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hans 67
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Location: Holland
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 Posted: Sat Jan 14, 2006 9:55 am Post subject: Concerto SP1002 crossover? |
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Hello all,
I have a pair of Concertos with the SP1002 crossover.
Does anybody have the schematics?
I can figure out myself the circuitboard, but I am not able to measure the inductances.
Hans |
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ColinR
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| Posted: Sat Jan 14, 2006 10:37 am Post subject: |
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Has it got a date code or a serial number?
Email me a picture if it has a serial number, your Concertos will also have a veneered front baffle. |
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hans 67
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Location: Holland
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ColinR
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hans 67
Intermediate Contributor 25+
Joined: 11 May 2003
Posts: 39
Location: Holland
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| Posted: Sat Jan 14, 2006 5:05 pm Post subject: |
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I have posted the schematic of the crossover:
http://www.dse.nl/~hifi/concerto/index.htm
I am not sure about the 6 uF capacitor, I could not read it clearly.
It is definately different to the SP1004!
Hans |
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ColinR
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| Posted: Sat Jan 14, 2006 7:33 pm Post subject: |
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So why is it different folks?
Well if you could see the magnet on the B110 you'd find that it's diameter is about 0.25" greater compared with it's later bretheren from 1975, which are in turn are deeper than those from 1985.
Remember the slide rule, 8086 & 386 processors  ?
What are the resistor values btw?
Are they in a ~3:1 ratio? |
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hans 67
Intermediate Contributor 25+
Joined: 11 May 2003
Posts: 39
Location: Holland
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| Posted: Sat Jan 14, 2006 9:15 pm Post subject: |
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Why different?
I have not seen resistors in the SP1004 DN12 network. And the values of the capacitors are different.
Or do you mean that the B110A from 1971 is different from those in 1975 and 1985. And I do mean not only mechanical, but also acoustical?
I do not understand your "slide rule".
The series resistor reads "3R0", I think, I am not sure. I can not read the parallel resistor.
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hans 67
Intermediate Contributor 25+
Joined: 11 May 2003
Posts: 39
Location: Holland
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| Posted: Sat Jan 14, 2006 9:29 pm Post subject: |
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Does these differences mean that if I want to replace my crossovers that I need some SP1002s and that I can NOT use SP1004s?
Hans |
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ColinR
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| Posted: Sun Jan 15, 2006 12:08 pm Post subject: |
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| Quote: | | Or do you mean that the B110A from 1971 is different from those in 1975 and 1985. And I do mean not only mechanical, but also acoustical |
Yes in all cases, if all the drive units were from 1971.
Your B110 should be a A6362 (proper B110A SP1003 appear later, after April 1974, there is an intermediate design before that, using the same big magnets but with a different smaller voice coil also designated SP1003!) and your T27's are A6535 ( after April 1971).
T27 SP1032 from April 1973 btw.
With the B110 being more efficient (hence the attenuation) and the T27 A6340 being the first production model, (up to April 1971), logically you will get a difference in crossover topography and your SP1002 crossovers are an overhang from that earlier varient.
So you have a "rare" but not particularly valuable pair of speakers.
| Quote: | | do not understand your "slide rule" |
Hmmm, I was just indicating that the changes in mathematics technology and computing power over time had an influence upon magnets and voice coil design.
Can you remember (or find out), what 60-70's continental engineers used before computers, it was a circular version of the UK/US slide-rule?
| Quote: | | I can not read the parallel resistor |
Please try to borrow a simple 10Euro meter and find out.
| Quote: | | Does these differences mean that if I want to replace my crossovers that I need some SP1002s and that I can NOT use SP1004s |
On your 12/05/1971 birds you should firstly, either impliment the series/parallel resistors to pad down the output of the B110 or install a 25 Watt L-pad in the circuit to do the same job.
Or just try it, you won't do any damage and might prefer the silghlty "forward midrange" presentation.
I suggest you get your replacement parts/modern crossovers from Malcolm Jones of Falcon Acoustics, being KEF's first employee, he'll remember the design and may be able to offer some additional suggestions.
Edit March 2006
The parallel resistor is 15R btw, padding the B110 down by 4dB. |
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