Project "The Drummer"-Flat DIY sub driver

[ZuMbAiU]

Hi guys!
Now I know what I want.When I can buy anything I can make it.
I want try use the flat cone design none the less that I don`t know anything about the prioritys and the shortcomings of this design.
In this thread I look for any information and any concrete result with this type driver.I have many questions,because my books are may be 20-30 years olds.I want to know how I can define the driver specifications like the frequency range,Fs,SPL,Vas,Qms,Qes,Qts,Xmax.
I know that this question isn`t very simple,but I haven`t any other choice.The facts for the moment: 2 voice coils x 2Ohms,solid rubber-surround,700W RMS power handling,18" aluminium basket,2 spiders,double aluminium flat cone.In the beginning I look for any info for this type design.If my project is wrong I wait for any advice.
Is necessary any help for the calculations of the dimensions of the basket,the voice coils,any help for the preliminary simulation of the driver...
For the moment the magnet is unknown ,because I don`t know from what old rubbish I can take it.I think that any old electric motor can be
suitable.I don`t know what type magnet I must search and wait for any help for this weighty choice.
The purpose of this project is : I want make sub driver(FS-500hZ) from any old rubbish.Will be great if this is possibly.