Practice test: Nubert NUBOX A-125 as a space-saving replacement for the Klipsch R-15PM in the near field and a lot of fun playing

The housing interior

So, screw up and look in curiously! The back of the active box carries the mounting plate, which houses all the connectors. The actual technology, including the boards, is inside and carried by this plate. But before we get to the electronics, I quickly show the inside of the box. It is very nice to see how the MDF body has been glued and that additional contra-angle handpieces increase the stiffness. The fact that these are only glued in the aftermath is also shown by the different adhesive, which in the second step indicates manual partial production. Note: Noses are human, even if they are made of glue.

The bass reflex tube is very long and ends at an angle behind the tweeter. I had already explained the chassis assembly on the first page. All connection cables are plugged in and the connectors are also insulated. The cables are additionally coated with foam and are sufficiently long. Cable ties on the board carrier are then ensured by order and strain relief.

The switching power supply, which is positioned on a separate board at the back, provides 96 watts of maximum power, of which more than 56 watts are required in the tip, which should have hit the efficiency window of this circuit quite well. So, in theory, there would be much more to it. However, you can't find huge elkos on the secondary side, which makes the power supply relatively "hard" in the full load range. However, since enough power remains open, even impulses are still well supplied and there is no voltage drop.

The placement of the motherboard is quite interesting. In addition to the usual 4-channel Class-D amplifier (power amplifiers under the black heat sink), sound processing is particularly interesting. The heart of this is, as with other boards, the very flexible D2 Audio SOC (D2 92683), as it is. manufactured by Renesas. It can generate configurable and routable audio signal paths, has 12 independent PWM channels and four independent asynchronous I2S digital inputs. The digital S/PDIF audio inputs support linear IEC-61958 PCM or compressed IEC-61937 audio.

The D2 Audio not only provides channel separation as an active switch, but also has an integrated high-performance stereo ADC, real-time amplifier control and monitoring and supports various power amplifier concepts such as: bridge-bridged, semi-bridged, and bridge-tied load (BTL) topologies that use discrete or integrated power amplifiers (as used here). The effects for the stereo base width extension ("Movie") and the music preset are also part of the DSP. In theory, the chip could also decode Dolby Digital/AC3, Pro Logic IIx, Virtual Speaker, TruSurround HD4, DTS WOW HD and TruVolume.

The G13 is an MCU with CISC processor and flash memory that can store the settings and also has a decent A/D converter. For the S/PDIF you use a CS8422 from Cirrus Logic. This is a pretty good 24-bit / 192-kHz Asynchronous Sample Rate Converter with up to 140 dB Dynamic Range, -120 dB THD+N and supported sampling rates of up to 211 kHz. And Bluetooth? Qualcomm (formerly Cambridge Silicon Radio Ltd) supplies this chip in the form of the CSR A64215 with integrated Balun antenna (sending and receiving). The chip supports AVRCP v1.6, TrueWireless Stereo (TWS), Secure simple pairing as well as CSR's Proximity Pairing and decoded aptX, aptX Low Latency, SBC and AAC.

Comparison to the Klipsch R-15PM: Craftmanship

Optical comparisons are of course always a bit unfair and also produce a funny aftertaste from time to time, nevertheless I would like not to withhold the inside and exterior of the more expensive active speakers from Klipsch at least visually, since I always want to at the beginning again on quality. The first image shows the board stack of the then loading new R-15PM. Apart from the fact that only the second delivery worked at all (thanks to Amazon for the unbureaucratic handling!), such a delivery state in this price range is completely indisputable, especially since I had to solder several times.