Is the FE 108EZ a bad Driver?

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#21
Fhis is the horn
 

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#22
hello all,

yesterday i went to a hifishop and asked the dealer what he thinks about the measurement HobbyHifi made.

he told me that they are wrong ... aarrgghhhh ... of course he did, he want's to sell the fostex drivers 😉. then he switched on his computer and i could see his own measurements: the frequency response from the 108ez -and various other fostex drivers- looks similar to the frequency response form fostex. you can see a small dip at about 1000hz, but it is not drastic.

he said that he would measure the frequency response in front of me if i would buy the drivers at his store.

after all, i really think that HobbyHifi is wrong. 😉

@franz g

hello franz,

are you "franz g" from the german forum www.audiodiskussion.de ? i think you are.

i know that you have the little fostex 103e in the recommended enclosure, or at least that you had it. could you please tell me the diffrence between the 103e and the 108ez; which sounds better in your opinion? and why?

have a nice day 🙂
lilmik
 
#23
LilMik said:
hello again,

searching this fourm up and down, i found a nearfield measurement of a 108ez in an 2 liter sealed box. look at the picture. scary 😱 . on the other hand, look at the frequency response from 7000hz and upwards. i really don't think the 108ez has a frequenzy response like this.

josephjcole made the nearfield measurement. here is the thread, it is post number 6 --> http://www.diyaudio.com/forums/showthread.php?s=&threadid=68706&highlight=
Click to expand...


Nelson Pass said:
I haven't measured the 108EZ, but there's no way
that it has that dip. It's an enclosure or measurement
artifact.
Click to expand...

Sorry, I've been out an about away from the form for a bit... I do think those measurements are fairly correct. That graph was nearfield, but they closely resemble the measurements that I did at 1 meter. With or with out time gating to remove reflections. I've done many different measurements of these drivers in different enclosures and they all have this hole.
Having said that I still listen to them and love them. I would not hesitate to recomend this driver to anybody. In the right application it can really sing. I've got mine in some wide range 2-ways (with a 12" pro-sound driver) which I've found to work very well, as the 108's are not exactly bass monsters 😉. Well for that matter they don't have the air of a good tweeter either 10kHz and up is not that great. Maybe I'll switch to a 3-way at some point. No plans to drop the 108 though.
Joe
 
#27
LilMik said:
how does fostex smooth there measurements. if you use 1 octave or 1/2 octave, a small but sharp dip may disappear or look hamrless, if you smooth over 1/16 octave, it can look very bad.
Click to expand...
My apologies, I just read this. This is exactly what I saw when looking at the graph. The Fostex graph appears to be smoothed to 1, or 1/3 octave which might make that dip look much more benign.
 
#28
The dip is probably there. But it is not unfair to present 1/3 octave smoothed measurements where the dip doesn’t look bad, rather it is unfair to present unsmoothed (or smoothed to 1/12 octave for instance) graphs where the dip looks scary. The 1/3 smoothing isn’t there for nothing, it isn’t a random choice but a well thought one. It is coming from years of experience and it is correlated with the way our ear responds - our ear smoothes frequency regions in such a way. If unsmoothed frequency responses of well-known speakers were to be presented you would all be very scared and would come to the (apparently false) conclusion that all these speakers are not about hi-fi.
Furthermore, our ear corresponds well to bumps but is more insensitive to dips. Someone should perhaps look after bumps in 1/6 smoothing, and dips in 1/3 octave smoothing. Lastly, our ear doesn’t reveal the same sensibility in every frequency region (and I’m not talking now about equal loudness contours) – it responds more if a same octave region dip is in the 300 Hz region for instance, were it will perceive changes in tonal balance - voices and string would seem thinner, but doesn’t easily recognize even a broader dip in the 1KHz region, which doesn’t easily change the tonal balance)
This fostex driver is probably of very good quality and its 1/3 octave response reveals part of this reality.
Regards,
Thalis
 
#31
Franz,

Thanx for the guided tour to the Cornu patent. For those who don't want to fight with 13 individual pdfs, i've assembled it into a single pdf (300 dpi/430 kB) http://p10hifi.net/planet10/TLS/downloads/cornu-spiral-horn-patent.pdf

If anyone wants to translate the German to English i'd be happy to assemble that too. (my wife knows a bit of German so i will do a first hack at it). The pictures need no translation but a bit of explanation wouldn't hurt.

dave
 
#34
Interesting thread. I like measurements.

Has anybody investigated what causes the dip? (Regardless of it being 5 or 10db everyone seems to agree it is there). Does the dip disappear off axis? I haven't seen this driver myself, is the phase plug mounted solid, or is it of the "whizzer plug" variety that is loosely mounted with a bit of surround material?
 
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