Big subs vs Small subs

[Keith_W]

Have any of you heard a rotary subwoofer? These things are capable of going down to 1Hz at very low distortion thanks to its efficiency. I haven't been lucky enough to hear one, but reviews from people who have vary between overwhelming and nausea inducing because of the intensity.

 

[charleski]

14.2 Sound Intensity and Sound Level - Physics | OpenStax

In a quiet forest, you can sometimes hear a single leaf fall to the ground. But in a traffic jam filled with honking cars, you may have to shout just so...

openstax.org

So sound intensity is just proportional to the square of the sound pressure. If you know the air density and speed of sound then measuring the sound pressure is the same as measuring the sound intensity. It's invalid to suggest there's a fundamental difference between these two measures, they're related in the same way as the voltage and power output of an amp.

At 20Hz an 18" driver will be able to go louder than a 12". That's all there is to it. If you want to play bass at high levels then you need a big sub. If you just want a sub to fill in at less than 75dB so you don't annoy the neighbours then you can get away with something a lot smaller.

 

[Sokel]

So sound intensity is just proportional to the square of the sound pressure. If you know the air density and speed of sound then measuring the sound pressure is the same as measuring the sound intensity. It's invalid to suggest there's a fundamental difference between these two measures, they're related in the same way as the voltage and power output of an amp.

At 20Hz an 18" driver will be able to go louder than a 12". That's all there is to it. If you want to play bass at high levels then you need a big sub. If you just want a sub to fill in at less than 75dB so you don't annoy the neighbours then you can get away with something a lot smaller.

I would say that add to each other than differentiate.
I must confess that even If I have heard about it by pros in venue never gave much attention to it,it's the first time I had a look at it after the post the friend above posted.

 

[dasdoing]

Yeah I would emphasize that tuning and integration is very important. Took me a while to get it to sound right and have just the right amount of tactile response. I use a miniDSP with Multi Sub Optimizer; had to play with the target curves and the crossovers/slopes on the miniDSP a bit.

It was REW EQed, and I don't even use the Harman boost

 

[dasdoing]

So sound intensity is just proportional to the square of the sound pressure. If you know the air density and speed of sound then measuring the sound pressure is the same as measuring the sound intensity. It's invalid to suggest there's a fundamental difference between these two measures, they're related in the same way as the voltage and power output of an amp.

That was my conclusion, too.

 

[dasdoing]

So how does a nearfield sub get so tactile? At same loud SPL you wont feel it at the wall, but it rumbles your ass behind the seat.
I guess it's because your seat will proportionally be absorbing more energy?

 

[Sokel]

So how does a nearfield sub get so tactile? At same loud SPL you wont feel it at the wall, but it rumbles your ass behind the seat.
I guess it's because your seat will proportionally be absorbing more energy?

Only by experience as tactile feel is a virtue that I always want.
Big speakers (cabinets) - big drivers gives you plenty.Specially in mid-bass,that's where this feeling is stronger not lower.
Old big speakers with big mid-bass drivers crossed at 250-500Hz gave that feeling easy despite their inability to go deep down.

 

[Bjorn]

Bigger drivers=equals lower modulation distortion. If there's good control of resonances in the room, that tend to be quite audible with a more effortless bass. A horn loaded subwoofer is king here and will equal several front firing drivers.

With movies where you can have high peaks in the lows it becomes even more audible since a smaller sub may not produce the full dynamics besides distortion with higher level also increases.

 

[Zapper]

Even a 5" can produce 10Hz and have low distortion, but only on a very low volume. the bigger the driver, the louder it can go on that frequency. And the harder you drive a driver to it's limits, the more distortion it makes. So a 18" and a 12" at the same frequency and volume will not necesairly sound the same, as the 18" wil probally have way more headroom and less distortion than the 12" (depending on the model and cabinet) as you use less of it's capacity of producing that frequency. It's similar as with amps and headroom.

The OP did stipulate that both subs had the same distortion at the given frequency and SPL. I agree that a larger woofer is likely to have less distortion, given similar quality construction.

 

[Zapper]

So how does a nearfield sub get so tactile? At same loud SPL you wont feel it at the wall, but it rumbles your ass behind the seat.
I guess it's because your seat will proportionally be absorbing more energy?

Right. The seat has more surface area to absorb the bass from the air and couple the motion to your ass. It's a type of impedance matching device, from a lower pressure / larger area (seatback) to a higher pressure / smaller area (your ass).

 

[robwpdx]

On subs, you can get very small - producers and consumer listeners will sometimes use the SubPac or similar brands. It straps on, has batteries and has a wired or wireless program feed. You also see the same in gamer chair tactile pads.

A friend of mine is deaf. He has a project to translate music to other senses, light and tactile. The SubPac company has been very generous in supporting projects like that. The transducer is small and battery powered, but ideal for one person to feel bass.

The other thing you see is the DBX patented subsonic synthesizer in pro gear. A producer can use it in the studio to add bass, or a pro sound installation which needs bass for EDM can use it. There are competing implementation plugins for audio production software. They are sometimes used on the bass drum in tracking. It is certainly not a linear item we usually discuss, but in recording many deliberate nonlinear effects are used.

https://dbxpro.com/en/product_families/subharmonic-synthesis

A friend built a large and heavy outdoor dance sub with a linear actuator, but I don't know what the piston was attached to. I believe it was this. The main expense was renting a storage space and trucks to move it.

 

[robwpdx]

Many know Dave Rat who does very large shows. Here he discusses building a system capable of producing a lot of bass for an audience in the round, The video discusses Soundvision software from the speaker/amp maker https://www.l-acoustics.com/ and then adjusting the system in real time based on the temperature of the venue during the show. The DJ has since been disgraced for preying on his young female fans.

 

[Astoneroad]

12 inchers are not going to fairly compete with 18” drivers. If you have close neighbors or live in a multi family building get the 12’s and you might get away with it. The JTR’s are definitely going to piss off any close neighbors.

I guess that everything is relative. For me, the 12" drivers were a step up... and experienced the same difference (to a lesser degree) as you describing the air motion as palpable... just not as much as those monsters as yours. Somehow I manage to piss off my neighbors just fine with it.

 

[ex audiophile]

Even a 5" can produce 10Hz and have low distortion, but only on a very low volume. the bigger the driver, the louder it can go on that frequency. And the harder you drive a driver to it's limits, the more distortion it makes. So a 18" and a 12" at the same frequency and volume will not necesairly sound the same, as the 18" wil probally have way more headroom and less distortion than the 12" (depending on the model and cabinet) as you use less of it's capacity of producing that frequency. It's similar as with amps and headroom.

So you and @Zapper would agree that if the distortion were equal the sound from the two subs (18 and 12) would be indistinguishable in an unsighted comparison? Many of us "less knowledgeable" audio enthusiasts just assume bigger is better and for HT there is merit to that argument (for special effects). What I'm getting from this is that for music, esp if we listen at sub90 spl levels, 10 and 12 inch subs are all that is needed to round out the bottom frequencies.

 

[ex audiophile]

Right. The seat has more surface area to absorb the bass from the air and couple the motion to your ass. It's a type of impedance matching device, from a lower pressure / larger area (seatback) to a higher pressure / smaller area (your ass).

So if the ass was larger than the seatback the pressure would be dissipated; would this cause a peak or a null in the room?

 

[Waxx]

So you and @Zapper would agree that if the distortion were equal the sound from the two subs (18 and 12) would be indistinguishable in an unsighted comparison? Many of us "less knowledgeable" audio enthusiasts just assume bigger is better and for HT there is merit to that argument (for special effects). But for music, esp if we listen at sub90 spl levels, 10 and 12 inch subs are all that is needed to round out the bottom frequencies.

My subs for a small listening room is with the 10" Scanspeak 26W8534G00 and it does the job for that small place. So yes i do. But if you want a lot of power, you need more cone surface and magnet strength, so multiples or bigger drivers are needed. I cross that one actually in the bass region so it's a sub and bass woofer for me. And most of my systems are even using smaller drivers for the low frequencies, but are used in small places on low volume. I don't need 120dB at 20Hz. I can live with 100dB at 30Hz peak power and mostly listen in the 65 to 85dB RMS range to music at home and don't do HT stuff (i don't even have a TV).

The main thing with subs is, don't stress them, don't run them on their limit. A big room needs a big sub (and preferable more than one), a small room can work with a small sub (also preferable more than one) tuned low and the get the pressure you want. That 10" i use can pressure the room like a big stack of 18" subs does in a big hall, even on half power or less. In my old house i could make the whole room shake with a pair of that 10", then in a a cabinet tuned to 25hz, powered by a 2x45w amp. But that room was about 3x6x2.5m large...

 

[Kvalsvoll]

So sound intensity is just proportional to the square of the sound pressure. If you know the air density and speed of sound then measuring the sound pressure is the same as measuring the sound intensity. It's invalid to suggest there's a fundamental difference between these two measures, they're related in the same way as the voltage and power output of an amp.

At 20Hz an 18" driver will be able to go louder than a 12". That's all there is to it. If you want to play bass at high levels then you need a big sub. If you just want a sub to fill in at less than 75dB so you don't annoy the neighbours then you can get away with something a lot smaller.

Wrong.

Intensity relative to pressure depends on acoustic impedance, which again is determined by the sound source and acoustic surroundings. Situation is simple for a plane wave, and quite simple for a sphehrical wave, where it can be shown that SI rlative to pressure depends on the distance from the sound source.

In a normal (small..) room the room affects acoustic impedance in such a way that no simple plane wave or spherical wave approximation is valid. So some locations in the room has better tactile, some rooms are better tactile. Moveyouerlf or the bass source, and the situation changes.

AND: Some subwoofers/bass-systems actually sound significantly different from the typical small closed box you find in a hifi-shop. Due to differences in radiated sound field. Hint: horns are different..

 

[Waxx]

Wrong.

Intensity relative to pressure depends on acoustic impedance, which again is determined by the sound source and acoustic surroundings. Situation is simple for a plane wave, and quite simple for a sphehrical wave, where it can be shown that SI rlative to pressure depends on the distance from the sound source.

In a normal (small..) room the room affects acoustic impedance in such a way that no simple plane wave or spherical wave approximation is valid. So some locations in the room has better tactile, some rooms are better tactile. Moveyouerlf or the bass source, and the situation changes.

AND: Some subwoofers/bass-systems actually sound significantly different from the typical small closed box you find in a hifi-shop. Due to differences in radiated sound field. Hint: horns are different..

The trick is with small sub drivers, don't put them in a small box and eq the shit out of them. Use a driver that can give the sub frequencies in a big (sealed or ported or TL) cabinet with no or minimal eq. Horns can do that also, but are even bigger.

 

[fpitas]

All I know is they will have to take my 15" woofers from my cold, dead hands

 

[Urubamba]

So I was considering the pros and cons of large vs small subwoofers. Clearly if you need to reproduce 10hz at 100+ db you need a large driver, something from JTR, Funk etc.

But what if you're producing 20 hz at 90db? Does a large driver, say 18" sound different than a small driver, say 12" assuming equal spl and distortion? The frequency range of the cello and double bass overlap, so do they sound the same when producing the same frequency at the same volume?
I don't know, but if the large and the small driver are both moving the same quantity of air at the same frequency they should sound the same. The smaller driver just has to make a larger excursion with each cycle. Would enjoy hearing thoughts of others.

The small driver distorts more than the large one because the displacement of the cone is much greaterto get the same SPL . There is a myth that goes by the aesthetic vision in subwoofers. We all like to see how the speaker cone moves a lot, but that is not synonymous with quality bass. On the contrary.