Goodmans Minister

[Kei]

Inherited these from my dad a few years ago and spent some time replacing the drivers and tweeters as they were knackered. (was told the drivers that were fitted at the time were Elac 8", but there were no markings and they weren't a matched pair anyway) The original tweeters were goodmans DT4 silk domes. I replaced the main drivers with a matched pair of KEF B200 SP1063A and the tweeters with a pair of Seas prestige H1280-06 22TFF tweeters. I reused the original crossovers that were there. The cabinets are 24L or 0.85cu.ft and ported with a 52x155mm port. Having read the specs on the kef drivers I've listened to them with the ports plugged. I have also tried unplugged too and found little difference. (although I've left them unplugged) Overall I find them quite pleasing to listen to, however I don't know if there are any improvements that I could make to them.

This is how they look now.


The crossover AFAIK is 1st order for the LF/midrange and 2nd order for the HF. The capacitor is 4.7uF 63V. I don't yet know the value of any of the other components. (I'd rather not have to dismantle them to find out)



I'm guessing a custom crossover for them might be better suited. If anyone can rough guess (or knows) the crossover component values can plot the response for me, that would be a great bonus.

[Kei]

I got some ClarityCap ESA replacements for the original erie bipolars. (cheap enough and supposedly a good performer, didn't fancy those ridiculously expensive mundorf silver items)

I measured the actual value of the originals and they came up as 6.4 and 6.5uF. The new ones are measuring a whisker over 4.7uF. There is definitely a difference in the way they sound, I reckon its a tad brighter which is probably down to the loss of the capacitor's ESR.


The B200 is an SP1063. and the Tweeter specs are here.


As far as i can tell this is how the crossovers are wired up. (inductors are unknown values as i have no inductance meter)


Since my speakers are very similar in design to the KEF chorale would it be beneficial to replace/upgrade these crossovers to something like the KEF chorale crossover kits they have on falcon acoustics?

These are the chorales: (They don't use the SP1063 unit, AFAIK it's an SP1014 and T27 - SP1032)

[VaNarn]

The original 8" driver was a paper cone unit from the O.E.M. range of Goodmans speakers. The crossover network should have the inductor in parallel across the tweeter .The tweeter needs an 'L' pad of -4dB to bring its level down to match the B200,s sensitivity;it has nothing to do with capacitor ESR.The Bextrene cone has problems in the mid-range and while correction networks may help to minimise the effects,maybe a better bass/mid range driver could be your next step.Meanwhile,since the cabinet is too small for the KEF bass driver it may help to add some wadding to the port tube.

[Kei]

I think i've listened to them as they are for a bit long and as such quite used to the brightness. Setting the parametric EQ up to knock 2k and up down by 4dB it seems a touch muffled compared to what i'm used. I've had a look and this is what an L-pad calculator suggests.

For -4 dB

Resistors
R1 = 2.21 Ohms - can get 2.2
R2 = 10.26 Ohms - can get 10.

11W should be sufficient for a tweeter? (50W luxman amp powering it)

[Kei]

a closer match for the L-pad arrangement is -3.5dB

Resistors
R1 = 2.06 Ohms
R2 = 11.96 Ohms

The crossover that i was looking at for these speakers was this one.

This is the pcb design.

[system7]

You've got your work cut out for you, setting these up by ear.

You can't realistically notch any nasties on the woofer, and really falcon acoustic's Chorale filter is made for a different B200 driver, so forget it. People do get decent results without the notch though, so there's hope.

At simplest you can try your tweeter attenuator on the Re= 5 ohm SEAS unit. And a rolloff capacitor on the woofer. Could be anything between 5 and 12uF with a little optional 2 ohm resistor to damp it a bit, I'd reckon. I've roughed up a circuit that incorporates some 4dB of tweeter attenuation and a calculated rolloff Zobel for the SEAS. Might be OK. 3.3uF for the tweeter is just a bit gentler than 4.7uF, but not a big deal.

BTW, your tweeter filter looks as in my diagram. What you've sketched would fry the tweeter with bass.

[LafeEric]

Originally Posted by system7

...BTW, your tweeter filter looks as in my diagram. What you've sketched would fry the tweeter with bass.

Why use a tapped inductor? What does that do?

[system7]

Originally Posted by LafeEric

Why use a tapped inductor? What does that do?

The (obsolete) idea of tapped inductors is they include a coil and an attenuator all in one. But I haven't got a clue what KEF are doing there in the Corelli. It makes no sense to me!

[Kei]

Looking at the datasheets for the SP1063 and the SP1014, there isn't much difference between them, The 22TFF tweeter doesn't seem greatly different to the T27 either. Could i use the falcon PCB (they suggest it can be used for various B200/T27 combinations) and use my own choice of components to make a more suitable unit?

[system7]

Originally Posted by Kei

Looking at the datasheets for the SP1063 and the SP1014, there isn't much difference between them, The 22TFF tweeter doesn't seem greatly different to the T27 either. Could i use the falcon PCB (they suggest it can be used for various B200/T27 combinations) and use my own choice of components to make a more suitable unit?

I think you're RIGHT there, Kei. Very Similar!

Wouldn't surprise me if KEF sold off out of spec SP1063 as SP1014!

Below is the Kefkit1 SP1106 crossover, aka known as the Chorale. I see the same components as the Chorale schematic I posted earlier. You get the notch too.