Frankenspiel FS-X Bluetooth Speakers: Big Sound from a Tiny Package

Posted by Jim Tanous on November 1, 2015
frankenspiel fs-x bluetooth speaker

Once a relatively high-end category, portable Bluetooth speakers are now decidedly mainstream, with literally hundreds of options ranging from $20 generic speakers direct from China to more pricey products from companies like Bose and JBL. Readers won’t be surprised to learn that most of the cheaper Bluetooth speakers produce a sound that matches the price, and while the higher-end options can offer surprisingly good audio quality, you’re looking at upwards of $300 per speaker.

Update [2015-12-30]: Since initially publishing this review in early November, Frankenspiel has continued to experience delays in hitting its original Kickstarter shipping goals, and we have heard from several of the campaign’s backers who are understandably frustrated with the situation. A delayed Kickstarter project is nothing new, but at this point we recommend that any readers interested in pre-ordering the FS-X speakers wait to order until Frankenspiel has demonstrated its ability to ship actual product in volume to backers. Those interested can follow the company’s updates on its Kickstarter page.

Enter Frankenspiel, a London-based audio firm that aims to bring higher quality sound to the Bluetooth speaker market with both unique features and a relatively lower price point. Frankenspiel’s solution is the FS-X, a Bluetooth speaker that first debuted on Kickstarter in early 2014 and is now nearing general availability. We spent a few weeks testing out some of the first FS-X production units, and we found that while the speakers still have some minor issues, they produce a surprisingly big sound for their size. Read on for our hands-on impressions.

Design & Specifications

The Frankenspiel FS-X is a rather diminutive cube speaker measuring about 3.5-inches on each side. The front of the FS-X features a black metal grille with the Frankenspiel logo and is surrounded by a chrome trim, while the rest of the speaker is covered in a smooth glossy plastic. Its 400-gram weight (about 0.9 pounds) gives the speaker a solid feel that immediately separates it from some of its cheaper competition. Our test FS-X speakers are black, but final models will also ship with gray, white, and special edition champagne gold color options.

frankenspiel fs-x bluetooth speaker

On the back, you’ll find a micro USB port for charging, a 3.5mm audio-in port for connecting wired audio sources in lieu of Bluetooth, and an LED-lit power button. Although these input and control options appear limited, they actually offer quite a bit of functionality, as we’ll discuss later on.

frankenspiel fs-x bluetooth speaker

Each FS-X is powered by a 63mm balance mode radiator (BMR) driver, which produces high, mid, and low-range frequencies from a single, highly efficient speaker. This is a relatively new speaker technology, but it has already been implemented in products from well known firms such as Cambridge Audio.

Frankenspiel advertises a maximum sound pressure level (SPL) of greater than 100 dB, a frequency response of 80Hz to 20kHz, and a maximum 50 hours of playback time (derived from 40 hours from a Bluetooth connection and 10 hours on the remaining charge from a 3.5mm wired connection). The FS-X also supports the A2DP Bluetooth profile for higher quality audio from supported devices.


Like most Bluetooth speakers, the process to set up and start using the Frankenspiel FS-X is relatively simple. After charging the speakers for the first time (the FS-X supports fast charging when connected to an adequately-powered USB power source), you just press the power button once to turn it on. After a brief initialization period, the power button’s LED will glow red to indicate that it is ready to pair with your device.

frankenspiel fs-x bluetooth speaker

We tested the FS-X with a number of devices, including the iPhone 6s Plus, Nexus 6P, and a 2013 Mac Pro. In each case, our devices identified the FS-X as a Bluetooth audio device and made the connection, with the power button LED on the FS-X turning blue to indicate a solid signal. Once connected, the FS-X acts as any other Bluetooth audio device.

We connected our first FS-X speaker and started some listening tests, aiming first and foremost to test Frankenspiel’s impressive SPL claims. Our ears immediately told us that the FS-X was loud, but a sound meter confirmed that the right songs could indeed achieve an output of greater than 100 dB, with our maximum measurement coming in at 104.7 dB. This measurement, however, came courtesy of the first of the FS-X’s unique features: power boost.

Out of the box, the FS-X will meet or exceed the SPL of the typical Bluetooth speaker, with pop and rock songs hitting the high 90s in terms of decibels. But a special mode called power boost can increase the volume quite a bit, to as high as 110 dB as reported in the FX-X user guide. We didn’t get quite that high with our aforementioned max of 104.7 dB, but power boost was notably effective in increasing the power of these tiny speakers.

To enable power boost, you’ll need to quickly double-press the power button after the speaker is already powered on. The power button LED will quickly flash blue twice to confirm that the power boost mode is enabled, and you’ll hear a noticeable increase in audio volume. We found this process to be a bit tricky, however, as you need to time your double-press just right; too fast or too slow and you’ll mute the speaker instead. We spent a frustrating 20+ minutes trying to get our test FS-X speakers into power boost mode on the first day, but once we figured out the correct timing, using the mode going forward wasn’t much of a problem. Users will likely grow accustomed to the correct timing as we did, but there’s probably a better way to enable power boost mode that Frankenspiel could adopt for a future product revision.

frankenspiel fs-x bluetooth speaker

While power boost does indeed provide a remarkable level of volume, the FS-X suffers from the same issue faced by most speakers: distortion. At these high audio levels, any song or audio that contains low frequencies becomes painfully distorted, with tracks like Unsteady by the X Ambassadors or Divinity by Porter Robinson practically unlistenable at anything approaching the FS-X’s maximum volume. That said, tracks that focus on vocals, such as Jeff Buckley’s version of Hallelujah, sound great at all volumes.

As a single Bluetooth speaker, the FS-X sounds far better than the generic Bluetooth speakers we’ve tried in the past, but not quite as good as some of the higher end units from Jambox or Bose. Highs and mids are clear and tight, but bass is lacking, even with the speaker backed up against a wall. But the FS-X has another unique feature that really takes it to the next level.

Dual Mode

While above-average in most respects on its own, a single FS-X speaker can be teamed up with a second FS-X to form a dual mode stereo pair. Simply powering on a second speaker within 10 seconds of powering on the first speaker will automatically link the two together. The pair then presents itself for Bluetooth pairing as a single “dual mode” device.

frankenspiel fs-x bluetooth setup

With no display or other method to indicate which speaker is assigned to which channel, the FS-X once again uses the power LED to convey this important information. After enabling dual mode, the power button LED on the speaker assigned to the left channel will blink blue twice, and then turn solid blue, while the speaker assigned to the right channel will display solid red.

Using the FS-X in dual mode provides two key benefits. First, it doubles the available power, and lets users run both speakers at lower respective volume levels that still produce an effectively loud experience for the listener. This helps avoid the distortion that occurs when a single speaker is driven to the same effective volume level.

frankenspiel fs-x bluetooth speaker

Second, it provides great stereo separation that adds a new dimension to the listening experience that is absent from a single speaker configuration. Other Bluetooth speakers support stereo, but they’re usually contained within a single chassis that limits stereo separation and placement flexibility. With two separate speakers, the FS-X in dual mode lets the user position and angle each speaker for optimal sound quality in a given environment.

There are a few disadvantages to dual mode, however, first and most obviously the requirement that the user purchase a second FS-X speaker. A single FS-X speaker is currently priced at £59.99 (about $93). This is a competitive price considering its sound quality versus the competition, but you’ll need to shell out £111.99 ($173) for two speakers (if you buy them together up front). We still think this is a fair price, but the pricing advantage of the FS-X is certainly reduced at this level, with some excellent Bluetooth speakers starting at around $200.

frankenspiel fs-x bluetooth speaker

Another more minor issue with dual mode is that sound options such as mute or power boost must be performed individually on each speaker. This isn’t a deal breaker, but it would be nice to have these settings automatically synced between the speakers.

Finally, you’ll also need to consider the portability factor. As good as the FS-X and some of its competitors sound, the primary reason to buy a Bluetooth speaker like this is portability. Although two FS-X speakers in dual mode provide great sound, it also means that you’ll need to pack and store two separate speakers and, possibly, two separate charging cables. This is a relatively minor factor, but some users may prefer the convenience of throwing a single Bluetooth speaker in their bag versus managing two separate speakers.

Battery Life

As mentioned earlier, Frankenspiel advertises a maximum of 50 hours of playback time for the FS-X, with 40 of those hours based on Bluetooth and 10 on a wired connection. As these are Bluetooth speakers that most users will use wirelessly, we focused our battery life testing on Bluetooth connections only.

It’s important to note, as Frankenspiel does in its user guide, that battery life will vary based on the type and volume of music. Loud, driving songs that push the speakers harder will logically drain the battery faster than slow, quieter songs that don’t require as much energy to reproduce.

We therefore tested two scenarios: classical music (the Jurassic World soundtrack) at a relatively quiet volume that we might use in the background while writing (about 65 dB), and rock music (Fall Out Boy’s Infinity on High) at maximum volume with power boost enabled. Due to the expected length of the test, we set up a webcam to record the speaker so that we could tell exactly when the battery gave out.

With the soundtrack test, we measured 34 hours and 16 minutes, a bit shy of the 40 hours advertised by Frankenspiel but quite good nonetheless, considering that this is 34+ hours of continuous playback. With the more demanding rock music test, we only achieved 8 hours and 23 minutes, revealing just how much power it takes to drive these speakers at maximum volume with power boost enabled. While that running time may seem disappointing, keep in mind that you’ll likely go deaf listening at these volume levels for any extended period of time.


The Frankenspiel FS-X is an ambitious product, well-suited to its Kickstarter origins. With a good build quality and a distinctive look, the FS-X certainly stands out from most of the other Bluetooth speakers on the market, and it offers very good sound and impressive volume levels for its sub-$100 asking price. Pairing two FS-X speakers together also offers a unique configuration that provides some of the best stereo sound on the Bluetooth speaker market, albeit at a higher price.

frankenspiel fs-x bluetooth speaker

But fans of bass-heavy music will probably be disappointed, especially at higher volume levels, and some of the quirks of a first-gen product still exist.

The Frankenspiel FS-X will be shipping soon, and interested users can get their pre-orders in right now at the company’s online store. As mentioned earlier, a single FS-X is currently available for £59.99 ($93) in black, grey, white, or special edition champagne gold color options, while an FS-X pair can be picked up for £111.99 (about $173). A number of FS-X accessories, including a neoprene carrying case, dual-port fast charger, and volume control cable, are also available for pre-order.

5 thoughts on “Frankenspiel FS-X Bluetooth Speakers: Big Sound from a Tiny Package”

Testingplease says:
hey how’s delivery going now, eh?? I am SO glad I didn’t get involved with these clowns at Frankenspiel…TWO years now since the Kickstarter posting….
Foobuz says:
@bazpoint: You fool! If Frankenspiel doesn’t get more pre-orders, they will run out of money for the guy who posts weekly “updates” 😉 If they actually are developing the speaker, they must have run out of money a long time ago… The speakers should have arrived ~1.5 years ago… and I don’t think they will pay the extended development phase out of their own pocket(s?). If this pyramid scheme ends too early, I (early backer) will not receive my reward…. as long as it continues, I can still hope.
John Halpern says:
The Review would benefit from mentioning that Frankenspiel next plans to roll out a dedicated subwoofer that will pair with the FS-X – which, hopefully, will “fix” the issue of low bass reproduction as described in this review. I also am a Kickstarter Backer but I’ve been “spoiled” by being one of the lucky few to have a pair of these early pre-release FS-X to test them out and comment back at Kickstarter. Having the speakers does A LOT to reassure that these speakers are for real and the concerns raised by others are, though totally justified, reflective also of having to live through a very very long delay in the FS-X’s release. I have not lost hope at all and I do think it quite unfair to Frankenspiel to complain that there is a scam going on here. The FS-X are great and I am listening to my pair playing right now!
bazpoint says:
I highly recommend that TekRevue remove links to the Frankenspiel website and preorders immediately. As a kickstarter backer of the FSX speakers, I have now lost all hope that this is not a scam. The final straw is in fact this review – backers were promised that no review units would be sent out until backers had been fulfilled. Clearly this is another promise broken. At this point it becomes clear that the final goal for Frankenspiel is to get as many reviews like this published that they can, hopefully pull in a few more suckers on their website to make preorders, then disappear with the loot.

I have no doubt that TekRevue have written this review in good faith, but if they continue to link to the FSX pre-ordered without a substantial warning and advice to check out the kickstarter thread linked below, then they will be complicit in the losses suffered by any poor fools who pre-order.

Adrian Joss says:
Before anyone buys these speakers they should check out the Kickstarter backers comments https://www.kickstarter.com/pr….

The chances of losing any monies you pay for pre-ordering are quite high. Frankenspiel is a company that has not conducted it self well, and this is at least the second time they have setup a company doing the same thing. Please Please Please air on the side of caution when parting with any monies.


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