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Kef Q80 & Q90 uni-q

 
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elgee
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Joined: 11 Oct 2013
Posts: 5
Location: Norfolk

PostPosted: Sun Oct 13, 2013 4:11 pm    Post subject: Kef Q80 & Q90 uni-q Reply with quote

Hi. I'm new to this forum but have owned Kef speakers for a number of years now in the form a pair of Q80's. I have also just picked up a pair of Q90's in excellent condition. As I searched for information on the Q90's before I bought them a few questions arose and I wondered whether anybody could shed light on them:

- I wonder why so little is written about these models?

- I see from browsing the forum that a number of members have invested in reference series speakers. I know they have an excellent reputation but are my Q90's anywhere near on a par or, should I save up until I can afford a pair of early reference speakers?

- Finally, and thank you for your patience, I read somewhere that my speakers would benefit from upgrading the crossovers. Do members feel that this would be worthwhile and what would they recommend? (I can solder but wouldn't know what to look for in terms of replacements for internal wiring, make/type of capacitors and any other replacements. Any suggestions would be most welcome.

Thanks.
Les Greenwood Very Happy
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speakerguru
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Joined: 18 Nov 2005
Posts: 958
Location: Green Hut, Tovil

PostPosted: Mon Oct 14, 2013 8:20 am    Post subject: Reply with quote

Welcome to the forum.

Have a look at http://www.hifiloudspeakers.info/Anatomy/KEFDocuments/KEFTopics/KEFTOPICS_Vol_3_No_3.pdf to see the selection and sorting that was done to get the close tolerance Reference Series systems.

Otherwise, in non-reference series, the spread in sensitivity and response ended up around 2 to 3 times bigger.
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elgee
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Joined: 11 Oct 2013
Posts: 5
Location: Norfolk

PostPosted: Tue Oct 15, 2013 2:14 pm    Post subject: Reply with quote

Thank you speakerguru , most interesting reading.

I can see that close matching of units would make a difference to the sound quality in the reference series. Would the new production techniques, testing regimes and materials mentioned in the bulletin, have also improved the consumer models like the Q90, do you think? (I wish I could get my hands on a pair of early 90's reference speakers to make a comparison but sadly, my pension will not stretch to this yet!).

I have read enough elsewhere to realise that there is a lot of misinformation and mythology surrounding various aspects of Hi Fi, including, the supposed compromises made when commercial realities meant that firms needed to 'build to a budget' rather than 'extracting the best irrespective of cost'. So, I'm a little sceptical when I read about vast improvements after spending large sums on say, 'bespoke' speaker cable etc., but it would be good to get the views of an expert like yourself, so...
In your view is there any mileage in upgrading the existing crossovers or, were they always designed and matched to produce the best results from the outset?
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speakerguru
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PostPosted: Wed Oct 16, 2013 7:43 am    Post subject: Reply with quote

I don't think that KEF crossovers can be "upgraded"without access to acoustic measuring equipment, loudspeaker design software, training and a lot of experience. By all means check that everything is working and that electrolytic capacitors have not degraded with age.
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elgee
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Joined: 11 Oct 2013
Posts: 5
Location: Norfolk

PostPosted: Wed Oct 16, 2013 11:35 am    Post subject: Reply with quote

Just as I thought. As you probably gathered from the basic nature of my original question I don't have the equipment or skill but I curious. I had read a 'casual ' comment on another forum, following a member's purchase of Q90's, that they would benefit from a crossover 'upgrade'. I thought at the time that this would be much more complicated than was implied by suggestion.

After checking the capacitors and assuming that they have degraded to some extent given their age, what would you recommend as replacements; possibly better quality? Question
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speakerguru
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Location: Green Hut, Tovil

PostPosted: Wed Oct 16, 2013 9:43 pm    Post subject: Reply with quote

KEF crossovers were designed taking into account the loss factor of reversible electrolytic capacitors. "Low loss" reversible electrolytic capacitors were used in most series positions in the ladder networks, e.g. tweeter sections. In parallel positions (to ground and often with a series resistor) there was low sensitivity in the response due to loss factor, so, regular reversible electrolytic capacitors were used. If you do not want to change the intended response then try to get similar replacements.
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elgee
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Joined: 11 Oct 2013
Posts: 5
Location: Norfolk

PostPosted: Thu Oct 17, 2013 12:10 pm    Post subject: Reply with quote

Thanks you for the help and advice.
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