Driver surface vs room volume

[ppataki]

I wonder if this topic has been discussed here before; I would be very interested to hear your comments Fellow ASR Members

When we design our DIY speakers we can see how big the surface area of the cone is since it is part of the T/S parameters (namely the Sd parameter)
We also have another parameter, Vd that tells us how much air will be moved when reaching the Xmax (Vd = Sd * Xmax) aka. air displacement

For example here is how this looks like for my MCLA speakers:

My room has a volume of 67 m3

In my personal experience the bigger the driver surface is the better we can 'feel' the instruments; it provides better sense of 'being there'

Now the question is: is there a recommended minimum/optimum/maximum (?) ratio between driver surface or driver air displacement and room volume?
Or is this total nonsense?

Any comments/experience would be appreciated

 

[Digby]

as large as WAF will allow.

 

[DVDdoug]

You'd need to know the desired SPL level (at the lowest frequency of interest) and then you could make a calculation. But there will be uncertainly and room absorption and reflection and standing waves.

 

[ppataki]

@DVDdoug let's say 85dB - can you please specify how the calculation would look like? (even if it is a rough estimate only - I guess it would be better than nothing)
Thank you

 

[Digby]

I think there is more to it than SPL, probably dispersion characteristics (of large speakers) and horn efficiency. There is something to the "direct" quality of large (say 12"/15" bass driver) speakers that can't be replicated even at dB levels where smaller speakers aren't struggling, this is probably because of directivity to low frequencies, among other things.

 

[Digital_Thor]

There's another factor too. The room is going to act different, depending on what it's build off and how it connects to other rooms. So I have a 45-50 sqm living room, that is open towards my entrance. I have almost no hard walls of concrete or brick. So some energy will get lost in the constructions of the building itself.
But above all this, I always found enjoyment in smaller drivers for stereo image and big drivers for thunderous low frequencies - also for music.
I change two of my four subwoofers from 12" to 15" and enjoyed a wonderful physique arise with most music, even at low volume. My theory is, that bigger drivers are able to move the air with much more realism, whereas smaller drivers only gives an illusion of doing that. Hence - bigger drivers - when used right of course - will give you a more subversive experience - IMO.
And I do have to emphasize, that I do NOT mean boom-box bass or exaggerated bass. I have very even bass response and simply wish and enjoy hearing the full potential of all types of music. I tried it in many rooms, at friends, who also have bigger drivers in their systems (all different types of systems and rooms). And I can only say - it works better than smaller drivers - every time

 

[ppataki]

There's another factor too. The room is going to act different, depending on what it's build off and how it connects to other rooms. So I have a 45-50 sqm living room, that is open towards my entrance. I have almost no hard walls of concrete or brick. So some energy will get lost in the constructions of the building itself.
But above all this, I always found enjoyment in smaller drivers for stereo image and big drivers for thunderous low frequencies - also for music.
I change two of my four subwoofers from 12" to 15" and enjoyed a wonderful physique arise with most music, even at low volume. My theory is, that bigger drivers are able to move the air with much more realism, whereas smaller drivers only gives an illusion of doing that. Hence - bigger drivers - when used right of course - will give you a more subversive experience - IMO.
And I do have to emphasize, that I do NOT mean boom-box bass or exaggerated bass. I have very even bass response and simply wish and enjoy hearing the full potential of all types of music. I tried it in many rooms, at friends, who also have bigger drivers in their systems (all different types of systems and rooms). And I can only say - it works better than smaller drivers - every time

That is also my ultimate experience: you cannot have a big enough driver surface

 

[Koeitje]

@DVDdoug let's say 85dB - can you please specify how the calculation would look like? (even if it is a rough estimate only - I guess it would be better than nothing)
Thank you

85dB is really not very loud at all. I assume you mean 85dB on average, so you need to account for dynamic peaks. Which can be anywhere from 10-20dB.