The challenge was to build a 3-way floorstanding loudspeaker, not too big and with an excellent WAF, well sounding, with an adequate frequency drop, for a 360 ° music / home theater listening, a discrete sensitivity and easy driving for a use also with minimal amplifications and above all at a price accessible to all …. have I succeeded? The answer to you after a short reading!

For the realization i chose drivers from me already tested several times with an excellent quality / price ratio:

Tweeter: Sb Acoustics SB26STC-C000-4

Midwoofer: Faital Pro 5FE120

Woofer: Faital Pro 6FE100

Starting from these drivers I made a floorstanding loudspeaker externally measuring 100x22x28cm (HxLxP) made with a 19mm mdf , with internal reinforcements and internally structured in 2 separate volumes, one with a 2.7-liter capacity closed box for the midwoofer and another about 37 liters for the woofer with the rectangular section reflex port made directly from the cabinet and placed at the front for an easy insertion of the speaker in the environment and placed at the bottom of the floor just above the woofer in order to use both the reinforcement provided from the floor for the low frequencies.

As far as the tune frequency for the woofer, it is about 34Hz, lower than the classic in order to obtain a less steep frequency drop and more similar to a pneumatic suspension load and also to limit the excursion of the woofer at lower frequencies where it will emit only the port as illustrated below where in celestial the porting used and in violet the classic one:

This is the final shape of the box:

CONSTRUCTION PLANS

all the panels are in mdf 19mm except the internal ones which are in 15mm mdf.
in the closed volume A of the midwoofer insert, filling it, glass wool.
fill the subvolume B 40 sound absorbent with 40mm polyester fiber
in the subvolume C insert on all the side walls, rear and front sound-absorbing ashlar-type.
place in the subvolume D ashlar type absorbing only on the inner septum of the reflex port and on the rear wall behind the woofer, arriving halfway through the driver to avoid obstructing the air in the port.
place the crossover filter on a side wall of subvolume D where the connection terminals will be inserted immediately below the soundproofing in the rear wall.
it is recommended to lock the cables inside the reinforcement partitions of the piece of furniture with clamps. .
drilling a hole on the back wall of the volume A for the passage of the connecting cables coming from the crossover filter of the tweeter and the midwoofer, being sure to seal it well around the cables with silicone sealant to prevent the passage of air from the volume A to the subvolume B.
place all the drivers with the flanges flush with the front wall (baffle), as an option you can avoid doing it only for the woofer.

Response 2,83V/1mt each drivers

Response of the individual drivers without filters, the response of the woofer (light blue) and the midwoofer (red) is the result of the merge between the farfield measurement and the nearfield measurement (for the woofer is also included near the reflex port which is very close the woofer also inserts a hole around 520Hz that does not worry us because the woofer will be cut lower.

Response 2,83V/1mt

Impedance curve

Crossover filter – schema and components

Crossover filter – electrical response to the speaker terminals

Midwoofer decay 2,83V (nearfield 2mm)

Woofer and reflex decay 2,83V (nearfield 2mm)

Loudspeaker THD (35cm)

Response in the environment from the listening point (2,5mt)

Technical features

Type: floor-standing slim tower speaker
Way: 3 way
Load type
- Midwoofer closed 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 380 Hz / 2800 Hz
Sensibility 91,5db @ 2,83V/1mt
Nominal impedance 8 ohm
Minimum power 15 watts RMS per canale.
Frequency response 50Hz – 18 Khz (-/+ 3db)
Recommended listening distance >= 2mt
External dimension 100x22x28 (AxLxP)
Box 19mm mdf panels, internal treatment with sound-absorbing.

PHOTO GALLERY HERE

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

all panels are in mdf 19mm except the internal ones which are in 15mm mdf.
insert the glass wool into the volume of the midwoofer.
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.
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.
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