How’s the sound quality? 70’s Akai SW35 test

A pair of vintage Akai SW-35 speakers from my friend. Not much info online , a Japanese page shows simple spec: 1 Way full range bookshelf speaker 13cm Driver made by Fostex Frequency response : 40Hz~18Khz Power handling : 15W SPL : 96db @ 50cm Width 170x Height 430x Length 270mm 4Kg Some forum friends say this is back loaded horn , but looks like a transmission line to me. Hows the sound quality? you judge. Recorded using D300S DSLR, with WM-61A electret microphone capsule plug-in directly to DSLR. My workspace is too boomy, I should test it in sound room.