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Surround Sound with Beolab speakers and none B&O TV

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Ravsted
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Ravsted Posted: Thu, Jan 21 2021 11:38 AM

Hi,

sharing some experience on this topic. I had some spare Beolabs so I decided to change to surround.

I considered getting a BV, Almando or another HDMI ARC to Preout gadget. But I ended up with this <100$ solution. I bought a secondhand AV Receiver with preout.

 

Setup:

Rear: Beolab 4000

Front: Beolab 4000

Center: Beovision 7 stand with Beolab 7.2

TV: Sony Bravia 55" with custom frame of hardwood

Receiver: Harman Kardon AVR 255

Control: Beo4 supported by Lintronic

Preout / PowerLink

The receiver has preout but I don't want to use the line input of the speakers. I decided to build a RCA to Powerlink box with trigger signal injected via USB. The center RCA input delivers the same signal to Powerlink L/R channel. There are two Powerlink sockets for both front and rear allowing to use one cable per speaker or only one cable if they are looped through a speaker with two sockets.

The result:

 

 

Problems and solutions:

I soldered PIN 2 (audio ground) to PIN 7 (data ground) but still had hum in the speakers. The root cause was the USB trigger cable which was connected to a USB socket of the TV. The amplifier has a power socket which turns on/off with the amp. I moved the trigger cable to a phone charger connected to the amp power socket. Problem solved.

 

Integration & ToDo's

LinTronic TT455-RT-238 is programmed to control Sony TV and Harman Kardon. No downsides.

I did consider using BL3's as front speakers but for pure esthetic reasons I selected the BL4000. Just looks great that front and rear are identical.

Considering adding a sub. I will probably build it myself to allow it fitting under a sofa.

Will post some more pictures.... but there is still some cable management to do Smile

 


Guy
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Guy replied on Thu, Jan 21 2021 12:25 PM

^ Great project and the end result looks very professional!  I like such cost effective solutions to B&O connectivity Smile

One question:  For the centre channel, is it safe/advisable to effectively bridge the L/R inputs of the BeoLab 7.2 - I am no expert but doesn't this cause problems with input impedance?  However, if you are using some kind of auto calibration for the surround amp, perhaps this is cancelled out once the amp automatically adjusts the level of the signal sent to the centre channel.

Ravsted
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Ravsted replied on Tue, Jan 26 2021 8:34 PM

Regarding the center channel.

I see no risk to provide the left and right channel with the same input. It is the 'mono' pre-out output from the AVR center channel which is splittet and connected to both left and right channel in the powerlink socket. It allows me to connect any BL7 range speaker.

 

I set the speaker distance, dB gain and crossover manually in the AVR. Very pleased with the result.

 

 

 

leosgonewild
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Very nicely done! I will try this myself Smile
Ravsted
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Ravsted replied on Wed, Jan 27 2021 8:17 PM

Thanks... If you want the files of the 3D printed RCA/Powelink case, then just let me know. I made the case in Fusion 360 but can export to other formats as well.

leosgonewild
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I would be more interested in seeing the inside Wink
Ravsted
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Ravsted replied on Wed, Jan 27 2021 8:44 PM

Ha ha .... That can be arranged as well .... I'll create a schematic as well .... Will post it in the near future.

leosgonewild
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Looking forward to it Big Smile
Ravsted
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Ravsted replied on Wed, Jan 27 2021 9:56 PM

This is the "inside" of the RCA to PowerLink box I made.

All my speakers are connected via MKIII cables.

Full spec of PowerLink socket can be found here: BeoTech :: BeoWorld Technical

If someone knows in which scenarios it is needed to shorten PIN 2 and 7 I would like to know. 

I did it because I read in a different post that it is needed to avoid humming in the speakers. But is that the case for both AB amps and D (IcePower) amps ?

depe
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depe replied on Thu, Jan 28 2021 2:14 AM

I am not 100% certain, but i believe that the ground must be shorted, no matter whether the amps are class AB or D. I use a prepro from Emotiva with a trigger out, so no noisy USB connection needed. Not sure if your AVR has that port.

Ravsted
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Ravsted replied on Tue, Mar 16 2021 10:04 PM

Lab2 moved in.

5.0 is now 5.1

:-)

tuttivini
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tuttivini replied on Wed, Mar 17 2021 12:54 PM

@Ravsted: Oh my god, what a beautiful solution! I want such a box soooooo badly!!!

Not sure if I can make this myself (I have a 3d-printer at work and I can hold a soldering iron...), do you also sell/make them?

If I have such a wonderfull box, I could look for a small form factor AV preamp, like a Canton Smart Connect 5.1

I can't use a full AV-receiver (with unnecessary power amplifiers) because they are too big to place under my self made TV wall/floating shelf) (see attached photo).

I have a beolab 7.1 and two beolab 8000 mk2's. I've connected the to a B&O Playmaker. So this is only stereo sound. In fact, this give 'double stereo' sound (left beolab 8000+left side beolab 7.1 and right beolab 8000 + right side beolab 7.1). Of course this does not sound optimal and I would like real 3.0 (or in future 5.0 or 5.1) sound.

Your box, with the centre channel internally connected (so it is connected to both the left and right channel, because I want to use it on a beolab 7.1) would open up possibilities for me!

Small form factor all-in-one AV pre-amplifier and streamer (I could hide this underneath my floating shelf. The same way as I installed my PlayStation 4). Hoping The USB port (only for 'service) on this device is providing 5v when device is on and 0v when device is switched of, so I can use this for the usb-triggering on your box):

Ravsted
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Ravsted replied on Thu, Mar 18 2021 11:42 AM

Hi,

no... I don't sell the box. It's too labor intensive and I would not take the risk of making a bad soldering causing trouble for you.

But here you have the files for printing. I printed in PLA with 100% infill and no support. You can print in other materials as well (e.g., PETG)

Part 1

Part 2

The files are an updated version with sockets for 5.1 setup.

I used these DIN/RCA connectors:

Elextra, DIN 8 270 degrees for cabinet

Ebay, RCA gold plated

Everything is held together with plate screws 3,5 x 9,5 mm. (or shorter)

The LFE/SW channel is soldered the same way as the center channel.

I screw all the DIN connectors upside/down to a piece of wood while soldering.

Good luck

Regards

Ravsted

 

 

 

 

 

tuttivini
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tuttivini replied on Thu, Mar 18 2021 8:39 PM

Edit: double post 

tuttivini
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tuttivini replied on Fri, Mar 19 2021 2:31 PM

Ravsted has helped me very well and extensively by email.
I will soon be working on the construction of this rca> powerlink converter. 

Maybe I'm not going to replace my 7.1 and 8000's for a Stage or Sonos Arc soundbar after all...
Instead buying extra rears, like the beolab 3 or 4's Lets have a Party !!!

 

tuttivini
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tuttivini replied on Tue, Mar 23 2021 2:27 PM

Received The av pre-amp. 
Ordered the DIN, plugs, RCA plugs and 24awg 6 color wiring.
Going to print the STL files, received from Ravsted.
Hoping to solder everything correctly.
I'll keep you updated.

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