Audio Crossover




Introduction: Audio Crossover

This Instructable show how to make your own audio crossover.
My circuit garranties excellent high class audio quality.
Just a new design to reduce crossover frequency losses.

In this instructable you'll need the folowing items:

A drill
Pcb board
A soldering iron
Deoldering Pump
Ferric Chloride or any other Cooper echent
A horizontal drive transformer ( found in televisions)
10uf and a 2.2uf non-polarized capacitor
1.5 mm to 3.5 mm drill bits
A  speaker box with an tweeter and loudspeaker
A digitial or analog multimeter
A permanent maker
Styrofoam Plate
Six strips of wire preferable three different colours about 1.5 metres
Surgical Alcohol

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Step 1: Summary of Operation

This is the schematic, simple and easy to make if your not doing the pcb.
It can be placed on a breadboard with ease, overall it shows you how to connect it.

Well the transformer that i used can be found in a crt television set and it must be selected based on the power rating of your speaker. 
I have a 15W Loudspeaker and a 5W tweeter this transformer is fairly small, so if you plan to have speakers that are very powerful i advise you to get a transformer of similar ratio but bigger. The transformer's ratio is 1 : 5.
Its primary resistance was 0.8 ohms and secondary 3.4 ohms

The same goes for the capacitors the voltage range is small like 16v -50v for small power applications. As you increase your output power the voltage of the capacitors must increase to the range of 100v -250V. The value of the capactors usually stay the same. Use non polarized capacitors because they wouldnt be damaged by the alternating voltage.

Step 2: First Step

Get your transformer and measure the resistances of the pins.
Mark the side of the transformer with lowest resistance with the marker this will be your primary for the circuit.
Another way to find the primary of the transformer is to find the larger gauge wire on the transformers connector pins.

Now get the pcb board and place the board with the copper facing down, put the transformer in the middle of it .  Take the marker and place marks under the pins by just leaning it to one side slightly. Do this for all four corners.

Please place two marks for each capacitor at sides of the transformer making sure that they are perpendicular  to the primary and secondary windings. My lines in my case are 1.0 cm apart.

Also place two more marks parallel to both capacitor marks labelled C1 and C2 on in the picture, and place two more dots parallel with the transformer secondary the unmarked side.

Two other marks are inserted at the sides of both capacitor pin out marks. There are also a two dots placed in front your transformers primary. There is a picture showing clarification below.

The end  result of how this should look is in a picture tagged end result.

Step 3: Drilling the Prepared Pcb

Drilling Time!

Get your drill out at this time i shouldnt have to tell you how to use a drill, it is advised to use goggles and a dust mask at this time. 
Take caution in in everything you do safety comes first. 

Just take out the drill, find the key and release the chuck depending on if you have a jacobs chuck or not u'll know what to do with it.
Find the appropriate bit , 1.5mm worked for me.
Just drill all the marks and we're on to the next step.

Be sure to wipe the pcb board clean with some alcohol and a piece of cloth.

Step 4: Laying the Pcb Tracks

This is also another easy step and you should be able to do it once you have use a dot to dot book before.

Take the drilled pcb board and place it on a flat surface. Get the permanent marker and follow the outline that i have in the photo above its that simple.

Step 5: Its Ecthing Time

Get the sytrofoam plate and place the pcb in it.
Get your gloves at this time be very carefully that you dont spill the ecthant near any metal like cooper, silver, nickel etc.


Pour the ecthant into the plate
Rock the plate for side to side to help agitation this will take about 15 minutes roughly.
Check the pcb periodical to see completion.
If you keep it in the ecthant to long everything will go and you will have failed the mission.
When the ecthing is finished wipe off the marker with alcohol.

Also dont throw away the echant it reusable and also damages the environment so dont do it .

At the end of the ecthing process the pcb should look like the picture below

Step 6: Soldering

At this point you plug in your soldering iron be sure to get it really hot.

Cut 2 sets of  25cm of wire, the metre left is for the input of the crossover.

Now get all of your components together, remember to place the transformer in the centre and place the higher  resistance end to the tweeters output. Now solder it in dont keep the solder melted to long that damages the flux so be quick when doing this.

Next the capacitors place the 2.2 uf capacitor parallel to the output lines of the loudspeaker, the 10uf capacitor is placed perpendular to the tweeters output. The loudspeakers output wires are coloured orange and black. The Tweeters output wires are coloured white and black.

 All that is left now are the input signal for the speakers mine are in the speaker box already and i soldered them on. 

Dont put up ur soldering iron just yet ! 

Sorry i couldnt be a little more specific beacuse the tags for the photos would work for me.

Step 7: Assembly

Find a good place in the box to place your crossover you screw it in or glue it with a glue gun.

The last step is to solder the appropriate wires to there respective places.
My orange and black wires went to the loudspeakers terminals, the black wire is used as ground and the speaker has to terminals posistive + and negative - , be sure to connect them correctly.
The tweeter is connected via the white and black terminals and black is also the ground.

The last thing i cant help you with and thats reassemblng your own speaker box  but thats something i'm sure u;ll be proud to do with out my help.

Plug it up to your set or amplifier and enjoy thanks for veiwing !

Step 8: Preveiw Audio Quality

Just a video showing how the speaker sounds
15W loudspeaker and 5W tweeter and off course i didnt have it pumping at max volume.
The bass is amazing for such a small speaker and the tweeter sounds crisp.

Please comment ......

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    9 Discussions


    2 years ago

    dumb question:

    what's the polarity of inputs and outputs?

    im too newbie at that stuffs :)

    2 is negative am i right?


    3 years ago

    Hi Josh!
    Im a ghanaian student in ghana(west africa) and your experties have actually attracted me. I have this problem. I want to connect leds to my speaker box so that the leds blink with sounds. Could you please give me the schematic and the components that i need. my contact is Thanks. Anybody who reads my message can assist me can also go ahead and help me. Thanks.

    What are the details of the low pass and high filters? I have no idea what they are and I can use some help in that department. I recently completed a TDA2030A stereo amp and I'd really like to be able to add something like this for increased audio performance. Thanks Josh.


    5 years ago on Introduction

    great work! congratulations!

    Would you mind sharing the specs for the transformer that you used ?




    Reply 5 years ago on Introduction

    Thanks broorb but to tell you the truth I can't remember the part no. on the transformer, but I can say you can find the transformer in an old crt television it will be identical to the one I have displayed, I think its properly good for about 25w rms


    6 years ago

    If I only wanted to make a low pass filter (with req. circuitry) and follow up by using the transformer and afterwards a logarithmic potentiometer to control my bass, would this work?


    Reply 6 years ago on Introduction

    Yes u can, just have place the pot in series with c2 and ground, I would go with no more than a 10kohm pot


    8 years ago on Introduction

    looks pretty good! im planning on building a 12v sound system and im gonna use something like this


    Reply 8 years ago on Introduction

    cool a good transformer does the trick