Reviving dead crossover help please

[dheming]

Hi
What is a motor run type please? How large is large value, coz it seems to have been established I would need very large pockets and a lot of room to put a large value film cap. Neither A nor B apply here
Hey, smilies are back!

Here's the wiki on Motor Capacitors. Motor run caps are commonly used in audio applications since they are an affordable way to get large value film caps. As an example, here is a 250uF 250V polypropylene film motor run cap on eBay for about $12: link. BTW, not all motor run caps are of the film type. Many are electrolytic so be careful when you are searching that you know what you're looking at.

 

[Too Tall]

Hi
I don't have a problem finding the 250uf 100v Bennic but I also need a 15uf and an 8uf polypropylene to replace the other two on the board. I can find the 250 and the 15 at Parts Express, but no 8uf. They have a lot of 6.8uf if that is close enough?
I'd prefer to source everything from one place, but Digikey's search system is pretty stupid very late at night. Maybe it's me?

The resistors don't have a value in Ohms, but one says 1RJ and the other 0R7J if that means anything to anyone?

I don't know if I have room to replace coils, especially with ones so big. Maybe in the center channel, but certainly not in the L and R Fronts. I don't know if there is any advantage to it; they are pretty expensive, at least at this size.

Thanks
Phil

First the writing on the resistors.

1RJ

R lets you know it is a resistor

J is the tolerance. If I recall that should be 1 %

1 is 1 ohm

Let’s say you have an 8.2 ohm resistor.
In that case it would look like this
8R2J

The R is also used as a decimal point.

If you were to buy from Parts Express, Madisound or other companies that sell a lot of parts for audio passive parts it will often tell you the wattage it can take and other information on the resistor.
Digikey does a huge amount of business but only a tiny amount of it is for audio passive parts. If I was repairing an electric motor or other electronic pieces I might look at Digikey or Newark, but for standard passive xovers I would look there last.

The 0R7J does not make a lot of sense to me.
0.7 ohms is not a typical value.
Any chance you read that wrong?

Something else that happens.
To fill in a range of values, say for a 25watt resistor they may go to several different manufacturers and they may use different naming protocols.

As for only buying from one company, it is fine when they have everything you need. It seldom works for me.

For the 8uF cap I would use the 8.2uF and not worry.

Lastly I picked the inductors with the idea that you wanted to “Upgrade” the parts.

Good Luck

 

[wintermute]

0.7 ohms sounds reasonable to me if it is the one in series with the cap on the woofer. This will most likely be to stop peaking caused by a resonance between the cap and the coil, the resistor dampens the resonance.

Tony.

 

[Too Tall]

0.7 ohms sounds reasonable to me if it is the one in series with the cap on the woofer. This will most likely be to stop peaking caused by a resonance between the cap and the coil, the resistor dampens the resonance.

Tony.

Yah, maybe.
I seldom work with dome tweeters anymore. I presume it is a dome in this case.
Its all compression drivers for me. I need to bring down the highs 15dB and more.
Cheers

 

[Pano]

I don't get the crossover. What are those caps doing? 1st order high pass/bass blocker at 80Hz?
And why 2 in series? Did they use polarized? The first post seems to indicate that they did.
I'd just get a Bennic/Dayton non-polar of about 230uF and be done with it. Put a small film cap (say 2.2uF) across it if you feel like spending money.

I don't think you need them in there, but have not seen the speakers. Maybe they wanted the roll off to mate it to a sub. The 80Hz point would indicate that. Maybe the woofers just don't handle bass well and that high pass cleans them up.

 

[wintermute]

Yes I think passive first order highpass at 80Hz.... It is a HT speaker, but why they would do it and not just rely on the receiver to do active filtering I don't know... perhaps in case someone sets the crossover to a higher frequency, or in case someone runs it just as a centre with left and right and no sub??

Tony.

 

[cogitech]

...or in case someone runs it just as a centre with left and right and no sub??

Tony.

This.

I have a pair of NanoSats, which likely have the exact same crossover in them. You can push a full signal through them hard and not blow the woofers because anything below 80 or so Hz never reaches the drivers. Mirage apparently doesn't trust the user to use the HT receiver crossover properly.

The ultimate "improvement" replacement part for those two caps is a piece of 18ga wire, IMO. However, this would obviously require the user to filter the low end appropriately on the receiver.

 

[phmosele]

Hi all

OK, here's some answers/comments.
TooTall, the inductors are just too big to fit in these boxes. Maybe the center, but not the other 4.

Resistor is definitely 0R7J for 0.7 as Wintermute opined - it's the one in series.

Piece of wire would do it I think, instead of the caps. My HT amp has a sub out at 100Hz. Frankly I'm surprised these things can take even that low...they are about 3 inches diameter. But someone suggested a couple of pages ago that it is probably 3dB down anyway.
I would rather throw anything below 150 at the sub. The amp crossover seems to be variable, but it always seems to reset itself, and nothing ever sounds different. I hate this amp with a passion.

Yep, they are dome tweeters.

I would love to replace the other two caps. I can find a 15uf 100v Dayton polypropylene at Parts express for about 6 bucks, but they only have an 8.2uF, not an 8. Anyone agree that it would be ok at 8.2uF please?

I don't have room for physically big coils, but if I have to live with the stock coils (which I think are 1.1 and 0.11mH, but some of it is in the glue) would it be a waste of time swapping out the caps please?
Phil

Thanks
Phil

 

[Too Tall]

As for the size of the coils make an outboard box with the xover in it. Make it as big as you need.