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iPhone SPL Meter

post #1 of 30
Thread Starter 
Does anyone have any experience with the SPL meters available on the iPhone/iPad app store? It appears that the Radio Shack meter has been discontinued. I was hoping to give one of the meters available on the app store a shot.

I understand that they will most likely not be 100% accurate but I just want a meter that gives me a good general idea of sound levels with my system.
post #2 of 30
They work, but not as good as more professional equipment.
post #3 of 30
Aha, that explains it!

I was in R.Shak the other day and asked about a SPL meter. The girl at the counter had no idea about it so looked up in her computer and could find nothing for it.

I figured it was operator error, or that they had a proprietary name for it or something...
post #4 of 30
This is why they are going away. http://studiosixdigital.com/spl_meter.html Easier for computer applications, and iphone app's, than the old school devices.
post #5 of 30
Thread Starter 
That is actually the same exact app I am looking to purchase. Anyone have experience with it?
post #6 of 30
I have that app on my ipad and the RS SPL. The ipad app is fine for everything but the sub. On my 7.1 system the app and my RS SPL all measured the same except the iPad app was off by almost 20bs for my SVS PC13 sub. I would say use it unless you need to set the trim for the sub.
post #7 of 30
Thread Starter 
Originally Posted by sotwell View Post

I have that app on my ipad and the RS SPL. The ipad app is fine for everything but the sub. On my 7.1 system the app and my RS SPL all measured the same except the iPad app was off by almost 20bs for my SVS PC13 sub. I would say use it unless you need to set the trim for the sub.

Is it possible that the iPad microphone is not as accurate as the iPhone microphone?

I am going to get the app and see if I experience the same issues. Thank you for your feedback.
post #8 of 30
Originally Posted by overwilhelmed View Post

Is it possible that the iPad microphone is not as accurate as the iPhone microphone?

I am going to get the app and see if I experience the same issues. Thank you for your feedback.

No phone mic is going to work properly below around 150hz. It isn't a requirement for voice pickup and after testing a large cross section of phones and apps, not one of them was within 15db of an 80hz tone.

I really wanted to be able to use a smartphone or tablet as an SPL meter, but they aren't accurate enough or reliable enough to be trusted - invest in a dedicated SPL meter.
post #9 of 30
Thread Starter 
Makes sense. Would it be possible to use my calibration microphone that came with my Onkyo receiver in place of the phone microphone?
post #10 of 30
The earlier iPhone actually did better at LF than the newer... The noise filters to make vocals more intelligible knock off highs and (mostly) lows.

Note most inexpensive SPL meters are only good down to 30 Hz (including the RS meter). A better investment may be to spend $100 - $150 for a cheap mic preamp and Behringer or similar mesaurement mic, then use REW or something similar for analysis.
post #11 of 30
Originally Posted by dragonfyr View Post

...They are not to be used for serious gain determinations at isolated frequencies!...

...Who feels the perceived need for "absolute" levels? If so, I am curious as to what this need is founded upon...

You know, generally, I'm not a fan of your posts but this, I'm on your page. It is suppose to be a hobby, for fun so yes, I agree.

I'll start reading your posts again and see if I can learn something else

post #12 of 30
I'm with dragonflyr. The only time I have worried about absolute levels was in various pro and some home installs, and then because it was on a spec sheet so I had to fill in the line. Or we needed to know for various reasons (max SPL to calculate coverage, for instance).

I use a calibrated measurement microphone (Earthworks) for freq measurements.

The biggest danger I have seen in using the cheaper meters is when folk try to set 15 or 20 Hz out of their sub to match a 1 kHz (or whatever) reference tone not realizing the meter may be 10 dB down or more.

I have a RS SPL. Probably used it twice in the past five years, once to see how loud the vacuum cleaner was in and out of my new (then) media room to get an idea of isolation.
post #13 of 30
Thread Starter 
So in reading the responses, I think I may be confused in the purpose of a SPL meter.

I am hoping to measure frequency response at various frequency intervals to determine if an adjustment is needed through room acoustics, EQ settings, and speaker calibration. I used my receiver's Audyssey 2EQ Dynamic EQ function to calibrate my speakers however, I want to confirm the response and visualize the frequency curve.

That said, my current budget does not allow for a large expense into laying out the finances for the measuring equipment and software, however I have an iPhone 4. Given my receiver (Onkyo 667), I would not be able to make the adjustments needed to correct many of the errors (such as EQ settings for the subwoofer).

It should be noted that I am new to the hobby though and I was hoping that experimenting with these tools available on the iPhone would get me comfortable with the measurement equipment, terms, charts, etc.
post #14 of 30
If you just want to play and learn, get the iPhone app and have fun. If later you want to move up, for under $100 you should be able to put together a "real" system with a cheap measurement mic and preamp assuming you have a notebook or PC you can move into the room and can download REW (free analysis software).

I must note a used RS SPL meter can be found on e.g. eBay for under $20. If the iPhone app lets you download the spectral plots to your PC you'll be way ahead, however. Manually taking data andplotting the curves with an SPL meter can be painful.
post #15 of 30
Thread Starter 
Originally Posted by dragonfyr View Post

Also be aware that the iPhone app also suggests and external microphone that will add to the price.

The cheapest (total) SPL meter remains a used RS SPL meter.

Just be aware that it is not going to afford you much utility and the money would be much better spent toward a calibrated Dayton EMM6 mic for $49 and an ART Dual USB Pre (amp) for $49, a few interconnects and the freeware REW.

Thanks for your insight. I was not aware that REW was free. As the saying goes, "Do it once and do it right", I think $20 would be better spent towards the utilities you just mentioned.

Given that my receiver is not conducive to making the adjustments needed to achieve adequate frequency response, I will just live with what I have now and acquire the equipment a later time.
post #16 of 30
Just thought I'd add on to this thread as I just spent some time with the app.

Bought the SPL app from Studio Six Digital ($2.99) to double-check some basic settings on a family member's HT system. As previous users have posted, the microphones in iOS devices vary greatly from one to the next. What I believe Studio Six does well vs some other apps is that their app is calibrated to the specific device (in other words, it "knows" you have an iPhone 4S and calibrates itself accordingly). If you're reading this as an Android device user, beware as Android devices don't have the same hardware standardization so results may be a little less consistent.

I did some side-by-side comparisons with a Radio Shack SPL meter and the results were always within 1db for front, center and surround speakers. The challenge was with the sub -as previous members have posted..

So, although this certainly isn't a replacement for serious HT enthusiasts, it does make it possible for everyday enthusiasts to get a ballpark reading on their HT measurements.
post #17 of 30
Thing is, for REW work, that RS meter is the one most often recommended to calibrate a sub. There are compensation files available for the RS meter that let you get meaningful results (for basic sub EQ via REW) down to 20 hz.

That said, any halfway decent calibrated mic will do better, across a bigger spectrum, unlike the RS meter.

It's a shame the iPhone mics are so filtered at the lower frequencies, else they would probably make a good substitute for the RS meter in other situations.

There are better SPL meters available than the RS meter that are still available, and would do the job, too. One such is available here:
post #18 of 30
Not to stray from thread topic, but seems like there are less choices for iPad. Wondering if anyone have experience with this one: Sound Level Meter Pro (http://itunes.apple.com/app/id553141695?mt=8). The interface looks pretty clean but more importantly it's the only one I found with ITU-R 468 and ISO 226 weightings in addition to A and C.
post #19 of 30
Originally Posted by DJKham View Post

As previous users have posted, the microphones in iOS devices vary greatly from one to the next.
Actually, the mics on iPhones are very consistent, but there are other issues at work. Can't believe nobody's posted this link, so here' goes:

If you read that page you'll see that iOS5 and iOS6 lets them deal with the low end issue and several others making their products on an iPhone quite sufficient for what they are.

For a couple hundred bucks you can get around the mic issue entirely:

But I do agree with the OP, if you're receiver can't effect the corrections you find you need, knowing about the problems will just make you miserable. Don't bother.

REW: nobody mentioned the steep learning curve. Funny.

The OP's receiver has Audyssey 2EQ, which is a start. When he upgrades to a unit with Audyssey XT32 the entire measurement issue becomes pretty much moot. Oh i hear everybody griping about how they try to verify that Audyssey is doing it's thing by using an RTA or REW. The simple answer is, you can't do it that way. Totally different means of collecting data, results are not comparable anyway. A well done Audyssey XT32 cal is mostly good enough. And you don't need an SPL meter at all to do it.
post #20 of 30

ummm... your last paragraph is wholly incorrect, with the possible exception of a well-done xt32 calibration being "good enough" for most...

and yes, you can easily verify the results of any calibration with the appropriate tools....

if you would like to learn why you are incorrect, come join us in the audyssey threads...
post #21 of 30
Yea...um...done it, found the differences in measurement methods, talked to the Audyssey developers as to why they're there, and what tool and technique to use to get agreement.

But thanks for the courteous and kind invitation.
post #22 of 30

choosing to remain uneducated about the topic will not make you correct...
post #23 of 30
Originally Posted by ccotenj View Post

choosing to remain uneducated about the topic will not make you correct...

I have a slightly different technique in obtaining knowledge. If I find a problem or inconsistency, rather than go to a forum and read massive amounts of opinion and anecdote, I go to the engineers who created the item and speak with them, one engineer to another.

But we are both talking generalities here. It would appear you're saying that you can measure the frequency response of a system that has Audyssey applied and verify exactly what it has done using an RTA. Perhaps I'm assuming something you haven't actually said. You can see, using an RTA, that Audyssey has done something, that's true. But you won't be able to measure the response before and after Audyssey with an RTA then dial that difference curve into an equalizer, and expect the same result in every case, in every room. If that were true, the entire fuzzy clustering technique would be unnecessary, and they could have used an FFT based RTA in the first place. In point of fact, a spacial/temporal average taken with an RTA results in reduced resolution masking response excursions, whereas the fuzzy clustering technique does not reduce resolution or mask response excursions. Hence, you'll end up with different curves. You also cannot make a valid comparison between a single point RTA measurement and an 8 point Audyssey calibration, that should be obvious. And making comparisons of the various measurement techniques in a single room or situation will also cloud one's perception. And all of that is only scratching the surface.

I won't bore you with talking about how many rooms I've worked with, but I'm not just an experimenter playing around in his own living room.

You see, I have not chosen to remain uneducated, I have chosen which school to attend.
post #24 of 30

if you would choose to follow my suggestion, you would see how us amateurs have done what i say you can do...

up to you...

edit: fwiw, i am one of the biggest xt32 ho's that exists... i am a FIRM believer in the positive effects it has on sq...
post #25 of 30
Care to point me to a specific post or group of posts? Sorry, I don't have time to dig around a forum this big.
post #26 of 30

the best place to start would be in the "audyssey pro kit thread"... that would be where many of the more advanced audyssey users congregate... also, several of those posters have links in their signatures to documents that have been put together to assist people...

sorry if i'm a bit blunt with my previous posts... redface.gif however, "we" have learned that the phrase "trust but verify" is definitely true when it comes to anything automated (this holds true for video cal for me as well... i use an automated process, but i check it afterwards...)... for example, xt32 (even with the pro kit), makes no attempt to optimize the speaker/subwoofer splice... "we" have found through much experimentation, measuring, comparison of notes, arguing, etc. that the end result can be improved (sometimes significantly)...
post #27 of 30
Thanks for the info. The thread you mention has over 3000 posts in it. If there's a particular section that deals with the issue we're talking about, I'll take a look, but probably won't read all the posts. I'd be specifically interested in how people think they can verify a high precision system like Audyssey with a low precision one like, well, any FFT RTA, and why trust is put in either system as the one under test, or the reference.
post #28 of 30

i led you to the water... it's up to you whether or not you drink... i am not going to drink it for you and regurgitate it in small doses...
post #29 of 30
What you led me to was Niagara Falls for a glass of water. I've spent more than a few minutes with searching the forum, came up with nothing substantive on this subject. I also went to the other Audyssey thread that has over 50,000 posts. Sorry, didn't find it there either. I Googled a bit, found the Ask Audyssey page where Chris Kyriakakis talks about how Audyssey is different from other methods (read that before, of course), which would tend to lean more toward confirmation of what I assert that what you do.

If you're going to suggest that somebody partake of a source of information, that's fine, provided there is actually information there that can be found. You've accused me of being incorrect, yet you've offered no substantive counter arguments. You've accused me of desiring to remain uneducated. I think it's evident that I've done more due diligence than the average guy, both relating to this thread and in previous years of hands-on experience as a certified Audyssey calibrator, and that would not seem to support a desire to remain uneducated. I simply don't have time to wade through literally thousands of posts made by unknown people without credentials giving their opinions. I went to the inventors of the technology and asked them.

You're asking me to ignore the Master Chef and seek out the opinions of perhaps a few individuals mixed into thousands of back-yard weekend barbecue amateurs. You've given no specific links, but instead said "The guy with the answer lives in New York, his last name is Smith, he's in the book."

Post a link, please, and I'll be glad to look it over. Otherwise, let's both do this thread a service and stop this pointless banter. We've hijacked the thread far enough already.
post #30 of 30
Just saw this one on the Ask Audyssey page: https://audyssey.zendesk.com/entries/215529
The response was from Chris Kyriakakis.
Note point #3, re: RTA.

"It's usually tough to match results with different methods because they don't have the IP used by Audyssey. However, reasonable results for verification can be achieved if:

1. You have a calibrated microphone (i.e. a file used by the measurement program)

2. You take multiple measurements (in the same locations used when calibrating with Audyssey)

3. You use an FFT method to find the impulse response of each measured position (RTA only looks at magnitude and ignores time so it doesn't match at all)

4. You average the multiple measurements to come up with a representation of the listening area response."

I guess we weren't the only ones talking about this.
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