I found a Yamaha Hi-Fi general brochure for that time period and it lists the NS-100M tiered below the NS-1000 and the NS-690III. Ir is described as follows:
NS-100M
3 way speaker system + True bookshelf size, yet with excellent sonic qualities + Tangential edge tweeter dome suspension + Midrange and tweeter level controls + Left/right speaker configuration + Single-sheet white cone woofer + Frequency response 50-20,000 Hz + Maximum input capacity 60 W + Sound pressure level 87 dB/W/m + Woofer: 20cm cone + midrange: 5.5cm soft dome + Tweeter: 3.5cm soft dome +_ Dimensions (HxWxD) 496 x 276 x 251 + Weight: 12Kg
Now, among my 100plus pairs of speakers, I have a NS-500 2/way speaker and I have seen this model in both 2/way and 3/way but have not seen any brochure or specs for these speakers. I also have the NS-1000 and these speakers are rather good and the only group of speakers made in Japan that can compete with our good domestic brands.
Your NS-100M should be a pleasant sounding speakers that are polite and do not shout at you... good for a row-M listener.
NS-100M
3 way speaker system + True bookshelf size, yet with excellent sonic qualities + Tangential edge tweeter dome suspension + Midrange and tweeter level controls + Left/right speaker configuration + Single-sheet white cone woofer + Frequency response 50-20,000 Hz + Maximum input capacity 60 W + Sound pressure level 87 dB/W/m + Woofer: 20cm cone + midrange: 5.5cm soft dome + Tweeter: 3.5cm soft dome +_ Dimensions (HxWxD) 496 x 276 x 251 + Weight: 12Kg
Now, among my 100plus pairs of speakers, I have a NS-500 2/way speaker and I have seen this model in both 2/way and 3/way but have not seen any brochure or specs for these speakers. I also have the NS-1000 and these speakers are rather good and the only group of speakers made in Japan that can compete with our good domestic brands.
Your NS-100M should be a pleasant sounding speakers that are polite and do not shout at you... good for a row-M listener.