Thursday, 26 October 2017

CSS EL70eN frame dampening

I know, it's been a while since my last post, but life has kept me busy and away from the audio world.

This summer I brought my dMar-Kel70T to the local hifi-store to try them with better amplifiers but also to let the store owner have a listen to them.
My dMar-Kel70T next to some Dali and B&W speakers at the local hifi-store

The store owner, who has probably been in the audio business since before I was born, thought they had a "nasal" tone and I do agree with him. Without some sort of EQ they can be a bit too nasal. At home I use a MiniDSP to control that and it makes a massive difference, bringing them from sounding like a pair of $500 speakers to >$1000. One suggestion he gave me was to dampen the driver frame and bezel. Since they are a lightweight plastic they do ring quite a bit at certain frequencies, which surely has a negative impact on the sound.

I did some googling and found this thread at the forums. None of the materials suggested there were easily available (or cheap enough) for me. I did some research and found that blu tack would probably suit my needs. It sticks well, is easy to shape, has a high density (around 1.8g/cm^3), sticks to things, and isn't crazy expensive for the amounts that I would need. I bought two packets for 29SEK each (~$3.50/ea). Each pack has six strips each weighing 10g.

The drivers before my mod.
Note that these have already been partly modified by Dave at Planet_10 hifi
I had no idea how much blu tack I would be able to fit in there. On the first go on the first driver I managed to get around 2.5 strips in there. Then I figured I could use a stick to press out the blu tack better into the spaces, so then I could fit even more in there. In total I used around 40-45g per driver.
Side view of inishedd driver
I also put some on the "legs" of the frame just to add some extra mass to it.
Top view of finished driver
So now to the important question: do I hear any difference? I can't say for sure, but there is a noticeable difference in vibrations in the frame. I started out doing just one driver, put it back in the enclosure and played some music on both speakers. The untreated driver frame had a lot more vibrations in the mid-range frequencies. The untreated driver made a higher pitched (and louder) sound when tapping on the bezel compared to the treated one.

Was this mod worth my time and money? I don't know, but why not? At least I can now have peace of mind knowing that I have done what I can to address the problem.

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