Fostex F200A

[Peter17]

Bij 4000-5000 hz gives the Fostex driver a metalic sound bij bigger volumes.
What can i doe about it?

[Scottmoose]

I bet you do. Looking at Fostex's massively smoothed FR plot, there's a peak centred at 4KHz, and from experience we know that the small bump that appears on their published FE126E FR, is in reality a +8 - 10db spike, which probably explains the metallic sound you're hearing.

Not sure -phase plugs might (might) be possible, which would certainly solve the problem if they could be fitted. Damping the dust-cap with varnish etc., might be an option.

EnABL apparantly makes a big sonic improvement, and I suspect would be worth doing at some point. Only slight problem is that nobody has figured out exactly what it does in a technical sense yet. Ron's certainly established what it doesn't do, so we're in a 'we don't know what it does, but we know what it doesn't' situation at present; this will only improve in the near future though as it's further explored.

[ronc]

this will only improve in the near future though as it's further explored.


The physical actions has merit. I can see some very good applications/results ,with the current design/methods, within a limited BW.

Now to tackle the physics outside the limited BW.

I have some time now to investigate as i handed over the ultrasonic edge scanner to production(up to Rev C) and i am not going to invest time in any other work projects till after the holidays.

ron

[el`Ol]

J.Manger mentions some viscoelastic polymers you could apply to the metal dustcap.
http://www.freepatentsonline.com/4029171.html
But this is probably not up to date, since the patent is quite old.

[planet10]

EnABLed drivers that have been measured have not shown significant changes in FR so it is unlikely to kill that problem. Syill worthwhile doing, but it would be better to fix the problem before doing anything else.

The FF125 has what might be a similar colouration, I suspect it is from the metal dustcap. Removing the dustcap would probably fix the problem, but would also, i suspect, reduce HF extension dramatically.

dave

[OzMikeH]

Originally posted by planet10
EnABLed drivers that have been measured have not shown significant changes in FR so it is unlikely to kill that problem. Syill worthwhile doing, but it would be better to fix the problem before doing anything else.

The FF125 has what might be a similar colouration, I suspect it is from the metal dustcap. Removing the dustcap would probably fix the problem, but would also, i suspect, reduce HF extension dramatically.

dave

....unless that little metal dustcap is ringing like a bell.
Reduced reflections from it's edges would mean less ringing.

Off with it's head! (well, it's dustcap anyway)

[tiefbassuebertr]

I have heard, that the versions from currently production of this model is much more better in all respects than older versions.

Are there such observations by user's, that have tested both versions ??

P.S. By the model No FE 166 this is so in real life (especially by the frequency response graph - equalizing in the midrange aera isn't necessary by the newer versions).

[BHD]

I know it's heresy, but the right thing to do is use a notch filter and cross the driver over to a really good supertweeter. I've heard the driver with and without one and the difference is really night and day. Even with extended break in the peak is just awful sounding. Used with a notch filter and a good (in this case ribbon) supertweeter the F200 is a world class driver.

[brady]

hello BHD. so an LRC centered at 4khz? or would it be better to just cut it off at say 2k5hz or maybe 3khz, and then supplement with a tweet

[steviedon]

What about a convex foam plug over that ringing dustcap, to disperse some of the HF beaming, similar to the foam plug on the Geddes waveguide. It seems even more heresy to be discussing modding a $400 driver.