First REW measurements - feedback appreciated :)

[viktorapo]

Speaker to side wall = 0.95
SBIR cancellation frequency = 0.95m x 4 = 3.8m
That equals 90Hz.

The problem with speaker placement is that there is no perfect position, only the least compromised positions. This is particularly true for smaller rooms. If you were to push your speakers so close to the wall that you eliminate this SBIR cancellation, you would screw up central imaging by widening your listening triangle. Another option is to position your speakers asymmetrically in the room so that the SBIR frequencies do not coincide. But if you do that, the upper frequencies will also have asymmetric reflections, and it will screw up imaging.

Another option is to get a subwoofer and cross it over at about 100Hz. You will need a bit of DSP to get it to blend in though. It may be best to try to lower that frequency so that you don't have to run the sub so high.



No. Any speaker placed in the same location will have the same problems below the Schroder frequency, assuming the frequency response is the same. The reason you buy a KH310 is because it's not as lumpy at the top end as your Yamaha.



That eBook is not a complete manual on acoustics, but it will be enough to get you started. You will still need to buy and read an acoustics text like Toole or Everest if you want to fully understand the subject. And BTW I never wrote that book with printing in mind, most of those diagrams rely on colour to make sense.

I can try positioning, pushing them forward and also moving myself forward with the seat so the triangle is the same, that should keep the stereo image the same, shouldnt it?

I get it, but meant more of will the DSP room correction provided by Neumann be able to resolve it or its just a guessing game?

Printed it in color i love reading hard copies

 

[Keith_W]

I can try positioning, pushing them forward and also moving myself forward with the seat so the triangle is the same, that should keep the stereo image the same, shouldnt it?

Read carefully. I think we worked out that the cancellation is coming from the side walls. You have two speakers equidistant to the side walls = double the cancellation. You can confirm that by pushing both speakers to the side walls and re-measure. But having your speakers so wide will certainly screw up the listening triangle.

I get it, but meant more of will the DSP room correction provided by Neumann be able to resolve it or its just a guessing game?

DSP can not be used to fill dips. Well actually it can, but you will need much more sophisticated DSP than what the Neumann has. And even then it's not that successful. It is ALWAYS BETTER to get rid of the dips by physical means as much as possible.

 

[viktorapo]

Read carefully. I think we worked out that the cancellation is coming from the side walls. You have two speakers equidistant to the side walls = double the cancellation. You can confirm that by pushing both speakers to the side walls and re-measure. But having your speakers so wide will certainly screw up the listening triangle.



DSP can not be used to fill dips. Well actually it can, but you will need much more sophisticated DSP than what the Neumann has. And even then it's not that successful. It is ALWAYS BETTER to get rid of the dips by physical means as much as possible.

A bit confused. I thought you are referring more to the front wall, as the math showed a SIBR cancellation @ 90hz and our null was at 75-80hz - not too much off but still.

What would be the go-to step in this case - just experimenting left/right and measuring? Is my next step speaker positioning or should I look more into tuned bass traps for the specific null freq?

 

[Keith_W]

A bit confused. I thought you are referring more to the front wall, as the math showed a SIBR cancellation @ 90hz and our null was at 75-80hz - not too much off but still.

Do the maths yourself. Speaker distance to front wall = 0.25m. Multiply this by 4, then plug that result into a sound wavelength-frequency calculator. Result = 343Hz. Then do the same for speaker distance of 0.95m to the side wall.

 

[viktorapo]

could that 75-80hz null be from the floor?
also, i measure speaker distance from wall from the most back point of the speaker to the wall, is that correct?
another question is, am i looking correctly but the db difference between the L and R speakers is like 10db? what could that be? i cant hear it audibly when listening, producing

 

[janbth]

could that 75-80hz null be from the floor?

First of all, some clarification on the terminology: A null is different to a dip:

• A null is a region in space. For a given room mode - a standing wave - it's where the sound pressure doesn't fluctuate, i.e. there is no "sound" in a null.
• A dip is a region in the frequency domain. If you put a mic in a null of a mode and measure the response, you will see a dip in the frequency of the mode.

So is the 75-80 Hz dip a floor bounce effect? Almost certainly no. It's almost certainly the effect of a room mode. Try to map out the standing wave pattern for your room, and see if you have the MLP in a null.

Edit: By the way: forget SBIR. Your speakers are too close to the front wall. Side wall effects may possibly explain the 180 Hz dip, but I doubt it. Some kind of reflection cancellation maybe.

 

[Keith_W]

View attachment 542619

could that 75-80hz null be from the floor?

Probably not. Floor bounce occurs in front of the speaker, so it's probably a room mode.

also, i measure speaker distance from wall from the most back point of the speaker to the wall, is that correct?

No. You measure the speaker distance from the sound source. If it's unported or front ported, you measure from the front baffle. If it's rear ported, you assume the sound source comes from midway between the woofer and the rear port. To be honest it doesn't really matter, all these are approximations anyway. Including the speed of sound, which varies according to temperature and elevation. These calculations give you a "ballpark" figure, and in the end it is you who needs to decide.

another question is, am i looking correctly but the db difference between the L and R speakers is like 10db? what could that be? i cant hear it audibly when listening, producing

Where is the 10dB difference? I don't see a 10dB difference.

 

[viktorapo]

@Keith_W thanks! i think i miscalculated by looking at a wrong graph regarding the 10db.

@janbth thank you as well!

my next step is to measure with putting the mic in several positions forward and back and check/observe that 75-80hz dip.

 

[Flaesh]

to measure with putting the mic in several positions forward and back

If the room is more or less cuboidal, try REW Room sim and compare it with reality.

ps: did you show the plan and dimensions of the room?

 

[viktorapo]

If the room is more or less cuboidal, try REW Room sim and compare it with reality.

ps: did you show the plan and dimensions of the room?

yes, its in the main post (1st post). there are dimensions, images, etc.

 

[Flaesh]

^Indeed! But there was no plan with speaker and seating.

The dips vary greatly along the front-rear axis. Actual measurements are more reliable than the simplified model, but the trend can be seen in the model.

ps: Are the measurements taken with room correction?

 

[viktorapo]

^Indeed! But there was no plan with speaker and seating.
View attachment 543064
The dips vary greatly along the front-rear axis. Actual measurements are more reliable than the simplified model, but the trend can be seen in the model.

ps: Are the measurements taken with room correction?

speaker to side wall is 95cm, to front wall 25cm. what do you mean about:

ps: Are the measurements taken with room correction?

if you are referring to the acoustic correction yes, if you are referring to any DSP room correction - NO, im running my Yamaha HS7 straight out of RME

also, what trend do you see in the model? i am a bit color blind and have trouble distinguishing on this image tbh :/

 

[Flaesh]

Try moving the listening position in the simulator yourself; it's simple and straightforward. And real mic also.
Usually, there are noticeable peaks in the graphs in rooms, but after room correction, they're cutted out. That's why I asked.
Is dip around 80Hz noticeable when listening to music? Yeah, that's a tricky question)).

 

[viktorapo]

Try moving the listening position in the simulator yourself; it's simple and straightforward. And real mic also.
Usually, there are noticeable peaks in the graphs in rooms, but after room correction, they're cutted out. That's why I asked.
Is dip around 80Hz noticeable when listening to music? Yeah, that's a tricky question)).

aham, thanks. well, playing around does not look promising anyway, ill have access to the microphone again on wednesday so i'll re-measure several positions

 

[Flaesh]

tricky question)).

Without access to a microphone, you can listen to the audibility of low-frequency articulation https://www.audiocheck.net/audiotests_matt.php and then hear or not hear a defect when playing music.

 

[viktorapo]

Without access to a microphone, you can listen to the audibility of low-frequency articulation https://www.audiocheck.net/audiotests_matt.php and then hear or not hear a defect when playing music.

was referring around to playing around in the Room simulator, sorry for not being specific. the 80hz dip seems like always present

 

[Flaesh]

Yes, I get it. No apologies needed.
Matt test helps investigate the audibility of the effects of signal aberrations, particularly in the dip region.

the 80hz dip seems like always present

I had a similar issue in the simulator and in my room (but 40-50 Hz at the listening position in my case), it moved in frequency in the same way.. It noticeably damaged the music. I had to take action.

 

[DY2]

I'll tell you from my experience, maybe it will help the initiator.
In my room I measured my subwoofers individually, from the listening position with Umik-2 in vertical position and 90 degree calibration file.
As can be seen from the graph, each position has a different response, and the black line represents the final response with all active positions, i.e. front left/right, middle left/right and rear left/right.

Before measuring with Umik-2 and REW, I calibrated each subwoofer from the listening position, with the ECM8000 microphone plugged into the DBX Venu 360 and AutoEQ turned on. The pictures show exactly how each subwoofer responds and what corrections were applied for the final result.
Now all that's needed is manual PEQ to flatten the curve to integrate as well as possible with the rest of the system.

 

[viktorapo]

Hey @janbth @Keith_W and @Flaesh here's an new .mdat file with measurements taken in multiple positions: https://www.dropbox.com/scl/fi/uu8y...ey=egnwr9cf2fy0zvh54bgx3ahx5&st=kqnco4tq&dl=0


Posting some photos, let me know if you need anything more or you will use the .mdat to help me analyze this

Listening position SPL

20cm forward SPL

40cm forward SPL

60cm forward SPL

20cm backward SPL

40cm backward SPL

60cm backward SPL

In the .mdat file there are also +20, +40, -20, -40 as well as +-15cm in height from listening position and ofc, more in depth of everything

 

[viktorapo]

Yes, that's exactly what I mean.

First impressions from the L+R+LR response plot:

• There is a dip at 80 Hz, almost certainly a room mode, probably due to an unfortunate listening posistion (because it is visible on both L and R). The solution is to move the MLP or use a sub.
• Another suckout at about 180 Hz. This is a bit too high for room modes, but could possibly be SBIR.

The problem with speaker placement is that there is no perfect position, only the least compromised positions. This is particularly true for smaller rooms. If you were to push your speakers so close to the wall that you eliminate this SBIR cancellation, you would screw up central imaging by widening your listening triangle. Another option is to position your speakers asymmetrically in the room so that the SBIR frequencies do not coincide. But if you do that, the upper frequencies will also have asymmetric reflections, and it will screw up imaging.

i just reposted above new set of measurements and a new .mdat file. am i correct to assume now, that the 40 or 60cm back are better positions by lowering the null and adding a boost around 50-60hz. assuming boosts can be treated easier with an eq then an null?