First reflections and back wall - 4 question I need help with please.

[Reminiscent Audio Guy]

Hello.....

1. Thank you to all that can help - I cannot thank you enough. I did my learning, contacted acoustic company - response automated/generic.. I need your suggestions.
2. Two Channel listening: I nailed the speaker/listening position set up and I have achieved a soundstage and center imaging - wow! I am impressed I did it. Thank you to all the contributors!!!

3. 4 questions I need help with but first - Room: split level apartment - living room is recessed and open to main level, Left long side windows/balcony doors - full curtain treatment. Right side - wall extends 4.5'form back wall and then its 3'of half a wall - upper half is an open kitchen bay window. Fully carpeted - entire apartment. Jpeg included.

#1. Do I treat first point reflections on sidewall that is only half a wall - pic included. First reflection points(using mirror method at tweeter level) are 2" below half wall - meaning above the reflection points its an open bay window. If so with a 2D or 3D diffuser? and do I put absorbers or thick "bass absorber" on the side wall behind the speaker? Jpeg showing speaker and kitchen window.

#2. Do I use a Diffuser at first reflection points on ceiling?

#3 Do I hang diffuser on the Tv which is mounted on the front wall or beneath the Tv or sides or all three?

#4 Should the exercise bikes be parallel to the wall(jpegs) or horizontal placed behind speakers(jpeg)? Speakers are 4'from front wall and 1 foot from side wall and curtain on other side. Bikes at horizontal position are 2'feet behind speakers. I thought the bikes would defuse the reflections.

I apologize if I included too many pictures, I figure it would help to show what the room looks like. Lastly, the sound sounds really good - no sub just full range speakers but I am sure some muddiness from certain tracks might be due to lack of treatment.



Thank you all.
Best regards,
Gary

 

[Keith_W]

If you are happy with the sound, then there is no need to do anything. You already have a room with a lot of scattering surfaces, there is no need to clutter it up even more.

Re: the bikes. They are behind the speakers so they would be seeing mostly bass frequencies. Long wavelengths would diffract around the bikes as if they weren't there.

If you really want to do something, then I suggest you examine your Energy-Time Curve (ETC). My guess is that you will see a jungle of reflections with no obvious peak which will tell you that your room is already scattering sound. If you do see a peak, then you need to figure out what it causing it. This is done by working out the time delay of the peak to the main impulse, converting that to distance with the speed of sound equation, and looking around your room with a tape measure to see what is causing it. Then slap something temporary over there (e.g. a pillow or mattress) and re-measure and see what happens to the peak.

You could also aim to make the room as symmetrical as possible. In your case, the left side of your room is semi-open and the right side is enclosed by a window. You could cover the whole thing up with a huge diffusion panel but it would impact the aesthetics of the room too much. It would make the kitchen feel dark and claustrophobic.

 

[goat76]

I think you should put the guesswork aside if that is possible…

The most strategic way to go about this is to first measure your room with REW (one speaker at the time), analyze the “Filtered IR” graph which will show you the first reflections going on in your room, and then using a measuring tape or something similar to calculate where those reflections points are in your room. The x-axis of the IR graph will show you the delay of the first reflections in milliseconds.

1 ms delay is roughly 1 foot in sound traveling time, so you can fairly easily calculate the extra traveling time it took for the reflected sound to reach the microphone at the listening position, and by that figuring out where each reflection point are in the room. You should be able to figure out what reflections are coming from the left wall, right wall, the back wall, the front wall, the ceiling, and the floor. By looking at the y-axis in the IR graph, you can see which ones of the first reflections that comes in louder than about 20 dB under the direct sound from the speakers, these should probably be the ones you should focus on first.



It’s not long shot to think that the side walls are the worst offenders in your room as the speakers are positioned rather close to them, so I would guess that absorption panels, with broadband coefficients, positioned at the reflection points at each side wall would be the first thing I’ve would focus on. But try to make measurements first if that’s possible, these things should not be based on guesswork in the same way as you don’t apply EQ adjustments based on hunches.

 

[Pareto Pragmatic]

I would measure each speaker and see what I have going on in terms of asymmetrical responses, then eq each speaker separately in that space. As my first step. But just on the fly...

Do I treat first point reflections on sidewall that is only half a wall

Given a full wall on the other side, I would say no. You will get more reflections from the full wall, and fewer from the half wall. I think treating the short wall might make things worse.

Do I use a Diffuser at first reflection points on ceiling?

Generally a good idea to treat ceilings, so maybe a "cloud" with some absorption and an air gap above it would help. If I were going to try diffraction, I might use something with angles to bounce it to the stereo left, out of the main listening area. That might be better than scatter things into the main listening space.

Do I hang diffuser on the Tv which is mounted on the front wall or beneath the Tv or sides or all three?

I'd leave this alone for now. But I can see, given your speakers are pretty straight into the room, a back to front reflection issue. I think you would be better off thinking about the back wall than the front.

In my room I can get a lot of high frequency ringing if I don't toe my speakers in. Shiny back and front walls, stuff just bounces back and forth a lot when I go no toe.

If that screen (?) on the back was on a pivot, I would try angling it to the other parts of the apartment when listening to music, send it out of the listening space to hopefully die.

Should the exercise bikes be parallel to the wall(jpegs) or horizontal placed behind speakers(jpeg)?

I don't see this as a huge issue, but those bikes do have more surface area than a real bike. The wheels are solid, panels. They will do something. Try checking by ear. Put them parallel to the back wall, then at an angle, see if you hear a difference with some well known music. Maybe you will, maybe not.

They will reflect some sound, but who knows how much or at what frequencies? Without measurement that is.

Given two bikes, I'd not worry, whatever they are doing is likely fairly symmetrical in effect. That's a last step in the process concern, if that.

 

[dualazmak]

The most strategic way to go about this is to first measure your room with REW (one speaker at the time), analyze the “Filtered IR” graph which will show you the first reflections going on in your room, and then using a measuring tape or something similar to calculate where those reflections points are in your room. The x-axis of the IR graph will show you the delay of the first reflections in milliseconds.

I too sometimes use REW's wavelet analysis (old version REW, ms delay on Y-axis) after "validation" with my audio gears and DSP software in my room acoustic environments (e.g. ref. #17, #18, #20, #21, #22, #23 on my project thread).

I also applied my rather primitive method to identify the primary sound reflection plane/wall; just for example, if you would be interested, please visit my post #498 on my project thread;
- Identification of sound reflecting plane/wall by strong excitation of SP unit and room acoustics: #498

BTW, I am very much interested in your astronomical telescope, it is right?

 

[Reminiscent Audio Guy]

I would measure each speaker and see what I have going on in terms of asymmetrical responses, then eq each speaker separately in that space. As my first step. But just on the fly...



Given a full wall on the other side, I would say no. You will get more reflections from the full wall, and fewer from the half wall. I think treating the short wall might make things worse.


Generally a good idea to treat ceilings, so maybe a "cloud" with some absorption and an air gap above it would help. If I were going to try diffraction, I might use something with angles to bounce it to the stereo left, out of the main listening area. That might be better than scatter things into the main listening space.


I'd leave this alone for now. But I can see, given your speakers are pretty straight into the room, a back to front reflection issue. I think you would be better off thinking about the back wall than the front.

In my room I can get a lot of high frequency ringing if I don't toe my speakers in. Shiny back and front walls, stuff just bounces back and forth a lot when I go no toe.

If that screen (?) on the back was on a pivot, I would try angling it to the other parts of the apartment when listening to music, send it out of the listening space to hopefully die.



I don't see this as a huge issue, but those bikes do have more surface area than a real bike. The wheels are solid, panels. They will do something. Try checking by ear. Put them parallel to the back wall, then at an angle, see if you hear a difference with some well known music. Maybe you will, maybe not.

They will reflect some sound, but who knows how much or at what frequencies? Without measurement that is.

Given two bikes, I'd not worry, whatever they are doing is likely fairly symmetrical in effect. That's a last step in the process concern, if that.

Thank you Pareto for answering my questions so detailed I really appreciate that. I learned from your responses.
Just one question pertaining to. "Given a full wall on the other side, I would say no. You will get more reflections from the full wall, and fewer from the half wall. I think treating the short wall might make things worse." The long side is window and balcony door covered in thick curtains, do I still not treat the short wall given the other side is not wall but curtains? Thank you.

 

[Reminiscent Audio Guy]

I think you should put the guesswork aside if that is possible…

The most strategic way to go about this is to first measure your room with REW (one speaker at the time), analyze the “Filtered IR” graph which will show you the first reflections going on in your room, and then using a measuring tape or something similar to calculate where those reflections points are in your room. The x-axis of the IR graph will show you the delay of the first reflections in milliseconds.

1 ms delay is roughly 1 foot in sound traveling time, so you can fairly easily calculate the extra traveling time it took for the reflected sound to reach the microphone at the listening position, and by that figuring out where each reflection point are in the room. You should be able to figure out what reflections are coming from the left wall, right wall, the back wall, the front wall, the ceiling, and the floor. By looking at the y-axis in the IR graph, you can see which ones of the first reflections that comes in louder than about 20 dB under the direct sound from the speakers, these should probably be the ones you should focus on first.



It’s not long shot to think that the side walls are the worst offenders in your room as the speakers are positioned rather close to them, so I would guess that absorption panels, with broadband coefficients, positioned at the reflection points at each side wall would be the first thing I’ve would focus on. But try to make measurements first if that’s possible, these things should not be based on guesswork in the same way as you don’t apply EQ adjustments based on hunches.

Thank you. I appreciate the advice.

If you are happy with the sound, then there is no need to do anything. You already have a room with a lot of scattering surfaces, there is no need to clutter it up even more.

Re: the bikes. They are behind the speakers so they would be seeing mostly bass frequencies. Long wavelengths would diffract around the bikes as if they weren't there.

If you really want to do something, then I suggest you examine your Energy-Time Curve (ETC). My guess is that you will see a jungle of reflections with no obvious peak which will tell you that your room is already scattering sound. If you do see a peak, then you need to figure out what it causing it. This is done by working out the time delay of the peak to the main impulse, converting that to distance with the speed of sound equation, and looking around your room with a tape measure to see what is causing it. Then slap something temporary over there (e.g. a pillow or mattress) and re-measure and see what happens to the peak.

You could also aim to make the room as symmetrical as possible. In your case, the left side of your room is semi-open and the right side is enclosed by a window. You could cover the whole thing up with a huge diffusion panel but it would impact the aesthetics of the room too much. It would make the kitchen feel dark and claustrophobic.

Thank you Keith! lots of good info here.

 

[Pareto Pragmatic]

Thank you Pareto for answering my questions so detailed I really appreciate that. I learned from your responses.
Just one question pertaining to. "Given a full wall on the other side, I would say no. You will get more reflections from the full wall, and fewer from the half wall. I think treating the short wall might make things worse." The long side is window and balcony door covered in thick curtains, do I still not treat the short wall given the other side is not wall but curtains? Thank you.

I think you might find a full curtain wall to be pretty close to the half wall. Without measuring, hard to say. The half wall will have effectively GREAT treatment above it.

As it stands I think the short wall is "treated" to some extent, with things and what looks like a fabric hanging? Is it open on bottom, just railings? Really, measuring is a good idea (short and long term). But I would leave it for the moment. And I do have things I use when I don't feel like breaking out the mic that might help.

Here's a quick test. Miles Davis, Kind of Blue, the first track is So What. I have found the first trumpet solo (around 2 minutes in), which should be dead center is very sensitive to left right imbalances and room asymmetries. Play that. If the trumpet is left of center, you have more coming from the left. If right, more from the right. That will give you a rough idea of how the balance of your sidewall reflections is at it stands.

BTW, if I did not consider how you might live your life (AV/screens), I would suggest setting up on the curtain wall and seeing how that works. Maybe angle it VERY slightly up. I'm not sure how it would work, and I am really not sure how wide you could get the speakers without losing center image. If I did this, I would use stand mounts and put the chairs on sliders for easy adjustment. But then I have different speakers for AV and music, so that would be easy for me.

 

[goat76]

I thought the main question here was about the first reflection, and that will be equal as strong even if it's not a full wall as the first reflection point is there anyway as can be seen in the pictures.

I think you should test putting mattresses or something similar at the first reflection points on both side walls (one behind the curtain), and then listen for a while if you find it better. I think you will get a more focused sound if you treat those reflections as they are probably rather strong at that short distance.

But again, measurements would be helpful to make sure what is going on in the room.

 

[Reminiscent Audio Guy]

I think you might find a full curtain wall to be pretty close to the half wall. Without measuring, hard to say. The half wall will have effectively GREAT treatment above it.

As it stands I think the short wall is "treated" to some extent, with things and what looks like a fabric hanging? Is it open on bottom, just railings? Really, measuring is a good idea (short and long term). But I would leave it for the moment. And I do have things I use when I don't feel like breaking out the mic that might help.

Here's a quick test. Miles Davis, Kind of Blue, the first track is So What. I have found the first trumpet solo (around 2 minutes in), which should be dead center is very sensitive to left right imbalances and room asymmetries. Play that. If the trumpet is left of center, you have more coming from the left. If right, more from the right. That will give you a rough idea of how the balance of your sidewall reflections is at it stands.

BTW, if I did not consider how you might live your life (AV/screens), I would suggest setting up on the curtain wall and seeing how that works. Maybe angle it VERY slightly up. I'm not sure how it would work, and I am really not sure how wide you could get the speakers without losing center image. If I did this, I would use stand mounts and put the chairs on sliders for easy adjustment. But then I have different speakers for AV and music, so that would be easy for me.

Pareto! that was excellent advice - Miles Davis. Just ordered it! Though I do hear centre image but now that you mentioned it sometimes it is slightly to one side..now I am really curious..... Thank you!

I thought the main question here was about the first reflection, and that will be equal as strong even if it's not a full wall as the first reflection point is there anyway as can be seen in the pictures.

I think you should test putting mattresses or something similar at the first reflection points on both side walls (one behind the curtain), and then listen for a while if you find it better. I think you will get a more focused sound if you treat those reflections as they are probably rather strong at that short distance.

But again, measurements would be helpful to make sure what is going on in the room.

Goat! Thank you. I did not even think about treating the window behind the curtain. Also thanks for confirming that the 1st reflection will be as strong even though the wall ends a few inches above the tweeter. It's really 1/4 of a wall so maybe I am lucky a lot of pressure and sound spill into the other room since it opens up 2 feet in front of the speaker.

 

[AdamG]

Pareto! that was excellent advice - Miles Davis. Just ordered it! Though I do hear centre image but now that you mentioned it sometimes it is slightly to one side..now I am really curious..... Thank you!

Goat! Thank you. I did not even think about treating the window behind the curtain. Also thanks for confirming that the 1st reflection will be as strong even though the wall ends a few inches above the tweeter. It's really 1/4 of a wall so maybe I am lucky a lot of pressure and sound spill into the other room since it opens up 2 feet in front of the speaker.

I have a long wall of glass doors that are 4 large sliding glass doors. Wife likes a sheer light curtain that still allows light and views. This curtain looks great but does little to dampen the reflections from this entire wall. I installed a second curtain rod and a heavy curtain that is basically a blackout curtain that is sealed on one side with a rubbery elastic like sealant. When I want to watch a movie or music I pull the heavy curtain closed. It makes a big difference in reducing the higher frequency reflections and also helps darken the room for better movie experience and less screen light reflections. It’s a happy compromise with the Wife. Maybe something like this might work for you too?

 

[Reminiscent Audio Guy]

I have a long wall of glass doors that are 4 large sliding glass doors. Wife likes a sheer light curtain that still allows light and views. This curtain looks great but does little to dampen the reflections from this entire wall. I installed a second curtain rod and a heavy curtain that is basically a blackout curtain that is sealed on one side with a rubbery elastic like sealant. When I want to watch a movie or music I pull the heavy curtain closed. It makes a big difference in reducing the higher frequency reflections and also helps darken the room for better movie experience and less screen light reflections. It’s a happy compromise with the Wife. Maybe something like this might work for you too?

Adam! That was dynamite! Going to Ikea to try this out... on a side note, I am stunned that shipping is as much as every acoustic panel I added to cart. Shipping was pretty much equivalent to each item which doubles the price of every item form GIK. I googled fabric for DIY pannels and Found this with "testing" so much less expensive - hemp is used for panels: https://www.dopepanels.com/. I am on the double curtain quest... Thank you!

 

[AdamG]

Adam! That was dynamite! Going to Ikea to try this out... on a side note, I am stunned that shipping is as much as every acoustic panel I added to cart. Shipping was pretty much equivalent to each item which doubles the price of every item form GIK. I googled fabric for DIY pannels and Found this with "testing" so much less expensive - hemp is used for panels: https://www.dopepanels.com/. I am on the double curtain quest... Thank you!

Try Amazon. They have some good selections for Darkening room curtains. This was the brand we went with and am very happy with the quality and performance of these.

H.VERSAILTEX Linen Blackout Curtains 108 Inches Long 100% Absolutely Blackout Thermal Insulated Textured Linen Look Curtain Draperies Anti-Rust Grommet, Energy Saving with White Liner, 2 Panels, Grey https://a.co/d/2S28PJa

 

[Reminiscent Audio Guy]

Try Amazon. They have some good selections for Darkening room curtains. This was the brand we went with and am very happy with the quality and performance of these.

H.VERSAILTEX Linen Blackout Curtains 108 Inches Long 100% Absolutely Blackout Thermal Insulated Textured Linen Look Curtain Draperies Anti-Rust Grommet, Energy Saving with White Liner, 2 Panels, Grey https://a.co/d/2S28PJa

Fantastic. Thank you for the link!

 

[dualazmak]

Try Amazon. They have some good selections for Darkening room curtains. This was the brand we went with and am very happy with the quality and performance of these.

H.VERSAILTEX Linen Blackout Curtains 108 Inches Long 100% Absolutely Blackout Thermal Insulated Textured Linen Look Curtain Draperies Anti-Rust Grommet, Energy Saving with White Liner, 2 Panels, Grey https://a.co/d/2S28PJa

Yes, very nice suggestion, fully agree with you!
I do exactly the same thing to our large glass door-windows facing to our garden using very thick darkening drape curtains together with thin race curtains (dual-curtain-rail up on the ceiling curtain-rail-box). You can also see my primitive acoustic treatments on our upright piano in the leftside.

If you would be interested in details of my latest audio setup, please visit my post #931 on my project thread.

 

[Pareto Pragmatic]

Pareto! that was excellent advice - Miles Davis. Just ordered it! Though I do hear centre image but now that you mentioned it sometimes it is slightly to one side..now I am really curious..... Thank you!

It's a classic and worth owning. But can be streamed. Anything with a solid center can be used, I just find that first track particularly sensitive in my room.

If you have a center pulled to one side, that usually means more reflections from that side. Toeing the offending speaker slightly in might be enough to bring it into balance. Or the other one slightly out.