Size box for my Dali Phantom 7" with limited specs.

Hi all this is my first post I spent all last week making some speakers and have just uncovered these Dali Phantom 7" woofers I had in storage. I'd love to use these In conjunction with with my new 6.5"SB acoustics SB17NRXC35-8 speakers (will separate the Dali 7" and SB 6.5" with divider in speaker box to simplify my calculations)

Problem is there are no specification sheet for the Dali 7" woofer on the internet which makes it near impossible for a novice like me to try and incorporate them my DIY ported cabinets. I have a spare 50 litres available space in each cabinet for them and was thinking I'd only need 20 or 30 litres of that for a Dali 7"

The only info I have is the Dali 7" were used in M-375 in wall speakers with two passive radiators. Here is the cutout size of it
29.6" x 8.9" x 3.9"

The inside cone volume which I measure this morning is 350 ml equals 360 cubic cm volume. The 2 passive radiators in each enclosure should measure the same which comes to 720 cubic cm which converts to same for port volume.

Is anyone able to close approximate what size port and enclosure I need. I'm thinking 20 to 25 litres and a port size 6.3 x 23 cm. But this is only a rough guess based on rudimentary calculations any help appreciated.
Regards Tim

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Thankyou much appreciated, do you mean 2 ports between 2 to 3 inches round?

Here are my half finished speaker cabinets, the speakers are a long way into the box (30mm) to give some protection as my two lorekeets fly around the house and do droppings on them I'm hoping this 30 mm edge will not effect the sound quality.
Tim
 

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