Monday, 28 August 2017

Thorpy's Non-Technical Speaker Crossover Guide

Thorpy's Non-Technical Speaker Crossover Guide




Intro


There are plenty of guides around on the web showing how to build speaker crossovers.

However, I found most be a bit mathematical. You will need maths if you a building the perfect set of speakers, but for a functional set, you can use these rough instructions. They worked for me.

Crossovers are normally hidden inside a set of speakers and so unless you are building your own boom box, or set of speakers, you may never have seen one before.

I have taken some of the more simple advice on the web and dumbed it down still further, for those who want to see some pictures, and just have a go.

I have no clue how any of this works. But I have built a boom box, with the below components, some homemade / DIY, and it works. So I would urge you to have a go too.

What does a Crossover do?


If you look at most speakers they have two drivers, a tweeter for treble  (high pitch sound) and a larger driver for mid range and bass (low pitch sound).

What does a cross over do? Well it filters the sound and delivers high frequency sound only to the tweeter, and low frequency sound to the large driver.

Do you need a Crossover?


Sometimes no. Sometimes yes. Most speakers have some form of crossover. But how can you tell if you need one:

Example 1 - A crackly / distorted / snicky sounding tweeter may require a filter to get rid of the low pitch sound, that it is not designed to handle. In this case you would want to filter out low pitch sound, with a "high pass filter", which can be done with a capacitor (see below).

Example 2 - A harsh sounding mid / bass driver that is getting too much treble. In this case you would need to filter out the high pitch sound. This can be done with a "low pass filter", this is done with an induction loop.

What do you need to build a cross over?

Here is a picture of my setup. (I am sorry to say that the capacitor in this picture is covered with glue, so it is a little hard to see. But it is there! Click on the image to make it bigger)

Ugly but Functional


Ingredients - You will need:



  • Soldering Iron & Solder
  • Insulated Copper Wire 2 or 3 Meters
  • Bi-Polar Capacitor 40V +
  • Sticky Tape
  • Glue
  • Chunky Steel or Iron "Core for Inductor"*

*I used the spindle from a industrial motor, but you could use a bit of scaffold pipe, or a big bolt or a piece of broken round file. It has to be iron or steel.

Install a High Pass Filter (also called a "Bass Blocker")


A high pass filter is very easy to install, you will need a bi-polar capacitor.

Polarised or Bi-Polar


Now as a general rule you should choose a capacitor with a voltage above 40V, but the higher voltages will also work, although they offer no advantage. The "uf" can be anything you like, and will probably work OK. Search here.

Just solder the bi-polar capacitor between the positive amplifier output and the the positive terminal of the tweeter. The the tweeter should be "fed" power through the capacitor.

Top Tip: Do not look directly at the capacitor when you power up you system. It may explode if you have chosen the wrong voltage or type (polarised or bi-polar). If you look the other way the bits won't go in your eyes.

Install a Low Pass Filter (also called a "Treble Blocker)


To make your low pass filter (induction coil) take around 2 to 3 meters of door bell wire, or other single cored insulated wire, and wrap is around your chunky steel or iron core. Leave enough spare wire poking out so you have enough to solder it to where it needs to go.

An Induction Coil - Very Techncial

Power needs to be fed to you bass speaker through this coil. So you wire one end to the positive supply from the amplifier and the other to the positive terminal of the speaker. (Scroll back up to the labeled picture to see how)

Conclusion

As mentioned this will not get you a top notch speaker, but it will make a horrible sounding speaker sound OK. 

By example, before installing these DIY crossover coils, I had to have the equaliser on my iphone on bass booster, and the sound was still too harsh.

After installing I can switch the EQ off, and they sound well balanced, I used an induction coil (low pass filter) taken from a professionally made speaker for the left hand side, and my DIY induction coil (low pass filter) on the right hand side. I cannot tell any difference by listening between the speakers. So the homemade one is working it would seem. 

For Reference - This is a professional made induction coil. Note PAM8610 amplifier bottom Right.

For reference I am using a PAM8610 to run this portable speaker, from 7 x AA batteries. The speakers were taken from some low quality active speakers. Also I should point out that you can get a pretty good bluetooth speaker for £30 / $50. So do not spend too much money on this unless you are doing it for fun!

Inside my DIY Portable Speaker





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