We have PROOF of the efficacy of EQ in correcting room mode resonances!

[Nyal Mellor]

Hi all,

From the vaults of Acoustic Frontiers and HdAcoustics we present incontrovertible proof of the efficacy of equalization in combating room mode resonances: frequency response, time decay and impulse response.

The subject is a 9 seat dedicated home theater where Jeff designed the acoustics and I did the calibration and equalization setup. The result is one of the most kick ass home theaters I have had the pleasure of working on!

Really looking forward to your comments and thoughts!

Nyal & Jeff

 

[fishnchips]

Nice work! Imagine this long, fat resonant tail at 25 Hz in the pre-eq charts combining with a similarly long, fat resonant tail coming from a large, reflex-loaded speaker. The cumulative effect would be atrocious.

 

[Mark Seaton]

Nice work! Imagine this long, fat resonant tail at 25 Hz in the pre-eq charts combining with a similarly long, fat resonant tail coming from a large, reflex-loaded speaker. The cumulative effect would be atrocious.

Funny... I don't see a single mention of what speakers or subwoofers were used in the system. Room modes alone can most definitely have the type of tail seen in the response, even when using the most ideal of sealed subwoofers.

 

[Jeff Hedback]

More of the "Rest of the Story"

Hello Nyal and thank you for the great post and blog. it is a true pleasure to work collaboratively with Nyal. The integrator of the project is a partner I've worked closely with for a few years. I completed the acoustical design in June of 2010 and Nyal completed the calibration just weeks ago.

To provide more insight:
- speakers: PHC
- treatments are RPG Acoustics LF, BAD and absorption control. 2-1/8"
- the riser is framed on Auralex U-Boats, front ported and backfilled with Rockwool for a dual-benefit of some LF control and a tactile response enhancement.

All of the architectural design was completed by the time "we" were brought in. So our scope was to budge and optimize but we couldn't redesign. That is the leading factor toward the unconventional sub location (halfway between floor and ceiling). The LCR and two subs are flush-mounted in a hi-mass and very rigid wall system per my design.

Attached is the acoustical design layout.

 

[Jeff Hedback]

more on the predictive studies

As mentioned, much was predetermined and the seating layout was in that column. Here is an overview with three location studies of my predictive analysis. As the room was fairly "rectangular" in shape and all surfaces were of a relatively hi-mass and isolation type, I did expect these predictive studies to be on target...seems that they were. Nyal and I spoke of the overall effectiveness of this front & back side collaboration and again...it is a pleasure to work with you Nyal.

Note: as these studies are focused on the sub locations (see previously attached pdf), the data above ~100Hz is of little value.

 

[amirm]

Nice work guys!

Jeff, was the sweet spot "C"? If so what was its measurements?

 

[Jeff Hedback]

I'm pretty sure that the final seating layout changed slightly from the one shown in the architectural plan view (to nine seats). So, the main listening/viewing position (which is likely the measurement location shown in Nyal's graphs) would be between locations C & D as marked. I'll let Nyal confirm.

 

[Nyal Mellor]

Jeff is right, there was a three seater couch used instead of two, although it was about the same size as the one in Jeff's diagram. The measurements shown are from between C&D.

 

[Nyal Mellor]

I guess this was so conclusive that Jeff and I have silenced even the doubters - good job buddy!

 

[amirm]

I can't speak for others but I was already sold on the technique so there was nothing to argue about . Appreciate you all posting the measurements though. Great to see these real life examples.

 

[Jeff Hedback]

how 'bout a pic

Here is a pic of the room pre-stretch fabric. you can see the yellow areas are the absorption and the pink with holes...the RPG BAD and the solid pink are the RPG LF Control panels...reference the pdf plan above and it should make even more sense.

Thank you Amirm!

 

[Jeff Hedback]

wow that image is crazy big...sorry. Should have resized (I guess).

 

[Brucemck2]

What is the "RPG LF Control panels" product being used? Is that their Modex product or something different?

 

[Jeff Hedback]

The LF panels are a composite of hardboard (1/8") veneered to 2" of 6.5# rigid fiberglass. There was not space to use the Modex Plates although I tried.

 

[Brucemck2]

The LF panels are a composite of hardboard (1/8") veneered to 2" of 6.5# rigid fiberglass. There was not space to use the Modex Plates although I tried.

Hardboard mounted against the ceiling above or hardboard facing the room below (if latter, making it sort of a diaphramatic absorber of sorts?)

 

[Jeff Hedback]

right...the hardboard is facing the room providing reflection above ~350Hz and reasonably effective absorption down to ~80Hz. They are the "pink" looking panels in the pic without the holes (the holes being the BAD panels)

 

[c1ferrari]

Hi Jeff,

You worked on a friend's room, Art Smuck, and I can attest to the marvelous sound from the room/system.
Congratulations!

 

[Jonas_h]

how 'bout a pic

Here is a pic of the room pre-stretch fabric. you can see the yellow areas are the absorption and the pink with holes...the RPG BAD and the solid pink are the RPG LF Control panels...reference the pdf plan above and it should make even more sense.

Thank you Amirm!

Resurrecting a very very old thread

The treatment plan and products look very much like RPG Behind the scenes: https://www.rpgeurope.com/products/product/behindthescenes.html

Is that correct? Stumbled upon them but havent seen them mentioned anywhere. I like the approach though and seems suitable for home theater sized rooms.

 

[Holmz]

Funny... I don't see a single mention of what speakers or subwoofers were used in the system. Room modes alone can most definitely have the type of tail seen in the response, even when using the most ideal of sealed subwoofers.

Aren’t the room, and treatment, somewhat independent of the speakers?