Why is this crashing?

I know you posted this a few days ago, so perhaps you've already answered the question yourself, but if you haven't, the problem is the speaker cable. It's pinched, frayed, or may even have a tiny tear in it. You can fix it yourself, but it's certainly one of the more irritating repairs to do, so you may want to have a professional do it.

The nice thing about doing it yourself though is that it's actually very cheap. You can buy just the ribbon cable itself and reuse your original speakers to save money, rather than buying the cable with new speakers already soldered on. One bit of advice though is that if you buy a third-party speaker cable from eBay you should buy two just to be safe. Sometimes they're faulty straight from the factory. If you buy an original cable taken from another 3DS console though it should be fine to get just one, since the seller should have tested it.

Here's the guide: Nintendo 3DS Lautsprechereinheit austauschen