Rythmik L12 Subwoofer Review

[pozz]

I understand the log part. What I dont understand is why your taking the log of the distortion value. The other thing I want to draw attention too is the Fletcher Munson curves where human hearing sensitivity to frequency is fairly insensitive to bass. Reading from different sources, I was under the impression that bass frequencies were able to mask noise much more effectively than mids and high frequencies. Maybe this is the perception thing that was mentioned earlier.

I kind of feel like we're going in circles. The conversion of a nominal percentage-based distortion figure to dB of attenuation vs. the signal is straightforward: http://www.sengpielaudio.com/calculator-thd.htm

Take Amir's dashboard: https://www.audiosciencereview.com/...icon-dd8-review-multichannel-amplifier.19576/

0.005090% THD+N is equivalent to 85.866dB SINAD, or is another way of saying that the sum of all distortion and noise for a 22kHz bandwidth is 85.866dB below the signal.

Since bass is at the extreme end of human hearing sensitivity, bass can have up to 10% distortion and you will not be able to distinguish it from the actual bass note.

"Bass can have up to 10% distortion" is equivalent to "distortion can be up to 20dB below the signal (or bass note)".

My first reply to you was to contextualize this threshold value. I quoted a study showing perceptual thresholds express in both dB and percent for varying SPL and specific harmonic content. The way to read the table from that study is as follows:

• For a 20Hz signal ("bass note") at 80dB SPL:
  • 2nd harmonic distortion (i.e., a spur at 40Hz in addition to the 20Hz signal, also known as H2) can be up to -24dB or 6% of the signal until you can hear it.
  • H3 (60Hz) can be up to -36dB or 1.6% of the signal until you can hear it.
  • H4 (80Hz) can be up to -43dB or 0.7%.
  • H5 (100Hz) can be up to -47dB or 0.44%.

These thresholds shift as SPL changes. You can definitely hit around 10% or -20dB for some combinations of distortion spectrum, level and frequency.

My point was that you cannot say stuff like "up to 10% distortion". It's very misleading and not useful even as a rule of thumb.

In general, it's important to get away from a kind of flat threshold thinking about sound. There are other studies that contradict the thresholds by Fielder et al that I cited. It's definitely an unresolved question, but absolute thresholds aren't as important given how effective masking is when we're listening to music.

The best we have available, in terms of a comparative standard, is the CEA 2010. However, some context is necessary. It states the following for allowable distortion thresholds vs. the fundamental (i.e., the signal or bass note):

• H2: -10dB (31.6%)
• H3: -15dB (17.8%)
• H4–5: -20dB (10%)
• H6–8: -30dB (3.2%)
• H9≤: -40dB (1%)

This would seem to contradict the Fielder study until you take into account the length of the signal. CEA 2010 calls for burst testing. Specifically, a 6.5 cycle tone burst. At 20Hz, that's 325ms (the calculation is based on how long it takes a 20Hz signal to go through 6.5 of its 20 cycles). Although music has percussive and impulsive components, there are also a lot of steady signals that are much longer, and the perceptual thresholds for detecting distortion are lower for longer signals, which Fielder used, than for bursts. In that sense the CEA 2010 thresholds define a very rigorous test.

 

[RichB]

... What I think is more likely to be the true description, based on a great many first-hand experiences, is that bass harmonic distortion frequently leads to the audibility of the higher-frequency, high-order distortion components and not to any real or synthesized perception of the bass note itself. I think it is safe to say that everyone has experienced this, which is why I'm not on board with the idea that we are less likely to hear harmonic distortion associated with a bass note as compared to harmonic distortion associated with a midrange note. I suppose this comes from experiments that have been done, but I suspect that the outcome of those experiments was influenced majorly by the assumptions that had been made when setting up the experiment.

I agree with this statement but add that resonances, port noise, and even mechanical noise can be localized.

The LFE channel can contain frequencies that can be localized.
For these reasons, it is still a good idea to pursue products with low THD and resonances and always consider more than one subwoofer to combat room modes.

- Rich

 

[Chromatischism]

You confused me with that first sentence, but I went ahead and read the rest of it anyway. You said, "There are no peaks." I can only suppose that you thought that I was saying that response peaks remain even with the application of servo control, and that I was speaking even more particularly of the actual response of the specific subwoofers that Rythmik makes, which use servo control. You must have thought that this is what I was saying, but it is bizarre, because there wasn't any reason at all for you to have thought this. None. I am thus motivated to tell you that your communication skills are awful.

You also did a poor job of making your meaning clear. You said, "There are no peaks, in fact it's surprising how linear the response of the subs are without any DSP." I can only assume that you are referring to the actual response of one or more specific models made by Rythmik, but you didn't make this clear, and it was confusing to me because the statement I had made was not specially about that. I had only said something about response peaks associated, inherently, with high Q.

As for the stuff you copied from Rythmik's website, it would require considerable effort for anyone to make an informed assessment of the veracity of the claims. What I see on the surface is some stuff that vaguely alludes to the possibility of true, audible benefit. But the audio world is plagued by this kind of thing, where someone touting some thing expounds a list of effects that seem potentially beneficial, i.e., they are plausible, but this is done without providing any real evidence that the claimed effect translates into audible reality. It isn't fundamentally any different from what cable peddlers do. Most everyone in the audio industry does this to some extent, but the extent to which it is done varies significantly.

Finally, I will point out that your opening words were, "That is mostly correct ...", which of course implies that it is partly incorrect, and to justify this insincere insinuation that what I wrote was partly incorrect, you deferred to a manufacturer's marketing spiel. The manufacturer's marketing spiel? Seriously? You're going to use a manufacturer's marketing spiel as the basis for asserting that something that someone else wrote isn't correct? And you're going to do this when your interpretation of what that other person wrote is obviously not even a sincere interpretation of what the other person wrote? If your goal was to discourage me from participating any further in this thread, you may have achieved that goal.

Wow. I think you are taking this WAY too seriously and personally when it was never meant that way. No part of my post was directed AT you in any negative way whatsoever. I simply keyed off of your post and added more detail for the thread readers. I'm not perfect, but if this is how you conduct yourself normally, I wouldn't be throwing shade on others' communication skills.

 

[preload]

Interestingly, the Rythmik F12 isn't particularly special among subs of similar size either. The SB-3000 Pro looks to have significantly higher output (+5.6dB at 50Hz), it's smaller, and it comes with a DSP x-over/PEQ.

 

[Chromatischism]

Sure, but the SB-3000 uses a 13" driver with an 800w amp. Also I notice it doesn't extend as low or have as flat of a response, with that peaking at 50 Hz.

 

[preload]

Sure, but the SB-3000 uses a 13" driver with an 800w amp. Also I notice it doesn't extend as low or have as flat of a response, with that peaking at 50 Hz.

Correct, and it's amazing technology that they're able to optimize a 13" driver into such a small enclosure. Also, what do you mean when you say that the SB-3000 "doesn't have as flat of a response, with that peaking at 50Hz?" What data or review are you basing that on?

 

[Chromatischism]

Correct, and it's amazing technology that they're able to optimize a 13" driver into such a small enclosure. Also, what do you mean when you say that the SB-3000 "doesn't have as flat of a response, with that peaking at 50Hz?" What data or review are you basing that on?

Your chart.

 

[preload]

Your chart.

How did you determine the frequency response of the SB3000 using CEA-2010 data???

 

[Chromatischism]

How did you determine the frequency response of the SB3000 using CEA-2010 data???

Is this a serious question? Your numbers show the sub has much more output in the midbass relative to 20 Hz, alluding to design decisions to not prioritize a more flat response like Rythmik and JTR. Not saying right or wrong. It's a different design. But not really comparable.

 

[preload]

Is this a serious question? Your numbers show the sub has much more output in the midbass relative to 20 Hz, alluding to design decisions to not prioritize a more flat response like Rythmik and JTR. Not saying right or wrong. It's a different design. But not really comparable.

Can you elaborate further? I want to make sure I understand completely. You’re saying the frequency response curve of the SB3000 has a peak at 50Hz based on the CEA-2020 figures I posted?

 

[Chromatischism]

I think the correct way to state it would be that at max output, there is more distortion-limited output at 50 Hz relative to 20 Hz compared to the Rythmik which is flatter. But yes, that is a frequency response measurement.

I don't know what the response looks like at lower levels.

PSA seems to have a similar philosophy in that they don't emphasize a monster low end like Rythmik and JTR and prefer to design subs that are stronger in the midbass. Again not right or wrong, just different designs.

 

[preload]

I think the correct way to state it would be that at max output, there is more distortion-limited output at 50 Hz relative to 20 Hz compared to the Rythmik which is flatter. But yes, that is frequency response.

I’m still not following, mostly because what you just described is NOT a frequency response.

Also, why would it be a disadvantage for the max CEA-2020 output at 50Hz to be greater than at 20Hz? How much greater can the 50Hz value be before you would say there’s a problem?

 

[Chromatischism]

I’m still not following, mostly because what you described is NOT a frequency response.

It is the frequency response at max output. I thought I worded clearly enough. I realize most won't run their subs at those levels but if you were to do so, that is what you will get.

It shows that at max output, the curve for the SVS will be tilted more than the Rythmik. I don't know a simpler way of putting it.

You can see this in the measurements for the SB-13 Ultra. While not the same sub, it's very similar. Compare to the sealed Rythmik models, especially at max extension to see they have different design goals. You'll see the drop off on the low end of the SVS comes much sooner. And not only at max output.

https://data-bass.com/#/systems/5bd0c4ea20120c00040a9bed?_k=am0qaq

 

[preload]

It is the frequency response at max output. I thought I worded clearly enough. I realize most won't run their subs at those levels but if you were to do so, that is what you will get.

That's what I thought you meant, but wanted to be sure. What you have stated is not correct. The frequency response at max output does not follow CEA-2010 values, unless they are all amplifier (and not THD) limited. The SB3000's CEA-2010 values were not amplifier-limited, which means SB3000's max output curve exceeds and does not necessarily follow the CEA-2010 numbers. The way to understand frequency response at max output is to run a series of sine sweeps at increasing levels - i.e. a compression test. You may want to consider the need to understand more than just what you read in the manufacturer's marketing materials (I think MrPeabody was the first to suggest this to you.)

 

[3dbinCanada]

Interestingly, the Rythmik F12 isn't particularly special among subs of similar size either. The SB-3000 Pro looks to have significantly higher output (+5.6dB at 50Hz), it's smaller, and it comes with a DSP x-over/PEQ.

View attachment 107789

And MSRP for the SVS compared to the F12? Lets compare a $1000 sub to the F12 while your at it.

 

[MrPeabody]

Wow. I think you are taking this WAY too seriously and personally when it was never meant that way. No part of my post was directed AT you in any negative way whatsoever. I simply keyed off of your post and added more detail for the thread readers. I'm not perfect, but if this is how you conduct yourself normally, I wouldn't be throwing shade on others' communication skills.

I'm not taking it too personally or too seriously. If I gave you the sense that I was particularly offended, then for that I need to apologize. I was annoyed, not offended, and there is a difference. I wanted to explain, in what I intended to be a matter-of-fact way, why I found your response confusing. Since you apparently didn't get it, I will try to explain it again, succinctly. You said in essence that I was incorrect in saying that the high Q implied a peak in the frequency response. Naturally I wanted to understand why you would have said that high Q does not imply a peak in the frequency response, and why you would have said that I was incorrect on that trivial point. I said to myself, "What's he saying?". So I read what you wrote, and it was not at all clear to me what you were trying to say, and why it would mean that high Q does not imply a peak in the frequency response. My best guess, and this is only a guess, is that you meant to say that with the application of servo control, the response peak that would otherwise be a consequence of high Q will be suppressed. If it happens that this is what you meant to say, then I will say to you that you never really came within a mile or two of actually saying this. I'm only guessing that this was what you meant to say, because it's the only plausible interpretation that I've been able to come up with. If you don't think that this reflects on your communication skills, after my having taken the time to explain this to you, then I just don't know what else to say.

 

[RichB]

I don't see how these discussions have much to do with the Rytmik L12.

- Rich

 

[preload]

And MSRP for the SVS compared to the F12? Lets compare a $1000 sub to the F12 while your at it.

This particular analysis was strictly based on enclosure size and cea-2010 performance. But if you want you can look up the price of an SVS SB3000, I think you'll be pleasantly surprised.

 

[Chromatischism]

That's what I thought you meant, but wanted to be sure. What you have stated is not correct. The frequency response at max output does not follow CEA-2010 values, unless they are all amplifier (and not THD) limited. The SB3000's CEA-2010 values were not amplifier-limited, which means SB3000's max output curve exceeds and does not necessarily follow the CEA-2010 numbers. The way to understand frequency response at max output is to run a series of sine sweeps at increasing levels - i.e. a compression test.

It's a fair point, but let me ask you this. Did my statement that the frequency response will show more of a rise toward 50 Hz (and higher) on the SVS bear out when looking at the measurements? If the SB-13 Ultra is an indication, and I see no reason to believe that it isn't, then yes, I am correct to say that the CTA-2010 measurements do give us an indication of what the frequency response will look like; it does not radically depart from the CTA-2010 from what I have seen. That is what I am trying to say. It is correct to say that the Rythmik has a flatter response. That is by design. Yes, a compression test is what I had in mind when writing that post, so I apologise for not being clear, but the trend is the same.

 

[Sancus]

Interestingly, the Rythmik F12 isn't particularly special among subs of similar size either. The SB-3000 Pro looks to have significantly higher output (+5.6dB at 50Hz), it's smaller, and it comes with a DSP x-over/PEQ.

That is indeed pretty close, makes me wonder about the SB-4000, can't find CEA2010 for it anywhere though.

I'll note, for a sealed sub, the SB-3000 does seem to have pretty high low-freq group delay, which is common for SVS and not something I've ever seen in measurements of a Rythmik. Audible? Dunno, I'd lean towards maybe not, but still. JL also has excellent group delay. E: PSA too.