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Multi-Way Conventional loudspeakers with crossovers

Mordaunt Short - Carnival Series 2 (1976) Crossover and Tweeter Help Needed!
Mordaunt Short - Carnival Series 2 (1976) Crossover and Tweeter Help Needed!
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Old 9th November 2019, 12:19 AM   #1
lhalha is offline lhalha  Australia
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Default Mordaunt Short - Carnival Series 2 (1976) Crossover and Tweeter Help Needed!

Hi all,

I am looking for some help and advice on these speakers. They are "working" and I'm confident the main drivers are in good shape but the sound is quite dull, especially from older music / vinyl that doesn't have that crisp electonically-enhanced high end. They also seem to need a lot of power to drive them - possibly to push the tweeters to produce sound and thus overcooking the rest. So I feel the crossovers and tweeters may need some attention - see attached images...

Crossover:

Considering this is a 43-year old circuit, I presume it's worth going ahead and replacing the 2 caps and 1 resistor? There is no visible damage to the caps... But what should I replace with (let's say total budget under $40 AUD)?

Yellow / Violet / GreenCap
4.7 uF 2% (min:4.61, max:4.79 uF) 500V
Replace with? ECWF2W475JA | Panasonic | Polypropylene Film Capacitors | RS

Black Cap

10uF 50V
Replace with? Soundlabs Group 10uF 50V Mundorf Bipolar Audio Cap

Resistor - Appears to be 6R8 - Replace with ???

Tweeter:

Not sure if this is the original unit. It looks pretty well made, and is mounted on a solid basket. but has no markings other than "8 Ohm" stamped on the outside cone. I can't find any pics online of any examples of this marking (or the crossovers) online!?!?!

The units are pretty dusty / crusty and when I tap them, they give off a bit of a crackly sound, like they are dried out. Should these be replaced or can they potentially be cleaned / restored / moisturised? I am not familiar with tweeter restoration at all!


Thanks in advance,

lhalha
Attached Images
File Type: jpg IMG_5669.jpg (1,012.5 KB, 93 views)
File Type: jpg IMG_5668.jpg (618.5 KB, 94 views)
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Old 9th November 2019, 12:24 AM   #2
lhalha is offline lhalha  Australia
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Another pic attached - they seem to be getting rotated when they are uploaded for some reason


IMG_5670.jpg
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Old 9th November 2019, 12:54 AM   #3
Galu is offline Galu  Scotland
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The tweeters look original (see attachment).

The only crossover component in urgent need of replacement is the 10uF ELCAP NP electrolytic - these do not age well! Replace with a good quality electrolytic.
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File Type: jpg Carnival Series 2.jpg (25.9 KB, 108 views)
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Old 9th November 2019, 01:09 AM   #4
Galu is offline Galu  Scotland
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You could try contacting Lockwood Audio regarding the availability of replacement tweeters: Lockwood Audio

Quote:
Lockwood Audio have all remaining spares for 20th Century Mordaunt-Short made before the brand was acquired by Audio Partnership Plc.
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Old 9th November 2019, 01:32 AM   #5
Galu is offline Galu  Scotland
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Quote:
Originally Posted by lhalha View Post
the sound is quite dull, especially from older music / vinyl
Be aware that British speakers from the 70s can be expected to sound on the 'warm' side.

Don't expect heaps of midrange presence and sparkling treble, even after upgrading the crossover capacitors. P.S. I can see no need to replace the resistor.
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Old 9th November 2019, 02:04 AM   #6
lhalha is offline lhalha  Australia
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Quote:
Originally Posted by Galu View Post
The tweeters look original (see attachment).

The only crossover component in urgent need of replacement is the 10uF ELCAP NP electrolytic - these do not age well! Replace with a good quality electrolytic.

Thanks Galu! Would this be a suitable replacement? I understand I can go higher with the voltage rating, but could I go lower?



https://au.element14.com/ampohm-woun...ilm-capacitors
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Old 9th November 2019, 02:33 AM   #7
rayma is online now rayma  United States
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Quote:
Originally Posted by lhalha View Post
I can go higher with the voltage rating, but could I go lower?
A 100VDC rating would be more than enough. Many would use 50VDC.
The 630V cap would be physically rather large, also.
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Old 9th November 2019, 02:52 AM   #8
lhalha is offline lhalha  Australia
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Quote:
Originally Posted by rayma View Post
A 100VDC rating would be more than enough. Many would use 50VDC.
The 630V cap would be physically rather large, also.

Oops - thanks mate, was getting my values mixed up. I will stick with this one that I can buy locally: Soundlabs Group 10uF 50V Mundorf Bipolar Audio Cap


The 500V one is the other cap that's there at the moment - I put Yellow / Violet / Green into this site and it gave me:


4.7 uF 2% (min:4.61, max:4.79 uF) 500V


Maybe the 500V is a red herring, or do those colours specifically denote 500V?



I think what you are saying is, I can replace with anything of the same capacitance value, but > 50VDC and no need to go over 100 VDC.


Should I aim for any specific capacitor type? I'm not sure what type this original multi-coloured part is.
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Old 9th November 2019, 03:24 AM   #9
picowallspeaker is offline picowallspeaker  Italy
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For tweeters it's better to stay with 250 V because of the Dv/Dt rating.
Dunno of any color code for modern film caps!
5% tolerance is ok ( J marking ? )
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Old 9th November 2019, 03:48 AM   #10
Max Headroom is offline Max Headroom  Australia
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Location: West Australia, near to the beach, natural ambient sounds mostly.
Quote:
Originally Posted by lhalha View Post
Hi all,

I am looking for some help and advice on these speakers. They are "working" and I'm confident the main drivers are in good shape but the sound is quite dull, especially from older music / vinyl that doesn't have that crisp electonically-enhanced high end. They also seem to need a lot of power to drive them - possibly to push the tweeters to produce sound and thus overcooking the rest. So I feel the crossovers and tweeters may need some attention - see attached images...

The (tweeter) units are pretty dusty / crusty and when I tap them, they give off a bit of a crackly sound, like they are dried out. Should these be replaced or can they potentially be cleaned / restored / moisturised? I am not familiar with tweeter restoration at all!


Thanks in advance,

lhalha
lhalha, the tweeters need electrical checking with an ohm meter (DMM), and mechanical checking by gently pushing on the cone (two fingers) and listening/feeling for any scraping which means tweeter replacement is required.
Jaycar have suitable 10uF 100V Electrolytic Crossover Capacitor to replace the original ELCAP electros.
The Polycarbonate cap could be replaced with a modern polypropylene perhaps...Jaycar have these too.

These speakers were never bright or lively but with capacitors type and value selection you may be able to brighten them somewhat.


Dan.


Edit: 50V rating is plenty for these speakers.
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