This is a review and detailed measurements of the Rythmik L12 subwoofer. It is kindly purchased by a member and drop shipped to me. The L12 costs US $559 in two colors (black oak and matte) and US $619 (gloss white). If you buy a white one to stick in your home theater, you and I will never get along.The sub is still on the measurement gear stand at 5 feet and I am in no mood to take it down by myself to take a picture. So you have to settle for a stock photo:Not much to look at. I did take a picture of the back though so you can see the numerous settings and configuration as tested:Note that most of the switches are three-way which makes it hard to understand at first. For example, the power button as off, auto, and always on. The way it is labeled it seems that it only has off and Audio On.A single parametric EQ is provided which is hugely better than none. Typically though you have at least two problematic modes to deal with in low frequencies so an extra one would have been great. Note that for testing I turned that off.There is an odd feature, or at least oddly labeled, is the "bass extension." Setting it to Low Music (I think) provides deepest bass. The second setting, Low-HT, puts in a subsonic filter. The third one, "high," is some kind of power saving feature???I tested with low pass filter (LPF) set to 12 dB/octave so that we can see the high frequency extension.Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS) . This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise.In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.Measurement resolution is 1.46 Hz and averaging was used to lower impact of room noise. 400 Measurements were used to determine the response of the subwoofer (low frequency devices don't need much resolution on this front).I had originally hoped to develop full suite of tests for subwoofers. I don't have the luxury of time right now to do that so what follows is brief. Open to feedback on what else should be measured.The standard Spinorama measurements are for speakers since what they radiate on-axis is different than what they radiate in other directions. At low frequencies, sound is basically omnidirectional so there is no value in that. This however is the standard way Klippel shows frequency response of the device so let's go with it:We have a broad response down to 10 Hz which was limit of my measurements. There is no port so response gently goes down.On the high side you clearly have gentle enough slope at 12 dB/octave to help out a bass deficient bookshelf speaker.Maximum output is between 60 and 90 Hz as noted.Note that this is a complete fantasy as far as what you will get in your room. Actual response in your room will have quite massive dips and peaks that need to be dealt with. Still, it is good to see what the sub is naturally capable of doing.This is a servo subwoofer which means it has a feedback loop to reduce distortion of the sub. Until we test more subs, and standardize on a playback level, we can't make comparisons. But just looking at the distortion metrics by themselves, it seems reasonably low:Best performance is above 70 Hz which is what we saw as far as peak output from the sub.The waterfall display gets crippled due to low resolution:That's it folks.Well, welcome to our first test of subwoofers.They seem to be easy to measure. And the Klippel system shines in how it produces "free field" measurements without having to hang the sub from a crane in sky or on some big field. We get perfect measurement of frequency response. There, the Rythmik L12 seems well designed and at reasonable price.------------As always, questions, comments, recommendations, etc. are welcome.Having spent all my money on the Klippel system, when it came to anchoring it down so it doesn't tip over, I used bags and jugs of heavy stuff I had in the garage. Well, I had to ask my wife to help me lift these heavy subs to the stand and she keeps tripping over them. I need to purchase heavy weight that are not a trip hazard but can't bring myself to spend my money on it. Your money however, I am happy to spend. So pleaseusing