Please can you help with advice. I have an old pair of Kef Concord 3s, and I would like to know the specs of the B200 SP1069 drivers. These were Kef's budget speakers of the 70's and are not worth a great deal, so I thought they might make an interesting project if I reconfigured the SP1069's (there are 2 in parallel in each speaker) to sit in Isobarik configuration.
I've never thought the Concords to be particularly good and never understood the logic of having two drive units pressurising the same enclosed space. They may be operating at different frequencies (apart from the crossover zones), but they would still apply unwanted back pressures on each other.
I understand that the two SP1069's currently combine to form a 'notional' 8 Ohms impedance, and that this would not change when placed in Isobarik parallel configuration. I also understand from reading about Isobariks, that none of the other speaker parameters will change too much .
I appreciate that the crossover will need adjustment.
Many thanks,
Any advice and/or data on the Sp1069 would be greatly appreciated.
I've never thought the Concords to be particularly good and never understood the logic of having two drive units pressurising the same enclosed space. They may be operating at different frequencies (apart from the crossover zones), but they would still apply unwanted back pressures on each other.
I understand that the two SP1069's currently combine to form a 'notional' 8 Ohms impedance, and that this would not change when placed in Isobarik parallel configuration. I also understand from reading about Isobariks, that none of the other speaker parameters will change too much .
I appreciate that the crossover will need adjustment.
Many thanks,
Any advice and/or data on the Sp1069 would be greatly appreciated.
Thanks Moondog. The Concords have two identical SP1069 drivers in each box. One does the mid and base, and the second boosts the lower base (in the roll-off section I think). The arrangement was generally referred to a 2.5 driver configuration.
The Concord's Mid/base therefore requires a large enclosure and so does the Lower Base driver, so Kef used the same enclosure for both !!.
My thoughts on the Isobarik configuration are that I would be getting rid of the back pressure interference between the drivers with (hopefully !) a clearer mid/base and lose some of the lower base. This would turn it into a Kef Celeste with a much larger effective enclosure (Isobarik benefit).
The Concord's Mid/base therefore requires a large enclosure and so does the Lower Base driver, so Kef used the same enclosure for both !!.
My thoughts on the Isobarik configuration are that I would be getting rid of the back pressure interference between the drivers with (hopefully !) a clearer mid/base and lose some of the lower base. This would turn it into a Kef Celeste with a much larger effective enclosure (Isobarik benefit).
Using the same enclosure for the bass-mid and the .5 bass boost is common enough but for isobaric mounting I woudn't consider it doing any midrange at all, simply using the existing drivers for bass duty. I have been wrong before but I would be converting to a 3-Way for my own use. Never noticed the "Bass interference' with any of my own builds and I have made a few 2.5 Way speakers
I respect your opinion, and agree that there are much better detailed speakers available. My main listening room has more modern Linn active speakers which have wonderful detail, but I also like listening to music in my study through my Kef Concerto's, which sound 'fuller' and more 'musical' to my ears.
The proposed alterations to the Concords was just for the thrill of experimenting with building Isobariks (I used to have Linn Isobariks, which were nice, but that was probably due to their B110s).
On reflection, I think that I will go with your opinion and re-cap the Carlton's and sell them on, and keep my B110/T27 speakers in the ported boxes I built them in many years ago (but not used much). Then I must do something about my Kef Carltons which need a new B200, and also sort out my Pye Black Box.
Thanks for your input, it was helpful reading your views.
The proposed alterations to the Concords was just for the thrill of experimenting with building Isobariks (I used to have Linn Isobariks, which were nice, but that was probably due to their B110s).
On reflection, I think that I will go with your opinion and re-cap the Carlton's and sell them on, and keep my B110/T27 speakers in the ported boxes I built them in many years ago (but not used much). Then I must do something about my Kef Carltons which need a new B200, and also sort out my Pye Black Box.
Thanks for your input, it was helpful reading your views.
Anyone wanna take a stab the bass driver’s TS parameters…
…or perhaps the driver’s Qts. I believe it’s above .6 or higher; VAS on the low side.
Interesting the 303 uses one of these in a 17 ltr (.6 cu ft) closure, .7 system Q. The 304 uses, two as you have you’ve discussed, in a 38 ltr (1.34 cu ft) .8 system Q - doesn’t “add up.”
I’ve read repeatedly twice the drivers, twice the volume should net the same Q etc. A challenge I know.
PS I’ve owed a pair for 40 years. I’m considering two ported single driver speakers; tweeter TBD. Open to suggestions
Thanks for your help
…or perhaps the driver’s Qts. I believe it’s above .6 or higher; VAS on the low side.
Interesting the 303 uses one of these in a 17 ltr (.6 cu ft) closure, .7 system Q. The 304 uses, two as you have you’ve discussed, in a 38 ltr (1.34 cu ft) .8 system Q - doesn’t “add up.”
I’ve read repeatedly twice the drivers, twice the volume should net the same Q etc. A challenge I know.
PS I’ve owed a pair for 40 years. I’m considering two ported single driver speakers; tweeter TBD. Open to suggestions
Thanks for your help
PPS an image of the drive units they look kinda triangular
Ads - Drivers - KEF B200 tri mount version SP1069 drivers speakers, bass uni
KEF Concord B200 Series: 8” Bass Driver SP1069 (1979) | eBay
Ads - Drivers - KEF B200 tri mount version SP1069 drivers speakers, bass uni
KEF Concord B200 Series: 8” Bass Driver SP1069 (1979) | eBay
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