Significant drop in less than 100hz

[Ofer]

I have upgraded to the MiniDsp 4x10hd. Did a few measurements of each driver at 1 meter and added the PEQ to the output channel. That worked great. The response at the woofers that are crossed at 500hz was improved. When I measure at the listening position I see a significant drop in the area under 100hz that I don't see at the measurement at 1m. The listening position is 4m from the speaker. Attached are pictures from the right speaker. What could be the cause of such a dramatic drop? How could I solve this?

 

[DanDan]

Looks like the Listening position is not good for that Sub Location. Move either or both.

 

[Ofer]

Moving the woofers is not going to be easy, ~60kg each, I will try different listening positions. I tried playing with the room modulator in REW but can't really understand the results.

 

[JStewart]

@DanDan , is it possible to have 20dB attenuation at 3m (increased) distance naturally?

 

[DanDan]

Unlikely, something has to change and locations are on the table. Note that they are swappable. You could place one sub at your listening position, move the mic around to find the new optimum location. Pink Noise and the RTA/Spectrum will help do this quickly.

 

[Ofer]

Hi Dan,

Thanks for your help. This is a 3 way speaker. The woofers are very heavy and the mid twitter is on top of them. Woofer+mid twitter weighs about 90kg. How do I go about using Pink noise and RTA/spectrum?

 

[John Mulcahy]

Use the signal generator to play full range pink periodic noise and watch the response on the RTA with these settings:

 

[JStewart]

Maybe my lack of knowledge/understanding, but it sure looks possible that something changed in the in the miniDsp or elsewhere in the measurement system between measurements.
Comparing the two measurements in the op they remain approx level matched between 150-600Hz, but in the listening position measurement the level drops about 20dB over the span of approximately 1 octave and then remains a somewhat consistent 20dB below the 1meter measurement from about 80Hz to 15Hz. If it’s a room effect, that room is one heck of a consistent filter.

 

[Ofer]

Use the signal generator to play full range pink periodic noise and watch the response on the RTA with these settings:

View attachment 41891

OK. But what would be a "good" response and a "bad" response? How should I interpret the RTA response?

 

[Ofer]

Maybe my lack of knowledge/understanding, but it sure looks possible that something changed in the in the miniDsp or elsewhere in the measurement system between measurements.
Comparing the two measurements in the op they remain approx level matched between 150-600Hz, but in the listening position measurement the level drops about 20dB over the span of approximately 1 octave and then remains a somewhat consistent 20dB below the 1meter measurement from about 80Hz to 15Hz. If it’s a room effect, that room is one heck of a consistent filter.

OK. So I decided to test this. I have measured the right base from 1m. Indeed as you can see in the figure the base now shows the same drop in less than 100Hz. This is true after removing all PEQ from both input and output. Now I am at a loss as to what causes this. Any help would be greatly appreciated

.

 

[JStewart]

Just to be clear, the red and green traces are of the very same SINGLE driver, both taken at 1M distance, on different dates. Is that correct?

You have a set of these. What is the response of the other in comparison?

 

[Ofer]

Just to be clear, the red and green traces are of the very same SINGLE driver, both taken at 1M distance, on different dates. Is that correct?

You have a set of these. What is the response of the other in comparison?

Thank you for your reply and help. Short answer, yes. It is a measurement of a single driver at 1m distance on different dates. It gets even more interesting. After measuring the right woffer driver I disconnected the cables and went back to using the unit, but the remote wouldn't work. The only solution was to power cycle the unit. The next day I measured the left woffer at 1m as JStewart suggested. The measurement of the other driver is below. As you can see, it is has no drop. So I decided to measure the right woofer at 1m again. To my surprise the drop below 100hz was gone. The only difference is the power cycle.

Is anyone familiar with this issue in the MiniDSP 4x10HD unit?

 

[JStewart]

OK that's weird. Glad its working now though.
I use a 2x4HD and never seen anything like that on it.

 

[Cheetodust]

Actually I am having a similar issue with the 2x4HD and I cannot figure out what is happening to cause it. This is two GSG Audio BTS 21" subs with LaVoce SAN214.50 21". Using Behringer NX6000. It looks very similar to Ofer's measurement.

 

[Ofer]

I'll ask the obvious questions. Did the subs measure differently before? Did you try to power cycle the unit?

 

[JStewart]

Also switching configs on the MiniDSP might tell you something as well.

 

[Cheetodust]

They have never measured correctly but thought it was my old sub. So when I bought my new ones and the reading looked the same, I new something had to be wrong. I actually think I have found the answer today. The guys from AZ Tuning suggested going into the advanced settings of the microphone on my laptop and disabling "Enable Enhanced Audio". Once I did I ended up with a very workable graph. Here is what it looks like after disabling. I have a high pass set at 14 Hz BTW.

 

[Ofer]

What microphone are you using?

 

[Cheetodust]

UMIK-1

 

[Ofer]

They have never measured correctly but thought it was my old sub. So when I bought my new ones and the reading looked the same, I new something had to be wrong. I actually think I have found the answer today. The guys from AZ Tuning suggested going into the advanced settings of the microphone on my laptop and disabling "Enable Enhanced Audio". Once I did I ended up with a very workable graph. Here is what it looks like after disabling. I have a high pass set at 14 Hz BTW.
View attachment 42116

Was that on W10? How did you do it? Can't seem to find the right settings.

 

[Cheetodust]

This is how I get there on Windows 10. Go to SETTINGS then SYSTEM then SOUND then down to INPUT then DEVICE PROPERTIES then ADDITIONAL DEVICE PROPERTIES then the ADVANCED tab then down to ENABLE AUDIO ENHANCEMENTS and uncheck to disable it. Hope this helps!

 

[Ofer]

For some reason I don't have the ENABLE AUDIO ENHANCEMENTS option on my laptop. Will have to dig deeper into it.