Improve the sound of your helmet loudspeaker

Upon testing my Bluetooth set up, people often comment about the sound quality in my helmet, and wonder why it is so much better than what they get from their own equipment.

I have made some simple modifications that I am happy to share with you. 

There is much to be said about loudspeakers and sonic quality, but let me start with some basics.

When the loudspeaker membrane is pushing forward to produce sound—this creates under-pressure on the backside of the membrane. The surrounding overpressure will seek to level out this pressure difference by filling the void on the back. Because of this, the sound is not travelling with its full effect to your ear; and you loose out on sound level (and quality). However, it is easy to fit a your own custom made resonator chamber, that will help directing/forcing the sound to your ear.

	The picture shows a normal helmet loudspeaker. The backside shows the black ring on the outer perimeter; this is where the overpressure flows to level out the under-pressure on the backside of the membrane.
	I use a highly compressed (dense) fabric—that is normally used as a dampening material for screening noise from computers—to be very efficient for this purpose. It has an adhesive (glue) on one side.
	Cut out two rings—both with an inner diameter the same size as that of the loudspeaker.
	Fit the rings on the front (ear facing) side of the loudspeakers.
	Than make a new set of rings, and cut two small openings on either sides.
	Glue the two sides of rings to each other, making the assembly the same height as the loudspeaker.
	This is from the backside — where you can see the two openings in the lower/back side ring.

And that is it!

You will need to find the right size of the openings; they will decide whether it works as intended and give you the best sonic quality. Keep trying until you find the optimum for your speakers and helmet.

Then fit the whole assembly back in the helmet.
You should take care to do this as accurately as possible—a few mm off means a lot for the sound.

Test it, that's the only way to get it just right.

Regards

STeinar