Yet another Fe126e mod!

[dfreemansc]

So I likes a lot of what these drivers can do, but I hate the way the high frequencies tend to drill through your skull (all of this IMO of course!)
So I tries Daves' Dammar/Puzzlecoat mods along with a perilous but successful dust capectomy and phase plug install, with the result that the drill had got smaller, but was still there.
Then I reads (no, I don't know what's with the esses either!) about Steve Deckerts mods with the DFR-8, and thought "OO. Haven't tried that one, wonder if it'd work with a smaller driver?"
So I bought some 4.5" surrounds off Steve and set to work.
The mod was not actually that tricky to do. The hardest part was levering off the plastic trim without lifting the original surround.
Listening afterwards reveals that the 'drill' seems to have gone away completely - in fact I can now comfortably listen on axis!
The only downside I've noticed so far is there's a mechanical 'buzz' when playing low frequency test tones, possibly where a small portion of the original surround lifted at the inner edge, but so far I've not noticed it with music.
More impressions when I've modded the other driver, bit so far at least, it looks to me that Steve's come up with a bit of a winner! (to my ears at least)

Cheers
Dave

[dfreemansc]

Frequency reponse.
Original driver in blue, modified in pink.
Any ideas anyone how to reduce the 7K peak?
Both responses are white noise, 'C' weighted (I was playing with the software and forgot to remove the weighting before taking final measurements, but I think the graphs are still valid for comparison purposes).

Cheers
Dave

[Svein_B]

Most interesting. Especially your measurements.

These measurements indicate that, while giving some clear improvements, none of the mods we have so far tried manage to tame the FE126E's peak around 6.6 KHz .

MarkMcK performed some measurements and analys of the FE126E in the Full-range reference project tread.
His measurements are here, and measurements of his "fixed" drivers are here and here
Unfortunately he did not share with us the details of the mods he performed.

SveinB

[MarkMcK]

Hi guys,

Fostex drivers are not good candidates for diy projects. Too many problems and too much skill required to implement them.

For example, many of the Fostex transducers have problems with edge holes. Adding mass to the surround will reduce the edge hole problem. Yet you risk the creation of a low frequency buzz in modifying the surrounds. This is not a good thing.

Regardless, if the surround mod adds mass to the system (typically 1/2 of actual mass of surround material), then it will also reduce high end output. It will not, however, address the cone vibration (breakup) problems.

Oh yes, coating a paper or metal cone will have almost no impact on cone vibration modes. Not even when adding many coats. I have before and after testing documentation to support this statement. Generally material vibrations are not simplistic and most diyers try to address them with simplistic solutions

[Rick J. B.]

Holy cow!

Hey Mark I have no reason to doubt a single word you've said but I'm chuckling cause you're going to start a fire storm if every guy in here who has used a Fostex driver in their project responds to your post.

All that said, what fullrange drivers do you believe lend themselves well to the diy'er?

Rick

[MarkMcK]

You cannot fight dogma. If they want to flame they can.

Still, challenging dogma is worthwhile. You will not change the mind of the dogmatic, but those that aren't will know that there are other ways to look (or listen) to the world.

[chrisb]

Originally posted by Rick J. B.
Holy cow!

Hey Mark I have no reason to doubt a single word you've said but I'm chuckling cause you're going to start a fire storm if every guy in here who has used a Fostex driver in their project responds to your post.

All that said, what fullrange drivers do you believe lend themselves well to the diy'er?

Rick

It would be very interesting to engage Ed S in this conversation.

[Rick J. B.]

Mark, you didn't answer my sincere question.

Chris, so who is Ed S?

Rick

[dfreemansc]

Mark, of course you're absolutely right on all counts.
A thought that occurs, it would be interesting if someone did/has done a set of responses for the effect of increasing layers of cone coating to see how it compares to the peripheral mass damping that I have done.
I suppose for me (as a comparitive noob in these areas) the aim was to increase the acceptabilty of the sound rather than aiming for perfection; in this I think I've succeeded - to my ears the sound seems more balanced, but then this is a very early days personal opinion of course.
Do you have any useful references for breakup mode theory and strategies for overcoming them? Google as usual so far has been giving me 15000 snippets without anything I can really get my teeth into.
My lack of knowledge in this area frustrates me: I have a Physics background, but when it came to specialising, I chose the wrong "A" - astrophysics rather than acoustics!

Cheers
DAve

[Scottmoose]

I suspect he's refering to Ed Schilling, of Hornshoppe Horn fame (a kind of modified, enlarged Buschorn MK1), owner of a wide variety of personal artillery etc., and 4 - 4 1/2in Fostex driver enthusiast. If memory serves, Ed started out by using the FE108Sigma, moved to the FE108ESigma, and currently uses the FE126E in his cabinets.

Fostex driver's don't lend themselves to modifications. Hmm. Dave's phase-plugs measureable improvements to the FR. Fostex's own brass-rings to mass-load their Sigma drivers have generally proven highly effective for all those who've tried the. Cone damping is not the easiest thing to get right I agree, but it's possible for some people to do it right with correct location and application to break-up points. Witness the damping Dave applies to his FE126E cones, and the basket & magnet. He's done this sort of mod for 25 years or so I believe, and is constantly refining the process> It's done via measurements BTW: it's not just a shot in the dark. I'm not saying it's easy. But nor is impossible to improve these units either if you've the experience and the skill to do so. Not many DIYers have, but some do.