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Radio shack SPL meter

Discussion in 'Recording' started by MisterBlue, Mar 16, 2003.

  1. MisterBlue

    MisterBlue Member


    there were a number of very interesting posts that talked about the use of the analog Radio Shack SPL/dB meter to get an idea what kind of frequency response one is getting in their control room. The gadget is rather inexpensive so I went for it and gave it a go.

    I have to say that I have not been able to get any consistent readings. I am not saying that my speaker system is crap and the FR is all over the place (which it might be but that is not the issue), but tiny variations in holding the unit or positioning myself (...I know about the effect at low frequencies) can result in up to 6 or more dB of difference. With speakers (hopefully) in the 1-3 dB tolerance range this renders the results obviously useless.

    What am I missing?
    Is it my room (only 8'x12', IMO pretty well "foam-controlled")?

    Any advice on how to conduct some useful measurements will be greatly appreciated.

    Thanks in advance,

  2. audiowkstation

    audiowkstation Active Member

    I would use a tripod.

    Attempt to place the unit where your head is during listening.

    Their are some inaccuracies with them although a calibration chart can be found on the web with a search for "radio shack spl calibration"

    When I compared one to my B&K calibration system, I found it to be amazingly accurate, within 2dB.

    Some tips as per the azimuth of the mic to sound source needs to be studied as well. One person mentioned that pointing the unit strait upwards yielded the most accurate results.

    It is a tool, not ideal but if their is a serious cancellation problem, the meter will show it.
  3. mixman77

    mixman77 Guest

  4. lowdbrent

    lowdbrent Guest

    You are not going to get usable results using the Radio Shack unit in that fashion. Why? Even though the specs say that the units SPL is fairly accurate (+/-3dB or so), the microphone element has not flat from 20Hz to 20kHz. At some frequencies the mic itself is of in excess of 20dB. How can this be? The unit is sensitive to a narrow bandwidth. It is not falt from 100Hz to 8kHz, but that is the bandwidth that is needed for measurement.

    Anyone that tunes a room with this is a nut.
  5. mixman77

    mixman77 Guest

  6. mixman77

    mixman77 Guest

    Post removed by Kevin M.
  7. lowdbrent

    lowdbrent Guest

    He is talking about the SPL meter. Many people think that they can set up a speaker system or a room eq with this. They sinewave sweeps or in some cases narrow bands of pink noise from test CD's. They look at the SPL meter to tell them how far up or down they need to adjust the EQ. The SPL meters are only using 100Hz-8kHz. The mic element is not flat. They only guarantee the unit will detect the greatest SPL in that 100Hz to 8kHz, not which frequencies are loudest. It cannot provide that kind of resolution.

    SIA SMAART lies at frequencies below 100Hz. So don't even try to work out the bottom end with it. It is a great tool for live sound and installs. I use it alot.

    The next step up would be the TEF system. It is licensed by Crown, Goldline Loft, etc...Then comes the grandaddy Meyer system.
  8. mixman77

    mixman77 Guest

  9. audiowkstation

    audiowkstation Active Member

    :roll: :d:

    It did not make a lot of clarity to me...

    Talk to the Man Kevin.

    We all know to sound "good" on an RTA, the bottom around 40 to 60 must be 7 to 9dB UP from midband average. Only the peaks in midband..."can approach" the level of the sustained bottom and if you want the crowd to not have a massive migraine, that 2 to 4K region....******MUST****** have a slight dip...at concert dB's, It would kill me to have 110dB at 3K hit me. I would not stand for it at all...

    Kevin...Hope you got some words to the Man..
  10. mixman77

    mixman77 Guest

  11. lowdbrent

    lowdbrent Guest

  12. audiowkstation

    audiowkstation Active Member

    What part of his fact did you not understand?

    Your post, just repeating Kevins post is insulting.

    I don't really think you know who we are or our expertise in acoustics, engineering, music or the recording arts. I was doing MAJOR mixing for groups you know (major 5 millions sold) in 1976.

    I certainly hope you can bring something positive to tha table because what I have read so far is useless drivel.

    Put up or go to another forum.

    This is NOT what we founded RO about.

    This is the first, and final warning of posting inaccurate deflamatory information.

    I can provide many links for people that have your level of experience.

    This is shameful, to just post a repeat of what the man said.


    Ready to fess up or go crawl in a hole?

    This is getting rather riduculous.

    Kevin, I applogize for this craziness. Where the hell he get his education from...????

    I am usually a guy that will not ever do anything but find good in a post and expound on that. You leave me no choice but to highly dissagree with your attitude and tactics.

    Don't reply to this..lowdbrent.

    Just heed it.

    Sorry Kevin, Now you know how we really feel.

    I hope you don't know this guy...

    If so, pay him a visit on me. Just a friendly conversation will do fine.

    [ March 17, 2003, 09:33 PM: Message edited by: audiokid ]
  13. audiowkstation

    audiowkstation Active Member

    I get it, go back over there, we do not subscribe to your tactics lowdbrent.

    I see you are totally on top of your game with the links:


    Really, I mean it. This is not learning, this is harrassing people that know their business.

    I will not have it.

    I want to get along, I use to live near Tulsa, I feel you can be a fine asset...but not at this rate..we do things accurate, with compassion and feelings toward our fellow man.

    [ March 17, 2003, 09:31 PM: Message edited by: audiokid ]
  14. lowdbrent

    lowdbrent Guest

    I quoted him in response, to answer him. Maybe you didn't read what I said. I don't know. I don't see anything offensive in what I said.

    He said surely they meant RTA, and I told him that no, people do attempt to use a SLM. I wouldn't do it. some do. What's the deal there. Then I identified that it wasn't class 2 or 3, and it makes relative not absolute measurements. The microphone element is a panasonic I believe, and is not flat, nor is the circuitry, and so I attempted to post a link to an article that had the AP graph. I didn't insult anyone. If I had, I would have talked about their computer or their hair. I clarified. That's it. I have read the F word by you and others. That's not offensive?
  15. audiokid

    audiokid Staff

    seems to me the reality of war and a full moon has everyone on edge. Man there's a cold chill.

  16. cjenrick

    cjenrick Active Member

    Darn it, where's Fat's when we need him! LOL!

  17. Kurt Foster

    Kurt Foster Distinguished Member

    I'm here...just watchin' ready to pick up a barstool or a micstand if needed :D All seems cool... Kurt Hi Chris... :w:
  18. cjenrick

    cjenrick Active Member

    That's right, if you play the Rack, you gotta know how to swing that axe! Or mic stand, or barstool! Hey , did they have the chckenwire when you played there?

    Was in town, had a cousin die a couple of months ago, burried her in the family plot outside of Drain. (my Mom's maiden name is Applegate, if you know any Ore. history)) I rode with my sister, and we only had a little while to get up and back, otherwise I woulda looked you up.

    Thanks for the Velvet Turtle flashback, forgot all about that place. Has it stopped raining yet?
  19. mixman77

    mixman77 Guest

  20. Kurt Foster

    Kurt Foster Distinguished Member

    Aww mommy! I wanna stay up!

    Chris.. Yeah! the Velvet Turtle.. The name of that guitar shop... ROCKET GUITARS, right???
    No they didn't have chicken wire at the Rack when I played there. Just the meanest g-d bouncers in town..They used to handcuff troublemakers to a metal grate in front of the club until the Cops showed up to collect them. They ended up getting sued for beating some guy up.. Man! That was a tough gig. 2 bands, 2 bandstands, three sets a night one hour on one hour off. Super loud Meyer speakers with Crest power amps. Speakers all over the place on delays to time align them. The monitor system did 120dB.. You can imagine how loud the mains were! No quiet place to go during your break. I used to go home with my head ringing. Polo Jones used to run sound. He played bass on the Bodyguard album for Whitney Huston, toured with Michael Jackson and Peter Gabriel.. He would have the mix cookin' and Hank (the owner of the Rack) would walk up to the console and push the bass guitar channel waaaaay up to get the dancers jumpin. Used to bug the sh*t out of Polo..hehehe Ahh the old days... Kurt

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