New and improved (?) "Radio Shack" meter (1 Viewer)

[Kevin C Brown]

http://www.atiaudio.com/?fa=product&id=170#

A blurb in the latest Hi Fi News (UM mag) about how ATI (not the same as the amplifier company) tried a whole bunch of mods, and then used the best ones to make it more accurate. fwiw.

Personally, the Radio Shack meter is so useful because of the published correction tables. Don't know if they'd be the same or not with this guy.

 

[BradJudy]

Okay, this is a pet peeve of mine, so forgive the rant...

The "correction" values for the RS meter are NOT specific to the RS meter. These are the compensations for C-weighting and any meter that uses C-weighting needs to use these values if you want to measure against a flat scale rather than a C-weighted curve.

 

[JohnPrader]

In fact, in following posts on great (and free!) programs like Room Eq Wizard, there are more caveats. The Room Eq wizard program has C-weighting tables that can be invoked input devices. There are additional download tables for correcting frequency response (FR) anomalies with the RS meter, as well. However, these tables are general. They are not always accurate meter to meter. The RS meters show substantial variation meter-to-meter and changes made to the product over time compound the issue. All of these render the basic product useful only in a general fashion.

While my RS meter has been a useful tool, I am presently scratching the itch to purchase a calibrated microphone (and mic preamp) to use in an effort to tame bass response in my listening room with eq. The RS meter was good during the "learning curve" portion of my efforts, now I'm looking to tweak it as best I can without hiring a third party to do it for me. Too bad RS doesn't take note and produce a more uniform product that we laypersons could be more reliant upon.

 

[JeremyErwin]

AVSForum has a thread on calibrating the meter. Those corrections show, for instance, that sensitivity to 20 Hz is reduced by 12.38 decibels.

C-weighting is less drastic. Perhaps a reduction of 5 dB?

 

[SteveCallas]

Agreed, and I worry that those who use the RS meter to EQ their bass response flat with a BFD may actually, in certain cases, be making their bass response worse. I'd love to meet up with someone who has a calibrated mic so I can get some accurate correction factors to apply to my meter.

 

[BradJudy]

I have a calibrated ECM8000 mic (I had it calibrated for a specific higher-demand reason) and I can say that based on my calibration file and the ones I have seen for a handful of other ECM8000s, there is no reason to bother with calibration for 95% of home use. The corrections from 20-6kHz were all less than 1db (generally around 0.2db) and the worst was 2db off in the 10kHz region (these numbers are for my mic, but others I have seen have similar results).

I have compared my mic with my RS meter, but don't have any screenshots like Ikka's. IIRC, mine was closer to 3db different around 20Hz with the C-weighting compensation.

 

[Kevin C Brown]

BJ- There are actually more than 1 set of cal factors for the R.S. meter out there. Someone actually did measure his meter vs a calibrated mike and posted those values. I have a buddy (who might even show up to this thread) who found a calibrated mike for about $100. So they do not cost an arm and a leg.

I did email the ATI people about if they could publish some calibration numbers for their meter. I'll be curious... I know one of the mods for the RS meter was specifically to make it more accurate at low freqs. (Something about adding a capacitor or something.)

 

[BradJudy]

I know they don't cost a ton. An ECM8000 is ~$50 and having it calibrated is ~$50, but since the calibration gains you almost nothing for this purpose, why not save $50? That $50 will pay for the mic pre-amp you'll need to go with it.

I know people have had their RS meters calibrated, but as mentioned here, any one person's calibration isn't particularly applicable to any other meter. I have an Aperion SPL meter in addition to my RadioShack and it's horribly off at lower frequencies, to the point it must simply be defective.

I don't mean to discourage you from pursuing more refined measurements, in fact, I generally encourage people to do so if they are interested. You can learn a lot about your system and audio in general by reading up and trying some measurement. There's a lot of good info out there on using RoomEQ Wizard which is a great place to start since it's free. There are also great commercial options like ETF and TrueRTA.

I think an ECM8000 along with a basic mic pre-amp (I have an ART MicroMix) and USB soundcard are a great combination for doing measurements. Don't forget an XLR cable and make sure the mic pre-amp has phantom power (most do, but not all). A lot of people use one of the inexpensive mixers for a mic pre-amp. You can combine the mic pre-amp and soundcard into one item also (I have an M-Audio MobilePre which is a great item for this type of thing).

 

[Kevin C Brown]

Here's the info:

http://img.villagephotos.com/p/2004-...ati-meter2.jpg

(No way to post an image with the new software?)

 

[Phil Iturralde]

Here you go , ...


Phil

 

[Kevin C Brown]

Thanks Phil!

 

[Arthur S]

Where did they come up with the "US $39.99" price? Looks like $69 to me.

 

[JeremyErwin]

The place below sells it for $40.
http://www.8thstreet.com/prod.asp?pid=27330

And this place sells it for $30
http://www.bswusa.com/proditem.asp?item=SLM100

The chief advantage of the radio shack meter was that it was commonly available, and good enough for setup purposes. Now that you have to look for it, it loses much of its appeal. You might as well seek out the most accurate (which could well be the ATI) model in that general price range.

 

[Arthur S]

Thanks Jeremy