Dear All,
I have recently purchased a pair of kef Concerto, I know they are ok but lack detail. The reason I bought them is to extract the units from the cabinets and make, with new crossovers a pair of descent speakers akin to Cambridge R50 or similar. I am struggling to find any plans for a decent build. I have some woodwork skills and a bench saw and so can make most things. The crossovers are apparently easy to obtain from Falcon, but it is the use of a super tweeter and smooth out the bass etc that is my main concern. I also have a pair of dual concentric Goodman's 15" that I could utilise in a design akin to the Kef 105 if that would make more sense. That is to say use the Goodman's as a pure Bass unit isolated from the mid and treble in separate pods.
Comments appreciated and thank you in advance.
Ray
I have recently purchased a pair of kef Concerto, I know they are ok but lack detail. The reason I bought them is to extract the units from the cabinets and make, with new crossovers a pair of descent speakers akin to Cambridge R50 or similar. I am struggling to find any plans for a decent build. I have some woodwork skills and a bench saw and so can make most things. The crossovers are apparently easy to obtain from Falcon, but it is the use of a super tweeter and smooth out the bass etc that is my main concern. I also have a pair of dual concentric Goodman's 15" that I could utilise in a design akin to the Kef 105 if that would make more sense. That is to say use the Goodman's as a pure Bass unit isolated from the mid and treble in separate pods.
Comments appreciated and thank you in advance.
Ray
Moved to Multi-WayThe drivers in the KEF are from 40-50 year ago. Driver design and construction has improved noticeably since this time plus the drivers are likely to be out of spec due to the suspension and other parts ageing. It makes little sense today to invest significant time, effort and money building some cabinets for such drivers unless the point of the exercise is retro. The drivers were widely used and if in reasonable condition are likely to have value as replacement drivers for old speakers. They drivers are actually being manufactured again and sold by Falcon. In your position, if in decent condition, I would consider selling them at 25-50% of the new Falcon price or whatever they tend to go for on ebay and buying some better modern drivers with the money.
If you want to build a retro transmission line like the R50 then there were one or two plans for similar speakers in magazines from the time. Falcon sell the Coles supertweeter new if obtaining one was your concern. If using a supertweeter was your concern then pretty much any modern tweeter won't need to be used with a supertweeter but that will mean using an appropriate crossover. Transmission line design has evolved a bit since this time and if it is the transmission line you want more than the retro then it may be beneficial to look at a few modern designs.
I suspect I haven't wholly grasped what you are seeking to do in terms cost, effort and the desirability of old drivers and designs versus modern ones with a higher technical performance.
If you want to build a retro transmission line like the R50 then there were one or two plans for similar speakers in magazines from the time. Falcon sell the Coles supertweeter new if obtaining one was your concern. If using a supertweeter was your concern then pretty much any modern tweeter won't need to be used with a supertweeter but that will mean using an appropriate crossover. Transmission line design has evolved a bit since this time and if it is the transmission line you want more than the retro then it may be beneficial to look at a few modern designs.
I suspect I haven't wholly grasped what you are seeking to do in terms cost, effort and the desirability of old drivers and designs versus modern ones with a higher technical performance.
The Concerto drivers are capable of sounding quite good even by todays standards; KEF's shockingly poor crossovers made of mess of their capabilities. However there are issues with the choice of original crossover frequencies. The B139 is not good up high and needs to be crossed much lower than 400Hz. I guess that frequency was chosen by KEF to keep an acceptable size and price limit on the crossovers. Much better to cross at ~250 or even 200 and the B110 is quite capable of going that low. The next problem is the B110 doesn't work that well up high and should be crossed about 2.5kHz, but that's a problem for the T27 which is a tad too fragile to cross so low. One option is to replace the tweeter to something that can be crossed lower (I've successfully used a relatively inexpensive PAE
BC25SG18-04 crossed at 2.5k), the other is just to live with the sound of the B110 crossed higher. The B110 also needs a filter to shape its response. If you have the Concerto drivers and they in good nick then you can get excellent results for not much money. The B139 will work well in a 60lt reflex cabinet. I wouldn't bother with the complexity of a TL. Here's the crossover I ended up with:
BC25SG18-04 crossed at 2.5k), the other is just to live with the sound of the B110 crossed higher. The B110 also needs a filter to shape its response. If you have the Concerto drivers and they in good nick then you can get excellent results for not much money. The B139 will work well in a 60lt reflex cabinet. I wouldn't bother with the complexity of a TL. Here's the crossover I ended up with: