Is my RS Digital SPL Meter Damaged?

**thewire** · **09-07-08, 08:15 PM**

When I measure my subs in my HT I get a dip at 60Hz. When I measure my sub in my bedroom I also get a dip at 60Hz. When I measure my Polk Towers in my bedroom I get a dip at 60Hz and also when measuring a single boombox speaker I think cost around $40.00 for the entire radio. Is it possible my RS Digital mic was damaged somehow when I had dropped it before? Is it because the battery insert is missing? Is 60Hz just a reacurring problem I have? Some other kind of problem?

The tiny boombox speaker got a 30dB offset. The crossover was 120Hz on each measured as a subwoofer, except I limited the Polk Rti70 and boombox speaker to 20Hz. I did not change the levels.

**Wayne A. Pflughaupt** · **09-07-08, 08:21 PM**

The green and blue traces look like they were measured in the same room.

Regards,
Wayne

**thewire** · **09-07-08, 08:34 PM**

Those are all measured in my bedroom with the speakers 3 feet behind me about 45 degrees with the mic next to my ear.

This one is from the HT room. I just didn't expect them to look so similar right off.

**JohnM** · **09-08-08, 08:24 AM**

To check the meter make a near field measurement right in front of the speaker/sub.

**thewire** · **09-08-08, 10:06 AM**

When I do that in my bedroom I noticed a dip with both the sub and the Polk at around 40Hz. The odd thing is that I had done nearfield measurements with my meter before in the HT and they had never showed any large dips. More recently I did a nearfield of one of my subs in the HT and it showed a large null at near 60Hz. I thought nothing of it and thought it may have been to close to the wall for measurement at the time. I'm using a different amp here than I use in the HT which shows a somewhat smooth response from 10Hz that slowly rises when I did a loopback of the highpass output. Here is a nearfield of my Polk tower at nearfield. I am using a headphone out into RCA splitters so that I can listen to headphones right now with the sub in my bedroom so it is not a standard REW connection. I was not looking at something very critical so thought it might not make a large difference. The wire I am using is also very small on the Polk. It looks like an 18 AWG or less and there are like 3 strands, but the distance is short. Only the bass drivers are hooked up. The amp does not have a serial number or model number on it but I could look up the name from where I bought it. It is a 200W plate amp rated for 4ohm.

Here is the nearfield and another measurement at my ear. Red = at my ear, purple = mic on the tv, the lower blue measurement is with the mic on the first step outside my door leading down the steps with the door open.

**thewire** · **09-08-08, 01:47 PM**

Does anyone have a similar problem? Was the nearfield measurement well enough to prove if my RS meter is capable or not?

**JohnM** · **09-08-08, 02:26 PM**

Meter output looks OK.

**thewire** · **09-08-08, 02:31 PM**

That is good news. I thought I would have to buy a new meter.

**thewire** · **09-08-08, 03:07 PM**

By the looks of these I think it may have something to do with ports then. Maybe it is magnetic shielding and it will protect me from harmful rays. J/K.

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