Ronald, do you think your separation issue was mainly due to the height? Would expect issues with a monitor or even floorstander that is doweled, glued, and clamped properly? I also like the idea of screwing each layer down into the next. I use deck screws in all of my cabinet work and they are terrific.
That's a hard question to answer 
...
I have read it as a solution in one of the horn threads, let me look it up a little later... Sadly I can't predict what will happen, aside from the knowledge the wood stack will expand and contract over time. That's the beauty of the Magico speakers where the stack is allowed to move.
I had to try and keep the wood finish after all that work I did on the stacks...
The original plan was an epoxy outer layer though. In the end it's a good thing the cracks happened so I could cut and dampen the enclosure before the epoxy layer, instead of facing the problem of the outer layer coming loose over time had I done what I planned originally. I'll add some links later...
...I have read it as a solution in one of the horn threads, let me look it up a little later... Sadly I can't predict what will happen, aside from the knowledge the wood stack will expand and contract over time. That's the beauty of the Magico speakers where the stack is allowed to move.
I had to try and keep the wood finish after all that work I did on the stacks...
The original plan was an epoxy outer layer though. In the end it's a good thing the cracks happened so I could cut and dampen the enclosure before the epoxy layer, instead of facing the problem of the outer layer coming loose over time had I done what I planned originally. I'll add some links later...
Here's a far out idea, what about placing gaskets between each plywood layer, hold it all together with long bolts, and not glue them together? Not only would this address the expansion/contraction issue, but it would also make it somewhat modular if internal volume would ever need to be changed. Something tells me this won't work...
Not what I would do ... I found my recipe... I decided to share both the successes and failures so others could learn from my experimental work as well as myself.
Here's an example of a stacked construction without trough bolts, but still experiencing the same problems I had: barackuda's teardrop enclosure
The horn stacking solution was found in this thread: http://www.diyaudio.com/forums/mult...x-turned-plywood-bass-horn-2.html#post4467063
So member JLH is the one who suggested that solution. I can only point you in that direction, I cannot vouch for it.
Somewhere within this huge thread of mine is a picture of a speaker that used your proposed gasket solution. (really!) I know because I was the one that posted that picture.... let's see if I can hunt that one down... fingers crossed!
I know it was a commercial speaker, I showed it on here as a possible solution, not my chosen solution.
... I found my recipe... I decided to share both the successes and failures so others could learn from my experimental work as well as myself.Here's an example of a stacked construction without trough bolts, but still experiencing the same problems I had: barackuda's teardrop enclosure
The horn stacking solution was found in this thread: http://www.diyaudio.com/forums/mult...x-turned-plywood-bass-horn-2.html#post4467063
So member JLH is the one who suggested that solution. I can only point you in that direction, I cannot vouch for it
. Somewhere within this huge thread of mine is a picture of a speaker that used your proposed gasket solution. (really!) I know because I was the one that posted that picture.... let's see if I can hunt that one down... fingers crossed!
I know it was a commercial speaker, I showed it on here as a possible solution, not my chosen solution.
Yeah, I had a feeling that might not be the optimal solution, I would not bet that It would properly maintain its seal and structure. I will study your feedback thoroughly and follow your advise for my first endeavor -I do like your thinking and respect your experience and results.
Interestingly, on another thread that I started to discuss my project there were a few people that were negative about translam construction. I felt their arguments didn't really hold water. One comment regarded that it wastes material. If I am making the investment of premium drivers and time in this type of project, I believe I can sacrifice some scrap plywood! Another raised a concern about rigidity which made no sense to me, translam appear to me to be a naturally more rigid construction and also gives the flexibility of non parallel internal surfaces -unlike cube boxes. Plus I love the way it looks!
Interestingly, on another thread that I started to discuss my project there were a few people that were negative about translam construction. I felt their arguments didn't really hold water. One comment regarded that it wastes material. If I am making the investment of premium drivers and time in this type of project, I believe I can sacrifice some scrap plywood! Another raised a concern about rigidity which made no sense to me, translam appear to me to be a naturally more rigid construction and also gives the flexibility of non parallel internal surfaces -unlike cube boxes. Plus I love the way it looks!
I saw your thread this morning, I read those comments... I'm certainly not the first one to do this type of construction, sadly also not the first one to get in trouble with cracks developing. My use of ply was not all that wasteful at all, I figured one open side could save me a ton of material (as a figure of speech).
In the end, you'll need to convince yourself if it is worth it to you. It was to me, I got pretty much the same advice you are getting now. I followed my own gut feeling, plus I would have hated to make rectangular speakers...
Form follows function, that disregarded any hard corners for my ideals... I do believe in preventing diffraction as much as sanely possible, not arguing my design has big enough round overs though, but it is one reason to like the Magico Mini's. Plus I'll state it once more: not having the baffle fixed to the stack like they did was a smart move to prevent extra stress on the expanding/contracting stack of ply, they did have experience with ply/alu enclosures before building the Mini's...
Do you notice the former bigger ones did use smaller divided stacks contrary to the Mini?
The Mini is the one I like though... with that round outer shape...
Another stacked construction and awesome read was this one:
M-21 Giveaway Build Pics - Page 24 - Home Theater Forum and Systems - HomeTheaterShack.com
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Wow, those are pretty cool. It looks like Isophon morphed into Gauder Acoustics. They make some pretty interesting stuff:
Gauder Akustik - BERLINA-SERIES
This is their $250K statement speaker:
Gauder Akustik - Berlina RC11
The rib construction is pretty interesting. But I'm seeing maybe $20K in Accuton drivers and an impressive box that is really just a bunch of MDF and aluminum cut exactly along the lines of what we're discussing here. Am I crazy to think I could build something comparable with an active crossover and DSP that actually might be even better than this thing for about 10-15% of this insane price? (yes, I need to work my way there and crawl before running marathons, but...)
Gauder Akustik - BERLINA-SERIES
This is their $250K statement speaker:
Gauder Akustik - Berlina RC11
The rib construction is pretty interesting. But I'm seeing maybe $20K in Accuton drivers and an impressive box that is really just a bunch of MDF and aluminum cut exactly along the lines of what we're discussing here. Am I crazy to think I could build something comparable with an active crossover and DSP that actually might be even better than this thing for about 10-15% of this insane price? (yes, I need to work my way there and crawl before running marathons, but...)
I can't understand a speaker at that price point using MDF... I'd expect something like Pantzerholz at that price point (lol)
I'm willing to offer you my speakers for $250K, it is my statement speaker
It comes with complete history and (in room) measurements too! In the first post are two reviews linked, hopefully more to come.
I'm willing to offer you my speakers for $250K, it is my statement speaker
It comes with complete history and (in room) measurements too! In the first post are two reviews linked, hopefully more to come
.I can't understand a speaker at that price point using MDF... I'd expect something like Pantzerholz at that price point (lol)
I'm willing to offer you my speakers for $250K, it is my statement speaker
It comes with complete history and (in room) measurements too! In the first post are two reviews linked, hopefully more to come
Dude, I'd buy them today, but I'm just committed to the build my own thing!
I apologize for the interruption but may be I can answer your earlier question. I followed this thread from the beginning and must admit this is the best diy speakers project that I've seen so far. Kudos to Ronald!
According to this document (see page 23, middle) the thickness variation of plywood can be around 0.3-0.4% per 1% moisture change within the range of moisture content of 10 - 27%. So for each meter of stacked ply 1% moisture change will result in 3-4mm change in length. On a 2+ meter long enclosure it will approach 1 cm per 1% moisture change which is a lot. Now the steel rods which hold the towers together (and are glued throughout if I remember right) do not swell/contract with moisture and thus lead to cracking of the enclosure on tension (when ply shrinks and the rods don't). On ply swelling it has not so dramatic effect since steel rods are way stronger than ply and will just compress it. Now you can repeat it for your dimensions and see if it is a problem. So the problem with the towers was the fact that the rods were glued to the ply and thus pulled it apart when the ply shrank.
Note also that along the grain ply elongates by only 0.015 % per 1 % increase of moisture, so it should be a non issue for a typical size enclosure.
Regards,
Oleg
Back to the building questions. I believe we touched on this, but I'm still unsure about how to determine the wall thickness. Would thicker be better? Would that not create both increased rigidity and more glued surface for improved structural solidity? Am I missing something about making them too thick -rigidity seems to be in favor among the super speaker makers like Magico and YG.
And thank you again for all the terrific feedback!
And thank you again for all the terrific feedback!
Yes, Magico was definitely on that path of "thicker is better".
In my own endeavours I figured I had to count in the fact that my speaker enclosure was meant to withstand 20 to 20000 Hz. But every little speaker only had to do a little part of that.
There are trains of thought about thin walled speakers too, like the work of Harbeth for the BBC.
Personally I also liked the idea of some static weight in the enclosure itself opposing the moving mass of the drivers.
This is one of the questions that has been debated a lot. I believe in rigid enclosures, for a 2 or 3 way like you are planning I would opt for the Geddes type of bracing (rods with planned/build in damping). Personally I would use thicker walls on your proposed speaker plans in comparison to my own. One or two drivers do all the SPL while in my case each driver does next to nothing... Together though they can produce massive SPL levels.
My 'moving mass' of one complete speaker (25 drivers) is about 60 grams(!) The enclosure weight is more than 65 Kg. What do your proposed driver cones weigh?
The thin walled enclosure theory is cute, but didn't do it for me. I can't help but think it will colour the sound in the bass department. Well damped rigid enclosure walls did make more sense to me. I also have a damped baffle construction etc. It worked for me.
In my own endeavours I figured I had to count in the fact that my speaker enclosure was meant to withstand 20 to 20000 Hz. But every little speaker only had to do a little part of that.
There are trains of thought about thin walled speakers too, like the work of Harbeth for the BBC.
Personally I also liked the idea of some static weight in the enclosure itself opposing the moving mass of the drivers.
This is one of the questions that has been debated a lot. I believe in rigid enclosures, for a 2 or 3 way like you are planning I would opt for the Geddes type of bracing (rods with planned/build in damping). Personally I would use thicker walls on your proposed speaker plans in comparison to my own. One or two drivers do all the SPL while in my case each driver does next to nothing... Together though they can produce massive SPL levels.
My 'moving mass' of one complete speaker (25 drivers) is about 60 grams(!) The enclosure weight is more than 65 Kg. What do your proposed driver cones weigh?
The thin walled enclosure theory is cute, but didn't do it for me. I can't help but think it will colour the sound in the bass department. Well damped rigid enclosure walls did make more sense to me. I also have a damped baffle construction etc. It worked for me.
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I apologize for the interruption but may be I can answer your earlier question. I followed this thread from the beginning and must admit this is the best diy speakers project that I've seen so far. Kudos to Ronald!
According to this document (see page 23, middle) the thickness variation of plywood can be around 0.3-0.4% per 1% moisture change within the range of moisture content of 10 - 27%. So for each meter of stacked ply 1% moisture change will result in 3-4mm change in length. On a 2+ meter long enclosure it will approach 1 cm per 1% moisture change which is a lot. Now the steel rods which hold the towers together (and are glued throughout if I remember right) do not swell/contract with moisture and thus lead to cracking of the enclosure on tension (when ply shrinks and the rods don't). On ply swelling it has not so dramatic effect since steel rods are way stronger than ply and will just compress it. Now you can repeat it for your dimensions and see if it is a problem. So the problem with the towers was the fact that the rods were glued to the ply and thus pulled it apart when the ply shrank.
Note also that along the grain ply elongates by only 0.015 % per 1 % increase of moisture, so it should be a non issue for a typical size enclosure.
Regards,
Oleg
Thanks Oleg, I can agree with the above based on what I experienced. The option to saw my enclosures in to 25 separate parts was my way of dealing with it, as the wood will never completely stop expanding/contracting...
The remaining stacks are small, and held in place within a rigid epoxy/matt shell. The rods which were glued in place are still in there...
True... it hurt! But I learned a lot, one of the things that I learned was patience...
Don't rush into a solution, think it trough... and more important: don't give up at the first sign of trouble!
But to JRSystems I have to say: if you are willing to do a translam construction by hand using a router, you better be a little crazy!
Don't rush into a solution, think it trough... and more important: don't give up at the first sign of trouble!
But to JRSystems I have to say: if you are willing to do a translam construction by hand using a router, you better be a little crazy!