LF measurement with iPad

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m R g S r

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Joined 2011
#1
This thread is specifically for Low Frequency (hence the Subwoofer forum) measurement with the iPad, using external mics (the internal mic isn't accurate for LF)

Here is a video of a way to get a decent external mic to work with the iPad, using a few things.

YouTube - Broadcast Yourself.

Measurement/calibration Mic, mic port with phantom power, USB wire, powered USB hub or a rechargeable USB power device with a non powered hub. You also need the apple iPad camera connection kit.

Various options:

Mics:

Dayton EMM-6 $50. Should be flat to 18Hz
Dayton Audio EMM-6 Electret Measurement Microphone Allows For Accurate Acoustic Measurements At A Fraction Of The Price 390-801

Behringern ECM 8000 $60. Should be flat to 15Hz
Behringer ECM8000 Measurement Microphone 248-625



Mic ports / USB -> XLR pre amp:

ART USB dual pre $60
ART USB Dual Pre - USB 1.1 Digital Audio Interface USBDUALPREPS

ART USB dual pre from P-E $100
ART USB DUAL PRE PS 2-Channel Preamp with USB 245-8688

9V internal battery should last up to 20 hours powering a mic with phantom power.

C Entrance Micport Pro $150
Amazon.com: CEntrance MicPort Pro: Computers & Accessories
Needs powered USB hub.


Shure X2U $100
Amazon.com: Shure X2U XLR-to-USB Signal Adapter: Musical Instruments

Needs powered USB hub.

Apple iPad Camera connection kit $30:
Apple iPad Camera Connection Kit - Apple Store (U.S.)



I have not made any purchases yet, but would like to in order to get a simple measurement system going. Any input on which I should go for?


UPDATE:

The UMIK works with the iPad with just the apple camera connection kit ($30) and the program Octave.

Here is proof of it working. db calibration is off, but the LF is deff more accurate with this mic attached.

kbc4.jpg
 
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#2
Hi Justin,
I was really bummed about the Apple Java+multi channel snag. I would still focus on solutions that are capable of gated measurement like REW. If you have access to a windows box you could try REW again or use Holm, it's also very good. If you just need this gear for measuring your TH then we could make a short term arrangement possibly.

If your looking to buy a new interface, I know the e-mu I use works well but either the input or output polarity is inverted. The Focusrite SCARLETT 2i2 I noticed recently looks nice, though I have no experience with it personally.
 
#6
m R g S r said:
Is it accurate on LF?
Click to expand...

You'd have to ask them. It is likely broadly similar to the Beringer at that price, but calibrated and with software in the iPad to make the best of it. It is integrated and targeting, which should give it an edge over anything possible at twice the price or more.

So the Behringer mic isn't any good?
Click to expand...

It needs to be calibrated to be worthwhile at all... that cal will give you an idea of where its limitations are. Roll-off in the bottom is of suffiicient amount to make you worry about absolute accuracy, but will give a good idea. To go a serious step up you'll need to spend a lot more, to get really good plan on spending $2-5k

dave
 
#8
The Studio Six gear looks nice. It looks like they are focused on environmental analysis. Their iAudioInterface2 does have some gated measurement capability, though it is not as flexible as most software.

iTestMic specs


Sorry mRgSr, I had confused you with CRESCENDO AKA Justin from your TH-18 thread who is having not much luck with his measurement gear ATM. So please disregard the first part of my post.

REW is available on Mac and PC it's free and can be used to produce anechoic measurements that are useful for comparing what you've built to the model. It's also useful for most of the other typical measurements that you might want for tuning a home theater setup.
 
#9
m R g S r said:
I want to use this for general testing. Maybe some HT setup etc. nothing crazy. Just don't want to spend the $ on shoddy stuff then spend it again on decent equipment. I'd rather just get it done with the first time.

So the Behringer mic isn't any good?

Any mics under $100 that are reliable?
Click to expand...

m R g S r said:
Ehh I'm not prepared to spend that on measurement equipment right now. A house is on the horizon 😉

Anyway the Dayton mic comes with a cal file specific to itself, via serial number. Maybe better luck with that one?
Click to expand...

I'd buy the Dayton EMM-6 calibrated from the CSL

It looks like e-mu is refreshing the line, the 0204 looks like it might be a suitable substitution/replacement.[s/] 😡 NOPE I don't see phantom power.
 
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#15
yup said:
Anyone tried this Dayton microphone yet? It claims to be specifically for the i-pad/phone, etc...

Dayton Audio iMM-6 iDevice Calibrated Measurement Microphone
Click to expand...

The only problem is, we can connect calibrated mics to these little devices all we want, but what guarantee do we have that, say, the input circuit of an iPhone is anywhere reasonably close to flat or has enough bandwidth? Something tells me 20 - 20,000 isn't a design goal for the microphone input circuit on a smartphone or tablet, much less the output we're using to generate the tones or noise.

Wouldn't we have to calibrate the entire device as a whole or do we trust the microscopic analog I/O stages in these devices to be as linear as a proper piece of hi-fi gear?
 
#16
Dr. Dyna,
Excellent point. That is why I was wondering if anyone has tried this so they can comment on the results - possibly even compare it to a more expensive setup.

At $20 for the microphone and $20 for the app it seems too good to be true. That said, when I play music through my home stereo via the headphone jack or air play it doesn't sound like it rolls off the HF or LF (subjective I know).
 
#17
iOS 6 has finally answered our prayers. The built in high pass filter(around 120 or 150 I think) for all audio input, is now defeatable by app developers. Studio Six already is optimized for iOS6 and for iDevices, I'd have to say they are the best right now. I think they are coming out with a new TF app soon because they couldn't get smaart's algorithm to work on the iPlatform.

-iMatt
 
#18
mattlong8 said:
iOS 6 has finally answered our prayers. The built in high pass filter(around 120 or 150 I think) for all audio input, is now defeatable by app developers. Studio Six already is optimized for iOS6 and for iDevices, I'd have to say they are the best right now. I think they are coming out with a new TF app soon because they couldn't get smaart's algorithm to work on the iPlatform.

-iMatt
Click to expand...

I'd still very much like to see some testing of these devices. Perhaps some noise or sweep testing into the microphone input and then played back from the device just to see how much, if any the signal changes passing through the microphone pre-amp and then output stages.

I'm going to hazard a guess and say it's probably not going to be pretty on a cel phone. iPads and tablets might be better if we had ways to bypass their analog stages, but I won't hold my breath that it's reliable enough to judge a loudspeaker with.

I could be very pleasantly proven wrong, however.

Edit: That Studio 6 business looks pretty decent. That doesn't appear to use the microphone input, but rather the data port.
 
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