Project Time: 20+ hours
Project Complexity: Hobbyist
Project Cost: $500-$1000

Driver Selection
I wanted to try something “exotic” so I went for all Morel drivers. I used 5” midbass drivers for the center (CAW 538), 6” midbass for the floorstanders (CAW 638), and CAT 308 tweeters for all three speakers.

Enclosure Design
In order to keep the size of the floorstanders as small as possible hence maximize waf (wife approval factor), I decided to go with a sealed box (23liters instead of 48). Qtc used was 0.71 Based on the 5” Morels specs, they are better suited for a vented enclosure. Center speaker volume is 13 liters and the tuning frequency is ~52Hz. This was not a great idea in the end because the speaker was to be used as a center speaker that delivers mostly dialog/vocals, hence the extra bass was unnecessary. With the help of the techtalk forum I was advised to plug the vents and change the design to a sealed enclosure. A friend of mine built the enclosures because I have no woodworking skills. 1” mdf was used mostly with internal braces and a beech veneer. Since the center was built according to a vented speaker spec and accommodated the tubes, after I plugged the holes with rubber and silicone I had to decrease the volume down to 8 liters using mdf blocks inside the enclosure.

Amplifier/Crossover Configuration
The crossover design is based on a 3rd order Butterworth filter for both low and high pass filters. For simplicity I used the same crossover for both speaker designs. I went for a 3rd order to avoid the apparent lobing usually found when 2nd order is used. Crossover frequency is a bit lower than 2kHz. This frequency provides excellent transition between the Morel woofers and tweeters.

Conclusion
The main goal of this design was to make a pair of high quality floorstanders and a center speaker for my home theater setup that I can use for music listening also. From a sonic standpoint, the Morels offer clean and detailed sound. I feel that all three of them perform very well in every respect. Having in mind the potential radiation pattern nulls that might be a common problem with MTM designs, I tested these in my listening room and results were very good in all listening positions. The intention was to match or even outperform expensive speakers in the market and I believe this was accomplished.

About The Designer
Marios has been a telecom engineer for the past 15 years. He is fascinated by audio engineering and room acoustics ever since he can remember. He always wanted to design his own speakers but never got to it due to lack woodworking skills. With the help of a friend, a professional carpenter this was accomplished. It’s been a never ending learning experience.

Project Parts List