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Rythmik L12 Subwoofer Review

amirm

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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:

1584683912992.png


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:

Rythmic L12 subwoofer Audio Review.jpg


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. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than anechoic chamber. 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.

Spinorama Audio Measurements
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:

Rythmic L12 subwoofer Spinorama CEA-2034 audio measurements.png


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:

Rythmic L12 subwoofer Distortion audio measurements.png


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:

Rythmic L12 subwoofer csd waterfall audio measurements.png


That's it folks.

Conclusions
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 please donate using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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Koeitje

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I think for subwoofers maximum SPL performance is the most interesting considering LFE channels play a lot louder than the rest of the channels?
 

RayDunzl

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General question:

What makes these?

Ambient noise?

1584690622262.png
 

Sancus

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I think for subwoofers maximum SPL performance is the most interesting considering LFE channels play a lot louder than the rest of the channels?

Agree, compression tests seem like the most important part of a sub review to me. They don't vary that substantially in moderately loaded frequency response unless they're really bad/broken.
 

beefkabob

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What SPL can it hit with some reasonable amount of distortion? Can it shake the house or just produce low sound waves at reasonable levels?
 

martijn86

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Wow thanks for kicking off subwoofers with the -to me- most interesting brand. To me, the most important thing about a subwoofer for music is the speed at which it can respond.

My suggestion for a subwoofer measurement would be to test its ability to track a square wave at E0 (20.602Hz) at a reference level. How fast can it incline and decline, and can it hold steady at the top and bottom of the square? I think that's where you'll really see a big difference in engineering quality.
 

Koeitje

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Agree, compression tests seem like the most important part of a sub review to me. They don't vary that substantially in moderately loaded frequency response unless they're really bad/broken.
Years ago I ran across a forum were some guy just dragged out subwoofers out and put them on a massive parking lot to measure spl output. Big difference there.
 

wwenze

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Wow thanks for kicking off subwoofers with the -to me- most interesting brand. To me, the most important thing about a subwoofer for music is the speed at which it can respond.

My suggestion for a subwoofer measurement would be to test its ability to track a square wave at E0 (20.602Hz) at a reference level. How fast can it incline and decline, and can it hold steady at the top and bottom of the square? I think that's where you'll really see a big difference in engineering quality.

You won't see a square nor see it hold steady because a sub shouldn't and doesn't reproduce anything above 100Hz. Or 200Hz if you count the -10dB point for this sub.
 

Blumlein 88

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I concur with others in that output levels are more important here.

And yes, aren't the low frequency rising distortion curves likely to be low frequency noise? When doing conventional measures with say REW, low frequency noise over-rides actual distortion levels below about 100 hz. The quieter you can get things at those low frequencies, which is very hard to do, the better those distortion curves look. Maybe if we could see what the Klippel picks up without the subwoofer actually connected at those frequencies it would be helpful. As most noise is pinkish, that will also make the low frequency resolution indicate higher levels at very low frequencies.
 

TabCam

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The distortion test starts from say 35 Hz. As the subwoofer has usable output from 10 Hz, is it too difficult to measure from 10 Hz on or are the distortion numbers too high??
 

RayDunzl

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You won't see a square nor see it hold steady because a sub shouldn't and doesn't reproduce anything above 100Hz.

Hmmm...

Here's a 20Hz square signal, and with a 24dB/octave low pass applied at 100Hz

1584693912446.png
 

wwenze

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Interesting. How does the FFT plot look like?

EDIT: So I made the same waveform in Audacity. No uploading images with this computer. But interesting to see a such a square wave being generated with just
20Hz @ 0dB
40Hz @ -62.5
60Hz @ -9.1
100Hz @ -16.3
140Hz @ -28.2
180Hz @ -39.1
220Hz @ -48.0
(omitting even harmonics because low amplitude)
(The original square wave has 220Hz @ -20.6 so the filter is working)

Took me a 48dB/octave filter to make the wave no longer flat. Good lesson: 24dB or gentler filters won't completely un-square a wave. At least in this case when cutoff frequency is 5 times E0.
 
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You won't see a square nor see it hold steady because a sub shouldn't and doesn't reproduce anything above 100Hz. Or 200Hz if you count the -10dB point for this sub.

My interpretation is that @martijn86 is referring to ~20 Hz.

Edit: See different uses of , & .
 

QMuse

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Years ago I ran across a forum were some guy just dragged out subwoofers out and put them on a massive parking lot to measure spl output. Big difference there.

Or he could simply google "room gain" and spared himself from the effort of proving something that has been known for at least 70 years.
 

Piotr

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Where can I buy it in Europe?

I planning to get one sub and thinking about JBL LSR310S / SB12-NSD. If I could get Rythmic L12 in $550 in price point EU it would be great.
 
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