need some guidance for building a P.A. subwoofer

[sweetperfume]

Every loudspeaker has specific TS (Thiele Small) parameters.
Cabinets are designed for speakers with TS parameters falling within certain range, for instance, a driver with a Qts in the range of .3 to .8 is suited for a sealed enclosure, while a range of .18 to .7 is better for a ported enclosure. Other distinctions would be in general the cabinet port tuning (Fb) should not be much lower than the driver Fs. Horn loading puts more stress on a cone than bass reflex, requiring heavier cones, which require more magnet strength to control. The heavier cones reduce sensitivity, requiring more power for the same output, requiring better heat management to avoid power compression.

If you plug various driver's TS parameters into various cabinet designs using the Hornresp simulation program, you will see that certain drivers have a flatter response (less amplitude deviation) in a given design. Some cabinet designs are more tolerant of a wide variety of TS parameters, others require very specific parameters, a woofer designed for the specific cabinet.

Art

How to know about TS of specific speaker???

 

[m R g S r]

It was already stated that you should measure. (In order to see of you've reached your goals by building a custom driver)
One can go by manufacturers specs but sometimes they're off.

 

[tb46]

Hi m R g S r,

Sweetperfume is cooking his own, but needs some help measuring T/S parameters.

Hi sweetperfume,

Elliott Sound Products has a wealth of information, here is their T/S measuring page:

Measuring Loudspeaker Driver Parameters

Regards,

 

[sweetperfume]

Hi m R g S r,

Sweetperfume is cooking his own, but needs some help measuring T/S parameters.

Hi sweetperfume,

Elliott Sound Products has a wealth of information, here is their T/S measuring page:

Measuring Loudspeaker Driver Parameters

Regards,

Thank you for understanding. I will do the testing but it will take some time as i m out of the town for a month.
I have got to know many things and i need to learn way more than i know at this time. I hope to have u all by my side when i fell feel short at knowledge part.
Regards
Sabir Nadaf