Assistance with Pre-EQ Graphs

STucker · Nov 11, 2024

Hello - I am new to the AV NIRVANA forums. I have been using REW for about 3 weeks now and watching several videos on setup, configuration, etc...
I have the latest generally available version of REW running on a Windows 11 laptop. I have a UMIK-1 microphone with the downloaded calibration file and a miniDSP 2x4 HD connected to dual Rythmik Audio FVX15 subs. I am attaching 3 graphs: 1 - left sub, 2 - right sub, 3 - both subs. I have tried several things to affect the null between 72-77 hz, but nothing has worked. I am asking the following:

I have heard conflicting information on the DB level above the noise floor. Should I stay with 75DB as a target and ignore the room floor noise (about 41 DB in my room) or do I add 40 DB to the noise floor?
Do I need to add gain to the UMIK-1 for Windows 11 - the gain for Windows 10 is 18?
You can see from the dual sub graph, I have significant peaks. Will EQ fix these peaks or are the other options I need to consider?
I have some spare thick sound absorption panels I moved to several places in my room and there was little to no improvement with the 72-77 HZ null. What are the options to eliminate this null?
Lastly, I have an unusual room shape with knee walls on both side walls, but opening to floor to ceiling on the left side of the room about 10 feet from the front of the wall.

I appreciate any coaching the REW community can offer to a new comer.

Wayne A. Pflughaupt · Nov 11, 2024

I have heard conflicting information on the DB level above the noise floor. Should I stay with 75DB as a target and ignore the room floor noise (about 41 DB in my room) or do I add 40 DB to the noise floor?

The measurement level only has to be a good bit above the noise floor. 75 dB is more than enough in your room. There’s no reason to add another40 dB unless you want to smoke your subs.

You can see from the dual sub graph, I have significant peaks. Will EQ fix these peaks or are the other options I need to consider?

EQ can fix the peaks. Your left graph actually looks pretty good, but the right sub is the problem. EQ can’t fix nulls as bad as that. You should try moving the right one to another location. If that’s not possible, the put them both where the left sub is.

I have some spare thick sound absorption panels I moved to several places in my room and there was little to no improvement with the 72-77 HZ null. What are the options to eliminate this null?

Sound absorption only reduces reverberation or echo in the room – I.e. makes the room more “dead.” Bass traps are the only acoustical treatments that can potentially reduce nulls.

Regards,
Wayne

STucker · Nov 11, 2024

Wayne A. Pflughaupt said:
The measurement level only has to be a good bit above the noise floor. 75 dB is more than enough in your room. There’s no reason to add another40 dB unless you want to smoke your subs.

EQ can fix the peaks. Your left graph actually looks pretty good, but the right sub is the problem. EQ can’t fix nulls as bad as that. You should try moving the right one to another location. If that’s not possible, the put them both where the left sub is.

Sound absorption only reduces reverberation or echo in the room – I.e. makes the room more “dead.” Bass traps are the only acoustical treatments that can potentially reduce nulls.

Regards,
Wayne

Wayne - thank you for the prompt response and excellent feedback. I tried the right sub in several places on the right side of the room and it did not improve. Putting it on the left right beside the left sub produced good results as indicated in the attached dual sub graph.

I have a few follow-up questions please:

Since I plan to crossover at 80HZ, do I need to be concerned with the null between 113 -123HZ?
I am hitting my 75DB target between about 70-76HZ and all other frequencies are at least 5DB or higher than 75. Will EQ filters be able to take down these peaks to the 75DB range?
So I don't get to about these measurements, what is a reasonable +/- DB range off the target of 75 I should aspire to achieve?

Thanks again for the assist.
Steve

Wayne A. Pflughaupt · Nov 11, 2024

Since I plan to crossover at 80HZ, do I need to be concerned with the null between 113 -123HZ?

No. When you add the main speakers to the measurement, there’s a good chance it will disappear

I am hitting my 75DB target between about 70-76HZ and all other frequencies are at least 5DB or higher than 75. Will EQ filters be able to take down these peaks to the 75DB range?

What you want is a sloped curve, not flat. Your measurement is nicely getting you there for free - see the picture below. A single filter at ~45 Hz cut about 8-10 dB with a 1/(2 octave bandwidth (2.9 Q) should be all you need. Don’t try to get a straight-line graph. A few dB above or below the target won’t be audible. Adjust the filter bandwidth so that the outlier frequencies at the ends of the orange line stay where they are presently. If they move down, the filter is too broad.

Likewise, the null at 72 Hz shouldn’t be a problem. I’ve had nulls far worse than that which were inaudible. Besides, there’s a good chance the mains will blow the null out when they’re added, since it’s so close to the crossover frequency.

You might want to check my articles on house curve and minimal EQ posted on another forum – find the latter searching “minimal EQ” along with my name.

So I don't get to about these measurements, what is a reasonable +/- DB range off the target of 75 I should aspire to achieve?

Can’t help you there. Personally, I don’t use a target. I EQ to smooth out response, then adjust the sub level by ear to blend with the main speakers. However, the answer above to the second quote should suffice.

Regards,
Wayne

STucker · Nov 15, 2024

Hello Again,

I have a followup question to my question from a previous post: "Since I plan to crossover at 80HZ, do I need to be concerned with the null between 113 -123HZ?"

And this response to the question above: "No. When you add the main speakers to the measurement, there’s a good chance it will disappear"

I am not clear on how to add the left / right / center speakers to my REW sub measurements to see the final results of any improvements to the nulls between 70 - 80 HZ and 113 - 123 HZ. Does enabling the L+R option in the measurements drop down add the Left / Right front speakers? If not, how do I add them to the measurement?

Also, is there an option to add all three front speakers along with the subs to the REW measurement?

Thanks in advance for your reponse.
Steve

Wayne A. Pflughaupt · Nov 15, 2024

STucker said:
Also, is there an option to add all three front speakers along with the subs to the REW measurement?

Set REW for a full range measurement (10Hz – 20 kHz) and measure with both the L/R and sub operating. Alternately, you can measure left + sub, or right + sub.

Regards,
Wayne

Assistance with Pre-EQ Graphs

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