About the ratio between cabinet mass and driver moving mass

[gino1961]

Good morning everyone
First of all i declare my ignorance on the subject
Anyway ... i was watching a video on youtube and i heard something that shocked me profoundly
The video is here

the point in question is mentioned at 14:00 and on
After hearing this speech I'm very interested in this ratio between the cabinet mass and the moving mass of a woofer (which is obviously the most critical component having a very high moving mass compared to the other drivers)
Obviously when instead of an open baffle what we consider is a traditional loudspeaker the total mass is the sum of the masses of all the panels (if the walls are rigidly connected together)
I would like to read some opinions on this subject which is extremely interesting to me Very interesting indedd
Some year ago with a friend with some risks for our health we glued some lead slabs on the internal sides of two speakers
We were sincerely amazed how the speakers reproduced the bass frequencies after that mod ... i had never heard a better Bach's Toccata e fuga from my speakers before
Very unfortunately lead is highly toxic If not it would be a God gift to increase speakers mass. Cheap and very high density
Thank you and many greetings to all, gino

 

[René - Acculution.com]

Good morning everyone
First of all i declare my ignorance on the subject
Anyway ... i was watching a video on youtube and i heard something that shocked me profoundly
The video is here

the point in question is mentioned at 14:00 and on
After hearing this speech I'm very interested in this ratio between the cabinet mass and the moving mass of a woofer (which is obviously the most critical component having a very high moving mass compared to the other drivers)
Obviously when instead of an open baffle what we consider is a traditional loudspeaker the total mass is the sum of the masses of all the panels (if the walls are rigidly connected together)
I would like to read some opinions on this subject which is extremely interesting to me Very interesting indedd
Some year ago with a friend with some risks for our health we glued some lead slabs on the internal sides of two speakers
We were sincerely amazed how the speakers reproduced the bass frequencies after that mod ... i had never heard a better Bach's Toccata e fuga from my speakers before
Very unfortunately lead is highly toxic If not it would be a God gift to increase speakers mass. Cheap and very high density
Thank you and many greetings to all, gino

When modelling loudspeakers we initially ignore the mass that is moving due to reaction forces. For many other products this may be too crude of an approximation. I showed in a recent audioXpress article how you can include such a housing mass for a loudspeaker and a balanced armature receiver and it affects the resonance frequency. And as you mention one should really also consider more than that as the enclosure is not rigid.

 

[RDoc]

Good morning everyone
First of all i declare my ignorance on the subject
Anyway ... i was watching a video on youtube and i heard something that shocked me profoundly
The video is here

the point in question is mentioned at 14:00 and on
After hearing this speech I'm very interested in this ratio between the cabinet mass and the moving mass of a woofer (which is obviously the most critical component having a very high moving mass compared to the other drivers)
Obviously when instead of an open baffle what we consider is a traditional loudspeaker the total mass is the sum of the masses of all the panels (if the walls are rigidly connected together)
I would like to read some opinions on this subject which is extremely interesting to me Very interesting indedd
Some year ago with a friend with some risks for our health we glued some lead slabs on the internal sides of two speakers
We were sincerely amazed how the speakers reproduced the bass frequencies after that mod ... i had never heard a better Bach's Toccata e fuga from my speakers before
Very unfortunately lead is highly toxic If not it would be a God gift to increase speakers mass. Cheap and very high density
Thank you and many greetings to all, gino

I'd think the real question is not the mass of the enclosure but its rigidity and damping unless the motion of the voice coil is vibrating the enclosure due to f=ma reaction which seems unlikely. Adding something like lead sheets to the cabinet enclosure would increase both the rigidity and damping.

 

[gino1961]

When modelling loudspeakers we initially ignore the mass that is moving due to reaction forces. For many other products this may be too crude of an approximation. I showed in a recent audioXpress article how you can include such a housing mass for a loudspeaker and a balanced armature receiver and it affects the resonance frequency. And as you mention one should really also consider more than that as the enclosure is not rigid.

HI thank you for the very kind and valuable reply
Do you mean that the reaction forces due to the moving mass are so low to be ignored?
I am quite ignorant but i guess that below a certain moving mass and above certain frequency reaction forces are not an issue
My biggest problem is the big woofer at the point that i am studying subwoofers design to try to understand a little
I really don't know if high cabinet mass is the key or stiffness is more important for no boxyness

 

[gino1961]

I'd think the real question is not the mass of the enclosure but its rigidity and damping unless the motion of the voice coil is vibrating the enclosure due to f=ma reaction which seems unlikely. Adding something like lead sheets to the cabinet enclosure would increase both the rigidity and damping.

HI thanks a lot for the very helpful advice
Unfortunately lead is very toxic and I am worried for this
Not the most rigid material
Very high end speakers use aluminum for enclosure panels and extensive bracing
I used lead in some DIY experiments and i felt a cleaner sound for instance listening pipe organ tracks
High stiffness material are usually difficult to work and expensive
Almost everyone use mdf with internal bracing
Another idea could be to brace mdf with steel profiles? Never seen that by the way

 

[Thomas_A]

1:1000 should be enough. What is important is not to have resonances in the audible range, which can multiply movement.

 

[René - Acculution.com]

HI thank you for the very kind and valuable reply
Do you mean that the reaction forces due to the moving mass are so low to be ignored?
I am quite ignorant but i guess that below a certain moving mass and above certain frequency reaction forces are not an issue
My biggest problem is the big woofer at the point that i am studying subwoofers design to try to understand a little
I really don't know if high cabinet mass is the key or stiffness is more important for no boxyness

The reaction force is the same as what moves the cone and such the opposite direction but the enclosure is much heavier so the acceleration is lower. But then comes more complications as torques and stiffness and modes and the pressure moving the walls. Just try and make it as heavy and stiff as makes sense to you.

 

[gino1961]

1:1000 should be enough. What is important is not to have resonances in the audible range, which can multiply movement.

Hi i checked some values for big woofers moving mass
They range around 50 grams that makes 50 kg for the cabinet
I guess that resonances should result in peaks in the frequency response?