I have recently "inherited" a 2003 Philips sound system with fairly decent compact speakers.
The specifications in the manual do not appear to state whether the speakers are magnetically shielded. Is there any simple way to find out?
Put them next to a CRT TV or computer screen. It's not a very high tech way to find out, but it's sure to change the image if they are not. Don't leave them there for long as they could damage your screen. You could also open them up and check visually. If you see bare magnet, they are not shielded. Then again, they could just be painted over.
Either method is not sure. Also the sheilding may not very good but provide some degree of shielding. So even thought the manufacturer may state they are shielded, they might not be shielded very well at all.
If you are really concerned and you don't trust the manuafacturer, you may want to use a gauss meter. I found this page: http://www.coolmagnetman.com/magmeter.htm