Testing on the RSL Speedwoofer 10S MKII was conducted with the microphone facing the woofer at a 2-meter distance. The temperature was recorded at 49F degrees with 70% humidity. The subwoofer’s gain was set to maximum and the low pass filters were left off.

The above graph shows the measured frequency responses for the RSL Speedwoofer 10S MKII subwoofer per its operating modes. The LFE Mode holds a nice flat response from the mid-20s up to 100Hz while the Music Mode rolls off the response at around 30Hz. I used the sub in LFE Mode for my own listening, and most people would probably find that more satisfying. The extra deep bass is noticeable. Above 100Hz, the upper-frequency roll-off is gradual, and it could probably be EQ’d for a flatter response without much trouble for those who want to use a 120Hz crossover. ‘Music Mode’ will have enough frequency bandwidth for the vast majority of music recordings. Music rarely dips below 30Hz, especially in acoustic recordings. RSL may have made this mode available for instances where room gain can really boost lower frequencies which is not an uncommon occurrence. There are plenty of movies that do dig below 30Hz, so for home theater aims, LFE Mode is recommended.

The above CEA-2010 measurements are short-term bursts that show the subwoofer’s clean peak SPL before heavy distortion sets in. Our measurements have been referenced to 2-meter RMS, which is 9dB down from the standard requirement for the measurements to be shown at 1-meter peak. However most publicly available CEA-2010 measurements are shown at 2-meter RMS, so we followed that convention. The burst performance is very good for the price and size of the Speedwoofer 10S MKII. With short-term output exceeding 107dB at 40Hz and above, it is no wonder that it could rock so hard even in my medium-to-large room size. It has some real low-end grunt as well, with a recorded measurement of 102dB at 25Hz. The overall measurement set here nets our Bassaholic Room Rating on the higher end of the ‘Medium’ Room Size Rating meaning that it should be able to remain powerful in a room of up to 3,000 cubic feet.

For information on how the room ratings are determined, please read our article Bassaholic Subwoofer Room Size Rating Protocol.

However, if you don’t intend to rock hard frequently, I do think it could handle somewhat larger room sizes at moderate loudness levels. On the other hand, a dual Speedwoofer 10S MKII setup could easily handle larger rooms and still come in at under $1k. Even better, a dual sub setup is better for reducing the adverse effect of room modes and standing waves, so you can get a flatter response and a higher quality sound than is possible with a single subwoofer.

Testing for long-term output compression was done by first conducting a 20-second sweep tone where 50Hz hit 90dB with the subwoofer 2 meters from the microphone. We then conduct further 20-second sweeps by raising the gain by 5dB until no more output could be wrung out of the subwoofer. These tests show us the long-term continuous headroom that the subwoofer is capable of. The Speedwoofer 10S MKII holds its response shape up to the 100dB sweep before any compression sets in. Above that point, it does start to run out of gas in deep bass, but there is still plenty left in the tank in lower-mid bass where we see it can exceed 105dB from about 40Hz to 90Hz. Again, this is a very respectable showing, especially considering the size and pricing. 

The above graphs show the corresponding total harmonic distortion to the long-term output graphs. Essentially, they depict how linear the subwoofer remains for the corresponding drive level seen in the long-term sweeps. The quantity being measured is how much of the subwoofer’s output is distortion and is shown here as a percentage. Starting at the 90dB sweep, there is very little distortion present. However, when pushed a bit harder, harmonic distortion does start to crop up, but not in quantities that are likely to be audible at anything but the highest drive levels, at least outside of deep bass. The nature of the distortion is what starts to matter at this point, and it is what we get a look at in the following graphs…

The above graphs depict measurements of the constituent harmonics from the long-term output sweeps and are what the total harmonic distortion measurements are composed of for the 2nd and 3rd harmonics. These individual harmonics can give us a clue as to what might be the cause of some quirk or non-linearity. We are only showing the 2nd and 3rd here because they more or less reflect the higher even-order and odd-order behaviors, although higher-order harmonics tend to be much further down as a percentage of distortion compared to the second and third.

Here we can see that most of the distortion product outside of deep bass below 25Hz is largely comprised of even-order harmonics. Since it seems to increase at fairly even intervals with respect to the rising drive level, I would guess this would be due to inductance rather than a suspension or motor issue. The fact that it is notched out just below 50hz would support this; were it a matter of stress from the suspension or motor, there wouldn’t be an absence of distortion at that frequency. The good news is that even-order harmonics are more difficult to perceive than odd-order, especially in music recordings. All musical instruments produce lots of even-order harmonics of their own, so if any even-order harmonic distortions are audible at all, the listener may not even be able to distinguish them from that of the instrument. The bottom line for these measurements is that if the listener doesn’t want to be met with any audible distortion products, just don’t crank the Speedwoofer 10S MKII as hard as humanly possible.

Group delay is the measurement of how much time it takes for individual frequency bands of an input signal to be produced by the speaker. It can indicate that some frequency components are developing slower than others or are taking longer to decay. It is generally thought that 1.5 sound cycles are needed for group delay to be audible at bass frequencies, although there is an argument that group delay should remain under 20ms to be completely unnoticeable, but that is likely meant for mid and upper bass frequencies.

The Speedwoofer 10S MKII seems to average group delay a bit below 1 cycle until port tuning which should keep it below any audible decay times for pretty much any content. It does exceed 1.5 cycles below 30Hz, but that is likely too deep in frequency to be readily perceptible by human hearing. There isn’t anything else remarkable about this measured performance; it isn’t extraordinarily good but it isn’t bad at all either. This is simply a competent level of group delay, and listeners are not likely to hear any laggy bass or overhang.

For those looking for a major upgrade from the original Speedwoofer 10S, the MKII version isn’t going to have a big increase in performance. We can expect some minor increases, but since the driver and enclosure hasn’t undergone any radical changes, and since there has only been a relatively small increase in amplifier power, the improvements in headroom will be minor. One of the aspects that will have a change in performance going from the original to the MKII is the switch from front-firing port to rear-firing port. The rear is likely to be placed closer to backwalls or side walls, so it will probably get more acoustic loading in that condition, and since it the port is not facing the listener, any chuffing or port turbulence noises will be much more heavily masked. The added DSP of the MKII has over the system justifies the upgrade. The RSL Speedwoofer 10S MK II sub is bulletproof. It can sense all kinds of problems and either compensate for them or shut the system down to avoid catastrophe. It can deal with suboptimal power sources, DC offsets in the signal, signal overloading, thermal issues, and other things way better than the previous non-DSP amp.

I normally go over the strengths and weaknesses of the product under review in the conclusion of my reviews, but the problem with going over the weaknesses of the Speedwoofer 10S MKII is that there isn’t much I can fairly complain about. This is a modestly priced sub that has a modest size, and that brings inherent limitations. It packs a lot of performance and usability within those limitations, and it managed to exceed my expectations of what it would do. It strikes a great balance of deep bass extension and dynamic range for its size. In loudspeaker design, there is an inevitable trade-off between smaller size, dynamic range, and low-frequency extension. Increasing one of those parameters must come at the cost of at least one of the other parameters and usually both to some degree. For a subwoofer of this size to have substantial output to below 30Hz while costing less than $500 is a whole lot of good news for a lot of subwoofer shoppers. And, as we mentioned before, those with a large room and a $1k budget ought to consider a dual Speedwoofer 10S MKII setup, since that will have enough output for larger spaces as well as negating localization effects and yielding a flatter in-room response than is possible with a single subwoofer.

There are subwoofers that can dig deeper, but they are more expensive and significantly larger. There are subs that can get louder, but again, at an increase in size and cost. Even taking size out of the equation, the Speedwoofer 10S MKII should be competitive in performance with nearly every other subwoofer in its price class. What is more is that for a mere $50 extra, you can go wireless with the addition of a subwoofer signal transmitter; most other wireless subwoofer kits start at $100 and can go up to $200. This all makes the Speedwoofer 10S MKII a very high-value proposition.

In the end, you get a small-sized, nice-looking subwoofer with good extension and output for $450 (FREE Shipping), and if you want less wire clutter and more placement flexibility, add the wireless transmitter for an extra $50. It is no wonder that RSL has seen such success with the previous iterations of the Speedwoofer, and, with a product this well-rounded, I expect that success to continue with the Speedwoofer 10S MKII. Those who think that the Speedwoofer 10S MKII might be a good fit for them can try it with very little risk. Shipping is free, and there is a 30-day in-home trial. If it doesn’t work out for you, it can be returned for a $25 flat rate return fee, and RSL pays for return shipping. RSL has a very generous trial policy here, and I think they can afford to since I doubt that many buyers will be returning this subwoofer.

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

James Larson is Audioholics' primary loudspeaker and subwoofer reviewer on account of his deep knowledge of loudspeaker functioning and performance and also his overall enthusiasm toward moving the state of audio science forward.

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