Why is decoupling necessary?

[HSLand]

I once had my monitors on a work desk and used some MoPads to decouple them. Then I switched to monitor stands filled with sand. So recently I bought a new desk and I've got to set my monitors on the desk itself.

My question is, why is it so important to decouple your monitors from the desk? I understand that it'll get rid of the desk vibration and it'll give you a clearer perspective of what's actually coming out of your speakers, but the way I look at it is that most people are going to be listening to music in very imperfect conditions anyway, so as long as you're aware that you're hearing a bit more bass than usual, what's the problem?

I think it can only help with bass in the mix because the more you're hearing, the less you'll put, and more often than not there's too much rather than not enough.

I want to try decoupling Vs. not decoupling... but I'm not sure it's worth it to buy those Primacoustic Recoil Stabilizers for $200 a pair for what you get in return.

[tallpaul]

there are cheaper ways to decouple your monitors than those fancifully named products. four hockey pucks (vulcanized rubber) under each speaker would be a cheap option to try. you could look at the Townshend seismic sink principle. this uses a compliant bladder (an inflated inner-tube from something like an electric wheelchair) filled with air underneath a large mass to decouple the speaker. a marble-sized blob of Blu Tac under each corner of the speaker is something else that you could try. silica gel squares under each corner is another option. plenty of cheap options. try a few and find the one which sounds best would be my advice.

[localhost127]

Originally Posted by tallpaul

there are cheaper ways to decouple your monitors than those fancifully named products. four hockey pucks (vulcanized rubber) under each speaker would be a cheap option to try. you could look at the Townshend seismic sink principle. this uses a compliant bladder (an inflated inner-tube from something like an electric wheelchair) filled with air underneath a large mass to decouple the speaker. a marble-sized blob of Blu Tac under each corner of the speaker is something else that you could try. silica gel squares under each corner is another option. plenty of cheap options. try a few and find the one which sounds best would be my advice.

sorbothane.

[tallpaul]

Originally Posted by localhost127

sorbothane.

try that as well...

[RScott]

As mentioned, plenty of ways to decouple on the cheap.

As far as the notion of "end user will be listening in imperfect conditions, why not mix in them?" the problem is that you won't be mixing in the same imperfect conditions. If you made a mix in someone's living room, that mix will sound good in their living room. But you want to make a mix to sound good in everyone's living room, and car, and ipod headset etc. In the end the best thing is to have a standard and mix as close as you can to the standard and then cross check on various systems.

Take care of the decoupling and other things on the cheap so that you have money left over to spend on other, possibly more significant problem zones (or pocket the savings).

[tallpaul]

+1. concisely and wisely put.

Originally Posted by RScott

As mentioned, plenty of ways to decouple on the cheap.

As far as the notion of "end user will be listening in imperfect conditions, why not mix in them?" the problem is that you won't be mixing in the same imperfect conditions. If you made a mix in someone's living room, that mix will sound good in their living room. But you want to make a mix to sound good in everyone's living room, and car, and ipod headset etc. In the end the best thing is to have a standard and mix as close as you can to the standard and then cross check on various systems.

Take care of the decoupling and other things on the cheap so that you have money left over to spend on other, possibly more significant problem zones (or pocket the savings).

[boggy]

Originally Posted by HSLand

....
My question is, why is it so important to decouple your monitors from the desk? I understand that it'll get rid of the desk vibration and it'll give you a clearer perspective of what's actually coming out of your speakers, but the way I look at it is that most people are going to be listening to music in very imperfect conditions anyway, so as long as you're aware that you're hearing a bit more bass than usual, what's the problem?

Loudspeaker cones move forth and back, so they introduce vibrations that is transferred to cabinet. If decoupling isn't applied properly, this vibrations translate to desk (stand) and through desk legs, to floor and to wall. All of this extra surfaces are much larger than cone of loudspeaker, so even if loudspeaker induce very small amount of vibrations, large surface of desk, floor and wall amplify air movement, and may cause influence to direct sound in absolutely unpredictable direction, so we may call it colourations, without hesitation.

Originally Posted by HSLand

I think it can only help with bass in the mix because the more you're hearing, the less you'll put, and more often than not there's too much rather than not enough.

Main target of acoustics treatment in studio is controlling of what listener hear, so we don't need more or less bass, we need absolutely right amount of all frequencies transferred to listener in some acceptable way to enable him/her to achieve good mix translation with smaller possible effort and frustration.

Originally Posted by HSLand

I want to try decoupling Vs. not decoupling... but I'm not sure it's worth it to buy those Primacoustic Recoil Stabilizers for $200 a pair for what you get in return.

Try it, why not?
Sure or not... good acoustic treatment enable listener to hear something that cannot be possible to hear before treatment. So if you don't hear difference with or without decoupling, you don't need it (for now, at least).

[avare]

Originally Posted by RScott

As far as the notion of "end user will be listening in imperfect conditions, why not mix in them?" the problem is that you won't be mixing in the same imperfect conditions. If you made a mix in someone's living room, that mix will sound good in their living room. But you want to make a mix to sound good in everyone's living room, and car, and ipod headset etc.

+1, with no additional vibrations.

Solidly,
Andre

[darkbuddha]

I'll just add a really fundamental idea (completely inline with what others have said), but if it's not mixed the way you want it, the end user can't and won't hear what you want them to hear, no matter how well it translates to others' systems/environments. If you mix in imperfect conditions, how can you expect for them to have a chance at getting the mix you intend? Basically, if the end user's system doesn't translate the mix well, that's on them; if you mix it poorly, that's on you.

[DanDan]

As a Mix engineer, my primary goal for years was to persuade mixes to sound the same everywhere. I would check the mix on three diverse systems every time. Back to studio, tweak the mix, then back to the three wise men again.
This was tedious and one couldn't sign off on the mix until done. No recall.
It works though. Try Fat Valley of Pain on Mary Black's 'No Frontiers' CD
It will sound very much the same on everything.

Obviously there is nothing new or revolutionary about this notion.
I formed it from admiration of the work of one of my great heroes. The late Alex Sadkin. 'Pull up to the bumper' Grace Jones, sounds the same over the phone as it does in a Disco (80's dancing place kids!)

DD

[John Suitcase]

I have a question on this point. It seems that a lot of the decoupling solutions sold (or DIY ones) do a fine job of eliminating or greatly reducing at least, the transfer of vibrations from the cabinet to the desk. But it seems to me that they increase the ease with which the cabinet itself can vibrate. Wouldn't you want the cabinet to be as solidly anchored as possible to remove any possibility of the bass driver moving the cab back and forth, both reducing the impact of those low frequencies, and modulating the highs in a doppler-effect way?

I suppose something like the Recoil units, if heavy enough, could minimize that effect for smaller speakers.

Is this not a consideration? I don't see it mentioned often, maybe I'm way off base...

[jwl]

Originally Posted by RScott

As far as the notion of "end user will be listening in imperfect conditions, why not mix in them?" the problem is that you won't be mixing in the same imperfect conditions. If you made a mix in someone's living room, that mix will sound good in their living room. But you want to make a mix to sound good in everyone's living room, and car, and ipod headset etc.

Completely agree. To me this is like a painter thinking, "hmm, some of the people that look at this will be colorblind, so I might as well paint in the dark."

[Ethan Winer]

You got plenty of explanations about desk vibration, so I'll address only this:

Originally Posted by HSLand

most people are going to be listening to music in very imperfect conditions anyway, so as long as you're aware that you're hearing a bit more bass than usual, what's the problem?

If you create a mix that sounds good in your room, which has its own particular frequency response, it’s likely to sound very different in other rooms. For example, if your room lacks deep bass, your mixes will probably contain too much bass as you incorrectly compensate for what you hear. And if someone plays your music in a room that has too much deep bass, the mixing error will be exaggerated and they’ll hear way too much deep bass. Therefore, the only practical solution is to make your room as accurate and neutral as possible, so any variation others experience is due solely to the response of their own room and system.

--Ethan

The Acoustic Treatment Experts

[boggy]

Originally Posted by John Suitcase

I have a question on this point. It seems that a lot of the decoupling solutions sold (or DIY ones) do a fine job of eliminating or greatly reducing at least, the transfer of vibrations from the cabinet to the desk. But it seems to me that they increase the ease with which the cabinet itself can vibrate. Wouldn't you want the cabinet to be as solidly anchored as possible to remove any possibility of the bass driver moving the cab back and forth, both reducing the impact of those low frequencies, and modulating the highs in a doppler-effect way?

Good question!
First, it is not that bad if only loudspeaker cabinet vibrate, it have smaller surface (... ok, it vibrate more because this... but who cares )
Second, loudspeaker's own cabinet vibrations are a part of loudspeaker design, so there are some solutions for minimizing this behavior. If loudspeaker resonate too much, it can be replaced with loudspeaker with better design..
Third, loudspeaker can be anchored to a extremely heavy concrete block and that may be a solution, but not very practical one.
[Fourth, Doppler modulation is more pronounced in mid range because midwoofer cone excursions (two way designs). Loudspeaker cabinet vibrations is much much smaller than midwoofer cone movements.]*

Originally Posted by John Suitcase

I suppose something like the Recoil units, if heavy enough, could minimize that effect for smaller speakers.

Main point is decoupling loudspeaker from (not too heavy) large surfaces which can vibrate in non predictable way (causing colorations)

Originally Posted by John Suitcase

Is this not a consideration? I don't see it mentioned often, maybe I'm way off base...

Of course that it is a consideration, but it is not very practical, as I already said.

* [edited later]

[tallpaul]

a tweak, especially with lower price monitors and the inferior cabinet construction, is to put a weight on top of the speaker. anything iron needing some sort of shielding enclosing it. i used gym weights in the past wrapped in pvc free clingfilm. subtle differences are hard to hear in a poorly sounding room, though.

Originally Posted by John Suitcase

I have a question on this point. It seems that a lot of the decoupling solutions sold (or DIY ones) do a fine job of eliminating or greatly reducing at least, the transfer of vibrations from the cabinet to the desk. But it seems to me that they increase the ease with which the cabinet itself can vibrate. Wouldn't you want the cabinet to be as solidly anchored as possible to remove any possibility of the bass driver moving the cab back and forth, both reducing the impact of those low frequencies, and modulating the highs in a doppler-effect way?

I suppose something like the Recoil units, if heavy enough, could minimize that effect for smaller speakers.

Is this not a consideration? I don't see it mentioned often, maybe I'm way off base...

[avare]

Originally Posted by tallpaul

a tweak, especially with lower price monitors and the inferior cabinet construction, is to put a weight on top of the speaker. anything iron needing some sort of shielding enclosing it. i used gym weights in the past wrapped in pvc free clingfilm. subtle differences are hard to hear in a poorly sounding room, though.

Why do you write "especially lower priced monitors?" The same technique was used Galaxy Studios with Genelec 1035s.

Andre

[tallpaul]

but not on B&W 802Ds! my experience with monitors is that costs are cut in the cabinetry of lower priced models. i wasn't aware that genelecs benefited but know that in a well designed room, tweaks can be heard (if they are not urban myth!) and the better the signal path, the more detail there is to be heard.

Originally Posted by avare

Why do you write "especially lower priced monitors?" The same technique was used Galaxy Studios with Genelec 1035s.

Andre

[boggy]

Originally Posted by tallpaul

but not on B&W 802Ds! my experience with monitors is that costs are cut in the cabinetry of lower priced models....

It is not only cut for less material, it is also because transport costs.
Custom loudspeakers I recently designed (shown here) weight about 125kg (for two cabinets, amplifiers, external DSP crossover, cables)...
loudspeaker alone weight about 43kg, and it is decoupled, from other construction, with custom rubber vibration absorbers, mechanical resonant frequency is about 3Hz.

[DanDan]

If a speaker is decoupled on say Sorbothane or Foam, doesn't this allow back and forward reaction opposite to the cone?
If the cabinet is not lossy ( Some notable speaker boxes were designed to radiate, Spendor BC1) wouldn't it be best to bond it to a massive stand. e.g. BlueTac it to a Concrete stand? In case there is LF transmission by conduction, this massive stand could then be decoupled from the floor with a layer of something. Just musing. There seems to be a lot of contradiction in the mounting of speakers. e.g. What's with spikes?
DD

[boggy]

Originally Posted by DanDan

..... What's with spikes?
DD

Spikes aren't vibration absorbers.

[DanDan]

Exactly Boggy. What is their purpose?
DD

[boggy]

Originally Posted by DanDan

Exactly Boggy. What is their purpose?
DD

Better look. They looks very elegant IMHO.

[DanDan]

I see now why we are called Slutz!
DD

[boggy]

Originally Posted by DanDan

If a speaker is decoupled on say Sorbothane or Foam, doesn't this allow back and forward reaction opposite to the cone?
If the cabinet is not lossy ( Some notable speaker boxes were designed to radiate, Spendor BC1) wouldn't it be best to bond it to a massive stand. e.g. BlueTac it to a Concrete stand? In case there is LF transmission by conduction, this massive stand could then be decoupled from the floor with a layer of something. Just musing......
DD

There are two sources of cabinet vibrations:

1. one from changes of internal pressure, and because sides of cabinet aren't ideally stiff, they vibrate as pressure change in the box. Sealed box designs suffer slightly more because this, than ported designs. This is a reason why we need cabinets which have "dead" sides in regards to pressure induced vibrations. Baffles are usually thick.
2. Second is because cone movement and third Newton law. So if we move loudspeaker cone with mass m1, forth, using acceleration a1, loudspeaker cabinet will move back using acceleration a2 =a1*m1/m2, where m2 is mass of cabinet. So if mass of cone is about 170g, acceleration of cabinet will be about 250 times smaller than acceleration of cone. This is very simplified model, of course, there are more parts in path, before vibrations are coupled to the box (they are recived to the magnet, then transferred to the front baffle through loudspeaker frame/basket... etc)

[tallpaul]

vibration coming from speakers and other sources and how this can effect jitter has been investigated, CD/DVD: Vibration and Jitter effects on Optical Disc Player and ROM Drives, for example. i have tried different methods of isolating my few pieces of equipment with audible differences. those differences went from the obvious to maybe psychoacoustic. experimenting with different materials which are inexpensive has been interesting.

[boggy]

Originally Posted by tallpaul

vibration coming from speakers and other sources and how this can effect jitter has been investigated, ....

Quartz crystals in oscillators (they are common in DACs, ADCs) are pretty sensitive to vibrations, so they really can induce jitter (unwanted phase modulation of clock signal).

[John Suitcase]

I recorded a band recently that was so loud my hard drive kept reporting that it was 'recording too many track's!' The solution was to put the HD into a case I have that has some foam cushioning to reduce the vibrations.


Of course my audio interface was being vibrated just as violently. I have to say that I can't hear any deleterious effects on the tracks, though. There may be some subtle distortion or what have you, but the band can be described as 'distortion, with screaming and drums.' So no matter!

[tallpaul]

exactly. decoupling of these units is important if jitter is of concern.

Originally Posted by boggy

Quartz crystals in oscillators (they are common in DACs, ADCs) are pretty sensitive to vibrations, so they really can induce jitter (unwanted phase modulation of clock signal).

[BriHar]

FWIW,
In many older studios, the monitors were often suspended from the ceiling or wall instead of supported on stands. Chains would usually be used for this often with a spring or other type of decoupling.