My new slightly quieter Corsi-Rosenthal box

Here is the TL:DR - I made a new Corsi-Rosenthal box with a disassembled pedestal fan that is 5 decibels quieter than my old Corsi-Rosenthal box made with a box fan.

This summer, I noticed that our pedestal fan was a lot quieter than the box fan mounted onto our Corsi-Rosenthal box. Louder enough to make a difference to a guy like me with a certain amount of hearing loss who wants to hear his visitors when they speak.

It occurred to me to see if I can get a quieter fan for my next box. I knew I'd be making a new box before long because the filters have to be replaced every few months.

So I went on line to find a quiet box fan. I actually found a couple of sites that said certain box fans were quieter than others and ordered one that was supposed to be quiet. But it was not. In fact, it was louder than the box fan I already had.

Next, I thought about disassembling our pedestal fan and using it.

But then I thought a little more and it occurred to me that the other resident here might not be pleased if I disassembled her pedestal fan even for such a good cause.

I did some looking. There were people selling pedestal fans for $10 on Facebook Marketplace, but I did not fancy the idea of driving to somebody's house, asking them to plug in the fan and then maybe driving away empty-handed if the fan didn't work or was louder than I liked.

So then I looked at the Belfast Road ReStore and the Cyrville Road Value Village. The ReStore had a pedestal fan that worked but seemed a bit noisy. Value Village had a $20 pedestal fan that didn't seem too noisy. And guess what. It was Tuesday, Senior Discount Day so 30% off!

I used five 20" x 20" filters for my first two Corsi-Rosenthal boxes. This meant I had to build a frame to raise the bottom filter off the floor. A worthwhile thing to do, but it was finicky.

It occurred to me that having the Corsi-Rosenthal box made from four 20" x 25" filters would give the same surface area of filters as five 20" x 20" filters but no frame would be required. (The old math classes came in handy. Check it out: 4 * 20 * 25 = 5 * 20 * 20!)

So I searched the local hardware stores' websites and Amazon, determined that Canadian Tire surprisingly had the best deal and ordered four 20" x 25" x 1" Merv 13 filters. I don't know why, but Canadian Tire gave me free same-day delivery.

These are the steps I took in making the new Corsi-Rosenthal box:

1. Disassembled the pedestal fan and reassembled it with the rotating mechanism removed and the power cord lengthened between the fan and the control box by about 12" with wire I've had hanging around and Wagu clips to connect the wires. (This is my first time using Wagu clips and I love them. They make joining wires incredibly easy. It might seem like $0.50 per join is a lot compared to a bit of solder and shrink wrap, but the time and effort saved is worth every penny. Plus, I'm not very good at soldering, so there's a high chance that my splices would fail.)
   
2. Cut a sheet of fibreboard I had in the basement into two 21"x 21" squares.
3. Cut a circle that was the size of the round fan grill into the square for the top to make a cowling.
4. Drilled eight little holes around the circle to attach the fan grill, and a bigger hole on the side of the circle for the fan's power cord to come out.
5. Drilled two holes 4" apart in two opposite corners for rope handles.
6. Took two pieces of 12" cord, threaded them through the holes in the corners and tied knots so they'd stay in place to make the rope handles.
   
7. Mounted the fan head in the cowling, attaching it with twisted binder wire and taping it down with duct tape. Making sure that the power cord came out through its hole.
   
8. Duct taped the filters together to form a box, being sure to orient the filters so that the arrows indicating the air flow direction pointed into the box.
9. Duct taped the fibreboard for the base onto the bottom of the box.
10. Placed four fuzzy floor protectors in the corners of the base and one in its middle.
11. Found a little box to put the Wagu connectors and wire that led into the control bar for the fan.
12. Painted the box black, cut holes for power wires and for a piece of cord to hang the control bar from. Put the stuff inside the box, duct taped the box to the cowling, hung the control bar from the box and put the lid on the little box.
    
13. Plugged in the fan and turned it on.
    

After trying the new Corsi-Rosenthal box, I realized that it still made some noise. That's when it occurred to me to download an app to measure how loud it is. I went with one called SPL Sound Meter. It was free and had a good rating.

According to the app, the new Corsi-Rosenthal box is 50 decibels loud at top speed and the old Corsi-Rosenthal box is 55 decibels at top speed.

I'm okay with that. And next time I'm in a Value Village, I'm going to see if they have an even quieter pedestal fan.