Quad 8" subs for my office

[anotherhobby]

I started building these this weekend! I'll post a few progress pics in the next post. I ended changing the design to something that was less corner specific, and instead I am building a pair of these, angled opposite each other:

The internal bracing is complicated with 75° angles and other stuff — it would not have been worth the effort to design these without CAD. The build is a bit more complicated then my last two, but I'm doing this for fun so I don't care. The rounded outsides of the sub will not be pressurized and are only for looks. The will be filled densely with polyfill, and the final sealed internal volume will be identical to the other two I built.

They will be placed along the back wall of my office so the drivers are angled directly at me:

 

[anotherhobby]

After the kerf cuts, I used steam to soften up the MDF and bend it. Test fit!

Now I'm in the process of gluing it all together.

 

[Wolf]

You could fill the open ends with kitty litter or dry sand, and make them more inert.

 

[anotherhobby]

You could fill the open ends with kitty litter or dry sand, and make them more inert.

Thanks for the suggestion! Last night I was looking at it thinking sand might be beneficial, but I wasn't sure. I don't have any on hand, but I do have unscented kitty litter.

 

[Colonel7]

Thanks for the suggestion! Last night I was looking at it thinking sand might be beneficial, but I wasn't sure. I don't have any on hand, but I do have unscented kitty litter.

If you haven’t bought the new drivers yet they are the monster deal of the week at PE. https://www.parts-express.com/Dayto...-Subwoofer-2-Ohms-Per-Coil-295-508?quantity=1

 

[anotherhobby]

If you haven’t bought the new drivers yet they are the monster deal of the week at PE. https://www.parts-express.com/Dayto...-Subwoofer-2-Ohms-Per-Coil-295-508?quantity=1

Yes! I had been sitting on them, but bought two on New Years eve when I saw the price drop. Lucky timing!

 

[DevinCortno]

Had you done some DIY audio projects before you built these subs? Looks like excellent work and nice design on the new ones, too.

I'm looking to build a couple subs but I've never done anything like this before... I'm brand new to the whole process. Never even used a router before. A sub box doesn't look that hard, provided you start with a good design and follow it carefully. I've visualized mine already and just need to model out the bracing.

 

[anotherhobby]

Had you done some DIY audio projects before you built these subs? Looks like excellent work and nice design on the new ones, too.

I'm looking to build a couple subs but I've never done anything like this before... I'm brand new to the whole process. Never even used a router before. A sub box doesn't look that hard, provided you start with a good design and follow it carefully. I've visualized mine already and just need to model out the bracing.

These were my first speaker build. I've never attempted DIY speakers before due to an initial lack of confidence in my ability to get a quality finished product. While I wanted something unique and I wanted my own specific size and shape, I didn't want them to look like a lot of typical DIY subs (plain MDF, black spray paint, truck bed liner, carpet, etc). I stumbled across a build somewhere that used this exact same laminate on a pair of speakers, and I thought it looked awesome, and it looked like something I could figure out. That's really want got me off my butt and convinced me to give it a try.

From there I made lots of test cuts on junk wood and started practing. I did several test laminations with the laminate, testing cuts with the laminate router bit, and working to get a good finish. I didn't start building them until I was confident I could do all the things all the way thru. As an example, here is a test kerf bend that I made before I committed to doing curved sides for this second set of subs:

As another example, I had some left over laminate from the first two subs in this thread, so I also practiced heating and pre-bending and forming the laminate to match a bend. I did this just to make sure it worked first:

So, even though they were my first subs, and I was learning new skills, I did all the learning and testing on scrap wood. It wasn't until I was confident in each skill that I dove in and committed to making them. Any time I'm unsure, I just practice the same thing on junk wood until it makes good sense to me. Also, measure everything 3 times.

If it makes you feel any better, I bought and learned how to use my first ever router so I could build these subs. I also bought this circle jig that makes perfect circles very easy, and I bought this router bit just for cutting the Wilsonart laminate finish. Yes, that's almost $300 worth of tools I just listed, but you can get cheaper routers. I generally only buy high quality tools so they last me the rest of my life. I've already used the router on several other projects in the last year.

As far as designing the subs goes, with my complicated shape for this second set of subs, I could not have designed them without software. Figuring out the bracing in the subs was definitely a puzzle since the front and rear panels aren’t parallel. Every panel under pressure must get braced, and at the same time the completed internal volume of air has to be specific. In this case I was shooting for exactly 640 cubic inches, so you have to calcuate the volume of bracing and everything. I would not have tried it without CAD sofware. I'm using SketchUp because I have a copy and I'm very familiar with it, but I'm sure there are other better options.

 

[DevinCortno]

These were my first speaker build. I've never attempted DIY speakers before due to an initial lack of confidence in my ability to get a quality finished product. While I wanted something unique and I wanted my own specific size and shape, I didn't want them to look like a lot of typical DIY subs (plain MDF, black spray paint, truck bed liner, carpet, etc). I stumbled across a build somewhere that used this exact same laminate on a pair of speakers, and I thought it looked awesome, and it looked like something I could figure out. That's really want got me off my butt and convinced me to give it a try.

From there I made lots of test cuts on junk wood and started practing. I did several test laminations with the laminate, testing cuts with the laminate router bit, and working to get a good finish. I didn't start building them until I was confident I could do all the things all the way thru. As an example, here is a test kerf bend that I made before I committed to doing curved sides for this second set of subs:

View attachment 255085

As another example, I had some left over laminate from the first two subs in this thread, so I also practiced heating and pre-bending and forming the laminate to match a bend. I did this just to make sure it worked first:

View attachment 255086

So, even though they were my first subs, and I was learning new skills, I did all the learning and testing on scrap wood. It wasn't until I was confident in each skill that I dove in and committed to making them. Any time I'm unsure, I just practice the same thing on junk wood until it makes good sense to me. Also, measure everything 3 times.

If it makes you feel any better, I bought and learned how to use my first ever router so I could build these subs. I also bought this circle jig that makes perfect circles very easy, and I bought this router bit just for cutting the Wilsonart laminate finish. Yes, that's almost $300 worth of tools I just listed, but you can get cheaper routers. I generally only buy high quality tools so they last me the rest of my life. I've already used the router on several other projects in the last year.

As far as designing the subs goes, with my complicated shape for this second set of subs, I could not have designed them without software. Figuring out the bracing in the subs was definitely a puzzle since the front and rear panels aren’t parallel. Every panel under pressure must get braced, and at the same time the completed internal volume of air has to be specific. In this case I was shooting for exactly 640 cubic inches, so you have to calcuate the volume of bracing and everything. I would not have tried it without CAD sofware. I'm using SketchUp because I have a copy and I'm very familiar with it, but I'm sure there are other better options.

I've done a bit of Solidworks before so I was going to use that to make sure I hit 75 liters including sub & bracing. Not going to do curves though! Too saucy for me. I just want to do roundovers on the corners so they match my new towers.

The router is one thing... I inherited a table saw but ended up giving it away after not using it for 3+ years, so need to figure out what to do there. Maybe I could rent one or maybe a cabinet shop would do cuts for me for a certain amount of money.

 

[anotherhobby]

Progress is slowly coming along. Both the drivers and all the hardware is here. Everything is cut up and getting glued together now.

The angled box with wrap around sides make gluing less straight forward than usual. All the bracing gets glued to the face first, then the back panel gets glued to the bracing from the backside. Then the top and bottom will get glued on, and then wrap around sides will get glued last.

I'm currently gluing the back panels to the bracing for each sub, one at a time due to how many clamps it takes. Even though the wrap around sides are clamped at the corners in the pic, they are not glued there yet.

 

[Wolf]

You'll be surprised how much mass the kitty litter will add.
Make sure you tap on the cabinets to make it settle. You don't want it to be loose and rattle.

 

[anotherhobby]

One of the cabinets is all glued together now, and the other one is about 3/4 of the way there. In the pic below I clamped the legs in place and then hauled the sub up to my office to see how the legs looked from different angles. I'm quite happy so far! I think I'm probably another 1-2 weeks from having them fully done, depending on how much time I can get to work on them.

Initially I will be driving each R/L pair of subs on the same amp channel in parallel. The Crown will push a max of 750 watts into each channel at 2Ω, and the Daytons are rated at 300W RMS and 600W peak each, so power should be good. I don't need any delay between them, but I'll only be able to DSP each pair. If I want to DSP the two new subs independently, it will cost about $500 more ($300 amp + $200 miniDSP 2x4). I may end up doing that, but it's a lot cheaper to try this way first, and the REW sweeps I took showed promising results that this should work well. I wired up some Speakon cables today so all this plugs in nicely and I don't have to think about the wiring.

 

[anotherhobby]

I made some excellent progress this weekend! I now have 2 structurally complete subwoofer cases that need to be finished (laminate, legs, wiring, poly fill, and drivers). The curves and angles were indeed the big pain in the ass that I thought they would be, but they didn't get in the way of success. As I look at them now, I am really excited to get them over the finish line, and the completed subs are going to look very cool and unique.

I did end up filling them with kittly litter, but I could not see how on earth you'd do that during the gluing stage, so instead I drilled out a 1-1/4" hole after gluing was comlete, filled the two compartments with litter while compacting it down by tamping with a wooden dowel. The litter was packed in nice and tight, then I made plugs from the wooden dowel, glued them in place, and sanded them flat. The kitty litter increased the mass of the enclosure by exactly 50% from 17.6 pounds to 26.4 pounds. With the driver, legs, laminate, and wiring I expect them to land around 45 pounds each.

I'm pretty confident they will be done within a week or two now.

Pics of the kitty litter fill:

Here are the two subs as they sit now. I stacked them with their backs aligned so you can see the angled faces.

 

[anotherhobby]

You could fill the open ends with kitty litter or dry sand, and make them more inert.

I wanted to come back to this suggestion and thank you explicity for it. I had originally thought of play sand as I mentioned, but didn't want to deal with drying it out and was probably going to pass on the idea due to the fuss. Kitty litter was perfect, added a lot of mass as I commented above, and it was very easy to do since I had it on hand. Thanks again!

 

[Wolf]

You are very welcome! I've used and added it about 3 times in projects, and it's very effective. I'm glad it was useful for you.

 

[williamsol]

Looks very nice!

 

[anotherhobby]

Getting closer! Last night I cut and heat formed the laminate, and then started by applying the bottom laminate on each first so I could start attaching legs and doing wiring. I'm getting really excited for them as everything continues to come along great! I'm hoping I'll have them finished up by the end of the weekend.

Curved face laminate just resting after being heat formed:

Contact cement gets applied to both the suface and the laminate:

Then you press the two together, run a hard roller over it to apply a lot of pressure, and then cut the excess with a router. After that, there is a bit of cleanup work on the routed edges to make them smooth before applying the next piece to an adjacent face. This is the bottom side of this sub, waiting for legs and wiring:

Legs are applied one one of them, everything went well and I'm loving the look!

 

[juliangst]

Have you thought about using Dirac Live Bass Control for the subwoofer setup? It would be a perfect match for a multisub system like this

 

[anotherhobby]

Have you thought about using Dirac Live Bass Control for the subwoofer setup? It would be a perfect match for a multisub system like this

Good question! I have a miniDSP Flex which does not have DLBC. I wish it did as it would probalby make my life easier.

I have a few ideas of how this could work, but I'm pretty confident I'm just going to use MSO to dial in the subs on their own first, then present that to Dirac Live to work with. I did that with my living room system (except Audyssey), and after learning how to get a good result there, I'm confident that MSO mixed with Dirac Live can also be set up to do the same.

 

[anotherhobby]

Yesterday was a whirlwind of a day, and after a 1 month break due to life, I spent about 10 full hours to finish them off! I'll post more later on when I have time to try a few different calibration techniques. First, here's how all 4 of my custom 8" subs look as a group! I absolutely love them!

Each smaller front sub is paired with a larger rear on the same channel, running in series at 2 ohms, with each pair getting 750 watts from a Crown XLS1500. The internal volume of the smaller and bigger subs are identical, but the larger subs have 2 compartments filled with kitty litter and more materials, so while the smaller ones are 26 pounds each, the big ones are 43 pounds each. This is pretty damn heavy for little 8" subs, especialy with no amps since they are passive!

They are currently placed along the back wall of my office, althought I'm still playing with precise location. It seems shoved into the corners may be better in practice than they looked in my original predictions, but I have lots of time to flush that out.

Now for some measurements. I had prediced the response by testing and moving my original two subs, and then used REW RMS averaging of the locations to determine what 4 subs would look like compared to two. Below is how close the prediction was, with the GREEN line being actual response with the new subs. The low frequency is extended deeper in the final measurements because I had a filter in my miniDSP to prevent the subs from digging too deep, but with 4 I don't need that anymore:

This next graph is the uncorrected L/R responses, with the green line is the combined corrected Dirac response. I am very happy with the result, especially considering I am only using 2 amp/dsp channels to accomplish this!

This is the full response with no tweaks to Dirac. I want to try smooting this out a little more, but this is excellent! I am incredibly happy with the resuls! I can't believe how much better it sounds in the low end. I've only had about an hour of listening, but I'm already fully happy with my time and money investment here!