics and pace. 

There doesn't seem to be any great hole here either. The FEs do very little bass, but my 12 inch open baffle U-frame subs fill in the lower frequencies nicely.

So, long story short, the FE206Es can work on open baffles. No, really.
Not that that is stopping me from looking at the b200s or the genIII FR8 Hempcones. Wondering which is going to work out better on this modestly sized baffle. Anyone have experiences with these two head to head??

By the by, the baffle as it stands is just to get a handle on size and sound. I intend to use these as templates for solid wood baffles and wings eventually.

On a final note, Im not going to be at home when the Mrs gets back, as Im off to watch the second round of the Superbikes at Phillip Island in Australia. Cant wait to see the expression on her face when she sees them. She will be so impressed with my DIY efforts…not.

[Russell Dawkins]

Luigi, are you saying that you changed red for black on just one channel or on both?

If you just changed the wiring of one and the speakers were out of phase with each other, then I'm sorry but you're going to have to stick that dust cap back on, get a big sheet of plywood and do it all again!

Just kidding ... sounds like you're having fun!

[Luigi]

Yep, all good fun Russell. Makes me wonder whether the amp or the drivers are at fault? I checked carefully that I had wired the drivers up correctly, putting the positive lead on the positive pole of the driver.

Wonder how often it is that the positive and negative poles of the driver are labelled incorrectly? The inside of the amp has only black wires, so Im thinking that it might be the amp at fault here, wired out of phase?

As an aside. It's kind of annoying that I'm getting some of the best sound I've yet heard out of what must be the cheapest speaker I've ever built. This is my first attempt at open baffle. The reason I tried it was not all the discussion on the net about OB but because my sealed subs sounded so much better when I ripped the backs off them and ran them OB!

[Russell Dawkins]

you can easily eliminate the drivers from the question by disconnecting them from the amp and experimentally, with a short length of insulated wire and a AA cell (or any 1.5 V cell), touch the positive end to the red terminal and the negative to the other terminal of each speaker.  The cones should both move in the same direction - out is standard -  with + to the red terminal.

[JohninCR]

Don't give up on those 206E's quite yet.  They're more extended than the B200 with a flatter overall response.  Raw they do have those biting peaks in the sensitive range, but I finally found dammar in Costa Rica, so now it's time for serious cone mods, including a serrated whizzer.  I have 2 pairs, and I'm willing to sacrifice one to see if I can tweak it into submission, like I saw someone do on the fullrange forum.  He claimed great results.  The addition of a very compliant positive roll surround is supposed to have a good effect according to Steve over at Decware, who sells a very modded 206.

[Luigi]

Hi Russell, John
Thanks for the battery tip. I'd forgotten about that so will give it a whirl.

Actually, I hadn't given up entirely on the FE206E. I have never heard them sound so good. Like the phase problem has been there right from the start. But once you've had a taste of a full range driver that does even a modicum of bass, like the FR8, it's hard to go back.

Saw a pic of the much modded FE drivers about which you spoke John. Think I also saw one set of FE206E drivers with the whizzer removed completely. Wonder what that would do to those nasty peaks?

[Russell Dawkins]

Saw a pic of the much modded FE drivers about which you spoke John. Think I also saw one set of FE206E drivers with the whizzer removed completely. Wonder what that would do to those nasty peaks?

prolly turn them into nasty dips 

[JohninCR]

Saw a pic of the much modded FE drivers about which you spoke John. Think I also saw one set of FE206E drivers with the whizzer removed completely. Wonder what that would do to those nasty peaks?

prolly turn them into nasty dips 

or just one big dip, ie top end gone.

[D OB G]

Hi Luigi,

I'm just new to the audiocircle, so this may be a dead thread, but I've had experience with the Fostex FE206e in an OB, using the size of the baffle to acoustically cross over to two Peerless xls woofers.

The bass wass great.  The Fostex was AWFUL.  I'd allowed for the possibility by including T nuts for the Audio Nirvana as well.  Not quite there, but a big improvement.  Both shouted, the AN less so.  I tried various compensating circuits-some from the net, others I worked out myself.  None worked.  Both had a rising response, ameliorated by toeing out sufficiently (and I'd anticipated this, so set the drivers well below ear level i.e already 15 degrees off axis before toeing in or out).

Compared to the AN, the Fostex exhibited distorted dynamic range (intermodulation distortion, multiple cone break-up modes?), but in any case it was unlistenable.  The AN is far from perfect, but I'd certainly recommend it over the fostex, BUT WITH BASS AUGMENTATION!!

I'm sorry to all you FE206e fans out there, and I know there are many, but it just didn't do it for me.  (I know there are phase plug mods, serrated whizzer mods, damar varnish mods, but in the end ...........