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-   -   help with crossovers and impedance (https://www.diyaudio.com/forums/multi-way/341220-help-crossovers-impedance.html)

Trevinni87 9th August 2019 01:04 AM

help with crossovers and impedance
 
if im setting up a center channel speaker using 4 speakers. 2 woofer, 2 tweeter, and crossover. if my reciever is looking for an 8 ohm load what ohm rating should i get each speaker to end up with the desired 8ohm load? and if it isnt too much trouble could you explain how it ends up there? i understand the math behind just the speakers and wiring them either series or parallel or a combo of the two but i get really confused once you add the crossover.

from what i understand when you add the crossover it takes on the ohm load rating of the woofer channel? so if the woofer channel is 8ohms and the tweeter channel is 4ohms then the reciever sees the whole thing as 8ohms but i feel like i misunderstood that.

any help would be awesome thank you so much guys.

rayma 9th August 2019 02:40 AM

You'd have to use two 4 ohm drivers in series to get 8 ohms. Two series 4 ohm woofers result in an 8 ohm load in the bass. Two series 4 ohm tweeters result in 8 ohm load in the treble. The crossover electrically blends these two 8 ohm loads so that the load presented to the amplifier is 8 ohms through the entire frequency range.

The woofer crossover lets the amp see the 8 ohm woofers in the bass range, but it unloads the amp in the treble. The tweeter crossover lets the amp see the 8 ohm tweeters in the treble range, but it unloads the amp in the bass. These two crossover sections are in parallel, so when one section unloads the amp, the other section loads the amp. This results in the amp being loaded with 8 ohms in the entire range.

Trevinni87 9th August 2019 03:00 AM

wow excellent answer that is exactly what i was looking for. thank you so much.

jareksy13 9th August 2019 07:45 AM

Help for JM Lab crossover repair
 
1 Attachment(s)
Hello,
Asking for help.
Can anybody send me actual schematic for JM Lab Olymp K2 loudspeakers' crossover?
I have bought the pair spekers and I found the sound of the them to be very strange. So I unscrew the mid-bass speaker to have a look at the crossover and found it to be in very poor condition (see the picture).
I can repair the PCB but must have the original schematic for the crossover to reconstruct it.
Thank in advance for your effords,
Jarek

buggers 9th August 2019 05:38 PM

Using 2 tweeters is a bad idea sound wise...

Galu 9th August 2019 05:53 PM

Quote:

Originally Posted by buggers (https://www.diyaudio.com/forums/multi-way/341220-help-crossovers-impedance-post5878469.html#post5878469)
Using 2 tweeters is a bad idea sound wise...

If so, a positive suggestion would be to use one 8Ω tweeter instead of two 4Ω ones.

P.S. +1 for rayma's excellent answer.

Galu 9th August 2019 06:12 PM

Quote:

Originally Posted by jareksy13 (https://www.diyaudio.com/forums/multi-way/341220-help-crossovers-impedance-post5877978.html#post5877978)
So I unscrew the mid-bass speaker to have a look at the crossover and found it to be in very poor condition (see the picture).

The physical condition looks OK to me, just a bit messy because of the hot glue applied to hold components in place.

The only components worthy of changing would be the non-polar electrolytic capacitors (the cylindrical ones). You will find the required values written on these capacitors.

What's written on the big grey cylindrical thingy?

Galu 9th August 2019 06:28 PM

Quote:

Originally Posted by jareksy13 (https://www.diyaudio.com/forums/multi-way/341220-help-crossovers-impedance-post5877978.html#post5877978)
I have bought the pair spekers and I found the sound of the them to be very strange.

Hi again Jarek!

I can't locate a circuit diagram or even an alternative photo of your crossover

It is possible that the previous owner has modified the crossover and that may explain the untidy hot melt glue.

That's why I am interested in discovering more about the grey cylinder which looks out of place to me.

jareksy13 9th August 2019 06:36 PM

Quote:

Originally Posted by Galu (https://www.diyaudio.com/forums/multi-way/341220-help-crossovers-impedance-post5878519.html#post5878519)
The physical condition looks OK to me, just a bit messy because of the hot glue applied to hold components in place.

The only components worthy of changing would be the non-polar electrolytic capacitors (the cylindrical ones). You will find the required values written on these capacitors.

What's written on the big grey cylindrical thingy?


Hello Galu,
I have the photo of original crossover (unfortunately I cant read the lettering on some elements) which certainy differs in many details from existing one:
1. No big inductance in bass section. Was replaced by capacitor.
2. No third power resistor on the PCB. Empty drilled holes.
3. Original PCB has some gaps grinded in few places. Have some extra winding jumpers too.
4. Big grey cap is a 40uF/450V one. They are using such components in fridges to start asynchronous motors.
My conclusion is the tweading job was done by a bungler.
Thanks for the answer,
Jarek
PS. Photo of original crossover can be seen on French internet webside.

Galu 9th August 2019 07:33 PM

Thanks Jarek!

Yes, as I finally suspected, modified by a bungler!

I now see why you require the crossover schematic so urgently!

Sorry I can't be of further assistance - would be interested in having the link to that french website though.


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