Speaker Crossover Wiring : Solve the Puzzle

Someone brought me an old Wharfedale model W-90 monitor speaker, a massive old beast with two highs, two midranges, and two 15" woofers. The problem was that the crossover circuits are damaged; two 50 ohm potentiometers were burned up, and someone had attempted to bypass them, getting the wiring mixed up in the process. I've drawn up a diagram of the components, numbering each component lead rather than show how they were hooked up. You can view the diagram here:

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I'm hoping that someone can figure out the arrangement, and rather than have to draw up a schematic for me, you can just point out which numbers to connect. Some notes:

-the connections between the high and midrange speakers appear to be original, though I cannot be certain

-the woofers are presently connected in series (each measures 4 ohms)

-values of the other components are as follows: C1 - 25 uF 50VDC C2 - 12 uF 25VAC (much larger than C1) L1, L2 - values unknown, but both look identical VR1, VR2 - 50 ohms, 5 watts wirewound

I played around for a while and was able to achieve a decent sound with the following configuration: 1-3-8-13, 2-18-24, 22-23, 4-5, 7-17, 9-10, 11-19,

14-21. This doesn't seem right though, since only two leads of each pot are used, and L2 isn't used at all.... Any help with this would be appreciated.
Reply to
Chris F.
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I should note that L1 and L2 both measure about 1 ohm.

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Reply to
Chris F.

The following is a guess. It would be useful to know the inductance of the coils, the impedance of the drivers, and the crossover frequencies.

The woofers would not normally be wired in series. I'm guessing that each woofer uses one inductor for a low-pass filter.

That leaves the caps. The 25uF cap would most-likely go in series with the midrange units, the 12uF in series with the tweeters.

Both capacitors should be non-polar. I don't know why the 25uF isn't.

Because the level controls can interact with the crossover, it's hard to know where they went.

This is a "common sense" configuration. We don't know what the Wharfedale designers were trying to do, or what driver problems they were trying to compensate for.

The probability of getting the "right" configuration is small. I once worked through the crossover for a classic two-way system -- the Advent -- and it was neither simple nor obvious.

Why haven't you contacted Wharfedale?

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Why should I have to look this up for you?

Reply to
William Sommerwerck

The owner of the speakers had contacted Wharfedale, but apparently the specs for these speakers were lost in a fire. Looking on the net, I see other people have encountered the same problem but nobody seems to know of a solution.

Reply to
Chris F.

I would suggest this... Use the inductors and capacitors in the "common sense" way I suggested, and measure the response of each driver pair separately. This will give you an idea of whether you're headed in the right direction.

Without knowing the impedances and responses of the "bare" drivers, there is no rational way to determine what the crossover was. There is no magic formula. One does not generally design crossovers without knowing the base behavior of the drivers.

You will have to figure this out on your own. We can make suggestions for starting points, but that's it.

Reply to
William Sommerwerck

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The 'L' elements of crossovers are often in parallel with the speakers rather than series, and may be combined with a 'C'. There are, however, many different configurations of crossovers, so it's virtually impossible to guide you with any certainty. As to the pots, they could have been for level, or phase adjustment. My money would be on level, in which case only two legs being in use - i.e. with the pots connected as variable resistors, one in series with the two tweeters in parallel, and one with the two mids in parallel - would be the expected configuration.

If you put "passive three way crossover designs" into Google, you will get an information overload on them, that you might be able to pick the bones out of to decide on what your design originally was or needs to be.

Arfa

Reply to
Arfa Daily

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I'd ask around at Audio Karma. Someone may have a set of those and could trace the wiring for you.

Reply to
boardjunkie1

As to the pots, they could have been for

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In speaker crossovers, L-pads are generally used as L-pads -- just a suggestion. Speaker manufacturers are extremely cost-conscious and won't overspend -- especially on something that doesn't show.

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Try back issues of Speaker Builder or the Audio Amateur for information on crossover design. Also Siegfried Linkwitz's site.

Reply to
spamtrap1888

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