As you stated, "it is a copy of the D&B B2 subwoofer" so, the characteristics will be different.
Here's a tip about speaker building. Unless you are using the same speaker (Model Number) and can guarantee the dimensions are exactly as the original, it is a replica. It may look like the original but, it will never perform like the original.
If you designed that box using a sheet of paper (blueprint) with only the cabinet dimensions, your guess is no better than anyone else on the impedance plot. All speaker enclosures alter the impedance curve of the driver based on frequency when sitting in the box. Whether it be Band pass, Horn, Reflex, and/or Sealed. There are no exceptions to the rule. However, you need the tools to determine what it is.
What ever program you used to build that design should offer the tools to help you determine the end result in terms of performance; Impedance, Maximum Acoustic, Maximum Electrical, Phase, Group Delay, and, Cone Displacement.
Those that are familiar with enclosure design create their own and, base it on their requirements. Those that copy designs from manufactures cannot expect the same results, when they are using substitute parts from the original. One shouldn’t use the technical specs of the manufacture as a guideline because they are using a replication of the original. Can you guarantee the woofer you are using in your D&B B2 Replica is the same woofer housed in the D&B B2 in terms of TS Parameters?
If you are familiar with EBP, and, impedance curves, I don't see why you would build a replica when you seem capable of building your own design. That’s how you learn the fundamentals of cabinet design.
Best Regards,