The role of sound-absorbing material in the sound box

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 What are the effects of sound-absorbing material in the sound box, the sound absorbing material is
suitable for speaker manufacturers using large quantities, the amount placed right, closed box
placed sound-absorbing material is easy to understand, inverted box has two division and three
division and four division division, is also a form of subwoofer inverted box, take these different
how to place the box, sound-absorbing cotton, placed much like Alto cavity placed, placed much, is
a relatively vague, the lack of a clear definition of public information difficult to find. So we
need to participate in this discussion, the author first published some personal views.
The speaker used sound-absorbing material sound absorption coefficient table
Name of material thickness of CM density kg/ frequency Hz square meters
4000 12525050010002000
Superfine glass wool 0.1 0.3 0.65 0.65 0.65
Superfine glass wool 0.18 0.38 0.89 0.81 0.98
Superfine glass wool 0.35 0.85 0.85 0.86 0.86
Polyurethane foam plastics 0.12 0.7 0.21 0.48 0.77 0.76
Polyurethane foam plastics 0.28 0.78 0.69 0.81 0.84
5200.14 0.37 0.68 0.75 0.78 acrylic cotton 0.82
A from the absorption coefficient table, in the same thickness under the condition of several
materials are similar, in the above 500Hz, the absorption coefficient of glass fiber is slightly
larger, but failed to find the 1 2CM thickness data, because of the sound-absorbing material inside
the sound box by the price factors, the general could not spread too thick. Since the sound
absorption performance of several materials almost, is the price of the preferred, acrylic cotton
is a good choice, choose to choose acrylic cotton, fiber thin, high density, do not spray a lot of
adhesive (for acrylic cotton and shaping glue). In fact, there is a vast source of sound-absorbing
materials, waste is multilayer corrugated boxes, corrugated carton board multilayer nail at the
inner wall of the box, is a very good sound absorption, high quality and inexpensive. Particularly
suitable for amateur use.
For various types of speakers, regardless of how we deal with the back structure, acoustic
radiation way follow a principle, not only silencing or semi mute processing. The closed box, for
silencing processing, sound-absorbing material to loose fill most of the space (near the speaker
frame window space).
The other speaker, should be half of the low frequency silencing processing,
namely the resonant frequency, to guide the use, to maximize the resonant wave energy radiated by
the inverted tube, so the sound-absorbing material around the wall of the box should be placed,
don't block the internal resonance wave channel, not to block phase reversal nozzle. Let the
speaker to pour tube smoothly. Don't be sound-absorbing material into the group freely placed
inside the box to sound-absorbing material
The material is fixed on the wall of the box. With the speaker mesh covered phase inverted tube
mouth some manufacturers think it sounds good, actually this is wrong, this shows that the speakers
sound long, sound-absorbing cotton should be increased. Over the inverted tube, will make the low
efficiency.
The bass is sound-absorbing cotton, has three functions, one can increase the
equivalent volume of large volume box, this box of small volume of no great importance, but it is
very good. The two is to adjust the transient characteristics of the sound-absorbing material more,
can improve the transient performance, and make the bass has certain elasticity, the sense of
hearing is more comfortable, everything has a degree, sound-absorbing material too much will reduce
the low frequency output sound pressure. The current status of the market, not the sound-absorbing
material too much, but generally too small, many manufacturers are symbolic release point, and put
the varieties also wrong. For example, some put a small piece of large pore coarse reinforced
sponge, aperture thick sponge, sound-absorbing effect is very poor, if the choice of sponge, must
choose high density sponge pores. The three is the resonant frequency above all inside the band, as
sound processing, the more thorough the better silencing, silencing more thoroughly, more small
back radiation interference.
A cavity of sound-absorbing cotton, role is only one, namely, silencing, sound-absorbing material
more, the silencing effect is better, the smaller the back radiation interference. The higher the
fidelity of the positive acoustic wave reduction. The actual status of the manufacturers is hardly
Alto cavity placed sound-absorbing material, analysis of the reasons, nothing more than two
factors, one is the cost savings, two is not to understand the sound-absorbing material in the Alto
cavity.
The Alto chamber, the ideal state should be based on the closed box, the sound-absorbing material
covered with loose cavity, the influence of price factors, most manufacturers do not, but for the
high-end box, or for some good. Is the general tenor speakers, volume little, is filled with sound
-absorbing material, the cost is limited, small volume can not hear it, large volume can still hear
the difference.
The subwoofer, bass effect and sound-absorbing material before the two the same, one is to increase
the equivalent volume, the two is to improve the transient performance. There is no interference of
the back radiation acoustic wave.




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Tags: sound-absorbing material