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Another post about impedance jigs
It is often mentioned that you can build a DIY impedance jig for $5 to $15 and there is a good "sticky" thread over at Parts Express Tech Talk. However, I have noticed there and on some other forums that beginners, if they try to build the jig, don't have problems building the jig but rather run into problems making the correct cabling connections. After @4thtry thoroughly documented his build a dual-channel jig I thought I would take the plunge.
To better understand how the jigs worked I made a few different versions. I have documented in elementary terms, step by step, how to build a DIY impedance jig (3 different versions) and how to measure impedance and calculate T/S parameters in REW. You need a 2 input, 2 output pre-amp, but you need this anyways for a dual channel measuring setup. I'll be selling my DATS v3 in the classified soon. Also, I built some extras of Jigs 2 and Jigs 3 that I'll post in the classifieds in a week or so.
If you are interested, see the impedance study HERE.
Comments
This ^ is VERY well done and exemplary work!
Thanks.
Just finished your study. Very well written, with detailed drawings and photos showing all the necessary connection points and software settings. It took me a while to digest the entire report, but it was well worth my time. Thanks for sharing. I have a couple questions/comments:
1) Were did you get that nice aluminum case for Jig 3? This almost looks like the same case that is used for the Lepai 2020 digital amplifier, except that it probably came with an undrilled front and rear panel.
2) This is the first that I have heard about the "dual added mass" method. I need to read up on this technique and give this a try. As you said, it is more accurate. Looks like it can make a huge difference in an alignment.
3) The reason I decided to build the Arta jig a few years ago was because @dcibel posted a detailed schematic diagram showing all the necessary connection points and values. This made it very easy for me to follow and build. And then he was very helpful in answering my questions about the appropriate software settings and cable connections. Other published papers and software help files only showed block diagrams of the necessary connection points, which simply did not give me enough info to figure it out.
4) Now that I have been using the Arta jig for a few years, the connections and re-connections are becoming second nature. I can disconnect the Arta jig and set things up quickly for loopback amplifier tests, then quickly reconnect it for more loudspeaker measurements, then quickly disconnect it for more amplifier tests, etc. I still use OmniMic if I am in a hurry, as it is much faster to set up and use. Same for DATS V2.
Thanks Bill!
Parts Express Part #320-425 $5. As you could probably tell in the pictures, it is pretty small, but I like that I can screw it down by the flanges. I made a jig in a big, and really light, plastic box and if I moved the speaker cables it would just yank it off the table.
Yeah, I'm not sure how accurate my measurements were, but I thought that was kind of a good thing for beginners. When someone takes screenshots of everything done right with perfectly correct impedance and T/S parameters and then the beginner comes in and screws something up, they have no idea what went wrong.
As I said in the article, and linked to your thread, I would have never tried to build the jig if you hadn't laid it all out first. It was kind of funny, when I linked your thread I went back to look at something I was posting at the time that the block diagrams totally intimated me.
I have not used the jig in practice yet. But will be measuring in about a month for by Dayton SDC build and am looking forward to flipping the switches.
I built a fancy jig at some point using a plastic project box and the guts out of a USB sound card. It did pretty well imo.