QDA-11 Quadratic Diffusor Absorber


The QDA – 11 is two units within one. First, a quadratic diffuser based upon prime number 11 with a diffusion frequency response from 385 Hz. – 3,450 Hz. Behind the prime 11 quadratic diffuser is our activated carbon broadband low frequency broadband absorber from 30 Hz. – 400 Hz. Broadband lower frequency absorption is required in all small rooms. The absorption performance is the same as our ACDA-10 unit. At the base of the QDA-11 is our more frequency specific carbon absorber from 30 Hz. – 50 Hz. This base absorber is designed after our ACDA-12 unit and offers large amounts of absorption from 30 – 50 Hz. which is the frequency range of unwanted pressure issues in the majority of today’s smaller rooms. The QDA measures 24″ w x 60″ h x 9″ deep and weighs 225 lbs.

– ACDA-10 Riverbank Test Result

– ACDA-12 Riverbank Test Result

Diffusion and lower frequency absorption goes hand in hand with the front and rear wall locations. The front wall is an area of high unwanted low frequency pressure and the rear wall follows the same pattern. Low frequency energy builds up at the boundary surfaces of  front and rear wall locations. You need both a frequency specific and a broadband absorption approach to deal with the magnitude of these low frequency pressure issues.

The QDA-11 was designed for those who do not have the physical space requirements to accommodate deeper units but still want the advantages of broadband and frequency specific absorption along with the diffusion benefits offered by quadratic diffusion.

If you order the QDA today you will also get

  • A free one 30 minute phone or video consultation on your room mode issues with me, the products inventor, Dennis Foley
  • A 100% risk free 30 day money back guarantee

Request Quote

These units have special handling and shipping requirements, due to their weight and size. Please call us on 520-392-9486 or click HERE to contact us so we can assist you further.

Additional information

Weight 200 lbs
Dimensions 10 × 24 × 60 in


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