Main Listening Position

[Titurel]

If I had to pick I'd pick the blue trace, but overall the advice in this thread so far is good.

Your speakers are either too close or too far from the wall, depending on how you're able to place them:

View attachment 522190

This is an illustration for genelecs but the principle applies to any speaker equally. You should ideally get them a good deal closer to the wall, or more than ~90 inches from the wall.

As others have mentioned a lot of the unwanted variation in your bass is due to the room - placement can help, room treatment can help, EQ can clean up whatever those efforts don't fix, at least in terms of FR.

Pardon me for bending the direction of this thread a tiny bit to pose a question.

The speaker placement diagram kemmler3D posted got me thinking. For many of us, placing the speaker flush against the wall or > 2M into the room is not practical, particularly the latter. Unfortunately, I don't have the math or the well schooled intuition to answer the question that the diagram raised for me.

What would be the effect on frequency response if a curved object (like a GIK Polycylindral Diffuser) were placed between the wall and the speaker - the diffuser securely attached to the wall and the speaker back almost touching the diffuser (closer than 1cm)?

I don't suppose this would be a magic bullet, but mighten such an arrangement broaden and reduce the depths of the notches, and thus make DSP solutions more achievable?

 

[Keith_W]

What would be the effect on frequency response if a curved object (like a GIK Polycylindral Diffuser) were placed between the wall and the speaker - the diffuser securely attached to the wall and the speaker back almost touching the diffuser (closer than 1cm)?

I don't suppose this would be a magic bullet, but mighten such an arrangement broaden and reduce the depths of the notches, and thus make DSP solutions more achievable?

It may, or it may not. Most likely it will make not much of a difference. The problem is - there are many causes for those peaks and dips in the response, and SBIR is only one of them. The SBIR frequency is where the distance from speaker to the wall is equal to 1/4 wavelength - so if the distance is 1m, the wavelength is 4m, and the frequency is 86Hz (use this calculator). Your diffuser would need to be pretty large to make any meaningful impact.

 

[Daverich4]

I would appreciate it if someone could take a look at these and tell if one of them is better than the others or if it's not enough difference to matter. I tried my speakers in a number of different locations. I first tried with the speakers at 29" from the front wall as suggested in the graphic higher up in this thread. That was better but still not all that great. I tried the REW simulator which I don't really know how to use as I don't know what to use for absorption rates and my room isn't a perfect rectangle. Anyway, it suggested 43" which was a little better. At that point I moved the right speaker closer to the wall in increments and came up with these. The deepest dips aren't as narrow as they were earlier and some of the peaks have moved or gotten taller. One of these is going to be my choice before (or if) I get a pair of subwoofers. These sweeps are the right speaker only as I didn't want to spend a bunch of time getting the left speaker exactly in place without finding out if any of these was better than the other. The distance from the wall is in the label. Thanks for your help.

 

[tmtomh]

I would appreciate it if someone could take a look at these and tell if one of them is better than the others or if it's not enough difference to matter. I tried my speakers in a number of different locations. I first tried with the speakers at 29" from the front wall as suggested in the graphic higher up in this thread. That was better but still not all that great. I tried the REW simulator which I don't really know how to use as I don't know what to use for absorption rates and my room isn't a perfect rectangle. Anyway, it suggested 43" which was a little better. At that point I moved the right speaker closer to the wall in increments and came up with these. The deepest dips aren't as narrow as they were earlier and some of the peaks have moved or gotten taller. One of these is going to be my choice before (or if) I get a pair of subwoofers. These sweeps are the right speaker only as I didn't want to spend a bunch of time getting the left speaker exactly in place without finding out if any of these was better than the other. The distance from the wall is in the label. Thanks for your help.

All look very similar to me. One or more have a bit less of a null at around 70Hz, 100Hz or 200Hz, but the one that’s slightly better at one of those frequencies is slightly worse at one or both of the others and vice versa. So I do not see a substantive difference overall.

 

[Daverich4]

Using the technique in Post "11 I chose 39" from the front wall although there isn't all that much difference between any of them. For some reason the Right Channel measures quite a bit differently from the Left. I'm not really sure why. There is a picture window on that side but it's covered by pretty heavy drapes. There are pictures of my room in Post #5 if that would help anyone figure out why. I'm posting the measurements of the L, R and L&R measurements along with the measurement of a Convolution filter made with Focus Fidelity. The Reference Curve used for that was Harman. That's where I am at this point. I know some of the measurements aren't all that great but it does sound quite a bit better than it did. I appreciate the help everyone has given me.

 

[Daverich4]

Is there any chance someone could take a quick look at this to help me figure out why the right channel is so different from the left? Thanks.

 

[Keith_W]

Is there any chance someone could take a quick look at this to help me figure out why the right channel is so different from the left? Thanks.

It isn't. That's about what I would expect for a typical speaker in-room.

You have been provided with resources to read the freq response curves for yourself. May I suggest you read those resources?

 

[Daverich4]

View attachment 523446

It isn't. That's about what I would expect for a typical speaker in-room.

You have been provided with resources to read the freq response curves for yourself. May I suggest you read those resources?

Thanks for your help. I’m mostly asking about the dip @40Hz that’s in the right channel and not the left. I’ve read both of your EBooks as well as others that have been posted but that doesn’t leave me with anywhere near the knowledge you and others on this site have. If we’re not to ask for help from others with more experience, that’s fine. I’ll move on.

 

[thcdru2k]

Thanks for your help. I’m mostly asking about the dip @40Hz that’s in the right channel and not the left. I’ve read both of your EBooks as well as others that have been posted but that doesn’t leave me with anywhere near the knowledge you and others on this site have. If we’re not to ask for help from others with more experience, that’s fine. I’ll move on.

Speaker Boundary Interference Response (SBIR) affecting one speaker due to asymmetry of room. Swap the speakers and if the 40hz dip remains you have your answer.

 

[Daverich4]

Speaker Boundary Interference Response (SBIR) affecting one speaker due to asymmetry of room. Swap the speakers and if the 40hz dip remains you have your answer.

Thanks for your response. The front 2/3rds of the room are physically symmetrical and the speakers themselves are equidistant from the walls. Perhaps it’s differences in the room surfaces that’s causing the dip in one channel and not the other? There is a picture window on the right side that’s covered with heavy drapes and the left side has a closed door to a room on that side. Not much I can do to change any of that if that’s the cause.

 

[tmtomh]

Thanks for your response. The front 2/3rds of the room are physically symmetrical and the speakers themselves are equidistant from the walls. Perhaps it’s differences in the room surfaces that’s causing the dip in one channel and not the other? There is a picture window on the right side that’s covered with heavy drapes and the left side has a closed door to a room on that side. Not much I can do to change any of that if that’s the cause.

Hard to know for sure, but I can say that heavy drapes are no match for lower bass sound waves, while a closed door (especially if it’s a solid-core door but even if it’s not) is likely to have quite different sound absorption and reflection qualities than a drape and glass window.

Also, are you doing an MMM measurement (mic at multiple locations within about 12 inches of each other to get an average), or a single point measurement?

 

[Daverich4]

Hard to know for sure, but I can say that heavy drapes are no match for lower bass sound waves, while a closed door (especially if it’s a solid-core door but even if it’s not) is likely to have quite different sound absorption and reflection qualities that a drape and glass window.

Also, are you doing an MMM measurement (mic at multiple locations within about 12 inches of each other to get an average), or a single point measurement?

Thank you. If it's those items there isn't much I can do about it. I'm going to listen for a while and then going forward, my plan is to get a pair of sub woofers and do the crawl to find the best location. A number of sources have suggested one in front and one in back of the room. Or, one on each side wall. I've been using Focus Fidelity to create the Convolution filters and it doesn't support MMM, only point measurements. Actually, up to 10 measurements in different locations but for that reason I've been using point measurements in REW as well. I'll go ahead and try a set of MMM measurements to see if they look any different. Thanks again.

 

[thcdru2k]

Thank you. If it's those items there isn't much I can do about it. I'm going to listen for a while and then going forward, my plan is to get a pair of sub woofers and do the crawl to find the best location. A number of sources have suggested one in front and one in back of the room. Or, one on each side wall. I've been using Focus Fidelity to create the Convolution filters and it doesn't support MMM, only point measurements. Actually, up to 10 measurements in different locations but for that reason I've been using point measurements in REW as well. I'll go ahead and try a set of MMM measurements to see if they look any different. Thanks again.

There may not really be a need for you to do anything. When you listen to music you do not listen to just one speaker you listen to both. When you play both at same time I would guess that 40hz dip is largely filled in. Also a lot of time these dips are seat dependent. You move a foot in any direction at it might be gone.

 

[Daverich4]

There may not really be a need for you to do anything. When you listen to music you do not listen to just one speaker you listen to both. When you play both at same time I would guess that 40hz dip is largely filled in. Also a lot of time these dips are seat dependent. You move a foot in any direction at it might be gone.

You are probably right. I listened to my system for a long time and always thought it sounded pretty good. With a lot of help from a number of the members here it now sounds noticeably better. I’m sure I would be happy to listen to it for a long time just as it is. However, I’ve read a number of posts that claim subwoofers have positive effects beyond smoothing out room modes so I suspect I’ll go ahead with that at some point.

 

[thcdru2k]

You are probably right. I listened to my system for a long time and always thought it sounded pretty good. With a lot of help from a number of the members here it now sounds noticeably better. I’m sure I would be happy to listen to it for a long time just as it is. However, I’ve read a number of posts that claim subwoofers have positive effects beyond smoothing out room modes so I suspect I’ll go ahead with that at some point.

Two would probably get you where you want to be easier but it will be time consuming as you can already see its challenging enough to just get two speakers to play friendly.

 

[janbth]

Speaker Boundary Interference Response (SBIR) affecting one speaker due to asymmetry of room. Swap the speakers and if the 40hz dip remains you have your answer.

It's definitely not SBIR. The lowest SBIR dip occurs when the speaker is located 1/4 wavelength from the wall. At 40 Hz that would be 2.14 m (7 feet).

Boundary effects like SBIR typically occur above 100 Hz or so.

... I’m mostly asking about the dip @40Hz that’s in the right channel and not the left.

Again, it's most likely room modes at these low frequencies. If you do a room mode analysis (or get your favourite AI to do it - and of course verify the results!), then you will find a tangential mode - the (1, 1, 0)-mode - at approximately 38 Hz. You would see a dip if your mic was in the null of that mode. It's a bit unclear why you see it in R but not in L, though. Possibly, due to an asymmetry in your setup (which could be small).

These things are explained in detail in Floyd Toole's Sound Reproduction. In the 4th Edition, you will find boundary effects in Chapter 13 and room modes in Chapter 14. Recommended reading!

 

[thcdru2k]

It's definitely not SBIR. The lowest SBIR dip occurs when the speaker is located 1/4 wavelength from the wall. At 40 Hz that would be 2.14 m (7 feet).

Boundary effects like SBIR typically occur above 100 Hz or so.


Again, it's most likely room modes at these low frequencies. If you do a room mode analysis (or get your favourite AI to do it - and of course verify the results!), then you will find a tangential mode - the (1, 1, 0)-mode - at approximately 38 Hz. You would see a dip if your mic was in the null of that mode. It's a bit unclear why you see it in R but not in L, though. Possibly, due to an asymmetry in your setup (which could be small).

These things are explained in detail in Floyd Toole's Sound Reproduction. In the 4th Edition, you will find boundary effects in Chapter 13 and room modes in Chapter 14. Recommended reading!

You are right...the 40hz is room mode. He does have something going on around 140hz coincidentally

 

[Daverich4]

It's definitely not SBIR. The lowest SBIR dip occurs when the speaker is located 1/4 wavelength from the wall. At 40 Hz that would be 2.14 m (7 feet).

Boundary effects like SBIR typically occur above 100 Hz or so.


Again, it's most likely room modes at these low frequencies. If you do a room mode analysis (or get your favourite AI to do it - and of course verify the results!), then you will find a tangential mode - the (1, 1, 0)-mode - at approximately 38 Hz. You would see a dip if your mic was in the null of that mode. It's a bit unclear why you see it in R but not in L, though. Possibly, due to an asymmetry in your setup (which could be small).

These things are explained in detail in Floyd Toole's Sound Reproduction. In the 4th Edition, you will find boundary effects in Chapter 13 and room modes in Chapter 14. Recommended reading!

Thanks for the suggestion. Amazon had it and it should be here tomorrow.

 

[janbth]

Thanks for the suggestion. Amazon had it and it should be here tomorrow.

Cool!

 

[Daverich4]

These things are explained in detail in Floyd Toole's Sound Reproduction. In the 4th Edition, you will find boundary effects in Chapter 13 and room modes in Chapter 14. Recommended reading!

Thanks for the suggestion. It’s kind of a tough read for me but it’s already given me some ideas on things to try regarding speaker placement and alternate positioning of my existing room treatment. I appreciate your help.