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About Invidiosulus

  • Birthday June 9

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    Mr. Lee’s Greater Hong Kong #28777
  • Interests
    Furniture design, Art, Music, Woodworking.

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  1. I’ll get a pic tomorrow. I actually added the 3/4” MDF onto the existing 1/2” plywood back, so 1-1/4” total. My cabs were pretty trashed when I got them and the back pieces were added 16 years ago when I had a tiny apartment in Orlando. If if I were to build some new heresy cabs I think I’d go at least 1” Baltic birch all the way around.
  2. Here is a plot showing reduction in resonance after I added 3/4” MDF to the back of my H1’s Don’t t get too worked up about the actual frequency response. The transducer I used for measuring the resonance wasn’t calibrated.
  3. You should replace the 1/2” thick plywood back while you are at it. Going 3/4” or thicker will help with resonances off the back of the cab that reflect off the rear wall causing mud in the bass.
  4. Hmmm, looks like I need to revisit mine. I think I kept the 2uF value when I replaced the caps in mine back in 2010. -Josh
  5. I don't need an official drawing to be able to take the dimensions from one of your drawings and see that your own dimensions do not resolve correctly to each other. Specifically, the "Needs to be checked" section of sheet 7 on page 1 of this thread. It doesn't check out. The pieces do NOT match up correctly. You yourself were the one who told me that a good CAD program wouldn't lie. I've taken your dimensions and drafted them in a CAD program with accuracy set at five decimal places and they do not work. The 2 versions that you sent Bruce didn't jive either. Now maybe you have already fixed the dimensions on Sheet 7 and this is much ado about nothing. If not, those pieces aren't going to go together correctly and I can prove it.
  6. Because out of the four different versions that you have shared/posted, none of them match up correctly with themselves. ¯\_(ツ)_/¯
  7. However, I haven’t gone over the rest of the measurements on the Jeff Robinson drawing. In my mind, if I were going to draw up plans based on say the ones in the Cohen article, it would make sense to start with the very obvious known measurements. Such as, 1. The overall size of the box 2. The known angles, 35, 24, 30, and 6 degrees. 3. The 4” square at the rear sides. 4. The size of the motor board. From these known measurements, the rest of the measurements could be quickly discovered. I might post a quick screen capture video or two of what I’m talking about. I can also show how I would verify that a drawing of the side pieces matches the mathematically correct angles from the compound angles calculator. Cheers, Josh - who has been spending way too much time thinking about this speaker cabinet this past week.
  8. Affirmative... uhhh... I mean, correct.
  9. In general, Jeff's version matches the dimensions provided by the published university plans for the classics with the overall length being 40.625". The motorboard in his drawing matches as well at 18.375" deep. The reflector is listed at 12.75"x30". One issue with the published plans is that if you use the dimensions listed for the roof of the doghouse you will end up with two boards trying to occupy the same space. This is because the plans list the bevel angle at 65 degrees. Changing that to 67 degrees as Jeff did makes the edges of the board line up perfectly as seen in his plans. Otherwise you will see something like the attached picture shows. This changes the angle between the doghouse roof pieces by 4 degrees. It sounds like different versions were built and published by University over the years.
  10. Next I measured the angle between the two faces with a sliding bevel gauge. Verified the correct angle (31.6 degrees). This matches up nicely with the front piece at the correct angle with 125 degrees between them in the horizontal plane. Cheers, Josh
  11. This was done in a hurry as I’m getting ready to head for work so I didn’t worry too much about the exact tenths of a degree. I set the bevel angle to 31.6 ish degrees. Next I made a 28.5 degree mark on my crosscut sled. Aligning the piece of wood to the miter angle gave me a cut that sits perfectly on the 35 degree angle needed to match the front piece. I took a square and made a mark at a right angle to the cut edge.
  12. Measuring the angle between the edges of the top of the board will give you a different angle than measuring the angle between the faces of the board. This is due to the miter angle. In the attached quick sketch you can see that the distance between the dashed red lines is greater at the top of the piece when measured in the horizontal plane. When measured relative to the two faces the distance is less. This accounts for the difference in measured angle as well. A table saw would need need to be set for the angle between the faces and not the edges or the cut would not come out right. So the measured angle in the top view is correct, it just wouldn’t be the most helpful to actually make the part in question.
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