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Old 9th February 2015, 02:56 AM   #1
freddi is offline freddi  United States
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Default break-in on tough cases - how to handle?

got a Fane TC-250 - its published spec: fs=50, qts=0.65 - - out of the box this triple-cone (dual whizzers !) ran 67Hz and 0.84. After 12 or so hours of ~ 4 watts sine at 50 plus a mix of lower F's and higher excursions, fs dropped to 62Hz and qts around 0.9. Considering a two inch coil, its getting towards the possibility of a fair thermal rise to get the excursion required to exercise the outer rings of the spider. I would assume it may not meet spec but don't know yet. I've briefly run 15vrms which is around 28 watts nominal to 8 ohm.

how do you guys handle these weird cases? - playing music with the speaker in an enclosure would not work well as the midrange sensitivity is around 98dB.
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Old 9th February 2015, 12:23 PM   #2
IG81 is offline IG81  Canada
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Hey freddi!

I'm not sure why such large variations happen. I've more or less cracked a similar case with a pair of Faital 6FE100 I have, with much higher Fs and Qt than published. After some measurement bumbling on my part, it turned out the spider is stiffer than supposed and no amount of exercising changes that in my case. I had them on ~10-15VRMS of 20-30Hz for hours at a time and could not measure much of a change after I let the motor cool down.

Small-signal loudspeaker parameters: some questioning

As Cms usually goes down with little cone stroke, I'd be surprised if higher drive levels at measurement ever produced lower Fs and Qt, even though this is what such a driver is expected to see in everyday use. Finally nailing the measurement for Mms has me convinced I did everything right.
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Old 9th February 2015, 01:41 PM   #3
freddi is offline freddi  United States
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hey back IG, I have two sets of Peavey in 15 and 18 where free air resonance are off a half octave and very stiff basically changing vented box woofers to open baffle woofers - in contrast, I've an Eminence Beta8cx laying out for a decade - its "spot-on" the factory spec of 62Hz and 0.29 qts. Did you contact Faital Pro to ask what's up with your drivers? In recent buys, Visaton's little cheap and cheerful BG20 came close to spec. Fane has a great driver - but I really doubt if can get it "forced" to spec. I've been careful not to fry it in the loosening up process and fs did drop 10%. Build quality is good - the basket seems a bit sturdier than a TF1020, impedance rise is controlled, xmax is large for a fullrange, the double whizzer arrangement really works, and it never was a vented box woofer in the first place.

LMAO - back through your thread, Dr. Gedde's comments on T-S are "good"

Last edited by freddi; 9th February 2015 at 01:49 PM.
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Old 9th February 2015, 01:56 PM   #4
IG81 is offline IG81  Canada
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That was a while ago, so I'm not to sure anymore, bu I may have sent an e-mail to Faital and likely did not hear back. Their specs - very consistent between both drivers if nothing else - pretty much void the BVR I had designed for them in Hornresp. I guess a 15L sealed & stuffed box will make for fair enough workshop speakers, possibly with APT80 tweeters I have in a box.

OTOH, I measured my pair of Fostex FF85WK to be very close to published data, I was pleasantly surprised.
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Old 9th February 2015, 02:05 PM   #5
xrk971 is offline xrk971  United States
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I don't agree with what Gedlee said that T/S params are worthless because the room dominates/or they are unreliable. I doubt that the thousands of people who now who successfully design their own tapped horn subs and other vented alignment subs in the sub woofer forum would agree either. The tools we have to simulate and model bass alignments work exceptionally well and they are based on fact that an electrodynamic driver can be modeled as a lumped element system like a circuit using T/S params. Out in the open for PA applications, the room effects are not important. In a house, the room effects are important, but we still need a baseline of performance (in the absence of a room) so that we can compare. This is like saying measurements are worthless because they are affected by the room they are measured in as being discussed in this thread: http://www.diyaudio.com/forums/full-...ts-ref-fh.html

Freddi,
You might want to exchange those Fanes - I doubt you will ever push an fs from 67Hz down to 50Hz by exercising it. It sounds like the magnet is not as strong as they claim which may be why the Qts is so high. That is interesting that your decade old Beta 8cx now has params that match their newer T/S specs! The old ones had a slightly higher Qts I think. But hey, Qts of 0.29 is in a better direction for a K or XKi in any event so you are getting a bonus.

Last edited by xrk971; 9th February 2015 at 02:18 PM.
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Old 9th February 2015, 02:48 PM   #6
freddi is offline freddi  United States
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hi XRK971 - I just have one Fane - the motor with fs and qes currently running about 20% high would not be a terrible problem for open baffle work. (the Karlsonator 12 would be far preferable to open baffle) Of course T-S matter with regards to low frequency response. It may be possible in some cases where there's a rising on-axis response where calculated peaking may not be so evident. Would you agree? Geddes seems to be working in the area where woofer qts ~0.3 and not the high Qs which we often have to contend.

fwiw, here's outdoor on-axis of a 70 liter 41Hz tuned reflex with a stamped frame Nirvana Super10 vs a Large Advent sans grill. This was with the speakers elevated off the ground but near my house wall. Qts and fs on the Nirvana rather than what was claimed ran around 0.41 and 50Hz IIRC - there was not much boom - very little subjective "bass". The best I've heard my Super10 is in the Karlsonator 12, although it also played very well in K15 - might be a matter of taste between the two.

Click the image to open in full size.

Last edited by freddi; 9th February 2015 at 02:53 PM.
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