John Sayers' Recording Studio Design Forum Archive

ok, my intelligence be damned, but i have a question at this point...

If your ray tracing at given angles, 10, 20, 30... this is only to give you an idea of incidence of reflection on the wall correct? but to confirm, there is no "ray", it is a continual wave, so all angles are to be accounted for correct? If so, then in my crude sketch, the blue line is probably about 35degrees... which does run through your 1ft area of concern... and if you were thinking the RFZ, then your gonna need to have a panel absorber at that first reflection point, which would be i guess anywhere between -0 and 60 degrees.... correct? I know John and others in the forum have dealt with this in the past for the window, by puttin in a heavy drape for mixing, then just open for tracking...

but am i understanding this right?

if so... then if you angle the front wall less, don't you push back that first reflection point, by aiming the speaker soffits more toward the back fo the room? is that a valid strategy? or does that kill the point of an angled soffit? what if he pushes the desk forward 1ft... it looks like your almost 50%, shouldn't ypu be somewhere like 38% or about that?

... guess i was asking both of you ?

there is no "ray", it is a continual wave, so all angles are to be accounted for correct?

Right! The "rays" just mark a few points on the continuous range of angles that a sound wave expands along. The higher the frequency the more it acts like a ray, but the lower the frequency, the more it spreads out in all directions.

If so, then in my crude sketch, the blue line is probably about 35degrees... which does run through your 1ft area of concern...

yup.

and if you were thinking the RFZ, then your gonna need to have a panel absorber at that first reflection point,

actually, no. For RFZ, the solution is to angle that section of wall more steeply, until the reflections no longer hit the mix position at all: That usually means pretty large angles, for small rooms. If you put perfect absorption there, then you could theoretically fix the problem, but of course there is no such thing as perfect absorption... There would always be some type of reflection coming back. So for true RFZ, angles is all you have.

I know John and others in the forum have dealt with this in the past for the window, by puttin in a heavy drape for mixing, then just open for tracking...

Right, but that's not for true RFZ rooms. That would be for other room concepts, not based fully on RFZ.

if so... then if you angle the front wall less, don't you push back that first reflection point,

Yes, but you shouldn't change your soffit angles to fix reflections! You should change the angle of the section of side wall where the problem is occurring. Your soffit angles and positions should be set for the basic room geometry, and shouldn't be changes unless there is no other option, as a very last resort. Sliding the speaker along the soffit face is one possibility, either left or right, but without changing the angle. Of course, that changes the location of the mix position... Don't you just love studio design? Change one tiny thing, and the entire room changes! Sometimes it seems that just turning the lights on is going to destroy the room!

what if he pushes the desk forward 1ft... it looks like your almost 50%, shouldn't ypu be somewhere like 38% or about that?

Right again!


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Since I don't have the space to angle my ceiling and planned to just add a hard-backed cloud above the mix position - is it worth conducting the exercise again for the vertical axis?

You should still do it, yes, and use the hard back of the cloud as though it were the room ceiling.

Since my room is symmetrical - do I only need to conduct this for one of the speakers? Won't the other be a mirror image?

Right. In fact, if you make your speaker, soffit and ray tracing into a component in SkethcUp, copy it, then flip it along the appropriate axis, you are all done with both! The copy will the follow exactly what you do with the original. Add a piece inside the component, change something, delete something... what ever you do on either of the copies will also be done on the opposite one, correctly mirror imaged...

Even with just the 12 degree splay and soffit mounting it would appear that none of the 1st reflections travel through the 1ft radius circle,

See above: Sandlefoot has it right. Those 10° rays just mark some of them; you have to imagine the others in between (or draw them too, if you feel like it!).

So is it worth angling the walls further or should I just treat that first reflection point? I'm guessing it would take some significant splay to angle that 50 degree reflection back behind the mix position.

Don't forget that each degree of wall angling greatly increases the the reflection angle, since you are using the surface normal as the point of reference. So a small change in the wall angle can produce a large change in the reflected ray...

Am I right in thinking that as well as having the bass traps in the rear corners I would want to make the rest of the rear wall absorptive, and / or diffuse to help dissipate or randomize those reflections?

Absolutely! The entire back wall should be absorptive. Thick.

Is there value to me adding absorption around the front wall window (between the two soffits)? It would appear that none of the primary on-axis rays appear to hit back there.

Some people do that. It can help. Your first axial room mode, for example, is associated with that front wall, as are some of the tangentials, and all of the obliques...

- Stuart -

Thanks to you both - this has really turned out to be a great learning experience and my Sketchup chops just keep on getting better. It's funny to think that only a month ago I dreaded using it and found it frustrating at best. Now I find it really quite intuitive and quick to use. I have been using a Ruby Plugin called RayTrace to help expediate this part of the process - very hand indeed. I mention this only to bring reassurance to anyone struggling with it. Perservere, practice, and you'll have it in no time. If you can edit in a DAW you can learn this I promise you.

So then, on to the topic de jour and some responses / more questions along with updates to my raytracing efforts.

I know John and others in the forum have dealt with this in the past for the window, by puttin in a heavy drape for mixing, then just open for tracking

That item on the Right hand wall is actually a LCD TV, not a window - so it can be relocated without any issue.

So on to the RayTracing...
I updated the 9 degree ray trace by adding more rays in the 40 to 60 degree area and also adjusted the circles to the 38% position (while I had previously setup the chair to be located at 38%, I forgot that I had it centered in the middle of the chair rather than the back headrest where these first circles originated from - thanks for picking that up Kevin), and then did the same ray tracing for 12, and 18 degree's to see what effect it was having.

Here is the 9 degree splay ray trace: 1st reflection issues appear to exist between approximately 41 and 55 degrees.

Now the 12 degree 1st reflection issues appear to exist between approximately 42 and 57 degrees.
Room volume decreases to 1515 cubic feet

And finally the 18 degree. 1st reflection issues appear to exist between approximately 43 and 60 degrees.
Room volume decreases to 1366 cubic feet

So from looking at these it would appear that as I increase the splay angle, the first reflections get angled further back, however - even with an 18 degree splay I am unable to fire all of the first reflections out of my 2 circles. In fact some of the further off-axis rays (55 to 60 degrees) have been brought into the circles. Further, by increasing the angle to 18 degrees I lose enough room volume that my CR is now below 1500 cubic feet (this was my minimum goal for CR volume).

So, here then would be my questions following this analysis:

• If I increase the angle to the extent that I lose room volume, should I compensate by increasing the room width? Will that throw-off, or improve my alignment to my room ratios?
• Given that most of the troublesome first reflections are coming from the further off-axis rays (41 degrees and up), and anything below that is going to the back wall - can I treat these front splayed wall areas with broadband absorbers spaced an inch or so off the wall? At approximately what angle are the off-axis rays could one consider - "it's low enough frequency so I'll live with it". I recall you mentioned the higher ~60 degrees ones are less of a concern for this reason, but is there a cross over angle? Does it depend on the speaker? I've looked at the specs for the HR824's MK1 and don't see anything. I guess I'm hoping the answer is 40 degrees is the magic crossover point to LF
• If it's not possible to create a true RFZ and I'm treating the first reflection points as mentioned in my question above - is there then much value in increasing the splay angle given that it will reduce room volume. Which would you be inclined to go with - 9, 12, 18 - something else?
• Am I right to not be concerned about my HRS120 subwoofer? I had read that it doesn't need to be in the soffit, and the frequency's are low enough that they won't be directional right? Any reason to be concerned about there being less low-end coming out of the mains in the soffits due to using this sub i.e. does any of this affect the ray-tracing? I should point out that I have the sub on a foot switch so that I can switch it on and off.
• Should I be concerned about that external window on the back wall to the left? It's really not that large, but is it going to mess up my ability to effectively treat the rear wall?

I think that about does it for my questions for now. Or at least for the ray-tracing ones at least - I have a growing list of questions that I'm saving for once I move beyond this lay-out phase, but one step at a time

Thanks so much as always and wishing you and everyone a wonderful weekend!

Andy

You are missing something rather important in your model, Andy: Your soffits! Most of those problematic rays will be hitting your soffit baffle, not the walls, and the baffle is angled at 60°...

Also, to avoid losing so much room volume, angle less of the front wall. In other words, extend the parts of your side walls that are parallel much further forwards. Now that you are ray-tracing like a pro, you can optimize the position of the point where the splay starts: it can go several feet further forward.

Am I right to not be concerned about my HRS120 subwoofer? I had read that it doesn't need to be in the soffit, and the frequency's are low enough that they won't be directional right?

Right. Directionality starts at about 70 to 100 Hz, which is more or less where your crossover point is probably set, so subs don't need to be soffited, and indeed doing so might mess things up, since may subs are ported at the back, sides, or even underneath.

- Stuart -

Hi Andy!

I'm sorry if I missed it somewhere but what are the dimensions of your CR?

If it helps at all mine are 16x14 and my design is RFZ going with soffit mounted A8x's, I splayed my side walls at 19 degrees and I have plenty of clearance in regards to no reflections around my mix position.

Allen

You are missing something rather important in your model, Andy: Your soffits! Most of those problematic rays will be hitting your soffit baffle, not the walls, and the baffle is angled at 60°

That's a fair point you make So much for that being a timesaver!

Ok, so I will go look at them again with the baffles. I thought that the baffles were angled at 30 degrees though? Or are you saying 30 degrees for each baffles which gives a total of 60 between the two them?

Also, to avoid losing so much room volume, angle less of the front wall

That thought had crossed my mind earlier today, although I was considering starting the splay steep, say 18 degrees and then making it less steep, say 9 degrees. I much prefer your plan though!

I'm still wondering about a couple of these questions though - even after I add the baffles back in and adjust where the splay starts - I'm still interested to know whether I should compensate for increased splay by increasing the room width in an attempt to keep the room volume the same? That was what I had done previously.

I also wondered if I should be concerned about the external window on the back wall to the left? Since you likely can't access my skp file still, let me add a jpeg below: Many thanks again Stuart. You are a wonderful teacher - I am learning so much at the moment and am very grateful indeed.

Allen - I just looked again at your thread and will be trying something just like this as Stuart suggests. My dimensions here are 17'5 x 12'6 x 7'6. Originally the room width was 12ft exactly which was based on Sepmeyer3 - 1:1.6:2.33, but after splaying the walls I increased the width of the room slightly to get the volume back up to that of the rectangular room volume. I hope that was the right thing to do! Keep up the great work and great to hear from you.

Andy

Andy,

my .02c...

Also, to avoid losing so much room volume, angle less of the front wall

I'm still wondering about a couple of these questions though - even after I add the baffles back in and adjust where the splay starts - I'm still interested to know whether I should compensate for increased splay by increasing the room width in an attempt to keep the room volume the same? That was what I had done previously.

In my non-expert opinion, room volume would be a secondary concern over room shape / ratio... i believe the room volume can be a good indicator of the total amount of room the sound has to begin to dissipate before being reflected... in rod's book, he gives some generalization about room volume, but it's kind of in the context (pulling from memory, the books at home)... that larger rooms are just easier to treat acoustically... but says something along the lines of a 'small room correctly treated can sound better than a large room (even in the golden ratio) not treated... '

i was also concerned about the ratio, and had read stuart mention in a post, that the ratio's suggested are good because they stay away from the bad ratios (like 1x1x1), so i think you have flexibility in your room....

I keep coming back to using a door in front setup, and removing the airlock... I know this gets close to a square ratio, but it would allow you to splay the entirety of both side walls, which sort of mitigates some of that... plus, you can keep the side walls in 1ft on each side, so you'd end up with a room of 8'x18'x16' but 16'splayed walls...that go from 16ft to 14ft?? this could help you with your current problem where your first reflection is close to your mix position... without doing a ray trace, i'd almost bet that if you pushed the walls out, you wouldn't worry about first reflections before 50degrees or more...

I'm sure you've seen this room mode calchttp://www.bobgolds.com/Mode/RoomModes.htm, but if you use the "average" of the splayed wall, the room isn't terrible 7'10"x18'x15' .... obviously some tweaking would be in order, but...

just a thought...

I also wondered if I should be concerned about the external window on the back wall to the left? Since you likely can't access my skp file still, let me add a jpeg below:

as for the back windows, I wouldn't worry about them too much, for several reasons... it's a hard surface, similar to the other side of the rear wall, except glass, not drywall...your not likely to be able to completely remove it... you'll most likely be treating the entirety of the rear wall in some absorbtive setup, so at that point, you can address it like you will on the other half of the wall... if you are worried about keeping it accessible, again, a removable panel of sorts for the times you are not mixing may do the trick... if your worried about isolation, then creating a 'plug' of sorts may work... black painted drywall up against the glass might help.... trying to remember the studio on the forum i just saw do that... i'll have to post the link after i find it...



kevin

I thought that the baffles were angled at 30 degrees though?

Right! It sure is 30° measured from the FRONT wall, . . . which is 60° when measured from the SIDE walls...

Like this:
It's as though you took your side wall and turned it 60°, so the bounce angle is huge for your ray-tracing.

I was considering starting the splay steep, say 18 degrees and then making it less steep, say 9 degrees.

You could do it that way too. There's even a slight advantage to that, acoustically, but it does complicate construction quite a bit more. Probably better to just keep one angle.

I'm still interested to know whether I should compensate for increased splay by increasing the room width in an attempt to keep the room volume the same?

If you can increase the width a bit, that would be good, but I have a feeling you don't have enough space to do that: that passage outside the room would become too narrow to be comfortable/useful.

I also wondered if I should be concerned about the external window on the back wall to the left?

It's fine: no big deal. It's not a big window, it is high up, and is not going to be reflecting much back at you. You could probably even fit a small horizontal superchunk across the top of that wall: Set it in the middle and make is roughly symmetrical, stopping at an imaginary window in the same place on the other side.

- Stuart -

I keep coming back to using a door in front setup, and removing the airlock...

Good idea! I hadn't thought of that, but it makes a lot of sense.

I'm also with you 100% on the room volume and room ratio comments.


- Stuart -

ok,

so this is rough... i'm finding the limits of my home designer software... and drawing angles is apparently one of them... so i can't measure angles... but this is close and should give you an idea of what i'm talking about... this is a blatant copy of John's SAE "Control Room" sample plan under the is forum... now, the dimensions for your room are a bit smaller, so this might not work exactly, but I think its close enough to make it work...

my sketch is kinda rough, but you get the idea...

again... i know that walkign around the desk wouldn't thrill me, but, its a workable plan within the limitations you have... and if your soffit mounting the monitors... there shouldn't be a problem with cables and cords and such... so you should be able to have a 3ft or so walkspace between your desk and the doorway...

what do you think?

kevin

Hey Guys,

I'm back to the drawing board and trying to find an RFZ design that will work. Thanks so much Kevin for taking the time to draw out that idea. I'm really hoping not to do the SG door unless it's absolutely necessary. The main factors being a) I don't like people walk around behind the desk (risk of damaging equipment, and it's quite annoying when you're working and people are coming and going), and b) I don't think the isolation to the drum room would be as good.

So I've been playing with various factors, moving the splay start a few feet further back as Stuart suggested, adjusting the splay angle, and I'm finding that in order to get a true RFZ I will likely need to increase the width of the room and say to hell with Sepmeyer 3. This is to ensure I have enough space between the speakers for my 4ft wide window. I have been using Bob Golds calculator right from the get go on these design attempts to get a feel for how the room might behave (if it were rectangular) and have found that adjust the width (within a certain extent) actually does not appear to have a substantially negative effect.

The other design consideration that's been bouncing around my noggin is whether to forgo the window in favor of my large LCD TV. Since a large part of what I do is video-streamed live - it might make sense to have the monitor placed here for me (and other sitting on the coach at the room rear) to see. Keep in mind that each room will have a number of camera's so having a window isn't actually a necessity for me since I can call up any camera, and pan, tilt, or zoom it. I asked a couple of clients if they would prefer privacy, or the ability to see the producer and their response was they like being able to see the producer when needed (I typically set them up so they don't look at me and need to turn around if they want to see me).

So not really much development - just ongoing questions and design attempts. I would be interested to hear anyone's thoughts on these factors - especially opinions around having the window vs. monitor.

Many thanks and more sketches to come soon.

Andy

I have been using Bob Golds calculator right from the get go on these design attempts to get a feel for how the room might behave (if it were rectangular) and have found that adjust the width (within a certain extent) actually does not appear to have a substantially negative effect.

Right! That's one of the reasons why it isn't necessary to chase perfection in room ratios. My normal recommendation is just "stay away form the bad ones, get close to a good one, and that's it!".

Here's another curve ball to add to your mix of tools for designing your room: Download the very latest version of REW. There is a "room simulator" option in there now, that actually predicts the frequency response graph for your room, based on the dimensions, the treatment on each wall, and the position of your head and your speakers within the room. Initially it is set up for only one sub, but you can add more speakers and adjust their position and frequency cut-off, to simulate your setup better. It only predicts up to 200 Hz right now, but that's all you need for most rooms. It's pretty darn amazing!

- Stuart -

Thanks for sharing that Stuart- that sounds like a very useful update that they've made - I will definitely be downloading and checking that out.

So do you fancy sharing your thoughts on the Window vs. LCD TV Debate I'm having?

The other design consideration that's been bouncing around my noggin is whether to forgo the window in favor of my large LCD TV

my thought is... let me know how that turns out, cause i'm thinking the same thing! But, I was thinking that it may be a cheaper option, than putting in an actual window... and depending on my final layout, I may not have visual sight lines to all booths anyways... you may have a similar circumstance, where you are looking through a room to see the first room... a video monitor may help solve some of those sighting issues, and may be a cheaper option... depending on the tv,camera etc...of course. A wood-framed drywall is going to be cheaper than the plate glass window, especially at the thickness and size we use in the studio world...

thats my .02c on the lcd vs window...

as for the layout, i'm also playing with a very similar sized control room, so i'm curious to see what you end up with...

kevin

Hey Kevin!

In my case I already have the window (salvaged from my last build) and already have the PTZ camera's etc since I do a lot of live streaming - so the cost of either is not a factor.

As for sight lines, well if I'm able to go with the CR window facing into the booth and a large patio door / wall as per my recent Sketchup plans I think I could get pretty good sight lines. Of course if I end up adding the vocal booth to the right of the CR I could always use the window there instead.

Decisions decisions... and a welcome distraction from many days of reading Newell, various build threads, and trying yet more designs in Sketchup At some point I have to say f it - let's build - as I have a couple of clients (one quite well known) waiting for it's completion. That and the fact that my poor wife will only tolerate my studio gear filling up the dining room for so long! Cheers for now,

Andy