On equalising a small speaker so that it sounds correct to listener's brain

We know (i may be paraphrasing it) from Dr. Harry Olson experiments that octaves missing must be symentrical on both sides of the frequency spectrum for balanced sound,(Music, Physics and Engineering - Olson). On listening tests of the Pleiades Linoleum Auratone 5C speaker Vicky pointed out how well it sounds with grandma's Eleni JVC 9425W FM radio cassette recorder, which has an amplifier that bass boosts roughly below 100+ Hz to compensate for the somewhat small speaker, cabinet. Inside childhood's Sony DR-S5 8 ohm headphones was found a clever treble cut R, RC filter that is very similar to RIAA bass boost networks. It works as speaker bass boost and sounds great, see previous posts.