My Shop Kit

hifiside

Since I get asked to build a set of bookshelves or towers for people throughout the year. I decide to build a few kits so I don’t have to spend countless hours searching for drivers and tuning crossovers that nobody would want to pay for. I used a Peerless 830855 Woofer and a peerless DX20 tweeter which I have plenty of. The crossovers aren’t finalized yet do to the rain we had the last couple days makes for a noisy shop but we are close. I can get 4 cabinets per 1/2 sheet of mdf which makes them around $4 a cabinet. Glue up is very simple and the laminate pieces I use the finish the edges (for no wood shrinkage marks) are scrapes from the years of previous projects. Terminal cup and will probably get changed on the final one but here’s what I came up with.
Tuned@53hz
.15 cuft 

Wolf

Make sure that resistor across the woofer is stout. 25W recommended.

ani_101

Wolf said:

Make sure that resistor across the woofer is stout. 25W recommended.

R2 and R3? Would they be channeling that much power? 

ani_101

@hifiside do you round over the bracing to ake them fit in the channels? My CNC boxes still have a minuscule misalignment and drives me nuts ending up with a lot of sanding/trimming.

Wolf

I generally keep the resistor across a woofer if needed to be 40 ohms or higher so less current will flow. I know it's for Fs suppression to flatten out the FR. Parallel notches in that range get expensive, series notches would as well.

Look at it like this- you have a coil (lowpass) and a resistor (shunt) directly across the amplifier outputs, so the resistor will get warm being the flat load across the outputs. I always use 25W+ resistors if I have to place them across a woofer for this reason.

hifiside

ani_101 said:

Wolf said:

Make sure that resistor across the woofer is stout. 25W recommended.

R2 and R3? Would they be channeling that much power? 

It’s R2 or R3. This is where I quit on the x-o do to the noisy rain on a tin building.

hifiside

ani_101 said:

@hifiside do you round over the bracing to ake them fit in the channels? My CNC boxes still have a minuscule misalignment and drives me nuts ending up with a lot of sanding/trimming.

No my bracing has square edges I only round over the through holes. I don’t have to sand anything until there all together.

hifiside

Wolf said:

Make sure that resistor across the woofer is stout. 25W recommended.

I’ve had them playing for about a week now. Stunt R doesn’t get hot and I play them to xmax and beyond. That circuit might get a cap added to it by the time I’m done tho. In my polymer cabinets I use a 40ohm stunt that works great but these are mounted different so it changed some things

PWRRYD

Hi Brad,
Love seeing your projects and thank you for sharing this one here.  This is just a question, not a criticism.  Are your measurements taken at that low of a SPL?  How far is your mic away?  I ask because I usually send my wife and kids away somewhere, turn off the furnace and all house fans, dishwasher, etc. and still my noise floor is around 50-55 dB.  So when I measure I measure with the mic as close as I can but still capture the entire baffle effect (at least 3 times the baffle width), and I crank the volume as high as I can without damaging the poor tweeter.  90 dB at about 30" is usually about where I'm at.
.

hifiside

PWRRYD said:

Hi Brad,
Love seeing your projects and thank you for sharing this one here.  This is just a question, not a criticism.  Are your measurements taken at that low of a SPL?  How far is your mic away?  I ask because I usually send my wife and kids away somewhere, turn off the furnace and all house fans, dishwasher, etc. and still my noise floor is around 50-55 dB.  So when I measure I measure with the mic as close as I can but still capture the entire baffle effect (at least 3 times the baffle width), and I crank the volume as high as I can without damaging the poor tweeter.  90 dB at about 30" is usually about where I'm at.
.

For FR usually around 70db. Distortion test are high volume 90-100db. Mic is always placed 2.5 times the baffle width on everything I do. This one is around 15” gated at 4ms. My area I test them in is quite big. 16ft ceilings and 10ft from any wall about 6 ft from floor. I’m in a industrial area so the middle of the night I do measurements and it’s very quiet out there. I’m going to finish the x-o this weekend I could try higher volumes to see if it makes a difference.

hifiside

Got some roll on 2k primer filler and a rattle can of 2k primer filler. Normally I would choose one or the other but I wanted to try them out. 

hifiside

Cut and buff it tomorrow. Turned out really nice for roll-on primer and rattle can finish.

jhollander

That Spray Max is in my amazon cart, thanks for the tip

hifiside

jhollander said:

That Spray Max is in my amazon cart, thanks for the tip

So far it’s been easy to work with. I’ll know more tomorrow when I cut and buff it. 

ani_101

What is the order of painting, as pictured? Sand how many coats of each and what grade of sanding in between? This looks like a good start to rattle can painting...

Also what is the engine enable for? Is that the darker shade on the baffle? 

And what do you mean by "cut it"?

Thanks for this series... 

PWRRYD

Cut it = wet sand

hifiside

Yes what PWRRYD said.
 I’ll know more when that actually happens 

hifiside

I’ll breakdown the steps later today. I’m happy with the results there’s a few things I would do different the second time around tho.

hifiside

My process for finishing.
 1 block sand all sides of enclosure with 80 grit and a hard sanding block (piece of mdf)
2. roll on glue (titebond blue). Enclosure sides 2 coats. Laminate 1 coat. Then press on with a iron.
3. After cool down router each side flush as you put it on. 

4. Block sand sharp edges of the laminate (round corners a bit) so it doesn’t catch on anything as you move and fumble the enclosure around.
5. Router round over
6. 180 grit DA (Dual action sander) all laminate to give it a good tooth.
7. 220 grit all round overs and other surfaces left.
8. Blow it off well. (Air hose, air in a can, etc..)
9. Mix primer 4:1 and roll on. 15 mins in between coats. Make sure the roller is completely wet with each coat or it will pull up the existing coat.
10. After 4 hour @ 70degs. 320 grit block sand enclosure. Re-Primer spots if needed.
11. I used the 2k primer surfacer (rattle can) as a sealer surfacer which after a 1 hour dried very good and sanded quick with 500 grit nicely.
12. blow it off good. And wipe gently with a quality Tack cloth.
13. shake color can. Fusion nickel silver paint. 1.00 per can at Ace bargain bin. 20 min flash time between coats and at least 4 coats. Let dry around 45 mins. Do Not tack cloth before clearing..
14. Rattle can Clear coat. Follow directions on can. Spray first coat med/wet, second and third Wet I used a 10 min flash time between all coats. These air dried @75 degrees for around 16 hrs before wet sanding and buffing.

Kornbread

Is there a certain kind/style of laminate you look for?  

hifiside

Smooth surface no pitted stuff and cheap. If you have a countertop manufacturer around you, you can most of the time take there scrapes that are plenty big enough for what we use it for.