Understanding subwoofers

[Sigberg Audio]

No sub manufacturers can integrate the subs for you. They can provide some tools but they won't affect rest of the speakers so they are really not the ultimate solution. That appears clear from the circumstances under which they offer their help?

Trying heorically not to make this sound like advertising, but I actually DO help our customers with subwoofer integration, I even help analyze rew measurements and suggest EQ - and recently made a tool to help them do this themselves. We of course also make systems where the subwoofers are integrated out of the box, which would be the best approach, but I do this even for customers who purchase subs and have speakers from other brands.

It's expensive, but the chance of getting good sound is way higher (and/or effort needed is way lower). It's hard to get people to understand the benefit of this, most don't understand until after they've made the purchase and got the assistance.

I talk to so many people who struggle with subwoofer integration, so for those in this thread who find it easy, this is not the case for everyone. Some don't have a system that is well suited for subwoofer integration, some aren't technically inclined / don't understand how it all works, and/or don't want to spend enough time to understand. Finally not everyone are clear on what benefit they are expecting from a subwoofer. So they're essentially purchasing one for the wrong reasons, not understanding that they may need other speakers as well to get the sound they are looking for. Or perhaps the issue is the room, so then we have to open the can of worms that is acoustical treatment, speaker/listening position placement, etc etc.

 

[Sokel]

• Subs are under the Left and Right speakers so no need for time alignment

???
Unless the "subs" are passive and driven by the same DSP/analog/whatever network, they will present electronic delay of their own, co-location is not enough to address that, it must be carefully measured (NOT an easy task) and applied.

 

[EJ3]

Did I say anything about your specific speakers? No, I didn’t.

Also, if the speaker has ports, they need to be plugged since all they will do is leak resonant noises from the inside of the cabinets. A small consideration, but very easy to do.

So: the speakers have no effect on where I would cross over? (which, by the way is 55 Hz HP & 70 Hz LP using analog xo).

Not 200Hz, but Dirac ART can work up to 150Hz.

All analog at the moment, nothing computerized in my system (yet).
The subs are run in stereo and each (of the 2) has 1800 (class G) watts available to it.

I may (and probably do) do things quite differently than many.
But I do what works for my system in my circumstances.

I'm sorry @SHB but you are absolutely wrong in regards to my 2.2 setup.
I've only been doing this stuff for just over 40 years and I'm pretty sure that I have gotten the hang of it (for what I need out of it, anyway) by now (at least until I add digital xo's to it).

 

[Sigberg Audio]

I actually can't think of any that fit that criteria.



Floor space, extra cables, ugliness, reliance on dedicated amplification (sometimes).

Infinity Reference Standard (IRS)
Marten Coltrane Supreme Extreme
MBL 101 X-Treme
YG Acoustics Sonja XV
Gryphon Kodo

...

 

[EJ3]

Trying heorically not to make this sound like advertising, but I actually DO help our customers with subwoofer integration, I even help analyze rew measurements and suggest EQ - and recently made a tool to help them do this themselves. We of course also make systems where the subwoofers are integrated out of the box, which would be the best approach, but I do this even for customers who purchase subs and have speakers from other brands.

It's expensive, but the chance of getting good sound is way higher (and/or effort needed is way lower). It's hard to get people to understand the benefit of this, most don't understand until after they've made the purchase and got the assistance.

I talk to so many people who struggle with subwoofer integration, so for those in this thread who find it easy, this is not the case for everyone. Some don't have a system that is well suited for subwoofer integration, some aren't technically inclined / don't understand how it all works, and/or don't want to spend enough time to understand. Finally not everyone are clear on what benefit they are expecting from a subwoofer. So they're essentially purchasing one for the wrong reasons, not understanding that they may need other speakers as well to get the sound they are looking for. Or perhaps the issue is the room, so then we have to open the can of worms that is acoustical treatment, speaker/listening position placement, etc etc.

Very nice tool!

 

[Sigberg Audio]

Xmax is only 15mm so trying to get useful output at 20Hz will not be possible with this driver.

An 18" driver with 15mm xmax will not get useful output at 20hz?

Where are you getting your numbers from?

Where are you getting yours from?

 

[thcdru2k]

If I had your components Emotiva XMC-1, KEF LS50, and four stacked Rythmik L12 subs, I would insert a miniDSP Flex HTx between the processor and amps. This keeps your layout but fixes the real weak point by giving you proper crossover control (I would test 150 to 170 Hz), precise delay to actually time align, and phase verification so they sum cleanly. Even co located, alignment is not automatic and either subs or mains will need delay, and a UMIK-2 is preferred for the timing precision needed.

Edit: after reading more of the thread I would probably check 100-130hz as well. Balance between minimizing distortion and directivity

 

[DY2]

To me it seems there are a lot of inconsistencies around subs and subs integration that aren't talked about very scientifically even on ASR:

1. Why is that for electronics we want 100+ dB SINAD and we want 50+ SINAD for speakers above 100 Hz but somehow it is "OK" to have distortion of 13% (which is more or less that CEA-2010 standard) or even much higher like 30% (common for many famous brand subs) below 100 Hz i.e. SINAD of <10? I think distortion is more audible down low due to Fletcher-Munson i.e. between 20 Hz and 40 Hz we are 20 dB more sensitive so for many subs when they try to play 20 Hz they actually produce more audible distortion products at 40 Hz than at the 20 Hz fundamental. I almost never see distortion mentioned when discussing subs.

Hello everyone! This is my first post here, and I would like to start by expressing my appreciation for the incredible work and detailed analyses shared on this forum. Your technical insights have been a great source of inspiration for my own system calibration.

I am following this discussion regarding low-frequency distortion with interest. I noticed the mention of 13% to 30% THD figures for subwoofers below 100 Hz, and I was curious to learn more about the context or sources of these specific values.

I am asking because, in my own measurements (using a Marantz AV7704 and Klipsch R-121SW subwoofers, manually aligned), I am seeing significantly lower figures at reference levels. For example, as shown in the attached THD graph, at 21.34 Hz my 2nd harmonic is at 0.088% and the 3rd at 0.067%.

I would love to understand if those higher percentages are common for specific stress tests or perhaps related to different measurement standards, as they contrast quite a bit with what I am finding in my room.

Looking forward to your insights and glad to be part of the community!

 

[Sokel]

Hello everyone! This is my first post here, and I would like to start by expressing my appreciation for the incredible work and detailed analyses shared on this forum. Your technical insights have been a great source of inspiration for my own system calibration.

I am following this discussion regarding low-frequency distortion with interest. I noticed the mention of 13% to 30% THD figures for subwoofers below 100 Hz, and I was curious to learn more about the context or sources of these specific values.

I am asking because, in my own measurements (using a Marantz AV7704 and Klipsch R-121SW subwoofers, manually aligned), I am seeing significantly lower figures at reference levels. For example, as shown in the attached THD graph, at 21.34 Hz my 2nd harmonic is at 0.088% and the 3rd at 0.067%.

I would love to understand if those higher percentages are common for specific stress tests or perhaps related to different measurement standards, as they contrast quite a bit with what I am finding in my room.

Looking forward to your insights and glad to be part of the community!

View attachment 529551

Better change your scale to dB units.
To judge about distortion in general one has to take absolute levels into account as the distortion is relative to them, so REW must be electrically calibrated as well as acoustically.

 

[Sigberg Audio]

Hello everyone! This is my first post here, and I would like to start by expressing my appreciation for the incredible work and detailed analyses shared on this forum. Your technical insights have been a great source of inspiration for my own system calibration.

I am following this discussion regarding low-frequency distortion with interest. I noticed the mention of 13% to 30% THD figures for subwoofers below 100 Hz, and I was curious to learn more about the context or sources of these specific values.

I am asking because, in my own measurements (using a Marantz AV7704 and Klipsch R-121SW subwoofers, manually aligned), I am seeing significantly lower figures at reference levels. For example, as shown in the attached THD graph, at 21.34 Hz my 2nd harmonic is at 0.088% and the 3rd at 0.067%.

I would love to understand if those higher percentages are common for specific stress tests or perhaps related to different measurement standards, as they contrast quite a bit with what I am finding in my room.

Looking forward to your insights and glad to be part of the community!

View attachment 529551

The CEA2010 / distortion measurements of subwofoers are typically measured outside in a free field.

In a normal room you will get lots of room gain (reinforcement of bass from the fact that you are inside a room), which makes the job of a subwoofer much easier. So the measurements you see would look completely different if you did the measurement with your subwoofer outside in a parking lot.

Here is a measurement of your subwoofer and how loud it can play in such a condition. In the rows where it says it's limited, it's probably at 20-30% THD. Measurement distance is 2 meters.

 

[Keith_W]

Trying heorically not to make this sound like advertising, but I actually DO help our customers with subwoofer integration, I even help analyze rew measurements and suggest EQ - and recently made a tool to help them do this themselves.

You know what you need to do? Take a leaf out of David Wilson's playbook. Wander around the listening room. Clap your hands a few times. Move the speakers a few inches. Then walk out and leave everyone in awe of your God-like status

 

[Sigberg Audio]

You know what you need to do? Take a leaf out of David Wilson's playbook. Wander around the listening room. Clap your hands a few times. Move the speakers a few inches. Then walk out and leave everyone in awe of your God-like status

Haha! Maybe I will try that next time.

 

[Redacted]

Integration with my mains took fully three days, but it worked out well.

In the end, if you have large full range speakers, someone else did the work to integrate low bass using filters (and cabinet & driver knowledge), and you may not want to bother doing anything yourself. If however, you have small main speakers like me, they really won't have properly extended bass, and I like low bass. I don't have room for big floor standers though, so a pair of subs helped a lot. I plugged the ports of my main speakers (per the manual and foam plugs that came with them) to essentially make them infinite baffles, and they sound far better for it (with added subs!).

N.B. bass guitar bottom E is ~43Hz, and bottom A on a piano is ~27.5Hz.

 

[Redacted]

You know what you need to do? Take a leaf out of David Wilson's playbook. Wander around the listening room. Clap your hands a few times. Move the speakers a few inches. Then walk out and leave everyone in awe of your God-like status

My servants are attentive enough for me to not have to clap.

 

[DY2]

Better change your scale to dB units.
To judge about distortion in general one has to take absolute levels into account as the distortion is relative to them, so REW must be electrically calibrated as well as acoustically.

I completely agree, Sokel. Absolute levels and a log scale are much more professional for this type of analysis.

I don't have the PC with the REW project open right now to export a new dB-scaled graph, but I can provide the key data points from that specific measurement (taken with a calibrated Umik-2):
2nd Harmonic: -70.7 dB
3rd Harmonic: -76.1 dB:
Context:
This was measured at a reference level where the fundamental is clearly dominant. The low distortion is a direct result of the 6-sub array providing massive headroom, keeping the excursion of each individual Klipsch driver at a minimum.
I will make sure to use the dB scale for my future posts to keep everything consistent. My main point was that even without the dbx units (which I'm adding now), the manual alignment of a multi-sub system can yield results far superior to the 13-30% figures mentioned earlier.

 

[DY2]

The CEA2010 / distortion measurements of subwofoers are typically measured outside in a free field.

In a normal room you will get lots of room gain (reinforcement of bass from the fact that you are inside a room), which makes the job of a subwoofer much easier. So the measurements you see would look completely different if you did the measurement with your subwoofer outside in a parking lot.

Here is a measurement of your subwoofer and how loud it can play in such a condition. In the rows where it says it's limited, it's probably at 20-30% THD. Measurement distance is 2 meters.

View attachment 529552

Thank you, sigbergaudio, for the detailed explanation and for sharing the CEA-2010 data for the R-121SW. That context is very helpful.

You make an excellent point regarding room gain versus free-field measurements. I am fully aware that my indoor measurements benefit significantly from the room's reinforcement, which eases the load on the drivers compared to a parking lot stress test.

However, the main reason my figures differ so much from the single-unit 'Harmonic Limit' rows in that table is the multi-sub array. By using 6 subwoofers instead of one, the displacement (Xmax) required from each individual driver to reach my reference SPL is divided by six.

Essentially, while a single unit might be pushed into 20-30% THD to hit a certain target at 20 Hz, my array can provide the same output while each driver remains well within its linear operating range. This massive increase in system headroom—combined with the room gain you mentioned—is what allows me to maintain those -70 dB distortion levels in my actual listening environment.

I appreciate the insights, as it helps clarify that 'normal' distortion is often a function of pushing single units to their mechanical limits, which is exactly what I aimed to avoid with this setup.

 

[DY2]

Better change your scale to dB units.
To judge about distortion in general one has to take absolute levels into account as the distortion is relative to them, so REW must be electrically calibrated as well as acoustically.

As requested, here is the distortion graph for the 21 Hz measurement, now plotted with the Y-axis in dB relative to the fundamental (dBr) for better clarity.

Key technical details from the graph:

• The fundamental frequency at 21.04 Hz is normalized to 0 dBr as the reference level.
• The 2nd Harmonic (red line) sits at -61.1 dBr, which is exceptionally low for this frequency.
• The 3rd Harmonic (orange line) was measured at -63.7 dBr, showing excellent cone control.
  
• The 4th Harmonic (yellow line) drops significantly to -77.2 dBr.
• Total Harmonic Distortion (the black THD line) is calculated at -58.3 dBr, which is approximately 0.12%.
• The measurement remains clean with a noise floor around -56.2 dBr.

This confirms the previous data while providing the higher resolution requested by switching from percentages to decibels. The system remains extremely linear even at the very bottom of the frequency range.

 

[Devnull]

Infinity Reference Standard (IRS)
Marten Coltrane Supreme Extreme
MBL 101 X-Treme
YG Acoustics Sonja XV
Gryphon Kodo

...

Don't forget Gimm LS1 and not exactly small but JBL did design a subwoofer to specifically work with the M2

 

[janbth]

That’s why a simple 2.0 can make a lot of sense. With good placement and some boundary gain, you get solid in room bass with everything coming from one place, no crossover, no extra variables. It just sounds natural.
Subs are great for movies and full range impact, no question. But for music, especially in smaller or secondary rooms, the simplicity matters. Less setup, less tweaking, more time actually enjoying it.
I’m not biased either way. I run dual subs in my main system, a single sub in another, and a 2.0 setup elsewhere. Each has its place.
True integration takes effort, and sometimes a clean 2.0 gets you closer to the goal with less work.

These are the words of someone who is fortunate to not have problematic room modes in his/her setup.

 

[levimax]

Thank you, sigbergaudio, for the detailed explanation and for sharing the CEA-2010 data for the R-121SW. That context is very helpful.

You make an excellent point regarding room gain versus free-field measurements. I am fully aware that my indoor measurements benefit significantly from the room's reinforcement, which eases the load on the drivers compared to a parking lot stress test.

However, the main reason my figures differ so much from the single-unit 'Harmonic Limit' rows in that table is the multi-sub array. By using 6 subwoofers instead of one, the displacement (Xmax) required from each individual driver to reach my reference SPL is divided by six.

Essentially, while a single unit might be pushed into 20-30% THD to hit a certain target at 20 Hz, my array can provide the same output while each driver remains well within its linear operating range. This massive increase in system headroom—combined with the room gain you mentioned—is what allows me to maintain those -70 dB distortion levels in my actual listening environment.

I appreciate the insights, as it helps clarify that 'normal' distortion is often a function of pushing single units to their mechanical limits, which is exactly what I aimed to avoid with this setup.

I am glad you got things clarified about distortion, if you want some more contex I have learned a lot about both subs and the CEA-2010 tests by studying this post showing the details of every test for 10 popular subs. There is a lot more to sub performance than just over simplified marketing specs. https://www.audiosciencereview.com/forum/index.php?threads/i-measured-10-subwoofers.49042/

One question about your measurements, do you know the SPL level at the listening position for the sweep you took?