Thanks a lot for your answer. You just know it all!

McBeans program actually display impedance based on the T/S parameters of the driver(s)and the actual horn, of course, so I hope I can use these program facilities as a rule of thump.

However, the program displays both Acoustical and Electrical impedance.

Question 1:
Please correct me if I am wrong, but is it the Electrical impedance you refer to in your reply?

If it is the Electrical impedance you refer to, then I would like to know how critical 'reactance annulling' is soundwise (Unfortunately, I have already ordered the cabinets that might be too small, so it may be an expensive lesson - at least to me!).

The cabinets ordered have a back chamber volume of 120 liters, which gives an Electrical impedance peak at about 32 Hz, while the Fc = 29.11 Hz. According to your answer, this indicates that the cabinet is too small!!

With your added knowledge I have now been changing the numbers in the program, and these simulations indicate that I have to increase the back chamber volume to 160 liter in order to push the electrical impedance peak from 32 Hz down to 29 Hz.

Question 2:
Would such a change (pushing the impedance peak from 32 Hz to 29 Hz )make a large difference soundwise?

I thank you a lot in anticipation and look forward to hear your answer!

Regards
Peter Krojgaard