Axiom Home Page Forums General Discussion Technical Questions SPL Meter

I am still trying to grasp this SPL thing, I wanted to try and setup the EP500 today and was reading about it on http://forum.blu-ray.com/showthread.php?t=38765 and it stated, Set the db range on the meter to “75" or “80".

How do I do that? I don't see an option on my SPL to set a range.

This is the SPL meter I am using https://www.instrumentchoice.com.au/store/index.php?_a=viewProd&productId=64

Any advice would be very welcome

I would imagine that instruction applies only to analog SPL meters, not digital.

Graeme, surely the meter came with a booklet of instructions? Just from the brief info shown on the site it would appear that there are only two ranges, 30-100dB and 60-130dB, but there would have to be a switch to choose between the two. The comment that you quote from the Blu-ray forum apparently refers to a RadioShack meter or similar which has a relatively narrow range of +/- 10dB around the set number, which is on a round dial marked in 10dB increments from 60-120dB(allowing measurements from about 50 to 130db by varying the range setting). If your meter can in fact measure from 30 to 100dB in one range without having to change some setting, then of course that's even better than having to make a setting that's within 10dB of the sound level to be measured.

75 to 80 dB is your target SPL; you generate a test tone from each speaker and adjust the level so that the SPL readout is 75-80 dB at the primary seating position. For an analog meter, "setting" at 75 means that when the needle is showing 0 dB, the SPL is 75. Typically, the SPL meter has higher accuracy right around the 0 point and decreasing accuracy as the needle moves farther into either side of 0. I don't think it matters for digital meters. Don't forget to set your meter to "C" weighting and "Slow" response. Also, most hand-held meters are not perfectly linear, especially for low frequencies (as are produced by your EP500), and will need to be corrected; so, be sure to look up correction factors established for your particular meter for various frequencies. If you have any other questions, just shoot away. We are here to help.

You sound as if everyone should know these things? I have absolutely no clue what so ever with this, I have never used one in my life and have never even seen a Radio Shack SPL let alone used one.
It's a little hard when you don't understand what you are reading. It may as well be in Japanese.

I'm trying to learn, but maybe I should be a lot more knowledgeable before I ask a question.

Thank you for the info.

You're fine Graeme, keep the questions coming.

If we feel like you're getting too smart on any one topic, we'll start responding in Japanese to keep it challenging.

Otherwise, fire away.

Jason

I finally figured it out. Johnk is audiobot!

an grammerbot, and spellingbot, and attorneybot, and clasicalbot, etc...

I apologize if my post sounds patronizing. It is in no way meant to be. Just trying to help...

A decibel (db) is a measure of sound. An SPL meter tells you how many decibels it's picking up. Turn it on and talk, it should respond. See here for examples of how loud certain things are.

So with that in mind, the point of calibrating a system is so that all of your speakers produce the same volume. The 'set your SPL meter to 70-80db' is specific only to those of us with the old-style radio shack meters that are so popular. They look like this:

See the dial? That sets the range that the needle would register. It's set to "120". If the needle is pointing to "0" then you're hearing 120db (loud!). If it's -2, you're hearing 118db. +4 = 124db. But again, none of that really matters to you because you've got a nice digital one.

Imagine a thermometer. In your mind, you can see that it measures from -20º to perhaps 45º C. Now imagine a thermometer with a little window that only shows you 10º at a time. It'd be up to you to move the little window to the proper range to get the reading. If it's about 25º outside, you'd move the window to view 20º - 30º. The instructions you're reading are for an SPL meter that requires a 'window'.

But with your digital one, you've still got a 'window', it's just bigger. As JohnK says, it looks like 30-100dB and 60-130dB. It actually doesn't matter which you use because either range will give you readings in the 70-90db range that is usually used to calibrate speakers.

What you're trying to do with the SPL meter is to get all of your speaker outputs calibrated to play at the same volume given the same input signal. If they're out-of-balance, surround sound effects aren't nearly as convincing and your system just won't sound as good as it can. If your right rear speaker is closer to your seating position than the left rear, you're going to want to decrease the output from the RR and/or increase it to the LR so that they sound the same. By using an SPL meter, you can precisely dial-in the amount of +/- that you need. It's no different with the subwoofer, except that there are more variables involved with sub loudness because your sub has it's own amp & level adjustments. In other words, a sub's output can be quite 'wrong' compared to the rest of your system.

If all of your other speakers are pumping out 80db worth of test tone at X% volume, then you're going to want your sub pumping out 80db too*. The SPL meter just gives you a highly accurate way of making these adjustments.

Good luck! I'm sure there will be many others along to offer their assistance. We're all happy to help.

*Some folks (myself included) like to run their sub a little 'hot'. Mine is set about 3-4db louder than the rest of my speakers. I just like it that way.