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Discussion in 'Archived Threads 2001-2004' started by Alan Preston, Nov 9, 2002.
Is this true? If I get AVIA will I need to get an SPL meter from Radio Shack?
I seem to recall seeing some comments here a while ago stating that analog SPL meters were better than digital SPL meters for this specific purpose. Is this true, and if so, why? I would have thought a digital SPL meter would be better. Digital readouts are good for precisely indicating a steady-state value. Analog gauges are not as good at indicating the precise value but are much, much better at demonstrating the rate of change. It seems to me that for this specific purpose, rate of change is irrelevant as the test tones should be steady-state (although I have never performed a calibration so I may be wrong about that).
All I can say is I have the digital one and it works fine. One must remember to place ones meter in the slow response mode but the same is true of the analogue meter as well.
So I will need to get an SPL meter along with AVIA? I just want to be sure before I blow up my brand new system.
When u get Avia, u will see it has a chapter on how to actually use an SPL. All ur question would be answered here. While the SPL would be used for ausio calibrations, the Avia disc will be used for video and ausio calibrations. Don't worry about the "cost-effectiveness" of the above purchase. U will see that ur system will need to be re-adjusted once every month or so.
My HK AVR 520 has a simaler built in SPL set up ability.But seeing how I had just bought a SPL meter for the Onkya I owned for a week or so,I got stubborn and stayed with the reading if the seperate,and it also seemed more accuate.
You are completely wrong about that. Especially on sub tones, the variation is large. The digital meter is acceptible, but I find the analog for more intuitive.
Then I must completely misunderstand the point of calibration. I thought it was to get equal volume levels from all speakers. I thought this was accomplished by sending the same tone to all speakers, one by one, using the SPL meter to measure the volume from each speaker, and using the receiver to adjust the volume level for each speaker appropriately, until all were at the same level. How are you supposed to match the volume level of one channel to another when the test tone is a moving target?
>>>Then I must completely misunderstand the point of calibration. I thought it was to get equal volume levels from all speakers. I thought this was accomplished by sending the same tone to all speakers, one by one, using the SPL meter to measure the volume from each speaker, and using the receiver to adjust the volume level for each speaker appropriately, until all were at the same level. How are you supposed to match the volume level of one channel to another when the test tone is a moving target?
The needle on the meter will bounce around about 1-2db on average, sometimes more on bass tones and the reflectivity of your room. Heck, if you put in on Fast response, you'll see it dance like a riverdancer-- this is simply the nature of sound. Even a dead even SPL produced from your speakers will often be measured with slight variations due to interaction of sound waves and reflective sound hitting the meter. The source signal is steady- however the reproduction is never perfect, unless you have an anechoic chamber in your house...
But it's not as bad as it seems. You'll see once you get a meter- slow response and a analog meter to look at- you'll get a clear picture of what's happening.
One can easily match volume, because the meter will quiver pretty much identically for each tone from speaker to speaker. Whether you choose to calibrate using the peak point of the measurement, or the avg level of the measurement- as long as you chose the same method for each speaker, you're going to get a properly calibrated output.
So- what you posted above as your expectation is "true", but it isn't as dead precise and as right/wrong as you might be expecting it to be.
Bruce, what I meant by "moving target" was the changing volume of the tone, what you referred to as "the digital signal is fluctuating". This is what didn't make sense to me; if the point of the tone is for you to use it to match volume levels of all speakers, it shouldn't be fluctuating, it should be steady. Now Vince explains why it might be fluctuating (thanks, Vince), and he makes it seem that it's not the source signal but just normal effects of room and stuff like that.
If I can actually find my SPL meter, it's a fairly moot point. I bought an analog SPL meter from Radio Shack around ten years ago. I was mainly concerned about what to buy in case I couldn't find it. Are the current analog SPL meters the same as they were ten years ago, do you know?
I don't imagine you'll have much problem finding one... they have them in nearly every radio shack store on the planet, and you can call 1-800-The-Shack and ask for Catalog number 33-2050. They'll happily send you one in the mail for the tidy sum of $35 + S&H (if you want the digital one, call and ask for 33-2055 and pay $50). YOu can also order one on the website right here.
However the older one would work just fine. I have a buddy who bought an analog RS meter in 1994 and it's exactly the same as the one I bought last year.