Mordaunt Short - Carnival Series 2 (1976) Crossover and Tweeter Help Needed!

[lhalha]

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

 

[lhalha]

Another pic attached - they seem to be getting rotated when they are uploaded for some reason

 

[Galu]

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.

 

[Galu]

You could try contacting Lockwood Audio regarding the availability of replacement tweeters: Lockwood Audio

Lockwood Audio have all remaining spares for 20th Century Mordaunt-Short made before the brand was acquired by Audio Partnership Plc.

 

[Galu]

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.

 

[lhalha]

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-wou...passive-components/capacitors/film-capacitors

 

[rayma]

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.

 

[lhalha]

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.

 

[picowallspeaker]

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 ? )

 

[Max Headroom]

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.

 

[Galu]

Thanks Galu! Would this be a suitable replacement?

The capacitors to which you referred in your original post are adequate for the job.

If you find that the tweeters are truly faulty, then look for suitable paper cone replacements - ones with similar physical dimensions.

Such tweeters are not expensive, so taking a chance on buying a pair to see how they blend in would be worth considering - we're not talking ultimate fidelity with these speakers.

Here's a possibility:

VIS TW 6NG: VISATON cone tweeter at reichelt elektronik

The original tweeters are Peerless units - read about them here:

McIntosh Drivers--Tweeters

 

[AllenB]

Our side of the pond was happy with conservative treble. The concept that any treble that stands out, ie that doesn't balance in, will draw attention to itself and speakers shouldn't do that.

 

[midrange]

VIS TW 6NG: VISATON cone tweeter at reichelt elektronik[/url]

The original tweeters are Peerless units - read about them here:

McIntosh Drivers--Tweeters

Also the Monacor HT-22/8 are surprisingly good cone tweeters. They are round though. I don't know if they are available locally.

 

[Galu]

Tweeter: The units are pretty dusty / crusty and when I tap them, they give off a bit of a crackly sound.

According to the link I supplied, the Peerless tweeter has a very lightweight cone/voice coil assembly and doesn't even have a spider to centre the voice coil.

So, after all these years, it is not surprising that the voice coil should be scraping in the magnetic gap, accounting for the 'crackling' sound you have heard!

 

[rayma]

This was a common problem, even new from the Peerless factory.

 

[lhalha]

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.

So I am off to Jaycar today, as it looks like they have all these parts in stock. Go Aussie!

For the 4.7 uF - they have both these parts (you can see from the URLs - no need to click) with the polypropylene being $12.50 a pop and the electros much cheaper. In my original image, my understanding from the thread responses is that the multi-coloured cap is not an electrolytic type. So would you advise that I drop the $25 on two of the polys, or could I replace that with a modern electro?

Thanks again for all your help!

4.7uF 250V Metallised Polypropylene Crossover Capacitor | Jaycar Electronics

4.7uF 100V Electrolytic Crossover Capacitor | Jaycar Electronics

 

[Galu]

The muti-coloured cap is a plastic film cap. There is probably no great advantage in replacing it at all!

Technically, you would be best to replace like with like, which means going for the polypropylene cap.

Personally, with this speaker, I don't think either of your three options is likely to be audibly superior to the others.

 

[lhalha]

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.

So I am off to Jaycar today, as it looks like they have all these parts in stock. Go Aussie!

For the 4.7 uF - they have both these parts (you can see from the URLs - no need to click) with the polypropylene being $12.50 a pop and the electros much cheaper. In my original image, my understanding from the thread responses is that the multi-coloured cap is not an electrolytic type. So would you advise that I drop the $25 on two of the polys, or could I replace that with a modern electro?

Thanks again for all your help!

4.7uF 250V Metallised Polypropylene Crossover Capacitor | Jaycar Electronics

4.7uF 100V Electrolytic Crossover Capacitor | Jaycar Electronics

 

[AllenB]

The woofer inductor could have a high permeability core. It is a guess without measurements, but with its size it may vary with power in.

 

[lhalha]

Thanks everyone - I have replaced the 10 uF cap and tested the tweeters with a DMM - readings were 1.4 for one and 2.4 for the other. I'm going to research some cheap replacement drivers, following some of the suggestions above. Thanks all