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SPL Meter: First Use, Couple Questions

post #1 of 16
Thread Starter 
Received my Radio Shack digital SPL meter last night, have a couple questions regarding its first use, but I'm having a difficult time finding consistent answers as there seems to be a lot of contradicting advice out there. My goal here is simply to balance the output levels of each speaker so they all produce 75db from my listening position.

I understand that it's not advised to point the meter at each individual speaker, as moving the meter each time can create variances in the readings. So with the meter pointed in the direction of my display, I can position it either: (A) horizontally (B) at a 45° angle or (C) vertically. I understand each position will produce different results, and some may prefer one result over the other. But just as a starting point, which would be considered the most commonly used position?

Also, I purchased a microphone stand with a boom arm to hold the meter in the correct location. Should I be concerned about the position of the microphone stand (i.e. placing it behind, off to the side, or in front of the listening position)? Obviously I will remove myself from the room, and monitor the meter via my laptop running REW with the correct calibration file. Easiest location in this case would be beside the listening position with the boom arm extending over the armrest of the couch.

Any thoughts or advice? Greatly appreciated.
post #2 of 16
You want to measure at ear height, with the SPL mic facing up, from the main listening position.
post #3 of 16
Quote:
Originally Posted by Doogals View Post

My goal here is simply to balance the output levels of each speaker so they all produce 75db from my listening position.

Per p.15 of the RS SPL meter manual: Point the meter at the source.
You don't have to leave the room for simple gain measurements. Just don't stand where you will reflect energy into the capsule.

That is sufficient to ascertain the relative levels of each speaker relative to one another.
post #4 of 16
Just aim the meter at each speaker as you test that speaker, from ear height at the listening position.

Are you using constant test tones of varying frequencies?



Quote:
Originally Posted by Doogals View Post

Received my Radio Shack digital SPL meter last night, have a couple questions regarding its first use, but I'm having a difficult time finding consistent answers as there seems to be a lot of contradicting advice out there. My goal here is simply to balance the output levels of each speaker so they all produce 75db from my listening position.

I understand that it's not advised to point the meter at each individual speaker, as moving the meter each time can create variances in the readings. So with the meter pointed in the direction of my display, I can position it either: (A) horizontally (B) at a 45° angle or (C) vertically. I understand each position will produce different results, and some may prefer one result over the other. But just as a starting point, which would be considered the most commonly used position?

Also, I purchased a microphone stand with a boom arm to hold the meter in the correct location. Should I be concerned about the position of the microphone stand (i.e. placing it behind, off to the side, or in front of the listening position)? Obviously I will remove myself from the room, and monitor the meter via my laptop running REW with the correct calibration file. Easiest location in this case would be beside the listening position with the boom arm extending over the armrest of the couch.

Any thoughts or advice? Greatly appreciated.
post #5 of 16
Quote:
Originally Posted by commsysman View Post

Just aim the meter at each speaker as you test that speaker, from ear height at the listening position.

Are you using constant test tones of varying frequencies?

Shouldn't you point the spl meter upwards slightly angled
post #6 of 16
No
But the capsule should technically remain at the same point for all measurements - rotate the body about a vertical axis extending through the capsule...as if such precision is really necessary for an SPL meter...
post #7 of 16

Hee hee - poor guy comes here because he’s seen conflicting information elsewhere, and what does he get?

Honestly Doogals, measurement procedures to achieve laboratory-grade precision are not needed here. The main thing is consistent orientation of the mic, be it direct-aimed or vertical.

The only good reason to point the mic directly at each speaker is if you really, really require an absolute 75 dB. Otherwise, vertical orientation is fine for speaker level-adjustment settings. The discrepancy between vertical orientation or pointing directly at the speaker will only come into play with the main speakers, not a subwoofer (since low freq output is omnidirectional).

And by the way, the meter has a threaded insert that will work with a common camera tripod. Your mic stand will only work with the meter if you have an adapter of some kind, or use a lot of duct tape.

Here’s what I suggest as a “best of both worlds” between pointing the meter directly at the speakers and a more-convenient, "set-it-and-leave-it” vertical orientation.

Situated at the listening position, point the meter directly at one of the speakers, and make the volume adjustment to get a 75 dB reading. Then, put the meter on the tripod at the listening position with straight-up 90° orientation, and afterwards take another SPL reading of that speaker. The new reading might be a dB or two lower than the direct-orientation reading – say for example, 73 dB. So, with the mic in the straight-up orientation, now calibrate the rest of the speakers to 73 dB. This will get you the functional equivalent of pointing the meter directly at each mic individually.

Make sense? Hope this helps.

Regards,
Wayne A. Pflughaupt


post #8 of 16
Quote:
Originally Posted by Wayne A. Pflughaupt View Post

Hee hee - poor guy comes here because he’s seen conflicting information elsewhere, and what does he get?


Yeah, heaven forbid we should quote from, and link to the RS SPL meter owner's manual that the meter is designed to be pointed AT the source; and the threading is on the bottom of the meter allowing it to be positioned horizontally atop a mic stand pointed at the source.

Confusing indeed.
post #9 of 16
Quote:
Originally Posted by Doogals View Post

Received my Radio Shack digital SPL meter last night, have a couple questions regarding its first use, but I'm having a difficult time finding consistent answers as there seems to be a lot of contradicting advice out there. My goal here is simply to balance the output levels of each speaker so they all produce 75db from my listening position.

I understand that it's not advised to point the meter at each individual speaker, as moving the meter each time can create variances in the readings. So with the meter pointed in the direction of my display, I can position it either: (A) horizontally (B) at a 45° angle or (C) vertically. I understand each position will produce different results, and some may prefer one result over the other. But just as a starting point, which would be considered the most commonly used position?

Also, I purchased a microphone stand with a boom arm to hold the meter in the correct location. Should I be concerned about the position of the microphone stand (i.e. placing it behind, off to the side, or in front of the listening position)?

Mic at the listening position. Mic pointed up is recommended by some to ensure that the mic is essentially omnidirectional in the horizontal plane, and not being blocked by the case of the meter on the back.

Quote:


Obviously I will remove myself from the room,

Usually Not necessary.

Quote:


and monitor the meter via my laptop running REW with the correct calibration file.

Usually Not necessary.

Quote:


Easiest location in this case would be beside the listening position with the boom arm extending over the armrest of the couch.

Any thoughts or advice? Greatly appreciated.

If all you want to do is match levels among full range speakers, what you want is a recording that routes a band of pink noise in the approximate 500-2000 Hz range to each channel in rotation. That will give you a steady reading.

I just did another post to a fellow who wanted to check out the crossover to his subwoofer (I think) and the advice I posted there is applicable to subwoofer balancing.

Usually, surround systems aren't properly balanced for equal sound everywhere. But if you start out with all speakers at the same lvel, you can add or subtract the same number of dB from speakers of the same kind (e.g., mains, rear surrounds) to get the desired results.
post #10 of 16
Quote:
Originally Posted by Doogals View Post

My goal here is simply to balance the output levels of each speaker so they all produce 75db from my listening position.

I'll try not to give an inconsistent answer.

First, this might help:

All About SPL Meters

In that article you'll read that the best way to balance speakers is with the meter pointed upward to not favor any one speaker. Just rotating the meter as it points toward each speaker one by one will change the response more than you want. But more important than that is using the correct test signal. The best signal is band-limited pink noise. Sine wave test tones are not useful, and using a single tone almost guarantees a mismatch of at least 5 dB or more. The DVD Essentials product mentioned in that article uses band-limited pink noise. I also created a file of such noise for my upcoming book. I can't post that publicly, but I'm glad to send it to anyone who emails me from the home page of my web site www.ethanwiner.com.

--Ethan
post #11 of 16
Quote:
Originally Posted by Ethan Winer View Post

Sine wave test tones are not useful, and using a single tone almost guarantees a mismatch of at least 5 dB or more. The DVD Essentials product mentioned in that article uses band-limited pink noise. I also created a file of such noise for my upcoming book. I can't post that publicly, but I'm glad to send it to anyone who emails me from the home page of my web site www.ethanwiner.com.

--Ethan

I'd like to get that as an e-mail d/l.

You've somehow managed to make it incredibly complex!!

Please please provide something simpler! Thank you!
post #12 of 16
Quote:
Originally Posted by arnyk View Post

Mic at the listening position. Mic pointed up is recommended by some to ensure that the mic is essentially omnidirectional in the horizontal plane,

mic direction is dictated by manufacturer / whether free-field or diffuse-field design.

dragonfyr's post above is accurate.
post #13 of 16
Quote:
Originally Posted by OtherSongs View Post

I'd like to get that as an e-mail d/l.

Email me from my web site.

Quote:


You've somehow managed to make it incredibly complex!!

It's very simple to balance levels. Though to use my file you need a way to send the noise to each speaker one at a time. If you have no way to do that, buy the DVD Essentials DVD which does that for you. The whole thing takes 5-10 minutes, once you find where in your receiver you can balance the volumes.

--Ethan
post #14 of 16
Dolby labs recommends specifically for the RS meter Meter held at the seating position arms length from body pointed at the center channel 45 degree tilt. The meter should be C weight and slow setting.

This position is to be used for the Fronts and Center channel.

From here you turn the meter 90 degrees to the left and right to do the surround channels still at 45 degrees. tilt.

I have tried just about every recommended way posted and this way by far has produced the best results for my money.
post #15 of 16
I sure hope you guys manage to figure out what is an incredibly simple procedure.

The fact is, if you drive each speaker individually an you only care about the RELATIVE LEVELS of each, you can wear a Spideman, Batman costume, or stand naked, on roller skates or a branded or non branded Tony Hawk skateboard, and/or point the mic at any @%#^$ angle you like, as long as it is done consistently for each source.

Would someone please explain how the tilt of the mic capsule is going to make a difference to the relative levels despite any appreciable effects occurring in a bandpass the meter in not even capable of measuring!? I don't care if they are all .000000000001 dB from absolute or 957362547.35621874 dB from absolute so long as a consistent procedure is followed allowing one to obtain valid RELATIVE levels.

No wonder marketing guides take precedence over any acoustics text here.

Now, if folks would only take a fraction of the time they use to worry about this absurd minutia to study more important acoustical concepts, one can only imagine what stimulating conversations we could aspire too. And maybe someone would FINALLY resolve what difference various speaker cables make.

And, can anyone think of a more limited piece of gear to be obsessing over - considering that so many seem to ascribe almost magical powers and capabilities to such a fundamentally limited device - aside from speaker cables?

And after solving that, maybe someone can aspire to resolve the age old dilemma over which end of a potato you properly start peeling first...
post #16 of 16
Quote:
Originally Posted by dragonfyr View Post


And after solving that, maybe someone can aspire to resolve the age old dilemma over which end of a potato you properly start peeling first...


I can answer that, but since the answer is so simple I shan't bore you with it.
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