The million-euro question
"I've seen some nice-looking panels. How many should I grab for my 12 m² room?"
It's the most repeated question, and the honest answer is: it depends. It depends on volume, current room materials, RT60 target and use type. The good news is that it can be calculated with two formulas and ten minutes.
Here's the method and reference numbers.
The 25-50% method (quick rule)
If you don't want to calculate anything and just want a quick answer, this rule of thumb works reasonably well:
Cover between 25% and 50% of the room's hard surfaces with absorber material.
- 25% for a lively room (hi-fi in a living room)
- 35-40% for a music home studio
- 50% for a professional mixing room or voiceover booth
Example
4 × 3 × 2.5 m room. Total surface of walls + ceiling = 2·(4·2.5) + 2·(3·2.5) + 4·3 = 20 + 15 + 12 = 47 m². For a home studio (~35% covered):
47 · 0.35 ≈ 16 m² of panels
If you use 60 × 60 cm panels (0.36 m²): 16 / 0.36 ≈ 45 panels.
But that's overkill. 60 × 60 × 5 cm panels absorb α ≈ 0.85 at 1 kHz, not 1.0. The 25-50% rule assumes highly efficient material. Let's move to the serious calculation.
The real calculation: Sabine step by step
Step 1: volume and surface
Measure your room. For a rectangular L × W × H room:
- Volume: V = L · W · H
- Surface: S = 2·(L·H) + 2·(W·H) + 2·(L·W)
Step 2: current absorption
For a typical untreated domestic room, assume an average coefficient α ≈ 0.08 at 1 kHz:
A_current = S · 0.08
Step 3: define your target
| Use type | RT60 target | |---|---| | Pro mixing room | 0.2 - 0.3 s | | Music home studio | 0.3 - 0.4 s | | Multi-purpose studio | 0.35 - 0.45 s | | Podcast room | 0.2 - 0.3 s | | Hi-fi / home cinema | 0.4 - 0.55 s |
Step 4: required absorption
Apply Sabine solved:
A_target = 0.161 · V / RT60_target
Step 5: deficit
ΔA = A_target - A_current
Step 6: number of panels
A 60 × 60 cm (0.36 m²) panel with 50 mm thickness and α ≈ 0.85 at 1 kHz contributes:
0.36 · 0.85 = 0.31 sabins per panel
If you combine panels + bass traps, corner bass traps contribute more (≈ 0.4-0.5 average broadband sabins per unit).
Number of panels ≈ ΔA / 0.31
Practical reference table
For music home studio (RT60 target 0.35 s), starting from an untreated domestic room:
| Room size | Volume | 60×60 panels | Bass traps | Diffusers | |---|---|---|---|---| | 6 m² (2.4 × 2.5 m, h 2.4 m) | 14 m³ | 6 | 2 | 0 | | 9 m² (3 × 3 m, h 2.5 m) | 22 m³ | 8 | 4 | 0 | | 12 m² (4 × 3 m, h 2.5 m) | 30 m³ | 10 | 4 | 0 | | 15 m² (5 × 3 m, h 2.5 m) | 37 m³ | 12 | 4 | 2 | | 18 m² (4.5 × 4 m, h 2.5 m) | 45 m³ | 14 | 6 | 2 | | 25 m² (5 × 5 m, h 2.7 m) | 67 m³ | 18 | 6 | 4 | | 35 m² (7 × 5 m, h 2.7 m) | 94 m³ | 24 | 8 | 4 |
These figures assume quality panels (density ≥ 28 kg/m³, NRC ≥ 0.75) and thick corner bass traps (300 × 300 × 600 mm).
How to split between panels and bass traps
A useful practical rule:
- 30% of budget / sabins on bass traps (corners)
- 60% on absorber panels (first reflection points, rear wall, partial ceiling)
- 10% on diffusers (rear wall in rooms > 12 m²)
Without bass traps you can't control bass. Without panels, first reflection points colour the mix. Without diffusers in medium rooms, the room sounds too dead. The balance between the three is what defines a well-treated room.
What to do if you can't reach the budget
If the number that comes out exceeds your budget, prioritise by audible impact:
- Bass traps in the 4 vertical corners (impact: enormous on bass)
- 2 panels on left side wall + 2 on right side wall (lateral first reflection points)
- 2 panels on front wall or ceiling (vertical first reflection)
- 2 panels on rear wall (filter late reflections)
- From here, add progressively
With just points 1 and 2 you already get audible improvements of 60-70% of the total potential. The rest is incremental refinement.
Why calculations can fall short
Sabine has limits:
- Assumes uniform absorption distribution (in reality, panels go concentrated)
- Doesn't predict room modes (bass remains a problem even if you meet RT60)
- Assumes constant α, but real absorption depends on mounting (spaced from the wall performs better in bass)
That's why it's wise to calculate conservatively (go 10-15% above the strict minimum) and measure with REW after installing. If measured RT60 exceeds the target in a specific band, you add 2-3 more pieces in that frequency range and you're done.
Shortcut: automatic calculator
Doing this calculation by hand is tedious. Our acoustic configurator takes your room dimensions, materials and target, and returns the exact list of panels, bass traps and diffusers. It also shows you in 3D where to place each one. Free and in 2 minutes.
Don't buy by intuition. Calculate. It's the difference between treating the room right the first time and having to buy again in six months.