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.
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
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
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...
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...
yes
I am not sure about that one
This thread does't really get into CLD at all.
Some tool like ANSYS, preceded by measuring the parameters of your raw material. There are formulas that give very rough indications.
Topics for more threads.
dave
Since I did not discover the answer in many pages of this thread, let me ask the following:
I am building a guitar cabinet, and I am wondering what the material of the brackets should be. Their type of wood. I am only using horizontal and vertical brackets that brace the panels of the cabinet, no other fancy internal bracing. Just peripheral brackets to hold the pieces together and mount the back and the baffle.
So, what is the best option for the wood they are made of? I have access to Swedish Pine, Pitch Pine and African Ayous. All of them around 20mm x 20mm. Which one is best for the application? I obviously need rigidity (guitar cabs push lots of volume) but I think that the brackets also need some flexibility to align with the wood panels. Which one do you vote?
I am building a guitar cabinet, and I am wondering what the material of the brackets should be. Their type of wood. I am only using horizontal and vertical brackets that brace the panels of the cabinet, no other fancy internal bracing. Just peripheral brackets to hold the pieces together and mount the back and the baffle.
So, what is the best option for the wood they are made of? I have access to Swedish Pine, Pitch Pine and African Ayous. All of them around 20mm x 20mm. Which one is best for the application? I obviously need rigidity (guitar cabs push lots of volume) but I think that the brackets also need some flexibility to align with the wood panels. Which one do you vote?
Rigidity is not the goal of a guitar cabinet. Resonance contributes to tone, that's why great guitar cabs are not made from MDF. Typically you want high quality Baltic birch, limit bracing to what is necessary for structural rigidity. If you are building a 4x12 look online for internal shots of vintage Marshalls (or whatever you prefer). A 2x12 or single 12 will require no bracing.
If you are just talking about blocking for the sides anything will work. It would be very advantageous to do a dovetail joint, but if you don't have the tools you can route a dado.
Jeff G.
If you are just talking about blocking for the sides anything will work. It would be very advantageous to do a dovetail joint, but if you don't have the tools you can route a dado.
Jeff G.
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Yes, I am using Birch Plywood and yes, I will limit the bracing only to what is needed for structural rigidity - that is peripheral brackets to mount the back and baffle on. Exactly what I mentioned earlier in my post.
But the question still remains - what wood for the brackets?
I would suggest the one that best holds screws (or threaded inserts) over time.
dave
Bingo! I will use threaded inserts in all brackets. So, which wood of the above would you suggest? Let me remind you my options: Swedish Pine, Pitch Pine and African Ayous.
I think you can just use clean pine construction lumber 1"x2" or 1"x3" to make the braces that the front and back will screw too. Glued and screwed the braces to the cabinet. That's always worked well for me.
While this can be used for front and back screw blocks, I would suggest 2"x2" in the corners to make the joints stronger, again screwed and glued.
As to vibration bracing, that depends on the shape of the cabinet and the number of drivers. To make relevant contributions to that subject we would need a lot more information of the specifics of your cabinet design, and the number of drivers per cabinet.
I would say in a common 4x12" Marshall style stack box, a single horizontal 1"x2" on the sides. To what extent you would need to brace the back panel is variable. I could be a couple of 1x2's in an "X" pattern. I would be a couple of horizontal or vertical braces. There could be an internal horizontal brace connecting the front of the cabinet to the back of the cabinet between the upper two drivers and the lower two drivers.
I've also seen tall Fender style cabinets with 2x12" drivers. Generally, somewhat like the Marshall cabinets, these tend to be somewhat shallow with a large face and back. Like the front and back would need bracing as this is a pretty fair expanse of area. Again, it could be horizontal or vertical or braces in an "X" pattern, or it could be front to back bracing as described above.
To some extent it falls heavily on your own ingenuity. If you feel you can construct cabinets of decent quality, then you should be skilled enough to work out the details.
Also, the tools and work space you have available determine how complex and how smooth the design can be implimented. Most of what I did, I did with very minimal tools, frequently in the front yard or in the basement, and I feel I got very good results.
So, if you want more than generalities, you have to provide us with information that goes beyond generalities. The more we know, the more precisely we can respond.
Steve/bluewizard
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Many thanks for your replies!
Dave, pitch pine is thought to be a hard version of common pine. From what I have gathered, this must be the hardest one.
Steve, I have really basic tools and I am not seeking anything special. I will use one 12" driver, but I have left room for the addition of another one if I like. The cab measures about 72cm x 45cm x 32cm (external dimensions), and is made of 18mm russian birch plywood.
I just want rigid brackets to hold my baffle (which I will initially make removable due to experimentation needs) using threaded inserts. But I have heard that brackets don't have to be stupidly rigid, since this will not enabe them to line up with any imperfections the panels could have.
Dave, pitch pine is thought to be a hard version of common pine. From what I have gathered, this must be the hardest one.
Steve, I have really basic tools and I am not seeking anything special. I will use one 12" driver, but I have left room for the addition of another one if I like. The cab measures about 72cm x 45cm x 32cm (external dimensions), and is made of 18mm russian birch plywood.
I just want rigid brackets to hold my baffle (which I will initially make removable due to experimentation needs) using threaded inserts. But I have heard that brackets don't have to be stupidly rigid, since this will not enabe them to line up with any imperfections the panels could have.
I've had good luck with pine. Common Yellow Pine construction lumber. Bearing in mind that, generally speaking, once the screws are in, they are in. Only rarely would a person have to open the cabinet, and unless a person foolishly strips out the holes, which would take some effort, pine will work fine.
Now, the above applies to wood screws. With the 3/4" thick (19mm) front and back screw braces, I've put threaded "T" nuts behind the braces, and used Machine Screw to hold the back on. Because this is nut and machine screw, you can pretty much open and close the cabinet an infinite number of times with no degradation in the quality of the screw connection.
http://www.woodpeck.com/tnut.html
I use screws on the front of the cabinets, but the screws are only there to hold things secure until the glue sets. I put the front panel screws in from the back. Though you could use a nail gun from the front, and fill the holes created by the nail heads. The specific details are up to you.
For the back, so you can get in and perform maintenance as necessary, the back panel needs to be removable. Again, straight up wood screws or "T"-nut and machine screws will work fine.
There is a type of wood screw that would work very well, if that's the type of screw you want to secure the back with. They are called POCKET SCREWS. These tend to have very deep threads and very large flat heads.
https://www.kregtool.com/store/c20/kreg-jigreg-screws/
Buy 8 x 1-1/4 Coarse, Kreg Pocket Hole Screw, Zinc, 500-Piece, SML-C125-500 at Woodcraft.com
This illustrates how Pocket Screws are usually used -
Pocket Hole Guide - WOOD Community
If you use common wood screws to secure the back of the cabinet, I would recommend also using a conical or finishing washer to spread the force of the screw out, and prevent the screw from digging deeper in to the wood each time you re-screw it in.
#10 Brass Finishing Washers (4 per Pack)-20791 - The Home Depot
http://www.amazon.com/Countersunk-Finish-Washer-Black-Plated/dp/B0040CVWP6
I would also use the Conical Finishing Washer even if I used the Machine Screws and T-Nuts previously suggested. It keeps the screw head for going farther into the wood panel each to you re-secure the back panel.
Just a few random thoughts.
Steve/bluewizard
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72cm x 45cm x 32cm
For the metrically challenged among us -
28.4" x 17.72" x 12.6"
If we are using standard 18mm to 19mm wood (3/4" = 19.05mm), then with the top and the internal screw brace, we lose 1.5 inches on the top and bottom or 3" overall. (3" = 76mm). That means the internal space of the cabinet is reduced to 25.4" (645mm). If we subtract two 12" (~300mm) drivers, we only have a very thin gap (<45mm, 1.8") between the drivers.
I would suggest that you need at least 1" internal clearance at the top and bottom and a min of 2" clearance between the speakers. With speakers that close in the middle, I would suggest and additional brace between the upper and lower speakers. That's minimum 4 inches or about 100mm. You have 45mm maximum, so the cabinet needs to be at least 2" (50mm) to 3" (75mm) taller.
Though that's just my opinion.
Steve/bluewizard
For the metrically challenged among us -
28.4" x 17.72" x 12.6"
If we are using standard 18mm to 19mm wood (3/4" = 19.05mm), then with the top and the internal screw brace, we lose 1.5 inches on the top and bottom or 3" overall. (3" = 76mm). That means the internal space of the cabinet is reduced to 25.4" (645mm). If we subtract two 12" (~300mm) drivers, we only have a very thin gap (<45mm, 1.8") between the drivers.
I would suggest that you need at least 1" internal clearance at the top and bottom and a min of 2" clearance between the speakers. With speakers that close in the middle, I would suggest and additional brace between the upper and lower speakers. That's minimum 4 inches or about 100mm. You have 45mm maximum, so the cabinet needs to be at least 2" (50mm) to 3" (75mm) taller.
Though that's just my opinion.
Steve/bluewizard
Here we have spruce & douglas fir construction material, Doug Fir us a pine species. I wouldn't use it for battens (Bernie has built some quite nice boxes out of it), for that i'd likely use Alder.
dave
I am currently making a set of loudspeakers with curved sides (lute shaped) made up of 9 alternate layers of 3mm Birch Plywood and 3mm MDF (27mm thick). I have glued the sides to the top, bottom and two mid braces using PVA glue. QUESTION - just to make sure that the braces and sides do not part company I have drilled through the sides into the braces and then glued 3 6mm dowel rods in place. Will this have an adverse effect on the overall sound do you think? I am going to veneer the cabinets afterwards so you will not be able to see the ends of the dowels.
Any advice would be much appreciated.
SteveT
Any advice would be much appreciated.
SteveT
Hi guys,
I just got a quote for my Pensil 10.3 build. 19mm BB Hoop Pine Ply is $230 plus GST per sheet. I hadn't counted on that much! I'm planning on veneering these boxes, so the finish isn't important. Is there another grade I can look at, or should I just re-set my expectations about how much the wood's going to cost? I understand that it's the ply count and lack of voids that's important - I could just go and look at what the supplier has.
Cheers,
Jon
I just got a quote for my Pensil 10.3 build. 19mm BB Hoop Pine Ply is $230 plus GST per sheet. I hadn't counted on that much! I'm planning on veneering these boxes, so the finish isn't important. Is there another grade I can look at, or should I just re-set my expectations about how much the wood's going to cost? I understand that it's the ply count and lack of voids that's important - I could just go and look at what the supplier has.
Cheers,
Jon
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