Castle Severn 2 Cross-over Caps

[hagzo]

I'm taking the opportunity while self-isolating to refurb an old pair of Serverns i've had kicking around for a while.

I re-guled the paper cone of the 4" driver to the spider the other night and pulled the crossover out - I felt after over 20 years old that the speakers would benefit from new capactitors and resistors to help improve the seperation and soundstage.

My problem is that the existing MMP capacitors are quoting 'J' values, and i cannot see the 'uf' value anywhere on the cap to let me order new ones.

4.7J 250V
10.0J 250V
12.0J 250V

I was hoping someone here could help point me towards suitable replacements.

Also while looking over the crossover i noticed a lot of brown marks below the solder points. I thought at first that this was oxydisation but then thought it might be glue used at manufacture to secure parts to the cross-over? I am basically asking whether this brown stuff affects the perfomance of the cross-over?

I've attached a picture to help, and any advice anyone can give would be great.

Keith

27574

[M6NTL]

Hi,
They are Metallised Polypropylene capacitors, and won't need replacing like old Electrolytics would - there's nothing in them to 'dry out'.
The brown spots are just flux from the flux cored solder used, perfectly normal, nothing to be concerned with...

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[Pharos]

I agree, and also doubt the benefit of replacing resistors unless they look aged, and that all looks in good shape to me.

[Made in 1968]

Agree but some cheap Polypprops are nasty. I do Ansar Supersounds every time
[4.7uF]
[10.0uF]
[12.0uF]

[M6NTL]

Agree but some cheap Polypprops are nasty. I do Ansar Supersounds every time
[4.7uF]
[10.0uF]
[12.0uF]Ansar Supersound - formerly known as SiderialCap...

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[Made in 1968]

Not to me knowing. I bought Ansar when they very first came out in the early 90's. They are an excellent pro/Mill spec cap. Not an over priced Boutique cap.

[M6NTL]

Not to me knowing. I bought Ansar when they very first came out in the early 90's. They are an excellent pro/Mill spec cap. Not an over priced Boutique cap.Me too - used to get mine from RATA...

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[Made in 1968]

Thats where i was first introduced to them. My first project was rebuilding the X Overs in a pair of Diesis 'DF-2' With Supersounds & RATA Iron core inductors. I don't like using the word Night & Day but boy that was Night & Day.

[sailor]

Hi Keith,

Just seen your post. As the XO is the heart of any speaker it is worth spending time and money on. I see a number of things you can do, what and how much depends on your budget.

At the very least replace the cap in series with the tweeter and change out that nasty, noisy sand cast resistor. They sound bad wherever used including power supplies. Minimum is a Mills 12W. I can mention others but don't know how far you want to take this.

It would help if you gave some indication of what you hoped to achieve regarding the overall balance. For example, would you like a more incisive sound, more top end detail, a brighter or more mellow sound.

Were it mine I would remove the coils and dump the rest. I would rebuild it on a bigger board to get greater spacing between the coils. I would replace the smaller coil with a quality air-cored one. You need to know its mH value. Measure it, take it to be measured or check online for XO schematic.

Definitely replace all caps. Its not expensive today to improve on 20 year old caps and makes sense if you go for a complete rebuild because they will have long leads allowing you to connect component to component in a point to point build, avoiding PCB traces and random bits of wire.

I would also do away with the auto-style connectors and solder directly from crossover to driver terminals. I think I assume correctly looking at your XO pic, that the same horrible push-ons are used to connect to the drivers. Again rather solder.

Good luck with this and if you know the direction you want to go I can give you names of brands to consider.

[hagzo]

Hi there, thank you for the replies and sorry it took a while to respond to the helpful comments - the reponses themselves gave me more food for thought, and I had to consider what i was wanting from these speakers.

I originally supposed that a simple capacitor upgrade would bare little improvement and this was backed up by a few members. Then the suggestion from Charles to identify what i was looking to improve with the speaker meant i had to go back and listen to much music - bonus.

The reason i keep going back to these speakers is because most commonly percieved non-sh!te speakers i have tried in the difficult room they sit don't work......and the Mrs likes them.
These small footprint Castles do work with both the bass and midrange sounding great. Where i am looking for improvement is in soundstage (or depth of it) and a little improvement in clarity of the treble.

The idea i thought might be good from reading on-line material (and achievable given my level of technical ability) was building a cross-over by mounting the parts direct to a non-pc board with silicon or hot glue. Then wiring the parts together point-to-point with final direct connection between the drivers and the plugs.

Based on the above, would it give the improvement in the areas that i mentioned? or am i simply spending money to achieve something that can't happen?

The speakers don't owe me anything now, and i am not a castle puritan, but they are surprisingly good in some areas. If they could be sensibly improved where they lack it would save me continually buying different speakers in an effort to find the right ones, when i feel i am close with these.

sorry for the ramble

Keith

[sailor]

Hi Keith, rebuilding the XO with good parts will minimize the damage components do to the signal. My previous recommendations stand. This will provide a cleaner and more detailed signal which will give you the clarity in the top end and also improve bass and midrange. This may seem a little hard to comprehend when the main target of this rebuild is to improve the tweeter's response.

What is at play here is that the upper harmonics of voices and instruments, from the drummers side tom, snare drum and other instruments going upwards, is reproduced by the tweeter. The transient performance is crucial for life-like sound, this stems from our senses being tuned for survival in the wild. The sharp snap of dry twig alerts you to danger and gives its location.

The transient or leading edge of the waveform is handled by the tweeter so when you provide it with a cleaner signal your ability to recognise and locate their position is enhanced, hence better imaging and staging.

I mentioned using Mills resistors. Use the 12W and not the 5W. Remember you are looking to maximise the transient snap and the bigger resistor will cause less thermal compression, and that's good. This is an excellent choice, noticeably better than that grainy thing used in your XO and used by many so called high-end designs. For a more precise response, and is what I like using, and feel may suit your speaker better is the Powertron, a Vishay foil. rated 3W or 30W when mounted on a heat sink.

Caps are another story and you still haven't disclosed your budget :scratch:
Here are some to consider: prices in GBP for a 4.7uf as reference.
Clarity Cap ESA 6.58
Jantzen Superior Z-Cap 15.5
Mundorf M Cap EVO Oil 7.43
Mundorf M Cap Supreme 22.24

All priced from : https://www.hificollective.co.uk/components/capacitors.html

The Clarity good for bass/mid driver. The tweeter series cap is where the bulk of your budget should go. The Mundorf Oil has a very slightly lit up top end. This is not a bright cap, just adds some brilliance. The M Cap Supreme is one of my favourites and is lovely. Jantzen great value.

Posting a schematic of the XO or emailing it to me would help. charleswasserfall@gmail.com

Rewire with solid core OCC copper.

Cheers
Charles