Three measurements - same speaker

[brk]

Hello,

Wanted to get some expert opinion on what is probably a known issue. In trying to EQ my two-way speakers with REW, I took measurements using three different methods at the listening position.
1. Moving mic - slowly twirling the mic in 3" circles around the ear.
2. Stationary empty - average of 6 measurements roughly forming a cube around ear position using a mic stand. I am out of the room.
3. Stationary person - average of 6 measurements roughly forming a cube around ear position using a mic stand. I am sitting still next to the mic in listening position.

All were obtained using at least 90 seconds of periodic pink noise playing through the one speaker at a time, a UMIK-1, 13x19 foot room, and couch positioned about 8' from speakers. I have repeated this experiment.

Bass measurements are similar across the methods. However, my presence at the listening position - either using the moving mic method or sitting next to the stationary mic -boosts the 400-700 hz region by about 3 db, shifts an 800 hz peak over to about 1000 hz, and diminishes the treble over 3K by another 3 db compared with the empty room.

Which one is "right"? (I have made EQs for all three and have a subjective preference)

Thanks very much,

Bryan

 

[ernestcarl]

Get your body as far away from the listening position and microphone as possible. Your body and head in close proximity acts like a “boundary” that will influence the measurements.

 

[brk]

I agree - except - my body is there when listening to music. So this odd shaped “boundary” may represent the true state of affairs, .Am trying to figure out what exactly is going into my ears when listening.

 

[ernestcarl]

I agree - except - my body is there when listening to music. So this odd shaped “boundary” may represent the true state of affairs, .Am trying to figure out what exactly is going into my ears when listening.

Seriously, no one measures that way — I think — unless you’re new to measurements… or are just operating on what you think is logically “common sense”, but really is wrong.

Even Amir and Erin take pains to wrap the microphone in their Klippel NFS with absorption material.

 

[brk]

OK - thanks. Many posts in the REW and other forums tout the moving mic method of measurement, which by design includes your body. I thought I could get the two methods to align if I took enough static measurements around the same area, but never could. Am wondering whether the presence of the body with the moving mic method is the primary cause of the distinction, rather than subtle differences in positioning.

Of note, EQ tailored to the moving mic measurements sounds subjectively better than EQ tailored to the static measurements, but I have not confirmed this in a true A-B matched test.

 

[ernestcarl]

EQ tailored to the moving mic measurements sounds subjectively better than EQ tailored to the static measurements, but I have not confirmed this in a true A-B matched test.

I would use more than one method and overlay the results. Anechoic/quasi-anechoic, regular sweeps at the MLP (ideally with some frequency dependent window), and MMM.

 

[Absolute]

In my opinion it's better to measure many individual spots in and around the seating position to more easily distinguish the areas you should/shouldn't equalize.
While MMM and spatial averages will look very similar, you can't use those to determine what happens in time.

More often than not you will end up making the time-domain much worse in places with those averaging methods, something that's extremely audible and detrimental to sound quality - especially as you move above around 100 hz.

Many believe that you don't hear anything other than the room up to between 300-500 hz, but Sean Olive explained in Erin's interview of him how speaker resonances in the upper bass/lower mids shows up in blind tests even when the lower resolution measurements (like in-room gated measurements) looked good.

A simple look at the time-domain will reveal problems that the frequency response doesn't show.

 

[ernestcarl]

More often than not you will end up making the time-domain much worse in places with those averaging methods, something that's extremely audible and detrimental to sound quality - especially as you move above around 100 hz.

Multi-position sweeps and MMM at different seating positions (angles/distances), then. No need to average them all into a blur. Same with quasi-anechoic measurements. A simple overlay of the "family of curves" is revealing enough, and so there is no need to average. What I would only suggest is is to learn to use more than one method.

 

[brk]

| Sean Olive explained in Erin's interview of him how speaker resonances in the upper bass/lower mids shows up in blind tests even when the lower resolution measurements (like in-room gated measurements) looked good.

This makes sense as EQ to the lower-mids seems - to me - to have the strongest audible impact.

In terms of measuring many individual spots in and around the seating position, you mean without yourself in or near the listening position? As a non-audio engineer, it seems like some sort of earbud microphone would most reliably track what actually goes into your ear - you could then move your head around and change positions to simulate listening.

 

[ernestcarl]

| Sean Olive explained in Erin's interview of him how speaker resonances in the upper bass/lower mids shows up in blind tests even when the lower resolution measurements (like in-room gated measurements) looked good.

This makes sense as EQ to the lower-mids seems - to me - to have the strongest audible impact.

In terms of measuring many individual spots in and around the seating position, you mean without yourself in or near the listening position? As a non-audio engineer, it seems like some sort of earbud microphone would most reliably track what actually goes into your ear - you could then move your head around and change positions to simulate listening.

I would just try to get out of the way as much as possible — same is true while holding the mic for MMM — for example, Erin uses a boom stick extension in his home theater; although, I don’t due to a lack of space and since I’m already standing literally against the wall.

What a microphone sees and how it’s presented in graphs (many of us don’t have a Klippel rig anyway so are limited to in-room measurements), and how we end up actually perceiving things are two different things. For instance, look up why the stereo phantom center is deeply flawed… trying to artificially recreate a center speaker will inevitably produce audible combing artifacts — even if it sounds perfectly fine to most of us.

But, we can sort of infer perhaps just “enough” from measurements to figure out what someone may “prefer” or which set of measurements come closer producing the expected and desired output — even if we often do not possess the time and resources to measure and analyze every single detail of a sound reproduction system, of course.

As we move heads and bodies, our relation to the sound sources and boundaries change so perception dynamically changes, too. So I do not expect any steady state point measurement to ever be fully representative of what we hear.

Psychoacoustics is a very broad subject and something some people end up studying for years at university. I do not think I can myself answer in detail what “is going into your ears”, to be honest — though, I think I sort of have some idea…

Some answers to your questions may already have been discussed elsewhere in the “Psychoustics” section of the forum.

 

[Hipper]

I would not look at measuring as an exact science but a guide. When I did my measurements I used one speaker, the left say, and placed the mic where my left ear would be, pointing at the centre of the speaker. Once I'd moved that around to get the best sounding position (only for the 0-300Hz range) then I placed the right speaker and measured that, hoping in my symmetrical room it would be more-or-less the same. I should add that I am the only listener. The ultimate decider on what is good is what you hear.

My post 6 in this thread may interest you.

https://www.audiosciencereview.com/...om-measurements-an-example.27151/#post-933488

If you follow the link in that post, then go to my post 3 on the that thread, then my post 6 on this third thread, you may also find some interesting info!!

Also, on the the above thread, my post 7, I mention how head movement whilst sitting in your listening chair can also affect the sound. This again illustrates that you cannot be exact.

 

[Balle Clorin]

What is the point of posting your test description without including the REW plots? moving mic always gives nicer looking results due to averaging local influences. averaging is good since it prevents overcorrecting local measurement artifacts

 

[Jdunk54nl]

Ultimately the method you choose to use doesn't really matter. Measurements are a tool, you need to understand your tool and how you are using it. As soon as you realize it is a tool, then use it appropriately.

Most house curves (all that I know of don't) do not include bodies in them because every body is different and would cause different things to take place in the frequency response. Taller, wider, shorter, head size, etc all would make changes in the response curve.

But, going back to that measurements are just a tool and you should understand them, having your body in there or out of there doesn't matter as long as you know how to use your tool appropriately for each scenario.


This reminds me of Toole's tuning of a theatre from his book, they had the microphone placed right at head level, which was close to the seat back. It was causing some weird measurements compared to what they heard. They moved the microphone up like a 1ft (IIRC that was how high) and it changed the measurements and matched what they heard. This ended up being due to the seat reflections, something that isn't there when a head is there. Toole understood his tool (pun intended ??) and used it appropriately.

Same with calibration file vs no calibration file. Or 90 degrees vs 0 degrees. It doesn't really matter if you know how to use your tool. It would only really matter if you need to make very precise measurements. Measuring in a room is not that.


Learn how to use your tool. Learn when to use your tool. Learn when to use another tool.