Carbonfiber cabinet.

[matsj]

Have someone here tried to make a cabinet in carbonfiber ?
On friday i´m going to make a visit on a company who makes everything in carbonfiber.
I want to build a sandwich cabinet in carbonfiber and divinycell. I talked to the company last week and they said it would work and the box will be extremly rigid.
2 layer of 600g carbonfiber and 15 mm divinycell and 2 layer 600g carbonfiber will be really good.

Does someone have some ideas on this ?

mats

[richluvsound]

Hi Matz ,


what you propose sounds really interesting indeed. I have been working with
this idea for some time. Are you sure its not GRP . Sounds beyond most
budgets if its 100 % carbon fibre.


When I did the panels for Guido's last speaker I used a slate powder -resin mix . I have a damping layer that I have been playing with using sikaflex .

I have Kevlar I could use . The is UV sensitve though , It darkens in sun light.
Your have a hydrolic press:applaud: You could laminate your own panel to great tolerances .

You have amazing scope with the kit you have. It don't like cold though 15 c needs to be the lowest temp it will cure in.

Rich

[timc]

Think it would be possible to ask a bike factory to make a cabinet form high modulus carbon?

Thinking about prestige manufacturers like Giant, Trek ++

Any idea what it would cost?


-Tim

[BMWCCA]

Think it would be possible to ask a bike factory to make a cabinet form high modulus carbon?Racecar manufacturers are better equipped. They make custom panels all the time. In the current recession you should have quite a few in Europe with a little extra time on their hands now that Honda has dropped out of F1. Maybe Williams or someone like that? Carbon-fibre with an aluminum-composite sandwich, like what Airbus probably uses in interior panels and overheads. Sometimes the sandwich is even honeycombed which makes them nice and rigid. These guys are only 45-minutes from me in Virginia but the parent company is in Europe. I suspect there are many others: http://www.euro-composites.com/en/Seiten/default.html

[timc]

Good point BMWCCA. I just thought that bikeframe manufacturers would be cheaper.

Thoose race car people usually know how to write an invoice.



-Tim

[BMWCCA]

I just thought that bikeframe manufacturers would be cheaper.

Thoose race car people usually know how to write an invoice.Maybe you haven't priced a really nice bike recently? And we know the car constructors are really hurting right now. :D

[Baron030]

Hi Mats

Sound like you are planning on building something that is really going to be light in weight. I have worked with divinycell and it does soak up quite a bit of resin, which can add a lot of weight to your project. If you mix in some hollow glass microsheres with the resin, you can reduce its weight without deducing its strength or its rigidity. But, I would not recommend adding more then 1 part glass microsheres to 2 parts resin by volume.

And speaking of rigidity, if you double the wall thickness you will effectively quadruple its rigidity. So, if you find that your carbon fiber, divinycell, and carbon fiber sandwich does turn out to be too flexible. Don’t make the mistake of just adding more layers of carbon fiber to each side of the divinycell in the hopes of stiffening up the enclosure. You would be better off by adding another layer of divinycell and another 2 layers of carbon fiber. So, what I am suggesting is a composite made up of carbon fiber, divinycell, carbon fiber, divinycell, and carbon fiber.

But, I would think that a well braced carbon fiber, divinycell, and carbon fiber sandwich would be more then rigid enough.

Baron030 :)

[grumpy]

LSR32 did the baffle... IIRC, but not the entire cab. Bang for the buck
decision? Probably. :dont-know

[matsj]

You can get Divinycell in many thickness and stiffnes, but over the phone he said 15 mm would be good.
It´s not cheap with carbonfiber but here in Sweden is mdf not cheap either. 2 speakers will cost around 1200$$ in material.
Rich you can put kevlar in it to get it stiffer to.

The bass box will look like this and there will be a horn and tweeter above it in a separate box:

mats

[matsj]

Yes, we talked about the honeycomb sandwich to. I´ll see on friday when i meet the guys what they says. about it
With 15mm Divinycell and 2+2 layer carbon fiber you can jump on it without problems. I´ll put some ribs in it too.
And YES there will be a Jbl element in it.

mats

[richluvsound]

Hi Mats,

I just did a search on this stuff. its a se. ----- web address . Any hints. I may get off my arse and post that bloody crossoverthing :o:

Rich

[matsj]

Yes Rich, they made the divinycell here in Sweden. http://www.diabgroup.com/europe/opening/e_home.html

The company is 200 km from me.

The crossover would be great.

mats

[matsj]

I talked with the carbon fiber company today about using honeycomb or divinycell.
Honeycomb will be stronger than divinycell BUT all noice from the inside of box will go threw the walls. Divinycell will lowers the noice from inside very MUCH.
And about the divinycell thickness he said 15 mm will be enough for my speakers.
So i´ll use 2x600g CF+ 15mm divinycell + 2x600g carbon fiber. Inside the box i´m going to use some damping body from Swedac acoustic (dc-p500).

To make these cabinets i´m going to bend 2mm steel to the right shape and laminate carbon fiber inside.

mats

[matsj]

One more picture:

The tweeter is 90 degres wrong and all measure is not right yet. And i want the 15" a little bit higher up.
Maybe i shall change the backside of the top.

I have to draw some more.

mats

[timc]

Thats a handsome looking brute Matsj.


What is the estimated cost on a cabinet like this?

Maybe this is what i should get for my own project.



-Tim

[matsj]

Tim around 1200$$ for the carbon fiber + divinycell. Nearly 1000$$ for the 50mm Walnut front.

mats

[jeenie67]

............and the fabric? Mesh? Weave? Powder? I'm in correspondence with a gentleman that purchased 300' of my CAT5 wire. Turns out he fabricates his own CF bike parts; sending me pics of parts in manufacture. I have slowly been replacing most units on my hybrid bike with the material in different forms of composite. I have already developed a plan to fabricate some clone JBL lenses. Just to do it, in CF. There are different forms of this material available. Some requiring a vacuum pump to properly set up the stuff. Some needing an oven to bake it, and some just layered like fiberglass cloth. I think looking at the entire spectrum a wise choice. A pic of my seat in a fabric style, easily made.

[Mr. Widget]

I know it isn't as sexy as aerospace or formula one, but it would seem to me that you might want to consider a boat manufacturer. For a loudspeaker's needs glass fiber in epoxy resin and carbon fiber in epoxy resin should be roughly interchangeable and the cost of building a fiberglass boat is significantly less than a carbon fiber fuselage or formula one body.


Widget

[jeenie67]

...boat maintainence stores (at least by me) sell the cloth in small rolls for hull repairs. Also quarts or gallons of resin. Rolls start at 1' wide to 3' wide. Be creative. Pick up a little of each kind of matt and experiment. I use CF cloth w/ the CF resin (weight for my parts is critical). A mix of both matts might produce the desired result. Any other matt could be laminated into the mix.

[matsj]

After a lot of work i now have a CAD model of my speakers. I didn´t had time to fix the horn and driver yet, but it will come. Some pictures:

mats

[matsj]

If someone have some ideas about my drawings please let me know. I don´t want any mistakes.

mats

[timc]

Have you done any calculation on baffle difraction? What about rounding the edges of the baffle to minimize the transition?

Beautiful work btw.


-Tim

[matsj]

Thanks Tim, no i haven´t had time to make such a simulation.

mats

[jeenie67]

Hi, Just a suggestion; I would be researching the port configuration. Some designers say a 90 or so degree bend somewhere in the tube is beneficial. Thickness of the tube material is another consideration. After all, what is a port but another quasi driver unit. Your basic design, especially the cosmetics are beautiful. I would enjoy having a pair in my office when I do not want to pump my main system up listening to music while I work.

[macaroonie]

Mats this looks like a super project however I would caution you about the solid baffle. A piece of solid that size could have problems. Central heat , warping etc . At the very least you will need to have it in the environment where it will be used for a good few months just to allow the moisture content to stabilise. I would do this in a partially finished state but allow for a final skim thicknessing. You may want to consider laminating this part on to a birch ply backer.
Also it seems a pretty high price. My lumber merchant is about 50% less than that for off saw material.
I also wonder about the cost / benefit of the curved sides in fancy space age materials. Both Meridian ( SL6 & 600 in Aerolam ) and various McLaren offerings ( Carbon fibre / kevlar ) were conspicuous flops as a final product.
The fancy cabinet did not seem to offer any great benefit in either case. What it did do was shove the price up through the ceiling.
If you are pursuing this route to achieve the curve a good hunt arround the industrial suppliers of birch ply will find you pre formed curved sheets.
Crowd called Andersen as I recall.
There is of course nothing to stop you using the weave cloth as a decor outer coating if that is the look you want.
It just seems to me to be a long road with possible benefits but also many pitfalls.

Best regards Mac


http://images.google.co.uk/imgres?imgurl=http://www.preformdirect.com/images/radikey.jpg&imgrefurl=http://www.preformdirect.com/prof1.asp&usg=__ZhpbAi59cPhtAkRmbh9R1emNmNI=&h=233&w=80&sz=7&hl=en&start=71&um=1&tbnid=uvReLncQJy-15M:&tbnh=109&tbnw=37&prev=/images%3Fq%3Dpre%2Bformed%2Bplywood%26start%3D60%2 6ndsp%3D20%26um%3D1%26hl%3Den%26safe%3Doff%26sa%3D N

[jeenie67]

I'd be doing the speaker baffle for that design in solid aluminum. Easy to cut, form, and machine with home power tools. Check out for materials: < @ metal supermarket.com >

[Steve Schell]

Matsj, I have a few random thoughts and a question or two. I am familiar with the properties of carbon fabric, as I use it in the construction of loudspeaker diaphragms.

I am curious as to your reasons for choosing carbon fiber as a speaker cabinet material. Generally in industry CF is used where high strength, and especially light weight are desired properties. Neither of these would seem to be high priorities in a home loudspeaker cabinet. In fact the light weight would be a disadvantage, as a cabinet's inertia helps it to resist motion in response to cone movements. If the external appearance of a carbon weave is important, a layer of carbon fabric could always be applied to another structural material.

The high stiffness of carbon composite would likely move panel resonances higher in frequency than, say, plywood or MDF, and the low mass would move them up further. This can be very good if the resonances are pushed up beyond the passband, as the cabinet will not vibrate if it is not excited at resonant frequencies.

Your renderings of the proposed design are beautiful; very nice work indeed. I might do a couple of things differently. Rather than enclosing your midrange horn inside an upper box, letting it be a free standing sculptural element sitting atop the bass bin would allow it to be larger, with perhaps greater length and a considerably larger mouth size; good things from a performance standpoint. Also, your tweeter could be supported independently and moved back to be time aligned with the midrange driver. I have found this to be very important unless the elements are to be time compensated digitally.

Not saying you should go this direction necessarily, but here is a link to a thread on the Fostex monitors. I would do the midrange horn differently (large and conical flare), but the time alignment achieved in these designs is a good thing.

http://audioheritage.org/vbulletin/showthread.php?t=5229&highlight=fostex+monitor

[matsj]

Thanks for the ideas Steve. All drivers are digitally compensated in time.
The horn is allready bought and ready, i haven´t got the drawings right yet. They are really difficult to draw these.
My choice of carbon fiber is for the strenght, not for the look or weight. I´m going to paint them .
Carbon fiber together with Divinycell makes the box dead so i hope the result will be good.
Marten design use carbon fiber boxes to their "Coltrane" speakers.
About the weight of the speaker, it will be heawy. Horn + driver 43 kg each. 10"=6.5 kg. 15"= 15 kg. Tweeter 1.1 kg

mats

[Mr. Widget]

My choice of carbon fiber is for the strenght, not for the look or weight. I´m going to paint them .By strength I assume you mean rigidity. Actually using a very light and very rigid material does have advantages. Westlake uses a heavy rigid material and therefore must use hundreds of pounds of damping material to achieve a truly non resonant enclosure which they achieve to a better degree than most. Using your much lighter yet rigid material means that you will be able to achieve similar results with far less mass... not at all undesirable.

All that said, as I pointed out before, you will have essentially the same results using glass fiber instead of carbon. The principal difference in this application being a significant cost savings. However it would appear you have made your mind up so go ahead and use carbon. I think you have the possibility of achieving your goal.

As for the design overall, it appears to be very similar to my own speakers. I believe you are even using some of my horns. It appears you are placing the mid horn at approximately 1 meter from the floor as I have, this works out very well. I chose not to place the tweeter above the horn for aesthetic reasons, but I did try it above... sonically there was very minimal difference in sound. I am not sure what the woofers you will be using are, but I think you will have a very nice system when you are done. It will be quite large, but I guess you are OK with that. ;)


Widget

[matsj]

I think less weight=less damping. Yes widget it´s one of your horns ( can you help me with the CAD). I have around 1070 mm to centrum of horn.

mac: About my walnut baffle i´m going to use walnut "laminated" side by side planks not regular kitchen wood. ( " i don´t know the right word")

mats

[macaroonie]

Single stave walnut

[Mike Caldwell]

Hello

There is a large touring sound company called Sound Image that build all of there proprietary cabinets from carbon fiber.
http://www.sound-image.com/index.php

Their division that builds the cabinets is called Audio Composite Engineering or something like that.

I've head their systems in use at a a few shows, they sound good.

[badman]

One point that's only been poked at: you're using the rounding where it's not going to make a whole lot of difference. Rounding the sides is a plus, but a MUCH bigger plus is to do large edge roundovers (think 4-6" radius). Not only do these reduce the appearance of the cabinet, much more importantly they smooth the edge diffraction so that you've got a fairly smooth transition to 4pi radiation with the baffle step (and smoothed diffraction artifacts above that), as well as eliminating the edges as secondary sources (better imaging).

For calculating the baffle width, just pick a width halfway along the roundovers and treat it like a flat baffle. Not perfect but close.

[matsj]

I have done some more drawings on my carbonfiber box. The front baffle aint right yet, i can´t deside what to do with it.

mats

[matsj]

Some other wiews.
I´ll start building these this weekend. I´m going to make a model in 1:1 in Mdf and cellular plastic.

mats

[pos]

that is VERY impressive!
Do you have a thread about the design (drivers, crossovers, etc.) ?

[matsj]

Pos: No not yet. I´m not a designer so i have tried to make something i like. The cabinet is a little wide (850 mm) but it must be that for the double Jbl W1500h.

It´s going to be fully active driving, with a computer as unit and crossover.
The computer will use 2 Lynxstudio TWO B soundcard: http://www.lynxstudio.com/product_detail.asp?i=12
Diy amp for the tweeter and horn driver. 2 Crown K2 for the W1500h. The amp choice for mid woofer isn´t desided yet.

mats

[Mr. Widget]

The cabinet is a little wide (850 mm) but it must be that for the double Jbl W1500h.I can't imagine you would ever need two W1500Hs per side... I use a very ;) similar system currently with a single Sub1500 per side and they have never run out of steam... beyond that if you already have four W1500Hs and love lots of bass, you'd be better served by locating the second pair in separate cabinets so that you can better integrate the system in your room.

All that said, "I´m not a designer so I have tried to make something I like." is a very rational approach... if you really want two 15" woofers per side, then go for it.


Widget

[grumpy]

Might see if vertical grain on the face slims up the design, visually :)
... a distinctive design thus far.

[Uncle Paul]

Based on Mats' usual craftsmanship, these should be quite stunning. I hope their audio impact matches the visual.

I do hope their Dalek like appearance doesn't send Ian Mackenzie running for the Tardis...

[pdemondo]

The drawings are excellent. Very attractive speaker.

[matsj]

grumpy: as i said before the baffle ain´t right yet, the grain should not be vertical. I have some ideas but i´ll wait untill the box is ready.

Widget: Yes,i have copied your speakers. And added 2 15" for my big room.

pos:
Tweteer: Tad ET-703.
Horn: Tad TH-4003.
Driver: Tad Td-4003.
Mid: Tad TL-1102.
Bass: Jbl W1500H.

mats

[matsj]

Correction: The grain on the wood shall be vertical :o: not horisontal. My mistake.

mats