88 dB Ambient?????

[Yesfan70]

Try wrapping the meter in aluminum foil and grounding the foil with a spare speaker cable.

When Flint starts telling you to raise your left leg a bit higher, please shoot/post video. :happy-smileygiantred:

I'm being brought back 5 decades, when we attached tinfoil to our rabbit ears and jiggled the channel knob...

I can see where this is going.

[youtube]http://www.youtube.com/watch?v=rryQfAnQs3M[/youtube]





Hey Heeman....try it now.

 

[DIYer]

^

 

[Rope]

Rope

 

[DIYer]

^ Those glasses look familiar. :confusion-scratchheadyellow:

 

[Orbison]

Yikes!! :happy-smileygiantred: :eusa-clap:

 

[yromj]

Oh man, when the foil discussion broke out, I was sooo reminded of Allen from the old forum. He would have appreciated that part of this thread.

John

 

[Flint]

Hey, when someone blames RF or EM interference for an issue, it has to be ruled out. The easiest and cheapest and easiest way to rule it out is with aluminum foil and a grounding wire.

 

[Botch]

^ Kitteh does not look amused... :mrgreen:

 

[heeman]

I purchased a new SPL Meter.

Galaxy; Checkmate CM 130.

This meter does not pic up an ambient noise. Chairs can be plugged in, light on and it works great.

After the purchase I noticed that it is only rated down to 125 Hz. The CM 140 (more than double the price) is rated down to 31.5 Hz.

The $10,000 question is...........................................................

Do I return the CM 130 and up grade to the CM 140? :angry-tappingfoot: :angry-tappingfoot:

 

[Flint]

If you want to use it to calibrate your sub? YES!

 

[heeman]

Yup, that's what I thought......

 

[yromj]

This also seems to indicate that the other SPL meter may be picking up a low frequency rumble.

John

 

[heeman]

The CM 130 is going back.

I just ordered this one from Musicians Friend; $99.99 Columbus Day discount of 10%. Good down to 31.5 Hz.

The little tripod is an accessory, I did not order that.

Nady DSM-1

 

[heeman]

I received the DSM-1 and the unit's build, looks and feels much better than the Galaxy/Checkmate brand.

Even though the DSM-1 is rated down to 31.5 Hz, it still does not pick up the erroneous 88 dB noise that the analog Radio Shack meter does. So I will conclude that the Radio Shack meter has some kind of issue and will find it self in the garbage.

I calibrated the system with the DSM-1 and found that the sub was WAY hot. I will contact Nady today to see if there is a low frequency compensation like other lower cost SPL Meters.

For $89 this is a winner.

:music-rockout: :music-rockout:

 

[Flint]

The meter probably measures with an A Weighted filter.

 

[heeman]

Both meters have "A" and "C" weighting. No noise was picked up with the new meter on either selection.

The Radio Shack meter picked up the noise on both.

 

[heeman]

Nady Tech Support indicates that there is no compensation curve for this SPL Meter.

 

[Flint]

In that case...

Use the A-Weighting or C-Weighting curves for correction (depending on the setting you have the meter on).

With the C-Weighting setting, if you are measuring the subwoofer with a crossover around 50Hz, add 1dB to 5dB to the measurement (meaning you need to turn down the sub by 1dB SPL to 5dB SPL).

 

[Flint]

Here's a lower resolution chart with only the A-Weighting and C-Weighting curves

 

[heeman]

So you are saying that these curves are standards for measurements across the frequency ranges?

Is this due to the inherent characteristics of the microphones response curve?

If other, can you please explain?