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Multi-Way Conventional loudspeakers with crossovers

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Old 2nd January 2013, 11:39 AM   #31
DeonC is offline DeonC  South Africa
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Hi guys

This week I finally got my pair of KEF Concertos. It was quite a good deal for me. I got the Concertos, a Lenco L-75 turntable, a pair of Seas H-087 tweeters and a trio of GE A1-501 16" tone-arms, all for the grand total of $135. I'm happy. The one T27 tweeter is not working, but the previous owner got a quote of $35 to fix it. I think I'm going to go down that route.

Ok, so I just got the speakers, and I am not even using them yet, but the DIY-and-tweaking bug has already bit. I have a pair of Leak Sandwich bass drivers, so I thought- why not go four-way. Put the B139 in an aperiodic sealed box, and use the Leak bass driver for low bass, XO at about 120Hz - 150Hz. I'll use the existing front baffle of the Concertos, just add a piece of baffle on the bottom end for the Leak driver, and then build a box around that. Sorta like the Concertos, just taller and with an extra bass driver on the bottom. The Leaks will each go into a sealed 2cu.ft. to 3cu.ft. cabinet. What I want to do is slightly improve on the aspect I suspect will be the weakest, namely the bass. I don't expect the bass to go much deeper, but with better quality and power handling. What do you guys think? Worth the trouble? Note that these speakers will not be keepers. I have a pair of Tannoy 15" dual-concentrics that need new surrounds. When they have been repaired, I'm going to pass the KEFs on to a friend of mine. They suit his types of music well (soft rock, ballads and vocals). I could have fixed the Tannoys for the money I spent on the KEF package deal, but the Lenco turntable called too hard. OTOH, I got such a good deal, if I had to choose again, I'd do it again at the drop of a hat. That all said, what do you guys think of my idea?

Enjoy,
Deon
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Old 2nd January 2013, 04:35 PM   #32
DeonC is offline DeonC  South Africa
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Hi guys

Here are two photos of the old girls. They are on some open-frame stands I got with them. The veneer on both has become very tatty and loose, in fact I got a nasty splinter from the one the other day, so this is also part of the motivation to build new cabs. I did a quick calc, and I'd be able to put the Leaks in sealed cabs of about 75l - 80l. Maybe more if I extend the depth a bit. What do you think?

Deon
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Old 2nd January 2013, 04:57 PM   #33
Gopher is offline Gopher  United Kingdom
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Hi there

Can anyone explain why, in the crossover schematic in Post 4, the B110 midrange is wired in inverse phase to the woofer and tweeter?

Last edited by Gopher; 2nd January 2013 at 04:59 PM.
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Old 4th January 2013, 07:19 PM   #34
DeonC is offline DeonC  South Africa
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Quote:
Originally Posted by Gopher View Post
Hi there

Can anyone explain why, in the crossover schematic in Post 4, the B110 midrange is wired in inverse phase to the woofer and tweeter?
Ok, so since no-one seems to want to answer this one, I'll take a stab at it. Just note that I am not technical. As far as I understand it, it is due to the fact that the 2nd order crossover reverses phase at the crossover point. Therefore the phase of the mid is reversed to compensate. Others may have a better explanation.

Deon
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Old 14th February 2013, 01:41 PM   #35
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Quote:
Originally Posted by DeonC View Post
Hi guys

Here are two photos of the old girls. They are on some open-frame stands I got with them. The veneer on both has become very tatty and loose, in fact I got a nasty splinter from the one the other day, so this is also part of the motivation to build new cabs. I did a quick calc, and I'd be able to put the Leaks in sealed cabs of about 75l - 80l. Maybe more if I extend the depth a bit. What do you think?

Deon
Those Concertos are nice speakers.

Falcon Acoustics do a 35 replacement crossover (No. 5aB) which is claimed to make a significant improvement to them.

Alternatively Dr. Bailey published a DIY transmission line design for them in Wirelesss World in May 1972 which is supposed to sound fantastic.
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Old 14th February 2013, 08:43 PM   #36
gfiandy is offline gfiandy  United Kingdom
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If there not going to be keepers why take them to bits. They will eventually be worth more as original KEF speakers. So why not just recover them in new veneer and replace the electrolytic caps as they will be well out of tolerance by now.

Regards,
Andrew
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