Mirage M-760 Crossover Build

[fonzieguy]

To make a long story short, I ended up with a pair of these speakers recently and love one of them but the other speakers crossover is not functioning correctly. I found out that it is a 2nd order butterworth low pass and a 3rd order butterworth high pass with the crossover frequency at 2200hz.

Was looking for some sort of new replacement I could drop in like this:
http://www.parts-express.com/pe/show...number=260-142

But after doing a lot of research I kind of wanted to take a shot at rebuilding it myself with the 2nd order low pass and 3rd order high pass.
Now it is really pretty easy to find diagrams on how to build a low pass or high pass, but I really cannot find much information on combining the filters into one full crossover.
So I drew something up and really need someone who knows crossovers/ electronics and can tell me if this will work the way it looks.

In the original crossover they used a few resistors, which I don't quite understand why yet. Literally I drew a 2nd order butterworth low pass and 3rd order butterworth high pass and combined them the way that made sense to me.

I am attaching pictures of my drawing and the original crossover. They are obviously not the same but if someone could let me know if what im proposing is actually feasible that would be awesome.
Also if anyone knows what Mirage was doing or has any other ideas to throw out that would be extremely welcome.
C for capacitors and L for inductors.

[Chris Roemer]

To make a long story short, I ended up with a pair of these speakers recently and love one of them but the other speakers crossover is not functioning correctly. I found out that it is a 2nd order butterworth low pass and a 3rd order butterworth high pass with the crossover frequency at 2200hz.

Was looking for some sort of new replacement I could drop in like this:
http://www.parts-express.com/pe/show...number=260-142

But after doing a lot of research I kind of wanted to take a shot at rebuilding it myself with the 2nd order low pass and 3rd order high pass.
Now it is really pretty easy to find diagrams on how to build a low pass or high pass, but I really cannot find much information on combining the filters into one full crossover.
So I drew something up and really need someone who knows crossovers/ electronics and can tell me if this will work the way it looks.

In the original crossover they used a few resistors, which I don't quite understand why yet. Literally I drew a 2nd order butterworth low pass and 3rd order butterworth high pass and combined them the way that made sense to me.

I am attaching pictures of my drawing and the original crossover. They are obviously not the same but if someone could let me know if what im proposing is actually feasible that would be awesome.
Also if anyone knows what Mirage was doing or has any other ideas to throw out that would be extremely welcome.
C for capacitors and L for inductors.

Well, your drawing is what you say it is, but you've got no specific component values.

Thing is, unless there's a broken connection on your old XO, about the only thing that can fail are the non-polarized electrolytic caps. You could try cutting them out and putting in new ones. That type tends to go bad after about 30 years or so. Not sure how old these are.

The resistors are an important part of the big picture. They're used to match the output levels of different drivers, and can also be used to level out impedance fluctuations.

Chris

[fonzieguy]

I have looked everywhere and emailed Mirage(Klipsch) themselves and can not get the specs on these. I only have the specs on one of the capacitors, the lower one, and not the other ones. I guess I could hope that its the broken one. These speakers are from about 1989-1990 so they are a little over 20 years old now.

[nbuk]

So is one speaker still ok ?, if so, you would need to measure the components in the good one and "back engineer" the crossover, and rebuild both of them, should not work out too expensive and you will learn a little on the way. Replace the old NPE caps with some cheap Daytons from PE, and some el cheapo resistors, your coils will probably be ok, and you should be good to go.
Though I am not familiar with the M-760, Mirage have a reputation for being above average and you may be pleased with the results.

[fonzieguy]

Ok I see what you are saying, I have a digital multimeter here, am I just checking resistances on all the caps and resistors? Is there a way to check the coils with that?

[nbuk]

You will need to measure capacitors and inductors with something like this, an LCR Meter,http://www.mcmelectronics.com/product/72-8155
Hope that link works for you, a regular "multi meter" will not do. If you can get the values from the good crossover, then you will be good to go.
You can get an LCR Meter for about $35 on fleabay that will do the job.

[Chris Roemer]

Ok I see what you are saying, I have a digital multimeter here, am I just checking resistances on all the caps and resistors? Is there a way to check the coils with that?

If your XO shot was clearer, I could almost read the caps. They LOOK like they'd have the "uF" rating on the case, somewhere. I can see the voltage "100v" on at least one of them. I can almost make out the resistors, 1.4n and 3n?, maybe?

Draw a schematic off the working XO. If you live near anyone with an LCR meter (or a "Woofer Tester"), they might read the component values for you.

How do you KNOW the XO is bad? Did you swap drivers onto the working XO, just to be sure?

chris

[fonzieguy]

Yes I have switched woofers with the ones from the good speaker, and no change. I actually just managed to pull the capacitors off the glue and can read all their values now. They all say bi-polar, does that mean they need to be replaced with bipolar or non polarized caps? Like these: http://www.parts-express.com/non-polorized-electrolytic-capacitors.cfm

Or can I use something higher quality like these: http://www.parts-express.com/dayton-loudspeaker-precision-1.cfm

And should I go ahead and replace the resistors with the dayton audio 10w or the Mills 12 watt?

Will it matter if the values aren't direct, like the 8.2uF vs 8.0 or 1.5 on the resistor vs 1.4?
Attaching pic.

[Sydney]

Crossover caps are Non polarized.

Will it matter if the values aren't direct, like the 8.2uF vs 8.0
I prefer to trim up a value: Add a small cap in parallel with the next lowest value.

[2leftthumbs]

I think most people would just try replacing the bipolar electrolyic capacitors with polypropylene capacitors of the same value. The coils are unlikely to fail as are the resistors, unless they were faces with a really high power situation.

[2leftthumbs]

I personally wouldn't worry much if the capacitor values were within 5%. Keep in mind however that electrolytic capacitors usually err on the high side and poly caps usually err on the low side.

[fonzieguy]

Ok then, I ordered 3 new dayton caps, we will see how that goes.
Thanks everyone for the help!

[Mike2112]

Also while you have the crossover out of the box you should re-heat all the solder at all the connections and maybe add a little more. There is a possibility of whats called a cold solder joint that can cause a loss of connection. also reheat the solder connections that are on the binding post. I have a pair of Marantz HD-77's from 1976 that i got off of CL that had that problem an a cold solder joint was the issue.

[Chris Roemer]

Also while you have the crossover out of the box you should re-heat all the solder at all the connections and maybe add a little more. There is a possibility of whats called a cold solder joint that can cause a loss of connection. also reheat the solder connections that are on the binding post. I have a pair of Marantz HD-77's from 1976 that i got off of CL that had that problem an a cold solder joint was the issue.

Also (since you'll have nearly everything apart) just check the resistors for the proper impedance, and the coils too. Their DCRs will probably be pretty low, like < 1.0 ohms, but you should be able to read them.

Still a good idea to sketch out the XO layout, just for future reference.