Help! first time using an SPL meter! help with an audio calibration!

[smcilwaine287]

I am going to purchase an SPL meter from radio shack tomorrow.
I have a yamaha 663 receiver and am going to try to improve my audio. I am trying to figure out what exactly to do

I know there is a number, I believe DB's that reads out from the meter. What am I looking for that to hit? and should I just put my receiver on test tone, then go to each individual frequency it allows me to adjust.

This is my first time doing this, and I need any help I can get. I can't burn any cd's or dvd's unfortunately, but I do have the test tones on my receiver and I have a few thx rated dvd's w/ audio calibrations built in.

Any help would be great!

[Chris A]

The RS series of hand-held SPL meters will help you understand the relative loudness of your speaker's output, using one of two scales: "A" weighting, and "C" weighting. I use "C" weighting. If you have a test CD or your receiver has test tones, then I would step through the tones, starting at mid-frequencies, then adjust your equalizer or your receiver's tone controls until you are getting about the same SPL level at each frequency where you sit to listen to your system. But the meter itself doesn't do much but help you understand what your ears are already telling you.

The bottom line is: What is it that you wish to have when you've used the measuring equipment?

Good luck,

Chris

[Arkytype]

It would appear your Yamaha has the YPAO feature which will automatically adjust the "frequency response" of your loudspeakers.

If your Yamaha RX-V663 didn't come with a measuring microphone, this one might be worth checking out. It is the model specified for other YPAO receivers. At ten bucks, it's a steal.

http://cgi.ebay.com/YAMAHA-YPAO-Optimizer-Microphone-Setup-RECEIVER-SEALED_W0QQitemZ190309926488QQcmdZViewItemQQimsxZ20090525?IMSfp=TL090525153002r19323

The RS SPL meter suffers from less-than-ideal circuitry and a non-linear capsule.

There are several web sites which have posted the correction curves for the RS unit as well as sites which have instructions for modding the RS unit for flatter response.

Here's a link to one of several threads discussing the YPAO and RS.

http://www.hometheatershack.com/forums/spl-meters-mics-calibration-sound-cards/1652-ypao-mic.html

As for using the RS meter, use the C-weighting scale and set the meter ballistics to Slow. For general system testing, you'll probably prefer 1/3-octave pink noise over discreet tones. Single tone testing can be misleading depending upon your room's "acoustics" and microphone placement. Pink noise is also easier on the ears!

Be sure to take readings at several locations around your listening position. If certain bass frequencies sounds and/or measures low or high, move the SPL meter a few feet laterally away from that spot. If the reading increases/decreases you are probably measuring the high and low sound pressure levels associated with low frequency room modes.

Here's a neat room mode calculator with a 3-D representaion of the peaks and nulls associated with room modes.

http://www.mcsquared.com/modecalc.htm

One last suggestion--don't try to boost the EQ to "fill a hole" in the response. If you are sitting in a room mode null, (you'll probably run out of amplifier power trying to fill a 30 dB "notch" at 50 Hz) try a different speaker/listening position setup or (better yet) use some diagphragmatic bass treatment to smooth out the overall bass octaves.

Lee

[artto]

You are not going to calibrate much of anything with the
Radio Shack sound pressure meter!!!

First of all, the device is ONLY $50. A high quality
calibrated microphone (which the RS spl meter has not) can set you back a few
grand, or at least a few hundred, and that’s just for the microphone.

Second. A SPL meter, especially an inexpensive model like
the RS is basically only good for measuring the general sound pressure level ~
a “ballpark” figure at best.

Third, you really need at least some kind of test CD or
other tone/noise generator.

Fourth, no, the “test” tone on tuners and receivers is
usually a 1000Hz sine wave ~ not suitable for calibrating your system’s frequency
response or tuning room acoustics.

You are not trying to “hit” any specific number of decibels
on the meter. What you want to do is try and make sure the sound pressure level
is the same (as uniform as possible) throughout the room, particularly in the
primary listening area.

You will need a broadband noise source that produces white
and pink noise across the whole audible spectrum as well as "bands" or a grouped range of frequencies (20Hz to 20KHz and 20Hz to 100Hz, 100Hz to 500hz etc.). I use the PreSonus Test CD.

And after you complete you measurements, what are going to
do with it? Do you have a 1/3 octave parametric equalizer? Are you going to
apply acoustical treatments to the room? Or are you simply going to be moving
your speakers around. For the later use your ears ~ you don’t need any meters.

Just a bit of advice ~ but from the way you formulated your
questions ~ I think you’re in way over your head as far as making any
improvements by taking some SPL measurements with the Radio Shack meter. It’s
not that accurate, +-2dB at best. The biggest problem is that it’s not “calibrated”
so you don’t know where the +2dB or -2dB falls along the frequency response
curve. Your ears can hear better than that.

The Radio Shack meter is really only good for "how loud is the sound"? in a very general sense.

[pauln]

There is nothing wrong with the RS meter. Most amateurs just turn it on and look at the readings. Here is how to make it work better:

Attach acoustically damping feet to the right side of the meter and set it on a marble slab oriented so that the RS meter is laying in its right side; lay a brick on top of it (use an ACME brick set on edge so you can still move the dial), then cover the sound entry opening with a Dr. Pepper bottle cap and allow the meter to warm up for 30 minutes after turning it on before taking any readings (take off the cap for the reading...)

Since the meter itself will be rotated 90 degress you will need to cock your head to the right, but since the right brain is the part that handles numerical concepts, the increased blood flow to that half will only improve the accuracy of the readings.

[peshewah]

Sorry smcilwaine287. I guess I should have never suggested a SPL meter. I won't do that again.

[Kriton]

Dude - the RS meter is very helpful for calibrating (however primatively) the surround sound blance of a 5.1 or 7.1 system - you put the meter at the primary listening position (where your head is going to be when you watch movies or listen to music in surround). Set it on something at the height of your head (don't hold it as your body may skew the results but if that is all you can do, it will work).

Now turn everything on, run your front speakers test noise on your receiver. make sure the gain for each of the speakers is zeroed out - and let the test tone rip - usually it is quite loud. Turn the meter on; if the noise is so loud it pegs the meter, turn the dial up to the next level of DB's (it will usually be around the 70 or 80 level) - now once you do that, the meter should be bouncing around between the high (say 90 db) and the low (say 80 db) - go back and forth from right to left, and make sure that the noise coming out of both the right and left channel is hitting the same db mark, adjust gain (+/-db) to make this happen - then go around the surround speakers with the same noise, and do the exact same thing to THE exact number that you used for the fronts - rock back and forth between them to make sure they are ALL the same DB on that test noise, even and especially, the center. I personally like dialogue so I hop up my center at least 2 db higher than the fronts, but that is just my preference.

NOW, put on a DVD and listen to how nicely this will create the illusion of surround sound - the pod racing scene from Star Wars the first crappie movie comes to mind...in my system, it made a huge difference - you may need to do it for every disk as they are very differently engineered, but you will be shocked at how much use you will get out of one after a while -

I am sure that you can use it for more, but that is what I have one around for. YMMV.

B

[Coytee]

It would appear your Yamaha has the YPAO feature which will automatically adjust the "frequency response" of your loudspeakers.

I'm not familar with the YPAO feature so my comment might be terribly off the wall.

I DO have an equalizer that I've had in/out of my system before (dbx 14/10). One of its features is to autocalibrate the sound of your room to flat. I don't know if it does or doesn't do it but by the time it's done with the process, it has taken the upper frequencies and simply increased them up off the scale. I mean to say, instead of bumping a HF 3 db's or perhaps, lowering everything else 3 db's relative to that HF signal, it has 100% maximized the upper sliders to where they are 100% maxed out.

Is it working properly? (it appears to be in general use) Does my room suck THAT much? (I didn't think so)

I finally yanked it out.

Just a comment to be aware of an automatic feature.

[USNRET]

I tried my Denon onboard setup and found it lacking for each channel gain setting. So I use the RS meter as Kriton said above but my technique is different.

1. Place meter at ear level with mic pointed up and scale set to be able to read 85 dB (set either 80 or 90), slow, C weighted.

2. Enter manual mode setup and select first speaker (typically front left), adjust receiver volume until you interpolate 85 dB (if scale set to 90 read -5dB on scale). Oh, make sure LF is set at "O" on your AVR setup. AVR volume control is not touched again from this point. Each speaker is adjusted to match the "MASTER", LF in this case.

3.Using AVR remote move on to next speaker (center) and adjust that speaker to mimic the LF using the menu adjustment.

4. Continue thru the speakers matching them up. Be careful at the sub, first time thru you might want to make sure the sub gain at the sub is set low and then bring up the gain at sub.

5. Exit, save or what have you on your AVR.

If curious what you might change you will make take notes on where the speaker level settings are after using the YPAO and then again after manual setup. Mine was as much as 5 dB off and using the RS meter was much better to me.

Is the RS 'calibrated'?. Heck no but then I have a $500 SPL meter and the difference with what we are doing here is not that great and the RS meter is easier for a quick check.

Good luck.

[jdm56]

...and don't forget to figure in the "corrections" for the RatShack meter's known low frequency deviations:

125Hz --- +0.5dB

100Hz --- +2.0dB

80Hz --- +1.5dB

63Hz --- +1.5dB

50Hz --- +1.5dB

40Hz --- +2.5dB

31.5Hz -- +3.0dB

25Hz --- +5.0dB

20Hz --- +7.5dB

[USNRET]

and don't forget to figure in the "corrections" for the RatShack meter's known low frequency deviations:

There are some minor differences between model. I use an older analog one. Who is that has a lot of info...Home Theater Shack forum, maybe?

[jdm56]

Mine is the older analog dial model. I believe the corrections were for that model in particular. I don't know if the same figures would be accurate for the newer digital digital read-out version or not. I've never seen another set of figures though, so maybe one size fits all -possible, but I doubt it.