When installing professional SDI video cables in a broadcast facility, commercial building, school, hospital, or corporate AV system, choosing the correct coaxial cable involves more than signal bandwidth and transmission distance.
You also need to consider where the cable will be installed.
One of the most common questions during permanent video installations is whether the project requires plenum-rated or riser-rated cable.
What is the difference between CMP and CMR cable, and which one should you use for professional SDI video?
Understanding these cable ratings can help installers select the correct materials, avoid unnecessary installation problems, and maintain dependable 3G-SDI, 6G-SDI, and 12G-SDI connectivity.
WHAT IS PLENUM-RATED SDI CABLE?
Plenum-rated SDI cable is professional coaxial cable constructed with materials that meet applicable flame-spread and smoke requirements for qualifying environmental air-handling spaces.
These spaces may include certain areas above suspended ceilings, below raised floors, or within building air-distribution systems.
Plenum-rated communications cable commonly carries the designation CMP.
CMP-rated cable is evaluated for flame propagation and smoke characteristics using applicable testing requirements, including NFPA 262.
This rating is particularly important in commercial buildings where cables may be installed in spaces used to circulate environmental air.
IMPORTANT INSTALLATION NOTE
Not every space above a suspended ceiling is automatically classified as a plenum.
The actual installation requirements depend on the building design, applicable electrical and mechanical codes, and the local authority having jurisdiction.
WHAT IS RISER-RATED SDI CABLE?
Riser-rated cable is designed for installations where cables pass through qualifying vertical building spaces, such as certain shafts connecting different floors.
Communications cable with a riser rating commonly carries the designation CMR.
CMR cable is evaluated for flame propagation under applicable riser testing requirements, including UL 1666.
Riser-rated coaxial cable is commonly used in professional broadcast and commercial AV installations where a plenum rating is not required.
However, a standard CMR rating does not automatically make a cable suitable for an environmental air-handling plenum.
Before installing cable, verify the rating required for the specific pathway.
CMP VS. CMR: WHAT IS THE DIFFERENCE?
| Feature | CMP Plenum Cable | CMR Riser Cable |
|---|---|---|
| Primary Purpose | Air-handling spaces | Vertical riser pathways |
| Common Test | NFPA 262 | UL 1666 |
| Smoke Requirements | Includes smoke-density limits | Different flame-test requirements |
| Typical Application | Qualifying environmental air spaces | Qualifying vertical shafts and other permitted pathways |
| 75-Ohm SDI Available? | Yes | Yes |
| Determines SDI Bandwidth? | No | No |
The most important distinction is that CMP and CMR describe installation-related fire-performance classifications.
They do not, by themselves, determine whether a cable supports 3G-SDI, 6G-SDI, or 12G-SDI.
DOES PLENUM-RATED CABLE PROVIDE BETTER SDI PERFORMANCE?
Not automatically.
A plenum rating does not mean that a coaxial cable has lower attenuation, better shielding, or greater transmission distance than every riser-rated alternative.
Those characteristics depend on the actual cable design.
Professional SDI performance is influenced by:
- Characteristic impedance
- Coaxial cable construction
- Conductor size
- Dielectric materials
- Shielding construction
- Frequency-dependent attenuation
- Return loss
- Connector selection and termination
A properly selected 75-ohm plenum cable can provide excellent SDI performance.
However, its supported video formats and transmission distance must be evaluated separately from its fire rating.
BELDEN 1695A VS. BELDEN 1694A RG6
Two professional RG6 coaxial cables illustrate the difference between plenum and riser constructions.
Belden 1695A — CMP Plenum RG6
Belden 1695A is a professional 75-ohm RG6 coaxial cable with a CMP plenum rating.
It is designed for professional digital video applications, including compatible HD-SDI, 3G-SDI, and 6G-SDI systems.
Its construction makes it useful for permanent commercial installations where the project requires plenum-rated cable.
View AV-Cables Belden 1695A Plenum RG6 BNC Cables.
Belden 1694A — CMR Riser RG6
Belden 1694A is a professional 75-ohm RG6 coaxial cable with a CMR riser rating.
It is widely used in professional broadcast and video installations requiring low-loss coaxial connections.
AV-Cables offers Belden 1694A assemblies for compatible SD-SDI, HD-SDI, 3G-SDI, and 6G-SDI systems.
View AV-Cables Belden 1694A RG6 BNC Cables.
BELDEN 1695A VS. 1694A COMPARISON
| Specification | Belden 1695A | Belden 1694A |
|---|---|---|
| Cable Type | RG6 | RG6 |
| Impedance | 75 Ohms | 75 Ohms |
| Installation Rating | CMP Plenum | CMR Riser |
| Center Conductor | 18 AWG Solid Copper | 18 AWG Solid Copper |
| Typical Supported SDI Formats | SD, HD, 3G, 6G | SD, HD, 3G, 6G |
| Primary Application | Plenum-rated installations | Riser and other permitted installations |
Both are professional broadcast coaxial cable constructions.
The correct choice depends on the required installation rating and the electrical requirements of the video system.
WHAT ABOUT 12G-SDI PLENUM CABLE?
Professional 12G-SDI systems can also require plenum-rated coaxial cable.
For example, a commercial building may use a 12G-SDI video router connected to 4K UHD production equipment in another room.
If the cable pathway requires a CMP rating, the installation needs a cable construction that satisfies both the applicable fire-performance requirements and the 12G-SDI transmission requirements.
Belden manufactures several professional 12G-SDI coaxial constructions with plenum-rated options.
Examples include:
- Belden 4855P: 12G-SDI Mini RG59 plenum coax
- Belden 4505P: 12G-SDI RG59 plenum coax
- Belden 4694P: 12G-SDI RG6 plenum coax
These are different cable constructions from their corresponding riser-rated versions.
Before selecting a cable, confirm the required SDI format, transmission distance, installation rating, and connector configuration.
For specialized 12G-SDI plenum requirements, contact AV-Cables to discuss a custom cable assembly.
WHERE ARE PLENUM SDI CABLES COMMONLY USED?
Plenum-rated professional video cables may be required in several commercial installation environments.
Broadcast Facilities
Permanent SDI cabling may travel through building pathways connecting production control rooms, studios, equipment racks, and technical areas.
Corporate AV Installations
Professional video connections may run between conference rooms, presentation systems, control equipment, and central AV racks.
Schools and Universities
Lecture halls, media-production classrooms, and campus video systems may require cables routed through regulated building spaces.
Hospitals and Healthcare Facilities
Professional AV systems in healthcare buildings may have specific cable-rating requirements based on the installation environment.
Government and Commercial Buildings
Systems integrators may need to select cables according to detailed project specifications and applicable building codes.
In each case, the cable rating should be confirmed before installation rather than assumed from the building type alone.
CAN YOU USE RISER CABLE IN A PLENUM SPACE?
A standard CMR-rated communications cable should not automatically be considered acceptable for an installation requiring CMP-rated cable.
The two classifications have different fire-performance requirements.
If a project requires plenum-rated cable, select a construction with the appropriate listing or use another installation method specifically permitted by the applicable code and approved for the project.
Always verify requirements with the project engineer, building inspector, or local authority having jurisdiction.
Important: This article provides general cable-selection information and is not a substitute for project-specific electrical-code review.
DO BNC, HD-BNC, AND DIN CONNECTORS CHANGE THE CABLE RATING?
The cable's installation rating and its connector configuration are separate considerations.
Professional SDI equipment may use standard BNC, HD-BNC, or DIN 1.0/2.3 interfaces.
These connectors provide different physical connection options for compatible professional video equipment.
However, installing a different connector does not change the cable jacket's CMP or CMR classification.
For permanent installations, verify that the complete cable assembly, connector configuration, and installation method satisfy the applicable project requirements.
AV-Cables offers professional HD-BNC cable assemblies and DIN 1.0/2.3 broadcast connectivity options for compatible equipment.
HOW TO CHOOSE THE CORRECT SDI CABLE FOR A COMMERCIAL INSTALLATION
Professional SDI Installation Checklist
- Confirm the required SDI video format.
- Determine whether the installation requires CMP or CMR cable.
- Verify the complete cable pathway.
- Check the applicable building-code requirements.
- Choose the correct 75-ohm coaxial construction.
- Verify the required cable length.
- Confirm BNC, HD-BNC, or DIN connector compatibility.
- Consider signal attenuation and transmission distance.
- Protect the cable from excessive bending and crushing.
- Provide appropriate cable support and strain relief.
- Label both ends of each cable.
- Test the completed SDI connection.
Planning these details before installation can help reduce unexpected cable replacements and troubleshooting work.
FREQUENTLY ASKED QUESTIONS
What does CMP mean on an SDI cable?
CMP identifies a plenum-rated communications cable construction evaluated for applicable flame and smoke performance requirements.
What does CMR mean on an SDI cable?
CMR identifies a riser-rated communications cable construction evaluated for applicable flame-propagation requirements in vertical riser applications.
Is plenum cable required above every suspended ceiling?
No. The requirement depends on whether the space is classified as an environmental air-handling space and on the applicable building codes and installation methods.
Does CMP cable support 12G-SDI?
Some CMP-rated coaxial cables are designed for 12G-SDI. The cable must meet both the installation-rating requirements and the electrical requirements of the intended SDI format.
Is Belden 1695A plenum rated?
Yes. Belden 1695A is a CMP-rated professional RG6 coaxial cable suitable for compatible SD-SDI, HD-SDI, 3G-SDI, and 6G-SDI applications.
Is Belden 1694A plenum rated?
No. Standard Belden 1694A is a CMR riser-rated RG6 coaxial cable. Belden 1695A is a corresponding plenum-rated option for compatible 6G-SDI and lower-rate applications.
Can plenum cable be used in a riser?
In many communications-cable installations, a properly listed CMP cable may be permitted where a CMR cable would otherwise be used. Verify the applicable code, cable listing, and project requirements before making substitutions.
Does a plenum rating guarantee better video quality?
No. CMP describes fire-performance characteristics. SDI signal quality depends on the electrical construction, cable length, connectors, equipment, and complete transmission path.
THE BOTTOM LINE
Choosing between plenum and riser SDI cable is an important part of planning a professional broadcast or commercial AV installation.
CMP and CMR ratings address different installation environments and fire-performance requirements.
Neither rating automatically determines whether a cable supports 3G-SDI, 6G-SDI, or 12G-SDI.
For reliable installations, select a cable that meets both the building requirements and the electrical performance needs of the video system.
When in doubt, confirm the installation requirements before ordering cable.
PROFESSIONAL PLENUM AND RISER SDI CABLES FROM AV-CABLES
AV-Cables manufactures professional broadcast cable assemblies for studios, production facilities, commercial AV installations, educational institutions, government buildings, and systems integrators.
Our cable selection includes:
- Belden 1695A CMP Plenum RG6 SDI cables
- Belden 1694A CMR RG6 SDI cables
- 12G-SDI Mini RG59 cables
- 12G-SDI RG59 and RG6 cables
- Professional BNC and HD-BNC assemblies
- DIN 1.0/2.3 broadcast video connections
- Custom cable lengths and configurations
Hand assembled in the USA and individually tested.
Need help identifying the correct cable for your installation?
Contact AV-Cables with your required SDI format, cable length, connector configuration, and installation rating.
AV-Cables — Professional • Reliable • Connected