Are my bass traps not working? Some changes in var smoothed frequency response, but not much in ERB smoothed one.

[Bjorn]

The difference between a room with very short low frequency decay and more or less no resonances vs a room with only even response based on EQ/multiple subwoofers with the traditional poor time domain behaviour is so massively different that one must be close to deaf to not hear it.

 

[dasdoing]

The difference between a room with very short low frequency decay and more or less no resonances vs a room with only even response based on EQ/multiple subwoofers with the traditional poor time domain behaviour is so massively different that one must be close to deaf to not hear it.

I think even the deaf can feel the difference.
people who defend that hypothesis simply never heard a bass-treated room. the ringing is natural after all. it is expected to happen. that's why you don't notice it until you heard a decay controlled room.

 

[ozzy9832001]

At low frequencies, rooms are mostly minimum phase systems. Toole advocates against trying to fill in dips in the bass response by turning up the volume of the subwoofer if the dip is caused by phase cancellation. The dip is non-minimum phase so it can never be filled. I love the rest of your explanation, nice and clear as always

I actually found this to the be most practical solution in a lot of cases. Turn the volume up and EQ the peaks down so everything is generally flat.

As for the OP's question, which seems to have been lost now.

The over under is that you typically need a large amount of treatment, especially in a smaller room to get a good result. It is also important to treat the room equally across all surfaces so absorption is consistent. 4 panels at the size and thickness described even with air gap isn't enough. Since the panels will naturally absorb more high frequencies than low, it is important to have a system in place to prevent that (slats, diffusors, etc)

For typical Rockwool-esque panels they need to be fairly thick to reach into the sub 100hz range. There are other types of targeted traps that will work lower, but can be either very expensive, heavy or difficult to get commercially. Less, thicker traps could be a way to go. I'm currently using 7.25" rockwool which I didn't even know existed and I've had very good results with half the panels I used to.

OPs room is very small, so corner straddling, thick traps maybe a good option, as floor to ceiling could be 6-8 traps right there, depending on where the door is located.

 

[Bjorn]

ok, then lets forget everything else and just concentrate on this question, which refers to your previous statement. I´m sure as an dealer of room acoustic products, you can provide us with reliable numbers:

Somewhere between $400 and $1500 in most cases.

 

[Paffi]

Somewhere between $400 and $1500 in most cases.

Just took a look at your price list and noticed, that the bass absorber is around 500€ each. If the complete room treatment would really be that cheap, respect! (Just to add, that you get many good single subwoofers in this price region)

 

[Paffi]

The difference between a room with very short low frequency decay and more or less no resonances vs a room with only even response based on EQ/multiple subwoofers with the traditional poor time domain behaviour is so massively different that one must be close to deaf to not hear it.

I think there is nobody who disagrees.

 

[Paffi]

graphs, e.g. OP's in post 25, clearly show that this is not the case.

While it's, of course, not 1:1 correlation, eq'ing does not solve the problem with reverb completely (I'm also writing this to people again and again, when they try to fix room related problems with eq). But it helps a little bit and for the sake of completeness:

"Both room modes and IIR filters are minimal phase, so that not only the amplitude response is linearized, but also the decay is reduced" (source: wikipedia, translated).

AND you can indeed solve reverb issues with multiple subs.

 

[dasdoing]

While it's, of course, not 1:1 correlation, eq'ing does not solve the problem with reverb completely (I'm also writing this to people again and again, when they try to fix room related problems with eq). But it helps a little bit and for the sake of completeness:

"Both room modes and IIR filters are minimal phase, so that not only the amplitude response is linearized, but also the decay is reduced" (source: wikipedia, translated).

AND you can indeed solve reverb issues with multiple subs.

of course, the decay gets quieter when you EQ the frequency down. nobody denies that

 

[Bjorn]

Bringing down peaks with many dBs tend to sound tame and lack tactile experience IMO. Even when you have a lot of SPL and headroom available.

One reason could be because it measures differently at other heights and bass is something we also feel with the body, but I don't have full explanation of why. I therefore seldom bring a peak down more than about 3 dB if EQ is the only option.

 

[Justdafactsmaam]

That

That's wrong and depends on the configuration. I by myself use multiple subs for that.

How can you configure subs to reduce room mode based reverb?

 

[NTK]

History of Multi-Sub & Sound Field Management (SFM) for Small Room Acoustics

Solving bass problems in small rooms have historically been done with low frequency absorption (ie. bass traps). This article discusses an alternative/complimentary solution using multi-sub and SFM.

www.audioholics.com

 

[theREALdotnet]

How can you configure subs to reduce room mode based reverb?

Room modes and reverb are unrelated. The former is a function of the room geometry, the latter of the energy preservation across the frequency range.

Room modes are what they are, they cannot be changed without changing the room geometry. You can avoid exciting them by not putting subs into the wrong spots, and you can reduce your suffering from them by not sitting in the wrong spot.

Reverb means how long a sound event lingers in the room through reflection. It affects all frequencies, not just the room modes. It is treated by absorption, i.e. burning up the energy of the reflected sound, or by leaking energy out of the room.

 

[Justdafactsmaam]

History of Multi-Sub & Sound Field Management (SFM) for Small Room Acoustics

Solving bass problems in small rooms have historically been done with low frequency absorption (ie. bass traps). This article discusses an alternative/complimentary solution using multi-sub and SFM.

www.audioholics.com

View attachment 375078

Did you look at the waterfall plots? Adding subs did not help at all in the time domain. Might have actually made things worse. And they are just plain bad RT measurements. This article does not make a good argument IMO.

 

[Justdafactsmaam]

Room modes and reverb are unrelated. The former is a function of the room geometry, the latter of the energy preservation across the frequency range.

Room modes are what they are, they cannot be changed without changing the room geometry. You can avoid exciting them by not putting subs into the wrong spots, and you can reduce your suffering from them by not sitting in the wrong spot.

Reverb means how long a sound event lingers in the room through reflection. It affects all frequencies, not just the room modes. It is treated by absorption, i.e. burning up the energy of the reflected sound, or by leaking energy out of the room.

Simply not true. Room modes will magnify reverb time. They are directly connected. And it’s easy to see that connection in any waterfall plot.

And you certainly can change room modes with either passive or active bass traps

 

[Justdafactsmaam]

While it's, of course, not 1:1 correlation, eq'ing does not solve the problem with reverb completely (I'm also writing this to people again and again, when they try to fix room related problems with eq). But it helps a little bit and for the sake of completeness:

"Both room modes and IIR filters are minimal phase, so that not only the amplitude response is linearized, but also the decay is reduced" (source: wikipedia, translated).

AND you can indeed solve reverb issues with multiple subs.

Let’s see some actual measurements in support of this

 

[Keith_W]

Simply not true. Room modes will magnify reverb time. They are directly connected. And it’s easy to see that connection in any waterfall plot.

Any volume peak will give you an apparent increase in reverb time. Try this - create a +10dB 25Hz wide peak at say 100Hz with your PEQ and then look at your waterfall plot.

 

[Justdafactsmaam]

Any volume peak will give you an apparent increase in reverb time. Try this - create a +10dB 25Hz wide peak at say 100Hz with your PEQ and then look at your waterfall plot.

An EQed peak will increase the reverb time. But will not have the same rate of decay as a room mode induced peak. Resonances are the gifts that just keep giving.

Either way the bigger point is EQ doesn’t fix anything in the time domain

 

[Duke]

This article by Earl Geddes might be of interest. It's more of a theoretical background than a "how to", and it looks at room size and shape, damping, EQ, and multiple subwoofers. Unlike what happens in threads like this (and of which I am guilty!), it does not pit one approach against another, but it does look at what is effective in different frequency regions.

Earl Geddes, Why Multiple Subs, 2011.pdf

drive.google.com

A related article, based on Geddes' work: https://mehlau.net/audio/multisub_geddes/

 

[Paffi]

Let’s see some actual measurements in support of this

What exactly? That you can eliminate/ reduce reverb time with several subs? That's nothing new, this technique is decades old and already used in uncountable number of settings. You just have to phase invert the back array and time delay it for the room distance.

 

[Justdafactsmaam]

What exactly? That you can eliminate/ reduce reverb time with several subs? That's nothing new, this technique is decades old and already used in uncountable number of settings. You just have to phase invert the back array and time delay it for the room distance.

Ok so you are speaking specifically of a double bass array. Yeah, that will work, just not evenly. It’s the poor man’s version of the Trinnov wave form technology.

I thought you were referring to the more common swarm array. Which will smooth frequency response but not reduce reverb time.

And I am wondering, double bass array, doesn’t that have to be all mono?