Understanding subwoofers

[WillBrink]

It seems that most audio fans and reviewers don’t really understand the advantages subwoofers bring to your listening experience other than more low bass.

• If you use stereo subs and set your crossover to around 200Hz, you can increase the dynamic range of your system by 6dB or more. If you’re using small two-way speakers, the increase will be in the more area. This is not an insubstantial improvement.

I was aware of the increase in dynamics but not aware it requires X over as high as 200Hz to achieve it. X over that high, would it not limit positioning options for the subs? It's moot for me as I'm using subs as speaker stands, but still curious.

 

[john61ct]

these are contradictory statements as a 4th order bandpass means a degraded transient response (but still a response described by the given frequency response so...)

Yes, hence the "but" in between the two choices

 

[john61ct]

I was aware of the increase in dynamics but not aware it requires X over as high as 200Hz to achieve it. X over that high, would it not limit positioning options for the subs? It's moot for me as I'm using subs as speaker stands, but still curious.

Yes. I would stick to 80Hz (likely lower) on units I want to place freely to wrangle room effects.

Any higher, co-locate and tune timing closely

 

[3ll3d00d]

Yes, hence the "but" in between the two choices

ok but then the fact it has a sealed rear chamber seems irrelevant, you could just add a port and call it done

 

[john61ct]

ok but then the fact it has a sealed rear chamber seems irrelevant, you could just add a port and call it done

My understanding is there is no room for a port given the 12x12" face limitation.

Just to clarify, I am leaning toward a purely sealed design at the moment, given the priority is clean transients over SPL efficiency

 

[levimax]

My understanding is there is no room for a port given the 12x12" face limitation.

Just to clarify, I am leaning toward a purely sealed design at the moment, given the priority is clean transients over SPL efficiency

Any chance you could do Infinite Baffle built into a wall or ceiling? You would not have to give up any performance and would still have a small face.

 

[EJ3]

Which impact are we talking about?
The chest punch for example is way higher than 80Hz reaching 250Hz.

Some nice test here:

Bass: the Physical Sensation of Sound

Ever wonder why you can feel bass? We take a look behind the science of bass waves and the tactile sensations that they cause. Our bass experiments were quite revealing but don't try them at home.

www.audioholics.com

And some of the text:

View attachment 530993

Also the internal dimensions of the chest cavity: if you are 5' 4" and 88 lbs. but well toned and sinewy (perhaps a competitive sprinter), your body cavities respond somewhat differently to different frequencies than someone that is 5'8' and 185 lbs. but muscular (perhaps a shot put competitor). Perhaps one feels the "chest punch at 60 Hz & the other doesn't feel it until the frequency is at 80 Hz.
And someone else perhaps does not feel it below 100 Hz.
Exactly what is said in this text "a broad range of low frequencies".
But, having built sound systems for night clubs (tri-amped and with around 10,000 watts RMS total power [18" speakers on the low end]):
I have a good bit of EMPIRICAL knowledge on this subject.
If you are not getting down to at least 60 Hz with a good bit of DB, some people will be missing out on the "slam".
Did I measure the bodies of those that let me know that they were "just not feeling it"? No.
So, not in anyway is this EMPIRICAL anecdotal evidence scientific.

 

[levimax]

Also the internal dimensions of the chest cavity: if you are 5' 4" and 88 lbs. but well toned and sinewy (perhaps a competitive sprinter), your body cavities respond somewhat differently to different frequencies than someone that is 5'8' and 185 lbs. but muscular (perhaps a shot put competitor). Perhaps one feels the "chest punch at 60 Hz & the other doesn't feel it until the frequency is at 80 Hz.
And someone else perhaps does not feel it below 100 Hz.
Exactly what is said in this text "a broad range of low frequencies".
But, having built sound systems for night clubs (tri-amped and with around 10,000 watts RMS total power [18" speakers on the low end]):
I have a good bit of EMPIRICAL knowledge on this subject.
If you are not getting down to at least 60 Hz with a good bit of DB, some people will be missing out on the "slam".
Did I measure the bodies of those that let me know that they were "just not feeling it"? No.
So, not in anyway is this EMPIRICAL anecdotal evidence scientific.

I read somewhere that it was about the resonant frequency of the chest cavity of the person which varies based on the size and shape of the person. No formula was given that I recall. I have seen numbers between 40 Hz and 200 Hz so to be safe I try for flat group delay from 200 Hz down to 20 Hz with plenty of SPL.

 

[john61ct]

Any chance you could do Infinite Baffle built into a wall or ceiling?

No, nearly all components need to be mobile

in fact often the "room" is the inside of a truck, a boat or the great outdoors.

12" is nearly "too big" smaller would be better.

 

[levimax]

Also the internal dimensions of the chest cavity: if you are 5' 4" and 88 lbs. but well toned and sinewy (perhaps a competitive sprinter), your body cavities respond somewhat differently to different frequencies than someone that is 5'8' and 185 lbs. but muscular (perhaps a shot put competitor). Perhaps one feels the "chest punch at 60 Hz & the other doesn't feel it until the frequency is at 80 Hz.
And someone else perhaps does not feel it below 100 Hz.
Exactly what is said in this text "a broad range of low frequencies".
But, having built sound systems for night clubs (tri-amped and with around 10,000 watts RMS total power [18" speakers on the low end]):
I have a good bit of EMPIRICAL knowledge on this subject.
If you are not getting down to at least 60 Hz with a good bit of DB, some people will be missing out on the "slam".
Did I measure the bodies of those that let me know that they were "just not feeling it"? No.
So, not in anyway is this EMPIRICAL anecdotal evidence scientific.

I asked my AI friend about slam and chest resonance and people size and it came back with some interesting results. I would not take this as the last word but it does appear that different size people are going to perceive slam differently which backs up your observations.

 

[EJ3]

I asked my AI friend about slam and chest resonance and people size and it came back with some interesting results. I would not take this as the last word but it does appear that different size people are going to perceive slam differently which backs up your observations.

View attachment 531030

I come in on the last one 5' 6 & 1/2" (down an inch and 1/2 due to cervical vertebrae surgery), 237 lbs. My wife is 96 lb.'s & 5'1" and she doesn't feel it until around 90 Hz.
So this chart seems to corelate reasonably well with my EMPIRICAL anecdotal evidence.
The systems that I built were for live bands on the stage (7 days a week, a different band every 2 weeks) AND in conjunction with the same gear (at a lesser DB level [and less of it]) around the dance floor (for music video's between band sets) that people would dance to. And everyone (up to 880 people capacity) should be feeling some level of slam, whether dancing between bands sets (at a slightly lower overall DB or during bands sets (at a slightly higher DB level) or just being at a table in the night club (with the ability to converse with others at the tables with a raised voice but not yelling [at least between band sets}).
A challenging balancing act. (with DB limits at the tables). Not an issue when more than 2/3 full but could be an issue until the crowd built up.

 

[audiofooled]

I see what you guys are talking about. Just about any system capable of high SPL will have some kind of an "impact" sometimes, at some frequency and it would quite possibly feel different depending on body size and physiology.

But what I'm talking about is actually a vector quantity that will hit at any fundamental frequency of the transient, be it recorded or produced. It really does not matter if it's a kick drum of any tuning, taiko drum, percussion, or entirely produced electronic music and it will not care about your body size.

Yes it's dP/dT, but the wavefront actually has a direction and area from where you can literally move away and be safe. And it would feel different at any frequency, it would feel different with distance, it would even feel different depending on how much air you have in your lungs. Different organs would also have different acoustic impedance.

Big part of it is related to air itself being nonlinear at high SPL. Something not easily measured or even predicted by the means of Linear Acoustics.

 

[john61ct]

Yes it's dP/dT, but the wavefront actually has a direction and area from where you can literally move away and be safe.

As in a weapon's shock wave?

 

[audiofooled]

As in a weapon's shock wave?

While there's research about weak shock waves and visuals using Shlieren optics, they are usually limited to small wavelengths, when it comes to transducers its really in the realm of ultrasound (where the amplitudes are high in comparison to the wavelength). What exactly is going on in case of wide bandwidth complex signals in a complex sound field is a matter of research and levels and conditions would need to be specified.

But the idea is that with high enough rate of change in pressure there would be a form of distortion where the pressure peaks are travelling faster than the troughs slanting the waveform to the left, taking a form resembling a sawtooth shape, but when observed as a function of distance, the high pressure wave would have also travelled a greater distance, slanting the wave to the opposite direction. In both cases the zero crossing would be at atmospheric pressure. In general this makes recording of the high intensity percussion very difficult. Close to the source the pressure can be very high, which could also be the case in reproduction, where the distance would also matter.

Anyway the effect when it comes to body sensation is that of the body acting as an acoustic absorber. The way the auditory mechanism maps the dynamic range, at SPL exceeding the realm of common sense when it becomes primarily a body sensation should be a good enough reason not to expose yourself for any extended period of time.

Even though with low frequencies you should be safe, there could be the case of high perceived loudness for sharp signals of higher bandwidth. By this I mean the usual practice of harmonics introduced to the signal as to increase the perception of bass in smaller systems incapable of reproducing the fundamentals. And then reproducing it on a system that actually does.

 

[Alice of Old Vincennes]

Many super-expensive high-end top-of-the-line systems are actually sub-satelite systems, I'm always baffled why it's not done more.

Gee, why didn’t Revel, Perlisten, KEF, etc think of that concept?

 

[Alice of Old Vincennes]

Sub integration? Really?

It’s only hard if you don’t know how to do it.

The minimum XO slope for your setup should be at least 24dB/oct. and, ideally, higher. I like using Linkwitz/Riley filters. When I use outboard XOs, I prefer steeper than that for the sub.

You XO point should be set one octave above the -3dB spec for your mains. This reduces distortion and increases system dynamic range. Loudspeaker designers do the exact same thing when selecting the XO point from a tweeter to a mid.

Again, the sub isn’t just being used to add low bass. You’re expanding the capabilities of your speaker and improving its performance.

Why don’t sub manufacturers recommend this simple solution?

 

[Alice of Old Vincennes]

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

Of course, the big thing to then look at with your specific speakers is where, when tested, do their woofers stop acting linear and start to distort? That point where the distortion starts increasing logarithmically is where you set the crossover. Maybe just a bit higher.

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.

Really, ported speakers should plugged? Nonsense.

 

[Alice of Old Vincennes]

My case is below. Really happy with it. Subs with ART are going to 100hz and bass localization was never better. Flies in the face of all my previous experiments and stups, but I am not shy to admit it. I was trying my best to get to something that ART does so much better with zero effort.

Don't mind the bed, it is just another convenience feature. I'd take it anytime over the swivel chair that has been resting in the cellar for years.


View attachment 529653

Now that’s a family room!

 

[Keith_W]

Why don’t sub manufacturers recommend this simple solution?

Marketing. To integrate subs properly, you need to be able to take and interpret measurements. Then you need some DSP to get the subs to work with the mains. That's a huge barrier to sales. Maybe people don't want to go through that effort. Maybe they have misgivings about DSP. Maybe they don't believe in measurements. Better to go the REL route and say "just plug your amplifier output into this sub, don't bother with DSP, don't bother with high-pass, it will just work", and you will get more sales.

Remember: we are in it for the sound quality. Manufacturers are in it for money. The two motivations are not necessarily aligned.

 

[EJ3]

Now that’s a family room!

Unfortunately my wife does not like audio. She much preferes that there is no external audio on, at home, in the car, anywhere.
I go to concerts with friends and leave her home (which she prefers). On the patio on nice days & inside if rainy days.
But, when we build our next home on our next property, I get my own audio/video room and my own workshop/auto shop.
So, worth the tradeoff for now.