Tweeter Diffusers

Diffusers are quite common among tweeters and are used to smooth out the frequency response. I used to believe that anything in front of a speaker was bad, but i found out later this was not the case at all.

The problem

Just like any other speaker a dome tweeter isn't perfect, it will start to break up at some frequency.

The breakup sometimes results in a peak or/and dip in the tweeters response around 17kHz, however if you measure off axis the peak/dip might be gone. This is where a diffuser comes in.

How it works

I have to admit i do not know the actual maths behind a diffuser but in short it's a beam blocker. If you place a plate before the area affected the sound waves will have to move around the object smearing the total response of the tweeter.

All the tweeters i modified had a short waveguide, i believe the waveguide is needed to get the result you need.

Without Diffuser

With Diffuser

A side effect of a diffuser is that the energy becomes more focused and thus will reduce the total directivity (at certain frequencies). This can however also be an advantage if you have a room with a lot of hard materials and wish to reduce reflections.

Modifying a tweeter
If you want to equip your own tweeter with a diffuser, you must first determine the size needed. You can do this by measuring the tweeter on different axis, when you find the angle where the peak or dip becomes smoother you know the area you need to cover, simple.

The diffuser can be made from any material as long as it's hard and non magnetic. Metal is the fastest way to create the diffuser but not as well looking as black PVC (plastic).

If you choose metal you can follow my guide, you can use copper, brass or aluminum.

Things you need
Scissors	Chasing Hammer	Cork Sanding Block
Needle Files	Glass of Water	Micro Blowtorch
Nose Pliers	Contact Adhesive

Step 1
Heat your piece of copper/brass/aluminum with the mini blowtorch until it glows red (except for aluminum) and cool it down immediately in a glass of water.

Step 2

Hammer the metal on the cork sanding block with something round or a chasing hammer.

Step 3

Trim the hammered piece to the required size (see Modifying a tweeter) using the scissors whilst leaving the highest point of the bulge in the middle.

File the piece down with the needle files until it is round and does not have any sharp edges.

Step 4

Now we need something to hold the diffuser in place, the easiest way to do this is to use a piece of copper or brass wire as a bridge. Cut some wire about twice as long as the diaphragms diameter.

If you made the diffuser out of brass or copper you can solder the wire onto the diffuser, otherwise glue the wire in place with contact adhesive.

Step 5

Glue the diffuser onto the tweeter with contact adhesive. Place it as close as possible over the tweeters diaphragm (without creating a mechanical obstruction).

Finished!