Mix and match subs?

Hello,
I have blended two totally different subs together with great success. This was talked about not to long ago. In fact you may want a sub that can reach down a little further. I am now running to JL Audio F110s with the JL Audio CR1 crossover and two REL T9s. MC and several others have a lot of good advice on setup. By going to 4 subs it made a huge difference in the bloom but also the sound blends across the whole room. The entire frequency, not just the bass. 

So 2 subs is definitely my max. Seems like there are differing opinions on to pair or mix and match. Seems to me a Paradigm x10 and x12 might work pretty well together. I would think in the frequencies where they overlap that they would blend well and the the x12 would take me down to 20hz. 
Or in the shared frequencies, would they not blend too well because they are different drivers?

Has anyone mixed subs with two driver sizes and had a bad result?

Seems like there are differing opinions on to pair or mix and match. 

Has anyone mixed subs with two driver sizes and had a bad result?

The majority of posters say mixing subs is not an issue.  I'm guessing that those are people (like me) that have actually done it.  I have two Rythmik F25 subs (2 X 15" drivers) and two SVS SB13 Ultra subs (13.5" drivers) and the result is very good!

I haven’t had any problems with my B&W and SVS subs. I don’t think it makes a difference in terms of subs. 

You can mix and match subs…but, you need to measure the in room frequency response at the listening position to see how the varied bass settings effect the sound. Ideally, something that gives you a visual to see in real time your settings as they change to help level out the curve. I use an old school Velodyne SMS-1 subwoofer Equalizer with a microphone and test tons to see in real time how all of the sub settings blend at the listening spot. I shared a link with my rudimentary measuring setup with a before measured response curve and after…note how much flatter it is after tweaking the settings. Not all flat curves are ideal, especially if you desire more bass and care a little less about microdetails. It is a personal choice, but it is important to eliminate as much drone, boom, and resonating bass which helps increase listening pleasure. 

https://www.amazon.com/photos/shared/I_6Rau1zQcOKOTfMsFSy1A.-ZXzEvmp6JEbBSJWepTMIw