Which is the correct FRD for WM 61

[Aucosticraft]

While searching frd files for Panasonic wm61 I found few here most are bit alike. but whats shown in datasheet is much different. which one should be considered?

http://www.panasonic.com/industrial/...61_a_b_dne.pdf

other files are uploaded in zip.

[aczern]

http://www.audioxpress.com/magsdirx/...avaras2861.pdf

[wintermute]

The problem with using a generic calibration file is that it won't be an exact match for your particular microphone.. It will probably make it better but won't be 100% right.

graphic below from Eric Wallin's site Eric Wallin's Internet Homepage



As you can see, you would not want to use a calibration file of the worst performing mic with the best performing mic! Even a calibration file made from the average of all of the mic's will be not appropriate for mics at either end of the spectrum..

Best you can hope for is that your mic is similar to the calibration file you have.

If you have a good tweeter, with reliable published curves, you can take a measurement of it and compare, and it MAY give you an idea as to how far from flat your mic is... Even better if you know someone who does have a calibrated mic, do back to back measurements and make your own calibration file

Tony.

[Aucosticraft]

Thanks Wintermute and aczern,

Can I say that at higher frequencies worst error can be 2db?

btw anyone knows what is the standard procedure to calibrate mic? or any link

[DavidL]

Kim Girardin used to calibrate mics. On the Liberty Instruments homepage they state that Currently our sales and basic support inquiries are being handled by Kim Girardin (kmgrdn @ luminet.net
They also sell panasonic based mics.

[wintermute]

Well the curves in the article that aczern posted had up to nearly 5db error without the linkwitz mod and closer to 2db with the modified capsules. The range with the mics in the wallin tests is not as severe at around 3db.

The important thing is what is going to be the purpose of the measurement mic? If you just want to design crossovers and get the matching right between drivers then any absolute error is probably not really important, as around the crossover frequency both drivers will be exhibiting the same over all error so their relative differences will be the same.

I think it will only be important if you are trying to adjust levels (padding or response shaping) as if the mic is telling you the wrong absolute level you may over or under correct.

Tony.

[Aucosticraft]

Originally Posted by wintermute

Well the curves in the article that aczern posted had up to nearly 5db error without the linkwitz mod and closer to 2db with the modified capsules. The range with the mics in the wallin tests is not as severe at around 3db.

Well, Considering the article that aczern posted, the difference between the two extreme graph is not more than 2db ( typicaly 1.5 db). so any of the four graphs used for calibration would lead to max 2db error. thats what i wanted to say ( probably I am not that good in framing sentences).

Originally Posted by wintermute

The important thing is what is going to be the purpose of the measurement mic?

Tony, this moment although I am going to use to check the frequency response of the speakers. matching cross overs etc. but later I would like to use it for some serious measurement. ( I am closely watching your forum "splicing nearfield to farfield" although being virgin to this thing I am not putting my words there.)

But any thing we start we start from basic. then we move to detailed.
so is my idea of using mic.

[wintermute]

Sorry it was me having a blonde moment You are of course correct and there is nothing wrong with your phrasing I was looking at the absolute values when I should have been looking at the relative!

I made some more measurements this afternoon, the spicing nearfield to farfield thread has deviated quite a bit from the original topic, but has been very beneficial for me that it has

My mic is not calibrated unfortunately, but the particular capsules I have (panasonic WM-60AY) are supposed to be very flat so I'm not worrying about it too much.. I end up setting the tweeter padding by ear as when I do it with the mic they sound too high to me, that may be my taste or it might be the mic is reading lower than it should at high frequencies. (certainly the old one had become so, the measurements this afternoon are actually quite flat from 2000 to about 15000 Hz), and I have no doubt now as to why something doesn't sound right

I've read somewhere before about making calibration files, but I can't remember where. I think the method is to measure a good speaker with the calibrated mic, then measure with the uncalibrated mic in the exact same position. if you subtract the calibrated curve from the uncalibrated curve the result should be the difference between the two which I guess you export and put into the calibration file format.

I just did a google search and funnily enough turned up another audio-express article on diy mic calibration... I was on the right track but missed a few important details (such as making sure the levels were adjusted to match! http://www.audioxpress.com/reviews/media/tipton3042.pdf

Tony.

[ente]

Hi aucosticraft,

without a reliable reference mic the job becomes a little tricky. Here are some articles dealing with the calibration of mics:

http://www.earthworksaudio.com/wp-co...sures-mics.pdf

http://www.fesb.hr/~mateljan/arta/Ap...r-Rev03Eng.pdf

Chapter 5.2 and 5.3
http://www.fesb.hr/~mateljan/arta/Ap...TA-HB-D2.3.pdf

Chapter 2
http://www.fesb.hr/~mateljan/arta/Ap...-H&T-D1.01.pdf

Regards
Heinrich

[Aucosticraft]

Thanks Wintermute and ente,

wintermute, I have opened your document and is reading it.

@ente. Is there any English version for last two chapters ? It would be of great help to me.