SynchCast vs VoiceMeeter vs Virtual Audio Cable vs Windows 11 Shared Audio

If you want the same audio coming out of two devices at once on Windows, you have four realistic options. They are not variations on the same idea — they are genuinely different tools built for different jobs, and picking the wrong one is why so many people give up and decide it isn't possible.

This is a straight comparison. I build one of these four, so read the SynchCast section with that in mind — but the criticisms of the other three are the same ones I'd give a friend, and each has a situation where it's the right answer.

The short version

The column that matters most and gets discussed least is "fixes sync drift". Getting audio to come out of two devices is the easy part. Keeping it aligned for two hours is the hard part, and it's where most setups quietly fail.

Why sync drift is the real problem

Two things go wrong when you split audio to several outputs, and they're often confused.

Latency is a fixed offset. Bluetooth has to encode, transmit and decode, which typically costs 100–300ms depending on the codec. Wired output is nearly instant. So one device is simply behind the other, constantly, by a fixed amount. This one is easy to fix: delay the faster device to match.

Drift is the one that ruins things. Every audio device has its own crystal oscillator, and no two run at exactly the same rate. One device might play 48,000 samples per second while another plays 48,002. That sounds negligible, and for the first minute it is. Over an hour it's several thousand samples — a clearly audible echo that gets worse the longer you watch.

A fixed delay setting cannot fix drift, because the error keeps growing. You need something continuously measuring how far apart the devices have got and resampling one of them to compensate. That's the distinction that separates the four options below.

VoiceMeeter

VoiceMeeter is a virtual audio mixer. It installs a virtual audio driver, gives you a mixing desk with hardware inputs, virtual inputs and multiple outputs (A1, A2, A3, B1, B2), and lets you route anything to anything.

It's genuinely powerful. If you stream, record, need per-application routing, want to mix a microphone with system audio, or need to send different mixes to different destinations, VoiceMeeter does things none of the other three can. It's free (donationware) and has been maintained for years.

What it costs you:

• It's a driver install and a reboot. Admin rights required, and it changes your system's audio configuration globally. On managed or work machines that's often a non-starter.
• The learning curve is real. The interface is a mixing desk, not a settings page. If you don't already understand buses and routing, "play sound on two devices" is a 30–60 minute research project, and most of the tutorials assume you're streaming.
• It has a manual delay slider, not drift correction. You can dial in an offset to align two devices, and it'll sound perfect. Then come back in 40 minutes and it's drifted, because the slider is a fixed number and the error isn't. You nudge it again. That's the loop people complain about.

Pick VoiceMeeter if you want a mixer and are willing to learn one. It's the right tool for streaming and complex routing. It's a heavy tool for "both of us want to hear the film."

Virtual Audio Cable

Virtual Audio Cable (VAC) is the more focused, lower-level tool. It creates virtual cables — a playback device on one end, a recording device on the other — and you wire your audio through them. Its Audio Repeater utility can take one cable and feed several physical outputs.

It's precise and stable. For scripted or unattended setups, VAC is dependable in a way GUI tools often aren't, and it gives you direct control over buffer sizes and sample rates.

What it costs you:

• Also a driver install, so again admin rights and a system-wide change.
• You are the integrator. VAC gives you the pieces; assembling "system audio reaches these three devices in sync" means running Audio Repeater instances with the right buffer settings and keeping them running. It's configuration, not a feature.
• Buffer tuning is the whole game, and it's a trade-off with no good answer. Small buffers mean low latency but crackling when the CPU is busy. Large buffers are stable but add delay. And as with VoiceMeeter, buffers are a fixed compensation — they don't track drift.
• It's paid (around 30 US dollars for a personal licence), which surprises people who assumed it was free.

Pick VAC if you need low-level control, are comfortable with audio plumbing, or are automating something. Skip it if you want a thing that just works.

Windows 11 Shared Audio

Microsoft added a genuine built-in feature for this. In supported Windows 11 builds you can share audio to two Bluetooth devices from Quick Settings — no downloads, no drivers, a couple of clicks.

When it applies, it's the obvious choice. Free, first-party, nothing to install.

The catch is eligibility, and it's a big one:

• It requires specific, recent hardware — it rolled out on Copilot+ PCs and newer Bluetooth stacks. Most machines in use today simply don't offer it. If you don't see it in Quick Settings, there's no download that adds it; it's a hardware and build requirement.
• Two devices, both Bluetooth. You can't include your laptop speakers or a wired pair. Plenty of real setups are "one Bluetooth, one wired," which this doesn't cover.
• No drift correction. It aligns two Bluetooth devices at the start; over a long session the same clock-drift problem applies.

Pick it if you have eligible hardware and exactly two Bluetooth devices. Check Quick Settings first — if it's there, try it before paying for anything, including mine.

SynchCast

SynchCast is deliberately narrow: it does the one job the other three treat as a side effect.

No drivers, no admin rights. It uses WASAPI loopback, which is already part of Windows, to read what's currently playing and re-render it to the outputs you pick. Nothing is installed into your audio stack and nothing about your system configuration changes. Uninstalling leaves no trace.

It corrects drift continuously. This is the actual reason it exists. A PI-controlled resampler measures how far each output has drifted and adjusts its playback rate in real time. Not a delay slider you re-nudge — a control loop that holds alignment over hours. It's the difference between "aligned when I set it up" and "still aligned at the end of the film."

Up to about 5 devices. There's no artificial cap in the software, and each output gets its own render thread. But real Bluetooth radios and USB audio stacks start struggling past roughly five, so that's the honest number for glitch-free playback rather than a marketing one. Most people run two or three. SynchCast tells you roughly how many your particular Bluetooth radio can drive cleanly.

What it doesn't do, so you don't buy the wrong thing: no microphone mixing, no per-application routing, no virtual devices for other software to record from, no streaming features. If you need any of those, you want VoiceMeeter. SynchCast plays what your PC is playing on several devices at once, in sync, and nothing else. It's Windows 10 and 11 only, because WASAPI loopback is Windows-only.

Price: $10.99 once (₹299 in India), with a 30-day fully featured trial and a 14-day money-back guarantee. One computer per licence, movable between machines.

How to choose

• Two Bluetooth devices and a new PC? Try Windows 11 Shared Audio first. It's free.
• Streaming, mic mixing, or per-app routing? VoiceMeeter. It's the real mixer.
• Automating something, or you want low-level control? Virtual Audio Cable.
• You want several devices to stay in sync for a whole film, with nothing installed into Windows? That's what SynchCast is for.

Worth saying plainly: if the free built-in option works on your machine, use it. The reason the other three exist is that for most people it isn't available yet, and the two established tools were built for professional routing rather than for keeping a couple of pairs of headphones aligned.

FAQ

Do I need to uninstall VoiceMeeter or VAC to try SynchCast? No. SynchCast doesn't install a driver or claim a virtual device, so it coexists with both. If you've already routed your system audio through a virtual cable, point SynchCast at your real output devices rather than the virtual ones.

Does SynchCast work with Bluetooth and wired at the same time? Yes, and that mix is the case it's built for — it's also the one Windows 11 Shared Audio can't do. The delay difference between a wired and a Bluetooth output is exactly what the drift correction is compensating for.

Is VoiceMeeter's delay slider really not enough? It's enough for a few minutes and it's genuinely fine for a short clip. The problem is that the error grows: the slider sets a fixed offset while the actual misalignment keeps increasing as the two clocks diverge. That's why it sounds perfect when you set it and wrong an hour later.

Why is there no free version of SynchCast? There's a 30-day trial with every feature unlocked and no limitations, and a 14-day refund if it doesn't work on your hardware. After that it's $10.99 once — no subscription.

Will this work on macOS or Linux? No. It depends on WASAPI loopback, which is a Windows API. Windows 10 and 11 only.

Bottom line

Getting audio out of two devices is solved four different ways. Keeping it in sync for a long session is solved by one of them. If you're picking between these, that's the question to ask about each — and the answer for VoiceMeeter, VAC and Windows 11 Shared Audio is all "manually, or not at all."

If your PC offers Windows 11 Shared Audio and two Bluetooth devices is all you need, start there. Otherwise, try SynchCast free for 30 days and see whether it holds sync on your hardware — that's the only test that matters. The setup guide walks through picking devices and tuning per-device delay, and if you want the background on the built-in Windows methods and why they echo, that's in how to play audio on two or more devices.