My ECM-8000 Mic just arrived. I have downloaded its Generic Calibration file from the Downloads section of HomeTheaterShack & loaded it into REW. At this stage, I need to know two things--
1. My Sony Vaio Laptop has a dedicated Mic input, so I guess I will not need any Mic preamp for using the ECM-8000???
2. If I was to measure one speaker at a time, does the Mic need to point flat to the centre of the front-wall, or point towards the top of the front-wall, or point towards the speaker being measured???

The ECM-8000 is a condenser microphone and thus needs phantom power (15-48 V) to operate. It also needs a preamplifier so the best option is to purchase a cheap interface with a preamp that offers phantom power.

Regarding microphone orientation when measuring and the Behringer ECM-8000:
Why point the mic at the ceiling?

1) Any clean (most modern are) pre should work.

2) Point it forward between the monitors and slightly up. There is a long thread on the subject sorry I don't have it bookmarked.

Hi Jolida

1. You can do that. However, do you have any way to connect line out to line in on your laptop to calibrate the soundcard? Laptop soundcards are not noted for their quality. The default for REW is to use the right channel for measuring. So, you need to connect Right line in to line out first, to loop the signal and create a Cal file for the "soundcard", separate to the mic cal file. It's all in the "getting started" help file.

2. Point the mic vertical towards ceiling in your chosen listening position , about ear height.

Why point the mic at the ceiling?

So according to measurement; straight up would be the optimal orientation for the ECM-8000.

Unfortunately, some measurement microphones are labeled “Free Field” but they in fact behave as “Diffuse Field” microphones:
Why point the mic at the ceiling?
Very confusing indeed.

Thanks

Whoa. Straight Up as in Pointing towards the ceiling just above the listening chair??? Or as Glenn pointed out, aimed between the two speakers with a tilt upwards ?
The Laptop has Only Mic in & Headphone Out. So making a Cal file for the card doesn't seem possible. Is it very important to make one??

Why point the mic at the ceiling?

There is not definite answer here since some measurements indicate that the ECM-8000 behaves more as a diffuse field microphone and is flat at 90 deg incidence. If so, you should point it at the ceiling (straight up).

But don´t worry too much about all this; it´s only affecting the higher frequency range and this range is seldom problematic (assuming you take care of your early reflections) so you can pretty much ignore anything above about 3 kHz (where the differences start to show).

And regarding the Soundcard Cal file.. Can I go without it?? Else I need to buy an external mic preamp. Saw one in the store where I bought the Mic from. Is this Good..??

Yes.

Here is a typical soundcard FR (below), before calibration (48kHz sample rate). Above 3k it starts to become less flat. However, it maybe looks worse than it is, check out the scale! (~+/- 0.2dB, 20Hz-20k). Your laptop soundcard of course will be different?, just so you are aware.

+1

IMHO, in measurements "for home recording purposes" consistency for comparison purposes is more important ie don't point the mic up for "before" and at the sound source for "after" treatment.

And it indicates why you normally don´t need to bother about calibrating the FR of your soundcard, (even if low budget) if used for room acoustics measurements. At least not in small to normal sized room with small to normal monitors.

Yea I do agree in the grand scale of things

+1

So all that being said, is it alright to start-over with taking my first measurement without bothering about calibrating the soundcard? Or have I not understood something?
Jens, u say it's ok to kinda close one-eye to the FR above 3k because it does not matter as much compared to everything else below that range. Well my main purpose of buying the ECM-8000 was thinking that it's much better than the Radio Shack SPL meter I already have (which is again said to be good till about 3k) & had no hassles of using an external preamp for phantom power or whatever..

That soundcard is (roughly) +/- .1dB from 30Hz up to around 20kHz..... and above and below those (so 20Hz to 24kHz is only off by (again roughly seeing as the graph is not accurate below +/- 1dB) +.1 to-.3dB max. IMHO a 1/3dB variance is a non issue..

I would not bother calibrating a card that was that close to being spot on.

The huge dip beyond 24kHz is meaningless, as is the drop off below 20Hz for the purpose of analyzing a small control room for treatments.

Rod

Well; it matters, but unless you have strong early reflections (that you locate by checking the ETC) or possibly a bad/malfunctioning monitor; there’s not much you can to about the response above 3 kHz anyway and even if your FR graph has a tilt in some direction, you can still observe possible comb filter artifacts above 3 kHz caused by earl reflections. As long as you are aware that any possible HF tilt in the RF might be due to the direction of the mic you´re using, you should be fine.

Rod

We are in agreement (post#13) +1

Just wanted to point out that's mine, not the OP

lol, Kinda figured that based on the wording of your post.

Rod

actually, i have a question, is it essential to get the calibration file of the mic loaded in rew? i have the ecm8000?

thanks

If you have a cal file, why not use it?

Unless you´re doing comparative measurements, there´s no reason not to use it.

true

make sense

tks

I have mixed feelings about that Jens....... if his mic had been calibrated I would agree completely it would make sense to use the file.

However, are you really better off with a generic cal file? Someone goes purchases a mic and has it calibrated - then puts that file out (I believes it's years ago now) for public download as a generic calibration file - what's the value of that file for his mic?

There's a good reason that mics are calibrated individually.

Is it really better than none at all?

Rod

I´m naturally assuming the cal file is correct. If not; I absolutely agree with you.

He did not have his mic calibrated based on his first post, The manufacturer does not offer calibration for those mics - he would have to pay to have his calibrated - which would cost him as much as the mic itself......

I missed that piece of info. But on the other hand; it was not the OP asking.


EDIT:

Just to be clear here: I have no experience using the ECM8000 and I don´t know whether or not it is individually calibrated. If not; I guess there are better options, even in the budget range: http://www.minidsp.com/products/acou...urement/umik-1

The results from ECM-8000 mic seem to vary at lower and higher frequencies.

Below: A report on an individual ECM-8000, as well as diagrams after tests on 130 pcs and 85 pcs versus a reference microphone.

(Sorry, I have forgotten the source of the German diagram, Ton ... something ?)

That's some pretty large variances there - a very small frequency range where they are relatively close.


Rod

Thank u all for the detailed replies. I just bought the Mic today from a local shop here which sells Musical Instruments. The Mic is not Calibrated. So am I better off not loading the Generic file itself?? The soundcard calibration has been explained well & I guess it wont hurt to not bother about doing so at the moment. So i can skip that as of now & proceed with the Measurement process. But a clarification on whether to use the Generic Cal file for the ECM-8000 or not would be really helpful.

Users of the ECM-8000, what preamp are u using for Phantom power? Or are any of you using the onboard soundcards of the Motherboard which provides both Mic as well as Line level in/outs??
Also, a big thank u to Dan for guiding me via PM & providing details using his link :-
https://gearspace.com/board/8451984-post80.html
I just Love GS. And we are very lucky to have all u fine people around.
Thanks to Jens for taking the time to help all of us. I just wish u & Dan could get back together.
Get back Dan..!!

yes you need phantom power otherwise it wont work.

Microphone - Wikipedia, the free encyclopedia

i guess you can use your onbard soundcard but going via a preamp with phantom power switch on (+48v) then line input.

i guess you havent got a "proper" soundcard but maybe you could borow one from a friend? one with a mic input and phamtom will be a plus

Comparing the calibration file with the wide variances I see in the tests of those 130 sample mics - there is probably a greater chance to make things worse than you have to make them better.

Picture (just one example) at 10K - the cal file indicates a correction of 3.4dB - which would work with 1 of the 130 mics sampled...... however the vast majority of those 130 mics are floating in the 0 to 5dB range - a lot of them in the 5-7.5dB range - and one is +10dB - adding 3.4dB to any of those would be real bad in terms of understanding what's really going on in your room..

I would just live with the mic and forget the cor file.

Just to be clear - I would never use a calibration file that was not generated for the mic in question. If you want a cal file - pay the money and have your mic calibrated.

Note that I am not suggesting this is necessary for a mic like this used for a home studio - what I am saying is that the odds are you will be worse off with a cal file from a different mic.

I do not believe calibrating a mic (in the case of Joe's home studio) is really necessary.

Rod

Rod