Paul Dimaline
12" round member
It was my old Kef Coda II's that got me into this whole modding game, and after a brief detour with my 62/90, i've just been listening to the result of my labours for the last week or so.
I had previously removed all the wadding from the Kef's and heavily braced the cabinets. I had been trying to make them sound better at lower volumes as we are moving from a detached farmhouse to a semi-detached bungalow in a couple of weeks. This worked in a fashion, they sounded a bit clearer in the midrange, but not particularly "better", and if turned up to much they got in a right muddle. I had decided that I would'nt do any more with them as the drive units, the mid-bass in particular were not up to much.
Then fate played a hand and I took "voluntary redundancy", (not that I had a choice!), and I went self employed. One of the first jobs I did left me with nearly a whole sheet of 15mm MDF, so I decided I had nothing to lose and started to make a new cabinet for the Kef drive units. It's at this time, after removing a sticker, that I found out that the tweeter is made by Audax!
I had an idea for a sand damped cabinet. At the time I thought that I was being particularly novel, not realising that the practice is not that uncommon.
Using what material I had to hand I made a cabinet 410mm high by 390mm deep and 310 wide. with legs at each corner so seperate stands are not needed. The front baffle is double thickness, ie 30mm thick, and on the back panel I fixed another piece of MDF 120mm wide. From that I fitted some 4mm plywood to the front corner, cutting it slightly bigger than required so as when fitted it is bowed. This gives a shape not unlike a Linn Tukan? Katan?, whichever, ie wider at the front than at the back.
I fitted a base of 15mm MDF, and that gave two triangular shaped compartments on either side, and these were then filled with fine kiln dried sand. The top is also 15mm MDF. and when all the joints were sealed this was glued in place.
I glued carpet to the back panel and halfway down the sides, and half filled the cabinet with long hair wool.
As the wires from the crossover would not reach I rubber mounted the crossover to the outside of the back panel and rewired with an ofcut of QED bi-wire cable.
The drivers were connected up and fitted in place with a little silicon sealant.
Externaly, the speakers have a volume of just over 50 litres. They have an internal volume of 22 litres! Over half the volume of the speaker makes up the cabinet walls, and according to the bathroom scales they weigh 49lbs. each. No spikes are fitted, the 44mm square legs sit straight on the carpet.
Due to the quality of the drive units I honestly was'nt expecting to much from them. The whole exersise was to find out if my cabinet ideas would work, and then go on to make an improved version some time in the future.
First record on the LP12 was one of my all time favourites, Sheffield Steel by Joe Cocker. It's a record I know really well both as a test piece and to listen to. After a few moments of stunned silence I went for the volume controll and turned it down a touch.
These are the most dynamic speakers that I have ever had in my house.
They have the warm tonal ballance of the origionals but this was combined with a clarity and an ability to go from quiet to loud that literaly made me jump.
After only a few minutes I had reduced the volume by about 25% over my normal listening level and still they were making me jump out of my skin.
The bass goes down so deep that I was getting some room resonance that I have never had before, (it is a smallish room).
The cartridge distortion that I could hear so clearly at New Audio Frontiers when I had the deck set up, but was not as noticable on my own system is now clearly audiable, (yes, I know a new cartridge is needed!!).
The knuckle test on the cabinet springs no suprises. The sand filled sides are as dead as a very, very dead thing. The 30mm front baffle is as you would expect, and the 15mm undamped top and base make quite a high pitched ring compared to the rest of the panels.
Feeling the panels when playing some loud music was a suprise however. The undamped top and base are virtualy dead, there is a little tingle from the baffle, but the sand damped side panels are the livliest, although we are talking minute vibrations here, the lowest from any speaker I have come across.
It was my hope that the sand would act as a sink for all the cabinet vibrations, but I never dreamed it would work so well. I'll put it down to beginers luck!
My only regret is that I did'nt take more careover the looks and finish. They were only ever meant to be an experiment, but I could live with these quite happily for a while thank you! I still cant believe those cheap and chearfull drive units can sound so good.
Paul.
I had previously removed all the wadding from the Kef's and heavily braced the cabinets. I had been trying to make them sound better at lower volumes as we are moving from a detached farmhouse to a semi-detached bungalow in a couple of weeks. This worked in a fashion, they sounded a bit clearer in the midrange, but not particularly "better", and if turned up to much they got in a right muddle. I had decided that I would'nt do any more with them as the drive units, the mid-bass in particular were not up to much.
Then fate played a hand and I took "voluntary redundancy", (not that I had a choice!), and I went self employed. One of the first jobs I did left me with nearly a whole sheet of 15mm MDF, so I decided I had nothing to lose and started to make a new cabinet for the Kef drive units. It's at this time, after removing a sticker, that I found out that the tweeter is made by Audax!
I had an idea for a sand damped cabinet. At the time I thought that I was being particularly novel, not realising that the practice is not that uncommon.
Using what material I had to hand I made a cabinet 410mm high by 390mm deep and 310 wide. with legs at each corner so seperate stands are not needed. The front baffle is double thickness, ie 30mm thick, and on the back panel I fixed another piece of MDF 120mm wide. From that I fitted some 4mm plywood to the front corner, cutting it slightly bigger than required so as when fitted it is bowed. This gives a shape not unlike a Linn Tukan? Katan?, whichever, ie wider at the front than at the back.
I fitted a base of 15mm MDF, and that gave two triangular shaped compartments on either side, and these were then filled with fine kiln dried sand. The top is also 15mm MDF. and when all the joints were sealed this was glued in place.
I glued carpet to the back panel and halfway down the sides, and half filled the cabinet with long hair wool.
As the wires from the crossover would not reach I rubber mounted the crossover to the outside of the back panel and rewired with an ofcut of QED bi-wire cable.
The drivers were connected up and fitted in place with a little silicon sealant.
Externaly, the speakers have a volume of just over 50 litres. They have an internal volume of 22 litres! Over half the volume of the speaker makes up the cabinet walls, and according to the bathroom scales they weigh 49lbs. each. No spikes are fitted, the 44mm square legs sit straight on the carpet.
Due to the quality of the drive units I honestly was'nt expecting to much from them. The whole exersise was to find out if my cabinet ideas would work, and then go on to make an improved version some time in the future.
First record on the LP12 was one of my all time favourites, Sheffield Steel by Joe Cocker. It's a record I know really well both as a test piece and to listen to. After a few moments of stunned silence I went for the volume controll and turned it down a touch.
These are the most dynamic speakers that I have ever had in my house.
They have the warm tonal ballance of the origionals but this was combined with a clarity and an ability to go from quiet to loud that literaly made me jump.
After only a few minutes I had reduced the volume by about 25% over my normal listening level and still they were making me jump out of my skin.
The bass goes down so deep that I was getting some room resonance that I have never had before, (it is a smallish room).
The cartridge distortion that I could hear so clearly at New Audio Frontiers when I had the deck set up, but was not as noticable on my own system is now clearly audiable, (yes, I know a new cartridge is needed!!).
The knuckle test on the cabinet springs no suprises. The sand filled sides are as dead as a very, very dead thing. The 30mm front baffle is as you would expect, and the 15mm undamped top and base make quite a high pitched ring compared to the rest of the panels.
Feeling the panels when playing some loud music was a suprise however. The undamped top and base are virtualy dead, there is a little tingle from the baffle, but the sand damped side panels are the livliest, although we are talking minute vibrations here, the lowest from any speaker I have come across.
It was my hope that the sand would act as a sink for all the cabinet vibrations, but I never dreamed it would work so well. I'll put it down to beginers luck!
My only regret is that I did'nt take more careover the looks and finish. They were only ever meant to be an experiment, but I could live with these quite happily for a while thank you! I still cant believe those cheap and chearfull drive units can sound so good.
Paul.
