Bought a used UMIK - now concerned about possible under-measurement of bass

[aanon]

Hi all,

I've recently jumped into room measurement and am looking for some guidance regarding initial results.

I use Acoustic Research AR9 speakers (the original model) in a 115 m³ space (converted garage). They are in good condition, all drivers correct type and working, up against a solid front wall as per recommended placement.

I bought a used UMIK-1 and have begun measuring with both REW and Dirac. I was shocked to find that measurement results in a position I found subjectively very nice came out with quite a huge apparent lack of energy in the bottom end. And not just a dip or a rolloff near 20-30Hz, but a strong general tilt downwards starting as high as 500-600Hz.

For reference, this is the approximate positioning information for the above measurements and the simulated response.

I have spent the last two days measuring in all kinds of locations around the room, moving speakers to many different locations, and yet the general picture hasn't changed much at all. Always a massive shortfall in the lower end. Have also tried two different amplifiers, two different computers, two different audio sources (laptop output and Benchmark DAC1). Both direct measurement and 90-degree measurement have been tried (using the corresponding calibration files in each case).

When I did a Dirac Live measurement/correction (this was in a slightly different location), the measured curve showed the same general shape.

The resulting Dirac "correction" made the audio in my room sound like I was listening underwater - i.e. all the higher frequencies were severely attenuated, leaving only muddy bass sounds.

All this leads me to believe that there is actually more bass end in the room than REW or Dirac are seeing from the UMIK input. It's making me wonder whether the UMIK itself might have an issue.

I looked closely at the mic and noticed the membrane appears like it's been pressed in in some places.

A question to the experienced room measurement people here: does this seem likely to be a microphone issue to you? I can return the UMIK to the seller but I want to be fair and rule out user error/misunderstanding before I take that step.

Many thanks for any advice you can offer.

Aanon

 

[aanon]

Update: I got the idea to measure a sweep with my SONY PCM-M10 recorder and import this into REW for analysis against the original sweep file. Results indicate, I think, that there actually is plenty of low end at the measurement position.

 

[lovinthehd]

I don't think I saw mention of uploading the calibration file with the mic or using it with the software?

 

[aanon]

I don't think I saw mention of uploading the calibration file with the mic or using it with the software?

Thanks for taking the time to consider this. Yes, calibration files have been downloaded and used in both REW and Dirac, and I have tried both direct and 90 degree measurement angles without much difference in outcome.

 

[panteragstk]

Thanks for taking the time to consider this. Yes, calibration files have been downloaded and used in both REW and Dirac, and I have tried both direct and 90 degree measurement angles without much difference in outcome.

It sucks, but you're going to have to try another mic. If all the calibration stuff is there then somethings not working properly. Do you have another USB cable?

 

[lovinthehd]

Thanks for taking the time to consider this. Yes, calibration files have been downloaded and used in both REW and Dirac, and I have tried both direct and 90 degree measurement angles without much difference in outcome.

Had to ask. I take it audibly you don't notice the shortfall so I'd suspect the mic too at this point, and the appearance isn't encouraging (did you violate warranty by taking it apart, tho?)....just who did you buy it from? miniDSP or someone else?

 

[aanon]

Thanks to all responders.

I've decided to return the mic to the (eBay) seller. I recorded sweeps with another device and found there was plenty of bass in the room (confirming what my ears perceived). The room correction based on measurements from that other device sounded very good. Also, miniDSP looked at the picture of the mic diaphram and they stated it is definitely not normal and would be affecting the measurements.

It's a bummer because I wanted to get fully into using the UMIK straight away, but I guess I'll just have to be patient for now. I have ordered another UMIK new from the manufacturer.

Aanon

 

[lovinthehd]

Thanks to all responders.

I've decided to return the mic to the (eBay) seller. I recorded sweeps with another device and found there was plenty of bass in the room (confirming what my ears perceived). The room correction based on measurements from that other device sounded very good. Also, miniDSP looked at the picture of the mic diaphram and they stated it is definitely not normal and would be affecting the measurements.

It's a bummer because I wanted to get fully into using the UMIK straight away, but I guess I'll just have to be patient for now. I have ordered another UMIK new from the manufacturer.

Aanon

Just buy one from minidsp or maybe Cross-spectrum....