Room modes

[OCA]

But I wonder what effect it has on the spatial cues being a mono system? Would the crossover have to be below 50 hz?

XO @ more like 100Hz and there's still a gap which cannot be filled with the current room treatment technology according to them.

TW focuses on bass uniformity across the seats of a home cinema rather than the traditional stereo listening environment. Although it would be exciting to hear to have rear wall reflections completely obliterated at their source, one should consider there will be leftovers from the cancellation signal flying around in the room which may or may not be easy to cope with for the trained ear.

PS I am not sure but I believe TW sends a cancellation signal for the cancellation signal from the front subwoofer array as well! Still, there are almost no subwoofers today designed to be hung in the middle of walls nor there are any bass absorbers truly effective below 150Hz. The need for digital filters is still very eminent IMO.

 

[Justdafactsmaam]

XO @ more like 100Hz and there's still a gap which cannot be filled with the current room treatment technology according to them

nor there are any bass absorbers truly effective below 150Hz.

I do plan to put that to the test.

 

[j_j]

TW focuses on bass uniformity across the seats of a home cinema rather than the traditional stereo listening environment.

Uniformity is not really the goal for realism until you're below 40Hz or so. What you want to have is a good grasp of the actual complexity of the INTENDED soundfield, in the form of what one would really see in the intended environment.

Sometimes, yes, that's monophonic.

Although it would be exciting to hear to have rear wall reflections completely obliterated at their source, one should consider there will be leftovers from the cancellation signal flying around in the room which may or may not be easy to cope with for the trained ear.

Um, doing pressure cancellation from the rear really does not remove any energy, sorry. It adds a new set of travelling waves heading the other direction. It is possible over a limited area, to avoid extreme problems, if done carefully.

Some absorption, even if only a few dB, can do wonders, too.

 

[Pareto Pragmatic]

Look at it the other way around and consider your self lucky. Put a egg seater or silicone acoustic pack's between floor and speakers/sub's to move the 30 Hz resonance down and use self filter on it and you have cheap extension to 30 Hz.

If only. I have isolated the sub, which helps. But the sound moves the floor so that only bought me a few extra dB until things go off the rails.

I can actually change the sub angle, not location, and activate a 15hz mode at high SPL, but that also makes the 30 worse. Used to do that with my old $100 sub.

But in some ways I am lucky, and I do think that way most of the time. I do get good bass without a sub. And when the weather is nice and I can open windows and a door, I can get as loud as I ever want to without major issues, sub or no sub. And if I get things just right, at the right point of "problems", I can make the room feel like a club where the band is JUST overpowering the room. So good for a "live" feel.

Best, I have a spot about 9' into the room where speakers really shine, and where all but one mode are minimal. But that's not a livable set up for the main room of the house, for some reason.

 

[ZolaIII]

@Pareto Pragmatic show me what you did and I will try to help you more. I told you to cut it under and I don't think you did that (tho I might be wrong).

 

[youngho]

Still, there are almost no subwoofers today designed to be hung in the middle of walls

@sigbergaudio The Inkognitohttps://www.sigbergaudio.no/products/inkognitosubwoofer

nor there are any bass absorbers truly effective below 150Hz

John Brandt's limp bag design, also the RealAcoustix BassMod (https://www.realacoustix.net/architectural-bass-absorption), from what I've read by Ron Sauro of NWAA Labs (https://www.nwaalabs.com/)

 

[Flaesh]

Still, there are almost no subwoofers today designed to be hung in the middle of walls

A subwoofer is simply a sturdy box with a decent driver [assuming external processing and amplification]. IIRC «Trinnov» subs are made by Australian cinema speakers manufacturer, I forgot brand, IIRC starts with the letter K.
Still, here are almost no users willing to hung subwoofers on the front and rear walls. See DBA treads.

 

[Pareto Pragmatic]

@Pareto Pragmatic show me what you did and I will try to help you more. I told you to cut it under and I don't think you did that (tho I might be wrong).

I am sure you can come up with things that are better than my rug/foam/hockey puck isolation system for my sub.

I appreciate the offer, really I do. But there's not much I can do to improve things further. A 7 pound cat jumping from a seat to the ground spikes 30 in my room. Foot taping spikes it. it is literally a drum, not a good drum, but a drum. As SPL goes up, the drum gets drummier, until it starts to go crazy. As in, the cat jump spikes 30hz up ~15dB, when I am playing white noise at 70dB 12 feet from the speakers. That's on top of the steady state effect of 70dB white noise.

It is the physical motion of the floor that is the issue. Bouncy bouncy.

The actual solution would involve putting a new beam and posts in the basement after jacking the floor up, which would likely crack a bunch of plaster. And that would also screw up the floating engineered wood floor on top of the hardwood underneath. I did install a "very much not structural for purposes of code" post and beam across 3 joists in the basement, which made things a lot better. But beyond that would be a lot of money and likely a lot of plaster patching.

An extra thick rug pad helped a lot, btw. Thicker, but also heavier which helped with the bouncing, and tends to keep the surface vibrations under control a bit longer.

I can live with what I have now. When the weather is nice and things are open I have to get too loud for me to make things go crazy.

Thanks again for the offer of help!

 

[Flaesh]

A 7 pound cat jumping from a seat to the ground spikes 30 in my room.

Quite a light cat; Is it an adult animal or is it still growing?..
Fairly high frequency; My floor shakes at 10-12 hertz.

 

[ZolaIII]

@Pareto Pragmatic you wouldn't believe but I use egg seaters under my sub's and have equally bad room mode little high (43 Hz) which you can see how good I autended little earlier hire. Rest is the same thick wool rug and small room, minimal phase corners positioning. So sure I can help you if you show me what you are getting and placement. You should try to play with REW room simulator for starters. Goal is to eliminate nulls by placement at least as much as possible. Then you PEQ peeks and on prominent room modes even do two pass PEQ's. I have cat's including fat male ones but they rarely go to my listening room.

 

[Pareto Pragmatic]

@Pareto Pragmatic you wouldn't believe but I use egg seaters under my sub's and have equally bad room mode little high (43 Hz) which you can see how good I autended little earlier hire. Rest is the same thick wool rug and small room, minimal phase corners positioning. So sure I can help you if you show me what you are getting and placement. You should try to play with REW room simulator for starters. Goal is to eliminate nulls by placement at least as much as possible. Then you PEQ peeks and on prominent room modes even do two pass PEQ's. I have cat's including fat male ones but they rarely go to my listening room.

Here are things you can do to help.

1-Do magic and make the temperatures like summer, so I can open up 10-12 windows.

2-Come over and help me move my current 90lb/40kg speakers out into the room, because if I do that and slap on an EQ at 250, all is well.

3-convince my bass loving wife that flat base is better. My current corrections are a compromise in tastes, so I have toned down the room some, but left some boost 80-120. She likes it, I can live with it. I have been listening no sub when she is not around, sub when she is.

My actual solution is to buy some stand mounts and set them up when I want best sound. Because the speaker position for 2 above works really, really, really well. For music, not for living life in our main room.

But I do appreciate the offer of help. When I get time I am going to integrate the sub with my fosi v3 for their new position (went from an asymmetrical set up to a symmetrical position). The AV eq went well, the no sub eq went well, but I may have some issues to ask about with the fosi+sub. Usually it is easier to set up than the AV amp, but if I have issues, I will certainly ask on ASR.

 

[ZolaIII]

@Pareto Pragmatic ad some doubt to the second part of your nick and call it profession (as it is profesor and so am I) and you are on the good path.
Bass loving wife that's a rare thing. I think you would also like it more when good integrated and ironed out. Would love to come and help even regarding hard pushing but we are 2000 miles apart. The answer is actually equal loudness normalisation I don't believe in bass heads and other way around we just like to listen on different SPL levels (influenced by many things). I really ment showing me position, room (and dimensions of it), listening spot and distance to it and to the wall behind it and REW measurements (preferably private), everything else is just empty talk.
Of course do ask and people will help, that's what community is really about.
Have a nice time and enjoy.

 

[Flaesh]

It adds a new set of travelling waves heading the other direction. It is possible over a limited area, to avoid extreme problems, if done carefully.

https://www.audiosciencereview.com/forum/index.php?attachments/animation-gif.234687/

Why don't we see the second one?

 

[j_j]

https://www.audiosciencereview.com/forum/index.php?attachments/animation-gif.234687/

Why don't we see the second one?

Because you didn't include it in your simulation?

 

[NTK]

https://www.audiosciencereview.com/forum/index.php?attachments/animation-gif.234687/

Why don't we see the second one?

Double bass array, aka Controlled Acoustic Bass System (CABS), is a specific case that utilizes bass drivers to turn the rear wall in effect into an absorbing boundary. It "makes" the acoustic impedance of the rear wall the same as the room air, and to the sound waves the rear wall will behave just like a continuation of the room, and therefore the sound waves will be absorbed with no reflection.

It works best when the room is rectangular and the drivers are flush mounted in the front and rear walls.

Source: https://vbn.aau.dk/en/publications/low-frequency-sound-field-control-in-rectangular-listening-rooms-

The original CABS paper is behind the AES paywall.

AES E-Library » Controlled Acoustic Bass System (CABS) A Method to Achieve Uniform Sound Field Distribution at Low Frequencies in Rectangular Rooms

A new method for improving the low-frequency response in small- and medium-sized rooms uses a pair of front loudspeakers for initiating a traveling plane wave and a canceling rear pair of loudspeakers that effectively remove the acoustic reflection of the back wall. The rear loudspeakers receive...

www.aes.org

 

[Flaesh]

Because you didn't include it in your simulation?

Not mine, taken from https://www.audiosciencereview.com/...of-the-double-bass-array-configuration.37943/

It works best when the room is rectangular and the drivers are flush mounted in the front and rear walls.

I have DBA, link in signature.

 

[j_j]

Double bass array, aka Controlled Acoustic Bass System (CABS), is a specific case that utilizes bass drivers to turn the rear wall in effect into an absorbing boundary. It "makes" the acoustic impedance of the rear wall the same as the room air, and to the sound waves the rear wall will behave just like a continuation of the room, and therefore the sound waves will be absorbed with no reflection.

It works best when the room is rectangular and the drivers are flush mounted in the front and rear walls.

View attachment 345487

Source: https://vbn.aau.dk/en/publications/low-frequency-sound-field-control-in-rectangular-listening-rooms-

The original CABS paper is behind the AES paywall.

AES E-Library » Controlled Acoustic Bass System (CABS) A Method to Achieve Uniform Sound Field Distribution at Low Frequencies in Rectangular Rooms

A new method for improving the low-frequency response in small- and medium-sized rooms uses a pair of front loudspeakers for initiating a traveling plane wave and a canceling rear pair of loudspeakers that effectively remove the acoustic reflection of the back wall. The rear loudspeakers receive...

www.aes.org

And in the "travelling in the same direction" is the hard part. Yes, it's possible. It's not easy, and the energy of both waves has to go somewhere.

 

[NTK]

I have DBA, link in signature.

DBA is a special, not general, case.

 

[Flaesh]

DBA is a special, not general, case.

A special case (similar to DBA?) was discussed:

doing pressure cancellation from the rear really does not remove any energy, sorry. It adds a new set of travelling waves heading the other direction.

In general case standing waves exist in room, I think.

 

[j_j]

A special case (similar to DBA?) was discussed:

In general case standing waves exist in room, I think.

DBA is very tricky (consider how you make a second wave opposite the first, going in the same direction, without creating anew back wave. Consider how that works. I'm not saying it's impossible.