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Old 20th June 2012, 08:48 PM   #1
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Default Chartwell PM110 Speakers - Crossover Help

Hi I am a complete DIY aoudio novice who needs some help.

I have been given a pair of Chartwell PM110 mk 2 speakers (early 1980's) which have not been used for many years and which I would like to refurbish. I have tried the speakers and they work though bass seems to be some what lacking, I was thinking of attempting a recap but need some help identifying parts. Can anyone tell me if the 5 Rifa brand silver rectangular capacitiors in the below photo are bipolar electrolytic and if so are there modern equivalents available of similar dimenions that would easy to fit on the board? Also the 3 black resistors are covered in white powdery deposit, is this normal with resistors of this type or does it mean they have failed and need repalcing?

Click the image to open in full size.

Sorry if these are dumb questions

Cheers
Rich
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Old 21st June 2012, 05:30 AM   #2
system7 is offline system7  United Kingdom
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No dumb questions here, just dumb answers, IMO!

These Chartwell PM110 MkII were made by swisstone down in Mitcham. I believe Chartwell added their own polypropylene cones to Dalesford chassis.

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The Chartwell PM110 is the smallest in a new series employing the company's own development of polypropylene as a cone material for the main driver. Apart from a claimed reduction in colouration and distortion (see also the Harbeth HL) this increases sensitivity, as does the use of a reflex vented enclosure rather than the usual closed box, and we found the PM11O of above average efficiency despite its relatively small size. The main driver has a PVC termination and a long-throw voice coil to permit reasonable bass radiation without clipping. The Son Audax tweeter operates from 2.5 kHz upwards. The review samples were teak veneered and looked very handsome with the 20mm thick moulded foam grille lending a bit of style, though it has no frame and is held rather loosely by velcro pads. Connections are via 4mm sockets or a DIN male socket in a recessed moulding.
Those boxy capacitors look like MKT polyesters to me, so probably haven't deteriorated badly. The black one IS a non-polar, maybe 7uF, so it looks like a 6.8uF replacement of the same type would be in order. You could use a better polypropylene there with a minor change in response. Wilmslow Audio have a good range: Capacitors

Wilmslow only stock 10W wirewound resistors, which are quite big. But fine as replacements if you find the old ones have drifted. Looks like 3rd order filters with a trap to kill a woofer peak to me. Very BBC/KEF! These speakers were designed to be very uncoloured and smooth and civilised and specified for professional monitor use, but don't expect slamming bass or metallic highs from them. In fact any crossover ageing really shouldn't affect low bass too much since the coils decide that. Always worth unplugging and replugging connectors and fuses to get some fresh metal on the connections, maybe check for dry joints if you are nifty with a soldering iron. These are a minor classic, FWIW. But I would unsentimentally replace any broken drivers with modern equivalents like Morel.
Attached Images
File Type: jpg Chartwell_PM100.JPG (49.8 KB, 99 views)
File Type: jpg Chartwell_PM100_crossover.JPG (15.3 KB, 100 views)
File Type: jpg DALESFORD-Drivers.jpg (161.3 KB, 98 views)
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Good Night, and Good Luck. Best regards from Steve in Portsmouth, UK.

Last edited by system7; 21st June 2012 at 05:42 AM.
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Old 21st June 2012, 07:06 AM   #3
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Is it possible that the rubber surround has hardened slightly? Those WW resistors look corroded, perhaps these have got damp for a significant period of time?My experience of Wilmslow is a little lacklustre. CPC stocks direct replacements for those resistors. As system7 says those caps are likely MKP, and available from plenty of vendors.
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Old 21st June 2012, 08:23 AM   #4
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Many thanks for the all advice. If the thinking is that the MKT Polyester caps won't have deteriorated as quickly as standard electrolytics would have, then I may leave them be and just replace the one 7uF electrolytic on the board with a direct Alcap LL replacement or possibly a film Claritycap. I'll try to scrape the corrosion of those resistors to see if any values are maked on them, unfortunately I don't have any test equipment only a soldering iron which I need to learn how to use.

I'll give them a good run over the weekend to see if they loosen up a bit as they obviously haven't been used for some considerable time. The quick listen I had last night showed reasonable mid's & highs but liitle in the way of bass but like you say they may have been designed that way. Not looking to spend much on these babies I just wanted to keep them out of landfill .

Last edited by Phantom499; 21st June 2012 at 08:28 AM.
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Old 21st June 2012, 08:45 AM   #5
system7 is offline system7  United Kingdom
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System7 shows off his MODEST old Chartwell PM400's....

Click the image to open in full size.

Pretty good actually. Well made.

Hang on to them, Phantom. Nice boxes with loads of potential down the road.

Next you need some test gear and a few components.

Click the image to open in full size.

That multimeter is a 60 Maplin jobbie that can measure capacitance and coil inductance, but a 5 cheapie can measure resistance. It's a great hobby.

Oh I should mention that Chartwell had some issues with PVC suspensions sagging in hot weather. Causes the bass voice coil to rub. You turn them upside down to fix that. LOL.
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Last edited by system7; 21st June 2012 at 08:52 AM.
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Old 21st June 2012, 11:48 AM   #6
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Had the same speakers 10 years ago.They do have that BBC sound.Very sweet if little bright Audax tweeter.They sound soft and slow but very natural and warm.You should replace the
resistors.
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Old 21st June 2012, 12:21 PM   #7
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Steve, your PM400's look in great. I have to agree that the Chartwell cabinets are very well made, far to good for me to scrap. My normal speakers are Audiomaster MLS4's which I bought new in 1980 and like very much, however a few weeks ago I had the chance to purchase some Celestion Ditton 44's cheap and have to say that these are probably even better than the Audiomasters, the Chartwells were thrown in for free when I went to collect the Dittons.

Dufus, thanks for your experiences with Chartwells, I will make sure I change those resistors.

Will keep you posted on my progress as I'm bound to need more advice as I go along.

Cheers
Rich
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Old 8th September 2014, 11:23 AM   #8
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A friend of me want to repair the PM110. An other Solution could be the replace through an currently available model from Spendor, the new A3 - go to
Spendor A3 Loudspeakers (Hi-Fi+ 86) | Hi-Fi+

Who have heard this Spendor model?
What about the crossover network and measure results of the A3 (quality of parts, frequency response etc.).

The actually question is, if one get a sound improvement/sound enhancement in opposite to the PM110.

Best thanks for comments.
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Old 8th September 2014, 05:46 PM   #9
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Those Audax HD 12x9 D25H's can be fizzy sounding. Good quality caps would help control that a little.
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