New Environment Nightmare - Tone Generator - Argh!

Loudspeakers
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I figured you audio-nerds may appreciate an audio horror story. Please read late at night and in the dark… yikes!

I just moved to a new home… my downstairs is all mine! Butt… always that big butt in the room… the environment is turning out to be an acoustics nightmare. The first issue I had is connecting my Directstream DAC across the room to my computer via a long USB cable. Solved with an iogear powered USB extension cable. I have some stick on conduit on order… will run the cable on the ceiling-wall interface as there is a wall of glass sliding doors to deal with. Of course the fidelity of this long cable… well forget it, I need to get the signal across the room above all else. Remote USB connection update? Wireless connection?

Butt… here we go… I started playing music and hear a multitude of problems… The system is way too forward, hard, and lacks bass. So I redirected my PC’s audio out to the PS Audio drivers (usually bound to foobar) and used this on-line tone generator - and beheld the horrors:

https://www.szynalski.com/tone-generator/

Boy is this thing handy. Before I used various CDs with sweeps and selected frequencies and such but this generator is all you need. What did I learn? Whoa! I was getting massive buzzing, vibrating, and yes, howling… from… somewhere… where? Well I found it was coming from my fireplace. The darn thing is not the old fashioned system of heavy cast iron placed into brickwork. No, it is some sort of cheesy sheet steel cabinet with thin heat-brick things. The damper is a round “lid” that gets pressed into a round hole up inside the thing. This is just crap. The home was built in 1983, and I guess it was around then that these crappy systems were installed into homes.

Well the whole internal firebox resonates across a whole range of frequencies. Just horrible!!! Unbelievable actually. I just spent about 2 hours trying to dampen the noises. I plan on never using the stupid thing (my electric piano sits in front and across the fireplace) but I don’t want to damage its internals for obvious reasons. In short, I jammed a metal pole in there kind of pushing/bending its internals… then finally, I took some small real, wood logs and kinda rammed them up there to add a dampening mass to the various panels and joints. Sheeeeeesh!!!

Well it is mostly quiet now… for now. I’ve learned from chasing these resonances down they can return in surprising ways. Think the rattles and squeaks in your car. (BTW, the easist/fasted way to find those squeaks and rattles, is to use a tone generator on your phone piped through your car’s stereo… the evils will just pop out and you can get to work eliminated them).

How does the room sound now? AWFUL! starting at around 220HZ, the volume appears to drop rather linearly down the frequency scale. Anemic is a good way to describe the sound… just no bass to make it short. The good news is my Focal speakers can generate an audible sound down to around 25-30 hz or so… so the sound is there. Now how to get it out?

Stay tuned… I will be posting more as I progress.

How is the imaging? Kind of like a charcoal smudge on a black wall. Yea, that bad. The wall of glass on the right side of the room is just… argh…

Peace
Bruce in Philly (now in Atlanta)

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We had a fireplace that wasn’t getting used and we filled it with fibreglass batt insulation as a temporary measure. Removing the fireplace would have affected resale. This works well to insulate and dampen the sounds.

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ARGH! What a headache.

I hope you get things sorted out.

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I lived in ATL area for 5 years. The builders had no regulation and cut corners everywhere. I had the worst time finding a home without issues. There were none. I saw stuff like a master bedroom bathroom floor that dropped 4 inches over 10 feet. Wood flooring crowned in center of rooms. Whole exterior walls with no insulation.

A coworker whose new home had no tarpaper under shingles that were stapled directly to underlayment. Sidewalls without moisture barrier. Hacked up wiring jobs and terrible HVAC installs. Synthetic stucco homes with trapped moisture.

Then there is Radon gas issues to deal with. Have the home tested. I had to install a system to ventilate under basement slab.

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Ha! That is consistent with what some of my relatives told me when they moved down here ten years ago. I found the home inspector that looked at our home missed… like everything. Not high quality work. Fortunately, I found a pretty good home… so far.

So I am not too upset about not using my fireplace… I worry it will torch the home… although the house was built in '83 and it didn’t burn down yet.

Anywho… now to tame these awful acoustics.

Peace
Bruce in Philly (now Atlanta)

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Sounds like a serious project you are up to. Are you planning to make acoustic measurements e.g. with REW? And are you looking into acoustic treatments? If this is your room you have visual freedom even for „ugly“ things like big bass traps and hanging broadband absorbers from the ceiling.

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The next thing is to place absorption at a key point along the glass wall to the right of the speaker. I placed a light on top of the speaker, then sat down in my listening position. Where I see the light in the glass is where I want to put a panel. I suspect only about two feet wide will do… floor standing up to about my shoulder height ought to do it.

The point where I can see the light in the glass is the first reflection from the speaker to me. I know from experience if I can kill this, I can probably help with most of my problems. At a minimum, it will improve imaging and make the sound more relaxed and comfortable. When sound reflects that “soon” and directly to the listener… well is is an echo, or more accurately a very near-time reverberation… that slap-echo is incredibly destructive to fidelity.

If you read up on Paul Klipsh’s work on his corner horn, you can see he uses the reflecting wall as an amplifier. I believe this glass wall, just 2+ feet from the speaker is acting like Paul’s amplifier… and an amplifier with a very short-term time delay. Blech.

Now to get some sort of thing to put there.

To improve, or accentuate the lower registers, I moved the speakers back towards the wall. This helped tremendously… but I still have work to do as the back wall is not flush… it has the fireplace sticking out and my keyboard and associated equipment to deal with. More work needed.

Peace
Bruce in Philly (now Atlanta)

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I used to plot sound pressure levels on graph paper with an old Realistic SPL meter. I would feed sweeps and tones from a collection of test-CDs I have. This was a great learning experience, but now I just use my ears and that tone-generator in my post above.

Go ahead and give the generator a try. Don’t go up over 10K hertz as it just plain hurts. Put the volume up a bit, not loud but slightly above average. This will accentuate the evils. Now slide the slider down and up… you will hear the volume jump and suck out. These are evils that you must tame.

Regarding bass treatment like traps: I don’t have a problem with bass, I have no bass. For this I need to reinforce it and there are few options other than try to get the speakers closer to the back wall but that is really tough given my keyboard and the odd shape of the wall and fireplace.

I used to be a zealot for nuking tone controls, but after being an audio nerd for a long long time and living in different environments, I want them back.

Peace
Bruce in Philly (now Atlanta)

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That tone generator is truly a nice one.
You find lots of amazing tools and tests also here: Free Online Audio Tests, Test Tones and Tone Generators - check it out.

And yes, ultimately it’s about your ears and there’s no more definite measurement device under the sun.

REW is just another amazing tool (for free, besides the calibrated microphone you’ll need to buy – around 100 USDy – or borrow), that allows you to accurately measure and see various aspects at once. You’ll get the impulse and frequency response, waterfall (decay times), spectrogram, and even a room simulator. That was e.g. very helpful for placing my sub in my living room, as I could virtually place the sub anywhere and see a simulation of the bass response at my listening position:

image
image1287×808 175 KB

You could e.g. use that simulation part alone to see how different distances of your speakers to the front and side walls effect the bass response in your room.

I used the REW measurements to create a convolution filter (todays tone controls) to optimise the bass response in my room. It’s easy to A/B that and it makes a huge difference.

Anyhow, REW (Room EQ Wizard) can be another rabbit hole and you can easily get lost in there. There are many other approaches that are valid and working, too. I just wanted to make you aware that there’s a very cheap scientific solution that gives a lot of detailed insights what the issues in a room are and to treat them specifically, now that you already found and fixed the most annoying fireplace thing.

Regarding the bass traps: It’s a common misbelieve that bass traps will give you less bass. The opposite is true.

The logic is: Your speakers are fine (you know that from your old room), they deliver all that great bass you want hear directly. So if you would just listen to them, you would be fine. But there is this room you are in… Certain bass frequencies are bouncing back from the walls (and the floor, and the ceiling) and are creating standing waves or room modes. These have nulls and dips, where these bass frequencies are either way too loud or non existent.
Bass traps do not alter the direct sound of your loudspeakers at all. They take out energy near walls, which results in less reflected energy, which 1. lowers the amplitude of standing waves and 2. shortens the reverberation time. Both effects are greatly desired for a better sound in a room.
In a nutshell: you can not have too many bass traps in a room, the more the better. (And yes, you need to make sure that you are not overdamping the higher frequencies which would make a room lifeless. But there are many solutions for that concern.)

From what you describe about your room, tone controls will not be the solution. It’s first optimal placement of the speakers, then optimal listening position and then room treatment. Then come tone controls/EQ/filters. Good luck!

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Excellent post. Thank you.

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Good stuff, thanx. I will run some bass tests. That is pretty easy… use the generator and start down low… actually low mid-range… male voice area… and just walk around the room. If there are wave cancellations and accentuation going on, I will hear them right away. Walking around the room, I will hear the tone volume rise and fall as the waves cancel and reinforce each other.

You know, something I started to realize a while back, but I prefer deader sounding rooms over lively ones. Now a real dead room is just as bad as a lively one. One place I lived… for only one year as I couldn’t fix the horrible acoustics (too lively)… I even tried hanging blankets on key walls and places. Yep, that fixed the liveliness but created a whole set of problems. So I think the optimal room characteristics… if you can make such a generalization… is a more dead than live room with good diffusion/scattering of sound. Direct bounces are really bad… better to slightly damp and scatter. After owning two sets of Magnepans over the years, I learned they sounded best on the long wall and not the ends of a room as they sounded best when the side walls were far away. I think this is true of any speaker regardless of design… but we can’t always force a living space to be what we want.

Oh well… back to work.

UPDATE: I just made a major improvement. An experiment as this is only temporary. I put a light on my right speaker that is located only 2 feet from the side wall… a wall of 90% glass floor to ceiling. Then I go to my listening position and I can see the light in the glass. This represents the point of reflection (must be a science name for that).

So, I took a large flat-screen TV box… covered it with a thick blanket and leaned it up against the glass where the reflection was. I raised the box up one foot from the floor so it stands about a foot higher than my speakers. WOW… what a difference. The sound is now way more comfortable. On super-imaging recordings, I can hear imaging… well sort of… the image locations are still smeary and in the wrong places… and the balance is still shifted right showing the glass wall is still a major factor. Butt… oh that big butt… it is a huge improvement. At least I can play music without my ears bleeding.

Onward…

Peace
Bruce in Philly

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