Here's mine. I put my phone on top of the speaker in the middle and pull up a compass app and just rotate the speaker while REW does repeated measurements. It's a pretty annoying setup to use but it did generate some off axis data that was useful for filter development. I want to make a better system but I also just want to buy some ascilab and call it a day lol.
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mikewxyz
Member
Here are the measurements using my DIY turntable. I think the non-uniform spacing between the two middle angles (30* & 45*) and the rest is a function of the turntable base being more exposed to reflections at these positions. Taking accurate measurements is difficult but the results seem OK to me.
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Curvature
Major Contributor
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You can try developing a compensation filter for those angles using a known source. For example, a flat-measuring speaker reviewed by Amir or Erin.
mikewxyz
Member
Thanks for the suggestion Curvature. I didn't intend to do anything with the data - more just a curiosity. $8 and some wasted time is about the level of investment I'm comfortable with. I would not spend the money to buy known measured speakers to use as a "measurement standard" for a gauge study.
terryforsythe
Major Contributor
Here is my turntable setup I just finished building and testing. I still need to cut down the platform and mount it to my ladder, but it seems to be working well.
It uses an Adafruit controller and stepper driver expansion board, connected to a Nema 17 stepper motor. It uses a 6mm belt to spin the table using a 4:1 gear ratio.
I created a Python GUI to run it. The GUI runs both on my Linux computer and my Windows laptop.
It uses an Adafruit controller and stepper driver expansion board, connected to a Nema 17 stepper motor. It uses a 6mm belt to spin the table using a 4:1 gear ratio.
I created a Python GUI to run it. The GUI runs both on my Linux computer and my Windows laptop.
terryforsythe
Major Contributor
I have the GUI working with REW to automate the measurement and rotation process. I explain it in this post:
www.audiosciencereview.com
Modifications to Elac Uni-Fi Reference UBR62 Bookshelf Speakers
What do you call that connector? It is a circular connector with push-pull locking. The manufacturer is Weipu. It is in the WEIPU IP67 - Large SA28 series. There are different pin configurations available - see the section "Solder Spec". https://www.weipuconnector.com/products/sa28/ They...
www.audiosciencereview.com
I just built a new measurement turntable that is basically a knock-off of MTG's turntable as seen here (post #3)
I did add one feature to help with getting large, heavy speakers up on a stand this high. I found this block and tackle pully system used for hoisting game for cleaning. I attached it to the outer and inner columns and this allows me to put the speaker up on the stand while its lower, then pull the rope to extend the column up to measurement height. Once its extended, the tower is locked in place with some steel pins. I still have to climb up a ladder with the speaker, but at least not as high.
The speaker pictured is at least 40-50lbs.
Just like MTG's design, the table spins on these MDF "wheels". I did not have a large Lazy Susan bearing, so I just made up something that works. The pivot point is just a steel pipe mounted to the lower wheel. The upper wheel is supported by a number of these "roller balls" which are basically casters with spheres instead of wheels. Cheap and worked well. Probably not as smooth as a real Lazy Susan, but it wasn't hard to turn with the speaker on there and I can upgrade later if I feel the need.
I did add one feature to help with getting large, heavy speakers up on a stand this high. I found this block and tackle pully system used for hoisting game for cleaning. I attached it to the outer and inner columns and this allows me to put the speaker up on the stand while its lower, then pull the rope to extend the column up to measurement height. Once its extended, the tower is locked in place with some steel pins. I still have to climb up a ladder with the speaker, but at least not as high.
The speaker pictured is at least 40-50lbs.
Just like MTG's design, the table spins on these MDF "wheels". I did not have a large Lazy Susan bearing, so I just made up something that works. The pivot point is just a steel pipe mounted to the lower wheel. The upper wheel is supported by a number of these "roller balls" which are basically casters with spheres instead of wheels. Cheap and worked well. Probably not as smooth as a real Lazy Susan, but it wasn't hard to turn with the speaker on there and I can upgrade later if I feel the need.
terryforsythe
Major Contributor
If you are using REW to take the measurements and want to automate the process, I have posted the computer code to google docs. I am using an Adafruit Itsy Bitsy M0 Express controller, an Adafruit TMC2209 Stepper Driver, and a stepper motor. It requires use of the Pro upgrade for REW.
Here is a link to the prototype in action:
c++ code for the Adafruit ItsyBitsy controller:
https://docs.google.com/document/d/10wD4b7UR8v50WHPFHFuK0yz3xInsSkIPP4k2B9Npf-0/edit?usp=sharing
Python code for the User Interface:
https://docs.google.com/document/d/1oOfAn9XkeB79seE6KC5B5qNTPhNGkp3o4Nadbv5lvgk/edit?usp=sharing
The user interface runs on Linux and Windows using Python. It also may work on a Mac, but I have not tested it.
Here is a link to notes for using it:
https://docs.google.com/document/d/1qE0cRJhmeEhFoTQvvIdHkSx0EpI7wzNtZMJEaeFMAA8/edit?usp=sharing
