Posts tagged Acoustics

Photo Diary: Building the QD-23 Diffuser by Acoustic Fields

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Building a QD-23 by Acoustic Fields

Without a doubt, the most time-intensive project to improve my composing studio has been a DiY build of Acoustic Fields’ QD-23. The QD-23 is a massive acoustic diffuser that evenly diffuses all frequencies from 185 Hz to 3.45 Khz. It was totally worth all the pain and difficulties because it sounds dope in my studio, now.

Why on earth did I attempt to build this damned thing? Three reasons.

Reason #1: Acoustics in recording studios are crucial. Taking care to shape the acoustics of a room allows me to feel reasonably confident that a mix will travel well (meaning, it’ll sound good on a lot of different systems). Proper acoustics also ensures a far better chance at clarity and balance.

Reason #2: Diffusion, in general, helps to scatter sound waves evenly throughout a space. The QD-23 works really well when it’s placed behind the person doing the mixing, like on the back wall. I knew that it would allow a deeper, more 3D richness in sound.

Reason #3: I talked my Uncle into helping me with the build. Seeing as how he’s a far better woodworker than I will ever be, I was both shocked and delighted he agreed to help me out.

The process was intense. I knew that I wanted to remember this for the rest of my life, so I kept a photo diary of the process. I’ve published a couple of blogs about this project already, Day 1 and Day 2, but I’ve condenced the entire project onto this blog post so you can see the entire thing, start to finish.

Let’s go!

Day 1

Goal: Cut all wood to the sizes required by the build plans.

Day 2-4

Goal: Stain the wood. I have fewer photos of this part of the process because getting my phone out to take pictures was incredibly difficult with rubber gloves and stain everywhere. The colors did turn out quite pretty:

Day 5-6

Goal: Mark the wood for the wells. Not sure what a well is? You’ll see later in the post.

Day 7

Goal: Get the wells routed out and ready for the slats. My Uncle managed to create a jig for the router so that we could get the work done quicker.

Day 8

Goal: Get sides and wells glued into place. This was really fun to do:

Day 9-10

Goal: Get tops on.

Day 11

Goal: Configure the well depths. See the hammer? My Uncle called that his “Persuader.”

Day 12

Goal: Start placing the wells. Each of them was configured to go to different depths. Notice the gnarly things we needed to do to each slat to make sure that it stuck together…

Day 13

Goal: Do a little framing, make a stand, install in studio, be happy!

Creative ProductivityDave WirthMarch 20, 2025Acoustics, recording studio Comments

Day 2: Quadratic Residue Diffuser Build

Slowly but surely, the Acoustic Fields’ QD23 is coming closer to completion. While our job before was to create rough and therefore imprecise cuts, today’s work was centered around cutting the wood exactly to fit. If there’s one thing I can say about this process, I’ve got mad respect for both professional and amateur woodworkers. The precision, the craft, the dedication? Upwards.

Earlier this week I called in an order to Austin Fine Lumber and Plywood. For the price of the wood plus a cut fee, this was what they gave me. The scrap are the long pieces, but the shorter ones are for the top and the bottoms of the diffuser. I picked up the wood on Wednesday.

A close up of the tops and bottoms of the diffuser. After dealing with Austin Fine Lumber and Plywood, there’s no doubt I’ll probably have them cut all the wood upfront for me. It’ll be more expensive, but that would leave me with the fun part: Assembling.

We needed to create this setup to cut multiple pieces at once. The next pictures show how.

Using a square to line up the corners.

A little bit of adjusting to make sure of a tight fit.

Here, we’ve got it. All good!

This is the rough edge. See how there are multiple pieces of wood? Yeah. We measured the length we needed on both sides and then put a square on that line to safely guide the hand saw.

Here is the result of the custom jig: All of the wood is cut exactly to the correct lengths.

Up close shot of the well dividers.

Our next job was to cut the well pieces exactly to fit. One edge was the factory edge, and the other was our rough. We had to line them all up with the factory edge to get a perfectly straight line. Then, we could get an exact cut on the mitre saw.

My friend measured out one of the pieces so that we could repeat the task with accuracy, quickly.

All of our pieces are ready! The thick pieces toward the back are the sides and the back of the diffuser. The thin pieces are the dividers. The really narrow but thick pieces in the front will be placed in between the dividers at specific depths.

All the wood that’s fit to print. Enroute to my studio, with a stop at a Texas BBQ joint first (of course).

What’s Next?

Now that all the wood is cut exactly to where we want it to be, I now have to consider staining. It’s looking like it’ll be a bit rainy for the next couple of days, so I’m refusing to think about it for now. However, I’m going to have that done hopefully at some point soon.

After the staining, we’ll cut each dado, and then assemble this wonderful diffuser.

Stay tuned for more details…

Dave WirthApril 5, 2019Acoustics, DiY

Day 1: Quadratic Residue Diffuser Build

I have long wished to build my own quadratic residue diffuser for my humble studio. Today was the first day of the process! I’ll be posting more details as things progress.

A big concern of mine is bang for the buck. More than anything, I wanted to find a design that was put through a battery of scientific tests before I shelled out my money on it. I’m very suspicious of anyone writing a review on just about any acoustic product website that says: “it sounds awesome, buy it.” I needed more assurance than that! I wanted a diffuser that the company took the time and tested in an anechoic chamber with well-calibrated equipment and a scientific process. After tons of research on companies that offer acoustic diffusion products, I settled on Acoustic Fields’ QD23:

Acoustic Fields can send you a QD23, but if you have a DIY spirit, you can also purchase the build plans on their website and build it yourself. I previously bought some other products from Acoustic Fields, and I can’t say enough positive things about them.

After purchasing the build plans for the diffuser and paying my friend from AMBO Guitars (a superior woodworker) to help me with the build, today was the first day we jumped in. We purchased the wood from Austin Fine Lumber and Plywood in North Austin. Our goal today was to cut the pieces we’d need to assemble. Here’s the progression:

Starting the cuts with one huge 4’x8’ piece. This one was the scariest because we had to cut the backs out of just one huge piece.

We started to get some rain, so we covered up the wood and took a coffee break. There was lots of swearing.

With our big cuts done, we ripped the pieces in half for the backs and sides. Unfortunately, we needed one extra sheet. Oh darn. I have to go back to Austin Fine Lumber…

Quadratic residue diffusers have different well depths. We needed to cut the alder into thinner pieces. When we assemble the final piece, each of these will be placed at specific depths within the diffuser.

A little saw action…

Each of the wells is separated by one of these panels. We had a ton of these to cut. Our first job was to do a rough cut before we jumped into the precision cuts. It’ll make the wood more manageable to cut into pieces where we had the exact size we needed.

Clamping all of these boards together made it possible to do just one single rough cut.

The rough cut happens!

We have our cuts for the well dividers! Yeah!

Aside from the tops and bottoms of the QRD, we have just about everything else we need.

Coming Up Next…

My job this week is to get some more wood from Austin Fine Lumber and Plywood, purchase wood screws, and purchase the stain I would like to use.

More to come… stay tuned.

Dave WirthMarch 30, 2019AcousticsComment

Absorbing Sound Reflection From Side Walls in a Rectangular Room

I've been working to make my existing mixing setup sound good acoustically rather than getting new pieces of gear. So, I decided to take it upon myself and construct my own sound panels for the side walls of my room:

The first thing I wanted to do was absorb the upper mid and high frequencies that reflect off the side walls. Why the side walls? The music I'm listening to from my monitors goes straight to my ears but when the side walls don't have any absorbtion, the direct sound gets combined with the reflections. As you might be able to guess, my monitoring room is a rectangle, which is exactly what you don't want. This reflection can color mixes negatively, so I started treating the side walls with some old Auralex foam panels, some cedar slats, partical board, and some glue.

Here's the general progression of how I put these together