taming harshness of fostex FF125WK - Page 2 - diyAudio
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Old 30th August 2012, 02:42 AM   #11
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Quote:
Originally Posted by Bigun View Post
was this the full enable treatment, just the tri-foil or something else ?
Full treatment.

dave
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Old 30th August 2012, 02:46 AM   #12
Bigun is offline Bigun  Canada
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good to know - one of these days I'll go the whole nine yards with these drivers and see if I can' rescue them.

p.s. Normal - for me, filters didn't help. I guess you only reduce the excitation signal, but this doesn't address the fundamental issue of a cone resonance.
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Old 30th August 2012, 03:39 AM   #13
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I don't have my 125WK in a cabinet yet, but I selected based on listening and comparing while in Japan. i had the impression that when you listen a bit off-axis, it was nicely musical without extra components.
Otherwise i expect that you'll have more success with an equalizer like the deq2496 than with classic notch filters.

Last edited by talaerts; 30th August 2012 at 03:42 AM.
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Old 30th August 2012, 08:57 AM   #14
ODougbo is offline ODougbo  United States
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Agreed,

Its' a nice 4" driver, very natural sounding [in a box]. Using a .75mh/7ohm resistor for a filter (need to add small cap). We tried a larger coil (2.5) but ran into some other issues. The filter helps a little bit - to sweeten them up.

I had a handful of light country music the other day (son's) I was very surprised how well they sounded, very full/lifelike. Wife and son agreed - "hey, that does sound nice".

As many know, I have been testing them in boxes for a long time now - I do feel that they need a good bit of damping material to calm them down.
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Old 30th August 2012, 09:10 AM   #15
hajj is offline hajj  Lebanon
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Dave, thanks for chiming in.
I'll be applying the zig glue today.
As for the Enabl process, does it involve any microgloss?

ODougbo, the reason I went with the FF125WK was that I wanted a two way OB with the full ranger covering everything from 150-200hz upwards and the FF125WK fit the bill just right with a good HF extension, a low enough Fs and an x-max that wold not make it strain or distort.

Below is my close mic measurement waterfall (3cm from dustcap) of the FF125wk on the OB board (60x45cm). It clearly shows the ringing at ~7khz. I'll measure later to check if the zig will cure any of it.

P.S: while there are lots of posts about the FF125WK, none addresses the issue I'm having in my setup
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Old 30th August 2012, 10:05 AM   #16
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Quote:
Originally Posted by Bigun View Post
...this doesn't address the fundamental issue of a cone resonance.
Everything above ~1.5KHz is resonance. That's how wideband drivers produce HF / extend their upper BW limit. Some frequencies more strongly than others, to be sure.
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Old 30th August 2012, 11:05 AM   #17
Bigun is offline Bigun  Canada
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Originally Posted by Scottmoose View Post
Everything above ~1.5KHz is resonance. That's how wideband drivers produce HF / extend their upper BW limit. Some frequencies more strongly than others, to be sure.
I've not heard this before. It has been my understanding that these lightweight cones do work at high frequencies (i.e. not relying on parasitic resonances for everything), especially some of the new MA drivers, and that perhaps the dust cap is responsible for helping too. Not saying you're wrong, only expressing my surprise - I guess I learned something new
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Old 30th August 2012, 11:06 PM   #18
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by norman bates View Post
has no one made a notch for it ?

Any measurements ?

And yea, it can measure flat but it can be "ringing down" in the time domain (waterfall plot) especially so close to the nasty 8khz range............

6khz (tang band 4" bamboo), not too bad unless you really know what it is doing and defitinely know it shouldn't be there. 6khz adds a nice clang to cymbals........

Norman
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Old 30th August 2012, 11:11 PM   #19
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Yea, I'd seen you've been struggling with them, but I havn't fully read the threads.

I'd love some measurements b4 and after to justify the enable on the ff125wk............

Norman
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Old 31st August 2012, 08:14 AM   #20
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Quote:
Originally Posted by Bigun View Post
I've not heard this before. It has been my understanding that these lightweight cones do work at high frequencies (i.e. not relying on parasitic resonances for everything), especially some of the new MA drivers, and that perhaps the dust cap is responsible for helping too. Not saying you're wrong, only expressing my surprise - I guess I learned something new
We can't beat the laws of physics. A wideband moving coil drive unit is only pistonic (itself a debateable word / definition) over a restricted BW. Everything above that is controlled resonance or vibration of the cone & any additions e.g. whizzers: another way of saying 'breakup.' The question is not really whether the driver is resonating, but how well controlled this resonance is. That's a big part of the science of designing them, and probably the hardest thing of all to do well. There are various methods. Some units use decoupling rings (those ridges you see on some cones) to progressively reduce the effective cone size as frequency increases. Some vary the cone profile and / or thicknesses. Some add strategic damping at certain points on the cone surface to damp regions where it rings more than others (the points often refered to as 'breakup'). Some more or less progressively decouple the main cone & hand over to a central dustcap attached to the end of the VC -essentially a central tweeter, turning the driver into a 2-way coax with mechanical XO. And so on. All have their advantages and disadvantages. But the constant is that it's resonant action. Same applies to conventional tweeters incidentally, esp. at the top end of their BW.

Last edited by Scottmoose; 31st August 2012 at 08:16 AM.
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