Hi ! i have a basic question about the main duty of speaker stands
i have search for discussion about the goals of stands design but i could not find a specific thread
Leaving aside the goal of elevating the point of emission for short speaker what is their real goal ?
is to decouple mechanically the speaker from the floor ? are floor vibrations really so intense ?
i have never felt the floor to vibrate Rarely the side walls with high SPLs at friends house
Moreover if the speaker is heavy on mass the all issue should be less critical Am i right ?
i have search for discussion about the goals of stands design but i could not find a specific thread
Leaving aside the goal of elevating the point of emission for short speaker what is their real goal ?
is to decouple mechanically the speaker from the floor ? are floor vibrations really so intense ?
i have never felt the floor to vibrate Rarely the side walls with high SPLs at friends house
Moreover if the speaker is heavy on mass the all issue should be less critical Am i right ?
It won't get much more "real" than that!
Avoiding reflective surfaces (such as furniture abused as speaker stands) below and around the speaker reduces first reflections.
hi thank you very much for the valuable advice Imho all vibrations/resonances issues should have to be dealt with at speaker level
There should not be vibes leaving the speakers
Vibes coming instead from the sorrounds should be of a much lower level of those generated by the bass drivers in the speaker
the speaker cabinet will be very substantial i.e. heavy Big inertia
There should not be vibes leaving the speakers
Vibes coming instead from the sorrounds should be of a much lower level of those generated by the bass drivers in the speaker
the speaker cabinet will be very substantial i.e. heavy Big inertia
Decoupling from the floor is not a bad goal at all ( after all the 'perfect' theorical is a floating in the air point source) but it isn't the initial goal of stand.
That said they can include this into their proposal.
Are floor ( and other wall) vibration so intense?
They can be. But it's rather the membrane area a wall can be which is an issue: even if weak, when the emmissing surface is multiple square meters then it's not negligible anymore.
Mass have an effect in that it ask for more 'power' to move. In that it approach the theorical ideal of 'floating in the air source': there is no rocking movement back/forth, side/side or up/dowb to perturbate the emmision of wave front our loudspeaker try to generate.
In other words, it help with stability of emmissive point. But it's double edged as with mass there is chance there is increase of coupling to surface hence increase of chance the walls became emmissive surface.
That's why spike are often recommended: they increase coupling by focusing the weight on small surface of contact. By such they offer a better mechanical reference and at same time limit the ability to transfer vibration as they are small contact point (eg with reference to a box/cabinet surface).
Decoupling can be achieved through other means being it by use of special materials ( like sorbothane) under box, mass/spring system under concrete slabs or even pendulum system under box or stands ( like the one used to protect building from damage generated by earthquake).
They differs ( decoupling) from typical damping in that the decoupling look alike an high Q low pass system ( there is a very high resonance at low resonance freq (sometimes with duration in the order of seconds or even minutes for very low cycle in hz like 1 hz or lower), and from there, they act as 'mechanical diode'* as you go higher in freq : les and less coupling happen - and why the target of sub 1hz resonance system frequency as once into audio territory (20hz) effect is already significant).
* of course this doesn't exist! This is just an image. 😉
That said they can include this into their proposal.
Are floor ( and other wall) vibration so intense?
They can be. But it's rather the membrane area a wall can be which is an issue: even if weak, when the emmissing surface is multiple square meters then it's not negligible anymore.
Mass have an effect in that it ask for more 'power' to move. In that it approach the theorical ideal of 'floating in the air source': there is no rocking movement back/forth, side/side or up/dowb to perturbate the emmision of wave front our loudspeaker try to generate.
In other words, it help with stability of emmissive point. But it's double edged as with mass there is chance there is increase of coupling to surface hence increase of chance the walls became emmissive surface.
That's why spike are often recommended: they increase coupling by focusing the weight on small surface of contact. By such they offer a better mechanical reference and at same time limit the ability to transfer vibration as they are small contact point (eg with reference to a box/cabinet surface).
Decoupling can be achieved through other means being it by use of special materials ( like sorbothane) under box, mass/spring system under concrete slabs or even pendulum system under box or stands ( like the one used to protect building from damage generated by earthquake).
They differs ( decoupling) from typical damping in that the decoupling look alike an high Q low pass system ( there is a very high resonance at low resonance freq (sometimes with duration in the order of seconds or even minutes for very low cycle in hz like 1 hz or lower), and from there, they act as 'mechanical diode'* as you go higher in freq : les and less coupling happen - and why the target of sub 1hz resonance system frequency as once into audio territory (20hz) effect is already significant).
* of course this doesn't exist! This is just an image. 😉
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Hi thank you for the very kind and helpful reply
I have decided to restrict the discussion to subwoofers cabinets They are by far the most critical application
The level of autogenerated vibes is high and the size of the cabinets big
I intend to segregate the big woofer in a dedicated cabinet I do not understand cheap tower speakers and the very good one weigh a ton I guess for a reson
this is extremely interesting If i understand well the sound coming out from the speaker can make a wall shake and the wall vibes can re-enter the speaker like a feed back ?
even in this case a high mass cabinet could have a higher inertia and therefore less prone to vibrate Clearly this feeedback is a bad thing because it wil be quite out of phase and time with the direct sound
unfortunately real is not ideal i know this very well
very interesting I will try them for sure After all i see them used almost everywhere also for racks They must be effective
this is more tricky to understand for me May i ask what do you use under your speakers ? i guess the decision has come after some experiments
I am leaning towards spike on a brass disk solution I will try different material
Hi Ginetto,
" sound coming out from the speaker.... re enter as feedback?"
Yes it happen but it's not the actual issue as i wanted to explain it. I will reword it:
when loudspeakers are coupled to walls, floor and ceilling, the vibrations ( even if small) are transfered to the wall which will then act as drivers by themself.
By vibrating sympatheticly ( in synchronicity) with the loudspeaker's drivers, they act as secondary drivers, blurring the wavefront you tried to initially create with your loudspeaker ( for sake of demonstration let's admit there is a single driver able to generate all frequencies at once by itself. Some kind of theorical ideal driver but not floating into the air).
In such situation your whole room will act as a driver with different time of propagation as sound travel at a speed which depend from the material it evolve into and there is chances your walls are from different material between them ( eg: concrete on floor, plasterboard for walls or ceilling, woods or metal lumber for structure,....) which will even be different than the air in which we try to propagate the vibration ( sound).
This will give different starting point for each 'secondary' driver ( walls) which will blur the transients ( first few milliseconds of a sound in which info about familly of instruments are contained / plucked or hited or bowed strings, hited membrane, reeds,...). It will too give phase anomaly as you initially though with cabinet feedback.
"High mass cabinet could have higher inertia and are less prone to vibrate".
This is deceiptive. In fact higher mass will be linked to frequency, lowering the frequency at which resonance happen, in no way it will garantee you it'll be 'less prone to vibrate'. Any material will vibrate, severity of the resonance ( what i defined as high Q previously) is linked to other things that mass.
You'll have to believe me on this as i don't feel to explain it there ( english is a foreign language to me too... 😉 ).
Let's go back to our single 'perfect theorical' driver: if you decide to make an heavy cabinet with material having resonnance at 40hz and you restrict frequency generated by the driver at 120hz, there is chance the cabinet will remain silent whatever happen with the driver ( your high pass electrical filter will limit the level of frequency prone to make cabinet vibrate to such a low level it will be under treshold of audibility ( this treshold thingy is important to remember concept).
Now think the inverse, your theorical driver will now only play freq below 120hz. Then you'll have an issue: at 40hz, there will be resonance happening, increasing the level to unkwnown level ( and for an unknown range of frequency around the center of 40hz). Here your mass doesn't change anything, there is even chance it make things worst as for the cabinet to resonate ( given there is increased mass) you'll need more power for it to happen!
A known solution to limit the resonance is to make the cabinet rigid. Extremely rigid: this will shift resonance frequency higher up in frequency. In theory if it is rigid enough to happen above reproductible freq range of loudspeaker it would render the issue inaudible ( above 20khz or higher).
But reality is that if you can even shift this above the cutoff freq of the way your driver have to reproduce it will be VERY NICE.
If we take our max freq limit of 120hz then if the box can resonate at let's say 400hz then, we are golden... this won't be achieved by mass, but by structural reinforcement, in other words: bracing.
i hope you get the idea... 😉
" sound coming out from the speaker.... re enter as feedback?"
Yes it happen but it's not the actual issue as i wanted to explain it. I will reword it:
when loudspeakers are coupled to walls, floor and ceilling, the vibrations ( even if small) are transfered to the wall which will then act as drivers by themself.
By vibrating sympatheticly ( in synchronicity) with the loudspeaker's drivers, they act as secondary drivers, blurring the wavefront you tried to initially create with your loudspeaker ( for sake of demonstration let's admit there is a single driver able to generate all frequencies at once by itself. Some kind of theorical ideal driver but not floating into the air).
In such situation your whole room will act as a driver with different time of propagation as sound travel at a speed which depend from the material it evolve into and there is chances your walls are from different material between them ( eg: concrete on floor, plasterboard for walls or ceilling, woods or metal lumber for structure,....) which will even be different than the air in which we try to propagate the vibration ( sound).
This will give different starting point for each 'secondary' driver ( walls) which will blur the transients ( first few milliseconds of a sound in which info about familly of instruments are contained / plucked or hited or bowed strings, hited membrane, reeds,...). It will too give phase anomaly as you initially though with cabinet feedback.
"High mass cabinet could have higher inertia and are less prone to vibrate".
This is deceiptive. In fact higher mass will be linked to frequency, lowering the frequency at which resonance happen, in no way it will garantee you it'll be 'less prone to vibrate'. Any material will vibrate, severity of the resonance ( what i defined as high Q previously) is linked to other things that mass.
You'll have to believe me on this as i don't feel to explain it there ( english is a foreign language to me too... 😉 ).
Let's go back to our single 'perfect theorical' driver: if you decide to make an heavy cabinet with material having resonnance at 40hz and you restrict frequency generated by the driver at 120hz, there is chance the cabinet will remain silent whatever happen with the driver ( your high pass electrical filter will limit the level of frequency prone to make cabinet vibrate to such a low level it will be under treshold of audibility ( this treshold thingy is important to remember concept).
Now think the inverse, your theorical driver will now only play freq below 120hz. Then you'll have an issue: at 40hz, there will be resonance happening, increasing the level to unkwnown level ( and for an unknown range of frequency around the center of 40hz). Here your mass doesn't change anything, there is even chance it make things worst as for the cabinet to resonate ( given there is increased mass) you'll need more power for it to happen!
A known solution to limit the resonance is to make the cabinet rigid. Extremely rigid: this will shift resonance frequency higher up in frequency. In theory if it is rigid enough to happen above reproductible freq range of loudspeaker it would render the issue inaudible ( above 20khz or higher).
But reality is that if you can even shift this above the cutoff freq of the way your driver have to reproduce it will be VERY NICE.
If we take our max freq limit of 120hz then if the box can resonate at let's say 400hz then, we are golden... this won't be achieved by mass, but by structural reinforcement, in other words: bracing.
i hope you get the idea... 😉
It's not because something is widespread that it is based on science, effectiveness and reproductibility. 😉
In fact it depend of the situation you face... sometimes spikes are the cure, sometime not.
In my experience it will depend from material used for floor: if soft ( wood) spike can help more than if hard ( ceramic tiles). In case of hard floor i prefer decoupling devices.
I've got differents pairs of loudspeakers and all are not treated the same.
My biggest one ( Mains) are 50kg each and have sorbothane decoupling to a frame they lie on and spike from frame to floor ( ceramic tiles).
My smaller Tannoy nearfield have 'regular' studio stands and are located on foam pad ( like Auralex products).
I've got other loudspeakers which do not see any particular attention to their decoupling/floor contact... as i'm either lazy or don't give a f.ck when i'm djing for example! 😉
Let's say this kind of things were part of my job when i was in charge of build of professional control rooms in recording studios. Anc i'm always curious and eager to learn things audio related anyway... 😉
hi just to understand better For me coupled means in physical contact with another body The coupling is speaker to stand and stand to floor
can we call this mechanical coupling ?
do you mean acoustical coupled ? in the sense that the air moved by the woofer makes the boundaries to vibe ?
i need to understand what coupled really means before going on
and this is clear of course
i see this is for instance when i hear wall shaking Usually with low Hz signals at high levels Not the norm with music
i wonder how can i check this resonance with a signal generator maybe ? i have to buy one soon It is a very needed instruments for speakers
i could make a sweep and listen for some resonances in the room
this is not my goal I need to make a "silent" cabinet for a driver covering from the very low to lets say 300Hz No more I am still undecided it could be even less like 150 Hz
perfectly clear Thanks !
i understand Well i will not need that much at all it will be the lower way of a 3 ways
Perfectl ! So bracing is key for bass boxes I will study the topic
I wonder if a signal generator could be to check the resonant frequency of a woofer-cabinet system If this frequency will be inside the range covered by the driver i will know that i have to make the box stiffer adding bracing
I willbuy soon a signal generator It is a must I like those with a round knob I do not know why most units now use up and down buttons
It is so nice a round knob
Ok now i know what i have to look for the cabinet Stiffness
Lets say that i have made a stiff cabinet Which kind of stand would be ideal ?
i need to elevate the cabinet of about 50cm from the floor More or less
Yes it's how it's called.
It happens too but for it to be meaningful you would need VERY HIGH SPL. Mechanical coupling is usually much higher in level and annoyance.
It's not because your senses are unaware than it doesn't happen or isn't an issue. That said once it is under treshold of audibility there is no issue to chase for. Except paranoia and OCD.
Yes it can work.
You'll have issue to separate what comes from the box and what comes from the room as is. ( both are box if you think about it!)...
It's a first step in the good direction imho. 👍
Not your goal but for understanding what is at work it help imho.
👍
Hmmm. It's not a black/white situation. As was told you in your other thread about acoustic and room mode there is different things to study and so different strategy...
You already moved from satellite/sub to 3 ways and it does change a lot of things...
50cm from floor will defacto limit your high freq range to something in the 80/100hz range max ( because of what is known as SBIR, 50cm will induce issue at 170hz and so half the freq limit seems wise imho)...
If you want to play with what SBIR is about:
http://tripp.com.au/sbir.htm
I first suggest you to read Roy Allison work to understand how room boundary interact with loudspeakers and what could be gained, issues created. It will explain why a satellite/sub is not a bad solution rather than a typical 3ways ( which could work too if you understand compromise and choices to be made...).
https://www.google.com/url?sa=t&sou...0QFnoECCAQAQ&usg=AOvVaw2TJ3NmqSr80ilMdVbA86x6
Well what loudspeaker design are all about... compromise, choices,...😉
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Hi sorry for the delay Perfect ! i understand all better now
if i can make the cabinet non resonant only the room resonances will be left I see the cabinet resonances the worst by far
no the sat/sub will be most likely a 3 ways The sub is only a woofer and above it a smaller box with mid and tw or a single fullrange maybe
one requirement is fixed The woofer will have its own cabinet
thanks i have to study it The woofer should cover up to 300Hz linear more or less
I have to study this issue Very important
i wll read it thanks a lot The reason beyond that two pieces solution is that i do not like to move around big speakers
i am pretty sure that there will be wheels below the bass cabinets
Very nice ! it is just a matter of selecting the wheels material .. some kind of plastics or rubber
it will make the positioning very easy
i am a little worried because i understand now better that the big woofers must be placed close to the floor
i remember this one Maybe it is a wrong design
was just thinking to replace the lower half of the cabinet with a 4 legs stand
all in all it is my perfect speaker concept Drivers of course can be different but i love the concept a lot Very lot
it will make the positioning very easy
i am a little worried because i understand now better that the big woofers must be placed close to the floor
i remember this one Maybe it is a wrong design
was just thinking to replace the lower half of the cabinet with a 4 legs stand
all in all it is my perfect speaker concept Drivers of course can be different but i love the concept a lot Very lot
'I'm worried because i understand now that thee big woofers must be placed close to the floor'
Well it's not as easy: there is different compromise that have to be thoughts about.
In Roy Allisson paper, he made a choice of low xover point ( 150hz or lower) which open to possibility to rely on boundary reinforcement for the better. So in that case then yes being close to floor and cut in the 100hz region is important.
In case of the ESS the 12" have to be xed over to the AMT circa 800hz. In that case driver's center to center distance might have a greater importance ( because it can enhance the sensation the 2 drivers behave as single source) than floor bounce cancelation. Maybe the fact their is a 12" passive radiator involved render the issue less important in the grand schem of things...
It's always the sum of the different choices made at design stage which matters for the outcome. And they are not always evident without a bit of reverse engineering.
Well it's not as easy: there is different compromise that have to be thoughts about.
In Roy Allisson paper, he made a choice of low xover point ( 150hz or lower) which open to possibility to rely on boundary reinforcement for the better. So in that case then yes being close to floor and cut in the 100hz region is important.
In case of the ESS the 12" have to be xed over to the AMT circa 800hz. In that case driver's center to center distance might have a greater importance ( because it can enhance the sensation the 2 drivers behave as single source) than floor bounce cancelation. Maybe the fact their is a 12" passive radiator involved render the issue less important in the grand schem of things...
It's always the sum of the different choices made at design stage which matters for the outcome. And they are not always evident without a bit of reverse engineering.
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Hi thanks again It will not be my case I like hugely the ESS concept
yes i think that this is much more important to me If i had a pair of great 12" coaxials those and this ESS cabinet would be the end of the game
but 12" great coaxial are very expensive indeed I will try different solution for the head The choice is immense The xover point could be much lower than 800Hz
i do not understand the passive solution and what kind of benefits it could provide A very complex solution I will skip on it
I see and thank you for the helpful advice These days people tend to prefer tower speakers I dont I like these ESS form factor
Very elegant and good looking I would please even to get only the empty boxes Love the way are built A 50 years old design