Full range speaker Visaton FR10-4, with DSP and Class D amp (or passive)

This is a full range loudspeaker using the well known Visaton FR10 chassis. The speaker is active, with high output Class D amplifier and DSP (digital sound processor). 

Frequency range -3dB 60Hz  - 20000kHz, 1W SPL 86 dB, 30W RMS, 6 litre bass reflex cabinet with magnetically held detachable grills (optional).

The whole project was realised with less than USD $100 expense for the lot for either active or passive version, not much difference as the coils and capacitors for the passive version are not cheap.

Application is bookshelf speakers, with enhancement by a subwoofer if needed (see my other designs, it works well with the large subwoofer which has sufficient sound pressure level to keep up). However, even without subwoofer the sound pressure level and output power is high enough to run a house party - but it won't rattle the windows. 

Alternatively, if you want a passive setup and use an external amplifier, there is a version with baffle step correction filter and Zobel network for impedance correction. Without it, the speaker sounds very shouty with the mids too elevated, I do not recommend running it without any correction. See the 3 curves in the frequency plot for no correction (blue), correction network (yellow), and DSP (pink). 

The DSP amplifier is the Wondom BDM3P,  a 2x50W Class-D stereo amplifier board built around the Texas Instruments TPA3116 chip and a Mountain View DSP chip. It has Bluetooth 5.3 input and AUX in/out. An external power supply 24V 4A is needed, but most old 19V laptop power supplies will work.

Some points re BDM3P idiosyncrasies:

• Get the BDM3P with the cable kit, although you won't need the LEDs and use only one of the potentiometers for volume.

• The 2 supplied LEDs in the cable kit are way too bright, and there are already the same LEDs on the PCB which you easily can see through the ventilation openings of the panel. 

• The treble and bass potentiometer stop working as soon as the DSP has been modified, I found this out the hard way and had to re-design everything. Only the volume potentiometer works. 

• As soon as you plug in a AUX in cable, Bluetooth de-connects and switches off, the blue LED starts blinking. Super annoying if you use the bright LED in the cable kit. 

• What comes out of the AUX out port is influenced by the DSP settings, so if you cut off the bass < 60 Hz for example to protect the speakers, a connected active subwoofer will be badly affected and needs compensation by increasing the volume and crossover. 

• The heat sink on the PCB gets warm during standby, measured around 45 degrees after 20 minutes on the infrared thermometer (not enough to melt PLA...). Interestingly it does not get much warmer when playing loud. Might be a good idea to use ASA or ABS for the panel and caddy.

Tools:

• Core XY 3D Printer with minimum 240x240x240 build area

• A bedslinger 3D printer might work, I have no experience. Maybe the mass of the enclosure of around 1.3kg is too high and it will come off the build plate. 

• Soldering iron for electronics, and heat inserts.

  Printing:

(Sorry, I don't have a multicolour printer or AMS, just a Qidi Q1 Pro where I have to change spools manually)

• Prepare the magnets: mark one pole of each magnet of the stack with a permanent marker, this marking has to show up when inserting them into the enclosure and the grille, when printed as below. 

• Enclosure: PLA matte, 0.6mm nozzle, 3 walls, 25% gyroid infill, print on face, adaptive layer height at the bottom to reduce layer lines around the bass reflex port flare. No support - it's designed in and can be removed easily. Enter pause command in slicer at around layer 13 (check in your slicer, depends on your layer height) before the holes are covered to insert the magnets on a drop of super glue with marked side up. 

• Back cover: PLA matte, 0.6mm nozzle, print on back. No support. Support for the BDM3P back plate, is designed in (see photo). 

• Caddy for BDM3P: PLA possible, I used ASA re heat concerns. 0.6mm nozzle. 

• Panel BDM3P: PLA possible, I used ASA re heat concerns. 0.4mm nozzle (or 0.2mm) to make the labels better readable. Enter pause command in slicer when the labels are appearing, and change spool to a contrasting colour (white in my example) for the writing. 

• Grille, fixing ring: PLA, 0.6mm nozzle, print grille on front face, enter pause command in slicer just before the magnet hols are closing and insert magnets on a drop of super glue with marked side up. 

• Gasket, feet: TPU 85A or 95A, 0.6mm nozzle

Assembly with BDM3P: 

• Prepare the USB cable from the cable kit, cut off the USB-A connector, and solder the 3 wires to the USB-C panel connector. The cables are designated V, D- and D+, on the BDM3P board and the USB-C panel. 

• Solder one of the rocker switch cables to the power supply jack, and the cut off cable to the other tab of the power supply jack. The 2 cables will later be soldered on to the BDM3P left and right of the PCB power supply jack - this PCB jack will not be used (see photo). You need a multimeter to make sure the polarity is correct, by checking that there inner connector pin of the power supply jacks on the panel and the PCB are connected. 

• Solder the volume potentiometer cables and the speaker wire for the left speaker from the underside of the PCB (see photo), the right speaker cable will be soldered in last once everything is about to be closed.

• connect the AUX out cable from the kit, and roll up the long cable and zip-tie it together

• The AUX in connector is on the PCB and lines up with the panel, nothing to do here.

• Screw the PCB on the caddy with M3 bolts

• Solder the loudspeaker cable to the PCB from underneath. 

• Insert the speaker terminals for the left speaker and solder them up to the PCB. 

• Pull 50cm of 16G speaker cable through the hole in the amp case so that 15 cm sticks out, and seal it with a little bit of glue around the hole

• Glue the back plate into the enclosure and let it cure, with some weights applied until solid

• Put the 16G speaker cable in the PCB from the underside, and solder from above

• Screw the complete panel assembly into the back plate.

• Line the internal walls with damping material, but do not obstruct the bass reflex port.

Assembly of the left speaker:

• Glue the back plate into the enclosure and let it cure, with some weights applied. 

• Insert the speaker terminals and connect to the speaker 

• Line the internal walls with damping material, but do not obstruct the bass reflex port.

Assembly of the passive version with correction circuit:

• Needless to say, you will need 2 correction networks, one for each speaker.

• The components of the circuit have to be soldered on the PCB board, according to the schematics (see PNG graphic in the photo section) . Stick the component wire through the holes in the PCB, align the wires and apply plenty solder. 

• Solder the wires from the terminal and to the speaker to the PCB, attach the spade connectors to the cables (crimp or solder)

• Screw the PCB to the sockets of the back plate with 3mm bolts

• Glue the back plate into the enclosure and let it cure, with some weights applied.  

• Line the internal walls with damping material, but do not obstruct the bass reflex port.

Speaker grills:

Lie the speaker grille onto the cloth, wrap the cloth loosely around the edges. Press the fixing ring slightly over the cloth into the slot, and pull the cloth straight. Once all even and under a bit of tension, press the fixing ring all the way in until flush. Apply super glue over the ring, it will soak a bit into the fabric. Let it cure and cut off the excess cloth with a sharp blade or hobby knife.

DSP Software ACP Workbench:

The ACP Workbench runs on Windows only. The download is available on the product website on Aliexpress, or here. The program is tailored to the BDM3P and you cannot use any other version of the software you might find elsewhere. It is pretty badly implemented in parts, and there are a lot of useless functions for Karaoke machines, microphone input, guitar effects and so forth, none of this you need. Some chinese dialogues are not translated. 

The only thing needed is the 10 channel equaliser, to be found under the register card Audio Effect - Effect List 1 - Music Pre Eq, or Music Out Eq, if you want ot add another 10 Eq channels. I have added a settings file in the attachments which I configured, the result you can see in the plots graphic. You can upload this settings file (AudioSettingsData.ini) under File - Import Audio Settings and save it, and then go to Downloader - Save configurations file to flash to the DSP chip permanently. 

Of course these settings have been configured in my room with specific size, reverberations and room resonances, so you might need to edit the EQ settings in your environment, maybe use a spectrum analyser software on an iPhone or Android. Or you just adjust it by ear, if you don't have a measuring microphone and software (UMIK-1 and REW suggested). The whole thing is real time, so a soon as you change something you can hear it immediately.  

Feel free to play around, even with the effects like bass enhancement. However, if you start from scratch, I suggest the first thing in the EQ settings is to use a high pass filter with Fc 60Hz 12dB Q1 to protect the speakers from low frequencies which might destroy them due to exceeding Xmax below the bass reflex tuning frequency when played very loud. The next setting is a peaking filter Fc 3000Hz 5dB Q0.7, to get rid of the nasty baffle step amplification between1-3kHz. After this it's all to your personal taste...

Bill of materials DSP version (exemplary links to suppliers included, non affiliate):

4kg PLA filament (or PLA-CF, PETG-CF) colour of choice and low price (I use 5kg spools with overhead feed, works out circa $8 per kg PLA)

2x Visaton FR10-4 

24x Neodymium magnets 10x2mm

1x Wondom BDM3P with cable set

1x rocker switch 

1x DC power supply jack  5.5mm

1x USB-C socket 6 pin

8x M4 10mm hex bolts

36x M3 x 8mm hex bolts

2x M2 x 6mm hex bolts and nuts

1x speaker grill cloth

1m speaker cable 16G

4x loudspeaker terminal

4x spade connectors 2.8mm and 4.8mm

8x heat insert M4 8.1mm

28x heat insert M3 5.7mm

1x 24V 4A power brick

Epoxy glue or building adhesive for the speaker back (don't use superglue, it's too viscous and leaves leaks)

Superglue for the grill fabric fixture

1" damping wool for the internal walls (I use dense polyfill batts) 

Bill of materials for the passive correction network, no DSP:

As above, minus the BDM3P and connectors:

2x 7x9cm PCB board

2x  5.6 Ohm 10W Resistor (5W version would be ok)

2x  3.9 Ohm 10W Resistor (5W version would be ok)

4x 15uF capacitor

2x 0.4mH inductor

4x loudspeaker terminal

4x spade connectors 2.8mm and 4.8mm