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Discussion Starter · #1 ·
Okay, I finally had a chance to do some measurements using my Dayton EMM-6 and ART USB Dual Pre setup after removing a wall of mirrors and painting my room. I'm surprised at how different the graphs look than the previous ones I took using my RS SPL meter and PC soundcard - but that's not the point here... ;)

I took readings with my sub in 2 different positions. In these graphs my test signal is plugged into the front left channel analog input on my HK AVR3600 with it set to 2 channel stereo mode and a crossover for the sub set at 80hz. I realized that one graph goes from 15hz and the other goes from 0 - I apologize in advance for that, I can't edit that right now since the measurement file is on my laptop and I am not.



and



I am looking strictly at the frequencies from 15-80hz so I can do some subwoofer managing with a DSP1124P.
To my amateur eye, the second one looks much more manageable using filters to level things out.

2 questions pop up though:
1) Why am I getting such a large peak from 80-120 if my sub is supposed to be crossed over at 80hz? It looks like it is not crossing over at 80hz like it is supposed to. Should I maybe re-run the test with the front left speaker disconnected to make sure I'm actually crossing where I should be so the measurements are accurate?

2) Assuming this graph is an accurate representation where the test tone was at 80dB before the testing - would 80dB be the appropriate level to set my filters to? To me that seems to me a logical level, just want to make sure I'm on the right track.
 

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To my amateur eye, the second one looks much more manageable using filters to level things out.

2 questions pop up though:
1) Why am I getting such a large peak from 80-120 if my sub is supposed to be crossed over at 80hz? It looks like it is not crossing over at 80hz like it is supposed to. Should I maybe re-run the test with the front left speaker disconnected to make sure I'm actually crossing where I should be so the measurements are accurate?

2) Assuming this graph is an accurate representation where the test tone was at 80dB before the testing - would 80dB be the appropriate level to set my filters to? To me that seems to me a logical level, just want to make sure I'm on the right track.
The second one is better higher up but you appear to be creating a null in the sub 20 Hz area. ( Or is that just because your two graphs are different ranges)
I would try and find another location if you are going to be using it for LFE in movies.

As for the peak at 80-120 Hz does your sub have a variable cutoff or is it solely relying on your amplifier?
 

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Discussion Starter · #3 ·
robbo266317 said:
The second one is better higher up but you appear to be creating a null in the sub 20 Hz area. ( Or is that just because your two graphs are different ranges)
I would try and find another location if you are going to be using it for LFE in movies.

As for the peak at 80-120 Hz does your sub have a variable cutoff or is it solely relying on your amplifier?
Thanks for the input.
The difference below 20 is because I goofed up on the graph ranges - the sub is only rated to 18hz so I'm not expecting to see much below 20. I should redo those images so they match better ;)

The sun does have its own crossover as well, but when I did the sweeps I had it turned all the way up and was just relying on the crossover on the AVR.
 

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I am looking strictly at the frequencies from 15-80hz so I can do some subwoofer managing with a DSP1124P.
To my amateur eye, the second one looks much more manageable using filters to level things out.
Not really. The second one doesn’t have the severe null that the first does, but you have a full 20 dB span between the worst peak and depression. That’s more than can be reasonably equalized, unless you have tons of headroom. Are there any other locations available, either for the sub or listening position?

Regards,
Wayne
 

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Discussion Starter · #7 ·
No to both... unfortunately.

I'm not sure what you mean by the headroom comment - but I am running the sub with the AVR sub level around -6 and the sub amp is at about 1/4-1/3. So I have room to bump up the overall sound level after doing some peak cutting if that I what you meant.

I had REW create filters for me and they seemed pretty reasonable, bringing the peaks down to about the 80dB line... but I have not yet level matched the sub and tried rerunning a sweep to see what it did for me.
 

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I'm not sure what you mean by the headroom comment.
Any equalization places additional demands on the sub, both the driver and amplifier – i.e. reduces headroom. The more severely you equalize (boost or cuts, doesn’t matter), the more the loss of headroom. Of course, how much this is a problem (if at all) depends on the capability of your sub. You can read a little about that here .


Wayne - this is the graph with my filters applied... does it look reasonable?
No, you’re essentially using the equalizer as a defacto volume control when you drag everything down to the level of the depression. Locate the Target midway between the worse peak and depression. :T

Regards,
Wayne
 

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Discussion Starter · #11 ·
Just to explain my thought process - so maybe I can see where I went wrong here - I had run the AVR built in manual calibration just before this and set the subwoofer to 80dB, and when I calibrated the SPL metering was also at 80dB. I thought it made sense then to set my target level on the filters to 80dB - which is why it ended up looking like this.

For the record - it does sound pretty good while just watching Deadliest Catch on digital cable (not even close to a good test) with that filter set active.
I will redo I for a higher range and smaller cuts tomorrow night. Thanks again for your help.
 

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Discussion Starter · #12 ·
I went ahead and applied the filters and ran a couple of tests just to see...
To start with I re-adjusted my speakers to be level matched with the filter on, and it actually ended up with the sub level lower than where it used to be because of the corner placement gaining me a LOT more SPL than expected.

Anyway - here is the graph:


So... it looks like it did an OK job... but I also learned that apparently my AVR is NOT crossing over the sub properly! I ran a sweep with the front speaker disconnected and this is what I got:


I don't know what to do there other than maybe using the crossover control on the sub... but that is a topic for a different thread I guess.
 
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