Usijng two different subwoofers

Depends on your goal. I go for bass impact in my home theater so I suspect mixing models or even brands might be fun there. However in my high end audio system I go for seamlessness of main speakers to subwoofer. I use a REL and tap the speaker outs, as REL suggests. The result is often spectacular and even funny. Turning on the subwoofer makes the system sound as if the main speakers just got better. Virtually everyone says "I don't hear the sub" until I turn it off! In my audio system, were I to add a second sub, I'd want the same make and model.
Art

Thank you all for your responses. I want to use this for a high end two channel system. The current subwoofer from B&W is no longer made thanks to the new modernized, 22nd century high tech look replacement versus the nice looking real cherry wood finish on my current old B&W 850 sub. I have not had any luck finding another one on this side of the pond, Germany.

That is why I posed the question; I am starting to realize that I must look at other brands. I crossover at 35hz right now.

Ciao,
Audioquest4life

I use an active PSB for centre chan. Custom enclosures with McIntosh 12 in. drivers driven by sub amp(and parametric eq)for front ch., and a PSB passive 2 ch. sub on rear ch. No issues at all. Surprisingly lots of low end info on rears and centre. Not boomy, tubby or loose low end. Verrry extended thanks to EQing.

Not only different brands but different generations, technology. Sounds great with music or movies. In the end, there is nothing like a test drive, as many well meaning people offer honest advice but your ears will make the final decision.

I will be able to test a drive a DD15 this weekend for a week and thus hope to find if I can match it with the system. Thanks all.

Ciao,
Audioquest4life

I agree that if you are searching for the BEST fidelity use the same brand and model. Different brands or models may yield very good results but in obtaining the best sound use matched models.