Determining reflection points for sound treatment locations

nooshinjohn

I am certain this was discussed somewhere... I am planning the location and types of sound treatments needed for my new man cave. What I have now is decent sound at lower volumes that quickly becomes a jumbled hot mess when I try and unleash the beasts.

The room measures 19 feet on the long wall by 15feet on the short one. The speakers are 46 inches off the side walls and 80 inches apart on the long wall. The ceilings are 94 inches. The seating area is 9 feet back and centered.

Any advice will be most appreciated.

Joey_V

I think it is difficult to pinpoint a single first reflection point, I think it's a mass of sound wave that hits the side wall and goes to hit your ears. I am treating as much of the side walls, rear wall as I can. I am also going to put up 2 panels between the speaker and me as CLOUDS.

Then I am also adding absorptions behind the front stage to help soak up extra reflection points - however, I know that some people advocate diffusors up front.

tratliff

John - You may want to give the guys at GIK a call. I worked with them to put a plan together. I have not purchased yet but have the recommendation from them on what they would do ideally. They requested pictures of the room showing the system, seating location and side walls. Then provided me a plan of action. They were very responsive. The one thing that really surprised me about the services they provide is that they did not just want to sell me a bunch of panels and corner traps but logically work thru a process.

Joey_V

My stuff is through GIK also.

deucekazoo

I have heard a laser pointer works nicely to get the reflection points. Just position it on top of speaker and go from there.

[Deleted User]

Have your wife walk hold them like "round" cards in boxing.
Of course if see looks at the speakers it changes things.
(Heisenberg Uncertainty Principle)

EndersShadow

Sit in the main LP. Give your wife a mirror and have her walk along the wall with you watching the mirror. Any location you can see the left or right speaker needs treatment.

You have 2 first reflection points per wall. One where you see the right speaker, one where you see the left.

vc69

EndersShadow wrote: »

Sit in the main LP. Give your wife a mirror and have her walk along the wall with you watching the mirror. Any location you can see the left or right speaker needs treatment.

You have 2 first reflection points per wall. One where you see the right speaker, one where you see the left.

Bingo! and plus 1 on the GIK call. Great folks.

Polkie2009

EndersShadow wrote: »

Sit in the main LP. Give your wife a mirror and have her walk along the wall with you watching the mirror. Any location you can see the left or right speaker needs treatment.

You have 2 first reflection points per wall. One where you see the right speaker, one where you see the left.

Enders is spot on, this will work. If you use diffusers, you'll have to experiment a bit , also you may want to check out using REW (room eq wizard) software with a calibrated mic . Lots of info at website and on AVS forum. GIK and RealTraps are both excellent outfits and very helpful.

Joey_V

The mirror idea is a good idea.

codyc1ark

^ you just leave that math wizardy at home why don't ya'

voltz

^^^^^^
LOL, can you post that in Geometry? I'm not very good at Algebra.

vmaxer

Ken once told me the exact thing to do with a mirror. Try it.

Joey_V

Honestly, I don't think it's as simple as what Skip wrote up there, unless I'm missing something. We are not accounting for first reflections coming off the contralateral wall from the opposing speaker. Not to mention, we are also neglecting first reflections off the ceiling thus cloud installation is important.

And floor as well.

But I do like the drawing and all the formulas he included, a throwback to my 9th grade geometry class.

PSOVLSK

Yep, and you can overdo it as well. It's not like you're gonna cover the entire walls and ceiling with sound panels.

The formula's not too complicated...I tried it previously, but my room doesn't allow me to put my panels where they truly need to go.

Joey_V

DSkip wrote: »

The reflections you are speaking of are not first reflection points. They are additional reflection points.

No, that's a very narrowed and simplified version of 1st reflection points.

[Deleted User]

Reflection points will become infinite at this point. There will a,ways be reflection points, unless you move that section.

Halen

SCompRacer

Joey_V wrote: »

DSkip wrote: »

The reflections you are speaking of are not first reflection points. They are additional reflection points.

No, that's a very narrowed and simplified version of 1st reflection points.

If anyone would follow Dan's advice, the right speakers reflection points on both side walls would be covered. And the same for the left speaker. Skip's diagram appears to just treat right and left speaker first reflection, not the right speaker on left wall and vice versa. Any additional listening positions have to be treated as well.

If you have a low ceiling, that too. GIK rocks. I use four bass of their traps and three 244 panels in my room. Great choice of custom fabrics.

https://youtu.be/B9u7k2V4YPw

Joey_V

DSkip wrote: »

The same formula can be used for any of these as every single reflection point creates two similar right triangles, which allow us to use the proportions I used in the formula. Its just a matter of tweaking it.

For some reason, I thought it was just talking about first reflection points. The opposite wall is a secondary reflection point, at least as I understand it. I wasn't saying those spots aren't important (Joey, you've seen my room and know this is true), I just thought it was first reflection points only.

Hey Skip,

I'm not saying that you do not find the other first reflection points not true/important especially since I've seen your room - and that you've treated for such. However, I think there is some misunderstanding regarding first reflection points.

First reflection points are any points at which the speaker primary reflects from and that does not only include the ipsilateral wall but also the contralateral wall, rear wall, and perhaps front wall. Those are all first reflection points. Second reflection points are points at which reflections are one-removed from the speaker i.e. points that reflect after already being reflected once. Third are one-removed from that... and so on.

The question is not whether you find the other first reflection points important or not, the question is whether or not your initial diagram encompasses the other first reflection points.

BlueMDPicker

DSkip wrote: »

This was done quickly, but if you're good with numbers, you just need a few measurements. This works due to similar triangles and their ensuing proportions. The rest is algebra.

Hi DSkip,

Using your sketch and math (thanks, BTW), does speaker toe-in change the "b and d" measurement methodology? Would those dimensions be measured in the same plane as the speaker front panel for my toed-in electrostats? Thanks!

ZLTFUL

BlueMDPicker wrote: »

Hi DSkip,

Using your sketch and math (thanks, BTW), does speaker toe-in change the "b and d" measurement methodology? Would those dimensions be measured in the same plane as the speaker front panel for my toed-in electrostats? Thanks!

Short answer, yes. To all of it.

It is a bit more complicated than that but the general rule of thumb is to base it off of the face of the speakers. This is because your toe-in changes the dispersion angle's "angle of attack" if you will.

BlueMDPicker

ZLTFUL wrote: »

BlueMDPicker wrote: »

Hi DSkip,

Using your sketch and math (thanks, BTW), does speaker toe-in change the "b and d" measurement methodology? Would those dimensions be measured in the same plane as the speaker front panel for my toed-in electrostats? Thanks!

Short answer, yes. To all of it.

It is a bit more complicated than that but the general rule of thumb is to base it off of the face of the speakers. This is because your toe-in changes the dispersion angle's "angle of attack" if you will.

Thanks @ZLTFUL! I re-calculated, based on this new knowledge, and it did move the panel locations over a foot. Much appreciated.

polrbehr

Why bother, all amps sound the same anyway, even those tubed beasts of yours.

Headphones = Done

BlueMDPicker

While the cat's away...............

This will never fly with my wife (who is shopping with the kids at the moment). But, it's been fun experimenting with DSkip's drawing and formulas. Results so far: getting a more open and detailed image with the first reflection point on each side treated. The second point (and I want to state right here math was not my major), extrapolated from the dimensions of the first triangle, seems to create a LF room node and (for the first time I ever noticed) some tone arm resonance on my TT. I tamed an initial room node when I got the ESLs by adjusting my sub (thanks to Rich for putting me on the right path). This doesn't sound like the same node frequency, and I never experienced tone arm resonance. So, I'm pulling the second point panels and moving them to the back wall of the room. Big fun!

SCompRacer

BlueMDPicker wrote: »

While the cat's away...............

This will never fly with my wife (who is shopping with the kids at the moment).

Yeah, I get away with extra placement for get togethers...lol Fortunately only the left wall needs side treatment higher than the wife's cushy recliner.

.... (for the first time I ever noticed) some tone arm resonance on my TT.

With this south wall setup, there was no way gear with turntable could be between the speakers. Anything above 70dB would cause awful feedback. West wall setup where right speaker is not boxed by corner, no problems with gear/turntable between speakers.

More than a few folks were surprised with what them ten inch SEAS woofers in eight foot folded transmission line bass modules could do on the Eros ESL's. They even got their own 600WPC @ 4 Ohms amp.

BlueFox

Don't forget the ceiling and floor. I'm lucky in that my ceiling has a wooden beam across the first reflection point, and (ugly, but effective) carpet on the floor. My left side has a fireplace, mantel, and CD rack at it, while the right side opens into the kitchen, dining room. My living room is almost a natural stereo room. The ceiling behind the speakers is 12' high, and slopes to 8' on the wall behind me. Late at night when the ambient noise level is low I feel as if I am Magico listening to the S7 in their designed listening room.

leftwinger57

Guys, certain things I grasp really easily and this one I do not at all. Maybe because my listening room is smaller 18'x15' w/ the 2Bs at a 7' spread and my couch 9' feet away making it almost an equilateral triangle and firing straight dead on to me. I have area rugs and a poofy couch and some pictures on sheet rock walls. What surfaces are most effected and is it the size of the room that's the main culprit, windows or vaulted ceilings or just the flow of the house. Not denying this problem I just do not know if given a problem house and was told Lew find the reflection point, I don't know if I could do it. I did read once in Stereophile magazine that I think Julian Hirsch actually did use sound treatments on his ceiling. But being that's his job and to have the most neutral house sound wise I guess he had to do the full monty.

BlueMDPicker

SCompRacer wrote: »

With this south wall setup, there was no way gear with turntable could be between the speakers. Anything above 70dB would cause awful feedback. West wall setup where right speaker is not boxed by corner, no problems with gear/turntable between speakers.

I suppose I may have created a virtual corner on the right with the tri trap stack?? That side's rear dipole reflection point was formerly down the hallway, while the left was boxed by a wing wall. The weird science is the fact I didn't observe any resonance issues with my TT until I started trying to find and attenuate the first reflection point for the opposite channels.

SCompRacer wrote: »

More than a few folks were surprised with what them ten inch SEAS woofers in eight foot folded transmission line bass modules could do on the Eros ESL's. They even got their own 600WPC @ 4 Ohms amp.

I dialed the bass setting back to 5 (from 7) on the crossover/bass amp using the opening track of "Dark Side of the Moon" LP as a reference. That eliminated the resonance issue, but seemed sonically unbalanced (for lack of a better term). Then, ran out of "lab time" when the family returned.

I'm going to take the sub out of the mix when I get another testing opportunity. Beginning to think it's no longer required.

BlueMDPicker

BlueFox wrote: »

Don't forget the ceiling and floor. I'm lucky in that my ceiling has a wooden beam across the first reflection point, and (ugly, but effective) carpet on the floor. My left side has a fireplace, mantel, and CD rack at it, while the right side opens into the kitchen, dining room.

I agree both are factors for sure. Before we made the move to Florida, this was a second home for over a year and sparsely furnished. With the marble tile flooring, windows and glass doors down both sides, and the hard wall surfaces, this room felt like an echo chamber--to the point people would comment about it when I used my cell phone sitting in there. More furnishings, art work on the few wall spaces not glass, and three oriental rugs help a lot. WAF and, for that matter, my tastes won't see anything suspended from the ceiling.

SCompRacer

BlueMDPicker wrote: »

I suppose I may have created a virtual corner on the right with the tri trap stack?? That side's rear dipole reflection point was formerly down the hallway, while the left was boxed by a wing wall. The weird science is the fact I didn't observe any resonance issues with my TT until I started trying to find and attenuate the first reflection point for the opposite channels.

I don't think stacked Tri Traps would cause the issue, but I could also be wrong. My 14' ceilings help by removing issues a lower ceiling would introduce. I think you get a pass there with high ceilings. IIRC GIK had suggested stacking a third trap in the corners of my south wall setup due to the bass problems of boxed corners. Maybe send them the pic and get their input.

Unlike higher frequencies bass radiates in all directions. It has length and maybe by moving things you set up the perfect spot for it to collect/amplify instead. You may have to do a bass walk and map out where it is and isn't. Moving a sub or speaker inches will determine whether I can hear low bass in my listening position or if it cancels out. I do have a small corner chimney wall by the right speaker like you do with more space to right for bass to escape. I'd like to trot down that hallway of yours to the right and hear the bass down there.

Regarding your sub, much depends on the music you play and what your rooms does with it. I do a room sweep and if I have low frequencies lacking in the type of music that I play, I'm going to supplement it. I've had folks comment that I don't need subs, but they are not on all the time. To me subs are not a personal choice or taboo in two channel, their use is dictated by the type of music you play and how low bass interacts in your space. I've got 10,000+ cubic feet to fill. Never had one pair of speakers do 25-35Hz low bass without help to get it in that +-3dB range. I don't just want a hint of what's there, even if it's just 10% of the time.

EDIT: I keep recalling visiting a Martin Logan user nearby. He had a small listening room that was fully covered with Owens Corning treatment covered with speaker fabric. He tried a pair of Sanders speakers, much like your Eros. Low bass mostly disappeared in the room, which elicited some negative comments of their bass capability. I walked into the hall and living room and there was this magnificent rich articulate bass. That situation has forever stuck with me.

BlueMDPicker

SCompRacer wrote: »

Unlike higher frequencies bass radiates in all directions. It has length and maybe by moving things you set up the perfect spot for it to collect/amplify instead. You may have to do a bass walk and map out where it is and isn't. Moving a sub or speaker inches will determine whether I can hear low bass in my listening position or if it cancels out.

I think I may have let the perfect imperfection genie out of the bottle when I shifted everything left (towards the wing-walled boxed corner) to approach aesthetic symmetry.

SCompRacer wrote: »

Regarding your sub, much depends on the music you play and what your rooms does with it. I do a room sweep and if I have low frequencies lacking in the type of music that I play, I'm going to supplement it. I've had folks comment that I don't need subs, but they are not on all the time. To me subs are not a personal choice or taboo in two channel, their use is dictated by the type of music you play and how low bass interacts in your space. I've got 10,000+ cubic feet to fill. Never had one pair of speakers do 25-35Hz low bass without help to get it in that +-3dB range. I don't just want a hint of what's there, even if it's just 10% of the time.

Wish I had the equipment (and knowledge) to do an accurate sweep. I downloaded the software from Home Theater Shack sometime ago and tried to use it with my RS meter, but got lost in the tall grass and gave up. My listening leans heavily to 3 or 4 piece blues rock. The bass and drums are the heartbeat of it and I find the sub gives me the low bass foundation that brings it to life. The room volume is nearly 13k cubic feet as well.

I'll have to keep nudging things about and being patiently critical I suspect.

SCompRacer wrote: »

EDIT: I keep recalling visiting a Martin Logan user nearby. He had a small listening room that was fully covered with Owens Corning treatment covered with speaker fabric. He tried a pair of Sanders speakers, much like your Eros. Low bass mostly disappeared in the room, which elicited some negative comments of their bass capability. I walked into the hall and living room and there was this magnificent rich articulate bass. That situation has forever stuck with me.

Lol! Sandy and I both commented this morning, while listening to Natalie Merchant's 'Ophelia', that the best bass was 45 feet away from the plane of the speakers/sub in the kitchen. Go figure?

As usual, thanks for all your insights!