My bedroom started looking like that somewhat later in the mid 1980s, kicked off by the winning of some car speakers in a primary school raffle. This inevitably raised the question of what to plug them into. Collecting discarded junk from the 1960s-1970s at jumble sales and car boot sales solved that problem and I learned a lot.
I think that I was privileged to have had a childhood in the age of ubiquitous junk availability. It kept me off the streets and lead to a technical profession and some life long interests. It’s actually more difficult to get hold of stuff now thanks to electrical safety regulations, skips being locked, eBay pushing the prices of trash up and general lack of repairability of anything.
A footnote: 30 years later my bedroom is a radio shack and just as messy and I’m blessed that I found someone understanding enough to put up with it :)