Accurate spl measuring

marty1

Active Member
I am going to try to get the hang of using REW, but first I need a sound card with line in.

First of all can anyone recommend a high quality sound card that i can connect to my laptop?

Secondly is there an spl meter that is capable of accurately measuring sub response down to 10hz without needing correction on the readings, that i can use with rew?

Thanks
Martin
 

Nimby

Distinguished Member
I am going to try to get the hang of using REW, but first I need a sound card with line in.

First of all can anyone recommend a high quality sound card that i can connect to my laptop?

Secondly is there an spl meter that is capable of accurately measuring sub response down to 10hz without needing correction on the readings, that i can use with rew?

Thanks
Martin
The standard answer is that if you want to measure reliably to 10Hz you will have to invest in a better microphone than that stuck on the end of an RS meter. Even then you have no idea if the better unit is accurately calibrated. Professional calibration is expensive and should be repeated at intervals. Most calibrators won't touch cheap SPL meters.

Unless you are testing to exacting standards I suggest you forget all of the above. Use the RS meter and load the matching REW .cal file. Then use the longest test sweeps with REW. These ensure repeatability below 20Hz. The standard sweep is not repeatable with any real accuracy. Just click on the REW Measured button to see all your graphs overlapping.

My own testing suggests that there is little to choose between test microphones and SPL meters in this price bracket. My two RS meters were exactly the same despite a 15 year difference in age and there being two different models.

My Galaxy 140 SPL meter matched the RS meters so closely that it didn't matter. Oddly the Behringer calibration microphone and phantom power preamp disagreed. By simple elimination of the odd-man-out the Behringer loses despite its greater price including the preamp.

For testing with REW I like the Galaxy 140 meter best because it is easy to use and has a nice screen. It also has useful peak hold features. Sadly they are expensive in the UK but much cheaper in the US. Avoid the cheaper Galaxy models as they don't have an output socket.

Because REW can cut through the harmonic crap to the fundamental do not be surprised if your subwoofer produces little useful output at 10Hz. Even with eight 15" drivers in my subwoofer 10hz has little real value beyond bragging rights.

I can't recommend any particular USB soundcard with Line-in because the popular SB Live! choice has been discontinued. Others may have useful suggestions.

A True Infinite Baffle Subwoofer: More measuring.
 

Aerial Man

Novice Member
Theres really no need for anything better than the radioshack meter. Lets face it, you cannot hear the tiny difference of a more accurate meter.

When you pick at a system to that level you are on the road to a never ending quest for perfection £££££££££

There has to be a cutoff point somewhere.
 

marty1

Active Member
Sorry if this is a daft question, but how does the screen on the spl matter?

I thought that you just plug it into laptop and rew reads what the spl measures?

I have only ever used carma from audionet and It took me a while to get the hang of that :confused: Still struggling now :eek:

Regards
Martin
 

Aerial Man

Novice Member
Another point to make, is that it's all well and good taking the most accurate measurements but if you cannot make adjustments to within the same level of accuracy then whats the point?

At the end of the day you are plotting a curve, if that curve looks good then you have made the most of your system. The curve will look the same with any meter, then you have the task of trying to make adjustments which may or may not be acheived, let alone worrying about the accuracy of your meter.
 

Member 639844

Former Advertiser
Sorry if this is a daft question, but how does the screen on the spl matter?

I thought that you just plug it into laptop and rew reads what the spl measures?

I have only ever used carma from audionet and It took me a while to get the hang of that :confused: Still struggling now :eek:

Regards
Martin
You output your test tone from REW via your system, and the SPL meter will read what level is being output, and typically, once your spl meter is reading spl's, you adjust your systems volume till the spl meter is reading 75db. Once there, you then adjust the on screen spl meter reading displayed by REW to match that of your spl meters display (75db). This quick calibration process aligns REW with what your spl meter reads.
 

marty1

Active Member
You output your test tone from REW via your system, and the SPL meter will read what level is being output, and typically, once your spl meter is reading spl's, you adjust your systems volume till the spl meter is reading 75db. Once there, you then adjust the on screen spl meter reading displayed by REW to match that of your spl meters display (75db). This quick calibration process aligns REW with what your spl meter reads.
Thanks, I guess it will be easier to understand when i actually try it
 

Nimby

Distinguished Member
Sorry if this is a daft question, but how does the screen on the spl matter?

Martin
Sorry, I missed your question. I like the digital screen on the Galaxy SPL meter because it is so easy to read compared with a fine needle against a scale. Nothing more than that.
 

Normal Bias

Active Member
First of all can anyone recommend a high quality sound card that i can connect to my laptop?
I would like to know which sound card to get, too. Doesn't anyone have any recommendations?

Thanks.
 

Normal Bias

Active Member
Thanks. Seems there is lots of discussion about SPL meters on here but not much on sound cards, even your linked-to thread petered out inconclusively. But!... the FUD could soon be at an end because I've ordered the Behringer 222 and will soon be able to pass an authoratative and informed judgement on the matter.

In other words I'll be back asking for help with it...

:)
 

marty1

Active Member
I have got a soundcard from maplins, £19.99 so how good it will be i dont know?

Now I am quite useless with downloads so I think I have managed to download rew but i am having trouble downloading the calibration file, it says microsoft works cannot open, the file may not be supported by any of the installed converters??

What am i doing wrong?

Regards
Martin
 

AngelEyes

Distinguished Member
Hi Marty,

When you click on the cal file to download it (SPL meter cal file I presume?), it should give you a couple of options, the first being along the lines of 'Open...' and the second 'Save...'.

I am guessing you have it still set to 'open' and your system doesn't know what to open the file with on download so tried MS Works which obviously failed.

If you click on the save option and note where it was saved to (probably my documents or downloads) you then open the cal file from within the setup section of REW where it mentions the SPL meter calibration files.

Hope that helps.

Adam :)
 

Stu V

Well-known Member
I have got a soundcard from maplins, £19.99 so how good it will be i dont know?

Regards
Martin
If this is the soundcard you bought, then it should be fine. I bought the same one and it works ok.
 

marty1

Active Member
Thats the one, thats good to hear :thumbsup:

Can anyone help me with the calibration file that i am unable to open?

Regards

Martin
 
Thats the one, thats good to hear :thumbsup:

Can anyone help me with the calibration file that i am unable to open?

Regards

Martin
Have you read AngelEyes post? I suspect he's right on the money.

It looks as though either you are telling the browser to open it (and it's trying with MS Works) or once you've downloading it, you are double clicking on it and expecting it to do something (which it is but trying to use the wrong program)

Save it to a folder on your computer using the browser (right click and choose 'save target' if necessary) and then open it from within REW.
 

marty1

Active Member
Hi Marty,

When you click on the cal file to download it (SPL meter cal file I presume?), it should give you a couple of options, the first being along the lines of 'Open...' and the second 'Save...'.

I am guessing you have it still set to 'open' and your system doesn't know what to open the file with on download so tried MS Works which obviously failed.

If you click on the save option and note where it was saved to (probably my documents or downloads) you then open the cal file from within the setup section of REW where it mentions the SPL meter calibration files.

Hope that helps.

Sorry I missed your post before asking the same question you already answered for me :suicide:

Thanks :thumbsup:
 

micb3rd

Novice Member
Theres really no need for anything better than the radioshack meter. Lets face it, you cannot hear the tiny difference of a more accurate meter.

When you pick at a system to that level you are on the road to a never ending quest for perfection £££££££££

There has to be a cutoff point somewhere.
RadioShack mics are far from flat, even with a correction file it is a best guess as the tolerances and responces are different.

Yeah I use them for quick portable checks and they are no doubt useful.

But for most if you going for the trouble of fine tuning the system with an EQ why not use something that is better?
 

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