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KEF Constructor Series - Long time started, time to finish!

 
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mullmuzzler
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Joined: 20 Sep 2005
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PostPosted: Tue Sep 20, 2005 7:00 pm    Post subject: KEF Constructor Series - Long time started, time to finish! Reply with quote

Hello!

I'm glad that I ran into this forum on hifiloudspeakers.info. I have my dad's DIY cabinets with KEF B110 and T27 units, but unfortunately, I don't have crossovers. The boxes were designed by my uncle and my father in the 80s for active amplifying, therefore the bigger boxes (rear part of the cabinet). Amplifiers are in *endless stand-by stage*, so, i need passive crossovers to complete the set so I can use them at home. I've found falcon-acoustics.co.uk sell crossovers for KEF, but I'm not sure what kit should I order... There is CS1 kit, and CS1A kit. Besides this, there is an option to buy the same kit, but with polyester capacitors.

I am new to this and everything sounds realy confusing... Could somebody help me out and point me in right direction, please?

Here are pictures of my speakers:










Thank you in advance,



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ColinR
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PostPosted: Tue Sep 20, 2005 10:16 pm    Post subject: Reply with quote

Remove a bass/mid unit and see which SP number is on the back or side of the magnet. 1057B's CS1, 1003A's Falcon 23aB and I've an alternative KEF (different solution to the target function) SP1057/T27 crossover design if you're into diy.
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mullmuzzler
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PostPosted: Wed Sep 21, 2005 1:19 am    Post subject: Reply with quote

I did it. On the bass/mid unit says:

B110B SP 1057

and on the treble:

T27A SP 1032.


What kit do I need to order from Falcon?


Could you send me your design, ColinR?



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ColinR
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PostPosted: Wed Sep 21, 2005 11:04 am    Post subject: Reply with quote

Get a CS1/PE.

I need your email address to send a .jpg.

If you're considering building the above, why not got "the whole hog" and use Steve Bell's Ref 101 schematic

http://www.hifiloudspeakers.info/Anatomy/SpeakerSystems/101/Gallery/pages/09R101.htm

Use a Polyswitch to protect the T27, the B110's mechanical stop should tell you if you're being naughty at the bass end Razz .
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mullmuzzler
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PostPosted: Wed Sep 21, 2005 7:22 pm    Post subject: Reply with quote

ColinR, I've sent you PM with my e-mail address.

Also, I have B139B (brand new). Is there some way to make a crossover for the bass unit to be used with my speakers - B110B+T27A x 2 (pictured aabove), and a single bass unit to be used as a sepparate speaker cabinet that I plan to build?



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ColinR
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PostPosted: Wed Sep 21, 2005 11:33 pm    Post subject: Reply with quote

You could steal the bass crossover design from the Cantata design as the B139's already attenuated slightly in it to match the B110B's higher output.

However running the speakers in series will present a 16 Ohm load, so you'll need a good amplifier.

Or steal the CS7 crossover design and insert a T27aB section in place of the T33 - change 3 components?

You could make a Bassett/Coffin transmission line sub - see t-linespeakers.org or dipole like this one http://mitglied.lycos.de/MundU/audio/dipolsubwoofer.htm
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mullmuzzler
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PostPosted: Wed Sep 21, 2005 11:58 pm    Post subject: Reply with quote

The link doesn't work... Crying or Very sad

Any more suggestions, please?



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ColinR
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PostPosted: Thu Sep 22, 2005 12:06 am    Post subject: Reply with quote

This one does... Very Happy

http://www.tech-diy.com/Dipol-Subwoofer.pdf


Night Cool
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SoundAsAnOldEngineer
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PostPosted: Fri Oct 07, 2005 1:14 pm    Post subject: Reply with quote

CS1A was the KEF design for a Ref. 101-like loudspeaker with front mounting B110B. CS1 was equivalent to LS3/5a with rear mounting B110A. I have the crossovers from CS1A, and I could sell you these if you want. However, I think you need to consider the size of the enclosures for the B110B units - they appear to be huge. The crossovers for Ref 101, LS3/5a etc. attenuate all of the audio range except for the bass. This accounts for the poor sensitivity (83 dB/W/m), and the relatively good bass extension. With your larger enclosures, this bass emphasis will be unnecessary, and will give the wrong response and unnecessarily low sensitivity. Also, don't use crossovers for much larger cabinets, because much of the crossover complexity is there to compensate for cabinet diffraction effects, and these depend critically on cabinet dimensions.
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proffski
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PostPosted: Fri Oct 07, 2005 7:29 pm    Post subject: Re: KEF Constructor Series - Long time started, time to fini Reply with quote

Try Falcon Acoustics.

What is the internal volume of the box?
The 'Q' will be wrong if too large.
If I have the time I could run the predicted performance through my simulator programme if you like.
Must admit the boxes look nice, mine are about the same size, but internal volume has been kept down to about 8.5 litres by using lead sheet and bitumen layers. The whole thing is HEAVY!

Good Luck!
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mullmuzzler
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PostPosted: Mon Oct 17, 2005 3:45 pm    Post subject: Reply with quote

They are bigger cause there was a plan to make active preamp for each of them, but that'a another story... I think that the volume is around 8.5 l, as you said... Here are the pics (sorry for the quality, it's my cell phone camera, my digital is not available at the moment)...








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mullmuzzler
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PostPosted: Mon Oct 17, 2005 3:48 pm    Post subject: Re: KEF Constructor Series - Long time started, time to fini Reply with quote

proffski wrote:


What is the internal volume of the box?
The 'Q' will be wrong if too large.


What's 'Q'? Sorry for a probable beginner question... Embarassed
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proffski
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PostPosted: Tue Oct 18, 2005 9:28 pm    Post subject: Re: KEF Constructor Series - Long time started, time to fini Reply with quote

Oh my!
The dreaded Q parameters...
Q - Qtc - Qts.
Have a look here: http://www.geocities.com/kreskovs/Box-Q.html

The ideal Q for most enclosed loudspeaker designs is around 0.7 to 1.0.
I could fill several pages trying to describe as to what Q is.
Call it the "goodness" factor or resonant augmentation.
It is the resultant combination of all the parameters the enclosure will inherit once it is built regarding the characteristics of the driver, the enclosure size and the crossover ultimately.
Amplifier damping, but that can be ignored for the time being.
It is the total sum of the degree to which all the electrical, pneumatic and mechanical interact in the final resonance.
It would be easier to look it up on the internet via Google than let me try and explain it over the net.
Find a good graph showing the various levels of Q in a cabinet where the size is altered and observe the variance of the peak around the fundamental resonance of the system.
Ok, Qts, look at it this way, the resonance and the degree of damping, and the ability of the speaker to reach a particular SPL at the systems resonance.

In pictorial form it is not nearly so formidable!
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