# Audyssey microphone and RTA?



## mooch91 (Apr 6, 2008)

Off the wall question... I've got a home theater with Audyssey microphone setup, I've now got a laptop, I'm sure I can get software...

Not very interested in precise RTA measurements but looking to better understand the adjustments I'm making to my system on a macro scale. And look for obvious holes and peaks.

Is it possible to use the Audyssey mic with RTA software on my laptop? Just looking to minimize investment on something that I'm sure is useful but will take me a long while to learn.

Thanks.


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## ibanzil (Jun 29, 2008)

i know it works with your mic plug in, not sure on accuracy. I do know that the graphs imprint shows for the before is pretty good. I used an audio control rta and the imprint graph was pretty spot on.


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## mooch91 (Apr 6, 2008)

I would figure curves for correction would be required.


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## Weightless (May 5, 2005)

yes it can be done, but it wont be very accurate. It all depends on which sound card you have. But for learning the ropes, it's a great place to start. 

Try these to [play with:

True Audio: Audio Spectrum Analyzer and Loudspeaker Design Software

the 1 octave is free

jDFT - Download

and 

ARTA home

have fun


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## mooch91 (Apr 6, 2008)

Yeah, I'm thinking this isn't as "DIY" as I initally thought.

Pretty sure my laptop sound card would be no good. Tried calibrating it with TrueRTA only to find a jagged calibrated signal. Would require a better input source.

No evidence that a correction curve exists for the Audyssey mic from other internet searches. Would probably need to invest in a calibrated mic.

Then the cost of the software.

While it would be a great tool for helping me understand why some systems/tunes sound good and why some don't, seems like a big investment to get scientific.

Thanks.


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## dbiegel (Oct 15, 2006)

Audyssey's frequency response measurements seem to be astoundingly accurate... but without the software, I'm not sure how useful the mic would be. For one, there's no available calibration file that I know of -- it's built into the Audyssey software. You might be able to extract it from decompiling the DLLs, but I haven't had much success with that so far. That is particularly sad, since according to Chris (one of the founders), they use a special manufacturing process to get amazing unit-to-unit consistency, so this would be one of the few mics out there where a generalized calibration file could actually work well. I guess they don't want people to just buy the mics from pacparts. Regardless, a lot of the Audyssey magic seems to come from their proprietary clustering and spatial averaging algorithms, which obviously you wouldn't have the benefit of if you used it with third party software anyway.


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## rlee777 (Apr 28, 2009)

I tried this! I took my Denon Audyssey mic and plugged it into my laptop input and used TrueRTA. I have tried an external Soundblaster USB soundcard, but for some reason the self-calibration looked really bad. With the internal laptop soundcard, the main problem is in the extreme ends of the spectrum.

I read a post where someone compared their Audyssey mic to a calibrated reference mic and found good accuracy up to 1.5khz, then the response of the Audyssey mic slopes downward to -4db at 20khz. I suppose you can build a .cal file using this info. I think the best way to use this setup is to start with a perceived balanced response audibly, then use the Audyssey mic/RTA setup to identify peaks and valleys to equalize. A smooth response is your goal, not necessarily a ruler flat graph because the mic does not have that type of response curve. See...this "cheap" setup can be useful!

BTW, the Behringer ECM8000, that many like to use as a budget calibrated mic, does not have a consistent response even with the downloadable .cal files. Accurate measurement microphones are $$$.


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## mooch91 (Apr 6, 2008)

dbiegel said:


> Audyssey's frequency response measurements seem to be astoundingly accurate... but without the software, I'm not sure how useful the mic would be. For one, there's no available calibration file that I know of -- it's built into the Audyssey software. You might be able to extract it from decompiling the DLLs, but I haven't had much success with that so far. That is particularly sad, since according to Chris (one of the founders), they use a special manufacturing process to get amazing unit-to-unit consistency, so this would be one of the few mics out there where a generalized calibration file could actually work well. I guess they don't want people to just buy the mics from pacparts. Regardless, a lot of the Audyssey magic seems to come from their proprietary clustering and spatial averaging algorithms, which obviously you wouldn't have the benefit of if you used it with third party software anyway.


Works great on the home Onkyo, actually gets me a sound I enjoy listening to and can't come close to in the car. I wasn't so interested in actually having the tuning software for the car (right now), more the ability to just visualize the differences between home and car. Since I've got the laptop, got the Audyssey mic, got the RTA software, I thought it would be a cheap way to get the RTA rather than investing in other hardware.

I suppose someone might be able to generate a calibration/compensation file by comparing the Audyssey mic to a known other calibration and subtracting the difference.


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## 14642 (May 19, 2008)

If there's a setting in the Audyssey gear that is intended to provide flat response, the foolowing will work: 

1. Determine the output voltage from the microphone with the test signal at a reasonable level. Use a AC volt meter.
2. Measure the level of the output of the piece of gear when it outputs the test signal.
3. Rig up some way to boost or attenuate the test signal so it matches the voltage you measured from the microphone.
4. connect the output of the EQ to the microphone input through your level matching device. 
5. Run the Auto EQ routine and choose a setting that is supposed to yeilda flat response.
4. Once the Auto EQ has finished, input pink noise or some other test signal that you can generate into the regular signal input of the EQ and record the output with your test gear.
5. The response you record will be the microphone correction filter. 

Basically, you want to input a test signal that you know is what the microphone would record as flat to eliminate the effect of the room and some speaker that the EQ is trying to measure.


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## npdang (Jul 29, 2005)

Can't speak to your receiver's mic, but the one that came with the Alpine h650 was spot on with my calibrated Praxis mic.


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## mooch91 (Apr 6, 2008)

I know the sound card in my laptop is junk, but I've got to assume the Audyssey microphone is reasonably flat. At a minimum I should be able to get some high-level measurements and at least a relative look between tuning changes.

Here is what I've managed so far, 1/6th octave smoothed; all curves are of both channels simultaneously (doing one channel at a time was not overly different than what was observed here):









Some interesting observations (experts, please chime in):

Seems to be a shelf on the sub since I do have it crossed at 100 Hz (12 dB/oct) and raised up fairly high. Toning it down gives a weak bottom end, but I'm probably looking to generate a little bit of a peak somewhere in the response rather than leaving it level across the board? Not sure what the best response would be down here, and I think I need to do some more reading on weighting to ensure I'm tuning in the right direction.

Peak at 500 Hz, dip at 900 Hz. With the limited EQ I have available (3-band in the Kenwood head unit), I'm figuring I can only fix one of the two issues here... 

A little bit of a dip at 4 kHz too (passive crossover on my Alpine REF set?). Not much I can do here either. 

Top end rolls off fairly well.

This is an awesome look at my system frequency response and will really give me a good tool to understand tuning!

For fun, I measured response with my sub turned off:









Sure enough, that peak at 150 Hz is my own creation, +2 dB on the head unit at 150 Hz with a Q of 1.5. Also shows that what I'm seeing at the lowest of the low frequencies may be noise.

The only thing I really don't get is the relative delta (>30 dB) between the vallies and peaks in the measurement. I can't be that far out of whack.

Very interesting, I'm going to keep tweaking...


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## mooch91 (Apr 6, 2008)

Autiophile said:


> Did you measure at only one position? You might be surprised to find how much the response varies even with seemingly minor changes in mic location. A good tactic is to take several measurements in various positions in the general listening area and then have the software average them.
> 
> What signal is being used for measurement? What is the time window for your measurement?


Source is pink noise, assuming 0 db, burned to disc from one of the lossless reference collections posted here. I did measure at only one position (top of headrest), but I'm planning on taking my makeshift Audyssey microphone stand out to the truck and situating it at ear level in the seat to get something that's more accurate to listening position. I'll try a few different positions to average (makes sense--I guess that's why Audyssey even recommends 6 positions minimum). Time window is a continuous measurement (80 Hz - fast) averaged at "10" using 1/24 octave resolution, snapshot taken when the curve stops bouncing around. Smoothed to 1/6th octave.


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## mooch91 (Apr 6, 2008)

I'm going to stop for the night... I'm not convinced I'm getting an accurate reading the way I'm doing this. I've been moving sliders +/- 8 dB and I don't see sharp peaks and vallies in the response like I'd expect.

This is about the flattest I got it, but boy did it SOUND flat and I seem to be opening a big valley around 250 Hz that I won't be able to fix with my EQ:


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## mooch91 (Apr 6, 2008)

And where I left it:










Any thoughts on what kind of a curve I should be shooting for on that low end? For a little bit of low end emphasis, should I be targeting a peak, maybe more of a transition between the low and the midbass region? Thoughts please.

Thanks!


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## ibanzil (Jun 29, 2008)

you should try to get rid of those peaks. you cant trust everything the rta says. if you see a huge dip or peak... use some test tones of different frequencies and see if it actually sounds that much higher/lower than the bands surrounding it.


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## mooch91 (Apr 6, 2008)

Autiophile said:


> It looks to me like you have some cancellation between your midbass drivers and your subs. The fact that each is higher outside of what I presume is the crossover region seems to indicate destructive interference. Changing the phase of the sub might help.


More likely, some very weak midbass (which is what I've assumed by ear)? I believe the dip was there even when I had the sub turned off.

Some great advice on sweeps and gated measurements, thanks. I need to do some reading up to understand the concepts a bit more (my head is hurting just trying to get it around the simple RTA concepts thusfar).


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## mooch91 (Apr 6, 2008)

Any place I can get gated lossless/WAV pink noise tracks that I can burn to CD?


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## mooch91 (Apr 6, 2008)

I wanted to take a minute to post a tutorial on how to set this up in case someone else was interested in a "poor man's version" of an RTA (not that the $100 version is too expensive, but this is a great way to do some learning without buying things you might never use later). 

GOAL: Set up a laptop-based RTA to get some gross system measurements using items I already had available -- new Dell Inspiron laptop (with integrated IDT sound card), Audyssey home theater microphone (for Onkyo Audyssey calibration), and TrueRTA software available online.

CAVEATS: My laptop's sound card definitely doesn't appear to be suitable for precise measurements and I've been unable to confirm the linearity of the Audyssey microphone at this point (although there is some anecdotal evidence from the thread above that it's fairly linear). Again, my goal was to get some gross measurements to better understand the basics of tuning and the limitations of my system.

STEP 1:
Following the TrueRTA calibrations I've seen online, I began by setting up my sound card for the operation. I needed to use the "microphone" (not line) input for the Audyssey microphone, so I set the volumes for wave output and microphone input to max, and deselected or muted the others. I left main system volume at a moderate level. One thing that took me a while to figure out was that my laptop attempted to automatically select the input depending on whether or not the microphone was plugged in, and there were a few times where it would switch back to the internal mic instead of the microphone input, creating some confusion.










STEP 2:
The TrueRTA calibrations I've seen online suggest using the laptop sound card as both the signal generator and the input device. Basically when testing your system, you'd connect the output from the laptop sound card to an aux input on your stereo and then connect the microphone to the input to the sound card. TrueRTA will generate quick sweeps, sine waves, and pink noise for you. In order to use this functionality, you need to perform the "sound system calibration" on TrueRTA's "Audio I/O" menu. You loop the sound card input and output using a 1/8" cable.










Here's where it starts to go bad using the laptop's integrated sound card.

Performing the calibration should yield a straight line across the frequency range. Here's what I got:










The sound card is really not linear in its output or its input, or both. After the calibration, I actually ran some pink noise with the sound card input and output still looped, and this is what I saw:










Looks decent (+/- 1 dB) from 100 Hz on up, but falls apart below 100 Hz, as one would expect from the plot created immediately after calibration.

I guessed that the sound card was probably worse on the output, so I decided at this point that using TrueRTA and the laptop sound card was not the way to go for this experiment. Instead, I decided to use an external source for my frequency response tests, plus it will be a lot easier to drop a CD in to my sound systems for the measurements rather than try to connect the laptop up to an aux input. I've got a ton of reference, tools, and calibration discs and I picked one that had a 0 dB pink noise track. I ended up using the laptop for microphone input only.

STEP 3:
Now, how to check the calibration of my sound card for the microphone input by itself?

What I did was to connect a CD player line output direct to the microphone input on the laptop. I played the pink noise track and I used TrueRTA to monitor the response. Averaging at 100 and giving the response some time to settle down, here's what I got:










Taking a look, the response measured without a lot of variability, but it sure was not linear. About a 15 dB swing from the low end to the high end.

STEP 4:
So I used this information to create a "pseudo system calibration" using the microphone calibration function built in to True RTA. Bascially, I used the microphone calibration function as a system calibration function (since I don't think TrueRTA lets you generate your own system calibration curve and apply it, you need to use the built-in calibration functionality to do so which wouldn't work too well with my external source as TrueRTA expects a series of quick sweeps to calibrate).

First I used TrueRTA's "shift" function (on the "utilities" menu) to center the curve at 1 kHz and 0 dB. Then I exported the data to a "txt" file using the "export data" function on the "file" menu.

Selecting "open a mic calibration file" on the "audio I/O" menu, and bringing the txt file back in allows TrueRTA to correct the input using the data generated from the calibration check in Step 3. 

Once the mic calibration was applied, I re-checked the pink noise track from the CD player line out connected directly to the mic in on the laptop, and this is what I got:










Not too bad! +/- 1 dB across the spectrum which I thought would be pretty good for what I am trying to achieve.

TrueRTA was now set up to take some frequency response measurements using my Audyssey microphone. From this point forward, however, I can only assume the Audyssey mic is linear across the range and there is probably some error in my measurements if this is not the case, but I should have a good system for taking some gross measurements with this setup.


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## bobdole369 (Mar 29, 2008)

Not exactly a dead thread yet and very good beginner and poor man info here!

It's so funny - I did exactly this too! Found my wifes laptop and grabbed the audyssey mic, thinking "well shoot its got to be good". 

Similar results as the OP - not much change eqing like crazy.

I've discovered why - I need to gate the thing - reflections and all that. 

ECM8000 and calibration will come in time - I found it better to set by ear, will revisit this soon.


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## Sulley (Dec 8, 2008)

Well I done everything you said, my Laptop card was a perfect straight line after calibration. So off to my car I went, Heres what i got. Took a few try's to even get a response so theres no EQ just as is response. I don't whats going on below 100hz.....










So any input on what i should do now would be great. thanks


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## 14642 (May 19, 2008)

increase the fft size for better resolution at low frequencies.


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## Sulley (Dec 8, 2008)

Andy Wehmeyer said:


> increase the fft size for better resolution at low frequencies.


Hmm, I just spent the last half hour going thru the help file and Google searches with no luck on how to change the FFT size. I know its on 8k now and can be changed to 64k but i have no idea how to do it. Maybe you can help??


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## s4turn (Jun 17, 2009)

\bit of a thread dredge 

but interesting thread

I just ordered a Mic Mate XL Classic and a ecm8000

I might be able to compare them, as I have 2 audessy Mics, one from a Denon receiver and a newer one from a Onkyo receiver

plus an audigy 2 ZS!


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## Sulley (Dec 8, 2008)

s4turn said:


> \bit of a thread dredge
> 
> but interesting thread
> 
> ...



This would be Great, I have a mic from a Onkyo TX-SR507 so it would nice to see, Looking forward to it if its doable for you.


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## Hernan (Jul 9, 2006)

I don't know if the Audyssey microphone has a built in pre amp. If not, you will probably need one.

I use a simple ECM8000 with Holm and they work perfect, more than enought to car audio. The soft is freeware and solid. Lots of info at DIYaudio.


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## Sulley (Dec 8, 2008)

The Audyssey mic didn't work on the line input, But it did work on the mic input of my PC soundcard.


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## s4turn (Jun 17, 2009)

i have a audigy 2 NX external sound card, I was getting mixed up with my internal Audigy 2 ZS I sold ages ago 

audessy mic from my onkyo 706 and from the 1708 denon, they are properly the same?
I know of a person who has the alpine imprint Mic and ecm8000, m-audio preamp .. so that might be worth a comparison too if he can be bothered 

Mine havent arrived yet  just ordered it from ebay a few days back


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