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The Nightmare Before Labor Day
The Nightmare Before Labor Day
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Old 13th July 2021, 05:44 PM   #1
Patrick Bateman is offline Patrick Bateman  United States
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Default The Nightmare Before Labor Day

The acoustics in my new home are horrendous and I have to figure out a way to deal with that, or else find a new hobby.

Click the image to open in full size.

This is my old place, in San Diego. The main room is really wide and deep and the ceiling is a standard height.

Click the image to open in full size.

Four years ago, I lived in a tiny condo, and one of my top requirements when I bought a house was a big living room. I had to sell my Gedlee Summas in 2016 because my old condo was way too small for such a big speaker.

Click the image to open in full size.

Click the image to open in full size.

The living room in my new place is about as large as the old place, but the ceiling is nearly 30' high. When I bought the place, I had daydreams of a space where there would basically be no 'ceiling bounce' and I thought this room would image like a dream.

Instead: it's an acoustical nightmare.

So many issues with his space:

1) Due to the fact that there's absolute nothing between the speakers and upstairs, you can play music in the living room and it's about as loud upstairs as it is downstairs.

2) Due to the fact that there's nothing between the kitchen and the living room, anything that's going on in the kitchen interferes with the living room. Last night we had guests over and I had to put my chair a meter away from the TV, just so I could watch a show.

3) Every surface in the house is flat and reflective. It's like putting speakers in a warehouse.

So I gotta come up with some way to tame this space, acoustically.

My initial idea was a CBT of Unity horns. The idea that I had, was that you could array a vertical series of Unity horns and get a beamwith that's 30 degrees or less. The idea was that I could listen to music or watch a movie without bugging everyone else in the house. After discussing this on the Facebook group, I came to the conclusion that an array probably isn't ideal. The problem with an array, is that it doesn't control directivity to a low frequency. For instance, an array that is one meter tall will control directivity to about 340hz. But nearly all of the issues that I'm having in this space are at low frequency and ultra low frequency.

For instance, on Monday I was trying to watch "Heat." In the movie, the action sequences are about 20dB louder than the dialog. This creates a catch-22:

* if I lower the volume to accomodate the action sequences, the dialog is completely unintelligible

* if I play the movie at a decent volume level, the action sequences irritate everyone in the house, particularly if people are sleeping. My wife's complained about this, and I've even had guests complain about it. (My guest room is on the opposite side of the house, about as far from the speakers as you can get.)

The obvious solution would be a dedicated home theater in the basement. Which would be great if I lived where homes have a basement. In Nevada, there's exactly one house with a basement, and it's built to withstand a nuclear bomb:

Las Vegas House With Doomsday Bunker for Sale

Although I'll admit that buying a fallout shelter and installing Unity horns in it would be a very Patrick Bateman thing to do, I don't particularly like their decorating choices.

So I have to come up with a plan for this space...
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Old 13th July 2021, 05:52 PM   #2
Patrick Bateman is offline Patrick Bateman  United States
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I haven't heard the Dutch and Dutch speakers. But the reviews are great, and a cardioid might solve a lot of problems.

A few years back, I was measuring some speakers. My measurements looked strange; the frequency response was about right, but the highs were rolled off. After some fiddling, I'd discovered something kid of amazing:

The reflected energy from my speaker was nearly identical to the incident wave. In other words, the reflection off the wall wasn't much different than what the speakers were radiating. What had happened was that I'd set the gate wrong in my software, and I was capturing the reflection, but not the original sound. But the reflection was so strong, it was basically the same as the original sound.

So I think that's part of the reason that my new room sounds so atrocious; there's a lot of big hard surfaces and they're acting like mirrors. An even bigger issue is that there's nearly no attenuation, due to the space being so open. For instance, someone in the kitchen downstairs is stirring their coffee right now, and I can hear it as clear as a bell, even though it's on the other side of the house.

The radiation of the mid and high frequencies isn't the worst thing in the world, but the radiation of the low and ultra low frequencies is a huge issue. It basically makes it impossible to listen to music or TV at even a modest volume.
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Old 13th July 2021, 05:53 PM   #3
Patrick Bateman is offline Patrick Bateman  United States
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Keyser wrote this:

2-way: Waveguide + Cardioid-like

"The resistance enclosure works very well, but it requires a lot of experimentation with locations of the openings and damping material to get optimal results. The heavier, thicker fibreglass panels tend to work well, although it might pose a health hazard. This thread describes my first experiment with a resistance enclosure. Much better results are possible than shown here. A box with openings to the side but none in the back works well even when placed very close to the wall behind it.

A damped U-frame works better at lower frequencies, but as has been said above the exact amount and kind of damping material have a great effect on how well it will work. It requires some room behind the box to work well.

A cardioid composed of a combination of a dipole and a monopole should work fine. You have to equalize both to the same response, because otherwise their phase-relationship will not be the same. I think it should be possible to place this configuration quite close to the wall behind it, because the cancelling sources are in the same vertical plane and cancellation starts right there at the sources - not at some distance behind it, as is the case with a U-frame and a cardioid that consists of two monopoles.

A configuration with two monopoles in line can work very well too. You place one sub behind the other, you invert the phase of the rear sub and add a delay that corresponds with the propagation delay of the sound over that distance. This should work well up to about the frequency where the distance between the subs is about a quarter wavelength.
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Old 13th July 2021, 06:07 PM   #4
Patrick Bateman is offline Patrick Bateman  United States
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I am no expert on cardioids or dipoles. Based on my limited understanding:

Click the image to open in full size.

In a dipole, you get a null at 180 degrees off axis, because the front and the back are out of phase.

Click the image to open in full size.

In a cardioid, you get significantly lower radiation to the sides AND the back. The front band back are still out of phase, but the radiation level from the back is attenuated.

IE, in a dipole you have a perfect null at the sides, because the radiation from the front and back is identical and out-of-phase. In a cardioid the radiation isn't 100% attenuated because the SPL of the front and the back is not identical. If the back side is radiating 100%, you'll get a perfect null to the sides. The less that's radiated from the back, the more output you get from the sides.

At the same time, a cardioid will generally produce more bass than a dipole.

For instance, if you have a woofer that's playing 200Hz and it's a dipole, you'll get a perfect null at the sides. At the front and the back of the woofer, you're going to have less output, because the front and the back are out-of-phase. The output level is complicated by pathlength. 200Hz is 1.7 meters long, so when the pathlengths between the front and the back are about 0.425 meters long (16.875") the two wavefronts won't null each other out completely.

In other words, as frequency rises, the front and the back won't null each other out much, because the difference in pathlength prevents it. Conversely, the front and the back WILL null out a lot, when the frequencies are low.

Going cardioid reduces that a lot, because the energy radiated by the back is attenuated. That attenuation could be accomplished passively, using fiberglass attenuation or rockwool, or actively, using a second woofer and DSP delay.
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Old 13th July 2021, 06:24 PM   #5
profiguy is offline profiguy  United States
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I've been in your situation and tried many (temporary) affordable things to fix this sort of problem without considerable or acceptable results.

(As you already know) Your biggest issue isn't the immediate listening space but rather the reflections and hash coming black from the whole rest of interior. The best solution IMO and experience is to isolate the listening space acoustically from the remaining house interior. You need some sort of barrier between the two. Even something like a sliding door will isolate most everything but the low end so that the rest of your household won't be overwhelmed by the sound spillover. An accordion style separation wall is another option, again, not always an option visually or practically. Obviously the best solution is a permanent staggered studded sheet rock wall, but that may not be an option either.

I'm an acoustician by trade and have struggled in my own living spaces, simply because I didn't want to spend the money and time to do the necessary modifications. I finally moved into a single story place with tall vaulted ceilings and concrete sub floor, which is just amazing by itself without any treatment other than wall hangings and corner absorbers. I would highly recommend doing some more research and reading on this - Master Handbook of Acoustics by F. Everest.
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Old 13th July 2021, 06:30 PM   #6
profiguy is offline profiguy  United States
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Just read your post on the cardioid sub setup. It can be done and it's very effective, but its not cheap. We use this in alot of classical and theater live venues with solo vocalists and acoustical instruments. Its really the only way to focus the low end where you want and run higher SPLs in a narrow room configuration.
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Old 13th July 2021, 06:39 PM   #7
mountainman bob is offline mountainman bob  United States
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Hey Patrick,
My situation is fairly close to the same with open floor plan with open loft except my ceiling slopes from 9’ to 24’.
One day (hopefully soon) my plan is to build some 10” mtm with horn tweeters over 15” bass modules with the woofers as close to the floor as possible to avoid bounce.
The idea is to keep the vertical polars in check which in my case will be around 20 degrees…….bass, I’m just hoping for the best.
Might want to consider that?

Last edited by mountainman bob; 13th July 2021 at 06:42 PM.
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Old 13th July 2021, 06:43 PM   #8
puppet is offline puppet  United States
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Man what a waste of space. Bright side is you've got plenty of room for a loft.
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Old 13th July 2021, 07:29 PM   #9
mark100 is offline mark100  United States
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The Nightmare Before Labor Day
Hi Patrick, a big open room like that is going to have long RTA60's across the spectrum.
Do you have a RT60 plot?

My bet is mid/HF/VHF are the bigger problems than LF at listening position, almost certainly for music clarity, speech intelligibility, and watching a movie. I'd work on it first with absorption to match your RT60 results.

The ladder in the room picts looks to be a standard 24ft extension with 12ft sections. On that, I'm guessing your room is a maybe a bit over 20ft high.
Lower than 30ft, but too high too reach anything.

Probably the first thing I'd do is put some heavy drapes on the upper windows all around. Motorized if at all possible.

Wall hangings; rugs, or rigid fiberglass panels on thin ply for hanging, wrapped in lady's choice of fabric
Anything you can do on top the usual furniture, floor rugs, etc.

I'll repeat myself in saying i'd work of the high end first....then see what the low end looks like.

Sadly, tall residential size rooms usually suck acoustically until well damped ...takes a ton of work to tame them. The hand clap, whistle test, etc....kinda say it all until tamed.
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Old 13th July 2021, 08:25 PM   #10
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by mountainman bob View Post
Hey Patrick,
My situation is fairly close to the same with open floor plan with open loft except my ceiling slopes from 9’ to 24’.
One day (hopefully soon) my plan is to build some 10” mtm with horn tweeters over 15” bass modules with the woofers as close to the floor as possible to avoid bounce.
The idea is to keep the vertical polars in check which in my case will be around 20 degrees…….bass, I’m just hoping for the best.
Might want to consider that?
That was my initial thought, to get the vertical directivity as narrow as possible, to keep sound from spilling into the upstairs area.

The more I thought about it, the less I liked it.

Click the image to open in full size.

For instance, Kimmo Saunisto was getting about 6dB of attenuation to the sides and to the back using a cardioid. Ideally I'd like to get attenuation of about 10-20dB, but Keyser's thread seemed to indicate that you could take things a step further by combining room treatment AND a cardioid. And I'm willing to do that, I just can't go completely crazy since this IS the living room.

On a side note, does anyone know what happened to all his projects? They seem to have evaporated off of his web site:

kimmosaunisto.net - Error 404: Not Found
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