First reflection point ..question

[AMIEL]

Hi!!
I want to know as we have the first reflexion point in the front of the room..if exist also a first reflexion point in the back..and how do u find that firts reflexion...

also the main point(height) of the first reflexion is at the hight of the speaker o the same from the floor tothe ceiling?

[lucey]

Have an assistant hold a mirror flat on the wall and look for the tweeter.

[AMIEL]

Originally Posted by lucey

Have an assistant hold a mirror flat on the wall and look for the tweeter.

Thanks!..yeah I know that....but that applyes to the side on the back of the studio?

[lucey]

Originally Posted by AMIEL

Thanks!..yeah I know that....but that applyes to the side on the back of the studio?

if you're looking for the line from the speaker to the back wall to your head ... then, yes. but generally in a rectangular room the entire back wall can be diffused. front and back perhaps, with side absorption or splayed side walls.

[jayfrigo]

Originally Posted by AMIEL

Thanks!..yeah I know that....but that applyes to the side on the back of the studio?

...and the ceiling, and the floor, and the console itself. The three ways to treat it are with absorption, diffusion, or reflection (aiming it somewhere besides your listening position, often into other treatments). Which method you choose for each reflection point depends on a number of factors, and the overall room plan.

[Ethan Winer]

Reuven,

Yes, the rear wall is a reflection point, and if it's less than ten feet behind your head those reflections are considered "early" and should be absorbed or diffused. Even when they're not early they should usually be handled.

Also see this article:

RealTraps - How To Set Up a Room

--Ethan

[AMIEL]

Thanks Ethan! Is very clear in your website how to trat the firt reflexion point i.....Thanks!!

If a room is 20 Ft lenght by 10Ft wide...I got the firts reflexion point...test and I am amzed how good canceled the slap echo!! ...A/B with and without the panels on the sides and you can feel the huge difference!!

But my question is .....in the sides of the back wall that first reflexion should be proporsional at the ones on the front side walls?

I understood how to find them in the front...but if I am not wrong..I did not find any feedback about the backwall.
thanks!

[Ethan Winer]

Reuven,

Originally Posted by AMIEL

in the sides of the back wall that first reflexion should be proporsional at the ones on the front side walls?

There won't be first reflections on the side walls behind the mix position unless you have a 5.1 surround setup. This is not to say that absorption on the side walls behind you is not useful. If you clap your hands back there and hear flutter echo or ringing, then absorption there will help. But that's not the same as treating specific first reflections from the loudspeakers.

--Ethan

[AMIEL]

Thanks Ethan ..very clear and very amazing/valuable info on your website!

[hereticskeptic]

Originally Posted by Ethan Winer

Reuven,

Yes, the rear wall is a reflection point, and if it's less than ten feet behind your head those reflections are considered "early" and should be absorbed or diffused. Even when they're not early they should usually be handled.

Also see this article:

RealTraps - How To Set Up a Room

--Ethan

Hey Ethan,

What determines whether you should use absorption, or diffusion when treating points? I'm not looking for the perfect room treatment, as I'm just getting a small home studio up and running. I'm simply trying to find a solid start which I can build from over time.

Would you use OC703 or FRK OC703 for bass traps, what density and how thick?

OC 703 for reflection points? 2", or thicker?

What are the reflection points? I've read so many different things on this subject, that I'm somewhat confused. Is the wall right behind your monitors/desk a reflection point? The ceiling right above where you mix? The side walls where you can see the monitors reflected through a mirror? Is the back wall considered a reflection point, or do you just completely cover it? If recording vocals in the same room you're mixing in, is it true that you want a panel on the ceiling near the back wall? Do certain reflection points require different levels of panel thickness? Is there an ideal location to place the mic stand when recording?

Apologies for all the questions. I'm just ready to get some materials and start getting the room treated. I feel like I'm close to grasping what is needed, but am having trouble pinpointing things exactly.

If you need room size, or any other info, I can get it for you (don't have a tape measure at the present time), but I'm really just looking for a general outline of how one can treat a small bedroom in an apartment to get better sound. Oh, and I'd be recording vocals, as well as mixing in the same room. Thank you so much for any and all help.

-Skep

[Ethan Winer]

Originally Posted by hereticskeptic

What determines whether you should use absorption, or diffusion when treating points?

I prefer absorption at reflection "points," if that's what you mean. I mentioned diffusion for the rear wall behind you. In that case the determining factor is budget. Good diffusion costs a lot more than good absorption, whether you DIY or buy commercial products.

Would you use OC703 or FRK OC703 for bass traps, what density and how thick? OC 703 for reflection points? 2", or thicker?

705 FRK at least 4 inches thick for corner traps, 703 or 705 at least 2 inches thick for reflection points.

What are the reflection points?

Early Reflections

--Ethan

________________
The Acoustic Treatment Experts

[hereticskeptic]

Originally Posted by Ethan Winer

I prefer absorption at reflection "points," if that's what you mean. I mentioned diffusion for the rear wall behind you. In that case the determining factor is budget. Good diffusion costs a lot more than good absorption, whether you DIY or buy commercial products.



705 FRK at least 4 inches thick for corner traps, 703 or 705 at least 2 inches thick for reflection points.



Early Reflections

--Ethan

________________
The Acoustic Treatment Experts

Thank you sir!

[SAC]

It may already have been covered in depth, but...

The problem may be caused by the terminology.

Specular reflections are commonly referred to by their "order". First order, second order, third...etc....

The order refers to how many incident surfaces they have encountered and reflected from. Hence, a first order reflection has been incident with one boundary between the source and the receiver.

The next two primary variables associated with a reflection, regardless of order, are arrival time and gain.

When one refers to early reflections, typically this refers to the first orer reflections that originate (depending upon the situation of the source within the room) from the side walls, floor and ceiling, and any intermediate surfaces such as work surfaces/desks, etc.

Note, a higher order reflection, such as a 2nd order reflection, can potentially arrive sooner than a particular lower order reflection, such as in this case a first order reflection, dependent upon room topology.

Additionally, with each boundary incidence, a degree of energy will be 'lost' and thus, along with distance and air resistance, gain is 'lot'.

Additional real world factors come into play, such as the acoustical impedance o the boundary which can cause variance in the direction, gain, polarity of the incident energy, as well as environmental factors such as heat.

Likewise, incident surface variations can result in modification to the reflected energy in the form of simple scattering or interactive/superpositional diffusion which will further modify the spatial, and possibly, temporal nature of the reflected energy.

[hereticskeptic]

Originally Posted by Ethan Winer

I prefer absorption at reflection "points," if that's what you mean. I mentioned diffusion for the rear wall behind you. In that case the determining factor is budget. Good diffusion costs a lot more than good absorption, whether you DIY or buy commercial products.



705 FRK at least 4 inches thick for corner traps, 703 or 705 at least 2 inches thick for reflection points.



Early Reflections

--Ethan


________________
The Acoustic Treatment Experts

If I can't afford diffusion at the present time, would you recommend leaving the rear wall bare, or adding some type of panels for the time being? If so, should I add reflection point panels, or bass trap style? Also, can you please show me an image of what you guys mean by straddling panels in the corners? have two ideas, but want to be sure which is correct

I'm likely going to go with some reflection point panels behind the monitors as well, as the room is so small and thus the desk won't be very far from the front wall. Thoughts on this? My basic plan at this point, pending insight from you on how to treat the rear wall for now is:

2" 703 spaced 2" from wall at reflection points: 2 behind monitors (front wall), 1 on ceiling above mix point, 1 on ceiling near rear wall, 1 on left wall near mix point, 1 on right wall near mix point, 4 conjoined to form a portable booth (placement to be determined)

4"-6" 703 straddling the rooms 4 corners as bass traps, top to bottom (one stack of panels on bottom, one stack on top, per corner).

Sound cool?

I basically just want to know what alternative to diffusion, if any, would be wise for the rear wall as a start. Other than that, I just need to confirm what straddling looks like, and I'm about ready to get started!

I know I'm asking a lot of questions, some probably even sounding repetitive (my grasp of the terminology isn't great), so I appreciate all of you guys' help, truly. Can't stress it enough!

[Glenn Kuras]

If I can't afford diffusion at the present time, would you recommend leaving the rear wall bare, or adding some type of panels for the time being?

Thick absorption for the back wall is important. Don't skip it.

Everything else you listed sounded pretty good to me. The only thing is you may or may not need panels behind the speakers. If you did it would be to control SBIR.
See more about SBIR
GIK Acoustics. What is SBIR?

[localhost127]

Originally Posted by Glenn Kuras

Thick absorption for the back wall is important. Don't skip it.

Everything else you listed sounded pretty good to me. The only thing is you may or may not need panels behind the speakers. If you did it would be to control SBIR.

glenn, why do you recommend heavy absorption (4-6") on the back wall vs thinner absorption (i.e. what is used/recommended to treat early reflection points -- 2" with 2" gap or just 4")? is this to help tame the room mode between the front/rear wall so the listening setup isn't directly in a null/peak?

if so, then why wouldnt adding more absorption on the front wall further help to combat this?

[Ethan Winer]

Originally Posted by localhost127

glenn, why do you recommend heavy absorption (4-6") on the back wall vs thinner absorption

The rear wall is a primary source of bass peaks and nulls:

Bass Waves in the Control Room

If you made the traps there two feet thick that isn't too much. Really.

if so, then why wouldnt adding more absorption on the front wall further help to combat this?

Yes, thick absorption on the front wall helps too. Though mainly for bass frequencies, not usually for mids and highs as is commonly done using too-thin material.

--Ethan

________________
The Acoustic Treatment Experts

[hereticskeptic]

Originally Posted by Glenn Kuras

Thick absorption for the back wall is important. Don't skip it.

Everything else you listed sounded pretty good to me. The only thing is you may or may not need panels behind the speakers. If you did it would be to control SBIR.
See more about SBIR
GIK Acoustics. What is SBIR?

I saw below where Ethan mentioned having 2 feet of panels on the rear wall wouldn't bee too much. Woooow.

So is that what diffusion ends up being? Much thicker material? I still didn't see a recommended alternative for diffusion, as you guys have mentioned it is quite costly. Would 4" bass traps be fine? Thicker? Would you cover the entire rear wall, or just put like 2 panels up? The rear wall treatment still confuses me.

Is taking this much base out of the room not going to negatively affect recording? I know I was old to treat it as a mix room first, but I just want to be sure I'm not going to buy all of this material, treat the room, and get poor vocals, in a room where I can mix very well.

As far as the SBIR, I got a room analysis emailed to me by Bryan Pape from your company. He recommended panels on the front wall, since the room is so small and the desk/monitors can't really be moved too far from the front wall.

[Glenn Kuras]

So is that what diffusion ends up being? Much thicker material? I still didn't see a recommended alternative for diffusion, as you guys have mentioned it is quite costly. Would 4" bass traps be fine? Thicker? Would you cover the entire rear wall, or just put like 2 panels up? The rear wall treatment still confuses me.

Diffusion is used on the back wall to break up mids and high end. 4" will work and how many is really a hard one to say. In your room I would start with 2 panels and see how that goes.
See the following about diffusion
GIK Acoustics presents "How Diffusion Works!"

Is taking this much base out of the room not going to negatively affect recording? I know I was old to treat it as a mix room first, but I just want to be sure I'm not going to buy all of this material, treat the room, and get poor vocals, in a room where I can mix very well.

No it will actually give you more clarity of the lows which will feel like more low end.
GIK Acoustics. How Bass Traps work.

As far as the SBIR, I got a room analysis emailed to me by Bryan Pape from your company. He recommended panels on the front wall, since the room is so small and the desk/monitors can't really be moved too far from the front wall.

Bryan knows his stuff. If he recommends it then I would do it

[hereticskeptic]

Thanks for the links Glenn. It sounds like diffusion is something that is not meant for a DIY project.

I have to say, I am still a little lost when it comes to the rear wall, in that I've been told thick absorption is a must for my rear wall, but also that diffusion should be used on the rear wall? Does this depend on the distance fro mix point to rear wall?

I believe you told me thick absorption for the rear, and then diffusion on the side walls behind the mix point. I won't do diffusion yet, seeing as it is costly, but I will definitely save up over time.

When you say thick absorption, what is meant by this? I would think 4 to 6 inch panels (like with bass traps) is pretty thick, while you might mean something more along the lines of what Ethan was saying ("2 feet wouldn't be too much"). I think I'll stick with the thick absorption on the rear wall (it's definitely less than 10 feet from the mix point). Can you explain what you mean by thick absorption?

Lastly, I've come across articles and threads that suggest covering the entire ceiling, as opposed to just above the mix point. Is this a good idea? I know that would be more costly, but if it is really good, it could be something I build slowly over time, as funds permit.

[SörenHjalmarsson]

Originally Posted by hereticskeptic

Thanks for the links Glenn. It sounds like diffusion is something that is not meant for a DIY project.

Yes, It is far more easy to build absorbers, but you can certainly build diffusers aswell. Just search the forum and you'll see...

Originally Posted by hereticskeptic

I have to say, I am still a little lost when it comes to the rear wall, in that I've been told thick absorption is a must for my rear wall, but also that diffusion should be used on the rear wall? Does this depend on the distance fro mix point to rear wall? .

Not should be used, could be used. Yes, the method used depends on certain restrictions of the room in question, but it also depends on the desired room response. whether you like to mix in an anechoic environment or not is really a subjective matter. Good mixes have been done in rooms with completely different designs, you just have to be aware of all the different cues involved in the chosen response model i.e. Why you are doing this and why you are doing that... Note also that a diffuser has a LF cut off frequency (i.e. it will absorb aswell) and that it is possible to implement diffusion in front of absorbtion.

Just to show how different some of these approaches can be, here are some Examples of different models/designs and their fundamental basis (very briefly):

Non-Environment Rooms: This model uses absorbtion to remove early and spatial reflections, creating an effectively anechoic environment. The only reflective surfaces left are ment for creature comfort (human reflections) and not ment to influence the listening material at all.

LEDE (Live End Dead End): Removes early reflections by absorbtion, but leaves the rear part of the room hard (with diffusion) in order to attain a desirable psycho-acoustical response. i.e. the room influence what you are hearing.

RFZ: Is a furthering of the LEDE design. Early reflections are deflected past the listening position (instead of absorbed). These reflections can then be moulded in a variety of different ways, in order to achieve the desired response.

Moulton Rooms: One could say that this design is the opposite of the LEDE/RFZ. Here the early reflection are preserved in order to become desirable reflections (good data) whereas the late/spatial reflections are attenuated.

To name a few...

Originally Posted by hereticskeptic

When you say thick absorption, what is meant by this? I would think 4 to 6 inch panels (like with bass traps) is pretty thick, while you might mean something more along the lines of what Ethan was saying ("2 feet wouldn't be too much"). I think I'll stick with the thick absorption on the rear wall (it's definitely less than 10 feet from the mix point). Can you explain what you mean by thick absorption?

Originally Posted by SörenHjalmarsson

The best place to start with bass traps however is where the low frequency resonances in a room have their points of maximum pressure, which is in the corners and thus bass traps mounted in these positions will be the most efficient.

When trying to damp your modes you should know that they arise from your specific room dimensions and if you for example need to tame a mode that is due to your room hight, you would need to dampen either the floor or the ceiling (not the walls).
You can make bass traps from wool filled spaces that will absorb frequencys with a wavelength down to 4x the depth of the space. If such a trap is to absorb the lowest mode of the room, the depth of it would have to be as big as 1/2 the lenght of the room. This is because the longest mode has a wavelenght that is twice as long as the length of the room.

i.e. To tame the lowest mode of a room with the lenght of 4 Meters, you would need a wool filled space with a thickness of about 2 meters. This is why tuned membrane panels and simular devices can be preferable (they do not take up as much space). However... tuned entitys 'only' focus on the modal frequencys determined by the room dimensions, whereas broadband absorbtion will attenuate the whole low frequency range.

The difference between a straddle trap and a filled space should also be mentioned... A straddle trap will work at it's best for a certain frequency at a distance from the boundary equal to 1/4 of that frequency wavelength, but it will avoid absorbtion of higher frequencys (with a shorter wavelength). A filled space on the other hand, will absorb all frequencys whose 1/4 wavelength falls within the depth of that space.

Originally Posted by hereticskeptic

Lastly, I've come across articles and threads that suggest covering the entire ceiling, as opposed to just above the mix point. Is this a good idea? I know that would be more costly, but if it is really good, it could be something I build slowly over time, as funds permit.

Originally Posted by SörenHjalmarsson

If you have additional material to use, the ceiling is a very good place for thick/big absorbtive clouds, as these would achieve alot of trapping without eating up any floor space.

[hereticskeptic]

Hey Soren,

Nice, lengthy, informative response brotha! I appreciate that.

It seems like most people are building their ceiling clouds using 2" 703, spaced 2" from the ceiling. This is what I've planned to do, but I do notice you mentioning thick absorption on the ceiling....basically, bass trap style.

Would it be wiser to make the cloud panels a little more thick, or would covering the entire ceiling using the 2" with 2" spacing be cool?

[SörenHjalmarsson]

2" absorbtion is better suited for mid and high frequency absorbtion, so 2" would work fine for removing early reflections coming from the ceiling. Thicker is always better though, as it will not only absorb HF. To absorb any LF you need at least 4", but more would be better.

To answer your question... I would make a thicker trap in the front than cover the whole ceiling with thin absorbtion. You can use a rug to attenuate flutters in the back of the room.

Cheers,

[hereticskeptic]

Originally Posted by SörenHjalmarsson

2" absorbtion is better suited for mid and high frequency absorbtion, so 2" would work fine for removing early reflections coming from the ceiling. Thicker is always better though, as it will not only absorb HF. To absorb any LF you need at least 4", but more would be better.

To answer your question... I would make a thicker trap in the front than cover the whole ceiling with thin absorbtion. You can use a rug to attenuate flutters in the back of the room.

Cheers,

Yo you mean making a thicker trap for the ceiling at the early reflection point, and then covering the remainder of the ceiling with 2" (thin)? What did you mean regarding the rug?

[DanDan]

Unless you don't have the height available I always recommend a 4 inch cloud with a 4 inch airgap over it. This eliminates HF and MF reflections from above, but it also has a go at the height mode.
I see no downside to this.
DD

[SörenHjalmarsson]

Originally Posted by hereticskeptic

Yo you mean making a thicker trap for the ceiling at the early reflection point, and then covering the remainder of the ceiling with 2" (thin)? What did you mean regarding the rug?

I ment exactly what DD is saying. Make a small/thick ceiling cloud rather than a big/thin, it will have more chance of absorbing modal frequencys.

And no, i can't really see any reason for treating the whole ceiling with thin absorbtion, as it will only serve to remove floor-ceiling flutters (this can be achieved anyway).

Covering the ceiling with thick (4" or more) absorbtion on the other hand, will help you to decrease the hight mode.

Cheers,

[hereticskeptic]

Thanks for the pointers fellas. So I guess my next question would be, would you still keep the panel above the mix point 2" spaced 2", since it is an early reflection point, or just look at the entire ceiling as a spot where 4" with a 4" gap is ideal?

Basically, should there be a difference between how you treat the spot above the mixing point and the rest of the ceiling, or just do it all the same? I ask, because I've been told 2" with a 2" gap for the ceiling above mixing point is ideal, but would be fine doing 4" with a 4" gap.

If i did that, i would likely treat the spot above the mixing point with 4" and 4" gap, as well as the same ceiling spot in the back of the room, then continue to cover the entire ceiling over time, as funds allowed.

Also, what is height mode, if you don't mind explaining it?

[hereticskeptic]

On hat same subject, is there a certain height that is ideal for the clouds to hang?

I mean, if my ceiling is 12' high (as an example), should I be trying to hang the clouds so that they sit at 7' high....lower...higher? My current ceiling is a few inches short of 8' high, by the way.

How low is too low, and how high is too high?

[SörenHjalmarsson]

I think this article deals with all your questions.

Acoustic Treatment and Design for Recording Studios and Listening Rooms

Get back to us if it doesn't.

Cheers,

[hereticskeptic]

Originally Posted by SörenHjalmarsson

I think this article deals with all your questions.

Acoustic Treatment and Design for Recording Studios and Listening Rooms

Get back to us if it doesn't.

Cheers,

Props for posting the link bro. Checking it out right now.