Controlling a Subwoofer

Hi! I want to use an arduino to control a subwoofer, but I'm not sure how to go about it. I need to make the subwoofer play a series of low-frequency tones, below the range of human hearing. The smallest subwoofer I could find is rated for 25 watts, so it seems I'll need to amplify the pwm output quite a lot. Anyone know what sort of amplifier I would need to use, or if there is a shield or something I could use? I looked at the wave shield, but since it only outputs 8 watts and I don't want to play .wav files, it doesn't seem particularly useful.

The catch is, this whole setup needs to battery-powered and small/light enough to wear on your back. I'm not sure that's possible with these sorts of components; if not, I'm going need a new idea.

Thanks!

subwoofer...play..low-frequency tones, below the range of human hearing

and

battery-powered and small/light enough to wear on your back

Are, in my experience, mutually exclusive. Subs are incredibly ineffecient without some form of resonator, and at these frequencies, that's a very long tube, even if you fold it up like Bose.

At the threshold of normal human hearing, 16Hz, your wavelength is something like 20 metres - even a quarter wavelength resonator is going to be 5 metres long.

You will definitely need an amplifier to drive any sort of a speaker from an arduino. If you want to play tones below the range of human hearing, you’re going to need large, large subwoofers, and a lot of power. Even at the low end of human hearing (~20Hz) it takes tremendous amounts of power to be able to ‘feel’ the bass.

Also note, dumping PWM into an amplifier/speaker setup can damage the speaker, as they were designed for sine waves not square waves (peak and dip of each wave with PWM is basically + and - DC across the coil, often times resulting in smoke :wink: ) Most of the time if you’re doing low power stuff it won’t really matter, but if you’re actually looking to reproduce frequencies <20Hz, there will be DC on the coil for a long time, probably resulting in smoking the coil.

Any chance this is a ‘brown noise’ project? ;D

Here is the speaker I was looking at - I wasn't allowed to include a link in my first post. Hopefully someone will understand the specs better than me. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-877

I am trying to use it to provide tactile feedback. I tried using vibrating pager motors before, but they don't have a large enough range of intensity or frequency. I'm hoping you would be able to feel changes in the amplitude and frequency of the tone from the subwoofer, and that it would be able to convey a value. From what you guys have said, it doesn't look too promising.

If you're looking for some sort of vibration to feel, definitely go with vibrating motors, think of the dual shock controllers for a playstation. Varying weights/speeds can give you different feels. A 3" "subwoofer" isn't going to produce really anything that's below hearing threshold, especially since its -3db freq is 65Hz.

I'd go look for some used dual shock controllers if I were you, or these are cheap: http://www.allelectronics.com/make-a-store/item/DCM-344/VIBRATOR-MOTOR/1.html

Couldn't you just make a modulator out of a 555, that would drive a servo?

What you want is what is known as a "bass shaker"; Aura makes a few cheapo ones (there are more expensive ones made by other manufacturers); ask around at your local vehicle audio shop if you have one, otherwise do some research.

Aura used to manufacture and sell a device called the "Aura Interactor" for use on the Nintendo NEW and Sega Genesis (among others) game consoles. It was a vest you wore that had a bass shaker in it, plus an amplifier, and you plugged it into an audio source.

Regardless of how you set it up, you need to have the bass shaker tight against the body for you to really feel it (a problem with the Interactor - most people didn't strap it on properly, like the piece of s&m gear it was - LOL); most bass shakers used in car audio (and home audio - you know, to rumble the couch) are attached with bolts to whatever surface they are to shake. Driven hard enough, they can cause minor damage (or at least loosen some stuff up!).

The biggest problems with bass shakers, though, will be power requirements; this won't be a portable system. If you are ok with being tethered to a power supply, though, then bass shakers will meet your goals, I think.

:)