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My Shop Kit

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 

jr@macrjj45PWRRYDkenrhodesdynamoThumperTom

Comments

  • Make sure that resistor across the woofer is stout. 25W recommended.
  • Wolf said:
    Make sure that resistor across the woofer is stout. 25W recommended.
    R2 and R3? Would they be channeling that much power? 
  • @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.
  • 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.
    ani_101
  • 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.
  • 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.
  • 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
  • edited January 2
    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.
    .
    rjj45
  • 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.
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