building a 412 with a couple of eminence beta and bp122?

[Simojam]

what do you think about this solution? it will be 8 ohm of final impedance and with two separate room. My idea is to have the bass part from the bp122 and the top end from the beta! 
let me know

[Jus Lukin]

-

Edited February 25, 2022 by Jus Lukin

[Bill Fitzmaurice]

Using a midrange driver with a BP122 isn't a bad idea, using a Beta 12 as a midrange driver is a very bad idea. It's not about response, it's about dispersion, and the midrange/HF dispersion of a twelve is horrid. That's why guitar cabs beam. The right tool for the job is a six or an eight.

[Phil Starr]

It depends upon what you are trying to do, if you already own these speakers and are just curious then you'll end up with a working speaker, you'll have learned something and had some fun. If you have to buy these speakers then probably give it a miss. This is not a marriage made in heaven. The first thing is that the speakers have different sensitivities with the Beta being 2-3dB louder than the BP122 so they will dominate the sound. Secondly get the two frequency plots up on screen, all the lumps and bumps above 500Hz are what give the speakers their 'sound'. Where they line up the effect will be additive but few of the bumps line up exactly and what you will get is a smoothed out response. Add in the beaming Bill mentions and it's likely to be a dull sounding speaker though dominated by the Betas. Even if you already own the speakers I'd be tempted to build two 2x12's. That gives you the option of using them together, either cab separately and also as a stereo set up. Together you can use them as a vertical stack which gives better dispersal but if you want to investigate using them side by side as in a traditional 4x12 then that's an option too. 

If you don't already own the speakers then I'd go for four Betas.

[Simojam]

Actually I know that the betas are more sensitive, but obviously they are not so good in the low frequencies! I can mix them because of the strongness and the lows of the bp122! A 412 with the betas Would not fit my tastes because I have already made a sealed 212 with them and I wasn’t sodisfied!

[Bill Fitzmaurice]

12 minutes ago, Simojam said:

Actually I know that the betas are more sensitive, but obviously they are not so good in the low frequencies!

That's not true. In the same 2 cu ft ported cab tuned to 45Hz or in 2 cu ft sealed the Beta 12 and BP122 have virtually identical low frequency response. Neither will have very good low frequency sensitivity in a sealed cab, because it's a sealed cab.