Maxolini, Solidworks will be more useful for my marine craft projects, especially the mechanical on the water gokart and I had a good read of Blender, and it is very powerful, but I still don't know if it suits engineering. Something to be explored in the future. I don't feel that FreeCAD is in the position to be a solid Freeware alternative due to the developer's approach for the whole program. They need to get the various benches consistent before users would be interested in coming back with bugs and things. I would admit that I see the program as an already lost cause........still highly useful but not very serious
I am rather inclined to beat this program into a useful prototyping tool for the hobbyist by working within its set of limitations. By using it to design a number of production ready items, I have already found many of those limitations. The good part is, once the limits and bugs are found, what's left is still a highly usable environment. This project will be a good measure of its performance. Let's see if it can be used to completely design a product with all the part complexities drawn in. Keep in mind that FreeCAD is not too bad for designing a part, the difficulties arise with interactions with other parts as the model gets more complex
There is something to really like, though. Once a full product model is created in detail, it is very simple to pull off individual parts or even chop up parts to fit the working areas on the CNC or 3D printers. It's worth persisting with at a hobby level
I am rather inclined to beat this program into a useful prototyping tool for the hobbyist by working within its set of limitations. By using it to design a number of production ready items, I have already found many of those limitations. The good part is, once the limits and bugs are found, what's left is still a highly usable environment. This project will be a good measure of its performance. Let's see if it can be used to completely design a product with all the part complexities drawn in. Keep in mind that FreeCAD is not too bad for designing a part, the difficulties arise with interactions with other parts as the model gets more complex
There is something to really like, though. Once a full product model is created in detail, it is very simple to pull off individual parts or even chop up parts to fit the working areas on the CNC or 3D printers. It's worth persisting with at a hobby level
@weltersys
Is it Art? Hey man, how do you feel about replacing the dual 6.5" Dyaton PR units with a single 8 or 10"?
Is it Art? Hey man, how do you feel about replacing the dual 6.5" Dyaton PR units with a single 8 or 10"?
Some thoughts at this stage. Eliminate the robot head look and hopefully increase performance at the same time by replacing the dual 6.5" passive radiators with a single 10" passive radiator. This will also allow more of the structure to be built with PVC foam core sandwich instead of bamboo. 10" is the max radiator size that will fit this structure, so why not build in max Sd and Xmax here. This basically eliminates one whole panel and replaces it with an engine mount. Another side benefit is that it can be placed on its side 
with the PR firing down. The SBA 10" PR with 17mm Xmax looks good. I will use that as a reference but will first run a DIY 10" PR with hexcel sandwich and butyl surrounds in a custom printed basket. I'll do this spider less but with dual roll surrounds. There is an existing thread I started on PR units and will update that thread with that drivers build. I hope knowing types of folks like @weltersys concur with this line of reasoning towards evolving this baby porch PA sub
with the PR firing down. The SBA 10" PR with 17mm Xmax looks good. I will use that as a reference but will first run a DIY 10" PR with hexcel sandwich and butyl surrounds in a custom printed basket. I'll do this spider less but with dual roll surrounds. There is an existing thread I started on PR units and will update that thread with that drivers build. I hope knowing types of folks like @weltersys concur with this line of reasoning towards evolving this baby porch PA sub
Many driver's spiders have air permeability built in, which would allow the interior air to leak through the pole vent extension, "short circuiting" a passive radiator.
You can test by blowing air through the vent, if the cone moves out and holds the air for a while, leakage shouldn't be a problem.
That would eliminate the force cancellation the dual passive radiators offer, an important feature when making a lightweight cabinet that can easily walk around.
An aluminum cone PR may transfer heat faster than a paper cone.Another side benefit is that it can be placed on its side
The aluminum cone SBA 10" SW26DBAC-00 PR has 400 grams Mms (14 oz, near a pound) of moving weight, about that of a small claw hammer head.
Mounting a PR horizontal is generally a bad idea, gravity will defeat linear response, and with a Vas of 54L, I'd expect it would sag considerably.
The paper cone SBA 10” SB29NRX-00 passive radiator is heavier (505g Mms) and looser (66L Vas).
Have you calculated their Fb in your box volume?
Art
Art, thanks heaps. Your thoughts are always welcome and helpful. Looks like I have some decisions to make on PR size and quantity
Thanks for catching the leaky spider thing. The air blows right through it! I will adjust accordingly
I hope that the following plan forward can be made to work, bearing in mind your concerns and the objectives of this project
Dual custom 8" or 10" PR units. These drivers would be flat honeycomb with 0.5mm aluminium skins. These are light and compliant and hopefully can tune by adding skins to reach the target 40hz. The pic below shows the flat type. The back of the diaphragm will also use a roll surround of smaller dia on a puck
Thanks for catching the leaky spider thing. The air blows right through it! I will adjust accordingly
I hope that the following plan forward can be made to work, bearing in mind your concerns and the objectives of this project
Dual custom 8" or 10" PR units. These drivers would be flat honeycomb with 0.5mm aluminium skins. These are light and compliant and hopefully can tune by adding skins to reach the target 40hz. The pic below shows the flat type. The back of the diaphragm will also use a roll surround of smaller dia on a puck
A smaller roll diameter will have less excursion than the larger front roll, and a different rearward compliance/stiffness than forward, Kms(x) nonlinearities.
https://www.klippel.de/fileadmin/_m...linearities–Causes_Parameters_Symptoms_01.pdf
Thanks for the link. I had a good read of that and absorb what I can. Would you please help confirm if I am understanding this correctly?
With passive radiators
- As long as the system is sound, things are fairly linear with small movements. Physical limitations start imposing with larger movements
- More Sd will need less xmax
- Light initial diaphragm weight means higher stock tuning but also more options to tune for smaller active drivers and volumes with large passive radiators
- It might be possible to get a very linear action over a smaller excursion by using dual 10" PR with the 6.5" active
If I am getting this correctly, then I would like to build the 10" passive radiators. The rubber surrounds are really supple and large subwoofer type radius. I can use the same roll surrounds on both sides of the diaphragm if that keeps things linear. A composite sandwich diaphragm is well within the construction type and theme of this project, as well as its DIY spirit. It will be a great opportunity to also demo things like scarfing of sections of non-oriented core material into a larger former that behaves as one without the problems of things like translam
If the PR are mounted vertically.
And more weight for a given Fb.
The Fb has nothing to do with the active driver size.
A little driver is not going to get a big, heavy PR doing much useful work at Fb.
Demonstrate that with a valid model if you think it is possible.
I was asking for your opinion on this, which I value, not sure why the stronger words? I don't think I have made any claims there
Lets see, past PR discussions...........feedback, more Sd is better, smaller drivers will need more excursion
Current discussion...........link to a study, less excursion is better
I formed a 'maybe a way forward' and asked for opinions........ not making any claims at all. Have always said that I do not have the expertise to make such calls and requesting help and still moving forward with 'bite and see' if none can be raised
Anyway, leaving that weirdness in communication aside and moving forward
The physical constraints for the target cab dimensions allow for dual passive radiators of up to 10” dia each
Since most of the side panel material gets cut away, l’ll set hard points there. The material left resembles a square ring with a round hole. Lets make those basket structure
The physical constraints for the target cab dimensions allow for dual passive radiators of up to 10” dia each
Since most of the side panel material gets cut away, l’ll set hard points there. The material left resembles a square ring with a round hole. Lets make those basket structure
I realised that if I turn the curved sides into driver hard points, I can try out single and dual 6.5", 8" and 10" passive radiators. Here is the thing, I can then also do things like leave the front blank and fit a 10" PR to one side and 8" active to the other
There is a cute lil 8" with a pancake body uniquely for tiny volumes that I have been eying for a while and might give it a run too. But that's for another time. Next up for this project is creating PR baskets into the curved sides. I'll start with dual 8" PR for the upright v3 model. Curious about the 8"x5" SBA passives. I wonder how one of these would go on the back panel, as that would totally avoid a return of the runaway robot head and develop v4 in conjunction. If a single racer SBA PR can tune this down to 40hz, that will be ideal as that will leave ample space for a roomy electronics bay within the constraints of the base model
Hmm, v4 appears to be the priority to proof test as it ticks all the cosmetic boxes, space allowances as well as upright or floorplay. The importance of developing a decent "porch" floorplay system wouldn't be easily understood by cultures who do not perform folk, religious and celebration music in seated in lotus position. I for one do not enjoy tall amp cabs and PA speakers next to the floor crew. A sub laying under a low stand holding my DJ-202 with the Roland drum machine and sequencer built in plus the Yamaha MG12XU will let all mic'ed performers plug in
There is a cute lil 8" with a pancake body uniquely for tiny volumes that I have been eying for a while and might give it a run too. But that's for another time. Next up for this project is creating PR baskets into the curved sides. I'll start with dual 8" PR for the upright v3 model. Curious about the 8"x5" SBA passives. I wonder how one of these would go on the back panel, as that would totally avoid a return of the runaway robot head and develop v4 in conjunction. If a single racer SBA PR can tune this down to 40hz, that will be ideal as that will leave ample space for a roomy electronics bay within the constraints of the base model
Hmm, v4 appears to be the priority to proof test as it ticks all the cosmetic boxes, space allowances as well as upright or floorplay. The importance of developing a decent "porch" floorplay system wouldn't be easily understood by cultures who do not perform folk, religious and celebration music in seated in lotus position. I for one do not enjoy tall amp cabs and PA speakers next to the floor crew. A sub laying under a low stand holding my DJ-202 with the Roland drum machine and sequencer built in plus the Yamaha MG12XU will let all mic'ed performers plug in