Room Acoustics and Bass Traps

[Sigmund451]

Ive struggled with this problem. First I had guitar problems, then a few cabinet problems. Those are solved

Now I am sure my practice space is killing my low E string notes.

4-7 frets do crazy things. I assume Im getting wave cancelation. Through headphones everything is fine. Notes sustain.
Depending on where I put the amp and where I sit certain notes just go THUD! Zero sustain and a fairly ugly sound.

I messed with it this morning and found a place to put the chair and amp where its acceptable. However, its a also my office and work space for other things. Their location is ok but not really ideal. So basically Ive moved the dead zones around a little.

SO...If I build and install real bass traps (over 6 inches thick suspended where there is an air gap should it fix this problem?
The squishy foam crap helps with room echo but of course does nothing to address the bass.

I understand no one can absolutely answer this question since every space is different but Id like some thoughts. I dont want to go to all the hassle of building these things if there is little chance of them working.

For some odd reason it is worse on my acoustic carved archtop vs my laminated guitars. Additionally, using the Dearmond setting on my Armstrong single coil makes the problem show up more than when using the full p90 setting. I guess its a different set of frequencies flying around the room and more easily disrupted

I just rememberd too. I must be getting some serious cancelation since the low E as it travels from my amp has far LESS volume than other strings...to the point where I have the pole piece raised higher than the 5th string. Not the case with headphones and when Im move the amp to a big room.

[Bob_Ross]

First question: What are the dimensions of this room?

Second question: How far down this rabbit hole are you willing to go?

[Luicaz72]

The fact that the problem goes away in a larger room pretty much points to room acoustics as the culprit.

[Sigmund451]

French houses have the worlds worst acoustics. Every surface is extremely hard and reflective. Its plaster over smooth block on floor and ceilings. A fair amount of glass windows and doors too

Im willing to go down the rabit hole but not with heavy computer programs and math.

Basically Im planning some 8 inch deep bass traps suspended from the ceiling and some on the walls. Its a dedicated multi workspace so it doesnt have to look like a living room.

Im not looking for studio quality but I really dont want to deal with playing a guitar that literally sounds broken.
I dont want to tell you how many adjustments I made on the guitar to fix the problem

The room is definitely the culprit. If I sit in one place one note sounds glorious and another bad. The bad notes move around as I move around. I tried to find the perfect place to sit and put the amp but within the constraints I have there are none.

The room is about 11x12.5 with 8.5 ft ceilings. There is a long set of counters and upper cabinets along one side which more or less makes the room 12.5 x 9 ish

[GuyBoden]

I've got 20mm thick foam flooring and 1 meter square, 20mm thick foam tiles on a few of the walls. Floor length thick drapes on the windows.

The sound is now ok.

[Little Jay]

We treated our music room with ‘acoustic’ wall paper (just thick rubbery wall paper), acoustic panels on the ceiling beams and rugs. It sounds fantastic: no unwanted reflections but also not too dry and dead. What you don’t see in the picture is the book cabinet in the corner and in the drum booth, a book cabinet makes a fantastic bass trap!

[Bob_Ross]

Basically Im planning some 8 inch deep bass traps suspended from the ceiling and some on the walls.

Bass traps tend to be more effective if they are located in the corners -- either wall/wall corners, or wall/ceiling corners. Get rectangular traps and have them straddle those corners, leaving empty airspace behind them. If you can get triangular bass traps, put those in all the trihedral corners (where two walls meet the ceiling) also.

The room is about 11x12.5 with 8.5 ft ceilings. There is a long set of counters and upper cabinets along one side which more or less makes the room 12.5 x 9 ish

Those cabinets are invisible to low frequencies, so 11 x 12.5 x 8.5 are the dimensions you should go by. If you plug those dimensions into a Room Mode Calculator, it confirms that there's a tangential mode right at the fundamental (and every partial) of your low E string, also a strong oblique mode at the 2nd harmonic (~165Hz), but that the worst axial modes are around your low C (3rd fret, 5th string).

If you were buying frequency-specific bass traps -- e.g., Helmholz resonators -- you could use that information accordingly...but frankly, for small room acoustics it's better to use broadband bass traps, so 4-8" of absorptive material straddling all corners should make a significant improvement.

[benhatchins]

Room acoustics really make a huge difference, especially for bass response and clarity. Even small changes like bass traps or furniture placement can transform how a room sounds. It’s one of those things you only notice once you start experimenting. I was looking at Montage Furniture Services reviews earlier and ended up down this audio rabbit hole instead. Interesting how sound behaves in different spaces.

[rpjazzguitar]

Ive struggled with this problem. First I had guitar problems, then a few cabinet problems. Those are solved


I just rememberd too. I must be getting some serious cancelation since the low E as it travels from my amp has far LESS volume than other strings...to the point where I have the pole piece raised higher than the 5th string. Not the case with headphones and when Im move the amp to a big room.

So, low E has less volume and carved archtop is worse than laminate. And, you don't hear it on headphones. Changing position makes a difference.

So, some notes are feeding back more than others.

If the low E is too soft, what will the bass trap do? Will it leave the low E alone and lower everything else?

I considered bass traps when I set up my music room. Consulted with a couple of bassists. Concensus was that they could solve the problem by turning down. That's worked fine for 12 years. I do have four good sized acoustic panels, commercial style carpet and drapes. Room, which is about 11x17 sounds fine.

If I was faced with this problem, here's what I'd try first. I'd bunch up some random foam and plug the f holes for a few minutes. Just to see what difference that would make. If it worked, I'd remove the bunched up foam and look for something like Doug's Plugs.

[Sigmund451]

That brings up some interesting points.

The Low E string is the worst but the real problems are between the 4th and 7th fret.
A thud...zero sustain issue happens in various spots depending on the location for sitting and the amp.

i have shoved a cloth in the F hole and it goes away. Does this mean the problem is kind of an anti feedback issue...sound waves/pressure entering the cavity and messing up/killing a note?

I do get some staning wave issues of louder low notes but the biggest issue is the "Thud".

I will also try down tuning a little.

Thanks for the suggestions. I will report back after some experiments.

[Sigmund451]

@Rpjazzguitar.

I think you nailed it.

The room does have lots of reflections as well as beaming sound from the main speaker.
I think its entering the gutiar and doing all sorts of crazy things.
Ive been experimenting with where the reflections come from and a little painters tape to cover various parts of the top f-hole.

Its seems to make a big difference just covering a two inch section. I dont know if its blocking the incoming waves or if its cutting back on the vibration in that area. Whatever the case it seems to even out the notes along the low e string scale and offers appropriate sustain.

More experiments to follow. I do think the room needs help but addressing it at the guitar is a whole lot more direct than fixing wave reflections.

If the room was a dedicated music room Id be able to rearage more but the way it is offers very limited options.

thanks

[Sigmund451]

Looks like I will be making an F-Hole Plug. Covering most or all of the upper bout hole comes close to fixing every problem. Time to order some EVA foam. Meanwhile, I will continue to experiment.

I have no idea what the problem is called but I call it anti-feedback. As opposed to boomy infinite sustain I get notes with a thunking absence of sustain. Its like wave cancelation inside the guitar body. Weird stuff sound is.

I will still treat the room a bit but Im not confident that it would fix every problem. At least now I have a solution at hand if it doesnt.

[Bob_Ross]

The Low E string is the worst but the real problems are between the 4th and 7th fret.
A thud...zero sustain issue happens in various spots depending on the location for sitting and the amp.

i have shoved a cloth in the F hole and it goes away.

First rule of troubleshooting is to isolate/eliminate variables. Is it the room, or is it the guitar? Easiest way to determine that is to go play that same guitar (with the same amp, etc.) in another room.
Do those sonic anomalies still exist? If so, the problem is your guitar, not the room, and no amount of bass trapping or sound absorbing materials will fix it.

They might fix other issues though.

[Sigmund451]

In a differerent room different issues arise. Of course that room is also terrible acoustics.

It appears that it may well be the interaction of the guitar with the room. As I move to different spots in order to minimize sound entering the guitar from the f-holes as well as directly hitting the top the problem notes move as well. Sometimes I can find a sweet spot where it only matters a little.

What I do know is that if I put blue tape over the top hole the problem almost every tonal problem vanishes. I put it on as lighly as possible to minimize dampening of the top around the hole. in a small room with very hard surfaces its really difficult to move much. The problem exists at low practice volume and persists equally if the volume is increased.

Im starting to think that the room itself is not canceling freqencies but instead bouncing them around so they flood the inside of the guitar and raise hell. Acoustically, with my ears to the face of the guitar the notes are very pure. And again, neither laminate guitar is effected...of course there isnt much top vibration going on with plywood.

When I cover the F hole the notes on the low e are louder and more in keeping with the volume of the rest of the guitar.

And finally, when I move a few thick cushions to select locations in the room(some not convienient for normal use) the impact is greatly minimized.

This leads me to think Im practicing in a psychotic room.
French houses are about the eqivalent of a bomb shelter when it comes to acoustics.

[Bob_Ross]

In a differerent room different issues arise. Of course that room is also terrible acoustics. ...[snip]... This leads me to think Im practicing in a psychotic room.

Take the guitar outdoors and play it in your backyard or the middle of the street as far away from your house as possible. Still hear those sonic anomalies?

[Sigmund451]

hahaha!

[stedtale]

I've been at a couple studios recently that use 16-20inch diameter, 1.5-2in thick fiberglass pipe insulation section with a black table cloth draped over them. Simple and very effective.