Category Archives: Audio

Running the MOTU M4 USB audio interface without bus power

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The MOTU M4 is a high quality, yet relatively affordable USB audio interface with 2x XLR/TRS in, 2x TRS in, 2x TRS/RCA out, 2x TRS out, 1x headphone out, 1x MIDI in, 1x MIDI out. The M2 is very similar, just without the 2x TRS in and 2x TRS out. Judging by the firmware, I am tempted to claim that the M2 and M4 are technically identical, just with a different back panel with fewer connectors hooked up to the ADC/DAC.

Some high-end audio interfaces have a separate power input, but the M4 is exclusively bus-powered. In theory you only need the separate power supply when your computer does not supply enough power, but the M4 is well within the limits of what the specification guarantees. The M4 actually also has a standalone mode where you can use it as a mic preamp by connecting it to a USB power supply. However, like most audio interfaces, it has one power-related downside: it makes the speakers pop when it is turned off. Some people say it’s on the quieter end of the spectrum of audio interface popping, but I would rather have complete silence when I reboot or shut down my computer. Interestingly, MOTU managed to make it completely quiet when powering on. I tried a powered USB hub, but its power output is still controlled by the computer, so the interface loses power and the speakers pop when I reboot my computer.

There is a simple solution to this problem: the USB-C/PWR Splitter by 8086 Consultancy. You can use it to power the M4 from a USB power supply, but connect its data lines to your computer as usual. This solution may also work with some other USB interfaces, but it’s not guaranteed that the interface will keep its output powered when it loses the data connection to the computer.

There is also a significantly more expensive solution: the MOTU M6, which can optionally be powered by a separate but included power supply. You might also shop around for other audio interfaces with separate power connectors (Focusrite Scarlett 8i6 Gen3, Arturia MiniFuse 4, Universal Audio Volt 4), but it’s not guaranteed that all of them will keep running when they lose the data connection to the computer. I picked the MOTU M4 because its case and knobs are mostly metal. My previous audio interface had some parts made from soft-touch plastic, which after about a decade began getting stick and shedding drops of plasticizer, so I was not going to spend money again on soft-touch plastic like on the Arturia’s knobs.

Active PA speaker systems

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During my high school time, I did a lot of work as a sound technician and lighting designer at all kinds of events, both as a volunteer at school and outside of school. Recently someone from the school told me that they were looking at buying a new portable speaker system, both to replace their old/broken/underpowered one and because they were paying more than a thousand euros in rental fees for additional speakers every year. They asked me if I could help them choose one. We quickly reached the conclusion that active speakers were the way to go because of their flexibility and because they would often be operated by people who didn’t know a lot about all the technical stuff.

We ended up narrowing it down to three candidates: the Yamaha DSR series, the JBL PRX600 series, and the QSC KW series. These are the top-of-the-line active systems the largest and most reputable speaker manufacturers have to offer, as of early 2012. The next step was to find a place where we could listen to all three and compare them. Thomann, the largest online shop for musical instruments and PA equipment in Europe, where we have been buying sound equipment for years, has a huge store and showroom in a small town in northern Bavaria. They ordered and set up all these speakers for us and let us listen to them for more than an hour. If the friendly sales guy ever grew tired of listening to our test songs like “He’s A Pirate” by Klaus Badelt or “Man in the Mirror” by Michael Jackson over and over again, he certainly didn’t show it.

We almost immediately ruled out the QSC: We had the QSC KW 153 three-way 15″ top coupled with a QSC KW 181 18″ subwoofer set up, but the mids and highs just sounded muddy.

Some other speakers we temporarily had in the test were some JBL Eon (by accident), which just sounded cheap compared to the others, and some RCF Art, which had crisp and powerful base, but not exactly outstanding highs.

Now we only had the JBL PRX 615 two-way 15″ top coupled with the JBL PRX618-XLF 18″ subwoofer and the Yamaha DSR 115 two-way 15″ top coupled with the Yamaha DSR 118W 18″ subwoofer left over. We tested and compared them for almost an hour: sometimes we tended towards the JBLs, other times we liked the Yamahas more.

The JBLs sounded very smooth (if you want to be mean, you could call them a tiny bit muddy) and their base stretched down to 30 Hz. On the other hand, the Yamahas had super-clear mids and highs and very precise and crisp base. After quite some discussion, we decided to go with the Yamahas. Another advantage was their significantly lower price and their more advanced DSP circuitry to protect the speakers.

They got delivered a few days ago and so far we’re really happy with them. They sound amazing: Perfect for the school’s numerous music performances. And they are powerful: Perfect for events like dances and parties.

If you’re looking for a set of high-quality portable speakers for a school, church, band or DJ, the Yamaha DSR series is most likely your best choice. They sound great, have lots of power and are well worth their money.

If you just use them for speech, a set of Yamaha DSR 112 would probably be a fine choice (I didn’t test the DSR 112, but assume they’re as good as the DSR 115 with a little less low-mids). If you’re using them for a band, go for a set of DSR 115, and if you have drums, base or anything else below 120 Hz, definitely get a pair of DSR 118W subwoofers along with them. Same goes for DJ and party use: a pair each of DSR 115 and DSR 118W should suffice to bring high-decibel, high-quality sound to a few hundred audience members.

If you have experiences with the Yamaha DSR (or the recently-released smaller DXR and DSW series), or have found other speakers in the same price range that sound better, please feel free to share them in the comments.