Mills resistors

[VantheMan]

You should hear the brush work and cymbals on "Waltz for Debby". On my favourite test disc ( Riverside re-re-re- issue) I once used to liken it to the North Sea on a bad day. Since fitting the Mills, it is finally recognisable as a middling to poor live recording of a drum set.

[VantheMan]

Having external crossovers and space not being a problem I have now fitted some 9.7uF Russian MBGO-2 caps and 0.47uF FT3 teflons to replace the Soniqs 6.8 and 3.3uF tweeter caps. Yes, as was not to be expected, bass has improved quite a bit (deeper and more varied) as well as air and separation higher up. They seem to change from day to day (teflons are supposed to be like that at first) so let´s see if the improvements consolidate or I make my mind up.
Being a technical no-no, I have no idea if the Soniqs are good, bad or neutral but they might certainly bear some closer study (not by me) by someone with greater experience of caps because in my case they certianly seem to have been holding the WD25TExs back a bit.
He says, ducking.

[bob orbell]

May I ask, why have you changed the value so dramaticly ? BOB

[VantheMan]

Hi Bob,
The tweeter series caps for the Wd25TEx (Millennium tweeters) according to The Next Step article by Peter are :
6.8 + 3.3 = 10.1 uF

I used :
9.7 + 0.47 = 10.17 uF

Maybe the values for other tweeters are different.
Cheers,
Chris

[bob orbell]

Thank's Chris, I follow you now. BOB

[pre65]

Originally Posted by VantheMan

Hi Bob,
The tweeter series caps for the Wd25TEx (Millennium tweeters) according to The Next Step article by Peter are :
6.8 + 3.3 = 10.1 uF

I used :
9.7 + 0.47 = 10.17 uF

Maybe the values for other tweeters are different.
Cheers,
Chris

And what was (or is) the tolerance on those capacitors ?

+/- 10% ?

[VantheMan]

Hi Philip,

The Russians were bought matched to values as confirmed on measuring them here and the Soniqs were spot on to 1 decimal so any variation was in the second decimal. I don´t think it´s down to differing values - just to the differing types.
With just 6-7 hours on them max., sound through the Russians seems to differ from one day to the next so let´s see if I can get a real handle on them after 20-30 hours time. All I will say is that I´m enjoying the trip at present.
As to be expected, my engineer mate says it´s all rubbish and that caps of the same value must sound the same as all they do is filter frequencies - the difference being a result of different tabs hearing different things. I´m not arguing- my tabs must ave a lot of imagination, I guess.
Chris

[VantheMan]

Considering the relative success of my crossover upgrades so far, my next step will be to change the series bass coils. As you may know the originals supplied are ferrite cored 0.76mH and 0.2R. I have seen some air core 0.76mH Jantzen toroidal coils but the DCR is around ten times lower ( 0.02R ). Would this be a mistake or are lower inductance values to be encouraged ?

[Richard]

Originally Posted by VantheMan

Considering the relative success of my crossover upgrades so far, my next step will be to change the series bass coils. As you may know the originals supplied are ferrite cored 0.76mH and 0.2R. I have seen some air core 0.76mH Jantzen toroidal coils but the DCR is around ten times lower ( 0.02R ). Would this be a mistake or are lower inductance values to be encouraged ?

Lower DCR of series bass coils is to be preferred as it will help the amp's electrical damping but do check those air cored ones are actually lower. It's usually the opposite way around; ferrite core inductors are usually lower DCR than air core types of a similar inductance value as the core makes them more efficient (hence shorter wire and more compact size). Ferrite cores are only a problem if they are under specified and the core saturates. Yes when changing inductors the DCR must be considered as it will attenuate all frequencies (whereas the inductance value affects the chosen frequencies by reactance).

[VantheMan]

Thanks Richard,

You were right. Mundorf air coils do have much higher DCR and the Jantzen coils I saw for use in woofer circuits are toroidals but they do have a "sandwich" core (0.82mH and 0.03R) , for use in high power/heat situations .

I live in the Canaries where year round ambient temps are constantly in the 20+º and in my opinion this does affect caps - I had to change the bulging Eurocaps (65º spec.) in my Sugden A21SE for Panasonics with higher temp. values (105º), despite Sugden´s protests to the contrary. Of course I´ve never had occasion even to imagine that crossover coils expel heat !

Jantzen however have some simple (cheap) air cores (0.76mH and 0.17R) and some dearer Wax Cils (0.76mh and 0.22R) so I guess I´ll have to toss a coin unless I can order the toroidals to the mH value.

Will keep the thread informed.