Yeah, I bought the wrong ones because I've got bad mold sensitivities. However, I was just a little lazy about changing filters and my motor burned out. I'm one of those that take a good 20x20 Lasko fan and put one of these behind it. I filled the corners to make it a ducted fan and the sound level drops WAY down. But having the 1000 Merv 11, I've got loads of airflow, just crazy amounts. The fan itself wasn't made to be ducted so the reduction in fine filtration made the airflow difference and will actually prevent this burnout from happening again, though I've only had it once. I think that was one of the water resistant motors which are closed. The open case motor is much cooler since air flows around the rotor and now it's getting more air in general. So I'm not getting as good filtration, in mold and tiny stuff, but since these fans aren't really made for pulling hard, even with my difficult to make duct, the 1000 is probably better in the long run. It blows really well on 1, so I will save some electricity and make my fans last a lot longer. These good Lasko fans aren't cheap. I had one last 25 years but it didn't have a filter behind it. I used it for a couple years with a filter and it seized an old dried up bearing. So I should have known that pulling air through filters with these heats things up and that will shorten the life, but it all connected when I got out my new filters and "Hey, It's sure blowing like crazy. No wonder. I got the 1000s." Now I remember making this decision on purpose for these very reasons, but before the motor burned out. So if there are others like me out there, I'd recommend the Merv 11, or 1000 because our fans will last longer. Maybe I just waited too long to change it. Well, that's possible. Maybe if you're better at changing filters, there's no problem with the 1550, but another plus with the 1000s is that they're cooler in the summer, blowing clean air at you from across the isle and on #1 setting. #2 is great and if I were to put the new motor into the ducted frame, the sound would pipe down. I guess it's like everything. How much time and how good is your back to make or reuse a ducted fan? I'll say this, If you want to make a ducted fan, get the pink or blue foam boards at Home depot. I found a purple piece of packaging foam and that cuts like butter. It's great to work with and sound absorbing. Don't use styrene foam, (brittle, crusty stuff). It's hard to deal with in every way. I wish there's someplace to buy these online. That makes it so much easier that it's not such a dreaded task at all. Anyway, Merv 11 will allow better air flow and that might help make up somewhat for the difference in filtration but I know the 1000s are not going to ruin a Lasko in 7 years. They'll last forever (essentially) on these Merv 11s. In this hot weather, I'm enjoying that better airflow. I also recommend the Lasko fan combo. Esp on these 1000s. They really keep the air in the house clean. I had my carpets cleaned and he said, "you're gonna have a lot of dust here on the AC inlet louvres. Well? (he tries again.) Huh. These are completely clean. Not a speck." He walks off mumbling "I don't know why it's so clean...". It's the Lasko/3m combination. It cleans SO MUCH air. I can go 2 years on a house filter and even then I don't see dust, I just assume it's there. It has to be. My inlet grates are spotless. Anyway, it really works and for so little money. I don't even bother to tape it up. The vacuum of the fan pulls it into the fan. That's the first thing I noticed. It barely pulled. That's the difference between the Merv 13 and Merv 11. It is a matter of preference ultimately, so try one of each. Keep the one you don't like because it's a lot better than nothing. (Unless you've got loads of money, I guess. I'm more of a waste not want not. It's not exactly true, but the saying has a point.) Anyway, I almost forgot. I prefer these filtretes over Filterbuy and others. They're sturdier and I believe they filter better, the MERV ratings being equal, the 3M is better made and it filters better, though I'll use a Filterbuy on the house system, for some reason. There's a frame around the house filter. So sturdiness isn't as important. These 20x20s for the Lasko fan are moved around, bumped into. They take the punishment and never get damaged. 3M really knows how to box these up, by the way. They're glued everywhere and it's very hard to open. Be careful.
