Perceptual Effects of Room Reflections

[srrxr71]

Yeah its worth a try as it can help emphasize the direct sound without having to throw away all the reflections. The RFZ is Reflection Free Zone. The image attached from the interwebs sums it up. For my case, though, I absorb beyond ~35 ms and just keep a fairly narrow grouping of reflections above around 1 kHz. These sum with the direct sound to give a flat perceived response at the seating position. A TL;DR of the RFZ is shown below:

View attachment 242318
You probably wont be able to or may not want to eliminate all the reflections after the direct sound, but potentially it can help imaging with a two-channel system since it will help do a better job of preserving the ITDs and ILDs (interaural timing and level differences, respectively). Also of note is the level of the reflections will need to be below that of the direct sound or they can be perceived as the sound sources in their own right, which will wreak havoc on the imaging. I would think maybe something like 10 dB or so reduction compared with the direct sound would be a good place to start.

As Amir alluded to, this was prevalent in the bad old days of crusty speakers with crappy directivity as it was used to get all the sound to diffuse and sum together to something resembling "flat." Now its not really necessary since monitors actually have constant directivity, but I think its still something worth experimenting with in two-channel setups.

Thank you for your good information.

I feel like no matter what you cannot absorb all reflections. However as I have attached I have -12.4dB on the left and -16.3 on the right on early (less than 15ms) reflections.

On late/early ratio I have an additional 3.5dB.

On preserving ITD and ILD information I feel like it depends on having a symmetrical room. Because clearly I have differences on both sides. Left is higher in my case with level. On timing I guess symmetry also matters.

Also as attached you can see that for the mains (which are crossed over at 60Hz) the deeper bass comes in after 20ms. The subs seem to be helping with that problem though.


Unfortunately the asymmetry of my room is something I cannot really help.

 

[Cars-N-Cans]

Unfortunately the asymmetry of my room is something I cannot really help.

Yeah that will complicate things. I had tile floors and cathedral ceilings in my last house. Even with some rugs it still sounded like listening to music in a long hallway.

Having a look at the measurements one thing that would be nice to solve would be the notch at 1 kHz that’s in the left speaker. It’s nearly 10 dB in a fairly critical area. If you’ll could find the source of that and eliminate it that would help things quite a bit. My guess would be a strong reflection that is interfering with the direct sound and causing a cancellation since it shows up in the early reflections as well.

 

[srrxr71]

Yeah that will complicate things. I had tile floors and cathedral ceilings in my last house. Even with some rugs it still sounded like listening to music in a long hallway.

Having a look at the measurements one thing that would be nice to solve would be the notch at 1 kHz that’s in the left speaker. It’s nearly 10 dB in a fairly critical area. If you’ll could find the source of that and eliminate it that would help things quite a bit. My guess would be a strong reflection that is interfering with the direct sound and causing a cancellation since it shows up in the early reflections as well.

Yes thank you! That has been bothering me.

It’s the one near the alcove. I have 5 traps and 2 corner traps there. I think I have to move them around.

It seems we agree the 2 dips around 90,120hz are not a huge deal. Not as bad as the 1KHz one.

I want to solve all of them. That was my first calibration after receiving and placing the 8361.

This weekend. I can listen and enjoy or work on it. Maybe Saturday listen and Sunday work.

 

[Bjorn]

Any thoughts on the dead end live end approach?

It's important to understand that LEDE was a design what developed over many years. So how it started out, was not how it ended. The name LEDE=live end and dead end, is actually quite misleading in how it turned out to be. That approach was before one had the abillity to measure the ETC or the impulse. Something Pudgy Rodgers was the main mind behind but unfortunately she passed away early with cancer.

For a while, LEDE was a design with very strict measurable criterias that needed to be met and a license was given. Later, many have followed the ideas of the design, but without following the strict criterias. So you have variations.

The design can be achieved actually in several ways, where one will maintain even more energy than the standard method. But either way, a proper designed LEDE room will be very lively, super accurate and also very spacious. It's still the most used design in the studio and mastering world today. When done well with quality diffusion and not simply scattering units, it's quite mind blowing to listen to. Such a room, even with mediocre speakers and electronics, will completely blow away high end (measurable) gear.

 

[Bjorn]

The classical studiio LEDE means sitting in the dead zone, half the room being dead and the half behind you is live. This is not not good, killing those important side wall reflections.

That's not really LEDE. Like I mentioned in a previous post, LEDE was a design that developed over many years. What you describe, is partially how it started out, but only partially.
LEDE isn't somehing you can read about at Wikipedia. Much of what ones googles is wrong or misleading information about LEDE.

 

[fredoamigo]

That's not really LEDE. Like I mentioned in a previous post, LEDE was a design that developed over many years. What you describe, is partially how it started out, but only partially.
LEDE isn't somehing you can read about at Wikipedia. Much of what ones googles is wrong or misleading information about LEDE.

The RFZ approach of which Peter D'antonio makes here the chronology seems more inspired by Floyd Toole What do you think ?
https://www.audiotechnology.com/features/resonating-with-history

---

DECADES IN DESIGN​

Control room design has basically evolved to address the changes in loudspeaker reproduction technology and the evolution from mono to surround. D’Antonio gives a potted history from the ’40s to today.


1940s: Monophonic playback in small control booths with no low frequency absorption. Most attention was given to large 15-30,000 square foot tracking rooms to accommodate large big band and symphonic orchestras.


1950s: Stereo began to slowly emerge and the non-symmetrical design of control rooms, poor monitoring conditions and speaker quality was becoming evident.


1960s: Stereo was where 5.1 multi-channel playback is today. Control room design became very important and designers like Tom Hidley, Phil Ramone and John Storyk emerged with various approaches and bass trapping to create rooms capable of auditioning multi-channel playback. Speaker technology also improved.


1970s: Philip Newell and Tom Hidley introduced the non-environment room with broad bandwidth bass trapping and flush mounted monitors. Dick Heyser introduced Time Delay Spectrometry, which led Don and Carolyn Davis to introduce the LEDE (Live End/Dead End) control room, which had an absorptive front and live rear.


1980s: Tom Hidley introduced 10Hz Infrasonic control room and surround-sound 5.1 monitoring. Neil Muncy designed LEDE rooms with all cone loudspeakers. George Massenburg employed a reflection rich zone control room, using front ceiling mounted quadratic diffusors and RPG introduced the RFZ/RPG control rooms offering a spatio-temporal reflection free zone and a diffusive passive surround-sound rear wall using number theoretic reflection phase grating diffusors.


1990s: The RFZ/RPG design proliferated and evolved along with other approaches, but no really new design emerged.


2000s: Floyd Toole presented research indicating that early reflections in small rooms may be beneficial to perception, an idea that was utilised by Massenburg and myself to create the Ambechoic control room design at Blackbird Studio C. New damped metal plate resonators, capable of providing absorption down to 40Hz in a thickness of four inches and the use of multiple in-phase subwoofers had a profound effect in controlling room modes.


2000s-Present: I haven’t seen much innovation in control room design, however, refinements in speaker technology, evolution beyond 5.1 to 7.x and improved acoustic materials have generally improved the quality of reproduced sound and envelopment. What was accomplished passively with the RFZ/RPG design, which was developed for stereo playback, is now being provided actively, however diffusion is even more necessary to uniformly scatter all of the direct sound coming from the speakers.

 

[Bjorn]

The RFZ design and not the RFZ approach as in only reflection free zone comes from LEDE. Peter tried to claim the design or commercialize as his but the idea really comes from someone else and in the development of LEDE.

 

[Bjorn]

The experiment in Black Bird studio by the way really wasn't very succesful. With such an amount of diffusion, you end up with a pretty dry/dead result. LEDE/RFZ is considerably more lively. That being said, the ambechoic approach is basically meant for multichannel and not stereo.

 

[Thomas_A]

That's not really LEDE. Like I mentioned in a previous post, LEDE was a design that developed over many years. What you describe, is partially how it started out, but only partially.
LEDE isn't somehing you can read about at Wikipedia. Much of what ones googles is wrong or misleading information about LEDE.

I am aware of that designs vary. I can’t say how it really started out but there should be some first publications on the LEDE design. ”Classic” might be exchanged for one of them.

 

[sarumbear]

The experiment in Black Bird studio by the way really wasn't very succesful. With such an amount of diffusion, you end up with a pretty dry/dead result. LEDE/RFZ is considerably more lively. That being said, the ambechoic approach is basically meant for multichannel and not stereo.

View attachment 242790

Too much of a good thing is invariably bad.

 

[sarumbear]

The classical studiio LEDE means sitting in the dead zone, half the room being dead and the half behind you is live. This is not not good, killing those important side wall reflections.

You may find that, it is the exact opposite. You sit on the live end.

 

[Thomas_A]

You may find that, it is the exact opposite. You sit on the live end.

It depends. Where are the side wall refelctions hitting you? If it hits at the dead half wall, it is not a true live end at the ear.

 

[sarumbear]

It depends. Where are the side wall refelctions hitting you? If it hits at the dead half wall, it is not a true live end at the ear.

It really does not depend on anything. LEDE is a well established name, which even became an adjective, like Tannoy did.

Live End Dead End concept was created by Tom Hidley and Carolyn & Don Davis 50 years ago when they introduced it to the studio design market in the 70s. It was a room design concept that has absorptive front and a live rear ends. The speakers and the mixing desk was in the dead end and the listener sat in the live end.

You may change any concept to your heart content but I'm afraid you cannot change the history nor the dictionary.

 

[Bjorn]

Sigh. So much confusion and little understanding. Tom Hidley had nothing to do with LEDE. He was behind non environment room.

 

[sarumbear]

Sigh. So much confusion and little understanding. Tom Hidley had nothing to do with LEDE. He was behind non environment room.

What is a "non-environment room"?

Do you mean that Tom has not designed The Manor Studio's control room, which had a LEDE room? Or that Don Davis hasn't published a paper about LEDE?

 

[Thomas_A]

It really does not depend on anything. LEDE is a well established name, which even became an adjective, like Tannoy did.

Live End Dead End concept was created by Tom Hidley & Carolyn Davis 50 years ago when they introduced it to the studio design market in the 70s. It was a room design concept that has absorptive front and a live rear ends. The speakers and the mixing desk was in the dead end and the listener sat in the live end.

You may change any concept to your heart content but I'm afraid you cannot change the history nor the dictionary.

So mixing desk at the dead end? Mixing at far field or with near field monitors? See there is no fixed rule for side wall reflections.

 

[tuga]

The RFZ approach of which Peter D'antonio makes here the chronology seems more inspired by Floyd Toole What do you think ?
https://www.audiotechnology.com/features/resonating-with-history

---

DECADES IN DESIGN​

Control room design has basically evolved to address the changes in loudspeaker reproduction technology and the evolution from mono to surround. D’Antonio gives a potted history from the ’40s to today.


1940s: Monophonic playback in small control booths with no low frequency absorption. Most attention was given to large 15-30,000 square foot tracking rooms to accommodate large big band and symphonic orchestras.


1950s: Stereo began to slowly emerge and the non-symmetrical design of control rooms, poor monitoring conditions and speaker quality was becoming evident.


1960s: Stereo was where 5.1 multi-channel playback is today. Control room design became very important and designers like Tom Hidley, Phil Ramone and John Storyk emerged with various approaches and bass trapping to create rooms capable of auditioning multi-channel playback. Speaker technology also improved.


1970s: Philip Newell and Tom Hidley introduced the non-environment room with broad bandwidth bass trapping and flush mounted monitors. Dick Heyser introduced Time Delay Spectrometry, which led Don and Carolyn Davis to introduce the LEDE (Live End/Dead End) control room, which had an absorptive front and live rear.


1980s: Tom Hidley introduced 10Hz Infrasonic control room and surround-sound 5.1 monitoring. Neil Muncy designed LEDE rooms with all cone loudspeakers. George Massenburg employed a reflection rich zone control room, using front ceiling mounted quadratic diffusors and RPG introduced the RFZ/RPG control rooms offering a spatio-temporal reflection free zone and a diffusive passive surround-sound rear wall using number theoretic reflection phase grating diffusors.


1990s: The RFZ/RPG design proliferated and evolved along with other approaches, but no really new design emerged.


2000s: Floyd Toole presented research indicating that early reflections in small rooms may be beneficial to perception, an idea that was utilised by Massenburg and myself to create the Ambechoic control room design at Blackbird Studio C. New damped metal plate resonators, capable of providing absorption down to 40Hz in a thickness of four inches and the use of multiple in-phase subwoofers had a profound effect in controlling room modes.


2000s-Present: I haven’t seen much innovation in control room design, however, refinements in speaker technology, evolution beyond 5.1 to 7.x and improved acoustic materials have generally improved the quality of reproduced sound and envelopment. What was accomplished passively with the RFZ/RPG design, which was developed for stereo playback, is now being provided actively, however diffusion is even more necessary to uniformly scatter all of the direct sound coming from the speakers.

I don't think that Toole influenced D'Antonio.

1990s: The RFZ/RPG design

2000s: Floyd Toole presented research indicating that early reflections in small rooms may be beneficial to perception

2000s-Present: however diffusion is even more necessary to uniformly scatter all of the direct sound coming from the speakers (regarding multi-channel)

To me it reads like D'Antonio does not agree with Toole.

 

[tuga]

What is a "non-environment room"?

Do you mean that Tom has not designed The Manor Studio's control room, which had a LEDE room? Or that Don Davis hasn't published a paper about LEDE?

Tom Hidley's "Non-Environment Control Room".

THE NON-ENVIRONMENT CONTROL ROOM
The concept of the sound-absorbing acoustic trap has become closely identified with specific styles of acoustic design.
In this article Philip Newell looks at how and why they work.
He then proceeds to the concept of the `non-environment' control room and the experience with the rooms built so far.
Studio Sound, November 1991

 

[tuga]

From Mono to Surround: A review of critical listening room design and a new immersive surround design proposal
Peter D’Antonio (RPG Diffusor Systems, Inc) and George Massenburg (Blackbird Studios)

 

[Bjorn]

What is a "non-environment room"?

Do you mean that Tom has not designed The Manor Studio's control room, which had a LEDE room? Or that Don Davis hasn't published a paper about LEDE?

NER room is basically a semi anechoic room where everything is absorptive apart from the front wall and floor. And the absorptive materiale is very thick, so it works low in frequency. Very different from a LEDE/RFZ design.

Tom Hidley had nothing to do with the developmet of LEDE, but Don Davis, Carolyn's husband very much did.