Designer:

Colonel7

Project Category:

Bookshelf Speakers

Project Level:

Intermediate

Project Time:

8-20 Hours

Project Cost:

$100-$500

Project Description:

I wanted to try out coaxials and thought a nearfield monitor set-up for work and music listening would work well and it has so far. These are called the Impastos because I used artist impasto (adds texture to paint) mixed with black floor paint and applied with a foam roller to give it a textured surface – kind of like a DIY Duratex.

Design Goals:

I work from home and needed higher quality desk speakers for both meetings and music listening in my office. I wanted good quality sound in small cabinets that would also sound good if I sat in a reading chair to relax without adjusting the speaker location or height. Coaxials are good for this so I wanted to try a pair knowing that I would high pass them and use a subwoofer from about 80Hz down.

Driver Selection:

This was a budget project so chose the Dayton CX120 that is a 4″ inch driver with a 3/4 inch tweeter.

Enclosure Design:

I modeled the drivers in WinISD and came up with a cabinet that is 0.14 cubic feet (6.5″w x 8 1/4″ H x 7″ D). Although I have a 1 and 5/8″ curved pvc vent of about 6 inches, in practice I high-pass the speakers at 80 Hz using my PC as a source.

Crossover Design:

I used a combination passive crossover and DSP to clean up the response at the listening position. Honestly, these are pretty cheap drivers, and the response is a little uneven like many coaxials. I tried a number of different crossovers (including from some other CX120 builds on PETT) and wasn’t satisfied with any of them. I then tried a simple crossover and then used APO Equalizer Peace to tweak the response by using RTA where I sit at my desk. I can do this because my PC is my source and Peace is free. Voila – much better sound. Also coaxials sound bright on-axis so I listen to these about 10-15 degrees off axis. I use a sub for the lower end.

Tips & Tricks:

I like to use WAGO wire lever nuts for making passive crossovers. It’s easy to switch out parts and they’re secure unlike alligator clips.

Conclusion:

The CX120s are a good way to try out a coaxial design. They image well and I’m happy using them as work monitors whether for music or meetings. For sure they don’t get loud without distorting and I wouldn’t recommend using them beyond about 5-6 feet of listening distance, but I don’t need them to do that. For a desk solution and quiet listening they work well.

About the Designer:

I’ve been doing DIY speakers and amplifiers and some woodworking for about 4 years now. There’s always something new to learn and it’s very satisfying designing my own solutions and problem solving.

Project Parts List: