Pros and Cons or don't do for Quad subs
Have two ported subs EP350
going to go for four but wondering if it is wise to mix say two ported and two sealed.
or just go all sealed.
One of the posters here combined two Axiom DSP subs with two SVS cylinder subs, to give a blend of good frequency response with highest output/$$. The result was the best HT system I ever heard, so definitely not a bad idea.
My first thought would be to reword the question as mixing DSP with non-DSP subs, although ported subs can (depending on configuration) have the advantage of generating bass output from two different locations for slightly smoother room interaction. EP350 ports are fairly close to the driver so you probably won't get much of that effect though.
Personally I would just add two of whatever sub appealed to me the most and make sure the levels were set so that all subs hit their limits at approximately the same time.
For what it's worth, I'm running an SVS PC+ 20-39 (which I bought back when EP350 was Axiom's top of the line) and an EP500.
I've read different things online about this as I too toyed with mixing ported with sealed subs.
I think that the big "gotcha" is that it is harder, a lot harder, to tune subs to the room to begin with. I am not talking about the subwoofer crawl because that pretty much goes away if you can get each of the 4 subs in the middle of each of the 4 walls.
I am talking about your receiver or processor. It will have to adjust itself to the combined output of each sub, and with different capabilities, you may have 1 or 2 subs playing one frequency great, and the others getting boomy.
I just went through a room correction setup about 2 months ago where I had to adjust 1 sub at a time until I got it dialed in as best as possible, and then shut it off and went to the next sub, and then turned them both on and went at it again.
Luckily for me, the subs performed pretty much identically (one SVS and the other a DIY virtual "clone" of the SVS), but it still took a solid 90 minutes of tinkering around. Then again, my 2 subs are both up front by the main speakers, so I would notice distinct variations just by moving a sub just a couple of inches sometimes, or if I tinkered with the phase a little.
Again, I think that it can be done, but you might actually be sacrificing the capability of one type/model so that you aren't "over-pushing" the other. I know that it seems like "hey, I will get the best of both worlds" which is true, but you will also get "the worst of both worlds" if you want to keep the LFE and bass clean and not boomy.