What happens if you use the ECM8000 Basic Mic 'not Basic +' with Cal file for measuring your rooms response?

 

The Basic + adds calibration for 45° and 90° mic orientations, in addition to the 0° orientation of the Basic calibration package. However, for frequency response measurements you typically want 0° orientation – i.e., pointed at the signal source. More reading as to the “whys” and “wherefores” here.

Regards,
Wayne

 

Thanks Wayne.

The more you go into EQ the deeper it gets that's for sure, it's like, just as you learn how to open one door another comes along with a bigger lock, 'so to speak'.



The short answer for subwoofer measurements is, it doesn’t matter.

If you’re doing full-range measurements (your main-channel speakers), the short answer is, you only point the mic towards the ceiling if you’re using a 90-degree incident (vertical) calibration file.

Horizontal orientation with the mic on-axis to the sound source (0-degrees incident) has been the traditional method for full-range, free-field measurement, where the room was an open space relatively free of reflections. However, that’s mainly because most stand-alone RTAs (which until several years ago was about the only thing available) came with mics that were calibrated for on-axis measurements.

Some RTA manufacturers offered the option of 90-degree orientation for random incident measurements (aka diffuse field), where the sound arrives from all directions more or less simultaneously, with equal probability and level. In other words, an exceedingly reverberant environment. Random-incident measurements required a different capsule for the measurement mic (which the manufacturer made available), for reason of the specific calibration as well as a housing better suited for 90-degree orientation.

That just refers to the mic’s position during its calibration, however. Everything I’ve seen for actual “in the field” measurements says the standard protocol for horizontal (on-axis) measuring is 20 degrees, and 70 degrees for vertical (i.e., angled slightly forwards towards the sound source). This may have something to do with compensating for interference from the mic’s housing with the sound waves, I forget exactly why.

The ready availability these days of mics with 90-degree calibration certainly opens up more measurement options. Others have their opinions, and maybe they’ll weigh in, but mine is that you will generally get the best results with on-axis measurements. It should be a no brainer to figure out that the home theater environment, while certainly not totally free of reflections and reverberation, more closely resembles a free-field environment than a random-incident environment.

Vertical orientation may add more upper-frequency information from ceiling reflections than you’d get with on-axis, and as such will probably influence what the RTA displays. How much so will depend on your particular room – how “live” it is, the height of the ceiling in relation to the distance between the sound source (speaker) and measurement mic (i.e. inside or outside the “first reflection” zone), etc. Even though the ECM8000 is omnidirectional, its capsule is rather large for a measurement mic. As a result, its off-axis response (compared to on-axis) starts skewing as low as 3 kHz. So differences >3 kHz are what you might see with horizontal vs. vertical readings. (Smaller-capsule omni mics typically retain uniform 0 vs. 90-degree response at least an octave higher.)

Regards,
Wayne

 

Hi.

I have just received my ECM800 'Basic' Mic from Cross Spectrum. It comes with two Mic Cal files. I was wandering which Cal file I load into REW, either the 'narrow band response 0 degree', or the 'one third octave band response 0 degree'.
:scratch:

 

There should have been a “Read me” file on the calibration disc that includes the following:

The narrow-band-response.FRD files are designed for use with measurement and analysis programs like Room EQ Wizard, ARTA, and FuzzMeasure Pro that can make use of fine-tuned correction curves. The one-third-octave-response.FRD files are designed for applications where additional smoothing is warranted or for comparision with criteria given in terms of 1/3-octave bands.

Regards,
Wayne

 

There should have been a “Read me” file on the calibration disc that includes the following:



Regards,
Wayne

Thanks Wayne, this is what mine reads:

Frequency Response Files:
The narrow band response x degree.FRD files contain the narrowband (FFT) frequency response response
calibration files for the microphone at an angle of 0 degree incidence (microphone pointed directly at the sound
source), 45 degrees incidence (microphone pointed diagonally with respect to the sound propagation path of the
source) and 90 degrees incidence (microphone perpendicular to the sound propagation path of the source).

The one third octave band response x degree.FRD files contain the one-third octave band frequency response
response calibration files for the microphone at an angle of 0 degree incidence (microphone pointed
directly at the sound source), 45 degrees incidence (microphone pointed diagonally with respect to the sound
propagation path of the source) and 90 degrees incidence (microphone perpendicular to the sound propagation
path of the source).
P.

 

Hi guys,

I don't know if this has been discussed before (not that I haven't searched) but in my quest in finding an affordable and convenient microphone calibration (by substitution) solution I stumbled across this:

(I don't know why the images are not showing up, maybe it's the forum censorship, just do a google on "rockwool tube")
It's rockwool tube used for plumbing purposes, it can be acquired in all kinds of thickness, diameter, density, with or without the foil shell. The idea is that it can be used as a anechoic chamber for high frequencies (best case scenario 1kHz and up) between the tweeter and the microphone.

Now while this is obviously an anechoic "chamber" at certain frequencies, the fact that it's quite narrow will inevitably affect the frequency response (some sort of high-pass filter?). On the positive side, reflections may get attenuated, compared to free air measurements, resulting in smoother overall response.

Also, correct me if I'm wrong but a very reliable and precise method of low end calibration should be nearfield measurement, as described in Claudio *****'s page.

Any comments appreciated
K.

 

Hi.

Is there a Generic Cal file available for the ECM8000 Mic for 90 degree orientation?

 

My Cross Spectrum ''Basic Plus'' ECM8000 will arrive next week. I want to make measurements with this mic+REW+my Tascam 122 MKII. Can you guys tell me what I need to do FIRST with the ECM8000 before I can start making measurements? I only know that I will need to plug in the ECM8000 to the L or R xlr input of my Tascam 122 MKII but that s all I know

Thanks guys!

 

The first thing you'll need to do is copy the calibration files from the disc that will come with the mic to the REW Calibration Files folder on your computer. Then, open REW and go to Preferences/Mic-Meter and open the "narrow_band_response_0_degree.cal" file.

If you're still lost at this point, then you obviously haven't studied the Help Files.

Regards,
Wayne

 

Allright. This seems simple enough! thxz

 

Wayne,

where are the other calibration files are for and why do I have to use the ''narrow_band_response_0_degree.cal'' file?

 

Not sure if you’re asking why you should use the narrow-band file vs. the third-octave, or why use the 0° file vs. some other?

Zero degree is the only orientation file type you’ll have unless you bought one of the upgraded calibration packages. If you did, there would also be 45° and/or 90° calibration files as well. I believe we’ve already discussed why 0° is preferable over the others, right?
If it’s the narrow band file vs. the third-octave that you’re wondering about, Herb covered that at Post #154.

Regards,
Wayne

 

thxz again for always your quick response Wayne.

Ok, so always use the narrow band response. CHECK!

But can you tell me where it is discussed why 0 degrees is the one to use?

(ps. I indeed have the version with 0, 45 and 90 degrees files)

 

thxz again for always your quick response Wayne.

But can you tell me where it is discussed why 0 degrees is the one to use?

My apologies, I confused you with someone else. Here ya go:

http://www.hometheatershack.com/for...hack.com/forums/rew-forum/59458-audio-calibration-file-mike-use.html#post532024

Regards,
Wayne

 

What are you measuring? If you are measuring full range speaker response then the mic should be pointed at the test subject directly (0 deg). This is the only way to get accurate upper mid and high frequency measurements.

If you are measuring bass response of a room at the listening position, then an indirect reading is preferable (mic pointed straight up, 90 deg)

I haven't ever used the 45 deg alignment, but I imagine it could be useful for getting a hybrid measurement of both with the same sweep.

 

I want to measure full range from 0-20000Hz for both my subwoofer and main speakers at the same measurement. Is that possible with REW?

 

ECM 8000 & MacBook Pro - Request for assistance

I'm hoping someone here can give me some help. I am interested in learning how to use REW and need to invest in a microphone. The Behringer ECM8000 seems to be a good starting point but currently I am using an older generation MacBook Pro (2.16 Ghz Intel Core Duo) running Mac OS X 10.5.8. I checked the manual to establish the spec on the internal sound card and audio interfaces on my system and this is what it says:-

An audio line in/optical digital audio in port and a headphone/optical digital audio out port for connecting headphones, speakers, microphones, and digital audio equipment.

You can connect external speakers, headphones, 5.1 surround systems, and other sound output devices to the headphone (f) port. The headphone port is also a S/PDIF stereo 3.5 mini-phono jack. When devices are plugged in, sound won’t come through your built-in speakers. Unplug any headphones or speakers to hear the computer
speakers.

You can also connect external microphones or other audio equipment to the audio line in port. The audio line in port is also a S/PDIF stereo 3.5 mini-phono jack, which does not provide power to a connected device, so you must use self-powered peripherals. Using a Toslink jack-to-miniplug adapter, you can use a Toslink cable to connect Digital Audio Tape (DAT) decks or digital instruments to input and mix your own music.

Questions:-

1. Is the sound card in my machine good enough ?

2. Is it better to get an external preamp/amp with the ECM8000 ?

3. What cables do I need considering that my main interest in REW is to use it to optimise my home theatre system.

4. I am interested in an easy workflow - e.g. long cables so that I can manoeuvre the mic without having to move my computer with it.

5. Are the ECM8000 calibration files available from the REW site accurate enough to avoid paying the extra amount for a dedicated calibration ?

6. Is the Mac Version of REW 5 just as good as the PC version ?

A comprehensive answer from a Mac user or otherwise will be appreciated as I would like to buy the right stuff from the very start. A kind friend on the forum has offered to help me to learn REW but he uses a PC and Windows OS and I can only start once I have all the right gear.

Cheers,

Sam

 

hi i'm new here, but i'd like to know more about the ECM8000. I'm going to buy it but i'm not sure for the price/quality... you guys maybe could help me! there is a similar price mic with better quality?

thank you!
Marco

 

Welcome

1. Deal with Herb from Cross - Spectrum if you can, here is his thread click here http://www.hometheatershack.com/for...ration-sound-cards/15951-cross-spectrum-microphone-calibration-service-usa.html

2. Purchase a calibrated mic

 

Hi Guys.
I did some measurement of five ECM 8000 units in vertical and horizontal possition and I think it might be helpful to see responses from different mics:
Horizontal responses rel. to beyer MM1:


Vertical responses rel. to beyer MM1 (MM1 stays horizontal):


PS: The absolute level of SPL does not match between those pictures (levels bellow 1 kHz should match on each color)