tweaking the Fostex 206E

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I built the a 45 liters bass reflex cabinet with 8cm diam and 7,5 long port. Is there any way to fill the hole in frequency responce around 100hz?

Here's what I thought to do:

1) equalizer

2) passive equalizer circuit

3) adding mass to the cone. How?

how these affects the group delay and the phase response? because I'm using it with a sub with cross frequency at 100hz so I would like to have a synchronized sound....

Now I'm making some experiments with the length of the port
 
Are we talking about the Fostex 45 litre box here? According to MathCad, and I've just modelled the box in the latest version of Martin King's worksheets to four decimal places, there, er, isn't a hole at 100Hz (or at least, not in 1/2 space). There is a hole at 150Hz in the horn, but IMO, the 206 horn isn't up to much. Ugly too.

Predicted response of the 45 litre reflex cabinet is attached; as you can see, it almost exactly matches what Fostex state: slowly decreasing bass with a peak (not sure if I'd call it 'controlled' though!) at 55Hz. If there's a big hole in the system response at 100Hz, then I'd say it's being cause by a room effect like floor-bounce, not a driver / cabinet characteristic. I don't like the reflex cab myself -you'd be much better off building Martin King's MLTL, or paying for Bob Brines's slightly more refined plans for a similar cabinet. They're an easy build -no harder than a reflex cabinet, won't be costly in materials, and you're unlikely to need a sub, except for frequencies below 40Hz. Alternatively, get them into a horn -again, a decent one will not require a sub except to support it below 40Hz.

I wouldn't advise adding mass to the cone -you might as well have bought a different driver in the first place; and there's a lot of potential for damaging the driver, which would be a shame. Adding some phase plugs will work wonders for the midrange and treble though -well worth doing. Damp the basket and the rear of the magnet with something like Ductseal. You could even try adding another magnet -just rip one off an old scrap pair of speakers out of a skip. Not a common idea, but might be worth a shot.

Crossing over to a single sub at 100Hz is a bad idea -anything over 70Hz is directional, so you'll be hearing frequencies between these two points coming from there, and everything else coming from your main speakers. Not so good. Two subs are needed if you want to XO over 70Hz IMO.

Get a BSC circuit on it too, if you want some more bass performance -you'll be loosing at least 3db through baffle-step diffraction. Depending on your amplifier, you might also want to add some series resistance. It'll lower the efficiency, but provide a more balanced response. Again, Martin's circuit, or Bob's, should do the job.

Hope this is of use
Scott
 

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there's the hole, look at my graph using winisd and also other prog is the same. Ok it stays in the -6db limit and so you can hear it, also because the room will boost that frequency.
An externally hosted image should be here but it was not working when we last tested it.

Could you show me your frequency responce but to 20k?

Damp the basket and the rear of the magnet with something like Ductseal.
what it does this to the sound?

Adding some phase plugs will work wonders for the midrange and treble though -well worth doing
I like the treble of fe206e

You could even try adding another magnet
and this? I've seen some people adding addition magnet to lower the qts, right?

anything over 70Hz is directional
it isn't 80hz?
anyway yes it is a bad idea for the most cases. But I place the sub beetween the two fostex, and I really don't notice the sound coming from there. Before I was using the sub at 150hz to completly fillup the hole:D I'm mad eh:smash: just in one song with a sax I could locate the sound, but the main problem was the resonce of the room at that frequency in few cds, you know at 150hz the sub it has a strong output. the quality was good aspecially the voices were so full, you know like pavarottii whoooooooooooooo but with a great cavernous voice.

Depending on your amplifier, you might also want to add some series resistance
I'm using a DB technologies MT530 amplifier, do you know it? anyway I think it will drive anything...

There's a severe dip in the FR because 35l
you mean 45l, right?

my recommendation for a ported box is the 207E
yes but the last year when I built the speaker I was seeing a lot of people using that driver and saying it soud good in BR... infact it sound fantastic, it's just light on bass( it's one of the compromises you told?), but it deepends a lot of what you listen and especially from the records quality. I had them 30/40cm from the wall and was good until one time I tried with sub. Also the previous speaker I had had a good extension in bass region but man when the last day I tried they had not great bass.

thank you thank you
 
MathCad only goes up to 1Khz as it models the driver / enclosure combination, and above that point, the only function of an enclosure is to provide a solid mounting point for the driver. With all due respect to WinISD, it's not in the same league as Martin's MathCad worksheets. However, you can still see the similar shape in the response, which drops away from 120Hz to a peak at ~55Hz. The graphs have different values which makes them look somewhat different.

The Fostex box is actually closer to being a short, mistuned MLTL than a reflex cabinet IMO. It's not a great design, as Bob points out & I agree 100% with everything he says. For reflex loading, it's too big, for QW loading, not really large enough, with a port that isn't tuned too well. Not too uncommon an alignment, if you can call it that, to have a decreasing bass down to a slightly high Fc, which peaks. Not one I'd ever suggest though.

70Hz. Actually, according to the latest findings, it's 72.874Hz, but we won't split hairs. ;) To each their own!

Damping the basket will kill resonances in the structure of the driver. Worth doing, especially as it costs very little and is completely reversable. The phase plugs will smooth the 206s treble and midrange; you won't loose any detail; in fact, you'll gain some insight if anything as they also remove the resonance caused by the hollow centre pole-piece under the dust-cap, which rings like crazy at about 3KHz or so. It takes away a little of the artificial brightness, but you'll find them a better driver in the long-term.

The 207 is indeed the better natural driver in a reflex or otherwise resonant cabinet, primarily because it's a higher Q (relatively -0.26 still isn't much), giving it better bass, but also it lacks the rising response of the 206, which was nominally intended to be re-balanced by horn loading. You can also bring it into line with a circuit, but you loose some efficieny that way. The plugs, as mentioned, help here too. The massive magnet of the 206 might give a whisker more detail, but it needs larger values in a compensation circuit, and more cabinet fettling to get working right.

Do yourself a favour: get them into a better cabinet. I know it's a hard thing to face up to, especially if you've put a lot of work into the enclosures. Believe me, I've been there, and it's a real pain.
But, you are not hearing your drivers at anything even remotely approaching their best at the moment, and there is very little you can do to improve your existing boxes. Martin's or Bob's MLTLs would be the automatic choice for an easy, relatively compact build.

Alternatively, if you have the space, get them into a horn. There are a few options here. The Factory horn design for the 206 isn't up to much, and looks horrible. However, their design for the FE208ESigma is much better, and the 206 will work quite well in it. I've just done a double-horn for the 8in Fostex speakers which should be nominally flat in-room to 30Hz or so (Bruce V1.1 -see the Spawn of Frugelhorn thread). Or a BIB -I suggested some dimensions for the 206 on the zillaspeak site: www.zillaspeak.com/bib.asp

Any of these, MLTLs or horns, will allow your drivers to perform as nature intended; and they'll be transformed. You'll get more enjoyment out of your music in the long term -promise.

All the best
Scott
 
horns

its really really hard to sub a horn.

meaning that the speed of bass that comes out of a full range horn loaded is the sole reason to build a horn for it. to get a sub to catch up with that is very difficult indeed. it realistically does not happen, except in cases of good EQ and biamping, etc. lots and lots of money and fussing for a few octaves that the driver will put out better all on its own anyways.

the martin, bob boxes, I have not heard. seem to look solid for the driver.

the fostex recommended enclosure I think would perform well probably. I have not heard it, but have heard alot of good things about it. it might not be pretty, it is a tough build, but it is a nice orthodox squared off BLH megadynamic and nicely coloured sonically. something to consider.

there are alot of other nice options though. simpler, (lighter), for all practical purposes just as good.

I like the treble distortion from the dust cap too. it is fun and crazy sounding. admittably, these are not my only speakers though....so i do not have to live with it. some day I will get around to phase plugging a few of my drivers.

Clark
 
The Factory 206 BLH has a horrible response up to 200Hz. Not one of their best. OTOH, dropping them into the 208ESigma horn would be a heck of a good move. Now that one really is a great cab. Massive bass heft, looks far better, and a much smoother response too. The 206ES-R cabinet is an alternativbe of course -response falls somewhere between the two camps.
 
You and me both -I've got another 25 months of my PhD to go yet.

Yes, I've heard the recommended 206 cabinet. Not impressed. Even less so when I decided afterward to run a few MathCad sims (I apply the same comments to the 166 BTW enclosure too. This cabinet type is not one of their best). The 208 box OTOH I heard recently at a friend's house, and came away very impressed indeed. With live Metallica, the floor was shaking (and I don't mean just lightly quivering) and it kicked you in the chest like a PA bass bin. Massive down to about 36Hz. I can understand why the mouth is hanging in mid-air when it's got that sort of grunt in the LF regions.
 
And I have 206`s in recommended horn and love the sound and look. I veneered them in red oak and staines the inside of the mouth black. I also have 206ESR in recommended horns, veneered in walnut, while they sound more detailed and extended than the 206`s, the 206`s get more compliments on looks than the bog 206 ESR horns do. Maybe because the 206ESR have a T90EX on top with exposed wires but they are on solid walnut mounts I like them both, 206ESR are in a 2 channel triode PP, with analog source, and the 206`s are mains in a HT system that I use 2 channell often as well. Both sound great and look good, but I spent alot of time finishing them. There`s my biased opinion, FWIW.
 
I can't belive it!
today I get my hand on some old supertweeter magnets and I put them on the back plate of the fostex and surprise of surprises I get more middle/bass. ah now the voices are full and the instruments like electric bass ca be heard better. I noticed the cone is now moving less also....

Now I'm in search of bigger magnets:D

Question: Can I put them right in the center of the back plate of the speaker without the risk of coil overheating? I suppose yes because I don't see any vent on the backplate, right?
 
You should be fine if it's not blocking any vents. As I mentioned before, it's not a very common tweak these days, but it can work. Sounds like it has for you anyway!

Of the Factory designs, the Sigma is the best best from modelled response & I can vouch for it's subjective performance. Goes far lower than the standard 206 cabinet, has a much flatter response. I still think it looks prettier too. Let's face it -you can't really argue with a pair of cabinets that look like this can you?

Kofi -didn't know it was you running the 206s in the 208 cab. Did you move up to those from the 108s? How does your floor stand up to the LF output?
 

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"Moray James tweak"

Something anybody running FE206E's ought to seriosly consider trying _grin_

I used to run FE206E's in my Azurahorns.

Moray James sent me a cool tweak - basically, just ground either the negative or positive side of the speaker terminals to the basket (chassis)

Easy to try - take a jumper with alligator clips on each end - put one clip on the chassis and the other on the red or black terminal.

There is a difference in the sound - at least with my system and quite a few others

There seems to be a slightly ( roughly 2DB+- ) lower output.

Also, maybe a tad less dynamics.

However, the overall result is a more pleasing and accurate sound.

May be different for different amp topolgies - dunno.

Just about everybody that heard the FE206E's preferred them in tweaked mode.

IIRC, mine sounded better with the jumper from the negative terminal grounded to the chassis
 
I started out using 206E's in 208 cab's and thought they sounded great. I switched to 206ESR's but kept the 208 cab. I was looking for a bit more DB from my 45 SET amp. The 45 is doesnt have much power so every little bit helps.
I also grounded the negitive terminal to the frame on both drivers, it made difference that I liked. Phase plugs for the 206ESR was the finishing touch.:cool::smash:
 
greeting Ladiies and Gentlemen, please dont forget the Dallas II designed by Ron Clarke and Fullrangedriver.com. I built this horn for the 206.It has a great bottom end and I implemented the folllowing 1.grounding chassis to -ve
2.Phase plug
3. fluffy baff gently wedged between whizzer and main cone
4. damp chassis(masses of blutack)
5. polystyrene disk(1 inch) on back of magnet
and in then end I felt I was pretty daarn close to getting the best out of this driver without resortind to drastic measures such as surgery on the whizzer or using coatings or totally desperate measures like notch filters(only kidding).I have since moved onto visaton b200 in open baffles and haven't looked back. Anyway i hope my post is useful in some way cheers fergs
 
bluetack? is it a product for idraulics? It can be removed after the application just in case I want to go back?
The target is to lower the resonance of the basket, right?

Thank you to all, now I don't have to work again to make new cabinet, I put a lot of work in my BR box, they're strange and I like it so much.

Butt, I agree some horn looks very good, very aggressive also
 
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