Bang & Olufsen Beovox 100 OVERHAUL PROJECT

OSIB16 · « **on:** 18 Oct 2018, 03:54 pm »

Hi Jeff,
I’m building a music and home cinema system using classic B&O BEOVOX 100 loudspeakers from the early 1990’s. They are wonderful and classy with their solid aluminium cabinets.
I would like to upgrade the internal components to Mundorf Silver/Oil and Neotech Copper hookup wire. It appears to be a very simplistic design, judging by the photos below. There is a Bipolar Capacitor that has the following ratings...

6u8
63v
137 Phillips

Please advise me which parts I need to buy from yourself, so that I can proceed with placing an order.

OSIB16 · « **Reply #1 on:** 18 Oct 2018, 03:57 pm »

OSIB16 · « **Reply #2 on:** 18 Oct 2018, 06:05 pm »

OSIB16 · « **Reply #3 on:** 18 Oct 2018, 06:23 pm »

OSIB16 · « **Reply #4 on:** 18 Oct 2018, 06:41 pm »

S Clark · « **Reply #5 on:** 18 Oct 2018, 07:20 pm »

Did they really put a piece of foam over the tweeter???!!! HOLY ---- that's a huge amount of deadening. Perhaps they are using the foam to drop the high end??? Never seen that before, except for some old JBL's.
First, get some foam and tweek with cutouts to find out what they were doing. If you must have covers rig some cloth over it and cut out the area in front of the drivers at 45* angling out.
This will make 10x more difference than changing crossover components. But if you must, replace the electrolytic cap. Honestly, I think you are trying to make this into something it's not... a high quality speaker. But you could upgrade to an inexpensive poly or mylar cap and get some improvement over the electrolytic. I'd be reluctant to put $$ into higher quality for this speaker.

JakeJ · « **Reply #6 on:** 18 Oct 2018, 07:25 pm »

Not much in the way of visible markings on the components but they will need to be measured to have Jeff or someone help with component choices.

On a side note, Danny of GR research is offering free crossover designing so if you can send him one original speaker he could find a better solution than just swapping parts.

OSIB16 · « **Reply #7 on:** 18 Oct 2018, 07:55 pm »

SClark,
Its not foam. It is a boxed plastic frame with thin acoustic fabric wrapped over it.

OSIB16 · « **Reply #8 on:** 18 Oct 2018, 07:59 pm »

JakeJ,
Because this speaker is a basic D’Apolitino design with 2 bass/mid drivers sandwiching a single tweeter, I thought maybe Jeff could help me start from scratch somehow.

S Clark · « **Reply #9 on:** 18 Oct 2018, 09:30 pm »

Quote from: OSIB16 on 18 Oct 2018, 07:55 pm

SClark,
Its not foam. It is a boxed plastic frame with thin acoustic fabric wrapped over it.

Well, the photos sure fooled me. So ignore everything I said except to swap that capacitor for something a bit better. I'd bet it's a 6.8 uF cap at 63V. Any decent poly cap should do a better job, won't cost an arm and a leg, and will give you some idea if you need to go further. As someone mentioned, Danny would design a crossover for free, and no one could make it sound better, but he doesn't use cheap parts. One advantage is that you only have one crossover to build.

FullRangeMan · « **Reply #10 on:** 18 Oct 2018, 11:16 pm »

The acoustic internal treatment are poor try this:
https://www.audiocircle.com/index.php?topic=100689.0

OSIB16 · « **Reply #11 on:** 18 Oct 2018, 11:21 pm »

Thanks for the heads up SClark, I’ll bear that in mind. A 6.8uf Mundorf capacitor would probably be so large that it wouldn’t fit inside the speaker cabinet. Instead perhaps I should just replace the internal wire with some cotton covered Neotech wire (this made a significant difference on my Monitor Audio Radius). However I did find the following interesting info about the CX100 on a Dutch website...

Re: BEOVOX CX100 filter???
door adijk » di 12 feb 2013, 18:32

Kleine aanvulling over wat ik op het net heb gevonden:

"The bottom woofer is connected in series with a a coil, as expected. The top woofer however, is connected in series with this coil and another coil that is paralleled with a capacitor. A weird thing about this second coil is that it has an iron core, just like a transformer. I thought this led to unlinearities.
The tweeter is connected in series with the lower woofer and bypassed by the first coil and also in series with the upper woofer - coil/capacitor combination.
I suppose the coil/capacitor is a bandstop filter. In conjunction with the other coil it will probably attenuate all frequencies exept the lower bass range to the top woofer. And the tweeter must in some way be affected too, but it is unclear how. It is clear however, that the two woofers will not have the same frequency response."

OSIB16 · « **Reply #12 on:** 19 Oct 2018, 12:16 am »

Fullrangeman,
Thanks for that info, however I am already of the same mind as yourself when it comes to internal damping.

Ferdi · « **Reply #13 on:** 19 Oct 2018, 01:58 am »

@OSIB16 - Those are nice-looking speakers.

I was surprised to see some Dutch in the text. Let me know if you need help in translation.

Dutch in DC....

S Clark · « **Reply #14 on:** 19 Oct 2018, 01:59 am »

At Jeff's web site he shows a 6.8 Sonicap at $17 that should provide better detail. I'd do that before changing wiring- usually caps make a bigger difference than wire. Also, it should fit with room to spare.

OSIB16 · « **Reply #15 on:** 19 Oct 2018, 02:30 am »

17 dollars? Damn thats cheap. I wonder if it’s Bipolar.

S Clark · « **Reply #16 on:** 19 Oct 2018, 02:54 am »

Quote from: OSIB16 on 19 Oct 2018, 02:30 am

17 dollars? Damn thats cheap. I wonder if it’s Bipolar.

It's a crossover cap, so it's non polar. I can't think of a case where a crossover cap is polar.
The word on Sonicap is that they lean toward detail/analytical where Mundorfs are perhaps fuller and more musical... but this is a center channel. It's mostly about clarity of the spoken voice. Clean and detailed is what I would want in that position. But email Jeff and ask him if he doesn't chime in here soon.

OSIB16 · « **Reply #17 on:** 19 Oct 2018, 05:13 pm »

SClark, its not a centre speaker, I merely turned it on its side for easier access to the inside. This is a hifi stereo speaker which comes as a pair. If you read that excerpt I took from a Dutch website, it explains that there is significant amount of filtering within the circuit design; which attenuates the treble and midrange at higher volume levels. I think that this may be detrimental to the transparency capabilities of this speaker. Can’t get hold of Jeff unfortunately.

Jeff · « **Reply #18 on:** 22 Oct 2018, 06:27 pm »

Dan,

Thank you for contacting me direct. Since I do not use this site like others, I'm not constantly checking in.

As I had guessed, it is a 2.5 way series network. And, as I had mentioned, your plan to mount the front three on their sides is flawed due to their intended dispersion.

Any attempt to convert them to a MTM is flawed because the two 4" drivers are different, so removing the large coil, and reducing the value of the smaller coil is not recommended.

You could try adjusting the toe in/out on the L/R for best results (prior to modification). The L/R would need to be mirror imaged whether mids were in or out. However, I just have a hard time seeing the center working out. The angled face plate will likely be working against you as well.

If the front three were mounted vertical, I would still need a description of what you felt lacking before making parts recommendations. The electrolytic would have to be replaced, but an air core replacement for the small coil would depend.

OSIB16 · « **Reply #19 on:** 22 Oct 2018, 10:19 pm »

Jeff,
OK so I have no choice but to use the CX100 in a vertical dispersion configuration. I will not turn them over onto their sides. As for my opinion of the sound quality of these speakers in an unmodified state; I mostly agree with your assesment over the telephone where you described the sonic signature as mostly Neutral, but with a slightly soft treble. However I do not agree that they are laid back. To my ears they are not Laidback and they are not Forward. I would class them as walking the fine tightrope between the two. You also critiqued them as lacking in Dynamics.