Small Speaker Build

[timvan]

Hello people,

I'm working on a active noise control project. Currently need to design a speaker that can reproduce the sound within a train carriage. This is approximately 75dB at 70Hz to 50dB at 2kHz. So trying to build a speaker that will be placed at about ear level between 10cm and 50cm away from the subject.

The hope is to make the speaker as small as possible, approximately 1-2inch driver. I've been reading the Loudspeaker Cookbook however thought i'd ask see if anyone had any thoughts.

Thanks

 

[Cal Weldon]

Hi Timvan, You might want to take your question over into one of the speaker forums, to get an answer. This area is more about build than design. Good luck with it.

 

[sreten]

Hi,

There is a huge difference between 0.1m and 0.5m to
the ear, in terms of levels from a driver. And there is
a very good reason it currently only essentially works
for headphones up to a reasonable frequency.

Which is accurate level and phase correlation.

No way can a single driver noise cancel 2KHz
for two ears, your head is far too big.

You also have to consider whilst 75dB might
be the average level, the peaks will be
considerably more, real ambient sounds
have a crest factor way beyond recordings,
especially in the bass, which is very slugged.

rgds, sreten.

 

[timvan]

Thanks for the quick reply,

The system uses 4 speakers 2 on each side to create an area of noise cancellation. We're currently using two pairs of fairly cheap desktop speakers. One of each pair on each side. So looking to build 4 of these speakers.

However the rig is currently a mesh of duct tape and wires. Looking to design some small speakers to embed in a housing.

Desktop speakers are usually vented enclosures. When reading the loudspeaker cookbook, the design tables do not give values with Qts above 0.7.