# 'FLAT' weighting on new SPL meter



## alexesposito (Mar 23, 2010)

Hi , 

I have a Landtek SL-5868P SPL meter: 

site: landteknet |dot| net 
manual: (type on google this text 'sl-5868P-sp4.pdf') 

(sorry I can't post url) 

this instrument is very inaccurate in the higher frequency without a specific calibration file, but can be done in low frequency (20 -200 Hz), I think , and I can use it for sub frequency. 

This SPL meter is particular becouse have the 'FLAT' weighting apart the 'A' and 'C' and have a +-1 dB accuracy. In my test, the 'FLAT' mode on 20 Hz, add 5 dB more then 'C' mode (this is a very good think to my opinion). 

On frequency more then 5000 Hz the 'C' and FLAT are identical and cut over 8000 Hz (for this reason I can't use it for higher frequency but and only for low frequency). 

I don't known how is accurate the 'FLAT' weighting ... I think is much better then 'C' weighting. Do you suggest to add some compensation (calibration file) on 20-200 Hz for this instrument ? 

Thanks ! 

Alex


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## glaufman (Nov 25, 2007)

Welcome to the Shack Alex!
Sorry but I'm unfamiliar with that meter, so without being able to compare diretly to a known meter, or sending it to a lab for characterization, I'm not sure how to advise you.


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## alexesposito (Mar 23, 2010)

Hi Greg ,

Thanks for your response.

This SPL meter is not common, you have right 

But, if possible, I like to understand how 'FLAT' weighting is better then 'C' weighting.

On the web there is a generalization graph of 'A' , 'C' weighting and is possible see the difference.

I like to see a generalization graph of 'C' , 'FLAT' weighting to see the difference.

Or if not possible I like to uderstand if for 'FLAT' weighting is better add some compensation like for example:

20 Hz + 2.0 dB
25 Hz + 1.5 dB
30 Hz + 1.0 dB
35 Hz + 0.5 dB

I think that exist others SPL meters with 'FLAT' weighting.

Please help !


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## glaufman (Nov 25, 2007)

The trouble is: A weighting is very specifically defined. C weighting is very specifically defined. FLAT, however, implies no weighting. If this was true, there would be no compensation needed. But unless that's a very high end meter (and maybe even if it is) I highly doubt it is truly flat. 
Assuming it's not completely flat over the frequency range you're interested in, it's impossible to recommend any correction factors with any degree of accuracy, without testing the meter with known equipment, such as might be done at a calibration lab.

For the sake of playing around, you could try the meter flat with no compensation, and run the same test with the meter set to "C" with "C" checked in REW, and see how they compare. I just don't think those results will be all that meaningful if you're after accuracy.


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## alexesposito (Mar 23, 2010)

Hi Greg ,

Aprt this I have the Berigher ECM8000 I consider to use this generic calibration file:

19.95 -3.09
25.12 -2.08
31.62 -1.30
39.81 -0.83
50.12 -0.41
63.10 -0.14
79.43 0.00
100.00 0.15
125.89 0.22
158.49 0.22
199.53 0.26

what do you thing of this calibration file for ECM8000 ? 

Can be useful, for your opinion, a comparison between the ECM8000 with this calibration file and Landtek SL-5868P without any calibration file ?

Do you have some suggestion ?

Thanks !

Alex


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## glaufman (Nov 25, 2007)

If you're not after absolute accuracy (which can only be achieved with a custom made calibration file), then yes, comparing to an ECM with a generic cal file can work. Within reason. Care must be taken to ensure indentical placement and orientation of the respective capsules in the mics. Further any cal file can only be trusted in the orientation the file was intended for. If you use our generic cal file for the ECM (which I believe is more detailed than the one you posted above) that's horizontal. 
Good luck and let us know what you come up with!


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## alexesposito (Mar 23, 2010)

Hi Greg ,

Can you please post your generic ECM8000 calibration file ?

Thanks !

Alex


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## glaufman (Nov 25, 2007)

You can find it, among others, in our downloads area:
http://www.hometheatershack.com/forums/downloads-area/


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## alexesposito (Mar 23, 2010)

Hi Greg , 

Today I have received the Creative Audigy 2 ZS and it is perferct (only +-0.1 dB 20-20.000) very good. 

but the ECM8000 required a 48 Volt phantom power and for this reason I have purchase this mic preamplifier: 

MXLMic Mate (USB preamplifier with phantom power) 

and it is very very bad !!! with accuracy more then +-4 dB (20-20.000) 

I like to keep my GREAT Creative Audigy 2 ZS and search a good 48 phantom power supply (without preamplifier) 

Normally a standard 48 phantom power supply can change the frequency response ? 

Do you suggest something with small dimension for 30/70$ ? 

Thanks ! 

Alex


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## alexesposito (Mar 23, 2010)

What do you think of this:

ART Phantom II Dual Phantom Power Supply (Amazon 49$ new) ?

Some other alternative ?


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## glaufman (Nov 25, 2007)

Alex- Normally our suggestion for phantom power is the Xenyx 502 mixer, but this would also function as a preamp... I know the 802 that I use has a very flat response... I'm sure you'd be satisfied with either.


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