My first full custom subwoofer

the box ended up smaller mostly becausse when fitting it, it ended up an inch and a half wider than my initial design. I won't ever trust Home Depot or Lowes to cut my wood ever again lol but it all fits now and all I need to do is fiberglass over it and I'm good to go. I got done fabricating the passive radiator already and it looks pretty decent for fiberglass hand molded without a form IMO

if im looking at your design correctly,and if i may,i knowshit all about sound and what not but, that all thread will become a tuning fork and become a resonance rod! anoying the shit outa ya.i mean they make quitar strings outa steel.am i reading this right?

The reason you hear guitar strings like that is because the guitar's acoustics takes advantage of the resonance frequency of each string. You pluck the string and the resonance frequency of the string is naturally amplified by the guitar. In my box, MDF which is 3/4 inch thick in a roughly 4 cu ft box which will be sealed up very tight with no Window now btw, having a rubber spray fix leak. Which turns into pretty much hard volcanized rubber, stuff sprayed in between each washer and in the holes that the rods are thread through to plug the which will be fiberglass ed over anyway and also I will be painting the entire interior of the box with a pretty thick coat of latex paint and I will also paint the rods wit it too but I'm probably going to glue a fabric around each thread with a rubber type adhesive before painting them so that they are very well insulated and any vibration will be damped. There is no possible way their resonance frequency will be heard if it were plucked like a guitar string from the outside when it's sealed, nonetheless from sound waves with a wavelength of 10 feet or more bouncing off them from crappy 250 watt rms, 750 watts peak each hooked up to a garbage 400 watt RMS Alpine class d mono block amp at a 2ohm load. They put out crap for pressure. This design shouldn't push put more than 122db max. I want sound quality, not to blow out my eardrums.

There would be far more resonance from not cross bracing with the sub enclosed walls moving than anything you could possibly hear sealed up like that as AA said earlier. The rods will be applying tension force on the steel and be pushing the MDF walls very tight against the fiberglass outside reinforcement which will make the box overall much more rigid. I'm no sound engineer and this is my first box, I'm no expert but at least I constantly learn from doing it

Here's the passive radiator I designed and fabricated with a nice grill on top of it. I guess it's not bad for forming it from fiberglass with no mold, for or skeleton lold

Nice to see someone researching and designing something custom! Keep it up!

Only comments I really have is the window size and intending on using 1/4" poly. I've done a ton of R&D work and fabrication that involves polycarbonate(and other plastics), specifically how it responds to internal and external pressure. (I helped construct two of the largest human environmental testing chambers in North Amercia.) With even a half PSI of pressure difference you are going to see a 1/4" window flex. You want 1/2" minimum just eyeballing the size you want your window. It will save you lots of aggravation of trying to brace it or modify your design later.

Also polycarbonate tends to delaminate under stress at the main stress points. All this means is to be sure to use lots of screws to fasten its edges and give yourself enough material between the screw and edge of material.

Keep up the work! and post pics!

Karma wrote:

Nice to see someone researching and designing something custom! Keep it up!

Only comments I really have is the window size and intending on using 1/4" poly. I've done a ton of R&D work and fabrication that involves polycarbonate(and other plastics), specifically how it responds to internal and external pressure. (I helped construct two of the largest human environmental testing chambers in North Amercia.) With even a half PSI of pressure difference you are going to see a 1/4" window flex. You want 1/2" minimum just eyeballing the size you want your window. It will save you lots of aggravation of trying to brace it or modify your design later.

Also polycarbonate tends to delaminate under stress at the main stress points. All this means is to be sure to use lots of screws to fasten its edges and give yourself enough material between the screw and edge of material.

Keep up the work! and post pics!

Thanks and I decided to scrap the Window a while ago. The box will be slightly smaller too. I'm going to fiberglass over it today since it's above 60 degrees and will get very cold so I'm lucky. Then it will be time to finish it and paint the box and ill be all done

I'm done fiberglassing the box. I decided not to have a perfect smooth finish and sprayed it with trucked liner. A perfect gloss finish would make me have to either remove more fiberglass than I want to or get about $60 more of resin. I've already spent about $90 on fiberglass materials alone on the box so fabut I want it to he extremely strong so that's okay



So I decided to fabricate my own more durable terminal plate. What's to point in having a super strong box with a flimsy plastic terminal plate? I ripped apart my broken Yeti mic and used its solid aluminum base and carved off the microphone legs from its base with a router bit, and sanded all the paint off for hours. It's about 3/4 inch solid aluminum. I plan on flush mounting it to the box itself from screwing it in the back and grinding off the extra screw part and epoxy over the screws and when I get time I can etch my own logo or take out the removable 1/2 solid aluminum puck that screws into the 1/4 inch bottom and get it sent to be laser etched. I'll put the Gold plated terminals on the bottom somewhat hiding, just gotta drill the holes now. Also I spent hours grinding the inverted round edge of the base to a flat straight edge so the terminals plate can be mounted right. I'll basically use my dremel and router bit and grind out a recessed 1/4 inch shelf for the terminal plate to screw into and epoxy and screw it in, add a rubberized coat in the inside of it and screw the solid aluminum puck from the inside out making look like one elegant piece.

I don't prefer terminals, personally. I like to use a pair of extra long binding posts, drill holes directly in the MDF and mount them, connecting the wiring inside. Another option: aluminum screws, washers and nuts.

I might ask - why use a terminal plate at all? Why not just drill holes for the terminals right into the wood? You can just disassemble the terminals that come with the cheap plate and reassemble them directly into the location you want with a simple hole.

Often the terminals used with plates aren't long enough to mount through the MDF, but there are extra long binding posts for this purpose, or just use aluminum bolts.

deekster_caddy wrote:

I might ask - why use a terminal plate at all? Why not just drill holes for the terminals right into the wood? You can just disassemble the terminals that come with the cheap plate and reassemble them directly into the location you want with a simple hole.

That just seemed tacky, and I wanted to d something unique. I really liked the terminal plate on my Velodyne ULD 18 but I didn't want a simple flimsy metal plate or even a weaker plastic terminal plate, so I did something no one ever does to a subwoofer. I custom fabricated a 3/4 inch aluminum flush mounted terminal plate with push spring terminals. The terminals are mounted in the aluminum by drilling 3/8 holes, putting in epoxy putty and right before the cure is done I drilled small holes and used long 8/32 screws and used the screw to thread the holes of the semi hard epoxy perfectly. I fabricated custom plastic washers to insulate and part of the terminals touching the aluminum. The terminal plate back plate is mounted in the box on the side I put a 1 inch thick MDF face because I ran out and that's what I had. I used a dremel and router bit and hand carved the hole and the shelf for the player to flush Mount perfectly. I then used fiberglass jelly resin reinforced with short hair fiberglass fibers and spackled it in the gap an behind the terminal plate, making it one big seamless piece. Terminal plates are usually the weak point of a box, but in mine, it's actually the strongest part of my box, and I think it looks cool and unique. Sure I could have simply drilled in some holes and put in long terminals. But that seemed really tacky to do. Even if my box d.oesn't have a perfect gloss finish, the aluminum plate makes it look like much higher quality, because it is.

this is my finished box. I have some more pics on my camera but my computer doesn't work.



I put liquid rubber on the aluminum backplate for a better seal.



Took a pic of when I fiberglassed it in

So the terminal plate isn't removable for access? Also, it appears the terminals are WAY to close for comfort! Careful a copper strand doesn't cause a short circuit.

AA wrote:

So the terminal plate isn't removable for access? Also, it appears the terminals are WAY to close for comfort! Careful a copper strand doesn't cause a short circuit.

The terminal plate is removable from the inside of the box. three machine screws mount the 1/2 inch thick solid aluminum terminal plate to the 1/4 inch thick aluminum backplate. The terminals are a little close but they are not touching at all. I fabricated the terminal plate to be self insulating by drilling two holes and pushing in epoxy putty and right before it cured, I drilled small holes in it, then threaded it with machine screws the same size as the terminal screws which created a perfect thread, then I fabricated some plastic washers to insulate each side of both terminals even further. There's no way it will short circuit. Wires will be fine because they are push terminals so basically you push the terminal to open the hole that the wire goes in verically, nowhere near touching each other. Also the copper wire soldered to the terminals are covered in liquid tape and well insulated with very clean solder joints and it's thick wire so it's nice and rigid and won't ever move enough to short circuit even if the wires weren't insulated


The box is done now but the passive radiator design failed. I'm going to find another Alpine Type E driver and just use a sealed box setup with it. According to the modeling program, I should be able to hit 123db with 750 watts in 3 drivers dead flat from 20Hz-80Hz.

Only problem is my Alpine amp isn't 1.33 ohms stable. I need to find an amp that will push 750 watts @ 1.33 ohms.

The main reason my passive radiator was a failiure was because it was basically 180degree phase from the drivers and also the construction wasn't as strong as I'd like. If I ever revert to passive radiator, I'll cutout two holes on either side of the terminal plate and mount in some TC sounds 12" high quality passive radiators which should be the proper setup, but those PR's are $160 each and not cheap at all.

I wish my Soundstream amp worked right now though lol. Its 1/2 ohm stable bridged and 1/4 ohm stable in stereo.