Honeycomb, Carbon Fibre and composites for flat panel speaker building: help required please

Sarel.wagner

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Anybody on here versed in these things? I can Mig and Tig (not to well but heck yes) use a mill and lathe and do woodworking, Composites not. I know of AMT and others, but nothing of the process and very little of the materials. I need help with this please. Any online resources, or anyone working with this, please reach out. This is for my flat panel speaker experimentation I want to start doing soon.

I talk about that in my It's a bliss to know nutting thread on here. I do not want this to be stuffed inside that thread for visibility sake. So any bites then?

Groetnis
 

DACMan1

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Ok, ignoring my opinion of panel speakers; AMT used to have good articles on vacuum bagging. I can't seem to find them anymore. A good option would be their Composite Workshop.

Aside from that, it is simple - especially since you already have a vacuum pump all you need is the consumables and some equipment from AMT.

I will try and compile something later.
 

Shonver

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Anybody for any advice please?

Groetnis

Did you explore those links? Nobody here will be able to tell you specifically how to do what you need, but the fundamentals are universal. You will have to develop your own process. An alternative is to source the parts from OEMs.
 

Sarel.wagner

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Yes I did indeed. The materials I am about to explore are expensive. I do not want to learn by making mistakes, when with some guidance that can be avoided. I did look at the AMT classes as well. I would think that a person that works with composites like Nomex and other honeycombs and making laminates may have insights into best practises learned over years. Hopefully they will share. At this point I do not know basic things yet.

Groetnis
 

Sarel.wagner

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There are a lot of videos in the link, have watched some of them already. Things I need to find out about are what properties will change when for example adding skins to honeycomb vs a foam core. I do appreciate that nobody will tell me what to do, that is not really what I am looking for. If there are good books on the subject, that will help to.

I need to not only find the craft practises for things like what epoxy to use to be compatible to what materials (AMT said they will help with that) but also how to go about bonding a skin on honeycomb. That process will likely differ from bonding a skin to a foam core etc.

Groetnis
 

Sarel.wagner

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And yes the links has now lead me down another rabbit hole ;) seems to me, because I do not know all the terms used, I was searching for the wrong stuff. managed to find some relevant info already....

groetnis
 

Air

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Hi Sarel, I am busy with my 3rd iteration of a design in composite material. My advice based on my experience is to get your design up and running with conventional material, probably mdf and then when you are sure you have all boxes ticked by all means translate t then to a composite structure. Vivid audio did the same, basic traditional material first.

If you going to do a composite structure, get the mould 100% correct and this in my world means to machine it from aluminium first. This way you get the correct tolerances and a great finish. You can also make sure there is as little trimming as possible needed on the final moulded structure. Trimming is both expensive and not so easy with carbon and a Nomex honeycomb core. Not very accurate. A good mould would incorporate all cut out for drivers, port etc. This is for example is my mould for the port. I can customise it depending on the speaker.

As for the layup(carbon and whether it would be unidirectional, woven and the density or Glas or Kevlar etc), you need to decide the format and the core material. Nomex honeycomb, that I used is very expensive and not always readily available in small supplies. Foam might have better damping at the cost of rigidity but increasing the core could once again offset that problem. I would not rule out Balsa as a core as well if the radii is not to much and only bend in 2 directions. Carbon don't work well with tight corners as well so keep those radii friendly.

A vacuum-bag and an autoclave produce the best results for sure but once again it increases the cost.

In the end it depends on whether this project is a once-off or a tooling for a short or long production lineup. Also be clear on your design goals. Ask yourself the question, why would you like a Carbon structure and answered that with absolute clarity. If you plan to build one, I would not go this route but rather skin the cat in the other ways possible. Getting and holding the attention of experienced suppliers are tough... doing it yourself.. not so if the structure is large like a speaker

Hope these random thoughts based on my journey of 8 years or more helps
 

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Sarel.wagner

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@Air Thank you Sire. Now those are the lessons and experience that is invaluable. Thanks for sharing!

The panels I need would most likely be flat and simple, maybe eventually 1m2 or so in size. To start experimenting they will be much smaller than that. Things I need to figure out is the core and skin layers impact on flexing and vibrations within the panel. Also the thickness of the core and skin combinations on the panel performance. There must be enough damping, but not so much to kill all vibrations and flexing. Also I do not even know if this type of panel will be better or worse for what I have in mind, time will tell I guess.

Groetnis

Groetnis
 

Shonver

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You may not be aware of this, but quite often a brainwave comes along that may seem novel to the thinker, but turns out to be a well-explored avenue. My recommendation is to try and get access to a university's library. From there you can access countless engineering white papers. Materials for audio applications have been extensively researched. Watch the loudspeaker market and you'll see various new materials touted as the next best thing, but only turning out to have their own set of cons. (Hint: there must be a reason why "paper" keeps popping up in various forms!). To get to my point: materials technology is a science unto itself and to develop a material that will serve your purpose starting from scratch may prove to be both a lengthy and costly venture. And that is just one component of your transducer.

However, if you want to dive right in, look at getting samples of double-skinned laminates ranging from the hollow-cored types such as honeycomb through to solid foam core. Implement a measurement system that will be able to give you objective scores by which to compare materials. Once you have these results you may have a better understanding of the trade-offs offered by the respective materials.
 

Sarel.wagner

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Very good advice, note taken. I am aware of prior work in this regard and between patents and other research, I have loads of reading still, even thou I have been reading up on the loudspeaker research for quite some time. Also I do have access to IEEE papers and have perused a number of them already and have some books on some of these subjects. Composites till now, nada. The experimentation, from what I have been able to find, will mostly not replicate what was done already, well I hope so. I have not seen nor read everything on this so might later find out I am still Johnny come lately, oh well then.

Thank you for sharing, I am here to learn.
Groetnis
 

henkveza

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Môre Sarel, here are some books I picked up at Exclusive Cresta several years ago.

I myself am working on a fibreglass speaker project, but not for a flat panel application.

If you consider that Magnepan and others use MDF exclusively, that might be the better choice.

Don’t let that deter you from leaening. I attended the AMT class several years back, and that opened my eyes to the possibilities. I can recommend it for sure.

From all my research on flat panel technology, there are some wood types that can give you an advantage e.g. Mahogany, buy MDF seems to be a practicle approach for most builders.

I also encourage you to follow :


For more information on DIY panel speakers.

Have fun and let us know once you made progress.

Groetnis
 

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Sarel.wagner

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After seeing the books Henveze posted, thank you man, managed to track down a few practical guidance books on how all this malarkey works. Hoping I can wrap my head around this, no pun intended. Will post up those tiles later. Also tracked down a long lost friend that works in aerospace with composites all day every day. Completely forgot that is what he does, embarrassing…. 🤦🏻‍♂️

Groetnis
 
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