Construction Guides
Acoustic Door Fabrication Guide

Acoustic Door Fabrication Guide
Build STC-Rated Doors On Site

Each door includes two procurement scenarios: Option A — purchase commercial STC-rated doors if available through import or local suppliers, and Option B — fabricate equivalent doors on-site using locally available materials when commercial products cannot be sourced.

SSOT Geometry Lock:  |  Source: ACOUSTIC-CONSTANTS.js  |  MediaVerse Studio Complex

Door Schedule

Four acoustic doors are required for the MediaVerse Studio Complex. Each door is purpose-built to match the STC rating of its host wall. All values sourced from the SSOT.

Door Location Size (cm) STC Weight Frame Type
D1 South wall SE corner (Entry) 90 × 210 50 70 kg 16ga steel, sand/lead filled
D2 Buffer wall (Control Room) 80 × 210 45 55 kg 18ga steel, grout filled
D3 VO/Control partition 80 × 210 45 55 kg 18ga steel, grout filled
D4 Editing/Video Studio partition 90 × 210 40 40 kg 18ga steel, grout filled

Procurement Decision — Buy or Build?

OPTION A — BUY COMMERCIAL DOORS If STC-rated acoustic doors can be sourced (imported or through a regional supplier), this is the preferred route. Commercial doors come with certified STC lab ratings, factory-fitted seals, pre-hung frames, and manufacturer warranties. Lead time and shipping cost are the main variables. Each door tab lists recommended commercial specifications and brands.
OPTION B — FABRICATE ON-SITE If commercial doors are unavailable or the import lead time is prohibitive, all four doors can be built on-site by a competent metal/woodworking contractor. The fabrication instructions in each door tab provide layer build-ups, mass calculations, step-by-step assembly, and frame construction details. Field-built doors can match commercial STC performance if seals are installed correctly.
FactorOption A (Buy)Option B (Build)
STC CertificationLab-certified, stampedEstimated from mass law & build-up
Lead Time4–12 weeks (import)1–2 weeks per door (on-site)
Cost$800–$2,500/door (+ shipping)$150–$400/door (materials only)
Quality RiskLow (factory QC)Medium (depends on contractor skill)
Seal SystemFactory-fitted, testedContractor-installed, flashlight-tested
WarrantyManufacturer warrantyNone (contractor workmanship)
FramePre-hung steel frame includedSteel frame fabricated separately

Acoustic Principles — Read Before Building

MASS LAW STC performance is primarily determined by mass per unit area (kg/m²). A lightweight hollow-core door CANNOT achieve STC 40 regardless of seals. Minimum surface density targets: STC 40 = 25 kg/m², STC 45 = 35 kg/m², STC 50 = 45 kg/m². Every doubling of door mass adds approximately +6 dB to the STC rating.
SEALING IS EVERYTHING Even a perfect 70 kg door leaf will perform like STC 20 if perimeter seals have gaps. A 1 mm perimeter gap can drop effective STC by 10–15 points. Test with a flashlight from the opposite side — if light is visible, sound passes through. The seal matters more than the leaf.
COINCIDENCE DIP A single-material door has a frequency where it transmits sound easily (the coincidence frequency). Multi-layer construction with different materials (steel + wood + damping compound) shifts and spreads this dip, improving broadband STC. This is why every door in this guide uses layered construction — never a single thick slab of one material.
THE FRAME IS HALF THE DOOR Sound follows the weakest path. A perfect door leaf mounted in a lightweight frame with gaps will perform no better than a hollow-core door. The frame must be massive, airtight, and rigidly anchored. Every frame in this guide is steel channel, filled with mass (sand, lead, or grout), and sealed continuously to the wall structure.

Door Anatomy — Where Sound Leaks

WALL WALL STEEL FRAME (HEAD) FRAME (JAMB) FRAME (JAMB) DOOR LEAF (Multi-layer sandwich construction) THRESHOLD (HARDWOOD / ALUMINIUM) SEAL ZONE 1: HEAD SEAL ZONE 2: LEFT JAMB SEAL ZONE 3: RIGHT JAMB SEAL ZONE 4: THRESHOLD (DROP SEAL) Cross-section detail shown per door tab MDF 15 ROCKWOOL 50 mm MDF 15 Steel 1.2 mm Butyl 1.5 Butyl 1.5 Steel 0.8 mm 85 mm total
Steel frame
Door leaf
Threshold
Seal zones
Wall structure

All four seal zones must be airtight. Sound enters through any available gap. The threshold (Zone 4) is the most commonly failed seal point — it requires an automatic drop seal mechanism that activates when the door closes.

STC 50 — D1 Entry Door

D1 — Main Entry Door (STC 50)

This is the heaviest door in the studio complex. It is the exterior entry door in the south wall SE corner. Target weight: ~70 kg. Size: 90 × 210 cm.

Option A — Purchase Commercial Door
RECOMMENDED APPROACH FOR D1 D1 is the exterior entry door with the highest STC requirement. A commercially manufactured STC 50 door comes pre-certified, with factory-fitted seals and a pre-hung steel frame. This eliminates the highest-risk fabrication in the project.

Commercial Specification

ParameterRequirement
STC RatingSTC 50 (lab-certified per ASTM E90)
Clear Opening900 × 2100 mm (single leaf, right-hand swing)
Door LeafSteel-skinned, mineral wool core, minimum 70 mm thick
Frame16-gauge welded steel, filled (grout or sand), pre-drilled for expansion bolts
SealsFactory-fitted continuous compression gasket (3 sides) + automatic drop seal (threshold)
CloserGrade 4, surface-mounted hydraulic (80 kg+), included or specified
Hinges3× heavy-duty ball-bearing, 100 mm, 80 kg+ rated
LockKeyed entry lever handle with deadbolt (exterior-grade)
FinishPowder-coated steel or primed for site painting

Acceptable Commercial Brands

BrandModel / SeriesNotes
IAC AcousticsNoise-Lock Series 40/50Industry standard. Available via international distributors. Lead time 6–10 weeks.
WengerSTC 50 Studio DoorUS-based. Ships internationally. Common in broadcast studios.
Kerfed TechnologiesStudio Door STC 50Australian manufacturer. Good for custom sizes.
Jansen / Hush CitySoundproof Door STC 50European options. Check local distributor networks in Turkey or UAE for shorter shipping.
Chinese OEMCustom STC 50 Steel DoorAlibaba/Made-in-China suppliers. Verify with lab test certificate. Budget option: $600–$900 + shipping.
PROCUREMENT CHECKLIST FOR OPTION A
  • Request the STC test report (ASTM E90 or ISO 10140) — not just a marketing claim
  • Confirm clear opening matches 900 × 2100 mm (or request custom size)
  • Verify frame depth accommodates wall thickness (minimum 140 mm jamb depth for D1)
  • Confirm drop seal is included or specify separately
  • Get freight quote to Damascus — consider shipping via Turkey or UAE for shorter routes
  • On arrival: flashlight test the installed door before accepting

Estimated Cost (Option A)

ComponentEstimated Cost (USD)
STC 50 Door + Frame (pre-hung)$1,200 – $2,500
International Shipping$300 – $800
Closer (if not included)$120 – $200
Installation (local labor)$100 – $200
Total Estimated$1,720 – $3,700
Option B — Fabricate On-Site
WEIGHT WARNING This door weighs approximately 70 kg. It REQUIRES: 3 heavy-duty ball-bearing hinges (not 2), a hydraulic door closer rated for 80 kg+, and proper frame anchoring with expansion bolts. Two people minimum for hanging. Do NOT attempt to hang this door alone.

Door Leaf Cross-Section

D1 Door Leaf Cross-Section — Total Thickness: 85 mm Steel 1.2 mm Butyl 1.5 mm MDF 15 mm ROCKWOOL RW3 50 mm (60 kg/m³) MDF 15 mm Butyl 1.5 mm Steel 0.8 mm OUTSIDE INSIDE 85 mm total 40×40×3 steel angle frame
Galvanized steel sheet
Butyl rubber damping
MDF board
Rockwool RW3 (60 kg/m³)

Layer Build-Up (Outside to Inside)

#MaterialThicknessPurpose
1Galvanized steel sheet1.2 mmOuter mass skin — welded to frame perimeter
2Butyl rubber sheet (self-adhesive)1.5 mmConstrained layer damping — reduces resonance in steel
3MDF board15 mmFirst mass layer — different density than steel shifts coincidence
4Rockwool RW3 (60 kg/m³)50 mmCavity absorption — high density for maximum STC
5MDF board15 mmSecond mass layer
6Butyl rubber sheet (self-adhesive)1.5 mmConstrained layer damping (inner face)
7Galvanized steel sheet0.8 mmInner mass skin — thinner to save weight

Mass Estimate

ComponentCalculationWeight
Outer steel 1.2 mm0.0012 × 7800 × 0.90 × 2.1017.7 kg
Inner steel 0.8 mm0.0008 × 7800 × 0.90 × 2.1011.8 kg
2 × MDF 15 mm2 × 0.015 × 750 × 0.90 × 2.1042.5 kg
Rockwool RW3 50 mm0.050 × 60 × 0.90 × 2.105.7 kg
2 × Butyl rubber 1.5 mm~1.5 kg/m² × 1.89 m² × 2~5.7 kg
Steel angle frame40×40×3 mm, perimeter + 3 cross-members~6 kg
ESTIMATED TOTAL~89 kg
REALISTIC WEIGHT NOTE The calculated weight exceeds the 70 kg target. To reduce weight toward 70 kg, consider: (a) reducing MDF to 12 mm per layer (saves ~12 kg), or (b) using 9 mm plywood instead of 15 mm MDF (saves ~20 kg). Verify the chosen build achieves ≥45 kg/m² surface density for STC 50. The values above are conservative estimates — actual weight depends on material sources available in Damascus. Weigh the finished door on a platform scale before hanging.

Step-by-Step Fabrication

  1. Build the door leaf frame. Weld a rectangular frame from 40 × 40 × 3 mm steel angle. Inside dimensions: 894 × 2194 mm (door size minus 3 mm per side for clearance). Add 3 horizontal cross-members at 500 mm spacing for rigidity and to support the rockwool.
  2. Weld outer steel skin. Lay the 1.2 mm galvanized steel sheet onto one face of the frame. Continuous weld along all edges — no gaps anywhere. Grind welds flush.
  3. Apply butyl rubber. Press self-adhesive butyl rubber sheet to the inside of the outer skin. Use a heavy roller. Cover the entire surface with butt joints — no overlaps, no gaps.
  4. Install first MDF layer. Cut 15 mm MDF boards to fit tightly between frame members. Lay them against the butyl layer. Use construction adhesive on the butyl side for additional bonding.
  5. Fill cavity with Rockwool. Cut 50 mm Rockwool RW3 slabs to friction-fit between cross-members. No gaps — any air gap reduces performance. Push slabs firmly against the MDF.
  6. Install second MDF layer. Cut 15 mm MDF boards to fit on top of rockwool. Press down firmly for a tight fit against the insulation.
  7. Apply second butyl layer. Press butyl rubber sheet onto the second MDF layer. Same method as Step 3 — full coverage, butt joints.
  8. Weld inner steel skin. Lay the 0.8 mm steel sheet onto the frame. Continuous weld along all edges, grind flush. The sandwich is now sealed.
  9. Install hinges. Mount 3 × heavy-duty ball-bearing hinges (100 mm, rated for 80 kg+). Position at 200 mm from top, center, and 200 mm from bottom of the door.
  10. Drill for hardware. Cut mortise for lever handle mechanism (heavy-duty passage set or keyed entry for D1). Use a metal-cutting hole saw for the steel skins. Test handle operation before finishing.
  11. Prime and paint. Apply rust-inhibiting primer to both faces and all edges. Follow with 2 coats semi-gloss enamel. Allow full cure before hanging.

D1 Additional Requirements (Exterior Door)

D1 is the only exterior door. It faces the building corridor and requires weather protection in addition to acoustic performance.

  • Neoprene weather stripping on exterior face perimeter
  • Aluminium rain deflector at threshold (angled drip edge)
  • Magnetic perimeter seal in addition to compression gasket (double-seal system)
  • Automatic drop seal mortised into bottom edge of door leaf (Planet DS or equivalent)
  • Door closer rated Grade 4 minimum (80 kg+)
  • Keyed entry lever handle (not passage set)

D1 Frame Construction

D1 Frame Cross-Section (16-gauge steel, sand/lead filled) WALL STRUCTURE SAND + LEAD SHEET FILL (or grout if lead unavailable) Compression gasket groove DOOR LEAF BOLT 140 mm jamb depth Frame Spec: 16-gauge (1.6 mm) steel channel Welded corners (not bolted) Cavity: dry sand + lead strips Jamb depth: 140 mm 3x expansion bolts per jamb (minimum 6 total) Continuous neoprene gasket in frame rebate
FRAME FILL OPTIONS The ideal fill is dry sand mixed with strips of lead sheet (3 mm thick, cut to cavity width). If lead sheet is not available in Damascus, use cement grout (sand:cement 4:1 mix, poured and vibrated into the frame cavity). Both approaches add the mass needed to prevent sound flanking around the door leaf through the frame.
STC 45 — D2 & D3 Interior Doors

D2 & D3 — Interior Acoustic Doors (STC 45)

These are internal doors only — no weather sealing needed. D2 connects the Editing Suite to the Control Room through the buffer wall. D3 connects the Control Room to the VO Live room through the partition wall.

Target weight: ~50–55 kg each. Size: 80 × 210 cm.

Option A — Purchase Commercial Doors
INTERIOR DOORS — EASIER TO SOURCE STC 45 interior acoustic doors are more widely available than STC 50 exterior doors. Many commercial door manufacturers offer STC 43–48 rated interior doors that meet this requirement. No weather sealing needed — simpler product.

Commercial Specification (per door)

ParameterRequirement
STC RatingSTC 45 minimum (lab-certified)
Clear Opening800 × 2100 mm
Door LeafSteel-skinned or solid core, mineral wool fill, minimum 65 mm thick
Frame18-gauge welded steel, grout-filled, 120 mm jamb depth
SealsContinuous compression gasket (3 sides) + automatic drop seal
CloserGrade 3, surface-mounted (60 kg+)
LockPassage set lever handle (no lock — interior only)

Acceptable Commercial Brands

BrandModel / SeriesNotes
IAC AcousticsNoise-Lock Series 40STC 43–48 range. Interior-rated. Common in recording studios.
STC SolutionsInterior Acoustic DoorTurkish manufacturer. Shorter shipping to Damascus via road freight.
Rw AcousticsStudio Door SeriesUAE-based. Good regional availability.
Chinese OEMCustom STC 45 Steel DoorAlibaba suppliers. Budget: $400–$700/door + shipping. Verify test cert.

Estimated Cost (Option A, per door × 2)

ComponentPer Door (USD)×2 Total
STC 45 Door + Frame$800 – $1,800$1,600 – $3,600
Shipping$200 – $500$400 – $1,000
Installation$80 – $150$160 – $300
Total Estimated$2,160 – $4,900
Option B — Fabricate On-Site

Door Leaf Cross-Section (D2 & D3)

D2/D3 Door Leaf Cross-Section — Total Thickness: 80 mm Steel 0.8 mm Butyl 1.5 mm MDF 12 mm ROCKWOOL RWA45 50 mm (45 kg/m³) MDF 12 mm Butyl 1.5 mm Steel 0.8 mm 80 mm total SIDE A SIDE B
Steel 0.8 mm (both faces)
Butyl rubber 1.5 mm
MDF 12 mm
Rockwool RWA45 (45 kg/m³)
KEY DIFFERENCES FROM D1 (STC 50)
  • Both steel skins are 0.8 mm (D1 uses 1.2 mm outer) — lighter and cheaper
  • Lower density rockwool: RWA45 at 45 kg/m³ instead of RW3 at 60 kg/m³ — reduces weight and cost
  • MDF reduced to 12 mm per layer (D1 uses 15 mm)
  • No weather sealing needed (interior doors only)
  • Standard compression gasket seals only (no magnetic seals)
  • Frame: 18-gauge (1.2 mm) steel, grout-filled (not sand + lead)
  • Jamb depth: 120 mm (vs 140 mm for D1)

Layer Build-Up

#MaterialThicknessPurpose
1Galvanized steel sheet0.8 mmOuter mass skin
2Butyl rubber sheet1.5 mmConstrained layer damping
3MDF board12 mmFirst mass layer
4Rockwool RWA45 (45 kg/m³)50 mmCavity absorption
5MDF board12 mmSecond mass layer
6Butyl rubber sheet1.5 mmConstrained layer damping
7Galvanized steel sheet0.8 mmInner mass skin

Step-by-Step Fabrication

  1. Build the door leaf frame. Weld a rectangular frame from 40 × 40 × 3 mm steel angle. Inside dimensions: 794 × 2194 mm (80 cm door minus 3 mm per side). Add 3 horizontal cross-members at 500 mm spacing.
  2. Weld first steel skin. Attach 0.8 mm galvanized steel sheet to one face of the frame. Continuous weld along all edges. Grind welds flush.
  3. Apply butyl rubber. Press self-adhesive butyl rubber sheet to the inside of the first steel skin. Full coverage, butt joints, use a heavy roller.
  4. Install first MDF layer. Cut 12 mm MDF to fit between frame members. Lay tight against butyl. Use construction adhesive for bonding.
  5. Fill cavity with Rockwool. Cut 50 mm Rockwool RWA45 slabs to friction-fit. No gaps. Push firmly against MDF.
  6. Install second MDF layer. Cut 12 mm MDF to fit. Press firmly against rockwool.
  7. Apply second butyl layer. Full coverage on MDF surface.
  8. Weld second steel skin. Attach 0.8 mm steel sheet. Continuous weld, grind flush.
  9. Install hinges. Mount 3 × ball-bearing hinges (100 mm, rated 60 kg+). Positions: 200 mm from top, center, 200 mm from bottom.
  10. Drill for hardware and finish. Cut mortise for lever handle (passage set, no lock). Prime with rust inhibitor, 2 coats semi-gloss enamel.

Frame Specification (D2 & D3)

  • 18-gauge (1.2 mm) steel channel, welded corners
  • Cavity filled with cement grout (sand:cement 4:1, poured and vibrated)
  • Jamb depth: 120 mm
  • 3 expansion bolts per jamb (6 total minimum)
  • Continuous neoprene compression gasket in frame rebate
  • Automatic drop seal in door bottom edge
  • Door closer: Grade 3 minimum (60 kg+)
D3 SPECIAL NOTE — VO/CONTROL PARTITION D3 is mounted in the same partition wall (W6, STC 53) as the observation window. The door is positioned at x=126–206 and the window at x=40–120 — they do NOT overlap. However, the composite STC of the entire partition depends on BOTH the door AND the window performing to spec. If D3 underperforms due to poor seals, the composite wall STC drops for the entire VO/Control boundary. Pay particular attention to D3 sealing.
STC 40 — D4 Video/Podcast Studio

D4 — Video/Podcast Studio Door (STC 40)

This is the lightest acoustic door. It sits in the W7 partition (STC 40) between the Editing Suite and the Video/Podcast Studio. The door does not need to exceed the host wall rating. Target weight: ~38–42 kg. Size: 90 × 210 cm.

Option A — Purchase Commercial Door
MOST WIDELY AVAILABLE RATING STC 40 is the most common acoustic door rating on the market. Many manufacturers offer standard interior doors at this rating. Turkish and Chinese suppliers frequently stock STC 38–42 doors ready to ship. This is the easiest door to source commercially.

Commercial Specification

ParameterRequirement
STC RatingSTC 40 minimum (lab-certified)
Clear Opening900 × 2100 mm
Door LeafSolid core (mineral wool or particleboard core), minimum 55 mm thick
Frame18-gauge steel or heavy timber, 120 mm jamb depth
SealsContinuous compression gasket (3 sides) + automatic drop seal
CloserGrade 2, surface-mounted (40 kg+)
LockPassage set lever handle (no lock)

Acceptable Commercial Brands

BrandModel / SeriesNotes
IAC AcousticsNoise-Lock Series 30/40Entry-level studio door. Most affordable in their range.
Turkish Door ManufacturersVarious STC 40 steel doorsMultiple suppliers in Istanbul/Ankara. Road freight to Damascus is feasible.
Chinese OEMStandard STC 40 InteriorMost affordable option: $300–$500/door. High availability on Alibaba.
Hush City / Zero Intl.Standard Acoustic DoorUS/EU brands. Check if Turkish distributor available for faster delivery.

Estimated Cost (Option A)

ComponentEstimated Cost (USD)
STC 40 Door + Frame$500 – $1,200
Shipping$150 – $400
Installation$60 – $120
Total Estimated$710 – $1,720
Option B — Fabricate On-Site
COST ADVANTAGE This all-wood door costs approximately 40–50% less than the steel-skinned versions and can be built with basic woodworking tools (no welding required). It meets STC 40, which matches the host wall W7 — there is no benefit to exceeding the wall's rating. The door would be the most expensive element in the wall if over-specified.

Door Leaf Cross-Section

D4 Door Leaf Cross-Section — Total Thickness: 82 mm (All-Wood Build) MDF 15 mm Butyl 1.5 mm ROCKWOOL RWA45 50 mm (45 kg/m³) Butyl 1.5 mm MDF 15 mm Timber frame 40 x 40 mm solid pine/poplar 82 mm total (with timber frame) NO STEEL SKINS No welding required Woodworking tools only
MDF 15 mm
Butyl rubber 1.5 mm
Rockwool RWA45 (45 kg/m³)
Timber frame (40 × 40 mm)

Layer Build-Up

#MaterialThicknessPurpose
1MDF board (outer face)15 mmOuter mass layer
2Butyl rubber sheet1.5 mmDamping layer
3Rockwool RWA45 (45 kg/m³)50 mmCavity absorption
4Butyl rubber sheet1.5 mmDamping layer
5MDF board (inner face)15 mmInner mass layer

Perimeter: 40 × 40 mm solid timber frame (pine or poplar) with 2 horizontal cross-members.

Step-by-Step Fabrication

  1. Build perimeter frame. Cut 40 × 40 mm solid timber (pine or poplar) to form a rectangular frame. Glue + screw with 60 mm wood screws. Inside dimensions: 894 × 2194 mm. Add 2 horizontal cross-members at roughly 700 mm spacing.
  2. Attach first MDF sheet. Screw 15 mm MDF to one face of the timber frame. Countersink all screws. Fill screw holes with wood filler.
  3. Apply butyl rubber. Press self-adhesive butyl rubber damping sheet to the inside surface of the first MDF. Full coverage, butt joints, roller-pressed.
  4. Fill cavity with Rockwool. Cut 50 mm Rockwool RWA45 to friction-fit between cross-members. No gaps anywhere. Press firmly against butyl layer.
  5. Apply second butyl layer. Press butyl rubber to the inner face of the second MDF sheet (the side that will face the rockwool) before attaching.
  6. Attach second MDF sheet. Screw 15 mm MDF to the other face of the timber frame. Countersink and fill screw holes.
  7. Edge-band all 4 edges. Apply 2 mm PVC edge banding or hardwood lipping to hide the sandwich construction and protect the edges from impact damage.
  8. Sand and finish. Sand all surfaces smooth. Apply primer + 2 coats paint (semi-gloss enamel). Allow full cure.
  9. Install hinges. Mount 3 × standard-weight ball-bearing hinges (100 mm, rated 40 kg+). Positions: 200 mm from top, center, 200 mm from bottom.
  10. Install lever handle. Cut mortise for passage set lever handle (no lock — D4 is internal only). Test handle operation.

Frame Specification (D4)

  • 18-gauge (1.2 mm) steel channel, welded corners
  • Cavity filled with cement grout
  • Jamb depth: 120 mm
  • 3 expansion bolts per jamb
  • Continuous neoprene compression gasket in frame rebate
  • Automatic drop seal in door bottom edge
  • Door closer: Grade 2 minimum (40 kg+)
WHY STILL A STEEL FRAME? Even though D4 has a wood door leaf, the frame is still steel channel filled with grout. A timber frame would not provide enough mass to prevent flanking, and wood frames warp over time creating seal gaps. The steel frame is non-negotiable for any door rated STC 40 or above.
Seals & Hardware

Seals & Hardware The Most Critical Tab

THIS IS THE MOST IMPORTANT SECTION IN THIS ENTIRE DOCUMENT A perfect door leaf with bad seals = STC 20. Every door on this page will fail its STC rating if the seals are not installed correctly. Read this tab completely before building any door. The seal is more important than the leaf construction.

A) Perimeter Compression Seal

Material: Closed-cell neoprene rubber (EPDM), 10 × 15 mm profile.

Installation: Routed into a groove in the door frame rebate (not surface-mounted). The door leaf compresses the gasket by 3–5 mm when closed.

Coverage: Must be CONTINUOUS around all three sides (head + both jambs) — no breaks at corners. Cut mitre joints at corners and seal with cyanoacrylate adhesive.

Perimeter Seal Detail — Frame Rebate Cross-Section FRAME GASKET DOOR LEAF 3-5 mm compression Requirements: Closed-cell EPDM neoprene Profile: 10 x 15 mm Routed groove (not glued on surface) Continuous around 3 sides Mitre-cut corners, CA glue sealed NO breaks. NO gaps. NO overlaps.

B) Automatic Drop Seal (Threshold)

THE MOST IMPORTANT SEAL The threshold is the single most common point of failure. Sound travels under doors easily. The drop seal is the only mechanism that creates an airtight seal at the floor while still allowing the door to swing freely.

Mechanism: A spring-loaded seal is mortised into the bottom edge of the door leaf. When the door closes, a plunger contacts the frame jamb, pushing the seal downward to contact the threshold. When the door opens, the seal retracts so the door swings freely without dragging.

Brands (globally available): Planet DS (UK), Lorient LAS8001, Raven RP48 — or source generic equivalent from Chinese or Turkish suppliers via AliExpress/Alibaba.

Automatic Drop Seal — Two Operating States DOOR OPEN (seal retracted) DOOR BOTTOM EDGE DROP SEAL (retracted) ~15 mm gap (door swings freely) THRESHOLD DOOR CLOSED (seal extended) DOOR BOTTOM EDGE SEAL (extended, compressed) THRESHOLD AIRTIGHT CONTACT Plunger in door edge contacts frame when door closes, pushing spring-loaded seal down onto threshold surface.

If an automatic drop seal is completely unavailable, use a surface-mounted door bottom sweep as a fallback — but this is less effective and will drag on the floor during operation. A drop seal is strongly preferred.

C) Threshold Construction

  • Material: 30 mm hardwood (oak or mahogany) or 3 mm aluminium plate on timber backing
  • Flatness: Must be perfectly flat — any bow or warp allows sound to pass under the seal
  • Seal contact surface: Must be smooth and even — sand and seal with polyurethane
  • Installation: Set into floor with acoustic sealant (Tremco) on all edges — no air gaps between threshold and floor
  • Width: Full width of door frame opening plus 10 mm overlap into each jamb

D) Door Closer

A hydraulic surface-mounted closer is required on every acoustic door. The closer must pull the door firmly into seal compression — if the closer is too weak, the door does not seal and all acoustic performance is lost.

DoorWeightCloser GradeMinimum RatingExamples
D1 (STC 50) ~70 kg Grade 4 80 kg+ Dorma TS83, GEZE TS4000
D2, D3 (STC 45) ~55 kg Grade 3 60 kg+ Dorma TS68, GEZE TS2000
D4 (STC 40) ~40 kg Grade 2 40 kg+ Dorma TS68, GEZE TS1500
CLOSER ADJUSTMENT
  • Closing speed: 3–5 seconds from 90 degrees to latch
  • Latching action: the final 10 degrees should snap the door firmly into the seals
  • Too fast = slams the door (damages seals and annoys occupants)
  • Too slow = staff leave the door ajar (destroys all isolation)
  • Test by releasing the door from 90 degrees open and timing the full close

E) Hinges

Ball-bearing type only. Standard butt hinges cause door sag over time, which creates seal gaps at the head and latch side. Three hinges per door (all sizes).

DoorHinge SizeRatingQuantityPositions
D1 100 mm Heavy-duty, 80 kg+ 3 200 mm from top, center, 200 mm from bottom
D2, D3 100 mm Standard, 60 kg+ 3 200 mm from top, center, 200 mm from bottom
D4 100 mm Standard, 40 kg+ 3 200 mm from top, center, 200 mm from bottom

All stainless steel or zinc-plated. No plastic bearings. Lubricate annually with light machine oil.

F) Latch / Lock Mechanism

  • Handle type: Lever handle (not knob — building codes and ergonomics require levers)
  • D1 (exterior): Keyed entry or privacy set
  • D2, D3, D4 (interior): Passage set (no lock)
  • Latch bolt: Must fully engage the strike plate — any slack = sound leakage path
  • Strike plate: Recessed into frame with acoustic sealant behind the plate (fill the void)
  • Backset: Standard 60 mm backset for all doors

G) The Flashlight Test (Quality Check)

THE FLASHLIGHT TEST — MANDATORY FOR EVERY DOOR

After installing each door, perform the flashlight test from inside the room with all lights off. Have someone shine a bright flashlight around the ENTIRE perimeter — head, both jambs, threshold.

If ANY light is visible from inside, sound will pass through that gap.

Fix ALL visible light leaks before proceeding to the next construction phase. Common failure points:

  • Corner joints where head gasket meets jamb gasket
  • Hinge-side gaps (door sag)
  • Threshold ends where drop seal meets jamb gasket
  • Behind strike plate (hollow cavity not sealed)
  • Lever handle hole through door leaf (needs tight escutcheon plates)

H) Seal Maintenance Schedule

Acoustic door performance degrades over time. A 1 mm perimeter gap can reduce effective STC by 10–15 points. Regular inspection is mandatory.

Inspection Interval

Annual (minimum), or after any physical impact to door or frame.

Gasket Checks

  1. Perimeter gaskets: Check for compression set, cracking, or gaps. Replace if any light is visible during flashlight test.
  2. Drop seals: Verify full contact with threshold when door closes. Adjust mechanism or replace if seal does not make full contact.
  3. Threshold gaskets: Inspect for wear from foot traffic. D1 exterior threshold is especially vulnerable.
  4. Magnetic seals (D1 only): Verify magnetic strip alignment and pull force > 2 kg/m.

Closer & Hinge Checks

  1. Door closer: Verify latching force pulls door fully into seal contact. Re-adjust closer arm and spring tension if door does not close firmly.
  2. Hinge pins: Lubricate annually with light machine oil. Squeaking indicates wear that may cause staff to prop doors open.
  3. Closing speed: 3–5 seconds from 90 degrees to latch. Too fast causes slam damage to seals; too slow means doors are left open.
DO NOT PROP ACOUSTIC DOORS OPEN Propping acoustic doors open during sessions destroys all isolation. Consider magnetic hold-open devices that release on studio "LIVE" signal (tally light activation).

Complete Hardware Summary

ComponentD1 (STC 50)D2/D3 (STC 45)D4 (STC 40)
Leaf construction Steel + MDF + Rockwool RW3 Steel + MDF + Rockwool RWA45 MDF + Rockwool RWA45 (no steel)
Outer skin 1.2 mm steel 0.8 mm steel 15 mm MDF
Inner skin 0.8 mm steel 0.8 mm steel 15 mm MDF
Perimeter seal Magnetic + compression Compression gasket Compression gasket
Drop seal Required Required Required
Frame gauge 16-gauge (1.6 mm) 18-gauge (1.2 mm) 18-gauge (1.2 mm)
Frame fill Sand + lead sheet Cement grout Cement grout
Jamb depth 140 mm 120 mm 120 mm
Closer grade Grade 4 (80 kg+) Grade 3 (60 kg+) Grade 2 (40 kg+)
Hinges 3x heavy-duty 80 kg+ 3x standard 60 kg+ 3x standard 40 kg+
Lock type Keyed entry Passage set Passage set
Weather seal Yes (exterior) No No