Problem
- Plaster of Paris is setting too fast for big speaker
- search for new POP type which have slower settings time.
- Change to other type of cement
- Back cover is hard to assemble and has many more problem
- May be I can build a speaker without a back cover
- Use some kind of plastic report cover to cover the cement surface make the surface vary smooth
- From Loudness, the frequency below 100Hz is quite steep, may be it’s better to invest in frequency around 50-60 Hz more than frequency below 50 Hz
- already tried tuning frequency flat down to 40Hz, the frequency below 50 Hz is hard to hear.
Realization
- My effective hearing range is around 60 - 15000 Hz
- with the same volume of 60 Hz, at 40 - 50 Hz I can hear very low.