[Chris Kaoss]

I don’t think even room treatment can deal with a sub crammed in a corner. Maybe suspending the sub from the ceiling in a more favorable position might help.

Speaker placement is probably the most important factor. If you start off on the wrong foot there, there’s no fixing it.

You're right.
That's the worst place for a sub i can think of.

@Selbi
Just for the sake of curiosity, how does it change if you place the sub like a frontfiring one?

 

[Selbi]

Well, I gave it a full test with the blankets and pillows again. No luck, it the droning prevails.

However, I did take a look in the manual and saw something regarding the XLF setting that caught my attention:

When the XLF crossover setting is selected, a 120Hz High Pass Filter is engaged in conjunction with a 10 dB boost at 60Hz with a bandwidth of 0.5 octaves.

I then took a look in my APO and played around with the 50-80 Hz range, and I can technically EQ that out... but it obviously kills all sub-bass. I then switched the setting back over to 80Hz (which is also what the manual recommends to be used in conjunction with the JBL LSR305), which audibly reduced the oomph, but it sounds ever so slighlty better. Still not great, especially on Dance Macabre, but the droning seems to have gone down a little...

Just for the sake of curiosity, how does it change if you place the sub like a frontfiring one?

Toppled it over to the side, no audible differences to the droning either.

 

[71 dB]

I've got some annoying issues with my subwoofer. There are some very specific low frequencies that don't respond well to my walls, causing a muddy droning sound to go through the entire room. Here's an audio example:

https://cdn.discordapp.com/attachments/430361376951894037/829440287705006192/droning.mp3

I'm more interested in a general approach how to fix such muddy frequencies in any scenario. Is there something like a tool that goes through the frequencies range slowly so you can identify the specific frequencies that cause this? And then how would you actually EQ that stuff out?

What sounds really bad in this audio example is the "droning" of 131 Hz (note C3). I notch-filtered it out by 12 dB (Q=10) and the sound became dramatically better (see the waveforms attached (upper = notch-filtered, lower is original). I notch-filtered 131 by 6 dB more and the sound got even better. The second most boost happens around 75 Hz, which I notch-filtered by 6 dB at lower Q. After these the sound sample appears okay for a typical living room.

Why does this sub go so damn high? Setting the crossover below 100 Hz would help with the 131 Hz issue. Its good to go as low as possible with the main speakers and have as low crossover frequency as possible. That way you don't hear here the sub is located.

The wavelength of 131 Hz is about 2.6 meters or 7.5 feet. That can help identifying the problem, but really lowering the crossover frequency is step one.

 

[71 dB]

EQ won’t fix something like that. Think about rearranging furniture perhaps.

Why not?

 

[Selbi]

Oh wow, EQ'ing out 131 Hz as you described worked wonders! I don't really know what most of these numbers mean, but blindly following helped immensly!

Take a listen at this audio sample with Dance Macabre again. It still got a bit of droning, but if you compare it to the sample from the first post the difference is night and day:

https://cdn.discordapp.com/attachments/430361376951894037/829678499399729232/droningbetter.mp3

I got multiple questions now: What does Q mean? What did you set you the Q to for 75 Hz (you only mentioned "lower")? And, most importantly, how did you identify the cause was 131Hz, cause I'd like to learn how to approach such problems in the future.

Why does this sub go so damn high?

Yeah, it's weird. While the manual states the XLF setting has a high-pass filter at 120 Hz, it doesn't really make much sense why it goes that far up beyond. Furthermore, setting it to 80Hz crossover doesn't get rid of the droning either. Only this explicit removal of the 131 Hz range did something.

Now I wonder if my monitors were the problem after all, but it seems counterintuitive considering how far they are away from the wall:

That's a good three feet away. Can it be a problem anyway?

 

[zizzyhead]

Oh wow, EQ'ing out 131 Hz as you described worked wonders! I don't really know what most of these numbers mean, but blindly following helped immensly!


Take a listen at this audio sample with Dance Macabre again. It still got a bit of droning, but if you compare it to the sample from the first post the difference is night and day:

https://cdn.discordapp.com/attachments/430361376951894037/829678499399729232/droningbetter.mp3

I got multiple questions now: What does Q mean? What did you set you the Q to for 75 Hz (you only mentioned "lower")? And, most importantly, how did you identify the cause was 131Hz, cause I'd like to learn how to approach such problems in the future.


Yeah, it's weird. While the manual states the XLF setting has a high-pass filter at 120 Hz, it doesn't really make much sense why it goes that far up beyond. Furthermore, setting it to 80Hz crossover doesn't get rid of the droning either. Only this explicit removal of the 131 Hz range did something.

Now I wonder if my monitors were the problem after all, but it seems counterintuitive considering how far they are away from the wall:


That's a good three feet away. Can it be a problem anyway?

Its easy enough to find out, just temporarily tape up the ports and see. Its not perfect but it will give you some info.

 

[71 dB]

Oh wow, EQ'ing out 131 Hz as you described worked wonders! I don't really know what most of these numbers mean, but blindly following helped immensly!


Take a listen at this audio sample with Dance Macabre again. It still got a bit of droning, but if you compare it to the sample from the first post the difference is night and day:

https://cdn.discordapp.com/attachments/430361376951894037/829678499399729232/droningbetter.mp3

I got multiple questions now: What does Q mean? What did you set you the Q to for 75 Hz (you only mentioned "lower")? And, most importantly, how did you identify the cause was 131Hz, cause I'd like to learn how to approach such problems in the future.


Yeah, it's weird. While the manual states the XLF setting has a high-pass filter at 120 Hz, it doesn't really make much sense why it goes that far up beyond. Furthermore, setting it to 80Hz crossover doesn't get rid of the droning either. Only this explicit removal of the 131 Hz range did something.

Now I wonder if my monitors were the problem after all, but it seems counterintuitive considering how far they are away from the wall:


That's a good three feet away. Can it be a problem anyway?

Of course filtering 131 Hz helps. The numbers on top are the frequencies, then is the gain (negative number mean attenuation) and the bottom number is Q-value, which means how narrow the filter is. Q=1 means pretty broad filter so it affects frequencies below and above 131 Hz while Q=10 is rather sharp notch filter affecting only frequencies very near 131 Hz. The "droning" of 131 Hz is very sharp, the resonance has very high Q-value so Q=10 works well. If the Q-value was for example only 2, frequencies such as 120 Hz would be attenuated too much when there is no need to do that. Try this: Gain 0 dB for everything else than 75 Hz and 131 Hz. For 75 Hz make Q = 4 and gain -6 dB. For 131 Hz Q=10 and gain -15 dB. Should sound pretty good.

I identified the 131 Hz by looking at the spectrum (in free Audacity software) of the sound sample (see attachment). It looks like your room has a mode exactly at this frequency which is also note C3. So everything composed in C major/minor/dorian/lydian/phrygian... is likely to give this droning. Playing with spectrums requires some practice and knowledge regarding window functions and window sizes so it can be confusing at first (just a warning for total newbies).

I'd say this is your main speakers doing this, but why does this droning go away when you move your sub? Try playing music through your main speakers only (sub off). You have a good distance from the walls, but room modes don't care. What are the dimension of your room? You can also move your head around the room (also down/up) and try to find where it disappears. That gives insight into what kind of room modes causes it.

See the sharp spike above 100 Hz. The cursor/peak (29 Hz) is "wrong" here because I screen capture selection. If you move the cursor near the spike the Peak "snaps" to 132 Hz, but there is also a little error (by about 1 Hz due to frequency resolution and peak estimation algorithms) so I made it 131 Hz (note C3). Close enough.

 

[71 dB]

Its easy enough to find out, just temporarily tape up the ports and see. Its not perfect but it will give you some info.

Except the reflex ports hardly radiate much acoustic energy at 131 Hz given the fact that typical resonance frequencies of reflex port speakers of this size are an octave or more lower (around 50-65 Hz). The speakers radiate most of the acoustic energy at 131 Hz from the bass drivers, not from the reflex ports.

 

[bigshot]

Why not?

It seems to me to be pretty heavy lifting for EQ to fix. But it's certainly worth a try. I'm guessing there are more problems in that room than one. I had a friend who had a McIntosh system crammed into a small bedroom, with huge Altec Lansing cabinet speakers that were as big as a washer and dryer. He had them on either side of a bed. He EQed to try to fix it, but even afterwards it was the worst sounding good system I ever heard. But who knows, maybe EQ is the trick here.

 

[71 dB]

It seems to me to be pretty heavy lifting for EQ to fix. But it's certainly worth a try. I'm guessing there are more problems in that room than one. I had a friend who had a McIntosh system crammed into a small bedroom, with huge Altec Lansing cabinet speakers that were as big as a washer and dryer. He had them on either side of a bed. He EQed to try to fix it, but even afterwards it was the worst sounding good system I ever heard. But who knows, maybe EQ is the trick here.

Well, it is true one should first do the acoustics of the room right + do the speaker/listening spot placement optimization before other stuff, but if there are clear room modes, precise notch filtering can make a difference, but you have to know what you are doing.

Bringing huge Altec Lansing cabinet speakers into a small bedroom is lunacy.

 

[Selbi]

Try this: Gain 0 dB for everything else than 75 Hz and 131 Hz. For 75 Hz make Q = 4 and gain -6 dB. For 131 Hz Q=10 and gain -15 dB. Should sound pretty good.

Sorry for the delay, took some time to get around to properly sit down and do this. I can report back that this indeed did the trick, though I didn't have to trim off a whopping 15 dB for 131 Hz, as 6 were already enough to get rid of the droning. For 75 Hz I don't really feel much difference in terms of droning, but I gave it a reduction of 1 dB for good measure anyway. The Q's were left unchanged from your suggestions though. With these settings, the droning disappeared almost entirely:

Now, however, I do have to admit something. I did experiment a little more with speaker setup and found out that, despite my initial assumptions, indeed it wasn't the subwoofer that caused this, but the monitors after all. If I turned them off and only let the sub do its thing, it was clean as can be, no droning whatsoever. I feel very stupid now and I could've bet a tenner on it being the felon. But here I stand corrected.

Whatever the case may be, I'm glad it's fixed now and I don't have to spend ridiculous amounts of money for these absorber thingies. They'd probably take care of my problems, but I neither lack the space nor the funds to put them up, so that's gonna have to wait for a while.

Thanks for your tremendous support!

 

[71 dB]

Sorry for the delay, took some time to get around to properly sit down and do this. I can report back that this indeed did the trick, though I didn't have to trim off a whopping 15 dB for 131 Hz, as 6 were already enough to get rid of the droning. For 75 Hz I don't really feel much difference in terms of droning, but I gave it a reduction of 1 dB for good measure anyway. The Q's were left unchanged from your suggestions though. With these settings, the droning disappeared almost entirely:


Now, however, I do have to admit something. I did experiment a little more with speaker setup and found out that, despite my initial assumptions, indeed it wasn't the subwoofer that caused this, but the monitors after all. If I turned them off and only let the sub do its thing, it was clean as can be, no droning whatsoever. I feel very stupid now and I could've bet a tenner on it being the felon. But here I stand corrected.

Whatever the case may be, I'm glad it's fixed now and I don't have to spend ridiculous amounts of money for these absorber thingies. They'd probably take care of my problems, but I neither lack the space nor the funds to put them up, so that's gonna have to wait for a while.

Thanks for your tremendous support!

Well, it was good you took the time to investigate this carefully. Yes, the first 6 dB cut for 131 Hz takes the most of the "droning" away and also it is possible the droning isn't as bad to begin with in your listening position compared to the point where you made the recording. So, by all means try different values for what sounds best. If 7 dB gives the best result then 7 dB it shall be and so on... ...the 75 Hz area isn't that problematic, but I suggested a way to improve it. Again, if 1 dB gives the best result in the listening point that's the way to go. These droning notes really sound different in different points in the room, especially when you move in the direction the corresponding room modes are created.

I am not surprised at all it was the speakers doing the 131 Hz droning. Makes so much more sense than the sub causing it. Feeling stupid is a sign of learning something new and that's a positive thing. What you can do now is try bypassing the filter and try moving the speakers around for a few inches to see (hear), if you can find a flatter response and then filter the rest away. The less you need to filter the better. That's why improving room acoustics is a good thing if you can do it, but if you can't then this filtering can definitely help fixing things partially. The advantage of good acoustics is that the sound is good almost anywhere in the room (bigger sweet spot) while these filtering tricks can optimize the sound for only one point. Try also "furniture acoustics" meaning use furniture that makes as much acoustic treatment as possible such as thick carpets on the floor etc. things that aren't insanely expensive nor take additional space.

You are welcome! I glad I was able to help.

 

[bigshot]

I really can't make any recommendation without a floor plan of the room. Speaker placement and furniture placement is critical. If you start off wrong, you can't patch all the problems... Like the guy I knew with two giant Altec Lansing speakers on either side of his bed. No soundstage. The speakers were coupled with the corners of the room. The drivers were firing into an alley down the side of his bed. There's no fixing that.

I'd suggest considering room layout before trying to put band aids on all the problems. Once you've done everything you can do there, then move on to the next fix.

 

[redrol]

Ive tried all kinds of subwoofer positions and turns out just putting it on the side of my chair works amazingly perfectly... and my chair is no where near a wall.. kind of off center in the room in question.

 

[71 dB]

Ive tried all kinds of subwoofer positions and turns out just putting it on the side of my chair works amazingly perfectly... and my chair is no where near a wall.. kind of off center in the room in question.

Good subwoofer placements can be found using reciprocity of sound and acoustics. The subwoofer is placed where your head would be in when you sit in your listening chair. Then you play test tones or music and test with your head places in the room where to put the subwoofer. When the bass sounds good, you have found a place for your subwoofer.