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New member - major help needed with Concerto's

 
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Hodgie
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Joined: 02 Jan 2011
Posts: 4
Location: Sydney, Australia

PostPosted: Mon Jan 03, 2011 10:41 am    Post subject: New member - major help needed with Concerto's Reply with quote

Hi all,
I'm a new KEF convert, having picked up a near mint pair of Concerto's for $50 AUS (near enough to 35 GBP I think).
I am building a minor collection of vintage hi fi, but I really am a rank amateur re any of the technical stuff, and I have 'fluked' a lot of my acquisitions.
Apologies in advance for both the long and potentially idiotic post - I have a number of questions I'm hoping for advice on. (BTW - if each question should be posted separately, just let me know.)
So here goes:
1) Advice from other web sources seems to recommend replacing the caps in the SP1004/dn12 cross-overs as a matter of course (30+ year old electrolytics) Is this true, and if yes, some advice on reasonably priced caps to suit?

2) As a true novice, I can't make sense of the original cap ratings vs new replacements - ie the current caps show 5MFD (x2), 7MFD, 30MFD, and 80 MFD, all at 50v, but I can't find current replacements listed in the same way. IF I need to replace them, what cap values do I need to get?

3) Stands - yes or no? The Concerto's currently sit on a concrete floor that is covered with vinyl (no, not LPs, except on one of my lazier listening days...) - vinyl/linoleum approx. 2.5 millimetres thick (not sure what this is in imperial). Room is approx. 6 metres/18 feet square, with speakers set in corners of one end with slight toe-in. Room has lots of glass (almost 2 walls), but windows are covered with heavy curtains.

4) I'm currently using the Sansui G-5000 rec/amp to drive these (Thorens TD-126 and Marantz CD-45 as sources) - Am I at risk of driving these too hard, and would my Rogers HG-88 be a suitable amp?

5) Finally (...for now...) - how can I tell exactly when my speakers were manufactured? They each have a serial number 5978 and 5981, but I have no way of knowing if this is a KEF number, or if these speakers were assembled locally (NB. IMHO, they don't look like kits, but I have no real reference points). I have approached KEF direct, but don't expect to hear anything until further into the new year.
Thanks for your patience with a newbie - I did try to read as many existing posts as possible re the caps issue to see if I could get an answer without cretaing a new thread.

Many thanks,
Hodgie
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Thorens TD-160B MkII Denon AVR-2105 Denon DVD-1910 Accusound ES-60 speakers Thorens TD-126 MkIII Sansui G-5000 rec/amp Marantz CD-45 KEF Concerto speakers Rogers HG-88 amp Goodmans Axiom 201's Mission 760i's, Dual CS-505 t/t Technics SL-3300 t/t
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ColinR
Über Contributor 1000+


Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Mon Jan 03, 2011 2:26 pm    Post subject: Reply with quote

As Speakerbits in Melbourne have gone "upmarket" annoy Jerry at www.falconacoustics.co.uk Smile .

Start with components like these http://www.cricklewoodelectronics.com/Cricklewood/home.php?cat=139 then spend more money if your ears feel the need.

I suspect Australia will have a ~£18 allowance like the UK where you can import items free of tax and duty, look for it on your Customs website.

Concertos will benefit from being raised, I suggest four cinder blocks covered with a bit of cloth to improve the asthetics and experiment with the height with house bricks, books, telephone directories, etc.

First approximation with Concertos would to have the tops level with the top of your head in your listening position.

You'll have to remove a bass drive and read the 1972(?) date code, serial numbers aren't much use for dating.

Bigger amplifers with bigger psus are less likely to kill an older speaker (tweeter) than smaller ones.
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audiolabtower
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Joined: 06 Jan 2009
Posts: 544

PostPosted: Mon Jan 03, 2011 2:40 pm    Post subject: Reply with quote

It is probable after all these years the caps will have drifted, are they dull in the treble or sucked out in the midrange?

Good advice about cricklewood, caps in parallel add up so if they don't do a 7uF connect a 6 and a 1 in parallel.

You could go for solid caps like cheaper polyesters or polyprops if found locally easily... but they have less losses than the original reversible electrolytics so usually you put resistors say 1/2 ohm in series with the midrange and 1 ohm in series with the tweeter 10 or 7 watt to compensate and bring the bass back to balance subjectively.
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Hodgie
Introductory Contributor


Joined: 02 Jan 2011
Posts: 4
Location: Sydney, Australia

PostPosted: Tue Jan 04, 2011 8:29 am    Post subject: Thanks and clarification on cap values Reply with quote

Thanks for your great replies.

Can I also get some clarification re the listed values of current caps vs what is printed on the existing caps.

For example, the Cricklewood site lists some caps with a value of 30uF.
Is this the same as the 30 MFD that is shown on the original caps?

In other words, is a new cap with a value of 'x' uF the same as an old cap of 'x' MFD?

ColinR - also just to confirm, my Sansui G-5000 is only rated at 45w RMS per channel, so you don't think it will be harmful to the tweeters (assuming I don't do anything stupid with the volume)?

Thanks again,
Hodgie
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Thorens TD-160B MkII Denon AVR-2105 Denon DVD-1910 Accusound ES-60 speakers Thorens TD-126 MkIII Sansui G-5000 rec/amp Marantz CD-45 KEF Concerto speakers Rogers HG-88 amp Goodmans Axiom 201's Mission 760i's, Dual CS-505 t/t Technics SL-3300 t/t
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speakerguru
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Joined: 18 Nov 2005
Posts: 958
Location: Green Hut, Tovil

PostPosted: Tue Jan 04, 2011 9:29 am    Post subject: Re: Thanks and clarification on cap values Reply with quote

Hodgie wrote:
In other words, is a new cap with a value of 'x' uF the same as an old cap of 'x' MFD?


Yes. In the early days of electronics when printing a greek mu (µ) onto a component would have been difficult, it was quite common to use "M" or even "m" instead of µ. Later with lower impedance transistor circuits, when 1000µF/1mF (milliFarad) became more common, the practice stopped.

BTW, I had to cut and paste from MS Word in order to get a "µ" into this post Laughing
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Hodgie
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Joined: 02 Jan 2011
Posts: 4
Location: Sydney, Australia

PostPosted: Fri Jan 07, 2011 10:24 am    Post subject: More info on Caps for Concerto's Reply with quote

Thanks again to all for replies, and the education on mF/MFD/uF etc.

Another question - if I can get the right value in uF/MFD, does it matter what the voltage rating is?

There seems to be plenty of caps available with the right uF, but they seem to be much higher voltage rating than the originals, which all show 50v on them.

Does the voltage have an impact on performance or long-term durability?

Thanks,
Hodgie
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Thorens TD-160B MkII Denon AVR-2105 Denon DVD-1910 Accusound ES-60 speakers Thorens TD-126 MkIII Sansui G-5000 rec/amp Marantz CD-45 KEF Concerto speakers Rogers HG-88 amp Goodmans Axiom 201's Mission 760i's, Dual CS-505 t/t Technics SL-3300 t/t
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audiolabtower
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PostPosted: Fri Jan 07, 2011 12:23 pm    Post subject: Reply with quote

higher voltage rating? excellent! less stress, maybe even better long term reliability.
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Hodgie
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Joined: 02 Jan 2011
Posts: 4
Location: Sydney, Australia

PostPosted: Sat Jan 08, 2011 6:46 am    Post subject: Thanks ....getting there slowly! Reply with quote

audiolabtower wrote:
higher voltage rating? excellent! less stress, maybe even better long term reliability.


Thanks audiolabtower - I'm getting slowly towards all the info I think I need.

I suspect I will draw some more responses, but I am thinking strongly about replacing with electrolytics, due to both price and the physical size of the equivalent poly types, which appear to be huge by comparison and create a concern that I won't be able to fit them without risk to the board.

I have decided to find some throw-away speakers with cross-overs that that I can practice my almost non-existent soldering skills on first.

Cheers,
Hodgie
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Thorens TD-160B MkII Denon AVR-2105 Denon DVD-1910 Accusound ES-60 speakers Thorens TD-126 MkIII Sansui G-5000 rec/amp Marantz CD-45 KEF Concerto speakers Rogers HG-88 amp Goodmans Axiom 201's Mission 760i's, Dual CS-505 t/t Technics SL-3300 t/t
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