B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT

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OSIB16

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B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« on: 12 Jul 2019, 09:24 pm »
I just completed modifying a set of Bang & Olufsen Beolab 4000 active speakers, and wanted to document the progress on this forum. They are the more desirable Mark 1 versions (Class A/B built in power amps). Most people prefer them to the later Mark 2 which uses built in Class D power amps.
« Last Edit: 12 Jul 2019, 10:59 pm by OSIB16 »

OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #1 on: 12 Jul 2019, 09:32 pm »
They are an odd shaped cabinet with solid aluminum build. Very beautiful to look at. Without the modifications the overall sound quality is quite good in my opinion (lots of potential), with balanced treble through to bass. The treble is smooth and clean,  and the bass is extended and powerful. Transparency is pretty good. However the downsides is that it is possible to hear a slight cabinet coloration. They go quite loud without distress, but bass becomes distorted when pushed to high levels.
« Last Edit: 13 Jul 2019, 02:38 am by OSIB16 »

OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #2 on: 12 Jul 2019, 09:51 pm »
The unmodified circuit boards are shown in the photos...





OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #3 on: 12 Jul 2019, 09:53 pm »



OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #4 on: 12 Jul 2019, 10:00 pm »
To cure the cabinet coloration I lined all the inside panels with grey adhesive backed 4mm thick wool fabric (shown in photo)...



 
« Last Edit: 13 Jul 2019, 02:31 am by OSIB16 »

OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #5 on: 12 Jul 2019, 10:06 pm »
Ok now I’m going to show the circuit board modifications done. I swapped out all the junk wire for Neotech and Jupiter 6 nines copper, and Kimber.

OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #6 on: 12 Jul 2019, 10:14 pm »
I Installed the following wires myself...

NEOTECH 12AWG PVC STRANDED COPPER (Power Input + Transformer Input).

KIMBER 19AWG VARISTRAND COPPER (Power Jumpers).

NEOTECH 16AWG SOLID CORE COPPER (Bass Midrange drivers).

JUPITER 23AWG SOLID CORE 6N COPPER (Tweeters).


(((((SPEAKER WIRING IS BARE COPPER, TREATED WITH DEOXIT GOLD & THEN COVERED IN PURE COTTON SLEEVE)))))








OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #7 on: 12 Jul 2019, 10:48 pm »
I fitted the 2 large Mundorf AG capacitors onto the board myself. They are slightly taller than the old Samwha’s  and had to be slightly offset to fit into the cramped speaker cabinet. I extended the legs with OCC Copper 18AWG magnet wire...


OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #8 on: 12 Jul 2019, 10:51 pm »
My local hifi repair guy installed all the Elna Silmic II electrolytic capacitors and ensured that the speakers were up and running...


OSIB16

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Re: B&O BEOLAB 4000 ACTIVE SPEAKER PROJECT
« Reply #9 on: 27 Jul 2021, 10:06 pm »
I’m a bit late here (by a few years  :lol:). I would like to provide my review for the modded Beolab 4000’s…



UPSIDES:

Massive improvements in terms of holographic 3D soundstage with instruments floating pinpoint/solid in the air in front of you. Voices are bang in the middle, you would swear that there is a centre speaker in the room (not joking! I had to keep checking). With well recorded music, and connected to a Beosound Core; the bass has more weight. There is more definition in treble, midrange and bass. There is also more ability to turn the volume up higher, without the sound falling apart (my DIY 4AWG copper power cables definitely help here). The built in analogue power amps (after modifications) are seriously high end sounding.



DOWNSIDES

Sound hollow and pinched when played from cold. Need at least one hour of music playback before these shortcomings disappear. The weird shaped cabinet is responsible for causing a degree of midrange coloration which manifests itself as ‘boxiness’. This is only evident with ‘talking voices’ like for example a radio channel commentator. Other than that; it is not noticeable during music playback.





FINAL THOUGHT… I would recommend using 18 AWG solid core copper wire for the bass midrange driver instead of 16 AWG. The result being that midrange sounds slightly more natural, while at the same time bass response is better balanced and integrated.
« Last Edit: 26 Sep 2021, 07:36 pm by OSIB16 »