Well, it's been a while since I have been able to get on here and help out... Still not done with the 3rd edition of my book (soon... very soon), I've had a birthday which puts me a year from 60. And I've been sick for two weeks with Dengue Fever. But I'm good now.

Attached is a little paper that I have put together to help answer and sort out some confusion about the termination of the initial signal delay in control room design. Enjoy!

I hope to be more 'regular' on the forum in the coming weeks. We have been extremely busy and I promise to update my studio build pages soon.

If I miss something, please feel free to send me an email to remind me to comment on your post or answer a question.

Cheers,
John

Glad to read that the sickenss is over. Great paper. Thank you.

Andre

Because of your poor weather, Mossies are rare. Guess I will stop complaining.
Glad you are well, welcome back, and thanks for the paper.

DD

Hi John and welcome back. Glad to hear you are feeling better.

And you have a little time to help out here and there. For me especially

And thanks for the PDF. I downloaded and read it, but I've got a few questions.


In regards to the LEDE concept, you quote the Davis criteria, of which it starts with this...
Ok, but can you explain what it means by "low-frequency asymmetrical outer shell" part? In other words...what makes a "shell"...low frequency"? I don't understand HOW a thing that is inert, like a building envelope, that doesn't produce "sound" itself..produce "low frequencies". (kinda like saying "there is a Low frequency Woofer")



That's odd. Given every reply I've read regarding "development" of low frequencies(like in "headphones") )maybe you could define what this so called "development" means ... at least how it relates to the "large enough" part. (vs..what I hear in my little CR..of which I hear LF's that the longest dimension of the room is way short of the wavelengths ... AND, I have NO outer massive nor large shell..of which begs the next question)
First...


From my perspective of years of seeing and contributing to "HOME STUDIO" forums, given "most" typical home studios are of modest size, one room affairs, with only the "home" part as "shell".....let alone...the "large enough to allow the development of bass frequencies" part...or the "larger than that of the Studio room or source" part...


1. How would a potential home studio builder reconcile those statements from your pdf?


Thanks John.

absolutely wonderful summary

you may wish to add in specific criteria for the LEDE/RFZ termination's gain, as i don't recall seeing that referenced within your paper.

thank you!

think of a rigid (concrete) outer shell that determines modal support, and an inner shell of which the walls are LPF but reflect (redirect) the specular frequencies. this way, the user can sit symmetrically (in the middle) within the inner shell BUT not be forced to be in the middle of the room for modes. the inner shell is asymmetrically placed within the outer shell.

Nice text John. Just some minor comments on LEDE/RFZ and splayed walls in the front:

https://gearspace.com/board/7423583-post15.html


Sincerely Jens Eklund

Thank you very much. It's good to be back.


The heavier the partition, (ie; mass or weight), the more reflective it will be at low frequencies. This is what is meant by low-frequency outer shell. The building shell simply reflects the LF waves so that they resonate within the enclosure forming modal resonances. - This is a good thing. Otherwise we would all be mixing in an open field where sound falls off at an even rate at all frequencies except for those reflected off the ground.

If the studio shell is lightweight, low frequencies will not reflect but will pass through the lightweight partition as though it were not there. At this point or crossover frequency and below, there will be no modal support. For example; if the crossover frequency is that of one layer of 5/8" gypsum board (16mm) - fire rated... with an air space of 3.5" or 89mm, the resonant frequency of that partition without insulation or fiberglass in the wall will be approximately 56Hz. This is usually calculated as the cut-off frequency in MAM calculations where at this frequency, the sound will pass through without much resistance. So, at double that frequency our resistance to reflection begins making the sounds that fall below 112Hz to be perceived lower in level.

Well, many (most) studios these days cannot afford the large tracking room so the point is moot. However, I hope that you understand the idea about creating an environment where the operator is able to hear the decay of the Tracking room or Sound source.

We have to deal with the reality of our individual situations. There are no magic bullets or special products that will enable us to defy the laws of physics. There is only the best that we can do. I believe that if we can honestly assess our individual situations, we can/will be better equipped to work within the confines of our environment(s).

There are no perfect rooms. There are only perfect adaptations. It is human imagination, determination, & diligence that produces these wonderful sounds and experiences from sometimes very difficult situations... to create something so unique and inspiring that it immortalizes the composer/producer/mixer.

Well, that's the whole point of my paper... THERE IS NO SET TERMINATION GAIN. The termination gain is determined from testing of the Tracking Room. - Either that or setting it as long as possible to give the illusion of a much larger control room so the the operator can hear the source decay.
Cheers,
John

Welcome back John!

I believe the reference was to the intensity of the termination, not the length of gap.

Nice summation though

John,

Yeah, I know!... intensity and length of gap... both to be set from determination of the intensity and length of gap of the Tracking Room. Nothing is set in stone.

But that's LEDE criteria...

I'm just trying to help folks not to be so 'Obsessive Compulsive Disorder'...

You don't have to.... Do you rigidly follow the instructions on how to set up the distortion channel on your guitar amp?? The treble knobs has to be on 3.5, the mid on 6, the bass on 2... preamp on 7, post amp on 8.25... OMG!! who moved it to 8!!!??

it doesn't matter. get your sound man!

I do not follow LEDE or RFZ criteria. I have my own design criteria and hundreds of happy, successful clients. And I'm not the only one either. There are many ways to skin that cat and I think people try to split to many hairs.

You know how some builders are too... 'no, no, no... you don't put header in like that!!... (it's fine - there are several ways you can do it as long as it it's up to code.)

Acoustics can be a little scarey if you are passionate about it and want to the best. But it takes time and skill development to add the confidence that comes as a result of effort in the field. I want to encourage that.

Take the time. Put in the effort. Hire a designer if you can afford it - you will learn more in 6 months working with them than 10 years study on your own.

You are a good example of that, John. & thanks for your support.

Cheers,
John

Brilliant reply John and great paper.

John,

I'm glad to hear you're feeling better - being sick just sucks.......

Great paper (not surprisingly)

Rod

Post of the year!!!!!!!!!!!!!!

Welcome back John..... If you are up early or up late (12 hour difference in zones) give me a call. Want to pass some info on to you.

Honestly it seems like the only people that "split hairs" are:

a)Designers that try to confuse people into thinking without there service they are sunk.



b)People that are so caught up in theory that they lose what is actually realistic for most people.

Glenn,

WORD! haha!

I'll have to call you in your evening - my morning. Talk to you 'Besok' (tomorrow).

Rod & Jeff - Thanks so much!
Cheers,
John

i did not insist there was a 'set termination gain' - i merely stated "you may wish to add in specific criteria for the LEDE/RFZ termination's gain", as you have with the ISD-length and attenuation levels (-X dB) of reflections within ISD in the paper.

there is no static termination gain, but there is a threshold to sufficiently induce haas trigger (and also that they be of sufficient bandwidth and preferably arriving laterally).

the termination's gain (gain of the first significant indirect signal) will dictate the liveliness of the room (the higher the gain, the livelier the room).

...hence the reason for splayed walls and lack of broadband absorption within RFZ model to maintain as much sonic energy within the space as possible to achieve as high of a termination as possible for the psycho-acoustic trigger. my comments were only meant to be complementary to the paper - i did not think by replying with such that it would be marked as being "OCD". thanks,

A friend was making his first album. Excess exceeded, everything was tried and micromanaged. He was obsessing on some detail one day, sibilance, breaths, or such.
DD- This is a very fine, inaudible, and uninteresting, non musical issue, you really are splitting hairs now.
Friend- I know, I know, but to me they look like 6"x4"s.

DD

+1

/Jens

That video is one of the best I have ever seen.

Please, I have always welcomed your posts as enlightening to all and did not intend to mark it OCD. I meant that many tend to split too many hairs. That's all. Please do not take what I thought to be a humorous comment personally. It was definitely NOT pointed at you.
Cheers,
John

Sent from my GT-S5830 using Gearslutz.com

Hi John, sorry it took a couple of days to get back. Had a wierd snow storm happen on the Oregon coast night before last. Lost all power, and had to deal with 20 or so trees that snapped and fell on the house/driveway/cars....HOLY SMOLLLY...never seen anything like it here before. Anyway, thanks for your answers. But as usual, at least for me, they create more questions. For instance.




Huh? ummm, I'm beginning to think I've missed a road sign along my journey. It seems I've ended up in bum**** egypt instead of my intended destination.

Ok John. Let me get this straight. And really, I'm not TRYING to be hardheaded here. I'm just trying to sort out, what appears to me, as contridictory insights. Let me explain.

For what seems like eternity, I've been under the impression, that for small rooms, LF modal resonanace was EXACTLY the problem, which has been the underpinning for an entire product industry, of which manufacture products to ABSORB these frequencies. In fact, I've read numerous threads over the years where certain "experts" claimed that it was actually "good" for small room recording, that frequencies below the dimensionally supported resonances ...ESCAPED..therefore you don't have to absorb or control them...vs a concrete envelope that traps/reflects them....ie...

..holy moly... I was also under the impression that the purpose of a massive outer shell was LF ISOLATION, not to use it for reflecting LF back into the studio/control room.

So now, are you saying it's GOOD to have these modal resonances??
What am I missing here John??
Well, I thought that was "good" for people with small rooms ...at least from a "treatment" perspective... and bad from an "isolation"/low budget perspective. Hmmm, if I remember right, even Everest mentioned that membrane absorption/and LF escape of lightweight drywall partitions was an "extra" that people with low budget home studios were receiving.


So, at double that frequency our resistance to reflection begins making the sounds that fall below 112Hz to be perceived lower in level.

But..but...I thought that was the point of absorption..that if you absorbed the LF reflections...in reality..you hear the DIRECT LF, instead of null/peak anomolies...which without absorption,, mask what you are hearing from the monitors, and cause EQ'ing mis-judgements..ie..hearing the truth...(sighs/rolls eyes). But now, it appears you are saying that instead of these "escaping" LF allowing you to hear them correctly in the monitors..you percieve them as LOWER...vs LF resonaces in the room causing you to EQ incorrectly? Egads...not only did I miss some roadsigns....I must have mistaken a path as the ROAD!!!

jeeeezus.

Well, many (most) studios these days cannot afford the large tracking room so the point is moot.

Moot???? ummmm, wait a minute. I asked about this LF "development"
thing...in relationship to small home studios. Which now you say...MOST studios these days can't afford a large tracking room"...which seems to me is entirely relevant to small home studios if what you mean is "most studios have SMALL tracking rooms...so what makes it moot? First you say that LF that escape render your perception of them lower, then you say the development of LF is a moot point in small rooms...huh?


However, I hope that you understand the idea about creating an environment where the operator is able to hear the decay of the Tracking room or Sound source.

Of course I do. Isn't hat's the whole point of having a CR TDG longer than the live room? But that's not what were talking about here...at least I think so. ie..ONE ROOM HOME STUDIOS!! My POINT was...your statement about "home studios" in relationship to the LF containment/reflection thing...which seems like an oxymoron to me. at least for a "typical" HOME studio.


What part of MY individual situation didn't you understand John?. why do you think I'm asking these questions. To my way of thinking..I DO have a typical, ONE ROOM, NON CONCRETE EXTERIOR SHELL, LF ESCAPING PARTITIONS WITH TREATMENT DESIGNED FOR LF ABSORPTION...umm,,

hmmm, perhaps I missed the MOOT roadsign...hahahahaha!
That's exactly WHY I'm here....but from what you imply..would it behoove me...from a ..er.."treatment" perspective....to add mass to "my" studio envelope???? You know...to "reflect" these LF's back into the room...so I can hear them at a HIGHER level????.........GAK!!!! this stuff is getting weird.

That "diligence" part might explain my anoyance...after a while..it gets old. Especially when you discover you've missed 10 roadsigns.

Immortalizes?? ummm...I think you are applying a stature to the muses and their scribes that's a bit overinflated John. At least in the context of all the CD's/tapes/records I see in the thrift store that were the top of the crop during their heyday. Immortalized? I defer to a different viewpoint. But that's me.
Hey, putting aside their sales fortunes, maybe someone can tell me where John Lennon is today? My granddaughter didn't have a clue.

WTF??? Testing tracking rooms??? But..but...wait a minute...this one is PERFECT!!!! hold on....... CALLING ROD GERVAIS..CALLING ROD GERVAIS..please report to the "testing Tracking room" memory..


good god..here we go again.


BTW John...HAPPY BIRTHDAY ya ole fart!

More questions is a good thing (like modal resonances) Thank you.

I like being questioned in an honest manner. Like I am always telling clients and students alike to 'question everything'.

Yes, this is a much misunderstood topic. I should probably write and illustrate a paper on this subject... keep bugging me about it. Meanwhile, I hope this brief explanation will help;

The action of standing waving in an enclosure or room will boost the perceived level of frequencies at or near the frequency of resonance which correspond to the dimensions of the room. Axial - L-W-H hitting two surfaces and bouncing very strongly, Tangential - hitting 4 surfaces and reflecting with less intensity, and Oblique - hitting all 6 surfaces and having the lowest intensity.

These reflections must be damped to reduce the negative effects, ie; constructive and destructive summing. The acoustic treatment applied to an enclosure will also assist in damping constructive and destructing summing from Speaker Boundary Interference as well.

When we listen to music in a room or enclosure, reflections support the sound at all frequencies, boosting the level and in many cases make the normal anechoic response of the speakers that we bought seem very choppy. For this reason, I hardly ever look at frequency response graphs of rooms at listening position for any kind of reference. (move the mic and it's totally different.... usless)

Anyway, back on subject: As my friend Wes Lachot has hinted at in his papers, there are no perfect rooms. They will all be choppy to some extent. ESPECIALLY in the low frequencies. This is the whole point about finding the best ratio.

A good room ratio coupled with a very dense rigid exterior shell will insure good modal distribution down to the lowest frequency of interest. This procedure will insure the smoothest and most accurate LF response in any critical monitoring situation. (Coupled, of course, with properly designed damping)

Yes.

It sort of is... a two-way street. While modal resonances DO present a problem, they have benefits too and are truly necessary from a human perspective.

Yes. The lower reflection level at frequencies below that cut-off will cause the lower frequency music notes to sound much lower in level.

If you were to completely fill your room with insulation so that there is no room to even be IN the room... or breathe... you would still not eliminate ONE mode. you might damp them down to one bounce... (you have no idea of the power of the dark side....)

sorry for the lols... Not really. I was talking about the termination of the ISD there... for LEDE/RFZ criteria compliance. I don't follow those guidelines, but do what I think is better. As I said in my paper, a good rule of thumb if it is at all possible with the size of the CR being considered would be a 20mS and -20db. In that range is usually a good starting/ending point.

I see and understand your confusion, but it wasn't me that ever said that LF modes are something you want to loose. Smooth and even is what we all want. Not elimination.

Maybe... But let's look at your individual situation. Have you done testing on your room to see where your LF decay is and what you may or may not be lacking?

Well, he would be one on that immortalized list.

I can respond here for Rod. Like him, I do not 'test' tracking rooms either - as far as room response for comparison. But our larger studio designs are calculated and sometimes tested for RT60 to determine the ISD of the CR for LEDE/RFZ criteria compliance. - It depends many times on the client and their needs.

Thanks buddy!

Cheers,
John

Altiverb and other IR systems have samples of legendary tracking rooms.
It should be possible to import the IR's and see Waterfalls and ETC's for these amazing spaces.
Altiverb can show a thumbnail Waterfall directly. It is helpful.
In general though, most of them look way whacked. Completely out of control first axial modes.
Quite and eye opener.

DD

i'm slightly confused - you say you do not follow LEDE/RFZ guidelines, but the 20ms/-20dB values you adhere to certainly falls within LEDE criteria. if i may ask, what modifications have you made and could you elaborate on why you feel they are "better"? curious to know your experiences if you can share.

above you say you do not follow LEDE guidelines, but here you say you design to meet LEDE criteria compliance? i have not been exposed to measuring RT60 in studio to determine ISD of control room. would you mind elaborating that decision process? thanks!

Thank You John for a thought provoking proposition. I have previously made a note of that Newell quote as I appreciate both his and your frankness. I just recently made an inquiry to a GS member about a related matter regarding first hand design processes.

Clarification of your 20/20 rule:
Is that -20dB the gap or is the termination gain -20dB?

LEDE/RFZ rough guides:


ISD-gap length: about 10-25 ms. More important is that the ISD-gap should be about 2-5 ms longer that the recording room ISD.

Level within the gap: -20 dB or lower.

ISD-gap termination gain: preferably about -12 dB or higher (in order to trigger the Haas effect).

Mr. Brandt has been open about his own criteria which I am grateful.
The question is directed at him and is still open.

Thank you, John.

Yes, 20mS is the gap and termination gain is around -20db. This seems to work well. We have done quite a few different gaps and gains but they usually fall within +/- 20% of these values. Of course, no two rooms are alike and neither are their circumstances.

Jens and all; Termination gain should fall within the Psychoacoustic perceived Haas region which actually has quite a variable range depending on the source material and direction. I would recommend reading Chapter 6 of "Sound Reproduction The Acoustics And Psychoacoustics Of Loudspeakers And Rooms" by Floyd Toole. This is a very excellent subjective study.

Dan, thank you for your input. That's not surprising about those room models. I'd love to see the data... but it would only be out of curiosity.

localhost127; True. But I do not build Asymmetrical shells. - I do for tracking rooms... But that's a 'whole 'nuther country'.
I do follow LEDE/RFZ criteria when my client wants the certification. But most folks want me to do it my way. My design is sort of a twist between the RFZ and NE approach because I use features from both of them to accomplish my goals. And like Thomas (Northward), I keep some of these procedures and goals close and guarded. Not to add to the crazy ideas about a 'dark art', but all designers have their way that makes their stuff a little special in this plug & play world.

The better part?... ha! Yes, I believe that my designs are slightly better balanced, easier to build and more fun to be in. - That's my story and I'm stickin' to it.

Cheers,
John

that's fair - i understand many of you guys here are selling/marketing your own particular designs, so i understand the need to distinguish yourself and your designs from the scientifically peer reviewed acoustic models such as LEDE/RFZ - while maintaining the differences 'secret'
cheers,

Thanks John - great response - saved me the time.....

Rod