I made many refinements on the speaker to improve performance which I bought last week. The tester gave 8.1 ohms of impedance. I found it was a full range speaker by listening to various kinds of music. Tweeter mounted 1.5 micro oil capacitor made no difference in sound. I tried to listen to it without a tweeter.
I put the speaker unit into ALTEC type speaker box(for the unit of 20 cm) which I made before. It was fitted closely along with vertical line because the unit was ellipse shape .
This speaker seems to reproduce richer sound in comparison with ALTEC full range speaker(20cm). This is the greatest speaker with high cost performance which I have ever tried, but the price costs only JPY100 per unit. I decided to buy another one set. I fell sound sleep soon after I listened to it. I still try to improve its performance.