A good wireless speaker comes down to a few physical things: drivers made of stiff, light materials, a sensible split of the frequency range between them, enough clean amplification for each, and a cabinet that stays out of the way. Power figures only mean something if they are honest, which is why Mitchell Acoustics quotes every uStream speaker in RMS watts rather than peak.
What makes a good wireless speaker?
Strip away the wireless part and a speaker is a simple chain. A signal arrives, an amplifier makes it strong enough to move a driver, and the driver pushes air. Every link can add something that was not in the recording: distortion, resonance, a smeared sense of timing. Good design is mostly about keeping those additions small.
Wireless adds two jobs. The speaker needs its own amplification, because there is no separate amplifier, and in a stereo pair the left and right speakers need a way to stay in step with each other.
Driver materials: magnesium alloy, silk composite and ceramic aluminium
A driver's diaphragm (the cone or dome that moves) has a hard brief. It should be stiff, so it moves as one piece rather than flexing, and light, so it starts and stops quickly. It should also be well damped, so any resonances it does have die away instead of ringing. No material is perfect at all three, which is why different drivers in the range use different ones.
Magnesium alloy. Used for the 106mm drivers in the uStream Cube and uStream One, and the 165mm woofer in the uStream Two. Magnesium is one of the lightest structural metals, and among metals it has relatively good internal damping, so it combines rigidity with a less aggressive character than some harder metals.
Silk composite. The tweeters in the uStream One and uStream Two are silk composite domes (38mm and 32mm respectively), and the uStream Three uses a 76mm silk film tweeter. Soft domes are naturally well damped, which tends to give smooth treble without hardness or glare.
Ceramic aluminium. The uStream Three's 120mm mid-range and 165mm woofer use aluminium diaphragms with a ceramic treatment. The aim is greater stiffness than plain aluminium, so the cone stays controlled when it is working hard.
The portable uStream Go uses an 80mm driver with a metal alloy diaphragm, backed by a 68mm passive radiator. A passive radiator is an unpowered diaphragm that moves in response to air pressure inside the cabinet, extending bass in a small enclosure without the port noise a reflex port can add.
Two-way vs co-axial vs three-way speakers
No single driver reproduces the whole audible range well. A cone large enough for deep bass is too heavy for crisp treble, and a small dome that handles treble cannot move enough air for bass. So most speakers split the job. The uStream range shows three approaches.
Single full-range driver: uStream Cube
The uStream Cube uses one 106mm magnesium alloy driver per speaker, with a quoted response of 30Hz to 18kHz. One driver means no crossover, so there is no handover point between drivers to get wrong, and the sound comes from a single source. It is a simple, coherent way to build a compact speaker.
Two-way: uStream One
The uStream One pairs a 106mm magnesium alloy bass/mid driver with a 38mm silk composite tweeter, for a quoted 33Hz to 20kHz. Each driver works in the range it suits, which lowers distortion and improves detail at the top end.
Co-axial two-way: uStream Two
In a conventional two-way speaker, the tweeter sits above the woofer. That vertical offset means sound from each driver travels slightly different distances to your ears, and the difference changes as you stand, sit or move. The uStream Two mounts its 32mm silk composite tweeter on the same axis as its 165mm magnesium alloy woofer, sharing one back plate and magnet assembly. Both drivers radiate from the same point, so their timing relationship stays consistent across the listening area. The practical result is a more focused image that holds together better off-axis.
Three-way: uStream Three
The uStream Three gives treble, mid-range and bass a driver each: a 76mm silk film tweeter, a 120mm ceramic aluminium mid-range and a 165mm ceramic aluminium woofer. The key benefit is for the middle of the spectrum, where voices and most instruments live. When the woofer is making large movements for bass, a driver that also handles vocals can add intermodulation distortion (the bass modulating everything else). Giving the mid-range its own driver keeps voices clean when the bass is working hard.
Why does each driver having its own amplifier matter?
In a typical passive speaker, one amplifier channel feeds a crossover network of coils and capacitors, which then splits the signal between drivers. That network sits between the amplifier and the drivers, consumes some power, and has to cope with a load that changes with frequency.
When each driver has its own amplifier, the signal is split before amplification instead. This is called bi-amping for two drivers and tri-amping for three. Each amplifier only has to drive one driver across a limited range, which makes its job easier and gives it tighter control over that driver. A demanding bass note also cannot pull power away from the tweeter, because they do not share an amplifier.
Across the range: the uStream One gives its woofer and tweeter separate amplifiers. The uStream Two is bi-amped, with a Texas Instruments TPA3116D2 Class D amplifier on the woofer and a separate amplifier on the tweeter. The uStream Three is tri-amped, with a Texas Instruments TPA3116D2 for each of its three drivers.
Class D amplification and neodymium magnets
Class D amplifiers work by switching their output transistors fully on and off at very high speed, then filtering the result back into an audio signal. Because the transistors spend almost no time half-on, they waste far less energy as heat than traditional linear designs; efficiencies of around 90 percent are typical. In an active speaker, that means plenty of power from a compact board without large heatsinks. The uStream Cube, uStream One, uStream Two and uStream Three all use Texas Instruments Class D amplification (on the uStream Two, for the woofer).
Behind every driver is a magnet and a voice coil. When current flows through the coil, it pushes against the magnetic field and moves the diaphragm. Neodymium magnets produce a much stronger field for their size and weight than traditional ferrite magnets, which gives the motor more control over the diaphragm. On the uStream Cube, uStream One, uStream Two and uStream Three, the voice coil is a proprietary design with a 20oz (566g) neodymium magnet. On the uStream Two, the co-axial woofer and tweeter share the magnet's back plate.
RMS vs peak watts: which number should you trust?
RMS power (strictly, continuous average power, calculated from the root mean square of the voltage) describes what an amplifier can deliver continuously into its speaker without running out of headroom. It relates to how loud and clean a speaker can play over a whole song or film.
Peak power describes a brief maximum and is often measured under conditions you would never listen at. Some audio products go further with figures such as PMPO (peak music power output), which can be many times the continuous rating and have no agreed standard. A large peak figure on a box tells you very little about how the speaker performs.
Mitchell Acoustics quotes RMS throughout the range, and the per-driver figures add up openly:
uStream Cube: 35W RMS per speaker, 70W RMS system.
uStream One: 35W RMS woofer plus 15W RMS tweeter, so 50W RMS per channel, 100W RMS system.
uStream Two: 60W RMS woofer plus 20W RMS tweeter, so 80W RMS per channel, 160W RMS system.
uStream Three: 60W woofer, 40W mid-range and 20W tweeter, so 120W RMS per channel, 240W RMS system.
uStream Go: 15W RMS per speaker, 30W RMS system.
Two more things help you read any power figure. First, loudness does not scale in a straight line: doubling amplifier power gives about 3dB more output, a noticeable but modest step, and it takes roughly ten times the power to sound twice as loud. Second, power is only one part of the picture. Distortion matters too, which is why the spec sheets also quote total harmonic distortion: under 0.5% at 1W and 1kHz for the uStream Cube, uStream One and uStream Two.
How true wireless stereo pairing works
Every uStream speaker model is a pair of separate speakers, left and right, and they find each other automatically when you switch them on. No app, no Wi-Fi, no cable between them. On the uStream Two, every wired input sits on the left speaker, so nothing needs plugging into the right. Keeping left and right physically separate is the point: it lets you place the speakers apart and get a real stereo image, which we explain in why stereo still matters.
Choosing within the uStream range
The uStream Cube is a compact full-range pair and the entry point. The uStream One adds a dedicated tweeter and more inputs. The uStream Two brings the co-axial driver and more power for larger rooms, and the uStream Three is the tri-amped three-way flagship. Every pair is Designed in Britain and carries a 2-year no-quibble warranty. You can compare them all on the uStream range page.
Frequently asked questions
Is RMS or peak power more important?
RMS. It describes continuous output, which is what you actually listen to. Peak figures describe a brief maximum and are often inflated, so they are a poor basis for comparing speakers.
Is a three-way speaker better than a two-way?
Not automatically, but a well-executed three-way lets a dedicated driver handle the mid-range, which keeps voices cleaner when bass is heavy. It also needs a larger cabinet, so it suits bigger rooms.
What is a co-axial speaker?
One where the tweeter is mounted on the same axis as the woofer, so both radiate from a single point. This keeps their timing consistent as you move around the room.
For the other half of the story, see how placement shapes what you hear in setting up for a better centre image.
