The Pyktis Subwoofers

[trevordj]

I have had aspirations to build a complete set of home theater speakers for several years. I started the design process about 6 years ago with modeling subwoofers and trying to figure out how big I was willing to go. I very much fall into the trap of bigger/more being better and jumped in head first. I also needed to get a wood shop set up first so several years were spent collecting equipment and getting my garage where I wanted it.

I overestimated my abilities and underestimated how much time I would have available and selected the drivers and amplifiers. I ended up purchasing some Stereo Integrity HST-18 D2 subwoofers, four to be exact, in 2015. At the time these drivers were a pretty good value for the money at $500 each. They were universally recommended as they were huge, beefy subwoofers capable of tons of excursion and able to take a ton of power that wasn’t bad. They fit well in a modestly sized box for an 18” woofer. I had also previously used some SI shallow mount subs in my car and liked them so I was confident with the brand. Initially I planned to build two sealed dual opposed boxes but once I received the drivers I realize that would be very impractical as the boxes would likely weigh 250lb. I transitioned to building four sealed boxes. I also purchased a pair of Seaton branded SpeakerPower SP2-8000 amplifiers to power them.

Then I had my second child and was trying to get my career off the ground. Life added up. I also knew that I needed to learn how to paint. I got overwhelmed and everything ended up turning to paperweights.

Fast forward 5 years, we had moved a couple of times and my garage was full of crap I had never used, this planned project was just one of many. I was left needing to either clear out the garage by selling things or by actually completing some projects. I have been without any home theater speakers for 5 years as I thought I would have had all my speakers built relatively quickly.

I decided to move forward with my builds, one at a time, and have spent the majority of my nights and weekends clearing the garage by completing things. Before I could start the subwoofers I needed to get the room completed, which I did.

Then the fun began. Lots of pictures to follow:

I modeled the sub in Jeff Bagby’s software (RIP) and did the 3D design in fusion 360. The only thing I added to the design were some additional braces as I went along. All the parts were cut The box was assembled with wood glue -Trevor

[trevordj]

I added a chamfer around the perimeter



Cutouts for the speakon connectors



Raw boxes done

I did the trench method on the joints to try and hide them



Body work started, some filler and sanding to get the panels flat

Purchased some nice feet from parts express and epoxied the threaded inserts in place -Trevor

[trevordj]

I mentioned before I needed to learn how to paint. This actually preceded starting this project. I had a couple goals: 1) I wanted to use 2K automotive paint for durability and looks, 2) I wanted to learn how to get a painted appearance and, for the future, also wanted to learn how to get a clear finish over raw wood.

The former goal I accomplished by painting a ton of scraps. I turned some of these into fun projects for my kids. This was the last test I did, painting some shields. My process was 1) sand the wood with 120 grit, 2) skim with body filler or (easier) spray with polyester primer, 3) block sand, 4) more poly if any wood shows through, 5) epoxy sealer, 6) base and clear, 7) color sand and polish

The latter goal of finishing wood with clear I accomplished by completing a magic mirror for my wife. Process here is: 1) sand wood running the grits to 220 grit, 2) spray with simtec 28x50 clear polyester, 3) block sand, 4) repeat with more poly if any wood exposed, 5) run the grits to 800, 6) spray with 2k urethane clear -Trevor

[trevordj]

Before starting paint I added the additional bracing. I underestimated how much I would need when I designed these otherwise I would have done as two pieces instead of four. It worked out well though. I started by painting the bottom of these, mostly to practice my technique and make sure everything was dialed.

They were sprayed with polyester, blocked, and then sprayed with House of Kolor KD3000 sealer I had to sand the sealer and re-spray as they weren’t yet perfect Better -Trevor

[trevordj]

Base, House of Kolor Black Pearl S2-PBC43 Clear, House of Kolor USC show clear Color sanded with 800 grit Flow coat of clear Sanded with 1500, 3000, then 5000 grit Polish Polished. Note this is the bottom of these subs, this will likely never be seen. This is mostly just proof of concept for me that I can get a mirror finish if I need to. -Trevor

[trevordj]

Switching to the other side

Taped Flipped Sprayed with poly Blocked Sprayed again I sprayed everything up to this point with a 3M accuspray gun. I don’t recommend it. I didn’t have anything to compare it to, but when it came to polyester it sprayed it very poorly. For a beginner, the accuspray gun was appealing because it has the ability to switch out plastic tips. “It’s a new gun every time” they say. I was always intimidated by hvlp guns worried that I wouldn’t be able to properly clean it and ruin it so this was exactly what I was looking for.

Don’t believe the hype, cleaning a gun is easy and a high quality gun makes everything so much easier. I recently purchased several new guns, one each for primer, base, and clear. My base and clear guns are Devilbiss DV1s. The first time I sprayed with them I was blown away. My primer gun is a Tekna Primer. It absolutely packs the primer on with only a tip pressure of 19psi. With the accuspray it was just not able to push the polyester out even with a 2mm tip. This led to me having to up the pressure and then I would get dry spray.

Get a nice gun if you are going to spray. -Trevor

[trevordj]

Base and clear. I used the same Black Pearl paint but because these will be in a home theater I sprayed them with flat clear, House of Kolor FC21

Painting process video showing sealer, base, and clear

https://vimeo.com/440902680

The color is hard to capture with a still, here is a short video. The pearl give this a really nice look.

https://vimeo.com/440831197

Speakon plugs added About 6lb polyfil added Subwoofer in Feet installed -Trevor

[trevordj]

Completed! I have about 200 hours into these subwoofers, the majority of that was on finishing/sanding. Much of that can be attributed to inexperience. I would hope in the future to cut that time at least in half. I am happy with how these have turned out. They are not perfect but only I would know where the small mistakes are.

They are named the Pyktis subs. Pyktis is a Lithuanian word meaning dark or anger. My wife is Lithuanian and helped me name them. I think that also adequately captures her dislike for these huge boxes 🙂. She appreciates that they are well done but it is not her dream to have four subs in the house.

Whew, that’s it for now!

-Trevor

[tomzarbo]

Epic project... and epic writeup as well! Glad you took the plunge and decided to build them instead of selling. You made the right choice!

They came out beautiful Trevor, really nice. Understated boxes, not too huge, and they blend in nicely for being as big as they probably are.

How do they sound in the room? They've gotta' jiggle the insides a bit right?

TomZ

[djg]

Very nice, I love the chamfered baffle. I would worry about them getting kicked

[trevordj]

Epic project... and epic writeup as well! Glad you took the plunge and decided to build them instead of selling. You made the right choice! They came out beautiful Trevor, really nice. Understated boxes, not too huge, and they blend in nicely for being as big as they probably are. How do they sound in the room? They've gotta' jiggle the insides a bit right? TomZ

Thank you! I cannot believe some of the subwoofer builds that have become the norm, mostly over on AVSForum; subwoofers the size of refrigerators and any driver smaller than 21 inches is small. I love audio but I needed to have something reasonable in size.

I haven’t gotten a chance to fire them up yet. I just settled them in the room two days ago and built all the speaker cables yesterday. I had also planned to build my XLRs yesterday’s but couldn’t find the cable I thought I had to do so. I have some Mogami cable on the way and I should get the signal cables hooked up on Wednesday.

Right now I am also in the process of building three front stage speakers and then I have six surrounds I need to build too. For now I will hook the subs up with only the overhead speakers playing.

-Trevor

[trevordj]

Very nice, I love the chamfered baffle. I would worry about them getting kicked

Thank you! Getting kicked is a possibility but I didn't want to complicate the design by adding a grill cover. Fingers crossed. I'll have to probably not practice kung fu in the home theater until I get a little bit better control.

[mmu7]

As someone who has struggled with spray paint jobs, WOW amazing.

Questions.

What kind of filler did you use? I don't have access to a spray poly (what ever that means) and I have used duplicolor sandable primer.

How did you prevent dust accumulation during the spray job.

[trevordj]

As someone who has struggled with spray paint jobs, WOW amazing. Questions. What kind of filler did you use? I don't have access to a spray poly (what ever that means) and I have used duplicolor sandable primer. How did you prevent dust accumulation during the spray job.

Thank you!

I used Evercoat Rage Ultra for filling. Any of the premium body fillers will work fine. I also used Evercoat 440 Express for filling pinholes. In the future I would probably use fiberglass impregnated filler for the joints for added strength although so far none of my joints are telegraphing.

In the future I also probably wouldn’t mess with trying to straighten the panels with anything but sprayable polyester primer. My process here was very inefficient, I was still trying to figure out exactly how to best accomplish my goals. My future process for bodywork will be: 1) trench the joints, 2) fiberglass filler (likely duraglas) in the trenches, then just spray three really heavy coats of polyester primer followed by guide coat/block sanding.

Really, everyone has access to sprayable polyester primer. I used Evercoat Slicksand which works really well. As long as you have an air compressor you can get an HVLP gun for $100 or so and it will change your life compared to anything that comes out of a rattle can. With a rattle can it’s tough to get more than just a few mils of build before it runs. Also, the more you build it, the more solvent you are waiting to flash off. When spraying any coating, solvent is the enemy. It’s a vehicle for getting solids onto a surface but it is also responsible for a lot of coating failures if there is too much of it. Catalyzed coatings, such as polyester primer (which is really nothing more than sprayable body filler) have a much higher proportion of solids therefore there is less solvent needing to flash off and since it relies on curing rather than drying to harden it gets much harder and is ready to sand faster. You can get anywhere from 4-8mil per coat of poly primer, if you put three coats on that is a ton of material.

As to dust management, I spray outside so there is always a possibility of getting junk in the paint. I found a pop up awning prevents 90% of that junk. Other than that, it’s all about proper prep. It is important to clean the surface with a manufacturer recommended post sand cleaner until you are getting nothing on the towel. Follow that up with a tack cloth and blowing it off with the air compressor. Between coats it is important to let the product flash per manufacture instructions, then tack and blow before spraying. It’s a little scary tacking between base or clear coats and you have to be gentle but as long as your coats aren’t too thick it works out.

If you are spraying gloss clear, dust nibs are no big deal, after the clear cures you can color sand and either spray a flow coat of clear or polish. That was the tough part about spraying with flat clear, you can’t polish it. If any junk gets in it you have no choice but to sand and re-clear.

-Trevor

[trevordj]

Ok, here is where I am really going to need some feedback, measurements. I started messing around with omnimic tonight and took some sub measurements. These are the first measurements I have ever taken of speakers so be gentle. These are averaged short sine sweeps. The first measurement is with the atmos speakers (wired in stereo) and the subs. I initially had a phase issue that I fixed with reversing polarity on two of the subs. The other two are just the subs.

This is without any other eq, time alignment, etc. There is a 100hz 24dv/octave crossover between the atmos speakers and the subs.

There is no smoothing in these plots



I am building to the point where I am going to be measuring to build passive crossovers for some LCRs and surrounds I am currently building. I figure this will at least get my feet wet.

-Trevor