roci_big_ear
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- Feb 24, 2022
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I bought one speaker out of curiosity. I wanted to see the value the speaker delivers for just $199.
What a great first impression unboxing and taking it apart!
These things are designed (thanks, Genelec!) and built (thanks, Behringer!) really well: the cabinet is dense and solid, the driver frame is cast, the circuits have good layout and soldering. Speaking of circuits: 3 TDA7293 chip amps power it, fed by a toroid transformer. At the +/-42V supply voltage, the power these chips can deliver is over 300W. This is not the 20-year old B2031A design you see reviewed online: on the outside it looks the same, but the PCB is a new revision of the now discontinued B3031A (which I have had for 10 years and like a lot).
I particularly like the front facing bass ports and the down facing rear connectors that make placement easy.
But then you turn it on... Right out of the box, my B2031A sounded very bright. Sure enough, a sweep confirmed the tweeter is 4-5 dB too loud above 4 kHz. They say it is factory calibrated... Did the technician stick the microphone in the woofer?
Thankfully, Behringer has put 2 hidden trimmers to change the level of the tweeter and adjust a ~17 kHz booster.
MOD 1
Using the factory trimmers, I decreased the tweeter level, and added a bit of a high boost to flatten it (as much as possible). This ended up in an overall flatter response, but also with a wide ~4 dB dip around the crossover frequency, which is at 1.85 kHz. Each driver is at -10 dB at that point. So overall, factory calibration was bad, but even after manual calibration, I am left with a smiley-face response.
I am starting to think the woofer cut off frequency is too low due to a wrong component value, which messed up the rest of their factory calibration.
MOD 2
It was time for more drastic measures. I removed the main PCB, took out the soldering iron and increased the woofer's low-pass filter cut off frequency a bit, so that the cross over is at 1.95 kHz vs 1.85 kHz originally. I didn't want to take out existing components (they are also glued), so I decided to solder a 47 kOhm resistor in parallel to R86 like this:
This increased the overlap of the two drivers and bumped the frequency valley by ~2 dB. Still not ideal, but better.
MOD 3
The response above 5 kHz bugged me. Not only is it not flat, but then the sudden drop off. The only reasonable course forward I could think of is to modify the 17 kHz booster. My plan was to move it to 25 kHz and counter that steep fall off. After another couple of hours of studying the board and simulating the circuit, the mod was to solder a parallel 10k resistor to R80.
Conclusion
As you can see, all the mods I did cost absolutely nothing (other than a weekend of my effort). I am dumbfounded why Behringer doesn't tune their speakers better. With all the mods, the speaker is quite nice actually.
Final response, 37-20kHz +/- 3dB.
What a great first impression unboxing and taking it apart!
These things are designed (thanks, Genelec!) and built (thanks, Behringer!) really well: the cabinet is dense and solid, the driver frame is cast, the circuits have good layout and soldering. Speaking of circuits: 3 TDA7293 chip amps power it, fed by a toroid transformer. At the +/-42V supply voltage, the power these chips can deliver is over 300W. This is not the 20-year old B2031A design you see reviewed online: on the outside it looks the same, but the PCB is a new revision of the now discontinued B3031A (which I have had for 10 years and like a lot).
I particularly like the front facing bass ports and the down facing rear connectors that make placement easy.
But then you turn it on... Right out of the box, my B2031A sounded very bright. Sure enough, a sweep confirmed the tweeter is 4-5 dB too loud above 4 kHz. They say it is factory calibrated... Did the technician stick the microphone in the woofer?
Thankfully, Behringer has put 2 hidden trimmers to change the level of the tweeter and adjust a ~17 kHz booster.
MOD 1
Using the factory trimmers, I decreased the tweeter level, and added a bit of a high boost to flatten it (as much as possible). This ended up in an overall flatter response, but also with a wide ~4 dB dip around the crossover frequency, which is at 1.85 kHz. Each driver is at -10 dB at that point. So overall, factory calibration was bad, but even after manual calibration, I am left with a smiley-face response.
I am starting to think the woofer cut off frequency is too low due to a wrong component value, which messed up the rest of their factory calibration.
MOD 2
It was time for more drastic measures. I removed the main PCB, took out the soldering iron and increased the woofer's low-pass filter cut off frequency a bit, so that the cross over is at 1.95 kHz vs 1.85 kHz originally. I didn't want to take out existing components (they are also glued), so I decided to solder a 47 kOhm resistor in parallel to R86 like this:
This increased the overlap of the two drivers and bumped the frequency valley by ~2 dB. Still not ideal, but better.
MOD 3
The response above 5 kHz bugged me. Not only is it not flat, but then the sudden drop off. The only reasonable course forward I could think of is to modify the 17 kHz booster. My plan was to move it to 25 kHz and counter that steep fall off. After another couple of hours of studying the board and simulating the circuit, the mod was to solder a parallel 10k resistor to R80.
Conclusion
As you can see, all the mods I did cost absolutely nothing (other than a weekend of my effort). I am dumbfounded why Behringer doesn't tune their speakers better. With all the mods, the speaker is quite nice actually.
Final response, 37-20kHz +/- 3dB.
Last edited:
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