Hi all,
I recently managed to pick up a pair of Mission/Cyrus 781 speakers in pretty good condition, although missing their front covers, (I will fabricate new ones, but more on that and cab refurbishment in another post later...).
The reason for this thread is two-fold,
1) I extensively searched trying to find the crossover components to no avail, there is limited information on this model and alot of people have this models info mixed up with the later MISSION 781. Therefore I am putting this info out there in case anyone else needs this information.
2) I am open to part replacement suggestions, not values, they will be like for like, but type/make/series.
So, here we are,
on the high/tweeter side we have;
1 x EXPOTUS 7w 1.5ohmJ wirewound ceramic encased resistor into,
1 x 4.7K 250v CH MER capacitor which I think is a 4.7uF Aluminum Electrolytic.
On the low/woofer end we have;
1 x EXPOTUS 5w 2.2ohmJ wirewound ceramic encased resistor into,
1 x 6.8uF 50v np capacitor, (this I will double check on the other x-over as the skin of the cap tore from the body whilst removing it from the hot glue).
I researched "Expotus" and it turns out they are a specialist audio component manufacturer, however, their minimum order is £100!!!!!
I suppose it is quite possible the caps are Expotus as well as the resistors...
So what do you think, like for like, or something else??
I recently managed to pick up a pair of Mission/Cyrus 781 speakers in pretty good condition, although missing their front covers, (I will fabricate new ones, but more on that and cab refurbishment in another post later...).
The reason for this thread is two-fold,
1) I extensively searched trying to find the crossover components to no avail, there is limited information on this model and alot of people have this models info mixed up with the later MISSION 781. Therefore I am putting this info out there in case anyone else needs this information.
2) I am open to part replacement suggestions, not values, they will be like for like, but type/make/series.
So, here we are,
on the high/tweeter side we have;
1 x EXPOTUS 7w 1.5ohmJ wirewound ceramic encased resistor into,
1 x 4.7K 250v CH MER capacitor which I think is a 4.7uF Aluminum Electrolytic.
On the low/woofer end we have;
1 x EXPOTUS 5w 2.2ohmJ wirewound ceramic encased resistor into,
1 x 6.8uF 50v np capacitor, (this I will double check on the other x-over as the skin of the cap tore from the body whilst removing it from the hot glue).
I researched "Expotus" and it turns out they are a specialist audio component manufacturer, however, their minimum order is £100!!!!!
I suppose it is quite possible the caps are Expotus as well as the resistors...
So what do you think, like for like, or something else??
Attachments
Unless you overheat them resistors age so slowly that there is no need to replace them. Similarly the MER 4.7uF capacitor is a metalized polyester film capacitor. These do not age quickly and it is highly unlikely that it needs replacing. the only component that really needs replacing is the 6.8uF NP capacitor.
If it really is 6.8uF (not 68uF) then I would replace it with a metalized polyester or a polypropylene. Generally polypropylene is considered to be the better dielectric as it has lower dielectric loss however you would be hard pressed to hear the difference. If it is a 68uF then a higher voltage non polar electrolytic would probably sound better, polypropylene in this size will be very expensive and I doubt you would find metalized polyester. You could look at putting a smaller polypropylene in parallel (typically 3.3 - 6.8uF) with it to bypass the electrolytic in the upper midrange.
If you change it you are most likely to hear the change in frequency response as it will almost certainly be a different value from the electrolytic which by now will have dried out a bit.
Regards,
Andy
If it really is 6.8uF (not 68uF) then I would replace it with a metalized polyester or a polypropylene. Generally polypropylene is considered to be the better dielectric as it has lower dielectric loss however you would be hard pressed to hear the difference. If it is a 68uF then a higher voltage non polar electrolytic would probably sound better, polypropylene in this size will be very expensive and I doubt you would find metalized polyester. You could look at putting a smaller polypropylene in parallel (typically 3.3 - 6.8uF) with it to bypass the electrolytic in the upper midrange.
If you change it you are most likely to hear the change in frequency response as it will almost certainly be a different value from the electrolytic which by now will have dried out a bit.
Regards,
Andy
gfiandy, thankyou for the reply.
Although I take your comments on board, these speakers are nearly 30 years old and regardless of the perceived longevity of any one component, my mind is set on replacing all....after all, it does not cost much...pennies in fact, (unless I opt for, in my opinion, needless "upgraditis" options).... It can't be detrimental and will give me the confidence that they will last a good length of time....peace of mind, if you will!!
Although I take your comments on board, these speakers are nearly 30 years old and regardless of the perceived longevity of any one component, my mind is set on replacing all....after all, it does not cost much...pennies in fact, (unless I opt for, in my opinion, needless "upgraditis" options).... It can't be detrimental and will give me the confidence that they will last a good length of time....peace of mind, if you will!!
.....
I'm also upgrading a pair - tweeter resistor in mine is labeled 1.2ohm. The 4.7uF poly cap measured 4.8, but I'm putting a modern Solen +/-2% in anyway. The 6.8ohm rubbish measured 8.4ohm !! Also a Solen replacement. The aircore inductor will be kept but the ironcore (1.5mH, 0.54ohm dcr) is being swapped.
Hope this helps!
David
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