Wharfedale Diamond II crossover...hmmm

[freefallrob]

Hi all,

This is the front and back of a Wharfedale Diamond II crossover.

https://public.bay.livefilestore.com/y1p3X-qX4hJqowYWcZNJrba17ckxbQK5LW_1rmJirSGztWXfzvYsyiOk ULT3H8zM2cV_zvjHoRc2qiVDeD6Wl6j6Q/dia2coverfront.jpg?psid=1


https://da3fhq.bay.livefilestore.com/y1pQXjPzUXtwV9znIwGGs1_492q4FIXwKwlYdgG7VPBGLp3UJ8 LaNvtKd-7RX4yeJPEs6jcYE1psMZWQ2XxXUMTO4FxOwll20W8/dia2coverback.jpg?psid=1

I guess what i'm looking for is a little more understanding of what does what and why.

Red and black feed the mid/bass unit, blue and yellow feed the treble. I've marked plus and minus for the input form the speaker terminals.

To the untrained eye (me!) it looks like there is a big capacitor in series with the mid bass unit (why?) and a resistor (level match?) and small cap (high pass?) in series with the treble and also an inductor in parallel (? not sure ? roll off the low end of the tweeter?) with the treble?

The speaker states the crossover point is 5000hz.

I'm interested as I was thinking of modifying them as a first 'journey' in to speaker understanding, perhaps fitting better quality & newer crossover components and in the long run building my own little speakers.
I'd also read an article by Russ Andrews(!?) about replacing the crossover with a single capacitor and maybe resistor, but I admit to being rather blind technically to the consequences of this...

Thanks for any input,

Rob.

[Stratmangler]

Big cap is a high pass filter for the mid/bass unit - it's a little driver, and can't cope with serious bass.
The Diamond II was designed to use wall/corner reinforcement in the low registers.

The cap/resistor arrangement for the HF unit is again hi-pass (capacitor), with attenuation (resistor).

[Reid Malenfant]

Chris is spot on :) The inclusion of the 450uf capacitor forms a 5th order rolloff along with the reflex port in an attempt to lower the input power below the port tuning frequency to attempt to prevent driver over excursion.

Looks like a 12Db/octave roloff for the tweeter below 5KHz (if that is correct) & as I can't see any other components I'm guessing that the bass/mid must have a fairly clean natural rolloff of it's own at about the same frequency :)


Only the capacitors are worth changing & possibly the power resistor, though you'll have difficulty finding a quality replacement for the 450uf :eyebrows:

Might be worth seeing if you can get a bunch of 2 or 3W film resistors to replace the wirewound or find a non inductive wirewound resistor of the same power rating :)

[freefallrob]

Hi thank you for the replies chaps, interesting I did wonder what that big blue cap was doing, I expected to see an inductor to roll the mid/bass off, but it seems it requires some help down below.

Having had a search around the net on the series cap, it seems that they can be used to artificially 'extend' the bass end of a driver in a sub optimal enclosure...though my understanding of it isn't quite there yet?!

I see what you mean about the 450 cap, not many nice ones about at all......but i'll see what can be done with the others, just for fun of course:).

I do find them a little coloured and box bound, but involving to listen to, perhaps a few component changes will open them up a little.

Any recommendations of what type and a good place to buy from??

Cheers,

Rob.

[DSJR]

With a clean and preferably non vinyl source (or vinyl with a VERY clean LF performance), the series cap on the bass unit could well be removed and the driver allowed to breathe freely. I heard similar once done externally on some Rogers Export Monitors to stop the cone-flap on record warps. I saw the effect but didn't hear any midrange loss in fairness. You may feel differently though. I'd also suggest that improving the tweeter crossover may open a bigger can of worms in the quality of the tweeter itself no being good enough - but 5K is so high, relatively speaking, that putting in a better cap and resistor may just make things "snappier," rather than "better."