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bencat

Help and suggestions needed

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Super Wammer

Okay I have now committed myself to a change in build in time for Kegworth (Tony this is all your fault for making the suggestion which wormed its way in to my head) .

I have a pair of 1973/4 original KEF 103 reference speakers which are two way units with a T52 SP1049 Tweeters and B200 SP1039 bass units . I loved these from when I bought them after hearing a pair at a Bake Off at Geoff,s (Oldius) . Then after my first visit to Kegworth I was exposed to some active mainly homemade designs which had a speed of delivery and sound that i found very addictive .

I decided that I would like to try it out and using a MiniDSP 24HD unit as active crossover and DAC and Pre I converted a pair of old Monitor Audio units which i bought really cheap . This went well and despite a few blind alleys and finding out I had no idea what a full sweep with REW was telling me I completed the job and ended up with a very noce sounding pair of speakers.

Next job was to be brave and convert the KEF 103 units to active . This proved a little more complex but again not that hard and the final result was all that I wanted it to be .Especially when I upgraded the MiniDSP to Dirac Live V1.0 . Even tones excellent controlled bass and that marvelous speed which I loved from the start. This year I was going to bring them and let others have a listen after the last spectacular failure at the Wam Show 2019 .

And so it should have stayed . Then I blew up not one but two tweeters with stupidity and clumsy use of a volume control. So I needed replacement drivers which were not easy to source and in the end I bought a second pair with good drivers . When I mentioned that I had bought them Tony suggested putting one on top of the other and disconecting the treble units of the bottom pair and using the bass only to make a large 2.5 speaker. Sadly the cabinets were badly damaged when delivered but the drive units were all intact so I went with my original idea and used the T52 units as replacements and kept the B200 for possible future use as spares.

Sadly the idea was already out the box and had wormed in to my head and one night while just a little the worse for Wine and Whisky I saw a very good pair available in Glasgow but only for collection . One cheeky bid later and they were mine . Holidays proved to be a pain so I went and collected them today from an AOS member and they are an excellent pair in very good condition.

Now the job is on for me to create a large floor standing speaker with the two bass units in series (I think) so that they can be wired as both full playing units. I then use the MiniDSP as before to create an active crossover at 3000 khz for the treble units and the two bass to as low as they will go.

Suggestions and help I would ask is that this design has the feature that the metal front panel can be mounted with the Treble above or below the bass unit or even at the side of the bass unit . My instinct is to have the top speaker as normal with treble unit above the bass unit and the bottom speaker with the bass unit at the top as close upper bass unit as possible with the disconnected treble unit at the very bottom . Does this make sense I have added a picture of a pair to assist. It would also be possible to mount the treble unit in the middle of the two bass units by making both fronts with the treble under the bass . Mission used to do this but not convinced it is any better.

I would love to be able to lots of experiments with driver positioning but the way the front panel is kept in place means it is more difficult to switch when you un screw it as the captive nut is spike fixed and falls out very quickly after too many changes. So I want to try and make my decision and then stick to it so that I can get the fronts placed as few times as possible.

Appreciate and advice and suggestions . I am not going to fix the two units together solidly as they are too heavy for a solo lift and too unwieldly to move about. Will use blu tack between the speakers to fix them which should be good enough . I plan to make a couple of Granite Plinths with spikes to stand the speakers on and bring the trebel unit up just a little closer to ear height .

IMAG0200.jpg

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Super Wammer

Andrew, have you considered making them 3 way, and using one of the B200 for mid duties?

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Super Wammer
4 minutes ago, greybeard said:

Andrew, have you considered making them 3 way, and using one of the B200 for mid duties?

Hi Colin , yes and because the Minidsp is only four out it needs another unit to cover three ways . If I had to go that route I would need to buy another DSP unit which I am not really looking to do at this time .

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Super Wammer

Y

3 minutes ago, bencat said:

Hi Colin , yes and because the Minidsp is only four out it needs another unit to cover three ways . If I had to go that route I would need to buy another DSP unit which I am not really looking to do at this time .

you could try it out using the pair with the crossover still in, and send just the mids and above to it, and then send the bass say sub 300hz to the active B200, just to give you an idea what they may sound like as a 3 way.

  • Upvote 1

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Moderator

Hi Andrew

My apologies for planting the idea :D

If you stick with the 2-way configuration, then running the two B200's in parallel would be my preferred choice, as long as the amp can handle the lower impedance (half of the nominal impedance of one driver). Colin's suggestion is a good one - effectively treating the second cabs as subs and having the upper B200 do mid duties only. If they sound good that way (with passive crossovers still in place to separate mid from treble) then you could consider adding a miniDSP 2x4 (not the HD) to split off one of the pairs of outputs from the DDRC, which is how I am doing my 3-way right now. I picked mine up used for not a lot.

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Super Wammer

I know what each of you are saying but I want to keep this all as a full active design and for my own limited ability the two way with the B200,s in parallel is what I am going to stick to . This is also because I only have two power amplifiers and do not want to bring a third.

I have not much time to complete the cosmetic and physical work on the speakers and given how bad I am at this side it takes me much longer to complete and causes me untold nerves . So right now I have made the decision to go with the simplest I can and see were that leaves me. After the Wam show and with no deadline I might well consider further work but just not now .

Do either of you think that the positioning of the bass units will make any difference ?

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Posted (edited)

I can understand that Andrew.

Given that you will be using them for mids as well, you would be best keeping the lower B200 as high as possible.

Edited by Tony_J
Spelpung

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Super Wammer
Posted (edited)
7 hours ago, Tony_J said:

I can understand that Andrew.

Given that you will be using them for mids as well, you would be best keeping the lower B200 as high as possible.

Ditto :^

Edited by Tony_J

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Posted (edited)

I make no claim to any speaker building capabilities but I would be tempted to stack the second speaker upside down on top of the first and disconnect one of the tweeters. You could even try some time alignment of the mid bass units by angling the top speaker down a little using a wedge at the back between the two cabinets.

Alternatively, what about stacking by lying each on it’s side, that would actually look really good and work with the asymmetrical front (the other pair would be a mirror image)

Edited by lostwin
Extra bit

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