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Measurement Mic Shootout (EMM-6, WM-61A, RS 33-2055, Audyssey) - Page 3

post #61 of 375
Quote:
Originally Posted by bossobass View Post

Ahhh, you're killin' me, man.

I'm not questioning that you get a similar FR with various electrets through your measurement signal chain/calibration files. That much is obvious.

I'm saying flat out that none of those systems approaches the accuracy of the ACOPacific/Edirol UA1000 system below 20 Hz.

The Aud mic roll off should be evidence enough. Do you really think that if the Aud mic is flat to 7 Hz, they would spec it as being down -3dB at 20 Hz? I used to have the Aud mic FR graphs, but they're gone and I see that Audyssey has removed them from their site, but that's irrelevant. There's no chance in this universe that your rig and the Aud cap are flat to single digits. None.

AV Talk's Slartibartfast uses the LinearX M53 with a calibration file (which includes cap/preamp). Here's the LinearX graph of its uncorrected FR, with the grayed out area representing the variation spectrum from one mic to the next.

I scaled and laid over the ACO 7012 mic uncorrected FR. Each ACO mic comes with a FR graph to 10 Hz, made at the time of manufacture. It will always be ruler flat below 10k Hz. The top end is where the ripple is, down -2dB at 40k Hz.



Of course, his measurements are accurate to 15 Hz, the bottom of his measurements, to within 1dB because his mic/preamp are professionally calibrated and a file created and burned to disc that he loads into his software, but the point here is that the ACO rig does not require a calibration file for subwoofer measurements.

Here are the published specs for the ACO mic, pre, PSU and Edirol UA1000:



I bet a months pay that the Aud mic will not be +/- 1dB with the ACO rig.

Bosso

How much does that cost?
post #62 of 375
Thread Starter 
I'll measure with a different rig in a little bit then and see what results are to be had.
post #63 of 375
I have Galaxy cm140's, a couple of ecm8000's including a calibrated one, about 3 audyssey mics and a matched pair of calibrated Earthworks m30's which don't require a calibration file until below 9hz and past 20khz. For normal measurement I dont use one with them. When I get time I will look at the comparison. I do not expect all of the mics to match up very closely at the extremes.

Notnyt Im not saying you did anything wrong. What myself and Bosso are saying is that if your calibration is right on that mic and everything matches so closely then a cheap audyssey mic with no cal is basically dead flat till 5hz. That just does not make any sense. Btw I don't know this for sure but the same Panny capsule or similar might be in most of the units. That's just a hunch though.
post #64 of 375
Thread Starter 
Quote:
Originally Posted by Ricci View Post

I have Galaxy cm140's, a couple of ecm8000's including a calibrated one, about 3 audyssey mics and a matched pair of calibrated Earthworks m30's which don't require a calibration file until below 9hz and past 20khz. For normal measurement I dont use one with them. When I get time I will look at the comparison. I do not expect all of the mics to match up very closely at the extremes.

Notnyt Im not saying you did anything wrong. What myself and Bosso are saying is that if your calibration is right on that mic and everything matches so closely then a cheap audyssey mic with no cal is basically dead flat till 5hz. That just does not make any sense. Btw I don't know this for sure but the same Panny capsule or similar might be in most of the units. That's just a hunch though.

I find it just as hard to believe as the next guy. However, I just reran some tests through different equipment and had the same results. Perhaps I got the luckiest group of mics ever? I don't know. I've included the results below. I'm dealing with a limited sampling of mics, so I cannot compare unit to unit variances, only the mics that I have.

Keep in mind that without the calibration file from CSL, my EMM-6 does not match up. Only after including the calibration data, and setting the RS meter to C weighted do all the mics line up so well. I'm mentioning this in case it would be related to some other source like the soundcard flattening things out or something, even though I validated a flat loopback measurement before testing. I'm really surprised.

The last test was run through my laptop, which was connected to my receiver via the speaker out. All devices were connected to the mic in. The laptop is a Sony VGN-TZ270N. This soundcard is not as good as the one previously used, but seems to do ok until about 7-8hz or so. The EMM-6 sweeps are absent here, since I did not feel like setting it up yet again. The other mics are much easier to setup.

Here is the calibration information for my EMM-6. It was calibrated against an ACO Pacific 7052S which was calibrated by NIST-traceable Scantek. Herb from CSL describes his measurement gear and calibrations here and here.



Here is a graph with the measurements through the laptop. I ran 3 sweeps each about 10db apart for each mic (-3, -12, -22). The only odd thing I noticed is that at higher levels, the Audyssey mic reported higher SPL than the other mics, and wasn't linear with its previous measurements. I reran that sweep a few times to make sure it wasn't a fluke. The volume level for the sweeps was controlled with REW. The receiver volume level and input levels remained constant. I was being lazy and just held the mics by hand for this test.


post #65 of 375
Quote:
Originally Posted by notnyt View Post


The last test was run through my laptop, which was connected to my receiver via the speaker out. All devices were connected to the mic in. The laptop is a Sony VGN-TZ270N. This soundcard is not as good as the one previously used, but seems to do ok until about 7-8hz or so. The EMM-6 sweeps are absent here, since I did not feel like setting it up yet again. The other mics are much easier to setup.



My desktop soundcard has a rolloff built in to the microphone input. Different input jack for the microphone input on my desktop PC's internal soundcard.


Pink noise sound source for the microphone input and for the line input. Red is the FR for line in, and green is the FR for microphone in.



post #66 of 375
Here's the EMM-6 mic against the ACO and extrapolated Aud mic from my exercise:



I'm tellin' ya, my extrapolated curve is darned close to what the actual uncorrected Aud mic response is.

Also, notice the reference mic Dayton used.

Bosso
post #67 of 375
You can start telling regular users to plug in their audyssey mics to their notebooks, then use REW to get some idea of their room response...interesting stuff indeed.

It begs the question, why in 2011 are we just finding this out? What other historical data exists on this topic.
post #68 of 375
Quote:
Originally Posted by penngray View Post

You can start telling regular users to plug in their audyssey mics to their notebooks, then use REW to get some idea of their room response...interesting stuff indeed.

It begs the question, why in 2011 are we just finding this out? What other historical data exists on this topic.



My microphone input is filtered, so that is a no go for me. My PC's microphone input does not produce "flat / accurate" results.

I don't have an Audyssey microphone either!
post #69 of 375
Quote:
Originally Posted by MKtheater View Post

How much does that cost?

No clue.

I bought mine in 2003-4. The UA1000 was around $600 and the PS9200 ACOPacific kit was around $1650.00.

The Edirol UA1000 is long discontinued and I have no idea what the ACO kit goes for today.

Here's the catalog and kit with options, including the SPL calibrator. You could call and inquire. The guy knows his stuff and is cool to talk to about measuring audio.

http://www.acopacific.com/acopaccat.pdf

Main site products page:

http://www.acopacific.com/products.html

Bosso
post #70 of 375
Thread Starter 
Quote:
Originally Posted by J_Palmer_Cass View Post


My microphone input is filtered, so that is a no go for me. My PC's microphone input does not produce "flat / accurate" results.

I don't have an Audyssey microphone either!

That's what you generate a loopback correction file to fix. Just plug a cable into the out and the in, then under preferences you can click 'calibrate' under the soundcard settings. It measures the direct response between the out and in and generates a correction file for this. You can also put your receiver in line and use one of the preamp front channel outputs (set fronts to full and disable eq for this step). The chain would look like pc out to receiver in, receiver front channel preamp output to input on pc. If you have a mic that requires a preamp like the EMM6 it needs to go in line as well.

Doing that takes out all the electronic rolloffs and let's you measure the mics response directly. After this calibration is done and in place you should be able to take a measurement and if everything was done correctly it will be perfectly flat.

My pc has super flat response, but my laptop has a LOT of rolloff. The receiver I have doesn't add any, but my mic amp adds a good bit. You can see the soundcard calibrations used in the close mic graphs I posted earlier.
post #71 of 375
Quote:
Originally Posted by bossobass View Post

Here's the EMM-6 mic against the ACO and extrapolated Aud mic from my exercise:



I'm tellin' ya, my extrapolated curve is darned close to what the actual uncorrected Aud mic response is.

Also, notice the reference mic Dayton used.

Bosso



You mean the reference microphone that Cross Spectrum Labs uses to generate "caliibration" files for a Dayton microphone.

Considering that the calibrated Dayton measured less than 3 dB lower than the reference microphone at 10 Hz, the difference in "accuracy" is hardly worth thinking about.
post #72 of 375
I PM'd Herb (Cross Spectrum Labs) over at HTS earlier today and got the following response:

"I took a quick look at the thread and I'll say from the start that Audyssey mics are all over the place in terms of their frequency response so you absolutely cannot generalize based on the performance of one mic (they have individualized correction curves in the hardware that flatten the mic response).

Out of the box, the accuracy of the ECM8000 (or EMM-6) doesn't hold a candle to a pro mic from ACO Pacific, B&K, GRAS, etc. Those pro mics are flat down to 1 Hz or so. The cheaper ECM8000/EMM-6 mics have high-pass filters that cause a roll-off starting around 100 Hz which severely degrades the low-frequency response. The correction files I generate compensate for this so in theory, which a correction file, you can get a ruler-flat response down to about 5Hz. That said, there is still a bit of error since the measurement procedure I use has some error, plus the amount of correction required for those mics below 10 Hz (which can be as much as 15 dB) may introduce some noise or distortion that can affect the measurement."
post #73 of 375
Thread Starter 
The EMM-6 I have seems to be a good unit and only required 8db of correction at 5hz, 2.7db at 10hz, and 0.6db at 20hz.
post #74 of 375
Thread Starter 
Quote:
Originally Posted by bossobass View Post

Here's the EMM-6 mic against the ACO and extrapolated Aud mic from my exercise:


I'm tellin' ya, my extrapolated curve is darned close to what the actual uncorrected Aud
Also, notice the reference mic Dayton used.

Bosso


Keep in mind the audyssey mic and the WM61A didn't need corretion to match my EMM-6's corrected response.
post #75 of 375
So what conclusions can be drawn from the data we have here?
post #76 of 375
Quote:
Originally Posted by penngray View Post

You can start telling regular users to plug in their audyssey mics to their notebooks, then use REW to get some idea of their room response...interesting stuff indeed.

It begs the question, why in 2011 are we just finding this out? What other historical data exists on this topic.

Well, first - no one asked me....

Second, old RS meters are evidently not nearly as accurate as new RS meters. Lots of respected folks measured them and showed us the results years ago. We've all relied on that since.

Third, and IMO, the most important.....

Anyone with a Windows PC or laptop, a 30 dollar USB sound card, a simple measurement mic, and REW can measure things extremely accurately with just a little bit of effort. This capability did not exist at all 10 years ago, and to be honest, has only become widespread in the last 3 years or so. This is the new and important part.

None of the mic technology is really new. There is a lot of information about the Panasonic electret capsules out there, and the Linkwitz Mod to these electret capsules is not exactly new news either, being dated 1988. Wallin mentioned it in his meter mods back in the 90s. Another mention of the panasonic capsule is the Mitey Mike from Audio Amateur, that's also back to 1990.

The low-cost availability of fast laptops and fast low-latency USB audio cards are probably the fundamentals here. The laptop I use for measurements is a refurbished Dell I picked up for $300, all in, shipped to me. It has plenty of CPU (2.2 GHz, dual core), hard drive (120 GB), and RAM (2GB), and came with Windows XP Pro at that price. Install some free software (REW & Holm), order in a Behringer UCA-202 for $30, and build yourself a lilmike mic for $10. You're pretty well set to handle any acoustic measurement a DIY sub or speaker builder needs to make. That sort of capability was not available for $340 5 years ago. Cobble up a proper set of test leads and you can do impedance and Thiele Small parameters for another $10 too.....do it wrong and you'll be ordering in another UCA-202....

I only brought up the idea of an accurate measurement mic because watching people apply close to 30 dB of "correction" factors that they downloaded from the Internet to their measurement sweeps, then claim frequency response extending into to the single digits (when their measurement hardware can not possibly resolve that) sorta runs against the grain of the "Science" in this site's name.

I figured that if people couldn't find another $10 and an hour of effort to measure the results of weeks of enclosure building and thousands of dollars worth of subs and amps and a bit more accurately, they were at the wrong site, reading the wrong forum. Sorry if that hurts feelings, it is not intended to.

Simply put, data that has 30 dB of correction applied to it is not exactly accurate in my eyes. 30 dB is HUGE, that exceeds the range of a typical analog SPL meter by a factor of 2. There is no need for this.

Not calling anyone out, not naming names, or anything like that. I really just wanted to clear the air and hopefully elevate everyone's game for the cost of a pitcher of beer. A little bit of direction and education does a long way.

Honestly - this has turned out a LOT better than I had hoped. Above 10 Hz, nearly any of mics presented is accurate enough to be trusted, and clearly, modest measurement gear will get us there. Certainly - extending the low end below 5 Hz separates the toys from the tools, but I'm not claiming I can accurately measure data that low, nor do I really care to. I'll leave that corner of the DIY sandbox for the bigger kids to play in.

Big thanks to all that have participated, and huge thanks to notnyt for helping me kick this off, as well as taking things as far down the road as he has. I'll have more to add once things calm down for me a touch. I have stock and modded RS 33-2050s, as well as my EMM-6/Xenyx to add to the mix.
post #77 of 375
Quote:
Originally Posted by penngray View Post

You can start telling regular users to plug in their audyssey mics to their notebooks, then use REW to get some idea of their room response...interesting stuff indeed.

It begs the question, why in 2011 are we just finding this out? What other historical data exists on this topic.

you know what, i am going to give this a try.

i have an htpc, an audyssey mic, and an old RS analog meter. but i don't have a sub.

can i measure my mains instead? if so how? is there a tutorial?
post #78 of 375
Thread Starter 
Same way, just put the mic where your head would be and do a sweep from 0-20,000hz
post #79 of 375
ok, downloaded REW and tried to run it but keep getting "level to low" warning.

any suggestions?

got my audeyssey mic hooked up to the "line in" input on my htpc.

volume on my integra 9.9 is at -20 (which is quite loud for me).

edit: also switched the mic to the "mic in" input on the htpc, still same message.

i have absolutely no idea what i am doing. need to read up.
LL
LL
post #80 of 375
Thread Starter 
First, make sure the level on your mic input is high enough to register readings from the microphone. You can right click the speaker in your systray and go to recording devices to access that. Also make sure under preferences in REW that the channel that the mic is inputting on matches the channel REW is listening on. Sometimes REW will be looking for input on the left, and your soundcard will have mic input on the right. Some systems will require that you start REW after plugging in the mic.

Then, you need to calibrate the mic to REW. Click the SPL meter icon in the top of REW and it will bring up a a meter. Click calibrate, and follow the steps to get everything calibrated. You can use your RS meter here to match the level correctly (place it near the Audyssey mic and use the reading on it) or just guess the level. If you guess, the SPL axis will not be accurate, but you will still be able to see your frequency response.

Low level warnings aren't really something to worry about as long as your readings are high enough above the noise floor. However the warnings you are getting appear to be from no input. Hope this helps.
post #81 of 375
"Big thanks to all that have participated, and huge thanks to notnyt for helping me kick this off"

very interesting thread guys...+1
post #82 of 375
Quote:
Originally Posted by lilmike View Post


None of the mic technology is really new. There is a lot of information about the Panasonic electret capsules out there, and the Linkwitz Mod to these electret capsules is not exactly new news either, being dated 1988. Wallin mentioned it in his meter mods back in the 90s. Another mention of the panasonic capsule is the Mitey Mike from Audio Amateur, that's also back to 1990.

True.

Before REW and just after purchasing my measurement gear (around the end of '03, beginning of '04) I bought Pure Bits Sample Champion, who had just extended their softwares capability to 1 Hz per my ragging.

Just about that time they posted their comparo of a B&K, Sennheiser and the Panny WM-61B electret, which is still partially on their site:

http://www.purebits.com/miccomp.html

He measured to 10 Hz:



So I was aware of the possibility, but preferred to go as low as I could. I also corresponded with the SC author on the subject so I was equally aware of the importance of quality fantom power/interface, etc, to successful results.

Quote:
Originally Posted by J_Palmer_Cass View Post

Considering that the calibrated Dayton measured less than 3 dB lower than the reference microphone at 10 Hz, the difference in "accuracy" is hardly worth thinking about.

Double rolleyes for this one, J.

How would you know it measured -3dB at 10 Hz without the reference mic? That's the whole point of using one, isn't it?

Quote:
Originally Posted by notnyt View Post

Keep in mind the audyssey mic and the WM61A didn't need corretion to match my EMM-6's corrected response.

That's just it. Yes, the Aud mic does need correction to match your corrected EMM-6. Both my measurement and Audyssey's own specs and graphs say so.

I'd really like to get to the bottom of that.

Maybe they took the FR pages down because they use a different mic with a different roll off? Doubtful.

Maybe you got a freak Aud mic? Doubtful as well.

I just don't know at this point. Suggestions and comments, please?

Bosso
post #83 of 375
Quote:
Originally Posted by notnyt View Post

First, make sure the level on your mic input is high enough to register readings from the microphone. You can right click the speaker in your systray and go to recording devices to access that. Also make sure under preferences in REW that the channel that the mic is inputting on matches the channel REW is listening on. Sometimes REW will be looking for input on the left, and your soundcard will have mic input on the right. Some systems will require that you start REW after plugging in the mic.

Then, you need to calibrate the mic to REW. Click the SPL meter icon in the top of REW and it will bring up a a meter. Click calibrate, and follow the steps to get everything calibrated. You can use your RS meter here to match the level correctly (place it near the Audyssey mic and use the reading on it) or just guess the level. If you guess, the SPL axis will not be accurate, but you will still be able to see your frequency response.

Low level warnings aren't really something to worry about as long as your readings are high enough above the noise floor. However the warnings you are getting appear to be from no input. Hope this helps.

thanks, that's good info. but sadly, didn't fix my low level thingy.

giving up for now. will look at it another day.
post #84 of 375
Thread Starter 
Quote:
Originally Posted by bossobass View Post


That's just it. Yes, the Aud mic does need correction to match your corrected EMM-6. Both my measurement and Audyssey's own specs and graphs say so.

I'd really like to get to the bottom of that.

Supposedly there is a good deal of variation between Audyssey mics. Mine measured even without any calibration with the WM-61A(without calibration), the RS meter(with C weighted adjustment), and the EMM-6(with calibration). Perhaps Denon selects the better mics for their higher end units? This came with the 5308 which is their flagship. I have no explanation for why they measure so closely.


Quote:
Originally Posted by bossobass View Post


Maybe they took the FR pages down because they use a different mic with a different roll off? Doubtful.

Maybe you got a freak Aud mic? Doubtful as well.

I just don't know at this point. Suggestions and comments, please?

Bosso

I don't either. I wouldn't think it was right if I didn't run so many measurements with different equipment and at different levels. I definitely see the Audyssey mic exhibiting strange behavior at higher levels, but below ~105db it seems to do fine.

If anyone has any ideas or any tests for me to run, I'd be happy to. I've been over this enough times that I can't fault the results at this point, but I'm still open to suggestions. If anyone sees any fault in the tests I've run, I'm all ears.
post #85 of 375
Thread Starter 
Quote:
Originally Posted by smokarz View Post

thanks, that's good info. but sadly, didn't fix my low level thingy.

giving up for now. will look at it another day.

The first thing to try is make sure you're plugged into the right mic port. Then make sure the level is high enough that in the 'recording devices' screen you can see the bars light up green if you blow onto the mic. You can choose this as the default recording device to make things easier in REW, or just make sure to choose this as the input device in REW under preferences. Drop me a PM or aim me at nyttt if you have any questions.
post #86 of 375
Quote:
Originally Posted by notnyt View Post

The first thing to try is make sure you're plugged into the right mic port. Then make sure the level is high enough that in the 'recording devices' screen you can see the bars light up green if you blow onto the mic. You can choose this as the default recording device to make things easier in REW, or just make sure to choose this as the input device in REW under preferences. Drop me a PM or aim me at nyttt if you have any questions.

thanks, i'll pm you when i get back to this again.

this is getting a bit complicated, and i thought i am good at following instructions.

i did turn the vol up to max in recording device, got 5 green bars (or was it 6?).
post #87 of 375
Quote:
Originally Posted by notnyt View Post

The EMM-6 I have seems to be a good unit and only required 8db of correction at 5hz, 2.7db at 10hz, and 0.6db at 20hz.

That is really good. My Cross Spectrum calibrated ECM8000 needs 17 dB at 5 Hz, 13 dB at 10 Hz, and 4.84 dB at 20 Hz.
post #88 of 375
Quote:
Originally Posted by bossobass View Post



Double rolleyes for this one, J.

How would you know it measured -3dB at 10 Hz without the reference mic? That's the whole point of using one, isn't it?


Bosso


Rolling eyes means sarcasm. I must have missed the sarcasm!


A few general points:

1. An uncalibrated microphone is uncalibrated. Accuracy for any individual unit is an unknown. Individual units of the same model vary. FR of individual units of the same model vary. Uncalibrated means uncalibrated (AKA accuracy unknown).

2. An expensive measurement microphone is expensive for a reason. Better quality element, known, calibrated and documented FR, higher SPL capability, and probably a better phase response (etc.).

3. The vast majority of weekend HT warriors need not be concerned with measured FR below 20 Hz. You get what you get below 20 Hz.

4. I can close mic measure my sealed main speakers 20 times in a row, and the FR below 20 Hz will vary measurement to measurement. Since each one is different, then which one is the accurate measurement below 20 Hz? I do not for one nanosecond think that the use of an expensive measurement microphone will change that fact.

5. I use a RS SPL meter for a measurement microphone because I just look for general relative trends when I measure in room. Kind of hard to get an accurate speaker measurement at the listening position in a room anyhow. Move over a couple of feet and the measurement is different. Room reverberation is always measured along with everything else in the bass department. You can't gate it out!


Below here is an old steady state FR measurement of my system (R, L, SW together) measured at the LP. Calibration factors have not been applied. The SPL C scale compensation factors have not been applied. There is no easy way to apply any compensation factors even if I had them. Accuracy at the low end is an unknow.

At the high end, anything above 8 kHz has unknown accuracy. In reality it just does not matter how that area measures. My speakers tweeters are crossed at 3kHz, so I get what I get. I am not going to EQ the tweeters anyhow!

That being said, I do have a good idea on what is going on in my room. Note that at 10 Hz, the RS SPL meter filters C scale by around 15 dB. How much more drop off is caused by my specific RS SPL meter's microphone is an unknown.


post #89 of 375
Thread Starter 
I can close mic my subs repeatedly, and the measurements will overlay perfectly down to 2hz with at least the EMM-6 and the WM-61A. I haven't tried it with the RS meter or Audyssey mic yet.
post #90 of 375
Quote:
Originally Posted by notnyt View Post

I can close mic my subs repeatedly, and the measurements will overlay perfectly down to 2hz with at least the EMM-6 and the WM-61A. I haven't tried it with the RS meter or Audyssey mic yet.



Well, that is not what I see when I measure. All my sweeps measure different in the low end. RS Digital SPL meter is used as the microphone, with the SPL C scale adjustment factors activated (MIC CAL button is ON).

These sweep measurements were made with TrueRTA. Under normal conditions, I would delete the obvious "bad looking" sweeps, and then average them. REW sweeps are a bit different, and REW goes off track at 8Hz when I measure with REW.


Top set of curves are 15 consecutive TrueRTA QuickSweeps overlaid no smoothing. 110 dB SPL sweeps measured at the close mic SPL meter position.

Second curve from top is the average of all 15 sweeps no smoothing applied.

Third set of curves is the soundcard calibration on and off. Minimal soundcard compensation is required.

Fourth curve down from top is the noise floor of room measured with microphone on and no noise except for the PC fan. No smoothing is applied.

Bottom is noise floor of electronics and cables with SPL meter turned off but still connected. No smoothing is applied.


One note, if you clip the RS SPL meter you can smooth out the curves (AKA SPL meter reads over range). Same thing applies to all electronics in the chain!



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