Tests and Analysis of the Seas DXT Tweeter
I am an experimenter more than anything. I like to find out what makes something work (or not work, as the case may be). This has extended to speakers. I am at the point of doing design, from measurements to construction to final tweaking, but I still like to go back to taking something apart to see how it works. You'll find a bit of that here because I have a few pages on tweeters, which are sometimes good candidates for a modification or two.
Experimenting with and measuring drivers and baffle treatment is one of my primary interests. You'll find a lot about this and CAD modelling as well.
My site has grown considerably, with sections on cable interaction, windowed measurements, a fair set of large-baffle quasi-anechoic raw measurements, baffle diffraction effects and treatment with felt, the basic electro-acoustic models, some articles on practical considerations and a bit more.
One of my forays is Tweeter Tweaks. This section shows all details of adding wool to the pole piece vent, but not just any wool. I found, quite by accident, a product which is very useful for tweeters. It is used to stuff the pole piece vent and has absolutely no negative effects. I wholeheartedly recommend it for tweeters for which access to the pole piece vent is possible. Some tweeters either prevent access and/or they already have a good filler from the manufacturer. Examples of the latter are the Vifa XT-25 and the Scan-Speak tweeters (probably all of them). I also have a section that shows results of the testing of changing rear-chambers.
Maybe one of the more useful pages is a web-based version of an article of mine published in Speaker Builder magazine (ONE:2000) included. It describes a method for determining relative acoustic offset for drivers when mounted on a baffle.
You may find a couple of pages on CAD software to be of interest. One deals with phase error due to an inaccurate CAD model. An example using CALSOD is extensively documented. A second one deals with the Hilbert-Bode transform and the effects which can occur when the CAD model does not have enough range, as when the high end rolloff of a tweeter is too high for the measurent system.
On the topic of modifications you'll find several section with a set of tests of several drivers, primarily tweeters, but I'm taking on some midrange testing and/or tweaks now. This one was my first evaluation of a driver. One of the tweaks is creating a soft-dome tweeter from what appears to be a clone of the Morel MDT-29 magnet structure and the MDT-32 dome/voice coil. It's fully documented. Some midrange tweaks will be online, possibly this month as well (July 2006).
The pages on raw measurements are those using my "quasi-IEC" baffle as I call it. This provides measurement data (with downloadable zip files) that extends down to about 250hz and has no diffraction artifacts due to the windowing used in the MLS software. The panel is now a 2m x 2m baffle with a replaceable 12" x 24" insert and is more rigid. Cutouts for each driver dimension are used.
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