• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Speaker Measurement Thread

My WT2 is the original S&L purchased from PE when they were initially selling them, with software upgrades from the S&L site.... :yes:
 
OK

I have installed my speaker tester (currently does not work with win7 x64 working on that with Keith) had to install win XP ( that's a whole different story).
So quad booting WinXP, Vista, Win7 and Ubuntu and I now have it working.

Did some TS measurements of a 5 1/2" 4 ohm Jamo driver buyout from PE.

I really do not know what I am doing yet but I am sure time will help this problem.:D

I think this is my first ever, post of a response graph.:banana:

attachment.php
 
Last edited:
I dug out my RTA...

When I saw this:

Zilch said:
...
Pete B and Ken Kantor are looking at the cheap in-line phantom powered USB preamps. Pete has discovered that the one he bought doesn't have sufficient front-end attenuation to permit nearfield measurements without overloading, but that may be because he wants to maintain max S/N ratio and plays the DUT at high SPL.
...
Click to expand...

It's a Neutrik Minilyser (with companion Minirator). Came with this mic and 20db attenuator for nearfield measurements. Of course the mic has an AA battery in it, so it doesn't try to run 48VDC through the H-Pad...

Most times phantom power is fed right to the XLR via a pair of resistors, so if you need to add a pad it has to be between the XLR and the actual input amp (or transformer). I have an external 48V phantom power box with XLR in and out that would work just great in this kind of high SPL situation, just plug the pad in on the output cable...

(BTW, thanks for reminding me to take the battery out of the measurement mic, it's been in there for 3 years at least, I was worried about it leaking, but couldn't figure out how to get it out last time I was using the RTA, found the little push-button this time!)
 

Attachments

  • NTI_Mic&pad.jpg
    NTI_Mic&pad.jpg
    30.9 KB · Views: 24
Last edited:
4343 said:
When I saw this:



It's a Neutrik Minilyser (with companion Minirator). Came with this mic and 20db attenuator for nearfield measurements. Of course the mic has an AA battery in it, so it doesn't try to run 48VDC through the H-Pad...

Most times phantom power is fed right to the XLR via a pair of resistors, so if you need to add a pad it has to be between the XLR and the actual input amp (or transformer). I have an external 48V phantom power box with XLR in and out that would work just great in this kind of high SPL situation, just plug the pad in on the output cable...

(BTW, thanks for reminding me to take the battery out of the measurement mic, it's been in there for 3 years at least, I was worried about it leaking, but couldn't figure out how to get it out last time I was using the RTA, found the little push-button this time!)
Click to expand...

Cool!!

Post some pics of your measurements please!!:thmbsp:
 
Hey, I've been wanting to ask another Minilyzer owner:

My ML1 has a strange glitch in its voltmeter amplitude response right around 315 Hz. Not a huge deviation, but noticeable. It's ruler flat just above, and just below, that frequency. It does this at all signal levels, very consistently. Checked it against various reference meters, etc.

Does yours show anything weird there?

-k



4343 said:
When I saw this:

It's a Neutrik Minilyser (with companion Minirator). Came with this mic and 20db attenuator for nearfield measurements. Of course the mic has an AA battery in it, so it doesn't try to run 48VDC through the H-Pad...

Most times phantom power is fed right to the XLR via a pair of resistors, so if you need to add a pad it has to be between the XLR and the actual input amp (or transformer). I have an external 48V phantom power box with XLR in and out that would work just great in this kind of high SPL situation, just plug the pad in on the output cable...

(BTW, thanks for reminding me to take the battery out of the measurement mic, it's been in there for 3 years at least, I was worried about it leaking, but couldn't figure out how to get it out last time I was using the RTA, found the little push-button this time!)
Click to expand...
 
Zilch said:
Pete B and Ken Kantor are looking at the cheap in-line phantom powered USB preamps. Pete has discovered that the one he bought doesn't have sufficient front-end attenuation to permit nearfield measurements without overloading, but that may be because he wants to maintain max S/N ratio and plays the DUT at high SPL.
Click to expand...

It was Ken who first pointed out the near field issues where the MIC-MATE distorted at high SPLs.

I actually, just recently, did some near field testing with the ECM8000 going into line in on an M-Audio Transit and found that there was clipping at very high levels. I believe that this was in the ECM8000 since the line in should have high headroom, but did not have time to check. I was running 200W into a 12" sub and wanted to check the speaker's max SPL distortion. I was able to just pull the mic away and see the clipping go away.

I'm seeing low freq noise with an ECM8000 that is about 50 dBA
which seems way too high. Anyone have the typical ECM8000
noise spectrum as measured with good lab equipment? I have to
look into this more when I have the time.
 
Last edited:
Pete B said:
I was running 200W into a 12" sub and wanted to check the speaker's max SPL distortion. I was able to just pull the mic away and see the clipping go away.
Click to expand...
I believe 120 dB is the max for any of the common ones; if you're measuring jet engines, high SPL mics are available for a substantial upcharge. ;)

Pete B said:
Anyone tried this, it is low cost and has phantom power.
Click to expand...
On order, Pete.... :thmbsp:
 
Last edited:
Zilch said:
I believe 120 dB is the max for any of the common ones; if you're measuring jet engines, high SPL mics are available for a substantial upcharge. ;)

On order, Pete.... :thmbsp:
Click to expand...

These mics are probably very similar to the popular Panasonic - interesting that Linkwitz's mod brings the MaxSPL to 141 dB for a 5 Vpp output! But yes these are probably limited to about 120 dB.

Linkwitz also mentions a noise level of 30 dBA SPL:
http://www.linkwitzlab.com/sys_test.htm
The calibration report for my ECM8000 indicates a noise level of 36 dBA which is in the ball park. Linkwitz mentions that his measurement is above 80 Hz and that there is 1/f noise below - this probably partly explains what I am seeing but not the fact that the rise starts below about 1K in my setup.
 
Looked into the LF noise a bit more, waited for the forced hot air heat to stop and the refrigerator to cycle off.

Now the rise starts at about 200 Hz, where the worst case LF noise between about 10 and 50 Hz bounces around averaging 15 to 20 dB higher than midband with short term random peaks to about 25 dB higher. This is probably mostly flicker or Johnson noise from the electret but I'm not very familiar with noise in electret mics so I welcome comments from microphone experts.

There was a 60 Hz component about 30 dB above the midband noise level, but when I listen to the noise spectra I could not hear it. It seemed to come from the rush of the forced hot air and went away when it shut off.
 
I went back to the MXL MIC-MATE:
http://www.bhphotovideo.com/c/product/522285-REG/MXL_MICMATE_BASIC_USB_Mic_Mate_.html

And, as expected it does not seem to contribute significant noise, about the same as with the M-Audio Transit.

I used my 114dB calibrator to check if the MXL clipped at this level and it did with the gain switch set to high, but not with it set to low. Switch is about 5dB/step.

The MXL MIC-MATE provides phantom power and seems to work fine for my intended portable application using a Laptop. Probably not a good choice if you need to do near field high SPL testing unless you use an attenuator and a source for phantom power.
 
I'll tell ya, reading some of those ECM8000 links remind me of what an OCD crowd audio techies are!

Anyway, my serious comment here is to point out that many mics have an overload characteristic that varies with both the input impedance of the preamp and the phantom power voltage/ESR. Many of the USB-powered pres are not quite up to snuff in these regards. Could be that the MXL has a wimpy phantom supply, and so the mic is clipping prematurely and/or is noisy.

I did a mic pre design last month for one of our upcoming products. You know the drill: tiny budget, bullet proof, must work happily and quietly with whatever gets plugged in. etc. Real world. So, I had to test it with dozens of mics. Wound up running the phantom voltage lower than spec, and dropping the phantom Rs a bit, too. The circuit works with almost everything in my mic locker, but dies on some notorious models. Old Earthworks TC40K. AT4050/CM5. AKG C414B-XLS. Fortunately, these are not mics are going to be found in the coffeehouse and bar gigs the product is for....

-k
 
Thanks for the input Ken. My speaker tester came with the ECM 8000 but i also have a DBX (for the driveracks) and a BESL made test mic (i think it is the Panasonic capsule) but have a comp file for it. Not sure what would be the best one to use:scratch2:
 
ken kantor said:
I'll tell ya, reading some of those ECM8000 links remind me of what an OCD crowd audio techies are!
Click to expand...

Not all of 'em! :D I took one of those goofy online quizzes that tell how "Type A" you are on a scale of 1-100. I scored 17. Where's my hammock?
 
You must log in or register to reply here.
Back
Top Bottom