Constructia de Incinte de la A la Z

[Vizitator Andrei.Hrubaru]

deja ma simt mai prost ca niciodata, dar mult mai destept ca inainte :finga: am facut o lista cu intrebari pe care as dori sa le adresez cuiva care lucreaza cu BlastBucsa, poate ma lumineaza asupra catorva aspecte noi pentru mine. documentatie este pentru toata lumea, dar sincer ma indoiesc ca amatorii chiar o sa o citeasca cap coada :axe: Let us pray ...

[radue]

daca vrei vb pe pm

[Vizitator Andrei.Hrubaru]

Am gasit ceva foarte util amatorilor de incinte home-made:

 

Avoiding Standing Waves

 

Most boxes are roughly shoebox or rectangular in shape. Technically speaking, this is a square prism. Unfortunately, these box shapes have a built-in flaw: box shapes with two or more sets of parallel sides will be prone to a phenomenon called ?standing? waves. Standing waves are sound waves that reflect back and forth between two parallel sides inside the box. The frequency of a standing wave will have a wavelength equal to twice the distance between the two sides. For example, if two parallel walls are 24 inches (61 cm) apart, the standing wave that will develop between them will have a wavelength of 48 inches (122 cm). This corresponds to approximately 283 Hz. You can use the wavelength calculator in BlastBucsa Pro to convert from the wavelength to the frequency.

 

A cube is generally a bad box shape since all of its parallel sides are equidistant. This means that all the standings waves inside the box will have the same frequency and will sum together, making them louder. This reduces the fidelity of the loudspeaker. But all is not lost if you really like the cube shape because there are ways to overcome standing wave problems. Here are a few suggestions:

 

 

? Add damping to the interior of the box. Bear in mind, that most of the commonly-used absorption materials have poor absorption coefficients at low frequencies. If your box is large, you should probably calculate the frequencies of the standing waves and check the absorption coefficients at those frequencies for the damping material you plan to use. Also, see the Damping tab of the Box Properties window.

? Add one or more angled walls to the interior of the box. In this way, the outside of the box still has parallel walls, but the inside does not. These walls must be rigid and either have openings or be short in one dimension so that air can flow around them without any restrictions. Without parallel walls, standing waves will not develop.

 

? The frequencies of the standing waves can be spread apart so they do not sum together. This is accomplished with the ?optimum square prism? box shape in BlastBucsa Pro. It uses a 1.62 : 1 : 0.62 ratio between its three dimensions (height, width, depth) to spread apart the frequencies of the standing waves.

 

? Pick a box shape without parallel sides such as a four-sided pyramid.

Diffraction

 

The diffraction caused by some box shapes can have a very significant effect on fidelity. For example, a cube can introduce a ?5 dB variation to the amplitude response of a loudspeaker (depending upon the area of the mounting surface). A shape that produces very smooth amplitude response is a sphere. Unfortunately a sphere is not a very practical shape to use for many designs. Here are a few suggestions to help minimize diffraction:

 

? Locate the drivers so they are not the same distance from any two or more edges.

? Mount all drivers flush in the front panel.

 

? Round the edges and corners of the box. They must be rounded rather severely to be effective.

sper sa ajute :yawinkle:

[vikingul38]

mai pe romaneste fratilor....cu engleza nu stam toti asa de bine....postati ceva grafice...si interpretatile...fratilor...ce-i ala gain...spl...grup delay((/????))nu pot sa postez ceva simulari facute cu winsid....\ :finga: :smt006

[Vizitator Andrei.Hrubaru]

cu WinISD nu cred ca e vreo problema, pentru ca e un soft free. daca totusi engleza ta nu e atat de precara, pe cat te plangi :

 

http://en.wikipedia.org/wiki/Gain

http://en.wikipedia.org/wiki/Sound_pressure_level

http://en.wikipedia.org/wiki/Group_delay

 

enjoy !

 

http://en.wikipedia.org/wiki/Audio_system_measurements

 

si aici :axe:

[Vizitator Andrei.Hrubaru]

am revenit cu o intrebare: cum as putea sa prelucrez PAL-ul melaminat fara ca marginile sa se ciobeasca (melamina) sau cu ce as putea masca muchiile ? vreau sa arate bine si nu stiu daca sa o fac cu PAL melaminat sau sa opez pentru PAL simplu si sa-l mochetez. voi ce ati face/facut ?

[Extrem]

cum as putea sa prelucrez PAL-ul melaminat fara ca marginile sa se ciobeasca

Eu nu stiu sa se ciobeasca nimic....asta depinde acuma la ce te referi cand zici ,,sa prelucrez''Personal mocheta de boxe arata bine pe floorstandere...altfel mi se par o mare porcarie este parerea mea...

[Vizitator Andrei.Hrubaru]

tocmai de aceea intreb, nici eu nu as opta pentru mocheta, mia ales ca as putea sa le fac pe din PAL pe aceasi combinatie ca biblioteca si biroul :supz:.la ce ma refer la prelucrat? pai la taiat la unghi drept si ascutit urmand o linie sau un arc de cerc :smt006 ce altceva :finga: ? si ma uit la birou si vad ca acolo unde marginile nu sunt melaminate (pe grosimea PAL-ului) sunt mici ciobituri in melamina care nu ar da bine, nu sunt foarte vizibile, dar intrebam poate pot sa le evit totusi , sunt eu un perfectionist :weedman:

[Extrem]

Nu se ciobeste nimic...tai si tu cu bun simt :finga:

[Vizitator Andrei.Hrubaru]

si cu marginile fetelor care nu sunt melaminate ce fac cu ele? raman asa ne-melaminate ? sa le vopsesc ? sau cum :axe: ?

[Extrem]

Le chituiesti...vezi ca este un topic pe undeva despre finisarea boxelor...citeste aia si vei sti ce ai de lucru :rock:

[Vizitator Andrei.Hrubaru]

le chituiesc cu chit de masina si-l smirgheluiesc si apoi il vopsesc, nu ?asa parca citisem undeva, nu stiu daca pe forum sau in alta parte :yawinkle:

[vikingul38]

ma ajuta un specialist sa-mi spuna ce dimensiuni (pe romaneste )

are acest tub bas reflex?????

Driver : ydd 165

Vas : 17,2

Qts : 0,50

Fs : 59,55

SPL : 89,79

--

Project by : florea

Project for : you

--

Number of drivers : 1

Box type : Vented

Box size : 35,6 l

Tuning frequency : 47,52 Hz

Vent : 1 vent(s)

0,225 m length for each = (lungimea tubului???)

0,102 m round( diametru pe interior????)

 

 

Relative

Freq Gain Phase SPL

[Hz] [dB] [deg] [dB]

20,00 -32,61 315,08 57,18

25,00 -24,03 300,97 65,76

30,00 -16,68 283,92 73,11

35,00 -10,24 261,94 79,55

40,00 -5,02 233,02 84,77

45,00 -1,79 199,80 88,00

50,00 -0,51 170,66 89,28

55,00 -0,18 149,08 89,61

60,00 -0,10 133,24 89,69

65,00 -0,08 121,06 89,71

70,00 -0,06 111,22 89,73

75,00 -0,04 103,01 89,75

80,00 -0,01 96,00 89,78

85,00 0,02 89,90 89,81

90,00 0,04 84,53 89,83

95,00 0,06 79,77 89,85

100,00 0,07 75,52 89,86

 

cum sunt simularile....???

pacat ca am cutia doarde circa 23 litrii( trebuie 35 l)

[Vizitator Andrei.Hrubaru]

vikingule vad ca ai inteles foarte bine despe ce incinta este vorba. daca ai cutia de 23-25 l , atunci cauta un difuzor care sa mearga bine la volumul asta (sau un volum mai mic), nu stiu ce altceva ai putea face.