I know RD is too humble to post this himself , but kudos for doing such a great job. These are measurements done by Purrin who dedicates many of his precious hours to further our interest and understanding .
These graphs tell us what we have always held true for these vintage orthos and it is a testament to many hours of fine tuning that we see such a flat frequency response.
congrats and thanks guys ..dB
What wonderful graphs, makes my heart all warm. The YH1 has the anisotropic driver, right? I remember there was a lively disussion as to its sound compared to the regular HP1 driver. Did you ever draw any conclusion, Wualta? The YH3 is similar to the HP3/HP50 and confirms what I'm hearing. Question is how much the termite housing influences the response.
About the magnets, I checked my HP1s, and also their serial numbers. Both are anisotropic.
HP1 from Germany 682645
HP1 from Sweden 120693
The serial numbers are probably encoded, for instance one digit for year, one for decade, one for model and the rest for number of headphones made. This is a common practice in manufacturing. Any former Yamaha employee reading this?