Crossovers for Amrita Towers

Help needed.
I have a pair of Amrita towers. I believe they are the Reference series. I bought these new, many years ago. I have had them in storage since my divorce, for about 7 years, before that they worked fine.

The problem is..
Highs - are getting piercing. I am noticing this all the time now.
Mids - seem ok
Lows - certain notes are very distorted. More so when you increase the volume. (Dark side of the Moon; the opening heat beat sounds just terrible.)

At first I thought it was my Crown Preamp, so I took that out and put in my Lexicon MC1. This cleared up some problems, but I was now able to notice other problems.

Tried different sources, playing the same music, no difference
Hooked up a different amp. No difference
Hooked up a laptop direct to the amp, no difference.

Finally opened up the speaker, and found a problem with the midrange crossover network. Several of the caps were leaking.

Pictures will follow.
 
Some more details

Amrita Reference Tower??
1 tweeter
2 6.5" midrange
2 12" woofers (isoberic?) one is mounted directly in front of the other.

Being driven by a Rotel 5 channel amp at 200 watts per channel, bi amped.

I am going to start with the Midrange Crossover, since that is the easiest to get out. I KNOW I will have to do the Low end Crossover, but that is harder to get out. Need my daughter with her small hands :):)

The board seems simple enough. I plan on replacing all 3 of the electrolyte caps. In addition I plan on replaceing the 2 other caps, as they are not that expensive. Every thing else should be reusable?????
 
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The caps that I do NOT understand is the large 35uf 400v poly propo cap, surrounded by 3 sets of 3 electrolytic 60v caps.

1 35uf 400v
3 33uf 23v~ / 63v
3 10uf 23v~ / 63v
3 2.2uf 23v~ / 40v
First 2 sets are wired across the large cap
the last set is wired together before going to the rest of the electrolytic caps, and the middle one has reversed polarity?

Is there a better way of doing this? Any room for improvement?
 
The capacitors shouldn't be polarised so it shouldn't matter which way direction they are wired. The only exception to this is if they have placed two polarised capacitors back to back (+- -+) or (-+ +-) to create a bipolar capacitor with half the capacitance value - this is a trick used when two bipolar capacitors of twice the capacitance value are cheaper than a single bipolar capacitor.

Are you sure the caps are leaking and it's not just copious amounts of glue used to hold the components in place? Either way the speakers are probably old enough to warrant replacement of the electrolytic capacitors by now however.
 
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Replacing old caps can help, but I don't see any evidence of leaking... looks like hot melt glue or epoxy to me. The big black cap is a Solen metallized polypropylene cap I think. The yellow one looks like a PP cap (Bennic?).

You might try some other things with the speakers before doing crossover surgery:

1. Move them away from the corner! At least 1m away from any wall. If you can't do that, you might find the high end less emphasized if it wasn't reflecting off the side wall. Exchange left and right speaker positions so that tweeters are to the INSIDE and move speakers out from the corners.
2. That's one funny "Reference" design - who would design an MMT/MTM with the tweeter wayyyyyy over on the other side of the baffle?
3. DO NOT blame your preamp.
4. You might blame your amp, however. Check to see that the Rotel amp can handle the load of the woofers and mids that you are driving. I once owned a 6-channel Rotel amp (RB-956) and found that my speakers sounded kind of "flabby" when listening at med and high volume. I only figured out later that the drivers were 4 ohm and the amp was only rated for 8 ohm speakers. Using an amp rated for 4 ohms solved the problem.
 
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I will check the specs of the amp, but it sounded fine using the same amp for many years. I also tried my other Rotel amp, that I use in my computer room, with exactly the same results.

I will move the speakers to the correct positions.

The caps are leaking, I found a few with deposits on them, also, there was some kind of liquid that I got on my hand when I was removing the large cap bundle from the speaker.
 
Seems like a bunch of the Frako caps leaked. Since they no longer produce this type of cap, what would be a good brand to use? I would think I should use a cap designed for audio, since the Frako caps must of been used for a reason.

Should I replace the large resistors on the circuit board? ( I would think these should be ok?)

The big black caps I have found a source for.

What is the yellow piece wired alongside the black cap on the circuit board, marked 685K 150VDC? I would think it would be another cap, but what type? What value?
 
This looks a good speaker to me. But a lot of investigation and work to tidy up.

Twin mids and isobaric bass is not really changing the three way principle which I include below:
SEAS-3-Way-Classic

It does look like the bass section caps are leaking. The whole thing needs rebuilding IMO. I don't know what those little blue caps are, but they look like polar electrolytics, which is very odd indeed.

Anyway, you need to trace the schematic. Tweeter section looks like a poor first order to me. I think you need to rip them apart completely. You can figure out the wiring polarity and such easily enough. Make a note of whether the mids and basses are wired in series or parallel, it'll make rebuilding easier.

A modelling program and some similar starter designs is useful to draw up circuit diagrams:
Downloads
Something with 5 drivers would be a good start imported into projekte folder:
boxsim-db.de | Boxsim Projektdatenbank
 

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  • Troels 3-way classic.PNG
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