These days Open Baffle / dipolar loudspeakers have become very popular and in DIY circles there are many examples of this construction principle. One prominent constructor is Siegfried Linkwitz and his Orion Open Baffle loudspeakers. An example of a mass-produced commercial dipolar loudspeaker is the award winning Jamo R909 and it's little brother R907.

Jeroen KV has constructed his loudspeakers with 2 pieces Aurasound NS12-513-4A woofers and a Bohlender & Graebener Neo8PDR planar. The drivers were chosen for their very low distortion and the possibility of only 2-way crossing or rather 2,5-way as one of the woofers only "helps" at the lower frequencies. Jeroen has chosen the obvious approach and made them active, which makes it much easier to get the right "drive". You simply have to EQ these kind of loudspeakers and it is easily done with our DCN23 - the result is convincing!

Above is the construction drawings at an early stage - some details have been changed on the way to the final speaker.

Jeroen got the wood cut out and CNC milled - ready for assembly and here is the result.
You can find more information in this thread:
Mijn finale OB speaker on the dutch DIY forum zelfbouwaudio.nl

As usual one can't wait to hear the result of all the labor and the loudspeakers has to be tested before the final finish painting ... years can go by before it happens! Not said that Jeroen will take that long

Jeroen has choosen to put the electronics into a Modu / Hi-Fi 2000 box - model GX388 (330 x 280 mm). The amplifier is a 3-way active with our DCN23, PSU DCN and relayboards + 3 pcs. Hypex UcD180 and supply

Measurments of the drivers imported in the XOverWizard:

Some comments and thread quotes - Jeroen:

The tricky part of the B & G Neo8PDR is that it has a peak at 12000Hz. If you want to correct it with an analogue notch filter, it can be a tough job. A Digital notch filter can be quite simple and much more accurate than an analogue one - only the peak will be addressed and the output at 20000Hz is well preserved. So you see how easy you can get the perfect curve with the DCN23.

Filtering and EQ is super. Download the free software and import the frequency curves. Simulation = reality with this tool. The question is rather - what you can't do? It is very easy to operate, so no hassle with all kinds of manuals etc.

Nice to see that real reality = simulation - Everything exactly true…

You can use the matching software for filtering and acoustic adjustments to model the loudspeaker setup (you can import measurements), then you upload the setup via USB. This takes 1.5 seconds and can also be done while you are listening to music (brief pause mute). This is ideal to determine what an adjustment does. This way of filtering and correction is not comparable to the traditional way... You have to try it before you know what the possibilities are.

When I measure my room response - I use a Behringer DSP8024 with room correction software. I can easily identify room modes this way. When I take out a 60 Hz peak / room mode the bass gets a lot tighter!

I replaced the capacitors and after extensive testing....... good news!! I hear no "hum" anymore! The speakers are now very quiet. (The problem of the smallest PCB transformer resolved)

The sound is just simply very neutral and the listening homogeneity is preserved.