• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Bass production and membrane area

Joined
Sep 24, 2019
Messages
91
Likes
53
Location
Haifa, IL
#1
This is a hypothetical question.

Assuming that we are in a reasonable living room (not a huge mansion), and our goal is to reproduce acoustically played music (i.e. not electronic, not movies), what would be the maximum woofer membrane area in order to produce bass, above which there would be no audible difference?

For example, suppose we have about 900-1,000 cm2 of total radiating area (12'' or 3 X 6.5'' woofers give or take, times 2 speakers). We want to reproduce double bass drum kicks, a church organ, these sorts of things. At which size of membrane area does it stop mattering? 15'' drivers? 18''? 3 X 10''?

Again, I'm talking about music reproduction in a domestic room, not earthquake bass of some movies that doesn't exist in acoustic music.
 
Last edited:

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
7,544
Likes
15,125
Location
The Neverlands
#3
I liked the phrase: 'There is no replacement for displacement' when it comes to bass reproduction.

The larger the surface area the less excursion is needed.
The smaller the needed excursion the easier it is to make a linear driver.
Of course room size & properties also matter.

When you have a large diameter woofer but a non-linear voicecoil and a smaller diameter woofer but with a huge and linear excursion the smaller diameter woofer may be preferred.

In short, if you want deep lows, impressive levels and real world feel using large surface area woofers keeps costs and engineering efforts down.
 

sergeauckland

Major Contributor
Forum Donor
Joined
Mar 16, 2016
Messages
1,923
Likes
4,431
Location
Suffolk UK
#4
As far as I know, it's not the area of the bass driver, but the volume of air shifted, so theoretically a large driver moving a small distance would be the equivalent of a small driver moving a large distance.

Furthermore, small drivers are easier to make and can be made more rigid so breakup at higher frequencies which are easier to deal with in the crossover, especially if the loudspeaker system is three way (or more) . It's also easier to get low distortion from a small driver as long as it's not being asked to do too much, but distortion is linked to excursion linked to efficiency due to magnetic gap linearity.

However, two or more small drivers will cost more than one large one, so there's a trade off to be made (isn't there always?). Cosmetically, the market has decided that tall thin loudspeakers are preferable to wide ones, so there's a commercial imperative to use multiple small units rather than a large one.

As far as I'm concerned personally, I prefer a large driver moving a small distance than smaller drivers although I accept that may be purely cosmetic in my case as I like big loudspeakers.

In conclusion, I don't think there's any particular merit in one approach over another. It may be of interest that in large professional monitoring loudspeakers like Genelec and PMC, they use multiple large units as what matters is volume of air shifted not how it's shifted.

S.
 

briskly

Active Member
Joined
Jul 10, 2019
Messages
103
Likes
131
#6
For drivers in half space:
P= 2π * f² * Sd * Xmax * ρ / r
ρ is air density, r is distance from driver. SPL peak in SI units is then:
94 + 20log(P)
One conclusion to be drawn here is that volume displacement required to sustain constant SPL against frequency is inverse square. A second-order cutoff, or a 12dB/octave slope for a given volume displacement.
Talking about the surface area of the radiator brings up engineering challenges in realizing the desired volume displacements. Some are discussed in the Purifi midwoofer thread.
 

Duke

Addicted to Fun and Learning
Manufacturer
Forum Donor
Joined
Apr 22, 2016
Messages
529
Likes
1,068
Location
Princeton, Texas
#7
I do not know the point at which adding more woofer cone area makes no audible difference. I have not yet found it.

That being said, given that room acoustics inevitably impose a significant peak-and-dip pattern on any woofer's output, addressing room interaction issues is imo more productive than maximizing woofer cone area.
 

CDMC

Major Contributor
Forum Donor
Joined
Sep 4, 2019
Messages
1,028
Likes
1,865
#8
Just my two cents based on my observations over the years. I have no scientific basis for my belief. I have found that larger drivers seem to couple better with the room. It could be psychological, it could be real, I don't know for sure.
 
OP
R
Joined
Sep 24, 2019
Messages
91
Likes
53
Location
Haifa, IL
Thread Starter #10
I don't get it...

Given that real drums, in room, displace a finite amount of air, isn't there a finite membrane area that can displace the same amount of air in a linear fashion? (I know, it can never be perfectly linear etc. I mean as linear as reasonbly possible)

So is any increase in size beneficial by definision? A speaker cannot be huge enough? So if I have Wilson Chronosonics, I should strive for WAMM Master Chronosonics for significantly better bass and air displacement? and maybe add a couple of PA subwoofers on top? (I exaggerate for argument's sake, but you get the point)
 

RayDunzl

Major Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
10,923
Likes
10,602
Location
Riverview FL
#11
Given that real drums
Drums come in different sizes for different frequencies...


Looks like power handing (00:37) is important too...
 

aac

Member
Joined
May 17, 2020
Messages
69
Likes
37
#12
Just my two cents based on my observations over the years. I have no scientific basis for my belief. I have found that larger drivers seem to couple better with the room. It could be psychological, it could be real, I don't know for sure.
The larger the driver, the better directivity control is.
 

Mnyb

Addicted to Fun and Learning
Forum Donor
Joined
Aug 14, 2019
Messages
638
Likes
759
Location
Sweden, Västerås
#13
I don't get it...

Given that real drums, in room, displace a finite amount of air, isn't there a finite membrane area that can displace the same amount of air in a linear fashion? (I know, it can never be perfectly linear etc. I mean as linear as reasonbly possible)

So is any increase in size beneficial by definision? A speaker cannot be huge enough? So if I have Wilson Chronosonics, I should strive for WAMM Master Chronosonics for significantly better bass and air displacement? and maybe add a couple of PA subwoofers on top? (I exaggerate for argument's sake, but you get the point)
I don’t think I ever heard home speakers reproduce kick drum realistically, so you ott example is not to stupid but it except that Wilson is probably hugely overrated, it seems to be possible to do this at a fraction of the cost.

In that context I can’t really understand the Uber expensive two way with one 6;5” driver that seems popular among some wealthy audiophiles its the wrong compromise for the price point and application .

Also a someone else said with larger bass driver you tend to get three way speakers or more for other reasons as it’s not feasible to cross such a large driver directly to a treble unit (unless some horn that can be crossed very low ). And then the speaker gets large and more complex .
 
OP
R
Joined
Sep 24, 2019
Messages
91
Likes
53
Location
Haifa, IL
Thread Starter #14
Wilson is probably hugely overrated, it seems to be possible to do this at a fraction of the cost.
Fine, than not Wilson. Focal Utopia vs Grande Utopia, Magico M3 vs M6, Fakespeaker Royal's Bazooka vs. Scud. Whatever. The namedropping is just for example's sake, I couldn't care less about what speaker brand it is. I'm asking about the principle.
 
OP
R
Joined
Sep 24, 2019
Messages
91
Likes
53
Location
Haifa, IL
Thread Starter #15
In that context I can’t really understand the Uber expensive two way with one 6;5” driver that seems popular among some wealthy audiophiles its the wrong compromise for the price point and application
I pretty much agree with that. Personally, I really like this kind of speaker design and think it's a great compromise for regular domestic environments.
However, lots of these are priced way up there, in the area that should be reserved for large, premium 3 ways, which undermines the whole point of this design being a compromise.
 
Last edited:

Hipper

Senior Member
Joined
Jun 16, 2019
Messages
483
Likes
378
Location
Herts., England
#16
I don't get it...

Given that real drums, in room, displace a finite amount of air, isn't there a finite membrane area that can displace the same amount of air in a linear fashion? (I know, it can never be perfectly linear etc. I mean as linear as reasonbly possible)

So is any increase in size beneficial by definision? A speaker cannot be huge enough? So if I have Wilson Chronosonics, I should strive for WAMM Master Chronosonics for significantly better bass and air displacement? and maybe add a couple of PA subwoofers on top? (I exaggerate for argument's sake, but you get the point)
Speaker drivers don't act like musical instruments. Indeed they often have to play multiple instruments at the same time including their phasing. I assume this means that at a particular moment in the music, a recording (and remember that the recording is also a compromise) of, say, a kick drum needs air to be pushed whilst some other instrument will want air to be pulled. Not only that but you don't normally play a full drum kit at full blast in a small room - it would be overpowering.

I would have thought the best solution to replicate good and low bass is to get multiple subs (and room treatment/DSP/EQ as Duke reminds us). That way we create a phantom image of the recording - the point being it is a phantom image and not a real one.

Having said that you can get a touch of chest punch from a kick drum from some recordings - I've felt on my system of slightly unconventional speakers. It seems to depend on the recording.
 
Last edited:

Frank Dernie

Major Contributor
Forum Donor
Joined
Mar 24, 2016
Messages
4,710
Likes
10,003
Location
Oxfordshire
#17
Drums come in different sizes for different frequencies...


Looks like power handing (00:37) is important too...
One of my favourite pieces of music.
The speaker needs high SPL capacity, but, as always, the recordings of different performances varies enormously, I have several, in some the bass drum is a "feature" in others not that noticeable.
A drum skin is nothing like a loudspeaker in the way it radiates, so the OP wanting some sort of equivalence is going to be disappointed.
 

Koeitje

Addicted to Fun and Learning
Joined
Oct 10, 2019
Messages
904
Likes
1,044
#18
I don't get it...

Given that real drums, in room, displace a finite amount of air, isn't there a finite membrane area that can displace the same amount of air in a linear fashion? (I know, it can never be perfectly linear etc. I mean as linear as reasonbly possible)

So is any increase in size beneficial by definision? A speaker cannot be huge enough? So if I have Wilson Chronosonics, I should strive for WAMM Master Chronosonics for significantly better bass and air displacement? and maybe add a couple of PA subwoofers on top? (I exaggerate for argument's sake, but you get the point)
PA subs generally don't play as low.
 

briskly

Active Member
Joined
Jul 10, 2019
Messages
103
Likes
131
#19
Given that real drums, in room, displace a finite amount of air, isn't there a finite membrane area that can displace the same amount of air in a linear fashion?
Your questions suggest a much more limited scope than the problem you really seem interested in. That problem does not seem to be clearly defined. It sounds like a circle of confusion problem.
In discussing the topic of bass, the thread is invoking other concepts that are distinct from bass alone: motor design, directivity, diaphragm modes, and efficiency. The response of a drum isn't limited to just the output in the bass region; it will have significant harmonics poking into the midrange.
 

tomtoo

Major Contributor
Joined
Nov 20, 2019
Messages
1,089
Likes
1,060
Location
Germany
#20
This is a hypothetical question.

Assuming that we are in a reasonable living room (not a huge mansion), and our goal is to reproduce acoustically played music (i.e. not electronic, not movies), what would be the maximum woofer membrane area in order to produce bass, above which there would be no audible difference?

For example, suppose we have about 900-1,000 cm2 of total radiating area (12'' or 3 X 6.5'' woofers give or take, times 2 speakers). We want to reproduce double bass drum kicks, a church organ, these sorts of things. At which size of membrane area does it stop mattering? 15'' drivers? 18''? 3 X 10''?

Again, I'm talking about music reproduction in a domestic room, not earthquake bass of some movies that doesn't exist in acoustic music.
A church organ can go as deep as 16hz and this with a lot of spl. Nothing for toy speakers. Not a good example.
Kick Drums have a lot of energy in the 50Hz region thats more easy.
8“ inch speakers can do 50Hz well. As long as you not want to reproduce the kick at original spl. If you like to reproduce a kick in original spl you are easaly in the region of 18" drivers.
 
Top Bottom