This is a question that needs more context. Are we discussing a geometric X-max and an appropriate damper surround design to allow that excursion? Because many loudspeakers do not have the full mechanical capability that the manufacturer states. Klippel can be gamed. I once did verification measurements on a subwoofer that claimed 12mm greater excursion than was mechanically verified. All measured via Klippel. All measurements are subject to the honesty of the person doing them.
So what happens as you approach the mechanical limits of a surround? It depends on the surround profile. Half roll you can actually engage a little more than half of the roll.
Most here are familiar with that in general. But my original question reph(r)ased: does a soft paper larger cone deflect between 40 and 80 Hz? Otherwise: does the 10" paper cone behave differently from an typical 10" woofer alu cone between 40 and 80 Hz? My question has nothing to do with break up modes above, say, 150Hz: I am only asking about real LF in-box behaviour @ some excursion. Of course "ceteris paribus" applies.
@Boden
A paper cone deflects for sure.
You lose always a bit from the original impulse which gets lost in the material.
Stiffer cones can follow much better the movement of the voice coil.
Here a comparison from a book on loudspeakers
https://www.diyaudio.com/community/...loudspeaker-sandwich-cone.402917/post-7615908
From
Götz Schwamkrug "Lautsprecher - Dichtung und Wahrheit", from 1986.
A paper cone deflects for sure.
You lose always a bit from the original impulse which gets lost in the material.
Stiffer cones can follow much better the movement of the voice coil.
Here a comparison from a book on loudspeakers
https://www.diyaudio.com/community/...loudspeaker-sandwich-cone.402917/post-7615908
From
Götz Schwamkrug "Lautsprecher - Dichtung und Wahrheit", from 1986.
It can?
A example of paper cone failure when driven hard is the old and venerable JBL 2118, drive them hard enough and the paper cone will often crease/fold at the first rib up from the dustcap, then the driver needs a recone after.
Wether it is a pure mechanical failure or due to the combination with the heated VC junction i can't really judge.
Does not seem to be the as bad in the 2119 and M209 with a slight design change.
So yes paper cones does and can flex until the point of destruction. So can other materials given the right conditions.
As was pointed out before a paper cone is too generalized, the composition , mix and treatment matters.
The pictured paper cone, has a visible polymer layer that is about half the thickness of the cone, that helps with damping and keeping it breakup-free throughout the useable range.
The mfg. Is easily recognizable for some i guess. Still considered a paper cone.
I know Pioneer/TAD used to own they're own pulp plantation just to keep the cone material consistent and controlled, versus sourcing from different suppliers.
And even todays premium driver has cone breakup and resonances that can be treated or damped to a large degree.
Often just requires coating and manual labour which noone wants to pay for anymore.
Attachments
I think you're maybe asking the question a bit vaguely.
A better more focused question could be; what's the main difference in low-end performance with a cone that's less stiff?
I don't understand deflecting in this context. You can deflect a beam etc, not a pressure wave at these lower frequencies. Well maybe very far away by a building or other mechanical structure.
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Or are you talking about bending of the cone itself?
In that case I have a video for you guys, I have to look it up and share it somehow.
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Indeed a check, but only in combination with picture showing the cone shape.
Straight cones would show strong breakup rel to curved cones especially first and second mode , but curved cones start to breakup at lower frequencies. Too much curved and it will sort of collapse, regardless of what the fr resp shows.
It is not without reason that purifi stiffens the cone edge.
In the past a Philips engineer published a application to simulate the cone break up (first and second mode). The point i still remember is that paper has an upper limit in breakup frequency regardless of thickness.
To actieve higher breakup frequencies stiffer (young's modulus) is required.
As a side note, for midrange the pure thickness of the cone material matter, thinner is better. At least that was outcome of studies then at the time jacques mahul of Focal started with poly kevlar. Glueing in general then was also an issue, i did a lot of reglueing then ;-)
Here is an example what could happen when a cone isn't stiff enough and/or assembles well.
This video was taken about 9 years ago or so, at the company I was working for.
If I remember correctly we used a simple 240fps or 400fps camera.
We decided to record this because we could see visual damage after stress testing this woofer.
Needless to say that this specific woofer (Ciare in this case) was a no-go.
Other woofers/brands didn't have this issue.
This video was taken about 9 years ago or so, at the company I was working for.
If I remember correctly we used a simple 240fps or 400fps camera.
We decided to record this because we could see visual damage after stress testing this woofer.
Needless to say that this specific woofer (Ciare in this case) was a no-go.
Other woofers/brands didn't have this issue.
That's why it's called a worst case scenario analysis.
Or in other words, we know for sure that we can expect less change in Sd in practice.
You are right. I did not answer directly. The simplest answer is definitely a paper cone will deflect.
I still do use a stroboscope. It is instantly informative. And gives you a real world understanding of what is happening. Something that a simulation never does. That Ciare video is showing a situation where the surround is not capable of allowing the X-max the motor can supply. Very poor design practice. But very common.
cone flexing: yes, definitely an issue with woofers in small boxes where the back pressure can be huge. The cone flexing causes Sd modulation. The surround is the softest link in the chain to its Sd is also modulated by the back pressure. At some point all surrounds starts buckling. Thin paper cones for high sensitivity woofers don’t handle the pressure well. luckily, high sensitivity large drivers need huge box volumes to play bass so the pressure is lower
Then you need to think through the harmonics and sweep through the frequency range with your stroboscope. Your camera frame rate managed to catch it. That is proof it is possible to do with a strobe. In fact if you get the periodicity correct it can look like a real time movie. I have a Stroboscope considerably older than I from the 50's that works fine. And I have a new one that uses LED's The old one with the analog dial is actually easier to find your frequency with. Nice large dial and you turn up and down. Or you set you strobe frequency and sweep your driver frequency. Again thinking through harmonics and sub-harmonics. Even partials it quickly becomes intuitive. I'm pretty sure than like me many on this thread are musicians. Or at least were. That helps think through the harmonic progressions.
