BANG & OLUFSEN BEOVOX CX-50 SPEAKER PROJECT

OSIB16 · « **on:** 18 Dec 2018, 06:08 pm »

Hi everyone, I just thought I would document my progress by posting images and info on here regarding my latest Bang & Olufsen classic speaker project. I’m in the middle of modifying multiple pairs of Beovox CX-50 for use in a high end Dolby Atmos 7.1 cinema system. The first picture below is of them before mods are done. Jeff helped advise with the circuit construction...

B E F O R E

A F T E R

OSIB16 · « **Reply #1 on:** 18 Dec 2018, 06:18 pm »

The CX-50 uses a bombproof (heavily braced) aluminium cabinet with a thin plastic rear cover.

OSIB16 · « **Reply #2 on:** 18 Dec 2018, 06:24 pm »

SONICAP PLATINUM GEN 1 FILM CAPACITORS (6.8uf)...

OSIB16 · « **Reply #3 on:** 18 Dec 2018, 06:31 pm »

Pure Cotton washing line cut into multiple lengths for use as sleeving. Neotech 16awg solid core copper wire for the bass mid drive unit (going to strip off the pvc sleeve). I also used some 6N Jupiter 23 awg copper wire for the tweeter unit which I already had laying around the house...

OSIB16 · « **Reply #4 on:** 19 Dec 2018, 12:58 am »

CIRCUITS BEFORE MODIFICATIONS...

OSIB16 · « **Reply #5 on:** 19 Dec 2018, 01:08 am »

TWEETER HAS AN OBSTRUCTIVE SHIELD COVER (DETRIMENTAL TO PERFORMANCE) WHICH I CUT OFF...

OSIB16 · « **Reply #6 on:** 19 Dec 2018, 01:14 am »

REPLACEMENT SOLID ALUMINIUM PANELS FOR THE REAR OF CABINETS...

OSIB16 · « **Reply #7 on:** 19 Dec 2018, 01:26 am »

ALL INTERNAL WALLS OF CABINET LINED WITH 4.5MM THICK WOOL (ADHESIVE BACKED)...

WOODEN BISCUITS GLUED AND SCREWED INTO EACH CORNER. THE REAR SPEAKER PANEL SCREWS ONTO THESE TO SECURE IT TO THE BACK OF THE SPEAKER...

OSIB16 · « **Reply #8 on:** 19 Dec 2018, 01:34 am »

MODIFIED CIRCUITS ON NEW REAR PANELS...

OSIB16 · « **Reply #9 on:** 19 Dec 2018, 01:42 am »

FITTED REPLACEMENT REAR PANELS...

maplegrovemusic · « **Reply #10 on:** 19 Dec 2018, 04:39 am »

Thanks for the detailed report . The million dollar question ... How does the refurb sound in comparison to stock ?

Folsom · « **Reply #11 on:** 19 Dec 2018, 05:32 am »

The tweeter cap was to stop bad beaming and make off-axis volume on par.

OSIB16 · « **Reply #12 on:** 19 Dec 2018, 02:53 pm »

Quote from: maplegrovemusic on 19 Dec 2018, 04:39 am

Thanks for the detailed report . The million dollar question ... How does the refurb sound in comparison to stock ?

Maplegrovemusic, the stock version has an attactive open sound. Imaging pretty good. Virtually no low bass. Significantly shrill treble. After the modifications the sound becomes “Shockingly Good”. It simply shouldn’t sound this good! Compared to my “SONICCRAFT MODIFIED” Martin Logan CLS IIZ electrostatic speakers; the refurbed CX50 actually produces 90% of the performance (NO WORD OF A LIE!). It does not make sense! The speakers vanish. I’m hearing solid 3D holographic imaging. Super large ‘Soundstage’ producing sounds coming from outside the living room and through the wall. Virtually zero cabinet coloration. Treble shrillness has gone. Thinness has gone. Still no low bass though. The overall sound very much reminds me of the modded CLS IIz. Jeff what the hell is going on? How does a cheap modified speaker like this, sound this realistic and amazing?

OSIB16 · « **Reply #13 on:** 19 Dec 2018, 03:00 pm »

I’M USING THEM UPSIDE DOWN. PREFER THE SOUND THAT WAY...

OSIB16 · « **Reply #14 on:** 19 Dec 2018, 03:10 pm »

REPLACED THE CRAPPY ‘2 DIN’ CONNECTOR SOCKET WITH A SET OF GOLD PLATED SPEAKER BINDING POSTS...

OSIB16 · « **Reply #15 on:** 19 Dec 2018, 03:19 pm »

I’M SITTING THE SPEAKERS ON TOP OF “DIY VIBRATION ISOLATORS” THAT I MADE OUT OF OLD PARCEL PACKING MATERIAL...

OSIB16 · « **Reply #16 on:** 19 Dec 2018, 03:24 pm »

Quote from: Folsom on 19 Dec 2018, 05:32 am

The tweeter cap was to stop bad beaming and make off-axis volume on par.

Folsom, with the cap in place I could hear a slight coloration in the treble region. After removing the cap; the treble opened up and sounded more natural.

Jeff · « **Reply #17 on:** 13 Jan 2019, 08:00 am »

Well, I guess I should check in every once in awhile

I never get update notices after a thread goes awhile...

Anyway, your project looks great

I'm glad to hear it turned out. I would have not removed that phase plug/lens. But, it tends to help more on hard domes, or bright tweeters. If you say it sounds better...you are the ears on the ground

At first when you were referring to it as a cap, I thought you meant capacitor

Well done. I'm surprised you used those low copper brass BPs after being so meticulous with the wire. However, I bet they beat what you had.

OSIB16 · « **Reply #18 on:** 15 Jan 2019, 01:32 am »

Quote from: Jeff on 13 Jan 2019, 08:00 am

Well, I guess I should check in every once in awhile I never get update notices after a thread goes awhile...

Anyway, your project looks great I'm glad to hear it turned out. I would have not removed that phase plug/lens. But, it tends to help more on hard domes, or bright tweeters. If you say it sounds better...you are the ears on the ground At first when you were referring to it as a cap, I thought you meant capacitor

Well done. I'm surprised you used those low copper brass BPs after being so meticulous with the wire. However, I bet they beat what you had.

Jeff, advice is appreciated. The tweeters were definitely too bright before I cut off the phase lens. After I did this the treble smoothed significantly. The cabinets are hermetically sealed (more or less); which prevents the problem of the open sleeve copper wires oxidising. How long should I burn in the Sonicaps?

Jeff · « **Reply #19 on:** 15 Jan 2019, 09:48 am »

Quote from: OSIB16 on 15 Jan 2019, 01:32 am

How long should I burn in the Sonicaps?

I hear improvement up to ~350 hours.