Why do bigger subwoofers sound different?

[staticV3]

Smaller drivers maybe pushes the same volume of air but it's bigger displacement takes more time.

A smaller driver will move farther and faster in each cycle to make up for the lower surface area.
That means that the same volume of air is displaced in the same amount of time as with the larger driver, and of course both wave planes move at the same speed (~343m/s).

"Speed" is one of those audiophile myths

 

[Sokel]

A smaller driver will move farther and faster in each cycle to make up for the lower surface area.
That means that the same volume of air is displaced in the same amount of time as with the larger driver, and of course both wave planes move at the same speed (~343m/s).

I know,but that bigger displacement takes longer time,the distance alone dictates that.
If both have strong motors none will be faster in response,is just that the bigger one will have less distance to travel.

 

[fpitas]

Well, I have 15" woofers. So, they're the best. Glad that's settled!

 

[staticV3]

I know,but that bigger displacement takes longer time,the distance alone dictates that.

If both drivers play 40Hz at 80dB SPL, then every 25ms, they will displace the same amount of air and take the same amount of time from "top" to "bottom" (12.5ms).

The larger driver will move a shorter distance at a lower speed, the smaller one a larger distance at a higher speed. Both drivers reach the end in the same amount of time.

If both have strong motors either will be faster in response,is just that the bigger one will have less distance to travel.

And it'll travel that distance at a slower average speed.
If it completed the cycle sooner than the smaller driver, then it would no longer play the same frequency

 

[Sokel]

And it'll travel that distance at a slower speed.

Traveling is dictated by the electrical signal,how this can be faster or slower at the same freq?
The cones will jump at the same time,at the same speed,the one will travel the appropriate distance to give the SPL we want and the other a little longer.

 

[staticV3]

Traveling is dictated by the electrical signal,how this can be faster or slower at the same freq?

The frequency of the movement is dictated by the frequency of the electrical signal.

The speed of the movement is dictated by the signal's amplitude, as well as by the magnet strength, motor stiffness, coil design, etc.

 

[staticV3]

The cones will jump at the same time,at the same speed,the one will travel the appropriate distance to give the SPL we want and the other a little longer.

If one cone moves a little longer than the other before reaching TDC/TBC, then it is no longer playing the same frequency of sound.

 

[Sokel]

The frequency of the movement is dictated by the frequency of the electrical signal.

The speed of the movement is dictated by the signal's amplitude, as well as by the magnet strength, motor stiffness, coil design, etc.

Exactly,that's why I said both to have strong motors so that will not be the limiting factor (there are beasts of motors out there).

 

[Axo1989]

I volunteer for the job of emptying the beer cans. I prefer bottles but one can not be too fussy.

You are going to need way more of a bass wave to knock empty glass bottles over. A cunning plan, I reckon.

 

[Sokel]

If one cone moves a little longer than the other before reaching TDC/TBC, then it is no longer playing the same frequency of sound.

Of course we're always talking about the optimal operating area of both drivers.

 

[staticV3]

Exactly,that's why I said both to have strong motors so that will not be the limiting factor (there are beasts of motors out there).

I still don't think you fully understand.
To produce the same tone at the same amplitude, the larger membrane will accelerate softer and move slower and over less distance than the small one, because its surface area compensates.

Both membranes will complete each cycle in the same amount of time and will have displaced the same volume of air in the process.

 

[Sokel]

I still don't think you fully understand.
To produce the same tone at the same amplitude, the larger membrane will accelerate softer and move slower and over less distance than the small one, because its surface area compensates.

Both membranes will complete each cycle in the same amount of time and will have displaced the same volume of air in the process.

I will have to think about it a little more I think,I obviously miss something.
I have in front of me a 10" and a 15" raw drivers I will make them play both a low level 10Hz so I can see how they handle it and how they move.

(I already said,it was a silly thought)

 

[Sokel]

I will have to think about it a little more I think,I obviously miss something.
I have in front of me a 10" and a 15" raw drivers I will make them play both a low level 10Hz so I can see how they handle it and how they move.

(I already said,it was a silly thought)

An initial observation is that the 10" moves a lot more back and forth than the 15".

(end of tests for today,tomorrow I'll measure them with REW too )

 

[staticV3]

I will have to think about it a little more I think,I obviously miss something.
I have in front of me a 10" and a 15" raw drivers I will make them play both a low level 10Hz so I can see how they handle it and how they move.

To be fair, it is more of a logic problem that may not be so easy to perceive with bare eyes.

1. Same SPL at same frequency means same volume of air displaced per cycle

2. Imagine a cube with a fixed volume. If you reduce its length and width (=smaller membrane), then the height must increase to compensate.

3. When both membranes reach top and bottom at the same time (they must, otherwise the audio frequency does not match), then the smaller driver with the taller cube has to move faster to get to the top, compared to the larger membrane and its shallow cube.

 

[Keith_W]

I agree with @AdamG247 comment that larger subs seem to be more tactile. I should have been clearer, I have experienced this multiple times in multiple setups. I do not have measurements for any of them, only an SPL meter. Perhaps people who own larger subwoofers like bass and so they dial them up higher - that could be a reason. But in my system, if I tried turning the subs up (I mentioned earlier that I have 4x 12" drivers), it quickly sounds unbalanced and bass heavy, way before I get that tactile feeling and slam that I experience with larger subs.

I wondered about whether it is the way larger drivers pressurize the room, but then if SPL is the same then surely the room has been pressurized to the same extent regardless of the size of the driver.

I have another silly thought - below a certain wavelength, sound behaves in compression mode rather than modal (where standing waves are formed). I think it was 1/4 wavelength of the dimensions of your room (varies according to which dimension, obviously?) - someone can correct me if I am wrong. Does compression mode sound different to modal bass, besides (obviously) the lack of room modes?

I know many objectivists tend to dismiss what they can not measure, or measure to be the same. I am a bit like that. But my experience with this phenomenon is so strong that I am seeking an explanation.

 

[Chrispy]

I agree with @AdamG247 comment that larger subs seem to be more tactile. I should have been clearer, I have experienced this multiple times in multiple setups. I do not have measurements for any of them, only an SPL meter. Perhaps people who own larger subwoofers like bass and so they dial them up higher - that could be a reason. But in my system, if I tried turning the subs up (I mentioned earlier that I have 4x 12" drivers), it quickly sounds unbalanced and bass heavy, way before I get that tactile feeling and slam that I experience with larger subs.

I wondered about whether it is the way larger drivers pressurize the room, but then if SPL is the same then surely the room has been pressurized to the same extent regardless of the size of the driver.

I have another silly thought - below a certain wavelength, sound behaves in compression mode rather than modal (where standing waves are formed). I think it was 1/4 wavelength of the dimensions of your room (varies according to which dimension, obviously?) - someone can correct me if I am wrong. Does compression mode sound different to modal bass, besides (obviously) the lack of room modes?

I know many objectivists tend to dismiss what they can not measure, or measure to be the same. I am a bit like that. But my experience with this phenomenon is so strong that I am seeking an explanation.

Different subs in different rooms are very hard to compare properly. OTOH I do definitely prefer my 18"s over my 12"s, altho in a small room the 12s can do quite well.

 

[test1223]

There are another two aspects I want to point out:

1. Structural sound and vibration transmission of the listening room > coupling of the subwoofer to the floor > bigger heavier box better coupling > higher amount of structural sound and vibration > the perception of deep bass is causes a lot via vibration.

2. Bigger woofer > lower none linear distortion > lower perceived sub bass at same spl > higher listening level is dialed in by the user.

 

[mj30250]

There are another two aspects I want to point out:

1. Structural sound and vibration transmission of the listening room > coupling of the subwoofer to the floor > bigger heavier box better coupling > higher amount of structural sound and vibration > the perception of deep bass is causes a lot via vibration.

This was my immediate thought. Even though the two rooms that the OP described are roughly the same size, they are likely not subject to the same amount / variety of structural (and other) vibrations to begin with, and then when you couple larger boxes to the floor, you could very well be hearing more of the room itself (as well as the things in it) in the case of the larger subs. Of course, not knowing all of the relevant details, that's just pure speculation.

From personal experience, I've chased down and resolved some irritating room vibrations which had the side effect of making my subs appear to drop in output. Of course, no such thing happened, but certain vibrations can certainly offer increased "impact" as a side benefit, sometimes even the irritating ones.

 

[test1223]

This was my immediate thought. Even though the two rooms that the OP described are roughly the same size, they are likely not subject to the same amount / variety of structural (and other) vibrations to begin with, and then when you couple larger boxes to the floor, you could very well be hearing more of the room itself (as well as the things in it) in the case of the larger subs. Of course, not knowing all of the relevant details, that's just pure speculation.

From personal experience, I've chased down and resolved some irritating room vibrations which had the side effect of making my subs appear to drop in output. Of course, no such thing happened, but certain vibrations can certainly offer increased "impact" as a side benefit, even some of the irritating ones.

You often have vibrations and structural sound which you can't detect as such. Think of the floor as a transmitter of sound like when you hear the bass from the sound outside of your house. It is similar for the vibration of the floor like when you stand near a washing machine the sub bass shakes your floor but it blends in with the perception of the air sound waves, which also shake your body.

 

[Bjorn]

Is using 10" driver really a subwoofer? Way too small to output enough, can seldom take much power, and there's high modulation distortion. Two don't equal a quality 18" either.

Plus small commercial subwoofers like that are generally poorly designed.