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What idiot decided to cut a hole in these?

 
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audiolabtower
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Joined: 06 Jan 2009
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PostPosted: Fri May 25, 2018 8:32 pm    Post subject: What idiot decided to cut a hole in these? Reply with quote

https://www.ebay.co.uk/itm/kef-floor-standing-speakers-model-105-and-full-technics-music-system/132626012320?hash=item1ee12058a0:g:vp0AAOSwlgNa~KOF

eBay item number:132626012320
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SaSi
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Joined: 24 Aug 2008
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PostPosted: Sat May 26, 2018 5:24 pm    Post subject: Reply with quote

Oh my!
I bet the guy is also proud of what they did.
I ran a simulation on WinISD just to see how the response would change by a (guesswork) 5cm port 10cm long.
It would create a 1-1.5dB bump at about 60Hz and drop the -3dB frequency by 4-5 Hertz.
Doesn't sound bad at first glance.
But cone excursion would be uncontrollable below 20Hz (bad if you are listening to vinyl) and group delay will be slightly affected.

I wouldn't mind experimenting on this avenue with this driver on a test enclosure but ruining a classic loudspeaker is a big shame.

I laughed at the claim "well maintained". Never seen so many scratches on CD players, amplifiers and such.
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audiolabtower
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PostPosted: Sat May 26, 2018 7:08 pm    Post subject: Reply with quote

Wink
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audiolabtower
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PostPosted: Sun May 27, 2018 1:30 pm    Post subject: Reply with quote

I did wonder if they left the series cap in the bass circuit too!
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speakerguru
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Joined: 18 Nov 2005
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PostPosted: Mon May 28, 2018 9:03 am    Post subject: Reply with quote

SaSi wrote:
But cone excursion would be uncontrollable below 20Hz (bad if you are listening to vinyl) and group delay will be slightly affected.

Indeed, it could be a problem with warped records and no rumble filter. However, a vented system can in some circumstances recover from LF overdrive more quickly than a sealed box. If mechanical rectification, sometimes called "float" has occured, the cone can take ages to return to its central position in a well sealed box with little leakage.
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