Measurement microphone specs and distance needed for measuring speaker distortion

[Mr. Haelscheir]

Some nice stuff was learned, but this thread was born of my wanting to do my own measurements of the KEF LS60 amid my dreaming of acquiring such for the living room, but let's say I have rather a "Mom Approval Factor" to contend with even if it's my own money, and blasting symphonic peaks at 100 dB probably isn't acceptable in this household. So the plan is to stick to dual Genelec 8341As plus the GLM kit, partly using such to produce an HRTF measurement for Earfish and finally get a proper in-ear speaker reference for headtracked headphone EQ.

 

[Blumlein 88]

While I'm doing this, a Lewitt LCT 540 (original version) in cardioid.

 

[Blumlein 88]

Some nice stuff was learned, but this thread was born of my wanting to do my own measurements of the KEF LS60 amid my dreaming of acquiring such for the living room, but let's say I have rather a "Mom Approval Factor" to contend with even if it's my own money, and blasting symphonic peaks at 100 dB probably isn't acceptable in this household. So the plan is to stick to dual Genelec 8341As plus the GLM kit, partly using such to produce an HRTF measurement for Earfish and finally get a proper in-ear speaker reference for headtracked headphone EQ.

Okay, then nevermind.

 

[pma]

Thought I would post some simple distortion measures. One speaker. First is the Umik 1. Don't worry about the bad THD+N numbers. Trains, and planes and air conditioners kept interfering. I think it only effected the low end.


Finally, a CAD M179 in omni mode.

View attachment 308692

In case your wondering I did all of these at least 3 times and a couple 4 or 5 due to noise issues in the low end. Other than the low end each run produced the same results to within 1 or 2 in the 2nd digit past the decimal place for each harmonic.

Your place must be really quite noisy, or, it all comes from the USB interface?

I am getting results like this at my place (580 mm measuring distance):

 

[Sokel]

Your place must be really quite noisy, or, it all comes from the USB interface?

I am getting results like this at my place (580 mm measuring distance):

View attachment 309126

Tried same settings (only mine is 20-20000Hz), same distance to practice:

 

[Blumlein 88]

I mentioned it was trains, planes and air conditioners. Trains were coming by every few minutes and low frequencies were elevated until they were miles away. Then a couple of planes were rather low and loud for a few minutes. Plus it was still hot with AC units running near continuously. So yes, at the time I did those it was rather loud.

 

[Sokel]

I mentioned it was trains, planes and air conditioners. Trains were coming by every few minutes and low frequencies were elevated until they were miles away. Then a couple of planes were rather low and loud for a few minutes. Plus it was still hot with AC units running near continuously. So yes, at the time I did those it was rather loud.

It's difficult that's for sure,low's were dancing all over the place for me,specially this 30Hz one (which I can't even hear down there )

 

[fineMen]

It's difficult that's for sure,low's were dancing all over the place for me,specially this 30Hz one (which I can't even hear down there )

The o/p is already missing in this conversation. Maybe he has come to revise his requirements based on corrected calculations, taking the actual measuring algorithm(s) into account, including the underlying, not always trivial, mathematics. He might follow the suggestion to start out with a cheap(er) microphone first in order to get used to its use. We can only hope that he will come back to this once he concluded on how to proceed. I would book that as a personal success for the genral good of it.

 

[Mr. Haelscheir]

The o/p is already missing in this conversation. Maybe he has come to revise his requirements based on corrected calculations, taking the actual measuring algorithm(s) into account, including the underlying, not always trivial, mathematics. He might follow the suggestion to start out with a cheap(er) microphone first in order to get used to its use. We can only hope that he will come back to this once he concluded on how to proceed. I would book that as a personal success for the genral good of it.

For now, despite my original ambitions, I don't see myself entering the distortion measurements game anytime soon. https://audiosciencereview.com/foru...60-wireless-just-announced.33705/post-1287310 already sated some curiosity, whereby I suppose one can't expect the DSP to have enabled Reference series distortion performance (it at least seems to be primarily second order). I also hoped to get better distortion data on the MartinLogan ESL X or Classic 9, but I doubt that a local shop would let you take such measurements even if you actually intend to buy one of the speakers you are comparing. Now knowing that Genelecs may practically speaking be the only speakers I will ever own in this household, with there already being plenty of data on them, there is no more incentive to seek my own measurements. But let this thread be informative to others seeking to conduct these measurements.

As for "cheaper microphone", for now, that will be the Genelec 8300A.

 

[Groovemandel]

Hi, I would like to know if it’s possible to measure the distortion of my KEF speakers using a UMIK 1 mic?

I have no experience in measuring anything before.

I feel the uniq on mine is grainy at low volumes but sounds fine when the volume is increased.

 

[staticV3]

Hi, I would like to know if it’s possible to measure the distortion of my KEF speakers using a UMIK 1 mic?

Possible, but not easy and not with very good results.
The UMIK-1 has very high self-noise, so it's really mostly good for frequency response measurements.

To measure THD accurately, you'd need to play your KEFs very loud, get really close with the UMIK-1, or use tricks like Coherent Averaging and high FFT length to combat the mic's noise.

 

[Groovemandel]

Possible, but not easy and not with very good results.
The UMIK-1 has very high self-noise, so it's really mostly good for frequency response measurements.

To measure THD accurately, you'd need to play your KEFs very loud, get really close with the UMIK-1, or use tricks like Coherent Averaging and high FFT length to combat the mic's noise.

Thanks for the reply. I guess it’s not usable in my case as I feel it sounds very clean when increasing the volume, but somehow is grainy at lower levels. Any idea if there is any way to do this?

 

[staticV3]

Any idea if there is any way to do this?

Do what exactly?

 

[Sokel]

Thanks for the reply. I guess it’s not usable in my case as I feel it sounds very clean when increasing the volume, but somehow is grainy at lower levels.

That sounds like a bad connection or a crappy pot somewhere the chain.

 

[Groovemandel]

That sounds like a bad connection or a crappy pot somewhere the chain.

I will look for it. Hope the midranges are not defective. The UNIQs are very expensive difficult to replace on the References

 

[Groovemandel]

Do what exactly?

Measure distortion at low loudness levels.