Spl meter recomendations

[Hogues92]

I'm looking to get a spl meter and have hit a bit of a snag. Radio Shack won't have any in stock untill mid June. That's right, June. Does any one have a good, inexpensive alternative? Not much on ebay except these:


ebay1 (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2588014940&category=4678)

ebay2 (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2589480860&category=25423)

Thanks,

Mike

[amnesiacv2]

WHen you say Rat Shack is out till mid-June, are you referring to their online store or your local store? If the latter, do you only have one in your vincinity?

I managed to find a couple local Radio Shacks that still had the analog meters (Cat# 33-4050 - now discontinued) in stock as recently as last week, and almost all of them should have the Digital SPL meters (Cat# 33-2055) in stock.

At worst, 1-800-The-Shack should have some in stock. Honestly, the Radio Shack meters are a great buy at twice the price, and are worth hunting down.

[Hogues92]

I called about six or seven local stores and nobody has the analog meter. I didn't ask about the digital because I was under the impression that it was not very good. The 1-800-theshack number was how I found out it was on back order untill june.

Mike

[vbjeff]

Cat# 33-4050 is not discontinued, it is a new model that replaced the discontinued Cat# 33-2050. If you go to the Radio Shack web site (link below) and enter a zipcode, it should list stores in your area that have them in stock. You can try different zip codes to look for different stores. There are at least 6 stores near me that have them in stock.
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=33-4050

[fanuminski]

Does anyone know if there are corrections
to the digital Radio Shack SPL meter?
I have seen postings on the corrections to
Decibel readings of the older analog style, but I don't know
if they apply to the digital model that
I purchased.

[Ajax]

Don't know for sure if these corrections apply to the digital version of the meter, but I would think they do.

Radio Shack SPL Meter Corrections
------------------------------------
10hz.....+20db
12.5hz...+16.5db
16hz.....+11.5db
20hz.....+7.5db
25hz.....+5db
31.5hz...+3db
40hz.....+2.5db
50hz.....+1.5db
63hz.....+1.5db
80hz.....+1.5db
100hz....+2db
125hz....+.5db
160hz....-.5db
200hz....-.5db
250hz....+.5db
315hz....-.5db
400hz....0db
500hz....-.5db
630hz....0db
800hz....0db
1k.......0db
1.25k....0db
1.6k.....-.5db
2k.......-1.5db
2.5k.....-1.5db
3.15k....-1.5db
4k.......-2db
5k.......-2db
6.3k.....-2db
8k.......-2db
10k......-1db
12.5k....+.5db
16k......0db
20k......+1db

THX Home Theater 16000 -8.5
20000 -11.2

At a given frequency, you add/subtract the above amounts to/from the meter reading to get the correct reading. For example, if you're running a 40hz tone, and the meter reads 80db, your actuall hearing 82.5db. If you're running a 2khz tone, and the meter reads 80db, you're actually hearing 78.5db.

Above corrections stolen from;
http://www.danmarx.org/audioinnovation

[fanuminski]

thanks Ajax
I really would like someone to confirm
if they do apply to the digital SPL
meter - if possible.
(I wonder how the corrections originated?)

[Hogues92]

I really would like someone to confirm if they do apply to the digital SPL meter

Me too, I have a freind that will lend me his.

Mike

[Ajax]

Hey guys, check out this thread. Now you'll REALLY be confused
;)

http://hsuresearch.com/forum/showthread.php?s=&threadid=539

[Lwang]

Yes, both digital and analog RS SPL meters has low freq rolloff.

The reason for the rolloff is so that ULF sound very near the meter does not set it off erratically. Things like fabric rubbing, movement of the meter itself, people passing wind nearby, etc.

[Ajax]

LOL! Yeah! You gotta watch those low frequency sounds. They can really mess things up!

Thanks Lwang!

[Ajax]

Borrowed this from another forum. Good basic explanation of what to do.

A Quick Overview of Home Theater Calibration

INTRODUCTION

Fellow moderator Jay Mitchosky outlined above that true home theater enjoyment is often the result of system calibration and accuracy. To that end, there are several test DVDs on the market, designed with patterns to help you dial your HT system. In the dozen discs available, there are two which are widely accepted as the most useful: Avia and Video Essentials.

Avia was designed by Guy Kuo & Ovation software. You'll find many posts from Guy here on the HTF, he's a regular poster and usually pretty helpful when it comes to Avia related issues.

Video Essentials was designed by Joe Kane, who is also a member here at the HTF. Joe also founded the well respected imaging-science foundation (ISF), and Video Essentials has been the calibration tool of choice since the days of laserdisc. VE has recently been discontinued, and Joe is set to release Digital Video Essentials sometime in late 2002 / early 2003.


BASIC AUDIO CALIBRATION STEPS

- Acquire a calibration disc (like those mentioned above) and a SPL meter like the Radio Shack SPL meter.


- Inside your receiver menus somewhere, there should be speaker level adjustments for each of the speaker channels (consult your manual if necessary). Set each of the individual speaker settings to 0. Go into the menu- and adjust all the available speaker settings so they aren't boosting or cutting. Set them all at 0. It also might be a good idea to turn off all Treble/Bass boosts or cutting.

- Set your meter to "slow" response, and the weighting to the setting suggested by the tones you're using (both VE and AVIA offer onscreen instructions on proper meter settings).

- Setup your meter at your main listening position, appoximately at the height of your nose while seated, and point it forward, angled upward at about 40 degrees (a decent rule of thumb is aiming it at the point where the ceiling meets the front wall). It is very helpful to place the meter on a camera tripod- the RS SPL meter has a nice tripod mount on the back- this will help make sure you keep it in one spot.

- Insert you test tone disc and begin the audio test for speaker calibration. Both Avia and VE have these tests, and they should be resonably easy to find.

- The majority of discs start with the left speaker tone. While the left speaker tone is playing- increase the master volume position until you reach a reading of 75db on your meter (or 85 is you're using Avia- double check the instructions for your particular disc to determine target level. The 75db number is specific to certain tones, while others a designed to be calibrated to 85db... this will depend on which disc you're using to calibrate.).

- There is sometimes confusion on how the meter dial/VU needle display operates. It is pretty simple: you set the dial on a number (say for example 70). Now the needle VU meter is displaying SPL relative to 70-- so when the needle hits the middle "0" position, that means the SPL of the thing you're measuring is 70db of spl. If it reads -4, that means it is 4 under 70, or 66db. Similarly if the dial is set to 80, the needle VU meter is displaying SPL relative to 80- so 0 on the meter means 80db of spl. If the dial is set to 90, the needle is relative to 90, and so on.

So, to measure 75db spl output, set the dial on the meter to 70, and then adjust the speaker volume until the little needle hits +5 position on the meter display.

So, to measure 85db spl output, set the dial on the meter to 80, and then adjust the speaker volume until the little needle hits +5 position on the meter display.

- Note that it doesn't matter at what position your master volume knob is placed, or for that matter what number it says. Calibration is a measure of OUTPUT, so even if the volume knob was marked with Japanese characters- you should still be able to calibrate with no problem. Some people choose to set their master volume to a 00 position and adjust the levels from that point-- which is fine but not at all necessary. (If you chose to do this- simply set the master volume at 00, and then play the tones, using the speaker controls to get the desired meter reading.)

- As the tone cycles to the other speakers- leave the master volume alone- and adjust the individual speaker levels in the receiver menu so that each speaker measures the same level on the meter. It may take a couple times through to get it right- but keep working at it, and leave the meter in the same place.

- At the end, take note of where your master volume knob is (what number)- this is Dolby's Ref level. You probably won't listen much at that position-- but often it is helpful to know how many clicks below ref you are.


WHAT THE HECK IS REF LEVEL ANYWAY?

In a nutshell, Dolby specifies an ideal playback level for their theatrical soundtracks and for the mixing envirinments in which those soundtracks are created. So, unlike music, movies are technically created with a standard playback level in mind. Based upon this intended level, dialog and effects are mixed at very specific levels to offer similar sound levels across various dolby soundtracks.

This playback level is basically defined as 105db peak level from any single speaker in the dolby playback system. By using tones on VE or Avia- they are specifically defined to give you this playback level.

Since VE's test tones are exactly 30 steps below the maximum level - calibrating that tone to 75db of SPL in your room means you have calibrated your system to playback 105db when given a peak signal.

Similarly, since Avia's test tones are exactly 20 steps below the maximum level - calibrating that tone to 85db of SPL in your room means you have calibrated your system to playback 105db when given a peak signal.

So, if you calibrate using those tones, and their intended target level (75db for VE or 85db for Avia)- that position on your volume knob will be dolby's ref level, providing you with a system that is now calibrated to offer 105db peak output.

Most home users don't listen at dolby's specified levels- but often it is a good point of ref when seeking help or advice on forums such as this one.