Why do bigger subwoofers sound different?

[Keith_W]

I am sure that this has been discussed before in ASR, but I did a search and could not find it. Mods please feel free to merge the thread if this topic has come up before.

Basically I have noticed that even if two subs (say) with a 10" driver and an 18" driver produce 40Hz at 80dB, the bigger sub sounds different. I can't get my head around this, after all if they are both outputting the same frequency at the same volume, at those super long wavelengths surely they must sound the same? What am I missing here?

 

[staticV3]

Could be different positioning in the room causing slightly different room modes, could be harmonic distortion, could be port noise, could be that the smaller sub is already entering compression.

Record both and post the files here, then we can tell you more.

 

[Keith_W]

Well, it's actually different systems. There is my system, which has four 12" subs which has been DSP'ed to an inch of it's life. Then there's my friend's system, who has two 18" subs. The rooms are roughly the same size. Even at the same SPL, the impact of those subs is something else. So I am not sure I can post a recording, or even a sweep. I can post my own sweep, but not the other system.

 

[staticV3]

That seems rather apples vs oranges then, not really "10in vs 18in"

 

[ppataki]

I am sure that this has been discussed before in ASR, but I did a search and could not find it. Mods please feel free to merge the thread if this topic has come up before.

Basically I have noticed that even if two subs (say) with a 10" driver and an 18" driver produce 40Hz at 80dB, the bigger sub sounds different. I can't get my head around this, after all if they are both outputting the same frequency at the same volume, at those super long wavelengths surely they must sound the same? What am I missing here?

Couldn't it be that the two systems have slightly different settings for the lows? What I mean is for example the bass boost, low shelves, etc. are set up differently?
Even a slight difference in how the low end is boosted can result in totally audible differences, the point in frequency where the boost starts, the amount of boost and the Q value of the boost all contribute to it

 

[jhaider]

I am sure that this has been discussed before in ASR, but I did a search and could not find it. Mods please feel free to merge the thread if this topic has come up before.

Basically I have noticed that even if two subs (say) with a 10" driver and an 18" driver produce 40Hz at 80dB, the bigger sub sounds different. I can't get my head around this, after all if they are both outputting the same frequency at the same volume, at those super long wavelengths surely they must sound the same? What am I missing here?

It’s basically an impossible experiment to do. You have to be able to listen to both subs centered in the same position to make a reasonable determination, but matter does not work like that. Even EQ’ing at the listening position doesn’t get you there because EQ’ing room modes has consequences (good and bad!) for system headroom.

That said, I have not noticed such a difference, so long as both systems have the headroom to play at the desired levels with reasonable dynamic linearity.

 

[DVDdoug]

Basically I have noticed that even if two subs (say) with a 10" driver and an 18" driver produce 40Hz at 80dB, the bigger sub sounds different.

Distortion from the smaller driver?

Well, it's actually different systems. There is my system, which has four 12" subs which has been DSP'ed to an inch of it's life. Then there's my friend's system, who has two 18" subs. The rooms are roughly the same size. Even at the same SPL, the impact of those subs is something else.

If you measure with REW and a measurement mic, I'd bet there are differences.

And... It's pretty hard to A/B or ABX between two different houses/locations.

 

[Puddingbuks]

The room is what you hear mostly, the standing waves, peaks and nulls, the reverb - it all has significant impact on the overall sound.

Comparing different speakers in different rooms is difficult if not impossible. Sure, you can compare the sound, but what do differences mean?

 

[moonlight rainbow dream]

A couple of things... when people claim that the two systems being compared have the same frequency response or same output, that is almost never true when you dig into it. Just anecdotal, but when I've personally experienced the sensation of a bigger speaker sounding bigger and taken the time to do a simple in-room measurement... there are always clear differences. e.g. more extension, several dB more output, or a reduced floor bounce dip.

The other part of this is "pressurization" which is often talked about in HT circles. I believe that this phenomenon is the sum of everything that's not purely the acoustic pressure wave detected by the ear (or a mic).. so mainly, the wind from the operation of the driver and/or port and its ability to vibrate you and your surroundings. A simple example is the "pants leg flapping" effect. Bigger drivers create more wind and the effect can be enhanced by sealing off the room and/or bringing the speakers into closer proximity.

 

[AdamG]

A couple of things... when people claim that the two systems being compared have the same frequency response or same output, that is almost never true when you dig into it. Just anecdotal, but when I've personally experienced the sensation of a bigger speaker sounding bigger and taken the time to do a simple in-room measurement... there are always clear differences. e.g. more extension, several dB more output, or a reduced floor bounce dip.

The other part of this is "pressurization" which is often talked about in HT circles. I believe that this phenomenon is the sum of everything that's not purely the acoustic pressure wave detected by the ear (or a mic).. so mainly, the wind from the operation of the driver and/or port and its ability to vibrate you and your surroundings. A simple example is the "pants leg flapping" effect. Bigger drivers create more wind and the effect can be enhanced by sealing off the room and/or bringing the speakers into closer proximity.

Tactile energy. With bigger drivers in my limited experience. You tend to feel the bass as much as hear it. Two movie as an example is the Pod Emergence scene in “War of the Worlds” and the Black hole scene in “Interstellar”. In both these scenes I feel the bass against my body/cloathing more than hear it. It’s a difficult sensation to describe but I have read that this is due to the greater amount of Tactile Energy produced by larger drivers at the same frequency. I went from dual 13” to dual 18” and the difference in this Tactile Energy was very noticeable. I’m not entirely certain how this phenomenon can be measured. So this is just another personal Opinion.

 

[staticV3]

greater amount of Tactile Energy produced by larger drivers at the same frequency

Same frequency at the same amplitude -> same tactile energy.

If instead of single tone sine waves you play soundtracks and you don't high-pass the larger sub to match the smaller, then it'll naturally sound larger. But I don't think that was what OP was asking about.

 

[jhaider]

Bigger drivers create more wind

Why would this be true? For a given bass SPL volume of air displaced is the same. Not saying you’re wrong, but I think if true we’d need to dig into the mechanism.

 

[moonlight rainbow dream]

Why would this be true? For a given bass SPL volume of air displaced is the same. Not saying you’re wrong, but I think if true we’d need to dig into the mechanism.

I'm not sure, but if you've ever overdriven a large speaker with a front-firing port and been blasted by the wind (in my case, it was most noticeable with a diy centre using 2x rs180 with 2x 1.5-inch ports, 41hz tuning; and not any of my 12" subs funnily enough), I definitely think there's a component of the air movement that is not directly tied to the measured acoustic output of the speaker. Heck, it may even be termed distortion of some kind, and people who utilize very large subwoofers, nearfield subs, bass shakers, etc. are chasing that "distortion".

 

[gnarly]

I think subwoofers have some sort of output vector, in addition to the well known radiation patterns. I think it comes from the baffle/box the drivers are in, combined with port location, if ported. I've read about wavefront velocity vs acceleration, but don't grasp any of that yet, or have a clue if it describes this "vector" though..

So i don't know how to describe it other than give some examples.

All three of the following sub setups use the same two double 18" drivers. All three are ported to very close to the same f-3 (25-30Hz).
All three are used with a very steep low pass at 100Hz, 96 dB/oct, so there is very little "non-sub / localizable" output from them.

All three sound tonally the same, when it comes to steady state tones.
They differ when it comes to transients.

The first sub is a push-push slot loaded (clamshell type). The slot has a little over the area of one driver's Sd, so almost a 2:1 compression ratio.
Kicks/punches like a beast.





But a bit surprisingly, the PPSL doesn't hit quite as hard as the same two drivers in two standard single 18" ported boxes on top of each other.



And more surprisingly, both the above punch harder than this big baffle guy with the same drivers, that has downward firing ports.




I've spent a lot of time with each of these underneath the same top main speaker, in the same spot in the middle of a fairly big room.
In mono.

One of my favorite tests besides hearing and feeling, is empty beer/coke cans on a table next to listening position.
And see how much SPL it takes to blow the can off the table, with a big bass drop.
The plain old double 18" is the champ, maybe simply because some of the the ports are closer to listening height level.
Dunno....I just know when it comes to transients....bass doesn't seem to be so dang omni after all.

 

[AdamG]

is empty beer

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

 

[Duke]

The first sub is a push-push slot loaded (clamshell type). The slot has a little over the area of one drivers Sd, so almost a 2:1 compression ratio.
Kicks/punches like a beast...

But a bit surprisingly, the PPSL doesn't hit quite as hard as the same two drivers in two standard single 18" ported boxes on top of each other.

And more surprisingly, both the above punch harder than this big baffle guy with the same drivers, that has downward firing ports.

Do these differences hold up at distance?

The slot loading funnels the frontwave of both drivers into a smaller, and therefore higher pressure, area, which would result in more punch at close range, especially with the ports aiming in the same direction. Along similar lines the front-facing ports on the stacked ported box contribute to impact at close range. In both cases I would expect the improved sensation of impact to fade away with distance, but I've never actually done an ears-on comparison.

Out in the venue, where the audience is, is there still a significant difference in impact?

 

[Ron Texas]

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

We need to have an ASR beer bash.

 

[gnarly]

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

I wish I could host all you guys for a beer can shootout ! Would be fun / nice
@ Ron, hell yeah ASR beer bash!

Do these differences hold up at distance?

The slot loading funnels the frontwave of both drivers into a smaller, and therefore higher pressure, area, which would result in more punch at close range, especially with the ports aiming in the same direction. Along similar lines the front-facing ports on the stacked ported box contribute to impact at close range. In both cases I would expect the improved sensation of impact to fade away with distance, but I've never actually done an ears-on comparison.

Out in the venue, where the audience is, is there still a significant difference in impact?

I'm reluctant to say. Outside is where i have to go for greater listening distances, and then it's usually a lot greater. (indoors is about 15ft)
Once I get outside, the amount punch and kick of any one of those single double 18" setups i poset, needs more boxes.
I only have the two of the single 18" ported subs. So no larger scale comparisons are available.

I do have my fav and champion outdoor setup though,,,,

I've read live-sound guys debate a block of horn loaded subs like these vs a wall of conventional ported subs.
Consensus seems to be that the horn loaded is better at flapping pants, etc
And that a wall of 18"s is better at punching guts lol

 

[jhaider]

I've read live-sound guys debate a block of horn loaded subs like these vs a wall of conventional ported subs.
Consensus seems to be that the horn loaded is better at flapping pants, etc
And that a wall of 18"s is better at punching guts lol

I’m curious if anyone knows what the bottom end at Riot Fest in Chicago two weekends ago was. That main stage(s)had the most chest compression/pants flapping bass I’ve felt in an outdoor concert. BUT it was also clear that it was tuned for punk rock kick drums. When the Postal Service came on with some lower electronic stuff (e.g. “Brand New Colony”) pitch definition on the deepest notes was lost.

 

[Sokel]

Maybe a silly thought:
Smaller drivers maybe pushes the same volume of air but it's bigger displacement takes more time.
The bigger driver makes it (a lot) faster over a bigger area capturing more air to push in it's bigger cone at a given time.

Doesn't that have an impact on the wave plane (excuse my english if it's not the right term).

(I like to think of stuff like this as if they were in water,I'm visual,so... )