[OSIB16]

I’m nearing the completion of extensive modification's that I’m doing to the ALUMINIUM ‘three way’ B&O BEOVOX CX100 speakers. Please bear in mind, that this is mostly an experiment at this point, which is to achieve the same level of pinpoint soundstage imaging that I’m hearing from the smaller ‘two way’ BEOVOX CX50, without losing any bass. Here is a list of the tasks…

SIMULATED WOOD FINISH (painted and stained).

ABSOLUTE PUREST/MINIMALIST DESIGN.

ADD BASS REFLEX TUBE (directly behind mid/bass driver).

DISCONNECT LOWER WOOFER.

REPLACE PLASTIC REAR SPEAKER PANEL WITH BILLET ALUMINIUM.

INSTALL SINGLE ‘AUDIO NOTE KAISEI’ ELECTROLYTIC CAPACITOR (note: The Audio Note factory assured me that it was suitable for loudspeaker use).

JUPITER COTTON COVERED 20AWG SOLID CORE COPPER WIRE - FOR TWEETER (99.99% PURITY).

NEOTECH UPOCC COTTON COVERED 18AWG BARE SOLID CORE COPPER - FOR MID/BASS DRIVER (99.9999% PURITY)

REMOVE SOME PILLARS ON THE MID/BASS DRIVER (to increase airflow, which will hopefully boost the bass response).

LINE THE REAR BASKET OF MID/BASS DRIVER WITH A LAYER OF ‘CLOSED CELL FOAM’.

DIRECT TO SPEAKER CONNECTION (clamp your favourite speaker cable directly onto protruding jumper wires from the internal circuit board).

LINE THE INTERNAL WALLS OF SPEAKER CABINET WITH OPEN CELL FOAM.

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[Nick B]

Nice to see you working on another B & O project 👍

[xschop]

Enjoying all these mods/ideas. Did you foam the inside frames of the baskets? I found this clears up the midrange from reflected back-waves. I'd be glad to donate a set of billet phase plugs for your mids if you'd like to try.

[OSIB16]

Nice to see you working on another B & O project 👍

Thanks, hopefully this gamble will pay off, and these things will actually produce some bass. Also bearing in mind that the BEOVOX CX50’s are already significantly hot in the treble region; Jeff Glowacki at Sonic Craft advised me to use 99.99% pure Jupiter copper solid core for the tweeter jumper wires, which is softer sounding, instead of the Neotech UPOCC equivalent which he said can tend to aggravate this problem.

[OSIB16]

Enjoying all these mods/ideas. Did you foam the inside frames of the baskets? I found this clears up the midrange from reflected back-waves. I'd be glad to donate a set of billet phase plugs for your mids if you'd like to try.

Yes I did foam the inside frames of the baskets. Thanks but I’m gonna stick with the original mid/woofer design. I’ll let you know if it was a good idea to Dremel off those basket pillars. Hopefully there will be some bass.

[xschop]

Well, do we have a verdict on the frame window/foam mods?

[OSIB16]

Well, do we have a verdict on the frame window/foam mods?

Here’s the verdict… Crazy holographic 3d imaging. Zero cabinet coloration. Treble is vastly improved and much smoother. The bass response is very slightly more extended than before, but ultimately it is still too bass light overall. I think that at some point in the future, I will be sending them to Danny Richie to see what he can do with them.

[xschop]

Bravo. That's what I experienced from my build. I did not cut the windows out, but did indeed foam the inside of every frame upright. Thank you for sharing.

[Danny Richie]

An inexpensive poly cap would be a nice step up over that electrolytic cap on there.

[OSIB16]

       Danny, I’m not being sarcastic here, but instead I am trying to learn new things. Please educate me on your quote below. Bearing in mind that that the capacitor I used is a state of the art ‘Audio Note Kaisei’ non polar electrolytic, which is super high end, and on a par with or better than the classic Black Gates.
      How can an inexpensive Polycap sound better than this? Audio Note assured me that the Kaisei capacitor can be used in speakers.
      I’ve previously tried a 6.8uf Sonicap Gen I in this speaker. The result was a ‘hot treble’ and no ‘low bass’.

An inexpensive poly cap would be a nice step up over that electrolytic cap on there.

[Hobbsmeerkat]

To be fair, as I mentioned previously in the other thread, this speaker uses a series network, so when you change one component, it changes the response of both drivers.
So trying to compare the speaker with a 6.8uF cap against a 5uF cap in a series network is essentially apples to oranges. (regardless of brand/variety)
To get a proper comparison, you need to try a 5uF against another 5uF.

"Audio Note assured me that the Kaisei capacitor can be used in speakers."
That's a rather moot point as any non-polarized cap can technically be used in any speaker crossover.

[Danny Richie]

       Danny, I’m not being sarcastic here, but instead I am trying to learn new things. Please educate me on your quote below. Bearing in mind that that the capacitor I used is a state of the art ‘Audio Note Kaisei’ non polar electrolytic, which is super high end, and on a par with or better than the classic Black Gates.
      How can an inexpensive Polycap sound better than this? Audio Note assured me that the Kaisei capacitor can be used in speakers.
      I’ve previously tried a 6.8uf Sonicap Gen I in this speaker. The result was a ‘hot treble’ and no ‘low bass’.

A state of the art electrolytic cap huh?

That is a bit like saying you have a state of the art butter knife, and wondering why it won't cut your steak.

That electrolytic cap can be the end all be all of electrolytic caps and still not be close to an inexpensive poly cap.

Hobbs is right about the value that you used. In a series network the value of the cap effects the woofer as well. A little value shift moves one in one direction and one in another. It could easily make the response have a hot spot.

[OSIB16]

A state of the art electrolytic cap huh?

That is a bit like saying you have a state of the art butter knife, and wondering why it won't cut your steak.

That electrolytic cap can be the end all be all of electrolytic caps and still not be close to an inexpensive poly cap.

Hobbs is right about the value that you used. In a series network the value of the cap effects the woofer as well. A little value shift moves one in one direction and one in another. It could easily make the response have a hot spot.

Ok, so a Film Cap is better than an Electrolytic for speakers circuit boards. However, I wonder if I have curtailed (i.e. reduced) the low bass of this speaker further, when I went from 6.8uf to 5uf. It definitely turned down the hot treble though, which is a good thing.

[xschop]

I was prepared to add a 0.5 ohm wire-wound resistor to the tweeter circuit just by reading comments on the CX100 before I started the build. Following your tweeter modification (removing phase-plug plastic piece), I took it further and stuffed the back-chamber with wool and added wool around tweeter. This coalesced the drivers where I look forward to near-field sessions daily.

 

[OSIB16]

I was prepared to add a 0.5 ohm wire-wound resistor to the tweeter circuit just by reading comments on the CX100 before I started the build. Following your tweeter modification (removing phase-plug plastic piece), I took it further and stuffed the back-chamber with wool and added wool around tweeter. This coalesced the drivers where I look forward to near-field sessions daily.

Bearing in mind that my modified speaker pictured is a CX50 circuit installed into a CX100 cabinet (lower woofer has been disconnected. I also need to you to understand that a standard unmodified BEOVOX CX100 does not have an overbright treble issue. However, a standard unmodified CX50 does suffer with an overbright treble issue.