Audio T Verdict
Custom Design Inert Filler provides a straightforward way to increase the mass and internal damping of compatible hollow speaker stand columns.
The material is formed from small, dense and angular particles measuring approximately 1mm to 2mm. These settle closely together inside the column, helping reduce the empty air spaces in which mechanical resonance can develop.
Adding the correct amount can make a speaker stand feel more stable and may help produce bass that sounds better defined and more precisely timed. It is not, however, a case of simply filling every available space as heavily as possible.
Custom Design specifically warns that excessive mass-loading can have a detrimental effect, particularly on bass timing and precision. The best approach is to begin with the quantity recommended for the particular stand and add more only in small, equal increments if listening tests suggest that it is beneficial.
Each Audio T product contains one sealed bag weighing approximately 1.6kg. Several bags may therefore be required for a pair of speaker stands. For example, Custom Design recommends two bags for each 610mm FS104 Signature central column, meaning four bags for a stereo pair.
This is a specialist setup accessory rather than a universal cure for poor loudspeaker performance. Correct stand height, top-plate compatibility, speaker positioning, levelling and room acoustics remain equally important.
Custom Design Inert Filler Speaker Stand Mass-Loading Material
Custom Design Inert Filler is a specialist granular material developed for mass-loading compatible hollow speaker stand columns.
It is supplied by Audio T as one individually sealed bag weighing approximately 1.6kg.
Its small angular particles are designed to settle closely together within a support column, adding mass while helping damp the hollow steel structure.
One Bag Is Supplied
The price shown on this Audio T page is for one individual bag of Custom Design Inert Filler.
It is not a complete box and may not provide enough material for a pair of stands.
- Approximate weight per bag: 1.6kg
- Check how many fillable columns each stand contains
- Check the manufacturer’s recommendation for the specific stand
- Multiply the quantity by two for a stereo pair
- Use equal quantities in the left and right stands
Why Mass-Load a Speaker Stand?
A hollow support column can store and release mechanical energy when the loudspeaker and floor excite the stand.
Adding suitable filler increases the total mass and reduces the open space inside the column. This changes the column’s resonant behaviour and can make the complete stand less prone to ringing or movement.
When correctly applied, possible benefits can include:
- Greater stand stability
- Reduced resonance within hollow columns
- Better-defined low frequencies
- More precise bass timing
- A firmer mechanical foundation for the speaker
- Reduced tendency for a lightweight stand to move
The result will depend on the stand, loudspeaker, floor, room and amount of filler used.
Dense Non-Magnetic Material
Custom Design describes Inert Filler as a very dense, non-magnetic and non-resonant material developed specifically for its speaker stand range.
It is not manufactured from steel and will not rust in the way an unprotected ferrous filling material could.
The exact material composition is not published, but its physical properties and small particle size have been selected for speaker stand mass-loading.
Angular 1mm to 2mm Particles
The individual particles measure approximately 1mm to 2mm and have irregular angular shapes.
The small size makes the filler easier to pour into compatible stand columns with relatively narrow openings.
The angular particles also settle together with fewer large voids or air pockets than a coarse filling material.
Developed for Custom Design Speaker Stands
Custom Design recommends Inert Filler for the fillable columns used throughout its speaker stand range.
Compatible designs may include:
- FS Series speaker stands
- RS Series speaker stands
- OM open-frame speaker stands
- SQ studio-monitor stands
- Custom-built Custom Design stands
- Other Custom Design supports specifically described as mass-loadable
Not every column on every stand is necessarily designed to be filled. Always follow the instructions for the specific model.
Do Not Fill an Unapproved or Sealed Section
Use Inert Filler only where the stand manufacturer provides a suitable mass-loading opening or explicitly identifies the column as fillable.
Do not drill or modify a speaker stand to create a filling opening. This could weaken the structure, damage the finish and invalidate the warranty.
General Quantity Guide
Custom Design provides a general starting recommendation of at least two bags, or approximately 3.2kg, for each 600mm fillable column where filler is not already supplied.
This is a general guide rather than a universal requirement. Different stand designs have columns with different widths, heights and internal volumes.
Some stands use one fillable central column, while larger designs may contain several fillable supports and require considerably more material.
FS104 Signature Quantity Guide
For the 610mm Custom Design FS104 Signature Speaker Stands, the manufacturer recommends two bags for each central column.
- Two bags per stand
- Approximately 3.2kg of filler per stand
- Four bags for a stereo pair
- Approximately 6.4kg for the pair
The FS104 Signature’s four smaller satellite columns are not intended to be filled.
Different Stands Need Different Quantities
A smaller or shorter column may require less than the general 600mm recommendation.
A large studio-monitor stand with several substantial columns may require considerably more.
Before ordering, check:
- The exact speaker stand model
- The number of fillable columns per stand
- The column height and internal dimensions
- Whether any filler is already supplied
- The recommended loading quantity
- Whether the recommendation applies per stand or per pair
Ask Audio T to Calculate the Quantity
Provide your local Audio T store with the stand manufacturer, model, height and number of columns.
We can help establish the appropriate starting quantity before you order several bags unnecessarily.
Listen Before Adding Filler
Custom Design recommends listening to the stands and loudspeakers before mass-loading them.
This provides a useful reference point and makes it easier to judge whether the added mass improves bass control, timing and overall balance.
Use familiar recordings containing natural bass instruments, voices and clear rhythmic information rather than assessing the change using bass quantity alone.
Begin with the Recommended Amount
Start with the quantity recommended for the specific speaker stand.
Use the same measured amount in the left and right stands so that their mass and mechanical behaviour remain consistent.
Listen again after the stands have been levelled and the speakers returned to their normal positions.
Add More in Small Increments
Where the stand design permits further loading, additional material should be added gradually.
Do not add several extra bags at once without listening between adjustments.
Small and equal changes make it easier to identify whether bass definition, timing and overall balance are improving or becoming less natural.
Avoid Overfilling
Custom Design warns that excessive mass-loading can reduce rather than improve performance.
Possible signs of overloading may include bass that sounds slow, heavy or less expressive, or a reduction in the system’s rhythmic agility.
The heaviest possible stand is not automatically the best-sounding stand.
Do Not Fill Every Column Automatically
Some open-frame Custom Design stands combine one fillable central column with several unfilled satellite supports.
Only load the columns identified by the manufacturer. Filling an unintended section could alter the stand’s design or make future servicing difficult.
How to Fill Compatible Speaker Stands
- Read the speaker stand assembly and mass-loading instructions.
- Remove the loudspeakers from the stands.
- Move the empty stands close to their final positions.
- Check that the fillable columns are dry, clean and correctly assembled.
- Measure the same quantity for the left and right stands.
- Use a clean, dry funnel if the filling opening is narrow.
- Pour slowly to reduce spills and airborne particles.
- Pause occasionally to allow the material to settle.
- Do not compact the material aggressively unless instructed.
- Secure the filling cap or column seal correctly.
- Level the stands before replacing the loudspeakers.
- Check all speaker cables and stand fixings.
- Listen before deciding whether further filler is required.
Use a Clean and Dry Funnel
A small funnel can make the filler easier to apply and reduce the risk of material entering threaded fixing holes or becoming trapped beneath the column seal.
The funnel and stand column should be completely dry.
Do not introduce water, oil, cleaning fluid or another filling material into the column.
Allow the Material to Settle Naturally
Pour the filler gradually and allow it to settle under its own weight.
Lightly tapping the outside of the column may help the small particles settle, but avoid striking or scratching the painted surface.
Do not hammer, mechanically compact or place excessive pressure on the filler.
Seal the Column Securely
Refit the filling cap, top plate or specified column seal after loading.
A loose cap can allow material to escape when the stand is moved or turned during final assembly.
Check that no particles are trapped within the fixing threads before tightening the stand.
Move the Stands Before Filling Where Possible
Adding four bags to a pair of FS104 Signature stands increases their combined weight by approximately 6.4kg.
Larger stands can gain substantially more weight.
Place the empty stands near their final listening positions before filling them and remove the loudspeakers whenever the stands must be moved.
Lift Rather Than Drag
Do not drag a filled stand across the floor.
Dragging can damage the floor, loosen the spikes, strain the stand structure and make the heavy stand unstable.
Keep Left and Right Loading Equal
Use equal quantities of filler in corresponding columns on the left and right stands.
A kitchen or parcel scale can help divide material accurately where a partial bag is being used.
Keep a written record of how many complete bags or measured quantities have been added to each stand.
Handling and Storage
Keep unopened bags sealed and store them in a dry location until required.
Follow any handling guidance printed on the product packaging.
When applying the filler:
- Work in a well-ventilated area
- Pour slowly to minimise spills and airborne particles
- Avoid contact with eyes
- Avoid breathing dust or fine particles
- Wash your hands after handling
- Keep the material away from children and pets
- Do not ingest the material
- Clean up spills before replacing the loudspeaker
Packaging
Each approximately 1.6kg quantity is supplied in its own sealed bag.
Custom Design states that the packaging is manufactured using 76% recycled material and is fully recyclable, subject to local recycling facilities.
The individual bags make it easier to calculate and divide the required quantity between a pair of stands.
Inert Filler or Atabites?
Custom Design Inert Filler
- Developed for compatible Custom Design stands
- Approximately 1.6kg per bag
- Small 1mm to 2mm particles
- Non-magnetic material
- Not manufactured from steel
- Sold by Audio T as individual bags
Atacama Atabites
- Developed principally for compatible Atacama stands
- Supplied in a larger container
- Metal particle construction
- Different loading quantities and particle properties
- Should be used according to Atacama’s instructions
Use the filling material recommended by the speaker stand manufacturer rather than assuming that different products are directly interchangeable.
Audio T also stocks Atacama Atabites for compatible Atacama and other suitable stands.
Mass-Loading Is Only Part of Speaker Stand Setup
Filler cannot compensate for a stand that is the wrong height, too small for the cabinet or positioned poorly in the room.
For the best result, also check:
- Top-plate dimensions
- Speaker cabinet stability
- Tweeter height
- Stand levelling
- Floor spikes or hard-floor protection
- Speaker spacing
- Distance from rear and side walls
- Toe-in towards the listening position
- Speaker cable routing
- Room reflections and bass behaviour
Compatible Custom Design Products and Audio T Guides
Key Features
- Specialist speaker stand mass-loading material
- Sold as one individual bag
- Approximately 1.6kg per bag
- Very dense granular construction
- Approximately 1mm to 2mm particle size
- Angular particle shape
- Designed to reduce large internal voids
- Non-magnetic material
- Non-resonant material
- Not manufactured from steel
- Will not rust
- Designed for compatible Custom Design stands
- Suitable for approved hollow support columns
- Adds mass to speaker stands
- Helps damp hollow column resonance
- May improve bass control
- May improve bass timing and precision
- Easy-to-apply small particle size
- Individually sealed packaging
- Approximately 3.2kg general guide per 600mm column
- Two bags recommended per 610mm FS104 central column
- Four bags recommended per pair of 610mm FS104 stands
- Can be added in controlled increments
- Equal left and right loading recommended
- Overloading is not recommended
- Packaging uses recycled material
- Packaging described as recyclable
Frequently Asked Questions
How much Inert Filler is included?
One sealed bag weighing approximately 1.6kg is supplied.
Is the price for one bag or a complete box?
The Audio T price is for one individual bag.
What is Custom Design Inert Filler?
It is a dense, non-magnetic granular material developed for mass-loading compatible speaker stand columns.
What size are the particles?
Custom Design specifies an approximate particle size of 1mm to 2mm.
Is it made from steel?
No. Custom Design states that it is not manufactured from steel.
Will it rust?
Custom Design states that the material will not rust.
What does mass-loading do?
It increases stand mass and helps damp resonance within a compatible hollow support column.
Will it definitely improve my speakers?
Not every stand and speaker combination responds identically. Correct quantities may improve stability and bass definition, but excessive loading can reduce performance.
How many bags do I need?
This depends on the speaker stand. Custom Design’s general guide is at least two bags per 600mm fillable column, but model-specific guidance should take priority.
How many bags are required for FS104 Signature stands?
Custom Design recommends two bags per 610mm central column, meaning four bags for a stereo pair.
Should I fill the four smaller FS104 columns?
No. The central column is intended for mass-loading. The four satellite supports remain unfilled.
Do all Custom Design stands use the same quantity?
No. The required quantity varies according to the number, height and internal size of the fillable columns.
Should I fill the column completely?
Not automatically. Begin with the manufacturer’s recommended quantity and listen before adding more.
Can too much filler make the system sound worse?
Yes. Custom Design warns that excessive mass-loading can adversely affect bass timing and precision.
Should both speaker stands contain the same amount?
Yes. Use equal quantities in corresponding left and right columns.
Can I use part of a bag?
Yes, provided the material is divided accurately and any unused filler is resealed and kept dry.
How should I pour it into the stand?
Use a clean, dry funnel and pour slowly into the approved filling opening.
Can I mix it with sand or another filler?
This is not recommended unless the stand manufacturer specifically approves the mixture.
Can I use it in another manufacturer’s speaker stands?
Only where the stand is designed for granular mass-loading and its manufacturer permits a material with these properties. Custom Design recommends it specifically for its own products.
Can I use Atabites in a Custom Design stand instead?
Custom Design recommends its own Inert Filler. Follow the stand manufacturer’s guidance rather than treating different filler products as automatically interchangeable.
Can it be used inside an equipment rack?
Only where the rack manufacturer identifies a suitable fillable section and approves mass-loading.
Should I fill the stands before assembling them?
Follow the instructions for the specific stand. Most designs should be assembled securely and moved close to their final position before loading.
Can I move the stands after filling?
Yes, but remove the speakers first and lift the stands carefully rather than dragging them.
How should unused filler be stored?
Keep it sealed in a dry place away from children and pets.
Is the packaging recyclable?
Custom Design states that the packaging is made using 76% recycled material and is fully recyclable, subject to local facilities.
Can Audio T calculate the quantity for me?
Yes. Provide your speaker stand make, model, height and number of fillable columns.
Why Buy From Audio T?
- Advice calculating the required number of bags
- Custom Design speaker stand compatibility checks
- Guidance identifying the correct fillable columns
- FS104 Signature loading advice
- Help avoiding excessive mass-loading
- Speaker stand assembly guidance
- Levelling and floor-protection advice
- Speaker positioning and toe-in assistance
- Stand-height and top-plate matching
- Alternative stand filler guidance
- Ongoing speaker and system setup support
Contact your local Audio T store with your speaker stand model and height so that we can help calculate the appropriate starting quantity.