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Old 21st September 2012, 06:44 PM   #41
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In the mFonken there is no set in stone driver position. It is usually drawn, for aesthetic reasons, in a position set by the golden ratio.

dave
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Old 21st September 2012, 07:26 PM   #42
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Originally Posted by planet10 View Post
In the mFonken there is no set in stone driver position. It is usually drawn, for aesthetic reasons, in a position set by the golden ratio.

dave
Thanks Dave. I've just completed the champfers. They are built from 1/2" Baltic birch, and have the optional braces in place.
regards,
Bill
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Old 22nd September 2012, 09:15 PM   #43
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That looks right

dave
Dave

1) what would the port length be for the FF105WK / FF125WK or does it need a redesign?
2) what is the rolloff frequency (bass)?

These would be nice to go next to a computer, the metronome does not really fit on a desk (wink)

Many thanks for the good work.
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Old 22nd September 2012, 09:36 PM   #44
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I haven't looked at the FF105 yet (but made good progress on getting my next set of protos ready -- hopefully someone doesn't sweet talk me out of this set), and i just hooked up the test build of the mFonken125 (they need some break-in). You can build those exactly like the mFonken (for FE127) but leave out the vent spacer (and of course modifiy the driver brace to suit the different magnet)

There is an interpretation step from the sims, i'd estimate F3 near 75-80 Hz, F10 near 50

Almost done all the spots:

Click the image to open in full size.

dave
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Old 22nd September 2012, 11:41 PM   #45
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Originally Posted by mondogenerator View Post
I agree. 25% THD of odd harmonics would sound like a guitar fuzz pedal....actually 25% of even harmonics would sound like a fuzz pedal too...

25% THD...so a 3:1 ratio of sine to overtones...that only represents something like -6dB for the sum of the harmonics amplitudes. i dont get how that is possibly correct, otherwise i struggle to see how the ear could distinguish the phase problems of a 2 way speaker over a FR type when listening to harmonically rich instruments like sax. Obviously, a full fourier anaylses would need to be done to determine the full extent of the harmonics produced by any given driver, but being natural in nature, they would be less at 5th and 7th than at 3rd harmonics.

I would have believed 2.5% THD or even .25% THD, my experience with amps, although small, showed the onset of audible THD to be somewhere between 0.5 and 1%THD. I by no means have 'golden ears' but i do not have a sunshine halo syndrome afflicted ones either. 25% of THD may only just be annoying for those who blast an personal stereo at full volume(in the days beforee mp3), or for those that have pretty underpowered valve gear, but I CAN hear it way before that. I know this as i measured the THD and commented on audibilty for my thesis in E/EE. by no means is it absolute, as 2nd harmonic THD was not tested.

I think this is more of a case of how much THD is acceptable to the listener, and what type is acceptable (especially if it artificially extends the HF BW of a driver), and not a case of what is strictly audible. Whilst i respect Toole's work, his latest work HAS recieved some justified criticism, though not from me i might add.
There is software that can add harmonic distortion and perform AB testing. In blind testing (that I've reproduced myself) with clean piano music, audible THD was 3%, and with rock music about 10%. Even then, they sound pretty darn clean and good. You need a very high level of distortion for it to become a distraction. Considering how easy it is to get below 1% harmonic distortion, I'm with Geedes and Toole on this. It's a meaningless measurement.
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Old 23rd September 2012, 01:20 AM   #46
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Originally Posted by planet10 View Post
.....i just hooked up the test build of the mFonken125 (they need some break-in). You can build those exactly like the mFonken (for FE127) but leave out the vent spacer (and of course modifiy the driver brace to suit the different magnet)

There is an interpretation step from the sims, i'd estimate F3 near 75-80 Hz, F10 near 50
.....
dave
Thanks, that sounds similar to the LS3/5A cutoff.

The metronome for the FF125WK models at approx 50Hz @ -3db and the FF105WK at approx 57Hz @ -3dB (depending on port length). The FF125WK metronome likes a 1 Ohm resistor in series and the FF105WK a 1.5 Ohm resistor.

I suspect power handling of the mFonken will be higher due to excursion limits in the metronomes. Was quite surprised at the results when I modelled the FF165WK in the metronome - not a large amount of bass improvement over the smaller FF125WK. Am having a 5-6 weeks waiting time for the FF105WK to arrive which will be for in the office.
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Old 23rd September 2012, 01:29 AM   #47
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otherwise i struggle to see how the ear could distinguish the phase problems of a 2 way speaker over a FR type when listening to harmonically rich instruments like sax.....
Very noticeable amongst others on voice. But then many have never heard life, unamplified music or only listened to low resolution MP3 and/or would not know what to listen for.

My wife has hearing defects and she can hear things (according to her the difference is like day and night) that I do not manage to pick up. The FF125WK metronomes replaced some Monitor Audio Studio 12's that we've had since 1997 and they were not cheap.... She also listened to LS3/5A, LS5/12A. Monitor Audio Studio 2, Monitor Audio Studio 20, several Mission loudspeakers and a host of other lesser known ones and none make her as happy as the metronomes. I am keen to try out some smaller metronomes (ff105WK) and some mFonkens with the FF105WK.
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