MAGNAT All-Ribbon 2 Crossover - Upgrade Required?

[SONDEKNZ]

I decided to use the LOCK-DOWN time to peep inside our beloved MAGNAT All-Ribbon 2 speakers - circa 1990, Germany - and check-out the crossover.
(No sound issues - just curious...)

So here's a quick pic.

To these eyes, this appears to be a pretty respectable bunch of components.

Looks like a decent polypropylene cap for the tweeter.
(Please correct me if I'm wrong...)

Air-gap inductor. Nice.

And huge copper ground-planes on the reverse of the crossover.

At 30-years old, one would suspect that the (bipolar) electrolytic caps need to be replaced - assume these are for the woofer - but a bit hard finding suitable alternatives that are not electrolytic.

I know sand-cast resistors have a few detractors, but I have always figured that if DC is not present - as it absolutely should not be - it shouldn't make a difference.

Any thoughts from the panel as to some quick wins here?

I have some nice, low-value MOJO polypropylene caps lying around for bypass duties, if anyone can see the need.

Or should I leave as is?

(No. Sadly, my new ESR tester has not yet arrived...)

 

[AllenB]

At 30-years old, one would suspect that the (bipolar) electrolytic caps need to be replaced

I don't know. Usage, temperature, modern construction, internal bulging, internal shrinkage? Maybe you can measure its value?

 

[adason]

Where are the ribbons?

 

[UserAbuser]

MKT = Polyester.
A step below polypropylene.

27uf isn't really that big for a polypropylene these days.

 

[SONDEKNZ]

Where are the ribbons?

Where are the ribbons?

Ribbon-shaped voice coils used on metal-dome tweeters.
Makes for remarkable high frequency extension and ”air”…

 

[Sonce]

At 30-years old, one would suspect that the (bipolar) electrolytic caps need to be replaced - assume these are for the woofer - but a bit hard finding suitable alternatives that are not electrolytic.

Replace the bipolar electrolytic capacitor with a new one (bipolar electrolytic also). Keep everything else as-is.

 

[raymondj]

I think Sonce has it in a nutshell.

If you have been happy all these years, the 27uf Bipolar electrolytic is the only sensible candidate for a replacement. I like the Mundorf ones. Not expensive, and not too large. Check the basic dimension to ensure it will fit before ordering or hitting the buy now button.

Have fun.

 

[manninen]

I decided to use the LOCK-DOWN time to peep inside our beloved MAGNAT All-Ribbon 2 speakers

So you have time...

measure raw drivers dual channel on the box 0-180deg
take impedance curves
throw all data to vituixcad

start simulating old crossover.

I´ll bet you can make it better than original

 

[SONDEKNZ]

Total Crossover Re-design... Nope.

So you have time...

measure raw drivers dual channel on the box 0-180deg
take impedance curves
throw all data to vituixcad

start simulating old crossover.

I´ll bet you can make it better than original

Thanks for the vote of confidence, MANNINEN.
I simply don't have access to the equipment, to make the types of measurements required.
That said, I believe the Germans made a great job of the original, as these speakers sound sensational.

 

[SONDEKNZ]

I think Sonce has it in a nutshell.

If you have been happy all these years, the 27uf Bipolar electrolytic is the only sensible candidate for a replacement. I like the Mundorf ones. Not expensive, and not too large. Check the basic dimension to ensure it will fit before ordering or hitting the buy now button.

Have fun.

Thanks SONCE and RAYMONDJ.
I had pretty much come to the same conclusion on the bipolar cap - but 27uF values are not easy to find. MUNDORF appears to do a 22uF before jumping to a 33uF, so I may have to do a bit of "combining".
Let's see what I find...

 

[manninen]

So no any measuring equipment? I would not touch it all

 

[SONDEKNZ]

So no any measuring equipment? I would not touch it all

Agreed.
Just waiting for my new ESR METER to arrive.
Measure thrice. Cut once.

 

[DickHertz]

It would be nice to confirm the 27uF capacitor was within spec. Maybe replace the cast resistors with Eagle, Lynx, or Mills resistors. Otherwise, I'd leave it alone.

 

[AllenB]

Just waiting for my new ESR METER to arrive.

That's one way to do it.

replace the cast resistors

You don't like wirewound?

 

[DickHertz]

I believe the replacements I recommended were wire wound. The sandcast resistors in the crossover are the cheapest of the bunch and the harshest sounding.

 

[giralfino]

I had pretty much come to the same conclusion on the bipolar cap - but 27uF values are not easy to find.

Hard to find, yes, but they do exist, at least Jantzen makes one. Do yourself a favor, source them and do nothing else.

Ralf