Speaker Crossover Wiring : Solve the Puzzle

[Chris F.]

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:

http://s282.photobucket.com/albums/kk275/packrat79/?action=view&current=WharfedaleSpeaker.jpg

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.

 

[Chris F.]

I should note that L1 and L2 both measure about 1 ohm.

"Chris F." <zappyman@hotmail.com> wrote in message
news:4d961cda$0$3982$9a566e8b@news.aliant.net...

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:

http://s282.photobucket.com/albums/kk275/packrat79/?action=view&current=WharfedaleSpeaker.jpg

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.

 

[William Sommerwerck]

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?

http://www.wharfedale.co.uk/Home/tabid/37/Default.aspx

Why should I have to look this up for you?

 

[Chris F.]

http://www.wharfedale.co.uk/Home/tabid/37/Default.aspx

Why should I have to look this up for you?

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.

 

[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.

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.

 

[Arfa Daily]

"Chris F." <zappyman@hotmail.com> wrote in message
news:4d961d4e$0$3983$9a566e8b@news.aliant.net...

I should note that L1 and L2 both measure about 1 ohm.

"Chris F." <zappyman@hotmail.com> wrote in message
news:4d961cda$0$3982$9a566e8b@news.aliant.net...
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:

http://s282.photobucket.com/albums/kk275/packrat79/?action=view&current=WharfedaleSpeaker.jpg

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.

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

 

[boardjunkie1]

On Apr 2, 6:09 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"Chris F." <zappy...@hotmail.com> wrote in message

news:4d961d4e$0$3983$9a566e8b@news.aliant.net...









I should note that L1 and L2 both measure about 1 ohm.

"Chris F." <zappy...@hotmail.com> wrote in message
news:4d961cda$0$3982$9a566e8b@news.aliant.net...
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:

http://s282.photobucket.com/albums/kk275/packrat79/?action=view&curre....

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.

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

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

 

[spamtrap1888]

On Apr 2, 3:09 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

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.

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.

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.

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