Curious about subwoofer/low frequency "tightness"/musicality. What does it even mean? What do YOU look for?

[OldHvyMec]

With me it's pretty simple after years of building subs that I like. I want as light a material and motor that can do the job. The job is how low I want to go and how fast or clean I want the signal. I want fast decay rates and the amp to be able to bring the cone/motor back to center. Room modes are easy enough to fix by prepping the room as much as a person is comfortable with and then tuning the passive radiator to the lowest octave before boom.

I use putty pinching for the mass on my passive radiators. I have certain tones I play over and over untill I've added enough mass to get a boom in that room, then remove the last washer and substitute it for a non-hardening putty like @Moretite. I (then) remove putty (about the size of a pea) until the boom goes away. Then that sub is tuned for that room, that cabling and that sub amp. Over time as the passive radiator wears and the spiders/springs relax, you have to remove more putty. It usually takes about 1-2 years for a re-adjustment after the first couple of years of use. Then it becomes less and less often.

So you know, surrounds and spiders do relax over time. It's the way of all things mechanical. There should be an initial break-in of the spiders and surround and then their normal service life begins. It usually takes from 5 to 50 hours, depending on how sturdy the spider/surround is constructed.

I prefer a shorter XMax and larger cones vs smaller cones with longer XMax ((travel). It's a weight thing, and the fact that a heavy cone has to return to the center. The longer it takes, the more distortion there is. I prefer 10-12" drivers in a typical 3-400 sf room with 8-10ft lids. 3 to 6 drivers depending on how much treatment/furniture is in the room.

I use 2-3 OB double 12"servos in the record/vinyl rooms or 3-4 10-12" PR subs. Either or works fine for me as long as there is a few rumble filters I can flip on. I prefer a servo/sub system for records and a PR system for serious chest thumping bass. I also use a pair of (6-8" drivers) bass columns (with 3-8 drivers in each column) for frequencies between 60hz to 250 hz. I like the center phantom a pair of bass columns can produce. It depends on who mixed the record/tape/CD.

It's not easy to get realy good sub/bass in a room for all kinds of music. The music I listen to has a lot of congas/bongo, Latin Jazz. Unless you want ok sound it takes a bit of effort to get it to sound the way it sound at a show. BUT quite possible...

Enjoy

Regards

 

[Oddball]

Not the prettiest ART graphs, but still working on it (kind of)...

Orange is the average. Bump at 25hz is under consideration...

This is my large multi purpose room - ART graphs get much prettier than this. The room in question is on top of the image below.

 

[voodooless]

The major determining factor, as others have pointed out, is how the sub performs in the room. The flatter the frequency response, the better.

GD is more of a theoretical problem as far as I can tell. I don't know that I've ever heard it in isolation as an issue.

Because you cannot really isolate it. The room is the largest contributor to GD. That is why in many cases a properly designed reflex sub can work very well.

That is why all of these new algorithms work so well; They try to minimize room effects, flattening the response and lowering decay times.

 

[EERecordist]

Objectively, I'm a fan of the perfect piston.

In a concert hall, you will hear the percussion instruments, and low registers of the instruments like string bass, brass, lower piano, and the like. The microphones pick those up and pass them through the recording process. Depending on the instrument or microphone placement, the lows may be rolled off in the microphone. Some organs can produce very low notes, so people who focus their listening on organ music may have special needs. Microphones are not the perfect piston, but they have very low mass. The home listener cannot control the microphone, but there are very many good microphones tracking engineers compare to listening live in person.

Sometimes the instruments may be limited or compressed in the recording process for artistic purposes. In movie sound, the low frequency sound effects are going to be mixed and processed in a very accurate monitoring environment. The SMPTE standards for theatrical playback are far from down to 20Hz.

In selecting a subwoofer, I would go for rigid LF cone materials, and servo control in a sealed box. That is the best way in my opinion to have a clean chain from the microphone to the speaker.

To other ways to make a subjective experience for some programs and some listeners for which measurement is not done. For people who want to feel low frequencies in dance music or movie effects an approach is furniture shakers or SubPacs. You will find shakers in amusement parks and I believe the Las Vegas Sphere. The DBX subsonic synthesizer and other versions are a tool used in dance music to create synthetic sound. I use that at home listening to EDM.

 

[Curvature]

I want as light a material and motor that can do the job. The job is how low I want to go and how fast or clean I want the signal. I want fast decay rates and the amp to be able to bring the cone/motor back to center

The weight of the membrane does not affect woofer "speed".

The paper describes what happens when a weight is added: FR changes.

https://stereointegrity.com/wp-content/uploads/2020/06/WooferSpeed.pdf

Because you cannot really isolate it. The room is the largest contributor to GD. That is why in many cases a properly designed reflex sub can work very well.

This is the same genre of discussion as phase distortion. I can readily hear and identify frequency problems. I can't even describe a how a pure phase problem sounds (with contrived signals).

 

[voodooless]

This is the same genre of discussion as phase distortion. I can readily hear and identify frequency problems

Frequency response issues are the main contributor to group delay. There are other factors, like the longer decay of a reflex sub for instance, but they are way lower down in priority if designed correctly. And yes, what you hear is the frequency response, not so much the group delay

 

[Curvature]

Frequency response issues are the main contributor to group delay. There are other factors, like the longer decay of a reflex sub for instance, but they are way lower down in priority if designed correctly. And yes, what you hear is the frequency response, not so much the group delay

By the way, the 1 cycle and 1.5 cycle limits used in group delay measurements by a few reviewers are derived from psychoacoustics research, primarily by Jens Blauert as far as I know. So it's not that GD is nothing, it's just buried at the bottom of the list beneath every other more audible quality.

 

[Curvature]

To other ways to make a subjective experience for some programs and some listeners for which measurement is not done. For people who want to feel low frequencies in dance music or movie effects an approach is furniture shakers or SubPacs. You will find shakers in amusement parks and I believe the Las Vegas Sphere. The DBX subsonic synthesizer and other versions are a tool used in dance music to create synthetic sound. I use that at home listening to EDM.

Yes—haptics are amazing for enhancing the low end.

 

[Wayne Highwood]

What do I look for in a sub?
-Linear response. This is pretty easy these days, as there are lots of linear subs on the market.
-Low distortion. This is where the "too much is just enough" method comes into play. I want my subs loafing along, not pushing their limits, but operating low in their range where distortion is negligible. That can be achieved via a large single sub, or an array of subs (better for modal smoothing as well as keeping demands on them low). One can always reduce the gain on a more capable sub, but cannot increase the capability of a lesser sub.
-Meticulous attention to the crossover between subs and main speakers. This is critical regardless of the subs in question.

So much depends on the room's influence and how well the subs are implemented in their specific environments, which is a broader topic than the performance of specific subs, but having a grasp of all that certainly informs which subs to choose from.

I don't worry about group delay below 30hz, I just can't hear it. More egregious audible tells arise from poor calibration at the crossover.

 

[mhardy6647]

My subjective take on this discussion, as with most advanced sub discourse, is that it’s being directed specifically at me, and it’s telling me, “You idiot with your single SVS subwoofer instead of two or more, calibrated without microphone and room software and room treatments, why are you even alive, your happy audio world is nothing but delusion and darkness, your listening room with its soggy bass is a peat bog of stupidity, know FUD and tremble in fear.”

ditto!

 

[Oddball]

Lots of talk but no graphs. Agree we should not get into phase and group delay as for the most part largely irrelevant (and will not share the .mdat files by the way, or engage in such discussion), but would like to see what others have just so I can put a face to a graph...

No graph - well it's a kind of making me wonder...

 

[Timcognito]

My subjective take on this discussion, as with most advanced sub discourse, is that it’s being directed specifically at me, and it’s telling me, “You idiot with your single SVS subwoofer instead of two or more, calibrated without microphone and room software and room treatments, why are you even alive, your happy audio world is nothing but delusion and darkness, your listening room with its soggy bass is a peat bog of stupidity, know FUD and tremble in fear.”

Yeah, what were you thinking, it's rare to draw those kind of conclusions here from the all so deferential ASR crowd. I love my modest HT single sub system, plus with a myriad of movie mixes the front end input defies anything close to playback perfection.

 

[Cbdb2]

but is 10% THD even that bad when it's <50 hz?

The harmonics of the 50hz distortion can reach 300hz. And we are 20db more sensitive to 300hz than 50hz. (even the first harmonic will seem 10db louder).
Add 10db to 10% and you get 100%.

 

[Jiraya369]

With me it's pretty simple after years of building subs that I like. I want as light a material and motor that can do the job. The job is how low I want to go and how fast or clean I want the signal. I want fast decay rates and the amp to be able to bring the cone/motor back to center. Room modes are easy enough to fix by prepping the room as much as a person is comfortable with and then tuning the passive radiator to the lowest octave before boom.

I use putty pinching for the mass on my passive radiators. I have certain tones I play over and over untill I've added enough mass to get a boom in that room, then remove the last washer and substitute it for a non-hardening putty like @Moretite. I (then) remove putty (about the size of a pea) until the boom goes away. Then that sub is tuned for that room, that cabling and that sub amp. Over time as the passive radiator wears and the spiders/springs relax, you have to remove more putty. It usually takes about 1-2 years for a re-adjustment after the first couple of years of use. Then it becomes less and less often.

So you know, surrounds and spiders do relax over time. It's the way of all things mechanical. There should be an initial break-in of the spiders and surround and then their normal service life begins. It usually takes from 5 to 50 hours, depending on how sturdy the spider/surround is constructed.

I prefer a shorter XMax and larger cones vs smaller cones with longer XMax ((travel). It's a weight thing, and the fact that a heavy cone has to return to the center. The longer it takes, the more distortion there is. I prefer 10-12" drivers in a typical 3-400 sf room with 8-10ft lids. 3 to 6 drivers depending on how much treatment/furniture is in the room.

I use 2-3 OB double 12"servos in the record/vinyl rooms or 3-4 10-12" PR subs. Either or works fine for me as long as there is a few rumble filters I can flip on. I prefer a servo/sub system for records and a PR system for serious chest thumping bass. I also use a pair of (6-8" drivers) bass columns (with 3-8 drivers in each column) for frequencies between 60hz to 250 hz. I like the center phantom a pair of bass columns can produce. It depends on who mixed the record/tape/CD.

It's not easy to get realy good sub/bass in a room for all kinds of music. The music I listen to has a lot of congas/bongo, Latin Jazz. Unless you want ok sound it takes a bit of effort to get it to sound the way it sound at a show. BUT quite possible...

Enjoy

Regards

I was talking about prebuilt subs cus im not even knowledgeable enough for them and you're out here talking about BUILDING a sub

thanks for the writeup, was a nice read!

 

[Jiraya369]

Not the prettiest ART graphs, but still working on it (kind of)...

View attachment 486163

Orange is the average. Bump at 25hz is under consideration...

View attachment 486164

This is my large multi purpose room - ART graphs get much prettier than this. The room in question is on top of the image below.

View attachment 486166

wtf that looks pristine!!! omg

ok i just checked your Slovak HT system and it makes sense now. 4 friggin subs and all of em are monsters. ZAMN!!!

 

[Jiraya369]

What do I look for in a sub?
-Linear response. This is pretty easy these days, as there are lots of linear subs on the market.
-Low distortion. This is where the "too much is just enough" method comes into play. I want my subs loafing along, not pushing their limits, but operating low in their range where distortion is negligible. That can be achieved via a large single sub, or an array of subs (better for modal smoothing as well as keeping demands on them low). One can always reduce the gain on a more capable sub, but cannot increase the capability of a lesser sub.
-Meticulous attention to the crossover between subs and main speakers. This is critical regardless of the subs in question.

So much depends on the room's influence and how well the subs are implemented in their specific environments, which is a broader topic than the performance of specific subs, but having a grasp of all that certainly informs which subs to choose from.

I don't worry about group delay below 30hz, I just can't hear it. More egregious audible tells arise from poor calibration at the crossover.

thanks for the answer! What would you say is low distortion?

 

[Jiraya369]

The harmonics of the 50hz distortion can reach 300hz. And we are 20db more sensitive to 300hz than 50hz. (even the first harmonic will seem 10db louder).
Add 10db to 10% and you get 100%.

yeah but isn't THD a summation of all the distortion metrics? And isn't the 2nd order one, the one that is the least audible, almost always the worst offender? The 3rd and 4th order ones are usually less than half to a quarter of the 2nd order ones from what i've seen

 

[Sokel]

"Tight" is a very broad word (and also one of my basic vices) and I would not register it to subs, I don't think it's a measure of their quality.
"Tight" is a whole range and it's usually a nice speaker in a fairly treated room.

Very low decay at 20's and 30's does not matter much to it but go higher and it's a big factor.
Design also not matters much, to me a strong motor (with a big VC and the works of course) and lowest excursion necessary in a big cabinet is what does the trick.
I've seen long-throw stuff struggling and the result was far from tight.

I have heard far "tighter" bass (with the same extension low) from ported speakers (fairly large) than sealed ones DSP'd to their limits.
And yes, low distortion matters and matters a lot, so one chooses its poison.

 

[Wayne Highwood]

thanks for the answer! What would you say is low distortion?

Oh, lets say low single digits. That's reasonable, and pretty easy to get if the subs are operating well below their limits. Let's say a sub you're considering produces 15% THD at 20hz 120db in CEA 2010 tests, but in your use you would never exceed 100db, so for your application it's probably going to have fairly negligible distortion. Make sense? Most reputable subs have low distortion unless you throttle them, so pick a sub you won't have to throttle to hit your specific desired spls.

 

[Cbdb2]

yeah but isn't THD a summation of all the distortion metrics? And isn't the 2nd order one, the one that is the least audible, almost always the worst offender? The 3rd and 4th order ones are usually less than half to a quarter of the 2nd order ones from what i've seen

Not always, sometimes the third is higher and it takes quite a bit less third to be audible..

Woofer measurements