Music City Acoustics Quadratic Residue Diffuser - QRD Diffuser for studios and churches
Stepped QRD Diffusers
Music City Acoustics Quadratic Residue Diffuser - QRD Diffuser for studios and churches
Stepped QRD Diffusers

Stepped QRD Diffusers

$245.00

★★★★★ 100+ 5-Star Reviews

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MCA Stepped QRD Diffusers are one-dimensional acoustic diffusers designed to scatter sound across the horizontal plane. Built from Baltic Birch plywood using a quadratic residue sequence, they deliver even, natural diffusion from 816 Hz to 3,721 Hz. The most versatile diffuser in our lineup, they work beautifully in listening rooms, studios, churches, and any space where depth, clarity, and balanced acoustics are essential.

Stepped QRD Diffusers are built to order in our Nashville shop. Production typically takes 1–2 weeks, with most orders completed in 8–10 business days. Once finished, orders usually arrive within 3–5 business days.

Smaller orders ship via UPS Ground, while larger orders ship via LTL freight to keep costs reasonable. Shipping is available within the continental U.S., Alaska, and Hawaii.

Local pickup is available in Nashville.

Eligible items may be returned within 30 days of delivery if unused and in original packaging. A 10% restocking fee applies, and return shipping is the customer's responsibility. Custom and special-order products are not eligible for return.

Diffusers that have been painted or stained cannot be returned, as they are no longer in new, unused condition.

All Stepped QRD Diffusers include a 3-year limited warranty covering defects in materials and workmanship under normal indoor use.

Available Sizes:

  • 2'x2' (23.5" x 23.5" x 4.75") - 18 lbs
  • 4'x2' (47.75" x 23.5" x 4.75") - 30 lbs
  • 6'x2' (71.75" x 23.5" x 4.75") - 45 lbs

Mounting: Wall or ceiling (with optional ceiling hardware kit)

Effective Frequency Range: 816 Hz to 3,721 Hz

Design Type: One-dimensional quadratic residue diffuser

Detailed specifications are available in our product guides.

Stepped QRD Diffusers are built using high-performance materials selected for acoustic performance, durability, and versatility.

Frame and Construction Materials
  • Material: Baltic Birch plywood
  • Construction: Quadratic residue sequence for even, natural diffusion across the horizontal plane
  • Finish: Sanded to 220 grit, unfinished
  • Design: One-dimensional diffusion (scatters sound horizontally)

Our construction approach prioritizes long-term performance and structural integrity while using premium materials.

Wood Finish and Customization

Stepped QRD Diffusers come unfinished, sanded to 220 grit and ready to install as-is. The raw Baltic Birch finish is beautiful and requires no additional treatment.

Optional finishing: Customers may stain or paint their diffusers without affecting acoustic performance. Leaving the wood unfinished showcases the beauty of Baltic Birch and allows us to keep prices down while using premium materials like Baltic Birch instead of MDF or lower-grade plywood.

Indoor Use and Safety

All materials used in Stepped QRD Diffusers are appropriate for indoor environments, including studios, homes, offices, schools, and houses of worship.

  • Baltic Birch plywood is designed for interior architectural use
  • Materials are stable and durable in typical indoor conditions

Stepped QRD Diffusers are designed for straightforward installation and include a 4" French Cleat for standard wall mounting.

Diffusers can be installed on walls or ceilings. Wall installations use the included French Cleat. For ceiling installations, the Ceiling Panel Hardware Kit is required (sold separately).

Optimal placement distance: For best results, position diffusers at least 6 feet away from the listening position or sound source. This gives the diffused sound waves enough distance to fully scatter and create the spatial effect.

Common placements:

  • Sidewalls in listening rooms (for improved imaging and width)
  • Back walls in control rooms or listening rooms (for soundstage depth)
  • Ceilings for balanced diffusion throughout the space
  • Multiple surfaces for comprehensive room treatment

Installation guides are available as downloadable PDFs and include step-by-step instructions for both wall and ceiling mounting.

Handcrafted in Nashville, TN

Built with sustainable and high-quality materials

Shipping

Ships in 1 to 2 weeks all over the continental United States

In-Store Pickup Available

Buy online and pick up your order at our Nashville location

The Diffuser That Works Everywhere

The Stepped QRD Diffuser is the most versatile diffuser we make, designed to perform across a wide range of rooms and placements. They scatter sound evenly through the critical midrange, reducing flutter echo and harsh reflections while preserving the energy and dimension that keeps spaces feeling alive.

Listening rooms gain depth and precise imaging. Studios reveal detail without fatigue. Churches maintain clarity while supporting the natural reverberation that gives congregational singing its power. These diffusers adapt easily to sidewalls, back walls, ceilings, or any combination.

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Built for Versatility

Listening Rooms

Listening Rooms

The Stepped QRD Diffuser is an excellent choice for treating the walls and ceilings. It will improve the depth, accuracy, and clarity of your speakers and amplifiers while retaining the energy and character of your favorite records. Pair the QRDs with Bass Trap Acoustic Panels for low-frequency control, and be prepared to hear your records in a whole new light!

Recording Studios

Recording Studios

Tracking Rooms: QRDs add size and dimension to recordings, controlling flutter echo while maintaining the energy that makes drums, vocals, and acoustic instruments feel natural and alive.

Control Rooms: Once your low end is dialed in and early reflections are controlled, QRDs become the final piece. They add spatial depth to your monitoring environment, making it easier to hear reverb tails, delay nuances, and mix details without fatigue.

Interior of a church with yellow walls, pews and large windows, with acoustic diffusers

Houses of Worship

Traditional worship services and congregational singing benefit from diffusion that maintains reverb while improving clarity. Stepped QRD Diffusers control flutter echo and harsh reflections without reducing the reverb time that makes congregational singing feel powerful and connected. The result is better speech intelligibility, clearer music, and a more enveloping, immersive worship experience.

★★★★★ 100+ 5-Star Reviews

Handbuilt by Us, Loved By You

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Diffusion Done Right.

Dimensions That Deliver: With 3 sizes available, you can match the perfect size Diffuser to your space!

Smooth the Sound: Scatter sound waves evenly to tame harsh reflections, eliminate dead spots, and balance your space. The Stepped QRD Diffusers diffuse from 816Hz to 3,721Hz

Baltic Birch Brilliance: Built from premium plywood that’s sturdy, stylish, and oozes natural character.

Are QRDs Right For Me?

Most likely, the answer is yes! Unlike our PRD Diffusers, our QRD Diffusers are right at home in most spaces! We love using them in:

Tracking rooms that need to sound larger than life.

Control rooms that already have the low-end translating well and now need an extra bit of detail and depth.

Listening rooms where the sound stage is lacking, and you want to get the absolute best performance from your speakers and amplifiers.

Houses of Worship where we need to improve clarity and speech intelligibility without reducing the Reverb Time RT60 too much!

For smaller rooms or spaces where you will be within 6 to 8 feet of your diffuser, we’d recommend the Space Coupling Diffuser or Scatter Face Diffuser paired with Bass Trap or Broadband Acoustic Panels.

Recommended by your favorite creators

“I’ve worked with the MCA team for a while now, and they have become an essential part of the evolution of my studio, Santa's Workshop. From designing custom gobos to overseeing complete room design, their data driven attention to detail is unmatched.”

“I’ve worked with the MCA team for a while now, and they have become an essential part of the evolution of my studio, Santa's Workshop. From designing custom gobos to overseeing complete room design, their data driven attention to detail is unmatched.”

—Dave Clauss
6-time Grammy-winning Recording Engineer/Producer/Mixer

“I’ve known and worked with the team at Music City Acoustics for years and have watched the company grow into what it is today. The quality of their service and products is top tier, and they are genuinely great people to work with. I trust Music City Acoustics with all of my studio treatment needs.”

“I’ve known and worked with the team at Music City Acoustics for years and have watched the company grow into what it is today. The quality of their service and products is top tier, and they are genuinely great people to work with. I trust Music City Acoustics with all of my studio treatment needs.”

—Chris Stevens
Grammy-winning Songwriter/Producer

“There are not many places in the music business where you can get the highest quality, the most attention to detail, the best sounding results, AND stay within your budget. Music City Acoustics is that PLACE! They helped me build the most beautiful and best sounding studio of my career!”

“There are not many places in the music business where you can get the highest quality, the most attention to detail, the best sounding results, AND stay within your budget. Music City Acoustics is that PLACE! They helped me build the most beautiful and best sounding studio of my career!”

—David Spencer
Producer/Singer/Songwriter/Instructor

Your Questions: Answered

  • For best results, position Stepped QRD Diffusers at least 6 feet away from the listening position or sound source. This gives the diffused sound waves enough distance to fully scatter and create the spatial effect you're looking for. If you're working in a smaller room where 6 feet isn't practical, consider our Space Coupling Diffusers, which are designed specifically for close-proximity use.

  • Yes, but only if your low-frequency control is already handled. QRDs don't absorb bass, so if your back wall needs bass trapping, install Bass Trap or Broadband panels first, then mount QRDs in front of them. This gives you low-end control with the spatial benefits of diffusion.

  • Both are excellent diffusers. Stepped QRDs offer one-dimensional diffusion (horizontal scattering), while Primitive Root Diffusers are two-dimensional (horizontal and vertical). QRDs work beautifully in most situations and are available in three sizes, making them the most versatile option for sidewalls, back walls, and ceilings. PRDs are ideal for tracking rooms where you want full 3D spatial control and prefer their distinct sculptural aesthetic.

  • QRDs work well in multiple locations: sidewalls for improved imaging and width, back walls for soundstage depth, or ceilings for balanced diffusion. The placement depends on your room layout and goals. Many rooms benefit from QRDs on multiple surfaces. Contact us for a free room design consultation and we'll help you determine the best placement for your space.

  • No. Stepped QRD Diffusers come sanded and ready to install as-is. The raw Baltic Birch finish looks great in most spaces, but you can stain or paint them if you prefer. Just avoid heavy coatings that could fill the wells between steps, as this may affect acoustic performance.

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