I'm designing something in which sound plays a small but important role. The audio section's job is to emit a loud squawk at about 250Hz (with harmonics) in automated one-second bursts at irregular intervals. I'd like to put everything, including the speaker, in a compact box less than half the size of a shoe box (the smaller the better).
The speaker will be driven by a 1-watt built-in amplifier. Given the low power level, I need the speaker to have good efficiency in that frequency range. Sound quality is not important.
My question to the experts here is about the speaker. Do you think something like a 4"x2" unit, the kind used in TVs, will be up to the task? If desirable for better efficiency, I can raise the frequency to ~300Hz.
The speaker will be driven by a 1-watt built-in amplifier. Given the low power level, I need the speaker to have good efficiency in that frequency range. Sound quality is not important.
My question to the experts here is about the speaker. Do you think something like a 4"x2" unit, the kind used in TVs, will be up to the task? If desirable for better efficiency, I can raise the frequency to ~300Hz.
No, these are made for bandwidth, not efficiency. It's ofc possible to use them but is ~84dB enough?
One of the loudest full range is probably this Visaton. I'd build it with high Q enclosure with a port tuned to the fs, at 300Hz that would add probably ~4dB.
Since it should be small (how small?) the enclosure will likely not help with the baffle step, so you will lose 4dB or so, no matter which speaker you have.
You said 1W. How long/short is the interval between the pulses? If it's a few seconds, a buck converter and capacitor could maybe increase the power for a short burst by quite a lot and recharge before the next.
I think there might be a better way to do this though. Why don't you create the sound mechanically? A servo or motor can make a hell of a noise with 1W. Or a doorbell.
The sound is to be triggered by some event and the interval between pulses is variable and unpredictable - anything from 1 to 10 minutes.
I made something similar to this 16 years ago but I provided a line-level output for that one and it goes to a PA mixer in a studio. It's still in use.
I made something similar to this 16 years ago but I provided a line-level output for that one and it goes to a PA mixer in a studio. It's still in use.
Yes, there are lots of ways to make a louder sound. But experience tells me that the squarish-wave ~250Hz is very well suited for the purpose. It will also have a volume control. The product is intended for use in a small hall seating 50-300 people in a quiet environment. I think ~84dB should be enough. This one too will have a line out but I want it to be usable as a standalone unit.
Okay, then the most cheap FR drivers will do the job. The much cheaper Visaton R 10 S 4 Ohm (10 bucks) got a ferrite magnet and still makes 90dB, so you have a bit of a headroom. But with 84dB it doesn't matter much really.
Thanks for the replies and suggestions. I've been designing and building electronics stuff for over 506 years but am not an expert in the audio field.
I live in one of the most remote regions of a developing country. The problem has always been with sourcing raw materials. So I make it a point to use the most common, easily available parts in my designs. No modules unless absolutely unavoidable, no copying of other people's designs. Almost everything from basic components.
I live in one of the most remote regions of a developing country. The problem has always been with sourcing raw materials. So I make it a point to use the most common, easily available parts in my designs. No modules unless absolutely unavoidable, no copying of other people's designs. Almost everything from basic components.
