Deep and narrow frequency null around 90hz - shall I be concerned?

[lamberticus]

First time poster (long time lurker) and trying to figure out if this room null is fixable and how much I should worry about it. Based on the below results in the Audyssey Multi-EQ app, I ran a 90hz test tone and it was very obvious some locations in the room have much higher and lower loudnesses. I have my Sierra-LX's currently crossed at 60hz, so the sub probably isn't helping to smooth this too much.

EQ-able? Other thoughts? Thanks!

 

[pjn]

The dreaded room modes - incredibly hard to get rid of, although you may be able to reduce them a bit by moving the spekers or your seat around.
I like to use room modes to show people the problems I have to deal with... Their eyes roll up in their heads and they change the subject.

It's physics... Possibly also reducible by placing bass traps in corners, but this will only drob the modes by a few db. The corrected profile isn't too bad, IMHO

 

[DVDdoug]

Yeah, you can't do a lot (electronically or digitally) where the standing waves are canceling. (+6dB is 4 times the power, etc., and you end-up driving your amp or speakers into distortion. You CAN knock-down the bumps.

...Moving the speakers may help or it may just move the dips & bumps around in frequency and space.

Multiple subwoofers can smooth things out, but of course only if the irregularities are in the subwoofers' range.

Bass traps might help too (if you want to go that far). By absorbing the reflected waves they can smooth-out the bumps and the dips.

 

[Audio Science Pal]

if this room null is fixable and how much I should worry about it.

Your condition is very common, just because walls create standing waves. As mentioned above, try to re-position your speakers and/or the listening position, if possible. Next step would be some room acoustic treatment. EQ compensation will cause your system to use more amplifier watts and make the speakers work harder.

 

[Audio Science Pal]

EQ compensation will cause your system to use more amplifier watts and make the speakers work harder.

And still might not fix a null.

 

[Andysu]

i think i have idea for the null , shall be top secret project i do some tests and see what REW show

 

[theREALdotnet]

Are there any walls/floors nearby that could cause extinction? Like, 95cm-1.05m from the right woofer cone and 90cm-1m from the left woofer cone?

Do the nulls move when you shift the speakers to change those distances?

EDIT: If it were room modes the null would be at the same frequency for both speakers. Hence my guess of SBIR.

 

[thewas]

Such SBIR nulls are unfortunately very common and unfortunate in that region as they take away quite some of the fun of music, since you are using subwoofer(s) which have often more freedom of placement you are more flexible to cope with them, so you could try a higher crossover frequency.

 

[CapMan]

since you are using subwoofer(s) which have often more freedom of placement you are more flexible to cope with them, so you could try a higher crossover frequency.

I used 120Hz with my previous arrangement to help fill in a similar dip. Worked well. I used two smaller subs to minimise the effect of localisation with the higher XO.

 

[pjn]

In principle, you can crossover to the subwoofer quite high - this is a useful thread https://audiosciencereview.com/forum/index.php?threads/what-frequencies-are-omnidirectional.22512/

It is worth trying various crossover frequencies as well as moving the sub(s) around. It is a lot of work, but quite fun - you end up (or at least I did) spending a ridiculous amount of time doing this and then going "I wonder if..." and repeating the whole process. Months of entertainment.
If you share the space with someone, you may end up with some complaints - "can you do that when I'm put of the house?"

The bottom line, of course, is what sounds good to you. The process will be a good learning experience.

 

[sfiruch]

SBIR is difficult to solve. Fortunately, narrow nulls are not that obvious, due to psychoacoustics. I would just ignore it, and instead reduce the 50 Hz bump. And most other bumps in the lower frequencies. If you want to work on it, there are many options:

• Move your speakers and subs around. The SBIR null depends on the distance of the speaker/sub to the walls/ceilings/floor. Move speakers closer to the walls (increases the frequency of the gap) or away from the walls (where subs can fill in)
• Increase the crossover frequency, to let subs fill in the null
• Dirac ART with multiple subs
• Trinnov Optimizer with a LOT of subs
• Use multiple subs, and optimize manually (difficult)
• Purchase and install a TRUCKLOAD of passive bass traps
• Buy some active bass absorbers

TL;DR - Either ignore it, move speakers, increase crossover or buy Dirac ART.

 

[theREALdotnet]

TL;DR - Either ignore it, move speakers, increase crossover or buy Dirac ART.

Or Dirac DLBC (is ART even a thing yet, outside of a few AVR models?).

 

[Neuro]

I doubt this small frequency dip is audible for neurophysiological reasons. The inner hair cells have significant frequency overlap especially at high sound pressures and low frequencies.
If it was a peak with the same sound pressure difference at a higher frequency, maybe it would be audible.
Actually, we don't hear exactly like a microphone.

 

[theREALdotnet]

I doubt this small frequency dip is audible for neurophysiological reasons. The inner hair cells have significant frequency overlap especially at high sound pressures and low frequencies.
If it was a peak with the same sound pressure difference at a higher frequency, maybe it would be audible.
Actually, we don't hear exactly like a microphone.

I find that ERB or psychoacoustic smoothing in REW reduces anxiety a lot

 

[lamberticus]

Thanks all for your thoughtful responses. I think I may start playing around with positioning and getting a measurement mic.

 

[kemmler3D]

+1 to crossing the sub higher to try and fill in the null.

I dispute that the null isn't audible though. If you are listening to any bass that doesn't have a ton of overtones / harmonics, if a note falls right in that frequency range it's going to suddenly disappear and the next note will boom out. I find that nulls in bass are actually hard NOT to hear once you start hearing them. My old setup had a nasty null at 65hz and once I knew about it, I couldn't stop hearing it.

 

[mj30250]

First of all, I wouldn't put too much stock in Audyssey's before graph (and none in the after). It's simply not large enough or at sufficient resolution to provide you with what's truly going on. You should really invest in a mic + REW. Anyway, I also had a narrow but deep null just north of 80Hz (see below - this is a dual sub setup). I kept one of the subs in the same location but simply turned it 180 degrees and that completely eliminated the dip.

Before:

After: