wm-61a topend peak- calibration? or resolder??

sqlkev · 15th July 2005, 03:17 AM

Just got my measurement preamp kit from highefficiencyloudspeakers.com.
The wm-61a pana. mic capsule seems to be very peaky from 10khz and up, is it due to my poor soldering skills? bad capsule? or is it a normal thing and I can calibrate it??

I'm still trying to figure out speakerworkshop to do simple FR for now. So far, I consistently get measurements with peaks above 10khz.
Help!!!!

Padel · 15th July 2005, 11:40 AM

Hi,

Have you modified the WM-61A as recommended here ?

jbateman · 15th July 2005, 11:46 AM

This is the response of my WM61a mic capsule...although it's about a 5 year old model. I also have a second one, which is the same shape but about 1 dB lower at the peak.

Padel · 15th July 2005, 12:02 PM

Quote:

Originally posted by jbateman
This is the response of my WM61a mic capsule...although it's about a 5 year old model. I also have a second one, which is the same shape but about 1 dB lower at the peak.

Hi jbateman,

Can you please tell me where can I find the generic calibration files of the WM-61A?
I'm a bit confused, the plot you posted, is the actually frequency response of the capsule or the calibration files for correction?
If these are the calibration files then the capsule should starting to roll off at about 5KHz, right?

Padel

wintermute · 15th July 2005, 12:04 PM

Hi sqlkev,

I've been having problems with peaky response too (wm60YA mic capsule). I have got some good results, but I haven't been able to get them consitently. Soldering could be an issue, I got good results after resoldering the capsule, but then it went bad again.... I think I was so worried about overheating the capsule that I didn't solder it properly...

I'm still trying to track down the problem.... I'm going to build a new preamp on one of Vikash's boards, I have the same preamp I made on an ic experimenter board, and want to make sure the problem isn't with my preamp.

Are you doing gated measurements in SW? and if so, are you setting the gate interval properly? If you don't correctly set the gate interval, then you will get very nasty freq response curves due to reflections....

here ---> http://www.akustyk.com/pomiary/hardw...%20preamp2.htmis what Eric Wallin measured on a number of WM61A's scroll down till you get to the f/r graph.

You could try downloading a generic WM61A callibration file.... I think that since the mics are good up to 5K you can confidently use it for crossover design provided you aren't crossing higher than 5K

Tony.

jbateman · 15th July 2005, 12:35 PM

Quote:

Originally posted by Padel

Hi jbateman,

Can you please tell me where can I find the generic calibration files of the WM-61A?
I'm a bit confused, the plot you posted, is the actually frequency response of the capsule or the calibration files for correction?
If these are the calibration files then the capsule should starting to roll off at about 5KHz, right?

Padel

I had my mic calibrated many years ago by Kim Girardin of Liberty Instruments. The picture is the actual frequency response of the mic.
When the mic is calibrated, you receive an FRD file, which you import into your SpeakerWorkshop project directory. Then when you open the OPTIONS/CALIBRATE tab, there is a box to browse to the mic cal file. SW then use this data to apply a correction to any acoustic measurements you make.

If you want to try my cal file, I will try to attach it as a TXT file (bateman.txt). You will have to rename it to an FRD file (anything.frd) in order to use it, though.

Padel · 15th July 2005, 01:20 PM

Hi jbateman,

Thank you very much for .frd files, unfortunately they are not compatible with the ETF 5.0 measuring software that I'm using right now. ETF accepts .cal files and I tried to rename as such with no luck.

Anyway, here is a response graph of a generic WM61A .cal file I found, I just connected the soundcards input directly to output with a short cable.

This should take care of the high frequency bump of the WM61A.

Regards
Padel

jbateman · 15th July 2005, 01:28 PM

Padel, I had confused you with the original poster in this thread, who is using Speaker Workshop.

Good luck.

Padel · 15th July 2005, 01:28 PM

...and here is the calibration file (.cal) in use renamed to .txt for allow posting!!!

Regards
Padel

sqlkev · 15th July 2005, 04:34 PM

padel:
I did not try to modify the capsule since I've read it isn't easy to do and results may vary.

wintermute:
I'll try to do the gated measurements today to see how that goes. I still have lots to learn in SW.

jbateman:
thank you for the file, I'll see if that helps out in my case.

BTW, when I solder the ground lead to the mic capsule, does it matter if the groud solder is touching the capsule's cover? I don't think it does, but just asking to be sure. I'd hate to resolder and mess it up, since I only have 1 capsule

15th July 2005, 03:17 AM	#1
sqlkev diyAudio Member Join Date: Mar 2004 Location: 714	wm-61a topend peak- calibration? or resolder?? Just got my measurement preamp kit from highefficiencyloudspeakers.com. The wm-61a pana. mic capsule seems to be very peaky from 10khz and up, is it due to my poor soldering skills? bad capsule? or is it a normal thing and I can calibrate it?? I'm still trying to figure out speakerworkshop to do simple FR for now. So far, I consistently get measurements with peaks above 10khz. Help!!!!

15th July 2005, 12:04 PM	#5
wintermute just another diyAudio Moderator Join Date: Aug 2003 Location: Sydney Blog Entries: 22	Hi sqlkev, I've been having problems with peaky response too (wm60YA mic capsule). I have got some good results, but I haven't been able to get them consitently. Soldering could be an issue, I got good results after resoldering the capsule, but then it went bad again.... I think I was so worried about overheating the capsule that I didn't solder it properly... I'm still trying to track down the problem.... I'm going to build a new preamp on one of Vikash's boards, I have the same preamp I made on an ic experimenter board, and want to make sure the problem isn't with my preamp. Are you doing gated measurements in SW? and if so, are you setting the gate interval properly? If you don't correctly set the gate interval, then you will get very nasty freq response curves due to reflections.... here ---> http://www.akustyk.com/pomiary/hardw...%20preamp2.htmis what Eric Wallin measured on a number of WM61A's scroll down till you get to the f/r graph. You could try downloading a generic WM61A callibration file.... I think that since the mics are good up to 5K you can confidently use it for crossover design provided you aren't crossing higher than 5K Tony. __________________ Any intelligence I may appear to have is purely artificial! Some of my photos

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15th July 2005, 11:46 AM	#3
jbateman diyAudio Member Join Date: Oct 2000 Location: The People's Republic of Maryland	This is the response of my WM61a mic capsule...although it's about a 5 year old model. I also have a second one, which is the same shape but about 1 dB lower at the peak.

15th July 2005, 01:28 PM	#8
jbateman diyAudio Member Join Date: Oct 2000 Location: The People's Republic of Maryland	Padel, I had confused you with the original poster in this thread, who is using Speaker Workshop. Good luck.

15th July 2005, 04:34 PM	#10
sqlkev diyAudio Member Join Date: Mar 2004 Location: 714	padel: I did not try to modify the capsule since I've read it isn't easy to do and results may vary. wintermute: I'll try to do the gated measurements today to see how that goes. I still have lots to learn in SW. jbateman: thank you for the file, I'll see if that helps out in my case. BTW, when I solder the ground lead to the mic capsule, does it matter if the groud solder is touching the capsule's cover? I don't think it does, but just asking to be sure. I'd hate to resolder and mess it up, since I only have 1 capsule

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