"JohnB" wrote in message

Hello experts!

I would like to run a cheap experiment. I will take a 10
or 12" subwoofer speaker, and wish to make it pulse from
0 - 20 Hz. I would like to do this relatively cheaply.

0 Hz is DC, an impractically low frequency for attempting to
reproduce audio. Think of it as raising the barometric
pressure in the room and keeping it there.

As a practical matter, 3-5 Hz are possible lower limits for
your experiment.

You want to do this experiment in a reasonably small room,
as that makes generating bass easier.

Needs:

1) Function generator - would be nice to have a digital
display, but not necessary. I see function generators
all over eBay. It seems I can buy anything that can
produce my desired frequency range. (?)

A low cost option - use the audio interface in your PC to
reproduce digitally-generated test signals.

2) Amplifier - I have NO idea what specifications I need
here. I just wish to make the speaker pulse at the low
frequencies. I would like a good pulse, a muddy
vibration would not be good. What do I need to look for,
what should my spec. concerns be?

You want an amplifier with good subsonic response. Many
common amplifiers are designed to roll-off response below 20
Hz.

3) Subwoofer - I would like something relatively
lightweight that I can easily hold in my hand. I'm
guessing that isn't an issue, as the cheaper the speaker,
the smaller the magnet, and the lighter it is.

Lightweight and low bass don't go together. Neither does
cheap.

4) Connectors - I see function generators tend to have
BNC outputs. do I look for BNC to RCA connectors at
Radioshack?

They have 'em.

How should I connect the generator to the amp?

If you're really fixed on that function generatgor, use
regular shielded cable. Use a regular audio cable with a
BNC-to-RCA adaptor.