The main idea of this project is that of a central home theater loudspeaker capable of reproducing at best the whole audio band with a classic horizontal development but without using the double midwoofer configuration in order to avoid the well-known problems of non-coherent lobes at the intersection and of destructive interference on the medium frequencies and therefore on the band of frequencies where the center channel has to give its best.
This is a 3-way bass reflex loudspeaker, not too big and therefore easily to insert into the room, with a sound that i would define as balanced and therefore without particular emphasis, with an adequate deep frequency reproduction for its use.
For the realization i chose drivers with an excellent quality / price ratio:
Tweeter: Sb Acoustics SB26STCN-C000-4
Midwoofer: Faital Pro 5FE120
Woofer: Faital Pro 6FE100
Starting from these drivers i realized a box with dimensions 24x50x31,9cm (HxLxP) made with a 19mm mdf structure and internally structured in 2 separate volumes, a 2.3-liter closed for the midwoofer and another of 21 liters approximately for the woofer with the reflex duct of rectangular section obtained directly from the cabinet and placed laterally for a possible recessed positioning in a TV cabinet (the duct can also be made with round tube the important thing is to respect the internal diameter of 8 / 8.2 cm about for a length of 28/29 cm but it would leave only 1 cm of space from the back wall, a situation that could create some problems of turbulence).
As far as the tune frequency for the woofer, it is about 46Hz, lower than the classic tune in order to obtain a less steep frequency drop more similar to a closed box load and also to limit the excursion of the woofer at lower frequencies where it will emit only the reflex as shown below where in purple we see the used tune and in red the classic one:
This is the final shape of the box:
CONSTRUCTION PLANS
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all panels are in mdf 19mm except the internal ones which are in 15mm mdf.
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insert the glass wool into the volume of the midwoofer.
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in the volume of the woofer insert on the walls “A, B, C” soundproofing material polyester fiber type thickness 30mm, with the foresight, on the wall B, not to obstruct the air passage in the reflex port, i would recommend cover the wall B for a length of not more than 35cm.
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place the crossover filter on the base behind the woofer about 10/15 from the magnet of the same and place the connection terminals on the back wall where you prefer.
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drill a hole on the small left wall of the midwoofer volume or on the wall D for the passage of the connecting cables coming from the crossover filter of the tweeter and the midwoofer having the certainty of sealing it well around the cables with silicone sealant not to allow the passage of air from one volume to another.
Response 2,83V/1mt each drivers
Response of the single drivers without filters, the woofer’s response (green) is the result of the merge between the farfield measurement and the nearfield measurement (also including the near reflex port), in purple the midwoofer response and in red the tweeter one .
Response 2,83V/1mt reflex, woofer and sum
Nearfield response of the woofer (cyan) , reflex port (violet) and sum (red).
Response 2,83V/1mt
Impedance curve
Crossover filter – schema and components
Crossover filter – electrical response to the speaker terminals
Speaker Decay 2,83V (60cm gated)
Woofer and reflex port decay 2,83V (nearfield 2mm)
THD loudspeaker (35cm)
Technical features
- Type: Home theatre horinzontal center channel loudspeaker
- Numero vie: 3 way
- Load type:
- Midwoofer losed box
- Woofer bass reflex
- Tweeter 2.54cm(1″) soft silk dome
- Midwoofer 13cm (5”) cone rubber suspension
- Woofer 16cm (6”) cone rubber suspension
- Crossing frequencies 330 Hz / 3500 Hz
- Sensibility 90,5db @ 2,83V/1mt
- Nominal impedance 8 ohm
- Pin. power 15 watts RMS per canale.
- Frequency response 55Hz – 18 Khz (-/+ 3db)
- Recommended listening distance >= 2mt
- External dimension 24x50x31,9 (AxLxP)
- Box 19mm mdf panels, internal treatment with sound-absorbing.
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