bluemonkeyflyer
Headphoneus Supremus
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- Jan 20, 2011
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Thanks for the informative post. Your graphs support your hypothesis. I'll have to try various types of microfiber with rock wool and then with cotton.
You're correct about rockwool, at least Grodan, having consistent density. I used a bread knife with a very sharp blade and a thickness guide attachment. I set it at 1 cm and that's exactly what I got. I did not remove the rubber shock absorbers. I notched the rockwool for all 4 posts and pressed it in place. I filled any gaps with scrap rockwool. Seems to work great and I retained the benefits of the rubber caps: decoupling the cup from the baffle to reduce vibration.
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You're correct about rockwool, at least Grodan, having consistent density. I used a bread knife with a very sharp blade and a thickness guide attachment. I set it at 1 cm and that's exactly what I got. I did not remove the rubber shock absorbers. I notched the rockwool for all 4 posts and pressed it in place. I filled any gaps with scrap rockwool. Seems to work great and I retained the benefits of the rubber caps: decoupling the cup from the baffle to reduce vibration.
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I'm using actual 003 pads.
I had to think about which mod I preferred. Of the two mods I consider distinctive, I think I'd suggest the thin microfiber/rock wool mod over the plush microfiber/cotton mod. Two my ears, they both sounded very good and measured well. But there are some practical considerations that cause me to favour the rock wool-based mod.
My results with the rock-wool mod have been reproduced by BMF but he couldn't get the microfiber/cotton mod to work to his liking.
Plus, with the microfiber/cotton mod, it requires that you use specific materials with little room for variation. And, as we all know, there's a lot of variation in cotton filling. Everything from teased cotton balls to absorbent cotton and cotton from nursing pads. And I got lucky with the plush microfiber I used. I found it at a discount store and haven't seen anything identical since.
On the other hand, Grodan rock wool is readily available in small amounts and the company says the density is uniform at 70 kg/cubic meter. Rock wool does a good job of mopping up the backwave and resonance in the cup. And the lens cleaning cloths I use are everywhere and they're cheap. Although they have a large variation in porosity, I view this as being a good thing with this mod. You can swap out different samples of microfiber and tune the upper end of the spectrum to your liking. And you're not limited to microfiber (see chart below). My hypothesis is that the more porous the driver covering, the warmer the sound. The less porous/more reflective the material, the greater the emphasis on the mids and treble. (You can judge the porosity/permeability just by blowing threw the material and assessing the resistance.)
Here's what I mean. The chart below plots the frequency response of the rock wool mod using four different driver-cover materials. Note how the response curves begin to diverge at around 1 kHz. The plush microfiber gives the greatest treble boost, then, in descending order, lens-cleaning microfiber, cotton from a nursing pad and a naked driver (covered only with the stock white material). This rank order is pretty consistent with how I'd compare the materials using the aforementioned and patented MoBlow® test.
I think the semi-rigid nature of rock wool could also mean that mods will be more durable and less likely to shift. But that's conjecture.