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In-wall Speaker Measurements (Monoprice THX-365IW)
A couple of weeks ago I post the measurements of the Monoprice THX-365IW. For that, I built a leaky back wall in an attempt to approximate the actual application. Alas, that provided such messy measurements that I thought I start over using a new methodology/system. Klippel NFS has a module...
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A couple of weeks ago I post the measurements of the Monoprice THX-365IW. For that, I built a leaky back wall in an attempt to approximate the actual application. Alas, that provided such messy measurements that I thought I start over using a new methodology/system. Klippel NFS has a module for measuring drivers in a baffle. It is a combination of a special baffle and different measurements system where only the surface of the baffle is scanned. I asked for an evaluation license for the module which normally costs more than 4,000 Euros. The baffle is even more expensive so I decided to build my own. First attempts were total failures as the module assumes you have their fixture and its special alignment points. I made a second try and almost succeeded:
I say almost as the software performs an alignment check and complained that accuracy was not as good as it should be. It was right: it pushed the microphone into the baffle at some point. Still, the results are much cleaner and I thought I share this with you and make a collective decision if we need to keep going this way.
As a way of background, Klippel NFS scanner makes measurements in a semi-hemisphere. This way, it doesn't matter what radiates in the back. To the extent any of that reflects from the walls, NFS computationally eliminates it. Furthermore, since edge diffraction occurs outside of the scanned area, it is able to eliminate that as well. Fort his to work though it requires a lot of distance between the "driver" and the sides of the baffle and hence the wide width you see. The width is also dictated by the height of the in-wall speaker which is naturally much taller than what Klippel had in mind with a single round driver.
Measuring and cutting the baffle was one thing. Getting it to mount and stay stable on a 5 inch stand was another! In addition to this, you have to be mindful of any resonances in the baffle being captured and reported as part of the speaker response. You can't see the back side of my baffle but I managed to deal with these effectively as well.