Duelundister bruger overvejende grov træuld i baskasser og et twist-lignende materiale i mellemtonekabinetterne til dæmpning.

Isolering overlades trygt til bygningshåndværkere..

Mvh. Jens/Modifix, - der ikke rigtig kan finde på noget at skrive her..

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Oksen er træg men jorden er tålmodig..

Så har jeg fundet lidt omkring kabinetter. Det er stadig ikke helt på det niveau jeg leder efter, men det er da en start.

(kilde: http://users.cwnet.com/kant/speakfaq.htm#best)

What is the best material to make speaker boxes out of? Why?
An ideal speaker cabinet material would be very stiff, so that it would not tend to move with variations in box air pressure. It would also be very well damped, so that if it ever does deflect from air pressure, it will come back to the original position without resonating. It would also have a very high resonant frequency (supersonic), so that low frequency box air pressure would not cause it to resonate. An attractive material is preferred, and additional credit is given for a material which is easy to cut, glue, and finish. A great material would be cheap, too. Finally, it would be nice if the material were light, because we all have to move our speakers sometimes, and it's hard to appreciate good speakers with a sore back.

With all of those attributes, it would seem that no material is perfect. However, there are many materials that have enough of the above good attributes to make excellent speaker cabinets. Yet each has advantages and disadvantages.

In the list of good speaker box materials below, letters are used to indicate which attributes the material possesses.


          S = Stiff
          D = Damped
          H = High Resonance
          A = Attractive
          M = Machinable
          C = Cheap
          L = Light

MEDIUM DENSITY FIBERBOARD (MDF): SDMC This is the most practical material for quality speakers. It is harder to find than plywood, but most lumber yards can special order it. It cuts very nicely and has a smooth surface. It takes veneer very well. However, bring a helper when you pick the stuff up. One sheet is very heavy. MDF is harder on tools than common wood, but easier than particle board. This is the material that many great speaker makers use. US $45 for a 4'x8'x1" sheet. Density: 50 lbs/cu ft.

POLYCARBONATE (LEXAN): DML A clear or solid-color polycarbonate box can look strikingly good. However, this is not a cheap material. To locate it, look in the classified directory under PLASTICS. US $60 for a 1'x1'x1" sheet. Density: 75 lbs/cu ft. Acrylic (Plexiglass) is cheaper than Polycarbonate, but weaker and poorer damped (not recommended).

CORIAN, FOUNTAINHEAD, AVONITE, SURELL, GIBRALTAR: SDA Regardless of the brand, these synthetic countertop materials come in a wide array of colors and look beautiful. They are hard to buy, and harder to work. They take special glue to bond and require wet sanding with very fine paper to finish. You can tap it, but it's too brittle for wood screws. Corian is acrylic mixed with powdered aluminum triwwwte clay filler. Avonite, Gibraltar, and Surell are polyester resin mixed with the same clay filler. US $26 per 1'x1'x0.5". Density: 100 lbs/cu ft.

MARBLE: SDHA One challenge with marble speaker enclosures is cutting holes for the drivers. A carbide bit on a router will work, but it will dull quickly. Marble is also difficult to glue, so bracing is difficult. But it sure is pretty when you're done! US $25 to $45 per 1'x1'x1.25". Density: 160 lbs/cu ft.

PLYWOOD SHEETS SPACED AND FILLED WITH SAND OR LEAD SHOT: SDAMC If you have time on your hands and want a great impractical box, try this. Make a simple box out of common plywood. Then glue cleats on the outside of the box to space the outside plywood from the common plywood. Glue hardwood-veneered plywood to the cleats and pour sand or lead shot into the spaces between the cleats. It won't be light, but with the filler, it will be extremely well damped. In addition, if you use strong cleats and glue well, the box will be extremely stiff. One person used different size Sonotubes as an alternative to plywood, and filled the space between them with sand. Be sure to sterilize the sand in your oven before putting it in the box.

ALUMINUM SHEETS SPACED AND FILLED WITH ALUMINUM HONEYCOMB (Aerolam): SDHL Airplanes use this material for flooring. Next time a plane crashes in your neighborhood, see if you can get the wreckage for your next speaker project. You can't get a better, light-weight material. Celestion has exploited this for some great products. If you're really ambitious, you can make your own sandwich out of high-quality plywood faces and a thick honeycomb core. You will probably need an epoxy to glue the honeycomb to the plywood. A home-brew sandwich is easier to cut and glue than Aerolam.

FORMED CONCRETE: SDHC There are tricks to working concrete, such as to cast braces, rebar, and steel-wire right into the mix. Also, some concrete is better damped than other. Remember to oil your concrete forms so that they can be removed. Most concrete speakers use an MDF front panel, but you can pour one if you use cardboard tubes or plywood rings to mold the concrete into the shape of a speaker cutout. Alternately, you can make a common veneered plywood speaker box and cast concrete inside it for stiffening.

Any box can be improved by making the walls thicker, by bracing the walls, and by stiffening the walls. The stiffness of a material goes up as the cube of the thickness, so a slightly thicker material is much stiffer. A thicker panel will also have a higher resonant frequency because the stiffness goes up faster than the mass.

Consider lining the inside of your speaker with ceramic tile, attached with thinset mortar. You can get tile remnants cheaply. They are easy to apply and can be added as an afterthought to an imperfect box. However, be sure to attach all braces before tiling, because it is hard to attach anything to tile.

Also consider bracing any weak parts of the box. For example, all joints will benefit from a wooden cleat. The back of the box will benefit from stiffeners where the speaker terminals are attached. Most importantly, brace the front panel, or make it out of a double thickness of material.


Og så skal jeg lige have fat i denne her:

Nashif, A. D., Jones, D. I. G., and Henderson, J. P., "Vibration Damping", Wiley, New York, 1985.

[QUOTE=Kjeldsen]B&W anvender iøvrigt også krydsfiner i Nautilus-serien og den husker jeg da at Mike synes godt om .

B&W anvender sig af dette til bas kabinetterne og så er kabinetterne for det første afrundede og meget tykke i materialet, og der er anvendt en interne MDF matrix, en sådan matrix gør at det næsten er ligemeget hvad kabinet siderne er lavet af, og når der anvendes så kraftig X-finer materiale som her samtidig så er det ok.

Du vil bemærke at de IKKE! anvender denne krydsfiner til mellemtonen, der sidder i en kunststof "kugle" / "dråbe".

Jeg bemærked dog også tidligere at X-finer godt kan anvendes hvis der anvendes eks. bitumen dæmpning samtidig med en matrix afstivning!

Jeg har selv gode erfaringer med 12 mm X-finer limet sammen med 12mm MDF med viskoseelastisk lim til en ( inc. lim. ) 25 mm. tyk plade. MDF. inderst & x-finer yderse og så en god matrix afstivning, og masser af bitumen i mellemtone sektionen, samt sand i bunden hvor bassen sidder.

Alt limet med silikone og speciel viskoseelastisk lim.

På denne måde opnås et meget stabilt og viberations dødt kabinet der sikre at så meget som overhoved muligt af energien fra enhederne bliver overført til luften og ikke afsat i kabinetterne og ned i gulvet mm.

mvh.

Mike.

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M.

Hej Kjeldsen,

Godt initeritiv med den artikel, jeg er i det store hele enig.

Hvis jeg skulle designe en ht til mig selv, ville jeg lave svøbet i MDF, og afstivninger i spånplade. Afstivningerne skulle være "flettet" sammen lidt ala B+W. Dog ikke i en egentlig matrix. (Jeg bryder mig ikke om matrixen, luftflowet bliver ødelagt pga. den tætte matrix.) 

Blot mine tanker

Jeg vil når jeg har læst noget seriøst literatur, prøve om jeg kan formulere et undersøgelsesdesign, hvor forskellige kritererier skal opfyldes.

Jeg vil ikke udelukke tunge bitumen fyldte kabinetter, bare fordi jeg har en fornemmelse at de ikke er gode for lyden.

Jeg vil indenfor et par måneder købe et seriøst lydkort med 12 input (jeg er lydmand i min fritid), hertil kan jeg så tilslutte piezoelektroniske mikrofoner som kan monteres på kabinetoverflader. På denne måde håber jeg at kunne måler forskellige kabinettypers påvirkning af lyden.

miju:

Det viskoseelastisk lim du snakker om, hvad er det for noget? hvor kan det købes og hvad koster det?

Cerberus skrev: Hej Kjeldsen, Godt initeritiv med den artikel, jeg er i det store hele enig. Hvis jeg skulle designe en ht til mig selv, ville jeg lave svøbet i MDF, og afstivninger i spånplade. Afstivningerne skulle være "flettet" sammen lidt ala B+W. Dog ikke i en egentlig matrix. (Jeg bryder mig ikke om matrixen, luftflowet bliver ødelagt pga. den tætte matrix.)  Blot mine tanker

Hele formålet med matrix-konstruktionen er at udnytte kamrenes egenskaber som gennemstrømningsventiler hvilket muliggør en nær "perfekt dæmpning" af det lukkede kabinet

Et korrekt udført matrixkabinet kan slet ikke reflexafstemmes, kan det det, er det fejlkonstrueret.

B&W har iøvrigt ikke lavet ægte matrixkabinetter siden de oprindelige konstruktioner fra for over 20 år siden.

Waal