You're doing well! The rest of us need this system for the following reasons:
- Its acoustically stable, structurally strong and robust design ensures that measurements are made in exactly the same way every time.
- The simple freely interchangeable measurement baffles ensure consistently repeatable and reliable measurements are made quickly and easily, without high skill levels.
- Accuracy careful set-up of the measurement microphone together with tight dimensional control and individual chamber calibration ensure highest accuracy and repeatable results.
"An affordable reliable system and procedure that allows design and manufacturing and then QC to measure a speakers characteristics in the same way in any global location is long overdue. To be able to carry out test/measurements that are repeatable anywhere in the world and provide the same data/result if carried out to the same procedure will reduce costs, improve products.”
- Eric Lytra
The Tetrahedral Internal Test System
It struck me that some of the most consistent measurements I had made over my career had been in a corner of a Chamber. So I thought why not basically build it from four triangles.
One of the Platonic Solids is the Tetrahedron, but modify it slightly with three right angled and one equilateral triangle.
A Tetrahedral based design has many advantages:
- As all of the major dimensions are different it will not support standing waves at high frequencies.
- It is inherently very stiff and strong resisting vibration.
- It is assembled from three identical parts and a series of fully interchangeable measurement baffles individual to the driver, tweeter or subwoofer under test.
Tetrahedral Test System - Parts
The system is built from three identical interlocking assemblies with a main baffle bolted securely onto the front edges of these three assemblies, all of these assemblies are bolted together using M6 Bolts and internal T-Nuts.
The main construction material is to be 24 mm Plywood with Main and Measurement Baffles having a 1 mm thick Aluminium skin inside.
The inside faces or walls and floor are covered with a 100 mm thick layer of Wool and then a 50 mm layer of Acoustic Foam.
The Microphone is held rigidly in a tube in the far internal corner, at a fixed distance from the internal face of the baffles.
Sub baffles are individual for every driver. All fit into 350 main baffle hole and have a 1 mm Aluminium Skin supporting the driver and a 45 degree chamfer at the rear.
The sub baffle(s) are clamped to the main baffle by 250 kg Horizontal clamps, whilst the drive units are clamped to the individual measurement baffles by 75 kg Horizontal clamps (dependent upon the loudspeaker) that need to be measured.
