Holes In Walls To Tune The Room?

[ttocs]

If a hole is cut into a wall, will that effectively become a "Port" of some type?

If the hole is in a corner, can the wall cavity become a bass trap?

If a door opening effectively sucks out bass, isn't a hole in the wall a tiny version of this?

Will a hole in a wall change anything with respect to frequency waves in a room?

As always, just curious.

[DYohn]

Yes, a hole cut into a wall can become a Helmholtz resonator bass trap. It is a technique commonly used in cinema design (resonators built into seat riser platforms.) The trick is to design it so it becomes functional in your room. Most spaces lack sufficient low frequency energy to make them very meaningful, but in a space with lots of excess bass energy or large room modes they can work. You need to design them for the frequency band you wish to attenuate.

[KeithL]

It's also worth noting that a Helmholtz resonator is an organ pipe...

It's also the thing that makes a hooting noise when you plow across the neck of a bottle...

(It would be more accurate to say that both bottles and organ pipes are Helmholtz resonators.)

In other words, a resonator resonates (rings) at a particular frequency, which means that it can attenuate energy, or it can do the opposite...

It's only going to act as a bass trap if you tune and position it precisely to counteract something going on in your room.

And, if you get it wrong, then it's going to make things worse instead of better.

So you really have to know what you're doing to get a good result.

Dec 3, 2020 16:13:09 GMT -5 DYohn said:

Yes, a hole cut into a wall can become a Helmholtz resonator bass trap. It is a technique commonly used in cinema design (resonators built into seat riser platforms.) The trick is to design it so it becomes functional in your room. Most spaces lack sufficient low frequency energy to make them very meaningful, but in a space with lots of excess bass energy or large room modes they can work. You need to design them for the frequency band you wish to attenuate.

[leonski]

When I had my sub in a certain location my DEN was a one-note resonator. It was awful to sit in the den with music playing in the next room.......Like being in a 55 gallon DRUM.

I fixed the room AND the bass problam by moving the sub about 12 feet or so. Bass became MUSICAL and the den now has normal sound.....

A win win. And I learned something....

[ttocs]

So, if I cut holes just the right size, in just the right places, I can make my room sound like a Pepsi bottle? 

Thanks for the responses! Great stuff to know about.

Since I've been rewiring the system, I leaned down in one corner and heard the low frequency buildup from the refrigerator in the kitchen area (it's a multipurpose room). Got me thinking about bass traps. So I came up with those questions to spark a dialogue hoping for those kind of responses. I love acoustical theory and application, but I'm a babe in the woods on the stuff.

[leonski]

I suspect but dont' know the extent of it, that 'ports' from room to room to 'tune' bass is as much art as science.

The TRICK is 'right size-right place'......

A buddy wanted to experiment with bass traps. He invited over a couple 'bulky' friends. Me, for example!

Stand HERE......(a corner_) and so forth until he had a couple answers to his questions. And YES, a bulky person standing hard INTO a corner

can act as a poor mans bass trap for experimental purposes. I've seen a number of interesting design proposals.

[ttocs]

Dec 4, 2020 0:59:38 GMT -5 leonski said:

I suspect but dont' know the extent of it, that 'ports' from room to room to 'tune' bass is as much art as science.

The TRICK is 'right size-right place'......

So, how to figure out Where, and How Big?

Might it be possible to use REW and move the mic around to see where the pressure areas are? hmmmmm . . . . . 

[leonski]

www.mh-audio.nl/Acoustics/HHReso.html

I think I'd start with 'standing waves' in a room. As the room gets more ....complicated....the calculations can get out of control.

But for what amounts to a simple, 'cubic' or 'Cubic / Rectangular' room, the type of calculator I link would perhaps be a starting point.

Than Of Course, the room into which you vent the hole will become UnLiveable since it'll be one-note bass heavy. Like my den WAS.

[Deleted]

Forget any hole in the wall.  Any change in the room can and many times does effect your system's sound.  Examples, open or shut room doors, carpet or no carpet or throw rugs, finish on the walls, moving furniture, ceiling surface, placement of speakers (on floor or stands, against wall, in corner) and on and on.

Put the drill away for now.
  

[ttocs]

Dec 15, 2020 21:21:53 GMT -5 @tllfkacn said:

Forget any hole in the wall.  Any change in the room can and many times does effect your system's sound.  Examples, open or shut room doors, carpet or no carpet or throw rugs, finish on the walls, moving furniture, ceiling surface, placement of speakers (on floor or stands, against wall, in corner) and on and on.

Put the drill away for now.

I'm putting the drill down . . . . . and stepping away from it . . . .

It's HI-LARIOUS that you mention doors to other rooms and such, because just today I did just that!

There is a hallway that has 3 bedrooms and two bathrooms. The hall has no door, and some doors are normally closed, others normally open. I closed some doors and noticed a difference in REW. Then I closed off the hallway with a sheet of MDF, again, difference. Then added MDF to one corner of the dining area (far left of system, same wall), got another difference. Took that MDF and the sheet closing off the hallway, then added two bales of mineral wool to the dining area corner, and another difference. Then played with a 2x4 absorb panel in the right corner behind the Right speaker and a double stack of subs, and another difference.

These differences are very noticeable and a tuning preference can be seen in the plots, if you need some of this - do that. In the end, it's a bunch of little things together that add up. Closing 3 doors, adding a 2x4' absorption panel behind the Right speaker, and moving the Right speaker and sub stack to the left made the improvement of closing the mouth of a wide/deep null from 60Hz-77Hz/35dB deep, to 59Hz-72Hz and only 15dB deep. That's a 4Hz and 20dB improvement. Pretty good for two free tweaks and one that costs about $8.

Below is a plot that shows the effect of what is so stupidly simple and free - Shut The Doors!
The red line is after closing two bathroom doors and one bedroom door in the same hallway. This demonstrates the "suck-out" theorem very well and makes my idea of adding a hallway door more of a necessity. Notice the improvement in SPL across the spectrum, and it's just from closing a few doors! This was the first step in today's journey. The results I spoke about above were with a couple more tweaks. So now I'm going to pickup a door for my basement stairway which had its door removed prior to me buying the house, so I'm just going to put it back to how it should be.

[leonski]

Dec 15, 2020 22:33:24 GMT -5 ttocs said:

Dec 15, 2020 21:21:53 GMT -5 @tllfkacn said:

Forget any hole in the wall.  Any change in the room can and many times does effect your system's sound.  Examples, open or shut room doors, carpet or no carpet or throw rugs, finish on the walls, moving furniture, ceiling surface, placement of speakers (on floor or stands, against wall, in corner) and on and on.

Put the drill away for now.

I'm putting the drill down . . . . . and stepping away from it . . . .

It's HI-LARIOUS that you mention doors to other rooms and such, because just today I did just that!

There is a hallway that has 3 bedrooms and two bathrooms. The hall has no door, and some doors are normally closed, others normally open. I closed some doors and noticed a difference in REW. Then I closed off the hallway with a sheet of MDF, again, difference. Then added MDF to one corner of the dining area (far left of system, same wall), got another difference. Took that MDF and the sheet closing off the hallway, then added two bales of mineral wool to the dining area corner, and another difference. Then played with a 2x4 absorb panel in the right corner behind the Right speaker and a double stack of subs, and another difference.

These differences are very noticeable and a tuning preference can be seen in the plots, if you need some of this - do that. In the end, it's a bunch of little things together that add up. Closing 3 doors, adding a 2x4' absorption panel behind the Right speaker, and moving the Right speaker and sub stack to the left made the improvement of closing the mouth of a wide/deep null from 60Hz-77Hz/35dB deep, to 59Hz-72Hz and only 15dB deep. That's a 4Hz and 20dB improvement. Pretty good for two free tweaks and one that costs about $8.

Below is a plot that shows the effect of what is so stupidly simple and free - Shut The Doors!
The red line is after closing two bathroom doors and one bedroom door in the same hallway. This demonstrates the "suck-out" theorem very well and makes my idea of adding a hallway door more of a necessity. Notice the improvement in SPL across the spectrum, and it's just from closing a few doors! This was the first step in today's journey. The results I spoke about above were with a couple more tweaks. So now I'm going to pickup a door for my basement stairway which had its door removed prior to me buying the house, so I'm just going to put it back to how it should be.
View Attachment

Well, since we are all 'confined to quarters' for the foreseeable future, I guess YOU'VE got your project lined up.
Just don't drive yourself nuts.     
Just for example?   You've noted a difference with closing doors.    Those a probably Hollow Core INTERIOR doors.     You'll get different (not necessarily 'better')  results with SOLID doors.     Years ago when I was noodling thru a dedicated room addition for sound, I specified a 36" EXTERIOR door be used.    Walls were to be 2x6 with each side NOT attached to the same stud.   Studs were to be regular 2x4 with basically 2 walls 'back to back' with room inbetween for sound absorbant materials.    
Stuff like that will have you up Late At Night and no amount of legal OR illegal 'relaxants' will help you sleep.     EVERY detail makes a difference.   Some such are built in as an original feature while others can be added later.     I'd build a dedicated room with NON-Parallell walls, for example.  And careful attention to the basic dimensions.......
Real professional room builders get a good sum for such advice and helps.    But THEY know pretty much what they are doing and won't have to go thru too many experiment / fail loops!

Hope this works out.    At some point, stop Measuring and LISTEN.    At some point what you measure may start making sense with what you HEAR.....Than YOU'LL be the pro!

[DYohn]

This is a good write up on room acoustics and includes descriptions of various types of bass traps, including Helmholtz traps.

www.acousticsciences.com/media/articles/trapping-bass-your-project-studio

[ttocs]

Dec 15, 2020 23:51:45 GMT -5 leonski said:

Dec 15, 2020 22:33:24 GMT -5 ttocs said:

I'm putting the drill down . . . . . and stepping away from it . . . .

It's HI-LARIOUS that you mention doors to other rooms and such, because just today I did just that!

There is a hallway that has 3 bedrooms and two bathrooms. The hall has no door, and some doors are normally closed, others normally open. I closed some doors and noticed a difference in REW. Then I closed off the hallway with a sheet of MDF, again, difference. Then added MDF to one corner of the dining area (far left of system, same wall), got another difference. Took that MDF and the sheet closing off the hallway, then added two bales of mineral wool to the dining area corner, and another difference. Then played with a 2x4 absorb panel in the right corner behind the Right speaker and a double stack of subs, and another difference.

These differences are very noticeable and a tuning preference can be seen in the plots, if you need some of this - do that. In the end, it's a bunch of little things together that add up. Closing 3 doors, adding a 2x4' absorption panel behind the Right speaker, and moving the Right speaker and sub stack to the left made the improvement of closing the mouth of a wide/deep null from 60Hz-77Hz/35dB deep, to 59Hz-72Hz and only 15dB deep. That's a 4Hz and 20dB improvement. Pretty good for two free tweaks and one that costs about $8.

Below is a plot that shows the effect of what is so stupidly simple and free - Shut The Doors!
The red line is after closing two bathroom doors and one bedroom door in the same hallway. This demonstrates the "suck-out" theorem very well and makes my idea of adding a hallway door more of a necessity. Notice the improvement in SPL across the spectrum, and it's just from closing a few doors! This was the first step in today's journey. The results I spoke about above were with a couple more tweaks. So now I'm going to pickup a door for my basement stairway which had its door removed prior to me buying the house, so I'm just going to put it back to how it should be.
View Attachment

Well, since we are all 'confined to quarters' for the foreseeable future, I guess YOU'VE got your project lined up.
Just don't drive yourself nuts.     
Just for example?   You've noted a difference with closing doors.    Those a probably Hollow Core INTERIOR doors.     You'll get different (not necessarily 'better')  results with SOLID doors.     Years ago when I was noodling thru a dedicated room addition for sound, I specified a 36" EXTERIOR door be used.    Walls were to be 2x6 with each side NOT attached to the same stud.   Studs were to be regular 2x4 with basically 2 walls 'back to back' with room inbetween for sound absorbant materials.    
Stuff like that will have you up Late At Night and no amount of legal OR illegal 'relaxants' will help you sleep.     EVERY detail makes a difference.   Some such are built in as an original feature while others can be added later.     I'd build a dedicated room with NON-Parallell walls, for example.  And careful attention to the basic dimensions.......
Real professional room builders get a good sum for such advice and helps.    But THEY know pretty much what they are doing and won't have to go thru too many experiment / fail loops!

Hope this works out.    At some point, stop Measuring and LISTEN.    At some point what you measure may start making sense with what you HEAR.....Than YOU'LL be the pro!

The doors are solid core. And yes, any differences are not necessarily good for my situation, just different.

What I got from that exercise yesterday is basically confirmation of what I thought might be beneficial, which is to close off the hallway and the basement stairs. I've been wanting to install a barn door for the hallway that would be normally closed. This is for privacy as well as for sound control - both ways.

Except for the last few weeks due to circumstances related to updating the sound system and work going on in the house, I listen all the time. I'm pretty sure you know from previous conversations that I like to tinker and test. So I make time for doing such things, especially when it involves questions floating around the inter-connected-web-of-computer-things which get answered with conjecture instead of repeatable, factual, measurement data. I have fun learning about "how" to test and measure audio and electronicals (Lisa Douglass on Green Acres), and then apply what I've learned to see how my system stacks up.

Not unlike the song lyrics by the Beatles: "I can't sleep, I can't stop my brain, you know it's three weeks, I'm goin' insane! You know I'd give you everything I've got for a little peace of mind."

It's all fun, it's all good.

[leonski]

I can't remember the last time I saw INTERIOR doors which were solid core. Maybe in a VERY old house? Even than, they'll be lighter than an exterior door.

Even the exterior door to my garage was hollow core....but Really Well Built and a PIA to cut up. It was replaced by a steel sheathed door.

Any way to skip the barn door and install a Pocket Door?? I personally like that 'finish', especially in a more modern home. Country may be another matter.

[ttocs]

Dec 18, 2020 14:54:58 GMT -5 leonski said:

I can't remember the last time I saw INTERIOR doors which were solid core. Maybe in a VERY old house? Even than, they'll be lighter than an exterior door.

Even the exterior door to my garage was hollow core....but Really Well Built and a PIA to cut up. It was replaced by a steel sheathed door.

Any way to skip the barn door and install a Pocket Door?? I personally like that 'finish', especially in a more modern home. Country may be another matter.

65 year old house. Even the bi-fold closet doors are solid slabs. The walls are gypsum/plaster, which is 3/8" gypsum board that are in strips 18" high (horizontally mounted) and have plaster applied to them. It was a transitional plastering method in place of using wood lathe. The gypsum/plaster is 1" to 1-1/4" thick, and really, really heavy, and wears out sawzall blades every couple feet of cuts. The scratch coat is similar to concrete. They used wire lathe in addition to the gypsum board at all the corners.

I'd love to pocket the hallway door!! But, it's a common wall for a bathroom and dining area, so that's a no-go. If I weren't concerned with eating up space I could build-out that wall, but every 6 inches counts in a small abode.

Couple more things about that hallway door idea. First is that the door will be closed all the time. The reason is so it doesn't block the Left Surround speaker recessed into that wall that I don't want a pocket door installed into.

The only other very reasonable solution is to keep the hall open and keep all the doors shut and work with room treatments that I'll be doing anyway. THEN see if closing off the hall is still a benefit, and if it is, deal with it at a later time.

[KeithL]

They most certainly do... or at least did... make solid interior doors.

My dad and I were finishing a room in the basement of the house where I lived about 40 years ago.

And we went to our local home supply / surplus store and bought a door.

This was not a wood panel door like most exterior doors.

It looked like a plain featureless cheap wooden interior door and was simply listed as a "solid core wooden interior door".

It was 36" wide, an inch and a half thick, and faced with normal looking unfinished mahogany wood...

I assume the interior was particleboard or some sort of dense fiber board; it was solid and it weighed about 100 pounds.

It felt like concrete when you rapped on it, made the wall shake if you closed it too fast, and was quite soundproof.

Dec 18, 2020 14:54:58 GMT -5 leonski said:

I can't remember the last time I saw INTERIOR doors which were solid core. Maybe in a VERY old house? Even than, they'll be lighter than an exterior door.

Even the exterior door to my garage was hollow core....but Really Well Built and a PIA to cut up. It was replaced by a steel sheathed door.

Any way to skip the barn door and install a Pocket Door?? I personally like that 'finish', especially in a more modern home. Country may be another matter.

[leonski]

Keith,
Don't doubt you for a second. But TODAY? First? Most interior doors are 32" or maybe 30" wide. And hung with TWO hinges (2(, not the 3 required of a door such as you describe.
Door to my Garage from the house? Very heavy / solid and hung with 3x hinges while being 30" or maybe 32" wide. My ENTRY is indeed a full 36" door.
Hinges are important. I recently used a pair of ADA compliant, high-offset hinges to build a lid for my BBQ box. The main feature is a slightly tilted lid and total wrap around 3" lip so water CANNOT enter
at all. I made it tight enough to have an air-spring closure, so it won't even slam......I've never even found a BUG inside this 30 cubic foot box. If I made the no-weight-limit version, it'd make a wonderful
enclosure for a sub. And would take two men and a boy to move.
the few othr interior doors are hollow core and cheap.
Might be worthwhile to see if the framing will support a heavy door and try to make a slightly quieter room?
When my dad built a recording studio, he hung a sheet of LEAD on the door between control room and studio. Other features Too Numerous to mention, but this studio portion was very inert. The walls were
a foot thick or more, in spots....over the existing structure which was an 'industrial space'.....This was when an OTARI Reel-2-Reel in half-track was a good way to finalize the mix. You may still be able to find one, new.....?

[marcl]

Dec 3, 2020 19:55:00 GMT -5 KeithL said:

It's also worth noting that a Helmholtz resonator is an organ pipe...

It's also the thing that makes a hooting noise when you plow across the neck of a bottle...

(It would be more accurate to say that both bottles and organ pipes are Helmholtz resonators.)

In other words, a resonator resonates (rings) at a particular frequency, which means that it can attenuate energy, or it can do the opposite...

It's only going to act as a bass trap if you tune and position it precisely to counteract something going on in your room.

And, if you get it wrong, then it's going to make things worse instead of better.

So you really have to know what you're doing to get a good result.

Dec 3, 2020 16:13:09 GMT -5 DYohn said:

Yes, a hole cut into a wall can become a Helmholtz resonator bass trap. It is a technique commonly used in cinema design (resonators built into seat riser platforms.) The trick is to design it so it becomes functional in your room. Most spaces lack sufficient low frequency energy to make them very meaningful, but in a space with lots of excess bass energy or large room modes they can work. You need to design them for the frequency band you wish to attenuate.

Several years ago PSAudio got some new (30 year old) Infinity IRS speakers and decided to renovate their main listening room.  They did 7 YouTube videos on the design and construction.  One feature was they got their engineer to design corner Helmhotz resonators with tunable ports.  Entertaining video of pumping pink fluffy into the cavities.

Then they proceeded to construct the room from triple thick sheetrock making the walls and ceiling extremely rigid and exacerbating every resonance issue to the max.  In the 7th video, they admitted the Helmholtz resonators were only slightly effective (2 decibels!), they still had peaks >10db, and only managed to make the system listenable by moving the speakers well out away from the front wall, and moving the MLP around.

www.youtube.com/watch?v=NPazywXrqJo

[leonski]

So Much for 'The Perfect Room'......
I've considered multiple layers of sheet rock but not on ALL walls. On adjaceent walls, yes, but only 2 of the 4 main walls. Celling needs another idea.
Non-Parallel walls? Maybe that would help. And staggered studs so the 2 sides of an interio wall were not BOTH secured to opposite sides of the SAME stud....
That would make it a drum head.

Trouble? Well, Yes. Lots of interesting things can be done for NEW construction. But in a renovation or simply making a listening room? Options close down....

[Deleted]

I was noticing today every Chipotle Mexican Grill has what seems as acoustical room treatment: