Background Wanted to get more low bass (under 70 Hz) so tried the CC ring mod. Findings:
- Open foam, “3” foam, no foam, and no ring (after the mod) give more bass, but ranging well above 70 Hz, and also muddies the estimable timbre and speed of the bass.
- Gray and blue foam decrease bass.
- Both combos increase output at 3k and occasionally noticed at 6k. But it’s more than just output, it is edgy. Think its because the driver whose resonance is around 70 Hz is now moving more below that point which results in increased IM – quite unwelcome.
FYI: Been using the 600’s modded for 5+ years: Custom Cans XLR & small amounts of dynamat on the back side of the cup, not blocking any of the vents. Not for mass loading, but to quiet the vibrations of the plastic cups. (Fig 1).
Basically tried the kitchen sink to restore the OG sound. Mods such as filter papers, cloths, and foams under the spider, and on the inside of the rear cups. Tried these small diameter metal tubes (button snap post) on top of the CC weight (Fig 2), even tried different diameter and length tubes to vent the front facing driver through the pads.
Conclusions:
The rear cups and pads that go with them are the best choice.
Don’t do the mod if you like the OG timbre. They are not LCD-4’s and never will be. If you want that, get that.
Given the materials at hand, to restore the sound closest to OG: 32 ct undyed linen (Fig 3) cut to fit under the spider and then notch it in 8 spots so that it lies flat under the spider, then cut the original under spider foam to fit the inside diam of the spider, and install it. Fig 5. The choice of this linen cloth is due to testing done that showed a consistent 2-3 db drop in output from 1.5k-15k. Since it’s on the back side that effect will be minimized, but still have some use and listening tests did indicate it was the best tried here.
If you insist on getting more bass using the CC ring and get the closest to OG treble:
- Inatall the linen and OG foam mod (Fig 5).
- Then install the post (Fig 4) – prefer the larger diam one (6 mm)), add the tack to keep it centered (from the visible side, don’t goop it up under the copper lip). It’s the best combo I found using the CC weight, but it's still not back to OG.
Tried to block all the vents on the back including the CC mod covered with just the front bass tube outlet. Very wanky sound.
Wish I never tried the CC mod, and recover those dozens of hours of mods. Like CC cables very much, great customer support. At least for the HD-600 not my cuppa. No opinion on the variants.
Note: I may have access to a testing rig on 10/21, I’ll test the two mods and report back. (I did - a GRAS clone - showed distinct broad peak in the 3-4k area, and just a bit of bass added - all over 70 Hz)
Add: More listening confirms I don't like any combo of the CC weight, so when I want bass impact/reach etc. - all my other cans on the Rag 1 were always the answer in the first place.