SpeakerTalk

[sorenb]

Have been restoring an old pair of KEF 104.2: new surrounds for the internal woofers, replaced the ferro fluid in the tweeter and replaced all caps with a set from Falcon Acoustics, and have a few questions in that regard?

After replacing the fluid, applying new fluid by eye balling. Noticed different output from the tweeters. Re-moved the ferro fluid once again, and re-applied using a syring so each got close to 0.1ml.
Hereafter the output sounded very much identical.

Is the amount of ferro fluid very critical to correct function?

Before replacing the caps the speakers sounded a bit muffled and harsh at times. After replacing much better, using my Maggies as ref.

Now, all caps I have replaced seems to be very close to correct value, and ESR is between 40-100 mohm ... apparently the components should work, however the result seems to contradict this, any idea as to why?

[oldandintheway]

Are you saying they sound worse since the cap replacement? Maybe they need to bed in?

[sorenb]

Quite the opposite:
Before replacing the caps the speakers sounded a bit muffled and harsh at times.
After replacing much better.

Since the caps are more than 30 years old, I would expect them to be worn out by now.
However, they all measure very close to specified value, and ESR below 100mohm, and thus seems to be working correct although sounding bad.

I am just wondering how to spot bad sounding caps ithen?


As for the ferro fluid, I haven't seen any recommendation to be very accurate when applying. However, my experience seems to suggest that using a syring for controlling the amount is actually needed.
The two tweeters where clearly different in output (hearing not actual measurement) after applying by eyeballing.
re-applying using a syring and aiming for 0,1mL, they sounded identical.
The postings by Speakerguru suggests (as far as I understand) that the fluid is only there to enhance power dissipation. So, I was just wondering whether the ferrpfluid enhance the sensivity or whether a bibt too much would attenuate the tweeters somehow.

[audiolabtower]

Perhaps a surplus of viscosity makes the coil more difficult to move and thus reduces sensitivity to produce a less bright sound?

[oldandintheway]

I don't think the qty of ferrofluid should change the viscosity, but it being ferrofluid may change things! More magnetic material (in the ferrofluid) will change the way the magnetic flux interacts between the permanent magnet and the voice coil. I tried my tweeters with no ferrofluid (low volume only) and they sounded ok (i wanted to check before i continued!).

I did find out that one of my voice coils had come detached from the diaphragm (i had used rubber cement and the excess ferrofluid had softened the cement). So keep an eye out for that too.

I know it sounds basic, but did you check the crossover connections? If you replaced everything and they check out good, i see no reason why they would sound 100% unless they need to get worn in with a sound thrashing!

[sorenb]

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