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Old 16th October 2010, 07:14 PM   #761
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Quote:
Originally Posted by andyjevans View Post
using 4mm aluminium as a baffle, bolted on to the wood underneath. Changing the aluminium front plate would allow for trying out different units if the cutout behind were generous. what effect would this have on sound? It would be stiff, of course.
Something i've wanted to try for sometime. I've got the aluminum, and the shop next to Chris' does waterjet cutting so sometime

Quote:
bamboo. Looks nice and available as worktops for instance, as well as flooring
A wonderful material. There are a range of products. The stranded outer, cored plywood is by far the stiffest (and very dense). I've a pair of Fonken & a pair of dMar-Ken7 awaiting drivers in this last. Not cheap stuff, but with care in construction nothing but a clear finish needed.

Chris has made comments in other threads on construction "issues"

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various plastic laminates. High-density polyethylene HDPE for instance or Tufnol - see 20mm - Direct Plastics Online
That looks interesting -- calling it a laminate is a bit of a stretch (i consider a laminate to be used like a veneer -- a good plastic laminate, inside & out, can go a long way to stiffening a box panel. Like Corian or other solid surface plastics it may have some practical issues (Chris?). We have discarded as a box materialCorian except for top & bottom instead of veneer.

Be nice if the specs were in a comparable format.

ASTM D 3043 Method D Flexural Strength (MOE/MOR)
  • ¾ inch thick, 1-ply, Edge Grain: 179 MOE/11,371 MOR average
  • ¾ inch thick, 3-ply, Cross Core: 148 MOE/9,109 MOR average
  • ¾ inch thick, 3-ply, Cross Core Strand: 268 MOE/14,762 MOR average

Carp Brand TUFNOL Sheet
  • Tensile strength 68 Pa
  • Young's modulus 6.5


Quote:
sound deadening Green Glue as a filler between layers
I've seen lots of discussion on this already (here and on stereonet.au). Geddes doesn't think it as good as it should for constrained layer construction

Thre constrained layer is very effective, but dramatically complicates a build.

dave
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Old 16th October 2010, 07:16 PM   #762
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Quote:
Originally Posted by andyjevans View Post
This is what I was thinking of doing. Did you put any material between the alu front and the MDF or was it just bolted straight on? Did the alu plate cover the whole front or just round the speaker units?

andy
Just bolts so far but I may glue them later. My idea is that the dissimilar materials damp each others natural resonance - and it seems to work well.

This is still work in progress - I'm thinking that I will try a separate cab for each driver - but I attach a pic for progress thus far . . .
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Old 17th October 2010, 06:13 PM   #763
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I had a go with solid beech for subwoofers and have been blown away with the stiffness of the material. So much so they're not braced AT ALL!

They look damn great too. Some of you may have seen these images elswhere as I've been trying to sell them and messed around loads with it LOLOL.

Material is 40mm and 29mm thick
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File Type: jpg 000_0017.jpg (804.2 KB, 83 views)

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Old 17th October 2010, 09:22 PM   #764
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Originally Posted by mikelm View Post
Just bolts so far but I may glue them later. My idea is that the dissimilar materials damp each others natural resonance - and it seems to work well.

This is still work in progress - I'm thinking that I will try a separate cab for each driver - but I attach a pic for progress thus far . . .
I love the look of this, very tasty looking

Ive been thinking about making a laminate of some undecided wood, perhaps aluminium plate, and an acrylic or something, maybe nylon, maybe finishing with glasstape and resin on the inside, and wondering if it was worth persuing. After seeing this project, i think i should definately give it a try.
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Old 18th October 2010, 03:36 AM   #765
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Originally Posted by mondogenerator View Post
I love the look of this, very tasty looking
Thanks, when they're finished the ali will be covered with cork - I heard cork was a good choice as a outer covering because of the uneven surface.

The difference between these composite baffles and original 1" MDF baffles that came with these cabs is quite significant so I think it's well worth experimenting.

My top two choices would be what I did here with ali & mdf or 6 - 9mm MDF or similar on the outside lined with 12 - 18mm of concrete inside. I tried this latter method with OB and it worked well.

My general take is to simply use two dissimilar heavy materials bonded together to damp resonances - but however much we can reduce cabinet vibration it's very hard to eliminate it completely so next I try a different cab for each driver to stop inter driver interaction.
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Old 18th October 2010, 08:47 PM   #766
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Village plank - where did you get that solid beech? I'm in the UK too and interested! As far as I gather, strips glued together are more stable and less likely to crack.

Andy
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Old 18th October 2010, 08:56 PM   #767
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Originally Posted by andyjevans View Post
Village plank - where did you get that solid beech? I'm in the UK too and interested! As far as I gather, strips glued together are more stable and less likely to crack.

Andy
Here you go....

Beech Worktops

I dare you to have a go with Wenge lolol..... super expensive!

Indeed the 40mm x40mm staves are 93 times stronger than MDF and 66 times stronger than birch ply of the same thicknesses in tension testing. People need to listen to this as I will only say this ONCE...... you ready........ Drum roll...... PROPERLY KILN DRIED AND TREATED HARDWOOD WILL NOT MOVE, SPLIT, WARP, CHECK, SHRINK OR EXPAND...... END OF!!!!!

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Old 5th May 2011, 08:46 PM   #768
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This recently generated graph is relavent to this discussion.

It shows the relative energy available to excite a resonance relative to a likelihood of 1 at 300 Hz. 300 Hz was choosen because this is considered the typical point where half the energy in the music is above, and half the energy below, and is key to one of the suppositions that leads to a 1/forth power.

A/ 1/second power falls out of the way a cone driver works to mantain flat frequency response

I argue that we can achieve the 4th power by considering:

B/ the "quantity" of music falls with increase in frequency
C/ the effectiveness of the panel material's damping increase as the wavelength decreases vrs material thickness

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dave
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Old 8th May 2011, 08:37 AM   #769
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http://diy-audio.narod.ru/litr/1977-03.pdf
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Old 12th May 2011, 12:00 PM   #770
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Gentlemen, first I have to say - I'm an (automotive) engineer. I don't believe in rumours and hearsay, I prefer data over politics. Instead of belief I trust in data. In 2008 a German magazine - stereoplay - published in one of their issues a supplement about DIY loudspeakers. One of the six articles, written by Bernd Timmermanns (inventor of many DIY loudspeakers, like the Needle), was about best material for loudspeakers. You can read it here, when you use an online translator, ie. Google (hopefully the link works):

Boxenselbstbau - Gehäusematerial - stereoplay - Magnus.de

Take a look at the graphs and come up with your own opinion. My personal conclusion from this article is, in general: the heavier - the better, due to higher density.

Outcome is that at roughly the same thickness, slate scores the highest over concrete and MDF, which finished on third position. Famous baltic birch ends up on rank 7 from 8 contestants.

Baltic birch is the preferred material for all highly stressed applications and the No. 1 for PA speakers. By the way, I used baltic birch for my own DIY speakers ...

Helmut
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