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opinions on an unusual crossover design

Kneedeepinit

Kneedeepinit

Super Member
I purchased a pair of Wharfedale Rosedale ( W70E ) speakers. One mid range is blown so I am waiting for the replacement to come. While waiting, I have decided to recap the crossovers as they are over 40 years old.

The design is unusual, IMO. I have zero experience with crossover designs so maybe this is normal but there are a couple of things that seem wierd to me.

The speakers do not sound great but that may be due to the blown mid range. Both crossovers are identical but it appears that they may have been worked on in the past. A couple of the conections are soldered differently when comparing the two.

w70erosedalecrossover_zpsb2b2fdd3.jpg


the things that seem crazy is that the black speaker input wire goes directly to the reds on two drivers and to the black on another. Also, the black and red speaker input wire go to one driver wire (black tweeter wire)
 
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What you have I believe is the midrange wired reverse phase from the woofer and tweeter. Depending upon the type of filter it is and its "order" a phase reversal for one or more speakers may be required. I don't know enough about it to know if it was needed here or not.

Shelly_D
 
shelly_d said:
What you have I believe is the midrange wired reverse phase from the woofer and tweeter. Depending upon the type of filter it is and its "order" a phase reversal for one or more speakers may be required. I don't know enough about it to know if it was needed here or not.

Shelly_D
Click to expand...

the interesting thing about the speakers and your comments is that one speaker has very low volume in the mid range speaker and the other one has a wierd vibration. I assumed it was blown so I have ordered another mid.

Maybe the previous owner played with the crossovers and they are just ourt of phase??
 
Kneedeepinit said:
the interesting thing about the speakers and your comments is that one speaker has very low volume in the mid range speaker and the other one has a wierd vibration. I assumed it was blown so I have ordered another mid.

Maybe the previous owner played with the crossovers and they are just ourt of phase??
Click to expand...

They look completely normal to me. Don't worry... because the electrical filter messes with the phase of the mid, wiring things this way actually give you an in-phase acoustic wave.

I would guess your problems are coming from something else.

-k
 
I would recap a speaker that old with modern caps first, then work on drivers. Particularly if something has a low volume. Old caps can act pretty funny. The vibration may be due to a rubbing voice coil, BUT if there is a bad cap in the midrange section, it's possible to get more bass into the midrange than the design spec.
 
BTW, your drawing is clear enough, but conventionally, crossovers are drawn with the drivers at right, each driver having both wires coming out of it.

Here's a good link about crossovers:

http://www.colomar.com/Shavano/crossover12db.html

Anyway, what you have is:

An inductor that allows bass into the woofer.

the midrange circuit has a smaller inductor combined with a cap. Inductors are low-pass(they pass everything below a certain frequency) and caps are high-pass (they pass everything above the cutoff frequency). Putting both in the midrange circuit ensures the middle of the range goes to that driver. It is unusual to see them in series though. Usually the signal comes into the cap, and after the cap, the inductor is used to dump whatever low freq. residue that gets through the cap, back to ground.

Which is exactly what was done in the tweeter circuit. That purple inductor is a shunt. The 3.3 ohm resistor is to tame down the tweeter because its output was too high compared to the other drivers.

This is a pretty typical crossover, 1st order to the woofer, and 2d order in the mid and tweeter.
 
I see a normal crossover,

1st order for the woofer,
1st order for the mid-range, and
2nd order for the tweeter. With addition of a resistor to attenuate the tweeter.

According to the color codes, the mid-range seems to be phase reversed.

Here is a very helpful page about crossovers, with examples and more:
http://www.bcae1.com/xoorder.htm
 
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