SPL Meter question

Discussion in 'Speakers' started by aht3, Sep 6, 2007.

  1. aht3

    aht3 Stunt Coordinator

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    Do you guys recommend analog or digital? What brand and where is the best place to get it?


    Thanks,

    Andrew
     
  2. drobbins

    drobbins Screenwriter

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  3. troy evans

    troy evans Screenwriter

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    Analog, because it gives a more precise bass reading. This is helpful when you adjust the subwoofer.
     
  4. Luis Gabriel Gerena

    Luis Gabriel Gerena Second Unit

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    I will advice you you to get something a bit better and calibrated or get the RS and get someone to calibrate it for you. The RS is a nice meter but without calibration you may as well not do anything as you wont be able to know if the readings are right or not.
    Is like trying to edit photos in a computer with a non calibrated Monitor.... :)
     
  5. aht3

    aht3 Stunt Coordinator

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    so....what is better and who is "someone"?


    All,
    Thanks for the help
     
  6. Luis Gabriel Gerena

    Luis Gabriel Gerena Second Unit

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  7. Alan Wise

    Alan Wise Stunt Coordinator

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    I have upgraded and purchased an AudioControls SA-3050 RTA (Real Time Analyzer) to perform further acoustic analysis of my system and listening area.
    I think I will pit my Radio Shack SPL meter against it and see how close they are in SPL measurments.

    Al Wise
     
  8. aht3

    aht3 Stunt Coordinator

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    Most appreciated. I look forward to the results.
     
  9. Phaseshift

    Phaseshift Agent

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    My technical staff had done such a study a while back for a client who is doing a auto-EQ feature on a integrated product. We did the lab and real world testing using an array of mics and available equipment. This may be a painful post for some to read, but I had promised to share the info when I could.

    The short answer to the folks asking about Radio Shack SPL meters- Where you hold the thing in the room probably has a greater impact on the measurement than the meter. However, the study that we did reveals some significant deviations in the lower cost units. We were asked to share only the conclusions and not the data files which is understandable (the client paid quite a bit of money for the study, lab time etc…). However, they were kind enough to agree to us sharing the text review and some of the conclusion wrap up with the general public.

    Here are the test units and result overview.

    Handheld units-

    Ivie handheld analyzer (3 each - now out of production as I understand, but the client has a few of them and wanted to use this as a baseline)
    TES SPL meter (3 each)
    NTI Minilizer with mic (3 each)
    Radio Shack analog SPL meter (I believe we had 6 of them- they are quite popular)

    Also mics based on a standard test setup using SoundCheck as the baseline T&M system.
    Earthworks M30
    B&K 4134
    GRAS 40AC
    Audix TR 40

    Professional test gear-

    We ran this against our AP System 1 and also threw in the latest hardware and software from Linear X, Audiomatica (Clio QC 8) and DRA (MLSSA 10W1) to see how they stack up as well. Lastly, we brought in Room EQ Wizard based on the request from the marketing folks.

    All calibration done using a GRAS 42AP series pistonphone. All electrical components and platforms were calibrated per manufacturers instructions / routines.

    Here is how it went in our lab compared to our standards-

    Hand-held analyzers and SPL meters

    1.NTI
    2.Ivie
    3.TES
    4.Radio Shack

    Repeatability went to the NTI – just better than the Ivie. The key was in consistency. These units were very close in all respects. If it were me using the thing, I would probably take the Ivie as it is color, faster and has a higher coolness factor going for it. I say that as the owner of probably 5 of the NTI Minilyzers (use them in our listening room and for field reference measurements in QA services)

    There is a big gap between the NTI – Ivie level and the Radio Shack – TES level.
    A.The absolute measurement numbers were consistently unpredictable. A few points were right on the money, some were off by about 5 dB. One of the RS meters was down by about 4 dB all the way across the board and another was hot by about 2 dB everywhere. We saw only slightly better results out of the TES meter, but to call it by the math, the TES performed better, even after taking only the best measurements from the Radio Shack meter.
    B.Repeatability- Fresh out of the box, the RS and TES meters were both OK in terms of reliability. Where we saw the issue was after accelerated life testing. The results were all over the place- unpredictable and poor test to test repeatability. Even using a 1K test tone the results were only fair (over 2dB of deviation was typical from one test to another). Note that the accelerated life test was cyclic heat and humidity over 96 hours +40F to +95F / 30% RH to 85% RH – not a big deal and certainly nothing like consumer audio products are tested to. We also placed all mics in the power test room in the presence of an EAI 426B test signal at 85dB. All mics were in the room as well, nothing powered up and no caps in place.

    The mics-

    1-2 - B&K / GRAS (practically identical in all regards)
    3 – Earthworks
    4 – Audix

    B&K + GRAS almost no difference. I would call these dead even and frankly, they should be. These mics represent the upper end of microphone technology and are well established as reliable and trusted measurement microphones in the professional and consumer audio community. Good stuff if you have the $$$.
    Earthworks was a close second more deviation on the low end and does not have the response out over the top like the others. Note that this mic is a close performer and costs quite a bit less then the B&K – GRAS units.
    Audix was just a bit behind the Earthworks. Again, a little lower performance on the low end and not quite the bandwidth. Also bear in mind that we are only looking at SPL response; not making any technical comparisons in other areas.

    The test platforms-

    All similar on initial measurements. As they heat up, you see some deviation, but not a huge difference.

    I am not going to fly in the face of convention here- the AP is the reference standard for the industry and at over $25K for the entry level system, it should be good.

    Listen and Clio were nearly identical. Gauge R&R comparing the systems has Clio on top by a slight margin. I would like to note that the accepted error margin here is greater then the separation of the 2 test platforms; therefore I would call this test conclusive only in that the platforms are both excellent performers compared to the AP and one another. Both outperformed the AP in terms of R&R testing.
    MLSSA measurements were right there with Listen and Clio, but as many of you already know, the MLSSA platform has heat soak issues. Absolutely measurements are good, R&R is only fair. Note that this system was supported by an old computer; one that we have used for MLSSA support for several years. We do not believe the computer to have a significant impact on the test, but when you are dealing with numbers and results as close as we are here, every variable has to be taken into account.
    LMS comes in at about the MLSSA level; depending on the mic. If you use the supplied microphone, the results are not so hot. Using better microphones increases the accuracy of the absolute measurements as well as the repeatability.
    Room EQ Wiz is a free software package. It is unfortunately not a good performer in absolute measurements and certainly poor in terms of repeatability. Above 500Hz, the performance is better, but the resolution is so low that I would be reluctant to accept any test data based on that platform.

    PCB comment on platform testing – We only looked at one aspect of the platforms. If you look at all the factors including the software / GUI, cost, availability, service, upgrades and so on you have a much better chance of picking a clear winner. You simply can not compare a maxed out Listen rig to the basic LMS bundle and say that it is fair. Listen has so many more features, is so much more powerful as a post processor and has super engineering brain power behind it. Clio is another case where looking at the total package is going to give you ore options. The software platform is impressive and the ease of use is certainly the best of the lot in my opinion. It is not quite at the same level as Listen in terms of features, but you can have 3 complete Clio’s for the price of 1 Listen. LMS has acceptance going for it and it seems that even the competitors agree as they will all import LMS / Leap format data. MLSSA is a strong technical performer and one of the cores that s many high end and consumer level systems were built and tested on, but the DOS platform and lack of available PC’s that accept the older ISA format is a tough thing to overcome.
     
  10. TimMc

    TimMc Stunt Coordinator

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    Andrew - after all that info, you still might want to check your budget & then check the prices on all of the gear mentioned above. Only you know how much you expect from such a product and if you'll think another handheld unit is worth 20 or more times more to you than an RS unit. The RS is relatively ubiquitous because of that price, and if you find the sale or coupon deal (and the calibrated spreadsheets, etc. available on the Web) you might also get yours for ~$30-35 and then get to decide if the extra hundreds - and it does appear to be a good handful of hundreds - of dollars more for the other units are worth it to you.
     
  11. Mike Frezon

    Mike Frezon Moderator
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    THAT was the only thing that was missing from Phil's informative post: the cost of the different meters. [​IMG]
     
  12. Phaseshift

    Phaseshift Agent

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    Just FYI-

    The price point where things start getting reliable and repeatable from my point of view is with the NIT Minilyzer - about $600 I believe. I am not a purchasing guy- please do your own research on costs, but I think the NIT rig I am taking about here is under $700.

    Earthworks M30 = about $350
    Audix Mic = about $300
    B&K or GRAS mic - big $$$ and you have nothing but a mic
    LMS + Leap = the big bargain - $1500 and you can get them all- maybe less than than
    Clio QC - another bargain - about $3400 plus the PC, but a fantastic package
    MLSSA = about $3900
    Listen - $ over 10K
     
  13. aht3

    aht3 Stunt Coordinator

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    Wow all and thanks for the help.For these prices, I'll just get a nice home system for the LR and guess. I think that if I was in the business and using it a lot, this would make sense. It kinda of like buying a bulldozer to knock down a tree. Thanks for the help. It seems to be cheaper to get someone to come out and do it for me.


    thanks again
     
  14. Mike Frezon

    Mike Frezon Moderator
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    Andrew: Don't get scared off by those prices.

    You DEFINITELY want an SPL meter to calibrate whatever system you get. But those prices are a reason why most people who are into this dopey little hobby use the Radio Shack SPL Meter which you can pick up for $20 to $40.
     
  15. Luis Gabriel Gerena

    Luis Gabriel Gerena Second Unit

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    If I recall correctly I think a member of HT shack was charging like $40 or so to calibrate the RS one. I think $100 or less is not a bad investment specially if you plan to add acoustic treatments.
     
  16. ChrisWiggles

    ChrisWiggles Producer

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    This is erroneous information. The precision of the two meters is identical, only the readout is different.
     
  17. troy evans

    troy evans Screenwriter

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    [​IMG] I wouldn't say that my friend. On one hand, the digital meter has a way of rounding up a decible in my experience with it. I like the ability of the analog meter to read the 74.2,74.3,74.4 etc,etc ranges. Then I get to decide what range is closest when I set my speakers. That means the precision of the two meters is not in fact equal. This is more relavent within the bass range when setting the subwoofer. You could argue that 1db is not that big a deal to most, but, I prefer my settings to be as accurate as I can get outside of getting an expert calibration. On the other hand, the analog meter is less expensive. So, even if you feel the digital spl is equal in ability to the analog, the analog is still the way to go for value alone.[​IMG]
     
  18. ChrisWiggles

    ChrisWiggles Producer

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    You are attributing a number of opinions to me that I have not said. I simply pointed out that the precision of the two meters is identical, which is true since the meters themselves are identical. Only the readout differs. Some people find one or the other more user-friendly. In neither case is the precision of the meter really capable of readings more fine than a db, especially temporally, nor is that usually necessary.

    I own and use and prefer the analog meter, because I find it more intuitive to use, but not because it has any added precision(or accuracy), which it does not.
     
  19. troy evans

    troy evans Screenwriter

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    Sounds like you have had experience with both digital and analog, so, what am I missing? If the digital meter rounds a reading of let's say 74.3db up to 75db even though that's incorrect they both have the same precision? If the readout gives me incorrect info then regardless of wether or not the meters are identical to one another in precision it will make the digital meter less accurate. Like I said before, some people may not care about a 1db difference.
     
  20. clubfoot

    clubfoot Auditioning

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    Phaseshift,...would you mind elaborating on your REW findings, as to what setup was used for the comparison, i.e. mic/s, computer & OS and .cal files etc?
     

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