SoundEasy V28 released - ANSI-CTA-2034 automatic measurements

[bohdan]

Hi George,

The ”outrigger” concept may require some investigation.

For a very simple reason.

The outrigger has the potential to take significant amount of (loudspeaker + rig itself) weight off the turntable. This would almost double the available load spinning capacity of the turntable.

The outrigger does not have to be placed at the end of the loudspeaker. It only needs to stand far enough from the turntable to prevent the loudspeaker from tipping over – so just past the long wall’s half-way point. Assuming, that the outrigger is rigid enough, this would rest almost the whole weight of the loudspeaker on the outrigger. The turntable role would be to driver the outrigger.

Perhaps, the wheels of the outrigger may need to be replaced by just a single wheel on a swivel, and the wheel would have to be attached to the turntable by a rigid rod, or some other rigid means, so that the outrigger does not tip forward/backwards.

Even for the horizontal polar measurements ( loudspeaker placed in a normal vertical position), you could attach to the turntable (behind the speaker), a small outrigger with a platform, to support the loudspeaker’s weight at the back. This way, no need for the “curtain rod”.

Anyway, does this make sense to anybody?.

Best Regards,
Bohdan

[soongsc]

Hi Bohdan,

The outrigger concept, I guess which was illustrated with the wheels, actually increases the rotation loading. This loading maximum allowable I have not really tested yet. This is due to the rolling resistance, wheel mass, and the arm leverage to the wheels.

The bearing of the turntable can take up to 150Kg in the vertical direction as provided by the supplier. So it seems we have enough design margin. But the rotation loading originally was calculated at the edge of the turntable with 30Kg. We feel it can take up to 60Kg, but do not know how much margin we have because the original estimation was done by the supplier when they recommended the motor. I do not know what kind of acceleration they based their calculation on. When we start trying to load the table to max, we will know.

Currently the design is based on our own in-house needs, but we could custom design and ship whatever a customer wants. Or once the maximum loading is tested, the customer can decide to attach their own depending on their specific needs.

The wheel as you mentioned can be added, and the bottom sliding rail is designed for something like that to add on, large diameter wheel about the diameter of the turntable would work best as it will have less rolling resistance. However, the weight of the wheels and the leverage not needs to be added to the weight calculation.

As far as back of the speaker. if the speaker gets sooo deep such that the CG will extend outside the edge of the turntable, you could use an additional wheel, it adds more friction and rotating weight.

Personally, I think tall speakers should take a cylindrical measurement approach because the diffraction edge now gets closer to the mic and kind of pollutes the data because such diffraction will reach the mic earlier than first room reflection, but such will not occur in real world application.

The curtain rods are for adding the second axis turntable. The full design is supposed to be expandable. But an idea just popped up. Let me see if I can get some wheels to play around with the loading with outrigger wheels. If I can stand no the outrigger, wheels and the table still turns, then this can be added as an option.

[soongsc]

Anyone know of light weight 6" caster wheels out there? Immediately around me are some that weight quite significant. Looking for vinyl tires with plastic rims.

[bohdan]

The rig shown on the attachment is being used for the turntable measurements. Looks like there are solutions available.

[soongsc]

Yes, it could be done that way. If this is the ARTA table, they have to do it like that because of the way their gearing is set up. The gears could loss contact if the load is not balanced near the center of the table. That table also would also have some difficulty being used in a second rotation axis due to the way the bearing, gear, and motor arrangement. If the speaker is taller than one meter, they would also have to place the mic further than 1 meter away from the speaker, otherwise the speaker could hit the mic at 90 degrees down position.

[soongsc]

This roller wheel for another project just came in. Seems like a nice low friction, low weight, and light solution. The only limitation is that it has to be used on a nice smooth solid floor due to it’s size. Thoughts?



My current thought is still going ahead with base expansion, but use these roller wheels to make it easier to move around. The outrigger option we should try for anechoic chamber application with larger wheels, in such case which actually three wheels would be required.

[soongsc]

Some heavy weight concepts.

[RT60]

Hi Soongsc,

we did a similar project some years ago.
Here you will find some material:

https://www.youtube.com/watch?v=VSsbYYfASiM

https://artalabs.hr/AppNotes/ARTA-Hardware&Tools%20-%20Annex%201%20-%20AutomaticTurntable-GerRev1.3.pdf

https://artalabs.hr/AppNotes/AP-9%20ARTA-AutomaticTurntable-GerRev1.4a.pdf

Regards
Heinrich

[soongsc]

Hi Heinrich,

Thank you for the information. Yes, we had looked into the design and was inspired by it. How long did it take for the software to interface with the motor? What turning load did you expect out of the design?

Regards,
George

[soongsc]

Here is an update with the lower base expansion added, also added an additional arm to support the loudspeaker. The location of the arm can be adjusted, and the length of the arm will be extended to 30 cm (twice the shown length). Some cleanup of the design is pending some parts to come in.

[soongsc]

In case anyone would like to use the turntable to add their own speaker supporting rig, here are the dimensions and specs of the mounting bolts accessible from the top of the table.



And the holes to attach your own expanded bottom.

[JRT]

Also... In case anybody is looking for extruded aluminum structural materials, look at what is available at:
8020 dot net 

You can also find similar materials for sale elsewhere. 

This is not SPAM. I have no affiliation with them,  have no profit motive in this, and it does not directly compete with anything that PE has for sale.

[soongsc]

Here is an update with the lower base expansion added, also added an additional arm to support the loudspeaker. The location of the arm can be adjusted, and the length of the arm will be extended to 30 cm (twice the shown length). Some cleanup of the design is pending some parts to come in.

A question had been raised whether the base will counter rotate when rotation during measurements or not. Our first impression is that due to the nylon balls used, we are not expecting it to react in such a way due to static friction. But in case it does happen, washers can be placed under the balls to keep it still. These will be provided as part of the kit.

[Shonver]

bohdan will you make the RS232 communications specification available, or are you making it exclusive for Soong's turntable?

[soongsc]

bohdan will you make the RS232 communications specification available, or are you making it exclusive for Soong's turntable?

Hi Shonver, The instruction set is Cool Muscle standard instruction set. If you use their motor, it would be a simple interface. Gear ratio is currently 100:1 in case anyone wishes to do their own design. We hope for more ideas to come out as well as more advanced features in SoundEasy. Whether Bohdan will support multiple interfaces is up to him. We chose this motor because it did not require too much effort on his part, and we thought that this was the easiest way to get the table implemented so that he could focus more on advanced measurement data processing. Hope this answers your question.

[Shonver]

Thank you, George.

I would recommend considering implementing a G-code option, as that would open up other options to the DIYer community due to the myriad of CNC-based accessories available these days.