yes that was my phone autocorrecting 🙁
It's mostly H2, how disturbing that is really depends, ask mr Geddes for the math behind that.
Point is, HD distortion is a lot less problematic compared to IMD, and HD distortion at lower frequencies is even less problematic again.
So compare that to all kinds of distortion issues as well as other problems with more cone excursion in OB.
You can also soften the phenolic resin on the damper. Doing this does nothing in terms of an efficiency penalty until you soften so much that you cease to maintain a centering of the voicecoil in the gap.
What are viable methods to reduce the compliance of the spider. As K stated, softening the adhesive is possible, but difficult to achieve consistent results. Making holes in the spider in some regular pattern should be possible, but likely to cause stability and nonlinear behavior. Has anyone tried this and done thorough testing to show the results? I have done cone damping treatments, mass loading, dustcap removal, but never attempted to modify the spider/damper.
When I mentioned changing the compliance I was referring to the design side of a driver. I do this regularly. It's pretty much the number one thing that we tweak when we are working in a driver. The magnetics side if designed and calculated out correctly is pretty much a fixed and known part of the design. The soft parts are the area where you get to tinker. You need to understand what you are getting into once you start making holes in the damper/spider. And particles of steel in the enclosure will magically appear and get into the gap. Non-linearity of the damper is not really that much of an issue if you poke holes. You can try with a soldering iron. Spiders are set in their shape via a heated two part die. Phenolic adhesive is heat activated. Many times they are a fabric that can be melted via a soldering iron.
So, if you want to try and lessen the compliance of a driver like this be sure to sweep you enclosure well with a magnet to pickup any stray bits of steel that will end up killing your driver.
I would love to have the luxury of designing a high compliance woofer with a modern motor system. Currently, everything is designed to work in the smallest box possible and not self distruct in a vented system.
With modern DSP, you can add limiters to prevent bottoming. You don't need to have a highly restrictive damper.
Almost 100% of the time I design a driver so that it is not possible to physically damage the Voice coil by hitting the back plate. You can kill them other ways of course. But that way I try and remove completely.
Kartesian does it by combining two spiders.
One is acting basically as a last resort brake.
I have worked with a lot of DSP's and compressors, they definitely would take care of it. but I wouldn't rely 100% on them either.
So some mechanical brake would always be nice to have.
Keep in mind that a compressor is also not free from distortion (otherwise it wouldn't be a compressor).
As we just established above, the penalty in performance by a less linear stiffness is already very limited.
Keep in mind that compressors also limit the voltage, NOT the excursion.
So you better make sure you reach cone excursion limits well before voltage/power limits with a big margin.
Opening a whole new can of worms how you're gonna do this, parameters of compressors (time constants etc), how you trigger and what frequency band etc etc etc
So practically speaking, you run the risk of creating more problems than solving.
Obviously this is also mainly an issue with overhung designs.
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Clement is a very intelligent loudspeaker designer. I'd venture that the idea that one spider is acting as a brake is not entirely correct. It is usually done to keep the voice coil centered over a larger excursion range. You can design into a single spider a limiting of the excursion that will properly designed limit the voice coil from over excursion. Unless there is a driver that I don't know of I cannot think of anything that he has designed that has much more than 12mm or linear excursion. That is well within the centering abilities of a single spider.
That's how he explains it in his paper:
https://www.kartesian-acoustic.com/_files/ugd/f62092_c268dc37090843dab5e6e9d1540fcbf6.pdf
Not saying that I disagree with you, but I was just sharing Kartesian's philosophy. 🙂
Cool paper. I like his explanation of how he implements two spiders. And it is not a new idea. I'd argue that one spider is not do all the braking. But the two have the progressive rolls set up so that they sum near the desired maximum excursion. One spider stiffness if it is greater will dominate. What it looks like is that Clement is producing a very well thought out suspension for his driver.
If you have a problem with the air volume of your box
do not blame the air
or the spring called "spider"
do not blame the air
or the spring called "spider"
Yes, "spider" is a poor word choice for the "dampers", which is also a poor choice. I believe some of the very earliest were not compressed fabric, but cut metal/phenolic sheet that vaguely resembled a spider web. Damper is also a poor choice as damping is only a secondary function of the voice coil suspension ring.
b-force, thank you for the Kartisian white paper. That outlines my concerns for most modern woofers Kms (x) restrictions. I understand progressive control is necessary for pro audio applications, but with proper design not totally necessary for Hi-Fi use. Proper DSP limiter should be both dynamic and frequency based. Yes, this will cause distortion when it kicks in, but if you design higher X lim (2x) than X-max, you will be getting BL (x) distortion before reaching the limiters.
The problems I run into is working with people all over the world. Spider is not exactly an international English term. Damper seems to get part of the idea across. When I talk with Haken about a new suspension design they use damper. So that's what I tend to use.
I think I missed something
thanks ! ........... j.
how do small particles of steel get into the enclosure? Are you speaking in a general sense, or only about this particular operation of lowering the compliance of the spider?
thanks ! ........... j.
That's very cryptic, lol
I think you mean this one?
https://secure.aes.org/forum/pubs/conventions/?elib=7684
It's evil, and happens more than you might think. Why a well designed driver has some protection against this possibilities. Most problematic win assemblies. Like radios, TV's etc.