Speaker frequency response (in room)

[svtcontour]

If I was to measure the frequency response of the system at the listening position (which of course takes room reflections into account), do I take my measurement mic and point it between the two loudspeakers? I've read online that some point it up which to me seems like it would lose lots of high frequency if its a directional measurement microphone.

I did it a while back using a software called TrueRTA but I was pointing it between the two speakers. Its not exactly super smooth but I want to try it again the proper way (unless the way I did it was fine). Its for an open baffle speaker I built a few years back.

 

[bmwr75]

I do in room measurements with the microphone placed right where my head is at in the listening position.

 

[svtcontour]

I do in room measurements with the microphone placed right where my head is at in the listening position.

right, its what I did, but do you point it between the two loudspeakers or up like I've read some people do?

 

[sam_adams]

right, its what I did, but do you point it between the two loudspeakers or up like I've read some people do?

What mic? What software?

 

[boxerfan88]

My opinion:

1. if correcting up to schroeder or up to 500-600Hz, pointing mic at ceiling or at speaker doesn’t really matter

2. if correcting full range, i think it’s better to point mic at speakers acoustic center so as to capture all the HF energy. if mic is pointed at ceiling, it’ll likely have some HF rolloff

 

[svtcontour]

What mic? What software?

Any RTA software where you're not running any kind of gated measurement and any calibrated directional microphone - example, the Dayton calibrated Mic or the Behringer ECM8000 or the DBX one.

 

[svtcontour]

My opinion:

1. if correcting up to schroeder or up to 500-600Hz, pointing mic at ceiling or at speaker doesn’t really matter

2. if correcting full range, i think it’s better to point mic at speakers acoustic center so as to capture all the HF energy. if mic is pointed at ceiling, it’ll likely have some HF rolloff

Ah ok perfect. Ya its more for full range so in that case pointing forward to center then is the best way for me. Its what I did so great. Thank you

 

[sam_adams]

Any RTA software where you're not running any kind of gated measurement and any calibrated directional microphone - example, the Dayton calibrated Mic or the Behringer ECM8000 or the DBX one.

Any measurement mic worth the money paid for it will come with correction files for both zero-degree and ninety-degree positioning for measurement at a minimum. The correction file will correct the frequency rolloff that occurs with the different positions to deliver consistent response regardless of the mic orientation. Professional calibration of the mic against a known NIST-traceable standard—and the correction files supplied from that calibration—will produce reliable results that are sufficient for the majority of home/hobbyist users. The measurement software has to be able to load those files to apply the correction, of course.

 

[NTK]

There is a good discussion on measurement microphones here:

Room Measurement Tutorial for Dummies Part 2

Room Measurement Tutorial for Dummies Part 2: Selecting a Measurement Microphone I hope everyone has read the first part of this tutorial on downloading and installing Room EQ Wizard. Here is the link to that if you missed it...

www.audiosciencereview.com

 

[svtcontour]

Any measurement mic worth the money paid for it will come with correction files for both zero-degree and ninety-degree positioning for measurement at a minimum. The correction file will correct the frequency rolloff that occurs with the different positions to deliver consistent response regardless of the mic orientation. Professional calibration of the mic against a known NIST-traceable standard—and the correction files supplied from that calibration—will produce reliable results that are sufficient for the majority of home/hobbyist users. The measurement software has to be able to load those files to apply the correction, of course.

Yes I have a correction file. I'm not sure why we are going through all this LOL. Has nothing to do with my question, which was "do most people point the microphone forward between the two loudspeakers when doing a measurement with room taken into consideration or do as some suggest which is to put up at the ceiling. Either way I got my answer from someone so I'm all set.

 

[jhaider]

Any measurement mic worth the money paid for it will come with correction files for both zero-degree and ninety-degree positioning for measurement at a minimum.

Earthworks mics only have an on-axis calibration file, so...

IMO if you're trying to do anything except measure a single speaker at a close distance (i.e. taking polar measurements to measure raw drivers for a crossover or validate a design) point up. And sample multiple points, or do an MMM. A single point "room measurement" is all but worthless on its own.

 

[sam_adams]

Yes I have a correction file. I'm not sure why we are going through all this LOL. Has nothing to do with my question, which was "do most people point the microphone forward between the two loudspeakers when doing a measurement with room taken into consideration or do as some suggest which is to put up at the ceiling. Either way I got my answer from someone so I'm all set.

If you take a moment to understand how room correction software works and read the instructions for measurement that are provided by those that the supply that software, Dirac, Audyssey, et al, you will find that all of them recommend that the mic be oriented ninety-degrees to the speakers to capture the room response and not the direct response of the speakers.

Earthworks mics only have an on-axis calibration file, so...

Send the the mic to Cross Spectrum Labs to have it calibrated for other positions.

A single point "room measurement" is all but worthless on its own.

That is one reason why Dirac and Audyssey recommend multi-point measurements.

 

[svtcontour]

There is a good discussion on measurement microphones here:

Room Measurement Tutorial for Dummies Part 2

Room Measurement Tutorial for Dummies Part 2: Selecting a Measurement Microphone I hope everyone has read the first part of this tutorial on downloading and installing Room EQ Wizard. Here is the link to that if you missed it...

www.audiosciencereview.com

Oh great. Thanks NTK!

 

[jhaider]

If you take a moment to understand how room correction software works and read the instructions for measurement that are provided by those that the supply that software, Dirac, Audyssey, et al, you will find that all of them recommend that the mic be oriented ninety-degrees to the speakers to capture the room response and not the direct response of the speakers.

RoomPerfect doesn't. RoomPerfect instructions are to face the microphone forward for the first measurement, and vary the incident angle for the others.

And for the record, RoomPerfect is the only commercially-available system with publicly-available blind test validation as outperforming no EQ.

Send the the mic to Cross Spectrum Labs to have it calibrated for other positions.

Or don't bother, because the microphone is good enough that their "generic" grazing incidence cal file offers the precision needed for in-room treble measurements.

Help with a math problem - converting Earthworks axial cal file to 90 deg

I'm trying to figure out a math problem that I thought would be easy but is ending up being more difficult than I expected. I'm trying to create a 90 deg cal file for an Earthworks M30. I have the current cal file ("ECF") as well as a "90 deg typical response" ECF from Earthworks. So I want to...

www.audiosciencereview.com

Besides, I thought Herb had paused that business. Too much backlog with bigger fish.

Of course, one shouldn't be "correcting" small deviations in the HF based on listening position measurements anyway. I know there's one person who has a bit of a cult following who believes that you can take one measurement, set a software to do some bleep blorps, and some magic lens makes everything just right. I have my doubts.

 

[Geert]

If I was to measure the frequency response of the system at the listening position (which of course takes room reflections into account), do I take my measurement mic and point it between the two loudspeakers?

It depends on the design of the microphone. If it's a free field design (designed for reflection free environments), point it at the speakers, if it's a diffuse field design, point it up. Most mic's used for room measurements are free field (they have a built in electric filter to compensate for the rise in HF), but best to read the manual.

Edit: from the Brüel&Kjær Microphone handbook:



The top curve shows the rise in pressure at the diagram of a 1/2" microphone capsule, which results in a rise of HF sensitivity. The middle curve shows the response of a 'free field' measurement microphone, which has a built-in compensation for that rise in HF.

 

[bmwr75]

right, its what I did, but do you point it between the two loudspeakers or up like I've read some people do?

I use a miniDSP UMIK-1 and it come with two calibration files. One for pointing the mic at the speakers (one I use) and another for pointing the mic straight up (90 degrees file).

 

[No. 5]

If I was to measure the frequency response of the system at the listening position (which of course takes room reflections into account), do I take my measurement mic and point it between the two loudspeakers? I've read online that some point it up which to me seems like it would lose lots of high frequency if its a directional measurement microphone.

I did it a while back using a software called TrueRTA but I was pointing it between the two speakers. Its not exactly super smooth but I want to try it again the proper way (unless the way I did it was fine). Its for an open baffle speaker I built a few years back.
View attachment 425488

Think about the geometry and acoustics involved. A 1/2" body measurement microphone will be omnidirectional up to around 2kHz, so it doesn't really matter where you point it up to those frequencies. Above 2kHz or so, the microphone will become increasingly directional. That means that high frequencies will be underreported to a greater and greater degree the further off axis they arrive from.

So if you point the microphone between the speakers, the high frequencies of the horizontal first reflections will be underreported to a greater degree than the highs from the speakers, which will themselves be underreported owning to being 30 degrees (or so) off the microphone's reference axis. On the other hand, if you point the mic at ceiling, all the energy from the speakers and horizontal reflections will be reported the same and a correction curve can be applied to account for the 90 degree arrival angle.

On the other hand, if you don't want to deal with arrival angles and correction curves, get a mic with a smaller capsule/body. It will be more omnidirectional to a higher frequency and you won't have to worry about the direction it's pointing.

 

[svtcontour]

It depends on the design of the microphone. If it's a free field design (designed for reflection free environments), point it at the speakers, if it's a diffuse field design, point it up. Most mic's used for room measurements are free field (they have a built in electric filter to compensate for the rise in HF), but best to read the manual.

Edit: from the Brüel&Kjær Microphone handbook:

View attachment 425515

The top curve shows the rise in pressure at the diagram of a 1/2" microphone capsule, which results in a rise of HF sensitivity. The middle curve shows the response of a 'free field' measurement microphone, which has a built-in compensation for that rise in HF.

Oh interesting. Ok I have to check this out. I typically use the Dayton USB calibrated mic. I have to see how its designed then. Thank you.

 

[svtcontour]

I use a miniDSP UMIK-1 and it come with two calibration files. One for pointing the mic at the speakers (one I use) and another for pointing the mic straight up (90 degrees file).

Oh nice. I assume then my Dayton USB mic which as one calibration file, is for forward measurements.

 

[svtcontour]

Think about the geometry and acoustics involved. A 1/2" body measurement microphone will be omnidirectional up to around 2kHz, so it doesn't really matter where you point it up to those frequencies. Above 2kHz or so, the microphone will become increasingly directional. That means that high frequencies will be underreported to a greater and greater degree the further off axis they arrive from.

So if you point the microphone between the speakers, the high frequencies of the horizontal first reflections will be underreported to a greater degree than the highs from the speakers, which will themselves be underreported owning to being 30 degrees (or so) off the microphone's reference axis. On the other hand, if you point the mic at ceiling, all the energy from the speakers and horizontal reflections will be reported the same and a correction curve can be applied to account for the 90 degree arrival angle.

On the other hand, if you don't want to deal with arrival angles and correction curves, get a mic with a smaller capsule/body. It will be more omnidirectional to a higher frequency and you won't have to worry about the direction it's pointing.

Oh interesting and thank you for that info. Appreciated No. 5