OK, so the metal stays still to .0001 units accuracy, its still glued TO THE WOOD!
If the wood contracts as it dries out (which it will do as there is a lot of surface area exposed AND its thin in section AND all open grain), what's the metal going to do?
It will stay put and the wood WILL break at its weakest point.
Another thing, the rods, after they have been tightened in the build phase, will be under quite a lot of torsional stress, this is because one end started out fixed after the first 'stacklet' was built up and bonded.
Even with 'rubbery' glue round the rods, they will still retain and maybe continue to 'wind up' more as the build goes / went on.
All these 'Stresses' could be root cause - or maybe one thing on its own.
All I know are basic Engineering principles learnt and garnered over 20yrs working as some form of Engineer.
And basic physics learnt at school.
An often quoted phrase by engineers: 80% of job time is thinking about it, the other 20% is making it (right first time).
If the wood contracts as it dries out (which it will do as there is a lot of surface area exposed AND its thin in section AND all open grain), what's the metal going to do?
It will stay put and the wood WILL break at its weakest point.
Another thing, the rods, after they have been tightened in the build phase, will be under quite a lot of torsional stress, this is because one end started out fixed after the first 'stacklet' was built up and bonded.
Even with 'rubbery' glue round the rods, they will still retain and maybe continue to 'wind up' more as the build goes / went on.
All these 'Stresses' could be root cause - or maybe one thing on its own.
All I know are basic Engineering principles learnt and garnered over 20yrs working as some form of Engineer.
And basic physics learnt at school.
An often quoted phrase by engineers: 80% of job time is thinking about it, the other 20% is making it (right first time).
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Wow, take it easy... All I was saying: no need to split the aluminum.
All other things you mentioned I have already acknowledged.
I spend half a year building it. And I did spend quite some time thinking about it.
And reading about it, even asking for opinions of others etc.
All the blame is on me, I already said that too. So what are you wound up about?
I am learning here, how about you? I am sorry I didn't get it right on my first stack
of 130 pieces of ply.
All other things you mentioned I have already acknowledged.
I spend half a year building it. And I did spend quite some time thinking about it.
And reading about it, even asking for opinions of others etc.
All the blame is on me, I already said that too. So what are you wound up about?
I am learning here, how about you? I am sorry I didn't get it right on my first stack
of 130 pieces of ply.
I just looked over this thread for the first time this morning and am sorry to hear what happened after all your hard work, but agree that the threaded rods are the problem, it sounds like you assembled the stack in the summer months, the peak of the humid season so the wood is going to want to continue shrinking until sometime in the spring when the process will start to reverse. Just thinking out loud here, i am going to assume retorking the rods is out of the question but if where possible early spring would be the final time to do this. As you probably know, you may find that the mounting holes on your front aluminium baffle will be miss aliened by the spring if that machining was done in late summer
I guess there is no right time of year only picking the lesser of two evils, shrinking causing fractures or expansion causing exessive pressure
I don,t know of any finish that will stop wood movement only slow it slightly
I guess there is no right time of year only picking the lesser of two evils, shrinking causing fractures or expansion causing exessive pressure
I don,t know of any finish that will stop wood movement only slow it slightly
Wow, take it easy... All I was saying: no need to split the aluminum.
All other things you mentioned I have already acknowledged.
I spend half a year building it. And I did spend quite some time thinking about it.
And reading about it, even asking for opinions of others etc.
All the blame is on me, I already said that too. So what are you wound up about?
I am learning here, how about you? I am sorry I didn't get it right on my first stack
of 130 pieces of ply.
I missed the relevant bits, so the apology is from me to you.
I learn lots from these and other forums.....
I leant from this thread that 8ft / 220cm towers could be very prone to some sort structural grief. I will never build such an array, the whole concept 'does not thrill me', but IF I did, it would be in sections - I leave nothing to chance, cos if it will go wrong it WILL go wrong for ME
I have learnt (even though I know already) that plywood is quite unstable stuff and, harbouring thoughts of a curve backed cabinets, has made me rethink everything regards the doing bits of a future project.
It also made me re-evaluate several very key areas in 2 model race planes I'm slowly working on regarding structural alignment / integrity while in operation (Very hot vibrating bits of metal distorting wood ) - the dangers here are not a loss of money or time, but the potential maiming people...... or Killing them!
It also got me thinking about how much the foam portion of a surfboard alters in shape when glass is laminated on - given that all cloths shrink a bit when 'Fixatives' are added.
Not bad going since my last post
I really do applaud your effort and was really quite gob-smacked and heartbroken when I saw 'that picture' (makes lots of signs to ward off the evil Murphy aka Sod).
Transplant me into your shoes - I'd be measuring a 'clean' portion of the break day to day to see if the structure is still shifting
Fyi, I wasn't wound up - I realised after I put my head down to sleep that my post might be construed as 'angry' - far from it, it was just me being me, I have a tendency to tap out what I think instead of what should be said, there are other DIY audio members who have a similar problem.
If I did have a problem with anybody, it sure as heel wouldn't be aired for the general forum membership to read!
rapt following
I have visited diyaudio as a guest many times but it has been reading your thread that finally insired me to join so it is only fitting that my first post is here. Although I have never owned a line array speaker they have intreged me as the only time that I have ever heard proper 3D stereo imaging from a digital source at a hifi show was through this type of speaker (sadly I can't remember the make). I imagine that your design being floor to ceiling is not only going to image like a dream, it's going to image like reality. The last time I read your thread was before the cabinet split (I've had wifi troubles). My heart goes out to you. I am sure that showing the skill, hard work and patience that you have already put in you will overcome this set back.
In your posts before the split occured you said you were about to start testing internal damping materials. Your design has a solid cabinet with non parallel sides and mechanisms to break up the rear sound waves, the wiggly surface and vented horiontal baffles. In my experience a cabinet of this design doesn't nessesarily need any internal damping. The addition of damping materials can softens dynamics, clarity can be veiled and the sound stage shrunken. When you do start your testing my I suggest that one of the damping combinations considered is none at all.
Good luck with overcoming your current problem. I look forward to your next step.
I have visited diyaudio as a guest many times but it has been reading your thread that finally insired me to join so it is only fitting that my first post is here. Although I have never owned a line array speaker they have intreged me as the only time that I have ever heard proper 3D stereo imaging from a digital source at a hifi show was through this type of speaker (sadly I can't remember the make). I imagine that your design being floor to ceiling is not only going to image like a dream, it's going to image like reality. The last time I read your thread was before the cabinet split (I've had wifi troubles). My heart goes out to you. I am sure that showing the skill, hard work and patience that you have already put in you will overcome this set back.
In your posts before the split occured you said you were about to start testing internal damping materials. Your design has a solid cabinet with non parallel sides and mechanisms to break up the rear sound waves, the wiggly surface and vented horiontal baffles. In my experience a cabinet of this design doesn't nessesarily need any internal damping. The addition of damping materials can softens dynamics, clarity can be veiled and the sound stage shrunken. When you do start your testing my I suggest that one of the damping combinations considered is none at all.
Good luck with overcoming your current problem. I look forward to your next step.
No harm done here . I have this build up here to learn. It would have been easy for me not to share this mishap. But I figured it would benefit more people to know this can happen with the wrong choices. Never thought it would cause such a stir though.
Still looking to gain knowledge how to do this shape and size without something like this happening. Would love to know all construction details on the older big Magico speakers that were made from stacked ply. I learned about them after I had this idea all worked out.
Would love to try composites the next time. Long ago I did do some fiber glassing but I have zero experience with epoxy. From what I read about it, it doesn't shrink when curing. But the curing temperature is something to keep in mind!
An all aluminum tower makes sense too. But not as easy to get the shape I want AND be able to afford it.
Good or bad, I intend to share my path here.
. I have this build up here to learn. It would have been easy for me not to share this mishap. But I figured it would benefit more people to know this can happen with the wrong choices. Never thought it would cause such a stir though.Still looking to gain knowledge how to do this shape and size without something like this happening. Would love to know all construction details on the older big Magico speakers that were made from stacked ply. I learned about them after I had this idea all worked out.
Would love to try composites the next time. Long ago I did do some fiber glassing but I have zero experience with epoxy. From what I read about it, it doesn't shrink when curing. But the curing temperature is something to keep in mind!
An all aluminum tower makes sense too. But not as easy to get the shape I want AND be able to afford it.
Good or bad, I intend to share my path here.
Thanks for that, and welcome!
The start of my experiments will be an empty chamber. That will be the reference measurement. I somewhat expect good things from simple fiber glass insulation material. Hoping even it will make the enclosure seem bigger than it is without stuffing too much.
Measurements would be able to proof that I hope. One thing I do hope to achieve from using damping materials is stopping the back wave coming back trough the cone. I will add no more than is needed, as little as possible.
That is why I am intrigued by the Twaron Angel hair. The claims made are way less material is needed for the same effect as lambs wool. But it would have to work for the entire spectrum. So far Fiber glass insulation seems up for that task from all the information and tests I have found around the net.
Another learning curve I guess... What do I look for in my measurements
.My guesses up front:
- smooth frequency response
- extended bass performance
- better waterfall (faster decay)
Hey wesayo,
Mechanical engineer here. Your speakers are beautiful. Stick with it and you'll not regret it. Here's my opinion. It's free, so you know what it's worth. You already know the cause was the wood contracting. If it was me, i'd remove the rods (if possible and replace them with a smaller diameter rod that can float insode the stack of plywood. Bolt them at the bottom and preload them with a fender washer and some heavy springs at the top so they can maintain pressure on the stack and still move freely with the stack's expansion and contraction.
You might be able to remove the existi g rods by either placing a fender washer on the top and using a nut to pullthem out or by welding a nut on the threaded rod (or using a nut and jam nut) and unscrewing them from the stack.
Good luck and stick with it. When you succeed it will pay off in triplicate.
Mechanical engineer here. Your speakers are beautiful. Stick with it and you'll not regret it. Here's my opinion. It's free, so you know what it's worth. You already know the cause was the wood contracting. If it was me, i'd remove the rods (if possible and replace them with a smaller diameter rod that can float insode the stack of plywood. Bolt them at the bottom and preload them with a fender washer and some heavy springs at the top so they can maintain pressure on the stack and still move freely with the stack's expansion and contraction.
You might be able to remove the existi g rods by either placing a fender washer on the top and using a nut to pullthem out or by welding a nut on the threaded rod (or using a nut and jam nut) and unscrewing them from the stack.
Good luck and stick with it. When you succeed it will pay off in triplicate.
The fun part is all the different opinions... that's why I decided to just wait and observe for now. Just stick to finishing the rest of it. But making sure to not permanently attach anything to the enclosure for now. My goal for this structure remains to have it as one big structure. Future builds may be different .
Hard to do with the spacing between the separate speakers! Not much room for a seal that way.
The mounting holes and even the embedded nuts have the "give" needed to allow some play.
The biggest variable for me was how much play do I need? I had no clear answer there.
.Hard to do with the spacing between the separate speakers! Not much room for a seal that way.
The mounting holes and even the embedded nuts have the "give" needed to allow some play.
The biggest variable for me was how much play do I need? I had no clear answer there.
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