If an old paper suspension speaker is repaired with foam suspension, how much effect on its characteristics occurs? I'm thinking its liable to get into trouble if mounted in an open backed cabinet due to less restraint/damping.
NT
** Could lower the free air resonant frequency and Q factors quite a bit. ** The voice coil length and magnet top plate thickness set the max excursions possible in normal use and you are not changing them.
But if the open back cabinet falls over or there is a nearby explosion, all bets are off.
... Phil
heh
My knowledge of Thiele Small isn't great. AIUI with foam suspension... Cms goes up Fs goes down Qms goes up Qts therefore increases Vas goes up Zmax goes up
Of course coil throw stays the same, but with less damping its more likely to endstop & thus distort at resonance in an open backed cabinet. Is it enough to cause problems?
NT
On Wed, 1 Jul 2015 00:45:16 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
If you are servicing an old speaker, simply changing the surrounds makes no sense, when you should be swapping out the entire cone/surround/coil support assy with a newer, more modern media.
The only exception would be an acoustic suspension design, where the cone impregnation usually makes for a seal of the assy against air intrusion of the non-ported cabinet during operation.
I truly hate you dopes who refuse to set YOUR line lengths and force the readers of your posts to do it for you.
This is for use in the 3rd world. That the cone is paper is not a problem.
the joys of google groups
Excursion at resonance will increase, the question is really by how much.
NT
On Wed, 1 Jul 2015 07:05:27 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
Jeez.... it would be cheaper then to simply replace the entire transducer (speaker). "Cheap Chinese" abounds.
My personal time is worth far more than to spend it reworking speaker cones for "3rd world" use.
Hell, watching a lioness protect a tiny baby baboon was more gratifying.
You misunderstand. This is for people in the 3rd world to do. They're not about throw away something fixable & buy new.
NT
On Wed, 1 Jul 2015 11:21:58 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
The suspension surrounds are new (and cheap as in falling apart soon after). The adhesives are new. Your trivialization of their enslaved
*employment* is not new.
ok, back to the killfile.
NT
On Wed, 1 Jul 2015 13:10:24 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
You are stupid to use one to begin with, and even more stupid to announce your edits.
Goddamned pussy crybaby is what you are.
t.
ursions possible in normal use and you are not changing them.
all bets are off.
** No joke, I have seen examples where pyrotechnics on stage wrecked the co nes of some Altec 421s and just slamming the tail door of a van did the sam e to some EV15Ls inside. In both cases the speakers were fitted to small po rted cabinets (foldback wedges). ** Qms goes down with lower Fs, other things being the same..... Phil
bit.
xcursions possible in normal use and you are not changing them.
n, all bets are off.
cones of some Altec 421s and just slamming the tail door of a van did the s ame to some EV15Ls inside. In both cases the speakers were fitted to small ported cabinets (foldback wedges).
Ah!
right. thanks.
NT
So really, you don't know what kind of cabinet they're going into ? Another thing is just how much power are we talking here ? Third world is probably not repleat with 200 WPC amplifiers.
Whoever said that cone excursion is limited by the voice coil, I cannot agr ee with that, at least on some speakers. In the old sea;led box cabinets, i f you ran the woofers in free air they would bottom VERY easily, I mean on a couple of watts at the right frequency. Those speakers are not suitable f or ported cabinets or those with large passive radiators. Completely sealed cabinets are rare enough these days that new woofers do have their cone ex cursion limited either by the motor or possibly even the yoke. You simply c annot assume that aout an older woofer. But the bottom line is that the pap er around the edges would not be what the engineer used to limit the cone e xcursion. It would be too failure prone. Would probably be nasty sonically.
It won't matter much. The suspension is pretty floppy, either way (you need to use a molded "rolled" foam, not just a sheet, to be sure it IS floppy). I've replaced suspensions with bronze bellows (long story, involves vibrations transmitted inside a vacuum chamber), it didn't affect the woofer-as-electrical-load in any significant way.
Shaping paper to make a good surround is easier than shaping foam, though, in an artisanal setting. Shaping paper isn't a lot different from shaping a felt hat.
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