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Happy new year to all!
Reading the article on the interview with David Smith got me intrigued especially what he said about cabinet construction.
"I’ve spent a bit of my career in architectural acoustics and come to have a much better understanding of cabinet performance by looking at the architectural parallels. A great deal of work has gone into building and measuring walls assemblies to try and keep your neighbor’s noise out of your side of the world. This is really what we want to achieve with loudspeaker cabinets. We want sound from the back side of the speaker to stay in the box. In architectural terms we want the Transmission Loss to be high.
Now energy loss through the cabinet walls isn’t the problem so much as that it isn’t a uniform loss. Every cabinet wall will have numerous panel resonances and at those resonances the panels become essentially transparent. As this is a narrow band phenomenon it will have a long time signature and can have an audible effect out of proportion to its energy level.
Cabinet construction frequently gets to the heart of audiophile beliefs and common misunderstandings. In audiophile circles, if a little wall thickness is good then a lot is always better. The physics are actually at odds with that. We need to lower the Q of cabinet resonances and higher mass or higher rigidity diminish the effect of any damping we apply. Damping is the key and we want a high ratio of damping material to wall mass or rigidity. The upshot is that thicker cabinet walls will always raise the Q of resonances and make their damping harder to achieve. Raising the resonance frequencies with more rigid walls will seldom get them above audibility, more likely they will just move into a range where they are more audible. This is at odds with many audiophiles understanding so it tends to lead to spirited arguments on the forums, but the physics is clear.
"In audiophile circles, if a little wall thickness is good then a lot is always better. The physics are actually at odds with that"
Much of the understanding on this topic comes from the BBC research, especially of Harwood. This brings us around full circle so it is worth discussing. You asked about professional products and their influence. In the 60s and 70s the BBC found that with studio monitors, commercial offerings were inadequate and so they felt the need to design their own. These were very pure, purposeful designs. The brief was to create a range of monitor systems by focusing primarily on neutrality over all else. The BBC knew that the music mixing process is fundamentally about taking your microphone feeds and using all the tools at your disposal (equalization) to create a product that has a very particular sound that you want to achieve. Now you are judging that sound via a pair of studio monitors that are not directly in the recording chain. In truth, if those monitors are colored you end up incorporating the inverse of their personality into your mix. That is, if the speakers are bright you will unwittingly make the mix dull to compensate."
I did some more reading on the construction of the BBC monitors particularly the LS 5/9 monitor speaker and then reading from the Harbeth site about their cabinet making.
What do you gentlemen/women make out of this...should we be then be making thin walled cabinets with visco-elastic dampening instead of thick MDF walls with bracing? Seems like according to this, bracing and thicker walls, at least the way we commonly see in here is a useless endeavor?
Reading the article on the interview with David Smith got me intrigued especially what he said about cabinet construction.
"I’ve spent a bit of my career in architectural acoustics and come to have a much better understanding of cabinet performance by looking at the architectural parallels. A great deal of work has gone into building and measuring walls assemblies to try and keep your neighbor’s noise out of your side of the world. This is really what we want to achieve with loudspeaker cabinets. We want sound from the back side of the speaker to stay in the box. In architectural terms we want the Transmission Loss to be high.
Now energy loss through the cabinet walls isn’t the problem so much as that it isn’t a uniform loss. Every cabinet wall will have numerous panel resonances and at those resonances the panels become essentially transparent. As this is a narrow band phenomenon it will have a long time signature and can have an audible effect out of proportion to its energy level.
Cabinet construction frequently gets to the heart of audiophile beliefs and common misunderstandings. In audiophile circles, if a little wall thickness is good then a lot is always better. The physics are actually at odds with that. We need to lower the Q of cabinet resonances and higher mass or higher rigidity diminish the effect of any damping we apply. Damping is the key and we want a high ratio of damping material to wall mass or rigidity. The upshot is that thicker cabinet walls will always raise the Q of resonances and make their damping harder to achieve. Raising the resonance frequencies with more rigid walls will seldom get them above audibility, more likely they will just move into a range where they are more audible. This is at odds with many audiophiles understanding so it tends to lead to spirited arguments on the forums, but the physics is clear.
"In audiophile circles, if a little wall thickness is good then a lot is always better. The physics are actually at odds with that"
Much of the understanding on this topic comes from the BBC research, especially of Harwood. This brings us around full circle so it is worth discussing. You asked about professional products and their influence. In the 60s and 70s the BBC found that with studio monitors, commercial offerings were inadequate and so they felt the need to design their own. These were very pure, purposeful designs. The brief was to create a range of monitor systems by focusing primarily on neutrality over all else. The BBC knew that the music mixing process is fundamentally about taking your microphone feeds and using all the tools at your disposal (equalization) to create a product that has a very particular sound that you want to achieve. Now you are judging that sound via a pair of studio monitors that are not directly in the recording chain. In truth, if those monitors are colored you end up incorporating the inverse of their personality into your mix. That is, if the speakers are bright you will unwittingly make the mix dull to compensate."
I did some more reading on the construction of the BBC monitors particularly the LS 5/9 monitor speaker and then reading from the Harbeth site about their cabinet making.
What do you gentlemen/women make out of this...should we be then be making thin walled cabinets with visco-elastic dampening instead of thick MDF walls with bracing? Seems like according to this, bracing and thicker walls, at least the way we commonly see in here is a useless endeavor?
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