And here is the data - below you will see dual 515 Altec in 817 on the top plot (the bottom plot is a bigger Altec cabinet).
You will see that your lose around 6dB from 100hz to 150hz compared to the 200-500hz region that it will extend to. It then goes off a cliff at 65hz. Please take note of x axis scaling - you lost 10dB from 60hz to 50hz.
So depending how full range you want to make your project (do you want 20, 30, or 40hz), you’ll need another channel below this or accept it as is or go for the 210A or 211 enclosures but they need a gigantic room.
Anyway - food for thoughts...

You will see that your lose around 6dB from 100hz to 150hz compared to the 200-500hz region that it will extend to. It then goes off a cliff at 65hz. Please take note of x axis scaling - you lost 10dB from 60hz to 50hz.
So depending how full range you want to make your project (do you want 20, 30, or 40hz), you’ll need another channel below this or accept it as is or go for the 210A or 211 enclosures but they need a gigantic room.
Anyway - food for thoughts...
