The final configuration of my stacked KEF 103 Reference Speakers

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Bencat57
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The final configuration of my stacked KEF 103 Reference Speakers

Unread post by Bencat57 »

I do not know if the following will be considered strictly DIY but there has been a large amount of work done by me so I will put this here in case anyone is interested .

One of my favorite passive speakers for many years has been the KEF 103 Reference units from the early seventies . This is a medium sized sealed baffle two way with a metal frame it uses B200 Drivers the large magnet version and a T52 Tweeter. Sound is tight bass and very musical and if you are brave and renew (upgrade) the crossover they will hold there own against much of today's mid range speakers.

In 2017 after being at the Wam Show and having a room I became interested in going active . I have very minor technical and practical skills so there was no way I was going to chance destroying my KEF 103 . Instead for the sum of £30 I bought a pair of late eighties Monitor Audio Reference speakers which were a 2 and a half way . Removed the internal passive crossovers and bought a MiniDSP 24 HD unit which allowed me to set crossovers with either digital in and four analogue out . using a UMIK microphone I was able at the start to get music out and using REW add some inroom filters which improved the sound quality . All in all was happy with this and proved to me I could do it .

Gave the Monitor Audio units away and then with trembling hands decided to go all in and convert the KEF 103 . Played them passive once more and very nearly changed my mind as they sounded so nice . Got over that and the a similar thing take out the passive CR but this time I had to add a second set of Speaker Binding posts and wire the drivers directly to them (Monitor Audio were bi wire).
I had also found about a download from MiniDSP that would convert my 24 HD to a DDRC 24 which would include DIRAC Live DSP software , yippee no more REW. So installed the Dirac and used 2 x Quad 405 amplifiers one for each side(Right/Left) . Completed a full Dirac Live session and made the sensible alterations to the filter in line with the sort of house curve I wanted . Results were to say the least spectacular the sound was now better bass , more realistic vocals , and speed . Speed is the thing that active seems to give you over passive designs and once you hear it you get addicted and want it more. By speed I mean how notes stop and start with active this is very fast and sounds more real with passives it can be a little slower and smeared , for me at least active us makes the music more natural and real but i am sure others will not agree.

I suppose this is were things should have stopped as the system was now sounding excellent best it ever had and I just loved it , sadly some of the other DIY gang had other ideas and one suggested that getting a second pair of KEF 103's and stacking them and just wiring the Bass units of the bottom pair in parallel would give me another two and a half way with more bass . Well I found another very nice pair in Glasgow and so started my next step . Leave the bottom tweeters unconnected wire the bass units in run another DIRAC Live session and what do we have . Well much to my surprise we have a bigger sound stage , more and deeper bass and even better speed . This was exceptional just awesome . I should now have reached end game but no the suggestions keep coming.

Now the idea of splitting this in to a true three way which is just not possible with the MiniDSP DDRC 24 and is expensive for the multi channel models . So now I am starting work on using a MiniDSP DDRC 22D unit for Dirac Live . Feeding an XLR digital signal from this at 24/96 in to a Behringer DCX2496 Ultra Pro unit which will then allow me to split the crossover digitally over Low Bass / Mid Bass / Treble and then feed that to an NVA P30 for Low Bass and two (one left / one right) NVA P20 amps for Mid Bass and Treble . I am already using the two NVA P20 amps in the active system which was an improvement on the QUAD 40's . This is my next job and splitting Low Bass to 200hz -350hz (will adjust this by ear) then Mid Bass 200hz-350hz - 3000hz above that through to the treble unit. I know this will sound good and my hope is that if the Mid Bass units are not having to do any Low Bass work then the drive unit will work much more in its best operating parameters and been less stressed and so more linear in output. My hope is that thiswill just lift the sound quality level to above were it is now . Actual work will start next week and I hope to have things working by next weekend .

If this all comes together and sound as good as I think it will then this is the system I will take with me to show at The Wam Show which is now scheduled for September 2021 (no firm date yet) . So if you have bothered to get to the end of this (sorry it is so long) and would like to hear it then will put a link to my room on here when the show is confirmed.

If you have any questions then ask away will do my best to answer as best i can .
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karatestu (Sun Jan 10, 2021 2:32 pm) • savvypaul (Tue Jan 12, 2021 10:27 am)

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by NSNO2021 »

Fascinating reading and thanks. I would love to hear them in action at the WAM show
Mr Modify :lol: Modified Airlink BPS 3110S with LDA DC filter, modified Rega Planar 8, with modified Apheta MC cartridge, Kenwood KD 8030 with AT OC9XSH, LDA MCJ3 phono, modified Schiit Freya plus pre amp,, FW Aleph J mono blocks, Cambridge Audio CXC, Denafrips Pontus 2 DAC, Mano Ultra2 streamer, Cisco switch, Audio Technica ATH 70 cans, Cubix MMXXI & NSNO W48.5 speaker cables

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by Daniel Quinn »

:banana-gotpics: :banana-gotpics: :banana-gotpics: :banana-gotpics:

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by Bencat57 »

Sorry the pictures I have are too large to show and when I reduce them using 7 Zip it says they are unsupported files .

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by antonio66 »

I'm sure you've done a grand job, it would be nice to see pics, someone maybe will come on here who will tell you how it's done

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by Bencat57 »

I have at least made them work but given the number of times I have blown up amplifier (including the last Wam Show when I was forced to use a suitcase system instead) and the treble units I have been through I would never say i have doen a grand job . I would say though that I am very happy with the end result . If anyone can advis how I can add the pictures then it would be appreciated .

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karatestu
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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by karatestu »

Fof advice on posting pics on the forum have a look at these threads in the forum help section.

https://www.hifisubjectivist.org/viewt ... =50967
https://www.hifisubjectivist.org/v ... 9&t=50321

You can also post videos :grin:

https://www.hifisubjectivist.org/view ... 8570
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TheMarlin (Tue Jan 12, 2021 11:43 am)
DIY inspired by Richard "The Doc" Dunn RIP

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by karatestu »

Nice thread and excellent work :dance:

Although I won't be going down the dsp route or room correction I am interested when I read others adventures.

My speaker mid bass (and NVA Cubes) are run full range without any filters before or after the power amps so will share many of the sound attributes you have experienced.

Although my tweeters have a first order filter before them (single capacitor) I have bought some polystyrene caps so I can try putting the high pass filter in the input stage of my nva amplifier boards. This will be half of what is known as a passive line level crossover. As there is a resistor to ground on the input of the amp board all that is required is to solder in the cap in series with the signal.

I am doing it out of curiosity mainly and will mean that there will be no components between the amplifier output and tweeters. If the amp goes DC for any reason then it will be bye bye tweeters :roll: It will, only be worth doing if the sonic gains are large enough.
DIY inspired by Richard "The Doc" Dunn RIP

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by Bencat57 »

Sorry this may well be a duplicate as I posted and saw the post but does not seem to be in the thread . I think this will be two photos of the system which some have asked for .


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savvypaul (Tue Jan 12, 2021 10:27 am)

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Re: The final configuration of my stacked KEF 103 Reference Speakers

Unread post by antonio66 »

I notice you have the tweeters top and bottom, most photos I've seen with this idea have had the tweeters in the middle and the mid/bass top and bottom, did you try it both ways? Look good though

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