What type of capacitors should I put in my AR-90s crossovers?

[Kuja]

Hello,

I want to recap crossovers in my "new" AR-90s.

In my previous restorations I used polypropylene caps manufactured by ICEL in Italy.
This is a very popular audiophile brand in my part of the world.

BUT...

I run across some threads saying that modern poly caps are not good, since they will change the voicing of old AR speakers.
The theory is that poly caps have lower ESR, and that using them will result in speakers having more treble and upper frequencies.

Did anybody confirm that in real life, or is it just hear-say?

I would like to be able to use poly caps due to their long life.

Any thoughts?

Thanks in advance,

Aleksandar

[sdclc126]

I'm quite confident what you've heard/read is not true. Poly caps are widely used and are likely superior to their predecessors.

Go ahead and use them.

[kevinkr]

My experience with the AR 58S which was marketed during the same period as the 90's indicates that this is in fact a concern. I upgraded the cross-overs in my pair and the bass alignment shifted drastically to my very considerable surprise, and sonically not for the better I might add. (Baffle step compensation ???)

I did not note any particular problems with the mids or treble performance of the speaker system.

The solution is simple - if you note a drastic negative change in sonics just add a small amount of resistance in series with the cap.

The capacitors in these x-o are so old at this point you really should rebuild the x-os.. Actually I would recommend you build totally new ones with air core inductors and fine tune until you get all of the performance the speakers are capable of. Keeping the old ones will allow you to use them as a baseline. All of the parts you will need are available from madisound.

[Kuja]

Originally posted by kevinkr
My experience with the AR 58S which was marketed during the same period as the 90's indicates that this is in fact a concern. I upgraded the cross-overs in my pair and the bass alignment shifted drastically to my very considerable surprise, and sonically not for the better I might add. (Baffle step compensation ???)

I did not note any particular problems with the mids or treble performance of the speaker system.

The solution is simple - if you note a drastic negative change in sonics just add a small amount of resistance in series with the cap.

The capacitors in these x-o are so old at this point you really should rebuild the x-os.. Actually I would recommend you build totally new ones with air core inductors and fine tune until you get all of the performance the speakers are capable of. Keeping the old ones will allow you to use them as a baseline. All of the parts you will need are available from madisound.

Hello,

You said that "the bass alignment shifted drastically".
What did you exactly do regarding upgrading you crossovers?

I'm expecting to have problems in higher frequencies, with them being more pronounced with modern lower ESR caps.

I plan to keep the old inductors, since they already are air core and they are wound with really thick wire.

Thanks!

[QSerraTico_Tico]

Originally posted by Kuja
Hello,

I want to recap crossovers in my "new" AR-90s.

In my previous restorations I used polypropylene caps manufactured by ICEL in Italy.
This is a very popular audiophile brand in my part of the world.

BUT...

I run across some threads saying that modern poly caps are not good, since they will change the voicing of old AR speakers.
The theory is that poly caps have lower ESR, and that using them will result in speakers having more treble and upper frequencies.

Did anybody confirm that in real life, or is it just hear-say?

I would like to be able to use poly caps due to their long life.

Any thoughts?

Thanks in advance,

Aleksandar

You sure will change the voicing if AR used bipolar electrolytics and metallized paper!
Perhaps Clarity Caps are in idea to try.
Contrary to the name these are not as bright and unforgiving as most other polypropylenes.
Are you sure you need a recap? The Sprague electrolytics I found in AR3a were still right on value after 30 years!

[Kuja]

Originally posted by QSerraTico_Tico



You sure will change the voicing if AR used bipolar electrolytics and metallized paper!
Perhaps Clarity Caps are in idea to try.
Contrary to the name these are not as bright and unforgiving as most other polypropylenes.
Are you sure you need a recap? The Sprague electrolytics I found in AR3a were still right on value after 30 years!

Here are some photos of the crossovers in my AR90s, along with the schematics...

Note those black caps with red cross sections and the white one with yellow cross section. They almost look like modern polypropylene.

All caps are original.

http://hifi-forumi.com/forum/download/file.php?id=9834
http://hifi-forumi.com/forum/download/file.php?id=9832
http://hifi-forumi.com/forum/download/file.php?id=9831
http://hifi-forumi.com/forum/download/file.php?id=9830

http://hifi-forumi.com/forum/download/file.php?id=9835
http://hifi-forumi.com/forum/download/file.php?id=9836

Schematics:

http://hifi-forumi.com/forum/download/file.php?id=9838
http://hifi-forumi.com/forum/download/file.php?id=9837

Are you sure you need a recap? The Sprague electrolytics I found in AR3a were still right on value after 30 years!

I've been told that capacitance in old caps might not change much over years, but that the ESR will become much higher, thus efectively reducing the output of the drivers.


.

[QSerraTico_Tico]

My goodness....
What a lot of parts.
I think those black bipolar electrolytics with the red ends are not good quality.
I saw then a lot in UK made loudspeakers. They really veil the sound.
If you replace these by polyprops you change the sound a LOT!

[kevinkr]

The yellow ended white jobbies are film caps - you don't need to replace those.

Can't say about the black ones..

The 58s used much cheaper caps that what you show.

Perhaps you don't need to do anything at this point...