I did not hear 1801b but simulation of the box volume rises a question about midbass endurance. Cone excursion goes over allowed region, even at low amp power:
Compared to what other driver?
Approximately how many watts/volts are actually needed to produce decent SPL with your current speakers? This should be measured at the speaker terminals.
Except distortion, this may cause quick weariness of the driver. Can you please comment it?
What do you mean... "except distortion"? Do you infer the driver might wear-out?
Also, I wonder why you do not use a bit stronger/better Excel driver: W18EX001 0017, instead of W18E?
Exactly in what way are these drivers stronger/better? Alternately do these drivers sacrifice anything compared to the W18E001?
However, it would have the same (theoretical) problem with cone peak.
Is it possible to have a truly stiff/pistonic cone without the cone peak?
You ask some very good questions that I could address in 2-3 pages of text, but I'd rather narrow your questions and save some of my time at the keyboard. It appears your questions have some educational basis. This is great! They are very solid questions that I was asking about 6 years ago.
