Anarchists Build Log

[wogg]

Nice xover writeup, Wogg! Very detailed and easy to follow. Thanks for sharing. These speakers really looked and sounded great at Indy.

I have one question. I noticed that you used the "sphere baffle step" function, when merging woofer NF/FF/Diffraction files, instead of creating and using a custom diffraction FRD using VituixCAD's diffraction tool. Just wondering what your thinking was on this process.

Great question... no idea. That's probably a potential improvement, I was getting direction from a Vituix guru at that point so that decision falls into a "someone smarter told me to" bucket

[4thtry]

Nice xover writeup, Wogg! Very detailed and easy to follow. Thanks for sharing. These speakers really looked and sounded great at Indy.

I have one question. I noticed that you used the "sphere baffle step" function, when merging woofer NF/FF/Diffraction files, instead of creating and using a custom diffraction FRD using VituixCAD's diffraction tool. Just wondering what your thinking was on this process.

[wogg]

Another section of write up is available on my Wogg page.

http://woggmusic.com/anarchies-crossover-design/

This outlines the VituixCAD design process I used for these and has some good tips on using the PIR to FR as well as the Merger tools. There were some settings on those that I didn't find intuitive and had to get some help, so I'm hoping this write up is useful for people.

Almost all done with documentation! Last thing is the final assembly and finish detail with validation measurements of the final product.

[wogg]

Finally, and what I find super interesting is the +-90 degree directivity plot. This shows the effect of the symmetrical tilt to the driver centers with a corresponding tilt to the off axis responses.

Left side

Right side


Here's a couple shots of the measurement setup today. Not a lot of space in the cave to do this, which limits my gating and general accuracy a bit. Definitely room for a more fancy measurement setup, but with the results I'm getting this works alright!

The center pivot reference was the front and center of the stand. This runs up with the baffle surface but due to the angles isn't exactly the centerline of the drivers. The mic height was about on the mid axis, as the stands are a bit high so ear level on the couch is below the tweeters.





Ignore the carpet.... it's crazy old berber that keeps cat hair ball color forever, or until I rent a steamer and clean it again. Also, my feet are super goofy looking at this angle.

[wogg]

Lastly, I did a full -90 to +90 degree sweep in similar 30 degree increments in the same space I did the original individual driver measurements for design. I did run into some weirdness attempting to merge near field woofer and port measurements. The close mic woofer measurements rolls off slowly at about 100Hz, making the merge look like a massive +12dB boost below 300 that doesn't seem to match reality. So this exercise is limited to the 300Hz bandwidth from gating.

The PIR files were all processed in Vituix, then added to a driver without crossover to graph. First the SPL charts for L and R.



The L and R match is within a couple dB, not exact but not bad considering I did not check or adjust anything between the 2 sets. Up next, Power and DI.

Left side


Right side


The L tweeter seems to have some more off axis issues in the ~18k range, but otherwise these remain similar.

[wogg]

The first thing I did was a simple REW measurement at the listening point, ungated with both speakers driven. This is through an older Yamaha Aventege receiver using only 2 of the 5.1 channels in direct mode, no EQ and no DSP.



Compared to my last build in the same spot, the Supernova Minimus



Kind of hard to tell, but the most obvious part is the low end where the Anarchies have a massive advantage below 60Hz, blowing the Supernova away and producing lots of output in the mid 30's. This is in spite of the +6 setting on the bass control for the Supernova.

Today I pulled off a slew of measurements, we'll start with 1M on axis and gated as processed by ARTA.


That's an easy +-2.5dB window from 300 to 20k with only that drop from ~1.8k to 2.4k that is a little worrisome. The flatness above that is remarkable! Let's flip the mid and see what happens.



This isn't surprising, the design was not simulated to have a reverse null at 1M and was instead focused on a smooth power response at a simulated distance of 2.5M. The reverse response is also pretty smooth, with some reduced smoothness above that 2.5k mark.

Ultimately this means very little, the phase may line up at some distance from the speaker creating that reverse null but I have no idea where. I swapped the phase back to design.

[wogg]

It's been a minute since these debuted at inDIYana, let's wrap this thing up. Final position: The simulation values were used to build the final product, and after listening and testing them this seems like a solid conclusion.

Here's some shots of the final product

[wogg]

WTF... the pictures are back! Odd, let's see how this post does.

Stand assembly today. The binding posts on little aluminum stock inserts, 16ga primary wires run through the pipes and up the top.




I used a 2 part epoxy to fill the pipe threads for assembly. I left the top piece holes tight so the pipe threaded into the MDF with the epoxy squeezing out as it went. No way to thread both sides, so the bottom holes were sanded out a bit to allow me to pound them in with a hammer, again with the epoxy in the threads to hold it all together. The front dowel was assembled with a healthy glob of Titebond II and a single screw in the center.



Now they're in drying mode on the floor to keep the top and bottom aligned. They had a little wiggle without the glue dry and one of them ended up with a good amount of angle that needed to be corrected on the floor like that.



The finish on the poplar dowels is pretty close to the baffles, not perfect. My dad was a master finish matcher and would have done better. I will use hot melt to fix those binding post plates into the base so I can remove them to fix or tighten connections if I have to. There will be a slight amount of Duratex touch up required, most notably I didn't think about those bolt counter-sinks being exposed on the bottom side of the top plate.

[wogg]

Dangit. Now both posts have no pictures. This is getting annoying, had lots of errors getting them up there but they were displaying fine. The forum software is not cooperating here.

[wogg]

Yup, are they not there for you? I see them just fine.

[Colonel7]

Me either - No pics

[a4eaudio]

"I don't have a drill press..."

Check you PMs

[unclejunebug]

Are there supposed to be pictures with your two posts above? I'm not seeing any (tried Chrome and Firefox).

[wogg]

The steep pipes actually thread in pretty well in a 1" hole. Not enough to hold for long term, a little epoxy for final assembly will do the trick. To test the length of the pipes and dowel, a little level comparison against the bench top will work.



Here's what they'll look like... pre-finish.



Now to solve how to get the rear binding posts mounted. I didn't account for the chamfer, so my original idea to use a 3/8 rabbet bit on each board to make a 3/4" wide recess for a little aluminum mounting pad isn't going to work. I'll have to break out the adjustable rabbet bit and offset it down to fit.

[wogg]

Stand progress, finally good enough to do some outside work and finish these suckers off. I flush trimmed the stand tops against the bottom of the speaker cabinets, then cut 45 degree corners off all of the base boards. I used a clamped down stop to hit the corners all the same.



Then it was a circle cut for the port clearance and a run around everything with a 45 degree chamfer bit on my make shift router table. That gave me a pile of pieces to work on the vertical bits in the basement.



I don't have a drill press, so the pipe and dowel holes were set by hand. I went about 0.25" deep on the single thickness top board, and all the way through the bottom board. The bottoms are double thick, so that puts it 0.75" recessed. The depth was a little at a time with my mini combo square for a depth gauge.



Compared to the 1" holes for the steel pipe.



The dowel and the steel pipes came out almost exactly the same length, there was just enough for curf in extra length on the dowel so we're within margin of error on the height.