B200 Kef Drivers

[michelino]

Playing another time with values of inductance and caps... One minute please
The 40uf cap is not a problem, i've got a stock os 20uf polypropylene at home (paid about 1.2€/pcs).

What do you mean with "Offsetting the drivers", Steve? The drivers are near one corner (left/right)?

[system7]

Offsetting exactly like the B&W design does, FWIW, that's the RHS loudspeaker:



This is a well-known BBC technique to avoid some bafflestep problems:
Arpeggio Loudspeaker

Flipping masterclass, that Morgan Jones article. BTW, the inverted tweeter thing is optional, but I think it has a lot going for it since it is more phase linear, since the centres are equidistant from the listener.

When you add a 6 ohm resistor to the tweeter filter input, it changes the capacitor values to symettrical. I always like symettrical. Such elegance:
LC Filter Design

This is what you do at radio frequencies to match source and load.

[Mr. dB]

Originally Posted by system7

Offsetting the drivers is actually quite vintage Bowers and Wilkins, as in this KEF bextrene/celestion tweeter based DM2A. A very fine loudspeaker which I liked a lot. The inverted tweeters are designed to work nicely in phase.

That's not a KEF woofer, B&W made their own.

[system7]

Originally Posted by Mr. dB

That's not a KEF woofer, B&W made their own.

You are doubtless right, but I really don't care from a system's engineering point of view. All Bextrene in the end, whatever that is made from. Let's stay on-topic.

Michelino, it's quite OK to use two 20uf capacitors in a balanced configuration if you have loads lying about. Put 20uf on live, and 20uF on the earth rail in a second order configuration. Amounts to 10uF overall in the end. Some people think that balanced is better. I can see valid reasons for that reasoning.

[michelino]

Good morning Steve!
After some simulations, it seems that 20 uf + 20 uf for the 3rd order isn't the best configuration. But it's only a simulation! So i ordered 10uf caps and then I'll try with mic and ears ... Even for the b200 crossover, I've ordered bigger inductor since they cost quite the same...

[MykhailoM]

Originally Posted by Neopsp

What drivers would you guys recomend from KEF ranges (bout the same age as the B200).
You see there is this audiophile hifi place near me that has got old replacement stock from the KEF ranges. The guy is wanting to get rid of it, and is selling it for quite cheap. Does anyone know the SP 1193?
Thanks
Neopsp

Hi Sure I came across this sp 1193 drivers. I have KEF CARA 1985 2-way speaker which I would like to MODIFY to better sounding speakers wit the tweeter and Mid/Bass drivers preserved. I want to buy technically suitable Bass Drivers to go with original KEF drivers as they lack bass. Mid and High frequencies to me are GREAT but the problem with bass or correct musical performance to drums.
Here is the link to my opened speakers
https://plus.google.com/photos/10396...62045529170897

This using Mud/Bass drivers kef type sp 1193 I like it.
I 'm looking to buy paper cones specifically for handling bass.

I will need to modify Crossover from original 2-ways to high quality custom made 3-way crossover. I came across of a few people I found on the internet and eBay who sell different crossovers to help me with modification. The only challenge I think is to find KEF drivers Technical Specifications in order to prepare individual crossovers properly.

So far I have this details:

Specification: Cara
System Type: Two-way, stand-mount/floor standing
Enclosure type: Passive radiator
Size: 600 x 247 x 230mm (23.6 x 9.7 x 9.1 inches)
Weight: 7.9kg (17.3 lb)

Nominal Impedance: 8 ohms
Rated maximum power: 100 programme
Frequency response: 70Hz to 20kHz +/-3.0dB at 2m on design axis (-6dB at 55Hz)

Sensitivity: 90dB for a pink noise input of 2.83V (anechoic conditions)
Maximum output: 110dB on programme peaks under typical listening conditions

System: SP3076
Drive units: B200 bass unit (SP1193), BD200 passive radiator (SP1185), T33 tweeter (SP1192)
Crossover: SP2085

This is all I have so far. Is anyone know where to get the technical specifications? Is anyone doing or planning to do DIY on KEF speakers?

I truly want to get the best with this wonderful KEF paper drivers, sound very natural For the bass driver I found this model

AUDAX AM210G0
http://www.audax-speaker.de/index.ph...articles&index[shop_articles][action]=details&index[shop_articles][data][shop_articles_id]=16

and I think Most PREFERABLE

AUDAX HM210G6

audax speaker units from cadaudio.dk

If anyone has any ideas please join in.

[system7]

OMG, MykhailoM, that is SO interesting! I didn't know KEF made a B200 SP1193 with a cardboard cone...

Reckon I've got one!



Restoring Monitor Audio R300 bookshelf speakers.

You won't get more bass by adding another woofer. The 23L cabinet of the KEF Cara will be the limit. In fact the ABR passive thingie is probably as good as it will get. That unit was made by KEF for the Laskys Hifi chain. Crossovers really aren't hard though. Looks like you have a third order tweeter and second order bass XO there.

[MykhailoM]

Hi Steve, I'm planning to make a new cabinets to accommodate the Bass (third driver) unit. I will be checking what is the minimum liters required and I think will either make them taller or dipper. Internal rewiring will need to be also changed to silver plated pure OFC copper between crossover and Mid/Bass drivers. I just thought in order for someone to make a custom crossovers they may need drivers specifications which I don't have and that is what bothers me.

[system7]

If I were you, I'd try something much more straightforward. 6dB Bafflestep correction:
Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits

It's effectively bass boost. The other crossover values are impacted. You attenuate the tweeter with a 6-7 ohm resistor on the input of the filter too.

That bass unit is unbalanced without some bafflestep. The T33 tweeter ferrofluid is probably drying out by now too. You need to write down the current crossover component values to go further. Caps are readable, coils, well you need a good multimeter with an inductance scale. It's usually measured at 1kHz.

Edit: FWIW, the bass unit is Re=6 ohms on mine. You'd need to look up or measure the tweeter resistance and usefully, its inductance Le. Can't be far off 6 ohms too.

[speakerman19422]

In the early days of B&W they used some of the Audax line. There is a website by some of the former employees that tested the drivers.

Contrary to popular opinion there were several other reasons Bextrene was phased out.
Bextrene cones could not be used in auto sound.
They would melt in the heat.
Polypropylene could with stand auto sound environments.

Ferrofluid should last 30 years.

There were some high sensitivity bextrene cones made for oem uses. They used thinner cones longer pole pieces and oversized magnets approaching the double stacked magnet approach in todays designs.