Discussion on what materials to build speakers out of - Page 87 - diyAudio
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Old 29th March 2013, 10:42 PM   #861
roline is offline roline  United States
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Nice boxes, I've always been partial to walnut!! You can countersink the terminals to thin the material. I do that on the back side of my power amps. PLEASE post pics of the assembly while in process, how much stuffen is used etc...
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Old 29th March 2013, 11:14 PM   #862
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Quote:
Originally Posted by Enzo View Post
Exactly. You can buy commercial jack plates or cups from places like Parts Express.

That makes sense to me, but if you are into wood work, you could also use a router to make a cup in the wood. Mill out space for the two posts down to maybe half the thickness of the panel.

An example:
Round Speaker Terminal 2-7/8" Gold Spring-Loaded 260-276

They come in round or square, with spring loaded or banana posts, etc.
I thought about all this stuff, but since I was using this as a learning experience, and since I plan on giving these to someone who will be overwhelmed anyway, I figured it wasn't worth the hassle. When I build my next pair, which will use mahogany intead of walnut, and which will likely be built from an $1100 kit instead of a $425 kit, I will definitely be using hardwood on all six sides. Whenever you do something like this for the first time, there are always things wish you would have done differently. For my next pair, I think I'm going to go a little thicker with the hardwood which will enable me to use a bigger radius roundover router bit for the corners. I like the roundover look that's simply not doable with veneer.
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Old 29th March 2013, 11:28 PM   #863
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I'm also planning on building a pair of speaker stands. I was thinking of using 1 1/2-inch steel pipe filled with sand for the columns, 3/16-inch thick steel sheet metal for the top and three pieces of 1 x 1/4-inch steel flat for the legs. Does anyone here have any better ideas?
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Old 3rd April 2013, 06:00 PM   #864
kbyrne is offline kbyrne  United States
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I have a speaker building 201 book and it states to win in competion use MDF or European
plywood and varnish. Send speaker parts and specs. to a place called maddison sound to
verify them. Build speakers in Bass Box and crossover in a supplied link. I am inexperienced
but can look up an send along links if you wish. Just ask. Best Kevin
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Old 5th April 2013, 05:15 PM   #865
markusA is offline markusA  Sweden
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Whoa, this thread is a behemoth.
Very interesting though.
Let's see if I have understood the basics...

- High Q will have a narrow frequency band and a high peak
- Low Q will have a wide frequency band and a low soft peak (i.e the oposite)
- High Q resonances are less easy to destinguish
- The height of the peak is proportional to how much energy is needed to get the resonance going.
- The energy of sound waves/vibrations is proportional to the inverse square of the frequency.
- By using a cabinet with a high resonance frequency and high Q the energy transmitted by the music will be unlikely to trigger any audiable panel resonances.

- Plywood is stiffer than MDF and has a lower density.
- The stiffer the cabinet/panels the higher the resonance frequency.
- The heavier the lower the f.
- Ply should have a higher resonance frequency in that case all things being equal?
- The Q is proportional to the frequency, higher f results in a higher Q.

One thing I haven't seen mentioned is a small piece of information about CLD.
By using identical inner and outer layers the energy transmitted through the visco elastic layer produces shear forces that are located in the right place and this is what is absorbed and dissipated by the sticky suff. If you use different inner and outer layer the forces might not act at the optimal depth. That's what I've been told anyway.

- Stiffness and braces will keep the walls from flexing as well.

Now for some questions...
Is there a formula to estimate panel resonance that applies to speaker cabinets?
Is it possible to calculate the difference depending on the bracing?
How do you calculate what is needed to avoid wall flex? (Ballooning?)
How much weight (spikes are not an option) is needed for the speaker not to move around from the music?
What are the effects of diffusion panels inside the cabinet?
Where should they be placed?
How do you decide where to apply what acoustic damping material and how much? Pollyfill is different from fiberglass insulation and should be treated differently.

The tread is 87 pages long and I sort of accumulated the questions while reading through it...

I'm gearing up for a larger 2-way build so this is good stuff for me. The inside of the cabinet will see the full 20-20kHz...
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Old 5th April 2013, 06:00 PM   #866
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Quote:
Originally Posted by markusA View Post
Let's see if I have understood the basics...

- High Q will have a narrow frequency band and a high peak
- Low Q will have a wide frequency band and a low soft peak (i.e the oposite)
- High Q resonances are less easy to destinguish
- The height of the peak is proportional to how much energy is needed to get the resonance going.
- The energy of sound waves/vibrations is proportional to the inverse square of the frequency.
- By using a cabinet with a high resonance frequency and high Q the energy transmitted by the music will be unlikely to trigger any audiable panel resonances.

- Plywood is stiffer than MDF and has a lower density.
- The stiffer the cabinet/panels the higher the resonance frequency.
- The heavier the lower the f.
- Ply should have a higher resonance frequency in that case all things being equal?
yes

Quote:
- The Q is proportional to the frequency, higher f results in a higher Q.
I am not sure about that one

Quote:
One thing I haven't seen mentioned is a small piece of information about CLD.
This thread does't really get into CLD at all.

Quote:
Is there a formula to estimate panel resonance that applies to speaker cabinets?
Is it possible to calculate the difference depending on the bracing?
How do you calculate what is needed to avoid wall flex? (Ballooning?)
Some tool like ANSYS, preceded by measuring the parameters of your raw material. There are formulas that give very rough indications.

Quote:
What are the effects of diffusion panels inside the cabinet?
Where should they be placed?
How do you decide where to apply what acoustic damping material and how much? Pollyfill is different from fiberglass insulation and should be treated differently.
Topics for more threads.

dave
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