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What should I be expecting from 1970s speakers?

 
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konkord
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PostPosted: Tue Dec 04, 2012 9:37 pm    Post subject: What should I be expecting from 1970s speakers? Reply with quote

I have just purchased some Kef Concord IIIs - I love the large size, the looks, and that they have twin 8" bass drivers: surely they must have some bass! But no. Sadly, to me, they sound like speakers half their size, and a little bit 'boxy', though not unpleasant to listen to. It's just that they look as though they should be so much more. Am I expecting too much?

I have a pair of Tannoy R2s that I am running 'sealed' i.e. with the port bunged up, and yet they sound so much bigger and more impressive than the Kefs despite smaller size and drivers.

The Concords are really rather nice cosmetically, and it would seem sacrilegious to rip them apart. However, without improving the sound, they're not much use to me. Assuming they're not in some way damaged, and I have no reason to think that yet, is there anything I can do to make them sound a bit more like they look, preferably without having to go active? I'd be quite willing to experiment with replacement drivers and/or crossovers if it would help, as I really do love them (even if only for their looks at this point!).

Thanks
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audiolabtower
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PostPosted: Wed Dec 05, 2012 12:22 am    Post subject: Reply with quote

Hi, these were "value" speakers in their day, using cloth sleeves rather than veneer, and paper drive units rather than the more expensive kef drivers. They were not that enthusiastically reviewed in their day if my memory is correct. If the lack of bass is that bad maybe something in the crossover has drifted - they are after all 33 years old.
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konkord
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PostPosted: Wed Dec 05, 2012 8:51 am    Post subject: Reply with quote

audiolabtower wrote:
Hi, these were "value" speakers in their day, using cloth sleeves rather than veneer, and paper drive units rather than the more expensive kef drivers. They were not that enthusiastically reviewed in their day if my memory is correct. If the lack of bass is that bad maybe something in the crossover has drifted - they are after all 33 years old.

OK, so it'll be no great loss if I do some major surgery on them. (I know that destroying 'perfectly good' speakers is frowned upon in these forums).

One thought occurs: Kef didn't use foam surrounds on their drivers did they?

Interesting what you say about the cloth sleeves rather than veneer. To my eyes the large size, rounded corners and cloth sleeves look so much more interesting and sophisticated than a veneered wooden box. In 1978 when I was about 15, these speakers would most definitely have been objects of desire for me. I'd imagine them in a large room with a white carpet and an XJS or a Jensen on the drive outside. In fact that 1970s styling, with rounded corners, square top and overall cloth sleeve has become rather fashionable again e.g. http://www.guardian.co.uk/technology/2010/oct/10/arcam-rcube-hi-fi-ipod
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audiolabtower
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PostPosted: Wed Dec 05, 2012 5:56 pm    Post subject: Reply with quote

Hi, foam surrounds were used on the coupled cavity speakers, mostly Reference series to get the lowest driver resonance frequency with a low mass cone. I doubt very much your Concords were foam surround but am not sure and could be wrong. If you want to stick with them I would look at the reversible electrolytics in the crossovers first, maybe they have drifted? The two 8in units should be outputting together in the bass, so you could try a blast of thumping bass and see if they move together. The lower one should roll off in the upper bass to leave the one nearest the tweeter to crossover on its own to the high frequencies, if my memory is correct.
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konkord
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PostPosted: Thu Dec 06, 2012 1:30 am    Post subject: Reply with quote

Maybe I've misjudged them a bit. Can I include images in this forum?

I do have a measurement microphone, and measuring the response at each driver's centre just off the grille cloth using REW shows that they're just about as described in terms of bass response i.e. 3dB-ish down at about 60 Hz, and 6dB down at 40Hz, but with a bit of a dip at about 300 Hz/ bulge at 120Hz (middle driver). Coming the other way, the tweeter appears to be down 6dB at 2.8 kHz. Does that sound about right for the crossover frequency?

In my listening room, the response at about 1m reflects those measurements, and is noticeably lumpier than some other speakers I've measured in the same position. But I am hearing the bass! Maybe I'll not take them to bits just yet.

However, I may just do as you suggest and replace the NP electrolytics as a matter of course - I can run to that expense.
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audiolabtower
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PostPosted: Thu Dec 06, 2012 11:45 am    Post subject: Reply with quote

Yes, 3 kHz crossover is about right, maybe seeing a phase dip due to mic position or crossover or mechanical driver drift?

By accident I have a review on same pages as another review I wanted to keep. This shows a flat bass from 70 to 300 Hz, a broad mid-range dip of ~3 dB to 4 kHz, then high treble back to bass level, this at 1m anechoic (no crossover dip). Room averaged it was flatter with a small peak at 150 Hz and above 10 kHz.
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