Getting 2 subs

The G&R Research has gotten me very interested in open baffle subs. They make single, double and triple kits with servo amplifiers for full control of each woofer. They include all the cnc cut material for diy assembly. Supposedly, with open baffle, it pressurizes the room equally, thereby giving a more even response without the “room boom”.

One more suggestion for integration, have two matched pairs of subs: Tower Kinergetics SW-800 and two SVS SB-16 Ultras and measure the room with Room EQ Wizard and plug those measurements into Multi Sub Optimizer to get my 12 biquads on each speaker for the DSP. The integration is amazing and also keeps the neighbors from complaining. They are all not set up symmetrically as others have mentioned to help with the room modes. The subs run full range and cut off based on their abilities and crossovers from MSO. It’s a dream set up, good luck and let us know what works for you! 
 

- Steve

so is it ok to get 2 different size subs to cover a wider spectrum of bass or get 2 matching subs?

To directly answer your question rather than blathering on about unrelated matters: Yes it's OK. The brand does not have to match nor the size. I have used subs as small as 6.5" with great results.

What you might consider is getting 3 or 4 subs which will go further in smoothing out the room response and when implemented well provides an astonishing result.

In a similar thread here:  "Subwoofers ported or sealed" audiokinesis mentions his system and is worth looking into. Check out his SWARM.

My advice is to not be in a hurry, do your due diligence, read up on the concept of multi-subs as researched and advocated by dignitaries such as Geddes, Toole and Welti.   They have all researched deep into the how, why and the spectacular results thereof. Their findings carry more weight than some posters here who do not have a clue.

There was a great thread a few years ago about matching 1 or 2 subs with large floor standers (actually B&W)...Audiokinesis talked about using 2 subs and thinking of the main speakers as subs...when I bought a second sub, Duke, of Audiokinesis, (when he was active on these threads), was incredibly gracious with sharing his expertise and advice on set up...asymmetric was the key...