Axiom Home Page Forums General Discussion Stereo Audio Only System Renewal

I'm not sure what you mean by a "more precise instrument", JB. I don't think that measuring SPL in db is particularly esoteric technology anymore.

Tom, if you have an iPhone or an Android device, you might be able to find a (free) app that does basically the same thing. I mean, we're not trying to launch the space shuttle here, or anything.

I'm not familiar with the Scosche. Mine is an old RS analog type. I suspect the chip in all those devices is probably the same. Looks like our Canadian brothers tend to have to pay more for this (among other things) than we do south of the border.

if you measure the output of 1 speaker and the meter says it's 75 dBSPL, and you check a second speaker and the meter reads 73 dBSPL, then when you increase the gain for the second speaker to the same reading as the first one, then they both will truly output the same SPL. This is what a low cost meter can do well: repeatability.

this does not mean that the reading on the meter is "really" 75 dBSPL though, but it can vary from one meter to another, and also the readings can vary according to the frequency that's measured.
This is called manufacturing tolerances.

most of the time, the auto calibration on an AVR is more precise than what a low cost meter can show.
the low cost meter will be able to bring all speakers to the same level, but will not necessarily show a true/exact meter reading: it will not tell you whether your SPL is, for example, 74 or 75 dBSPL, and there are additional errors when one changes frequencies, as those meters don't have a flat frequency response, so a sound measuring 75 dBSPL at 1 kHz will not give the same reading at other frequencies, specially for big chunks at the ends of the spectrum.

if you were to check a signal - with a low cost meter - of a specific strength at 1 kHz and then at 32 Hz, your meter would show very different readings; with a precision meter, the difference between the two would be minimal, as the tolerances are much tighter.

in short, with a low cost meter, all speakers can be adjusted to the same SPL, but you don't know what the true SPL reading is;
with a precision meter, an added benefit is that the display will give you a more precise, truer SPL reading, and this, over a much larger chunk of frequencies.

a few words more...
if you just want to have a good - but not necessarily precise - spl reading, the R.S. meter will be ok.

Tom, precision is pretty much a function of cost. When i was in the Navy we had some SPL meters that were a couple thousand dollars each, and had to be calibrated every quarter... As J.B. said, with those meters 75DB, was EXACTLY 75db, measured to the 1000'th..


However, the precision of an AVR is a function of the quality of the mic being used... even the audyssey pro kit only costs 500$. So, how accurate can that mic be? Also for HT stuff how accurate does the mic need to be? I mean, any of the mic's used are most likely WAY more sensitive than the average ear... So, i would propose that a Radio Shack meter would be more than sufficient..

Thanks for all of the info on SPL meters. The Source's model up here seems to be completely different from previous RS models that most people use. Reviews on it are scarce.

I don't have a fancy smart phone & plan never to get one. I rarely follow the herd - perhaps that's why I like Axioms & ride a Yamaha TMAX, ha!. Being long retired, I hate the interruption of mostly needless phone calls - but that's just me.

The levels that an AVR sets up do not apply with this system as it is driven only by a minimalist tube amp - only one volume control.

What I would like to do is just measure the overall average Db level that I consider to be at a 'moderate' level at my primary listening area so that I can pass on the results here.

I should try to borrow one I guess as it seems to me to be something that I really don't need to buy for just this purpose...

TAM

exlabdriver,

If you know anyone with an Iphone, there is a free SLP meter app. The iphone has a calibrated mic, so it should be as accurate as any sub 100% spl meter... They could always install the app get the reading for you and then delete it if they wanted.

That's a good idea, Alex.

Thanks for the clarification JB and Alex. I appreciate the opportunity to learn from folks here.

dak:

Thanks for the iphone App idea. My daughter in Victoria has one & will be coming up to visit in a couple weeks. I'll get her to download the app & try it out.

I'll put on my new Spiro Gyra SACD at my tube amp's 10 o'clock volume (moderate for me) & 11 o'clock (getting too loud) to see what Dbs my system is putting out at my couch.

We then should be able to nail down roughly whether the EP-400 should be able deliver like my F1000 does. The EP-400 being well over 5Xs more powerful than the F1000, I expect that it should have no trouble equaling or exceeding it.

Super idea, thanks again...

TAM

Has anyone ever tried this?:

http://www.ehow.com/how_12027736_turn-laptop-spl-measuring-tool.html

I thought that I might try the 'ETF Acoustic' demo software on our Toshiba Laptop. I guess that the main factor would be the accuracy of the built-in mic...

TAM

I brought the subject of SPL Meters up at our garage band session tonight. Seems that one of the guys was contemplating buying one until I pointed him to the 'SPL Meter' app for his IPad for $0.99.

He's going to try it out & lend it to me if it works OK.

TAM