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Old 21st April 2018, 08:26 AM   #21
Ivo is offline Ivo  Netherlands
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A laptop mic is fun to play with, but there is much unknown about its specific response and a laptop is an large flat thing with lots of acoustic consequences for measurements. I agree that a laptop mic can get people interested in that part of the hobby, but it is a poor tool to suggest to get easy, reliable measurements for a beginner.

I worked with an analog scanning electron microscope from the sixties while doing my masters in biology, was well built and functioning well if you understood its working and limitations, so I'm half with you in terms of lab fu. But there were a lot of things that it wasn't suitable for no matter what. We had cool digital machines in airconditioned rooms for that (I was in a damp and hot basement...).
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Old 21st April 2018, 11:32 AM   #22
bentoronto is offline bentoronto  Canada
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Originally Posted by Ivo View Post
I agree that a laptop mic can get people interested in that part of the hobby, but it is a poor tool to suggest to get easy, reliable measurements for a beginner.
You clearly know what you are talking regarding lab skills.* But even a laptop is just fine for a great many everyday measurements, esp stuff like cranking up the EQ or setting benchmarks for returning to in the future or eyeballing waterfall room acoustic displays and lots of stuff.

Your hearing satisfaction is the ultimate criterion and no measurements can over-ride your judgment. Except for anechoic work, indoors acoustic measurements are fraught, as anyone with any experience can tell you. All you can say is, "I did thus-and-so and here're the curves I got".

Also good to own an SPL meter because an absolute reading is often meaningful. True, it adds nothing to your ears but it does help at this forum when others want to know how loud a sound was you are testing. Some SPL meters can double as mics and the whole test shebang, such as the venerable Radio Shack model.

In terms of price, a laptop mic is free and REW is honourware.

A calibrated IMM-6 is usually on sale at PE, maybe $17 and a cable another $5. I use a camera mini-tripod with some trick DIY bits to hold it. If you look at how closely it tracks my fancier EMM-6 (second graph) except for lower bass (and you can take my graph as a re-calibration of the lower bass vis a vis the EMM), you'd sure want to buy one. I have two.

I don't have experience with a UMM-6 (USB) mic, but the price is right at us$65 when on sale, plus a cable and mic stand. It would be nice for outspoken critics like anatech to simply post curves for his set of mics.

My calibrated EMM-6, sometimes as little as us$40, is wonderful and seems to do the job. But it needs a phantom power supply and other pre-amp capabilities in order to know what you are doing and control it. I use a Behringer Xenix 1204 mic mixer (us$225), a DAC (say, $120, or like mine, $4 at the Salvation Army store), mic stand (about $35), and XLR cables (maybe $15).

B.
*just a way of saying, "glad somebody agrees with me"; anatech and I seem to disagree although I'd guess only one us has been on a Board of Directors of the National Research Council of Canada where decisions of dollars versus research benefits come to roost.
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Last edited by bentoronto; 21st April 2018 at 11:48 AM.
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Old 24th April 2018, 06:28 PM   #23
Jared is offline Jared
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Quote:
Originally Posted by bentoronto View Post

And anybody with acoustic measurement experience would know that the wild bumps and dips in the curves are not shortcomings of the mikes.

B.
I am confused by this statement and the graphs in the first post. How do you use a mic to measure frequency response of a subwoofer when the response of the mic looks so terrible? Am I reading correctly that the response is from 45 to 70 db meaning a 25 db difference? I would have thought the calibration file would get a close to flat response curve for the mic?
I feel like I need ground level baby steps for venturing into actual speaker measurements. If the mic response is that irregular I do not get how I would be able to measure the response of a speaker other than to compare it against another speaker?
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Old 24th April 2018, 06:59 PM   #24
bentoronto is offline bentoronto  Canada
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Originally Posted by Jared View Post
I feel like I need ground level baby steps for venturing into actual speaker measurements. If the mic response is that irregular I do not get how I would be able to measure the response of a speaker other than to compare it against another speaker?
You're the person I started this thread for. Time for you to try REW.... even just using your laptop mic. Why not?

The mic curve for the fancy EMM-6 is the flip-side of the individual calibration corrections I posted in #8 - about as flat as anything in the acoustics world.

The ups-and-downs of the post #1 are the reality of my smallish music room as picked up in one spot with sine-wave testing displayed in one format.

Such curves are related to some aspects of listening experience but freq response (esp one spot in the room as heard by a small mic) should not be thought to characterize all of the listening experience or even being definitive vis a vis your experience of tone compass.

I'd say most curves are used by folks like you and me as part of an iterative process where you are comparing before-and-after. And, as I showed in post #1, even a laptop mic is just dandy for a beginner.

B.
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Last edited by bentoronto; 24th April 2018 at 07:01 PM.
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Old 24th April 2018, 07:46 PM   #25
Jared is offline Jared
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Am I understanding then that the mic's ARE very flat, but the charts you generated are the real world measurements in your specific listening environment? IE the 10 db difference between 20 and 30 hz is an artifact of your environment, not the mic?
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Old 24th April 2018, 08:06 PM   #26
Ivo is offline Ivo  Netherlands
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Originally Posted by bentoronto View Post
*just a way of saying, "glad somebody agrees with me"; anatech and I seem to disagree although I'd guess only one us has been on a Board of Directors of the National Research Council of Canada where decisions of dollars versus research benefits come to roost.
Ok, you really know science through and through, cool. :-)

Oh, please don't get the impression I was good or efficient at practical research. I had good ideas and found the most interesting things, but never related to my research topic. ;-)

The electron microscope is a good illustration. After months of discovery, I could produce imagery straight out of the machine that others achieved after intensive image processing by the in-house graphics specialist. In some ways wonderful, but the machine was retired afterwards (so useless skills) and in the mean time I had spent less time on actually finding the microscopic anatomical feature I was looking for.

Later I moved on to science education and did some multimedia things. Produced little content, because I was discovering/struggling with the tech behind it. You can do a by yourself, with modest means, but it takes time and every workaround makes you less efficient and effective.

I think there is good and usable hardware in laptops and smartphones, but you have to know a lot of stuff to make meaningful use of it. The process of discovery, or simply lack of usable results, are inefficient and discouraging to someone starting out.

(I realized finding out "stuff" is not the same as doing science and moved out of it. I work more or less as a social worker now and out of procedural necessity work perhaps as structured and analytically as I would have as a Phd student. Go figure. There is more personal contact though, compared to that damp and hot basement. Did I mention the jars with dead fish around me? The smell of alcohol and formaldehyde? Why do people science at all...)
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Old 24th April 2018, 08:07 PM   #27
bentoronto is offline bentoronto  Canada
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Originally Posted by Jared View Post
Am I understanding then that the mic's ARE very flat, but the charts you generated are the real world measurements in your specific listening environment? IE the 10 db difference between 20 and 30 hz is an artifact of your environment, not the mic?
The two mics are in close agreement and both are notably flat, as per calibration in post #8. Yes, that's my system-plus-room, one spot (for purpose of comparison between mics), one day, and typical enough of curves posted by others.

Although you have no experience of your own for comparison and since builders on this forum are notably shy about posting their own rooms (even some of the most vocal persons in this very thread), I sense you are appalled at the non-flatness of my results?*

You can also say that my curve (1/12) is substantially plus-or-minus 5dB, 20 Hz to 15 kHz (with some boost in the bass as many good listeners know to do). Nothing to sneeze at.**

B.
*over the years, I've posted many REW curves; sure would be nice if everybody had skin tough-enough to do so too
** there's a bit of EQ in there, but I have enough spare DSP to make it as flat as I want it to be
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Last edited by bentoronto; 24th April 2018 at 08:14 PM.
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Old 24th April 2018, 09:22 PM   #28
Xoc1 is offline Xoc1  United Kingdom
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Not every laptop has a built in microphone but most have a microphone input that is compatible with an electret capsule.
Usually for a mono mic input the tip is the signal in, the ring is the voltage supply, and the sleeve is 0v ground. The internal components of the sound card usually mean that no resistors or capacitors need to be added to make the capsule work.
So I got an electret capsule and wired it to a 3.5mm jack using some screened cable with the tip & ring connected to the capsule positive and the sleeve connected to the capsule ground. The capsule was mounted to a plastic tube with some insulation tape
In a totally non scientific way, 2 pics. The photo shows the home made mic., on an old Dell d630 one trace kicks in at 150hz and has a peak at 3.5k - this is the laptop internal speaker. The other trace is a battered stage monitor plugged into the laptop headphone output (no amplifier used ).
Dell D630.jpg
Screen shot is a Dell Precision M6600 laptop Red trace is internal speaker and internal mic
Blue trace is internal speaker and hand held home made microphone.
Dell Precision.jpg
Capsule was a Panasonic wm-61a
Have Fun
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Old 25th April 2018, 01:37 AM   #29
anatech is offline anatech  Canada
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Hi Ben,
So ... what does being on a board have to do with real experience in measurement and acoustics?

Just curious. I'm taking your statement at face value. Also, I did know someone else who was on the board as well. Really nice old fella. Pretty unplugged though.

-Chris
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Old 26th April 2018, 12:43 AM   #30
Jared is offline Jared
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Quote:
Originally Posted by bentoronto View Post
I sense you are appalled at the non-flatness of my results?*
I am not sure I would have chosen the word appalled, maybe astonished...

Quite frankly, I have not done anything in home audio in over a decade now - I got to the point that I spent so much time at work, at a computer, that an investment in a mid grade DAC, headphne amp, and headphones made the most sense for me. I started becoming interested recently in doing some crossovers again and have boxes of components laying around to build a pair of TLs, line arrays, and a 6.1 home theatre setup and it seemed like a good place to start off was to measure things. Personally, my listening environments will be where the speakers fit on a desk, where they work in a room arangement etc, nothing dedicated, so I do not have pre conceived expectations of greatness, I just had confusion of a flat mic curve or not. I am in agreement with you now that I understand what that curve was - my laptop mic, cell phone mic, etc will be totally adequate for my initial learning. Whenever I get some actual measurements I will not be ashamed to post them at all, I am sure they will be terrible, but at least be a baseline to be sure that changes are for th the better, or even an idea of what the changes I think sound better actually look like...
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