Poor man's acoustic reflector!

[OPJ77]

Originally Posted by RussellHawaii

I’m very interested in this subject. At home I have two places that sound extra good. One is in front of a curved hallway (yes we have a curve in our hallway) where the sound reflections surrounds me. Another is simply in an uncluttered hallway.
The music room is mostly wooden. When I removed the main carpet the sound dramatically improved.
Long ago at school I’d play in a stairwell. Long reverb times!
I’d like to develop a performance space that maximizes such reflections, so that acoustic players and a modest audience can enjoy pure acoustic music. I actually have the opportunity to create such a space in a year or so, if I can come up with a plan.
I assume parabolic reflectors are ideal….I wonder if any are available commercially.
I realize this is what many performance spaces did in the old days. I also realize there could be too much reflection, and for loud sounds one must have some absorption, but for acoustic guitar and voice I cannot really imagine that!
Any further info is welcome. RFTinkerer’s article reference above was helpful regarding materials.

What is a parabolic reflector?

[KevWind]

Originally Posted by fitness1

For years I've been "evaluating" guitars by playing against a wall - probably 18" or so away is optimal for most guitars.

I was just sitting here watching golf and looked over at my laptop stand - and I realized it adjusts up and down and horizontally and vertically. When you get it adjusted just right, it reflects the sound directly back at your mellon

To my ear, it actually sounds better than against the wall (more natural with less 'boom'.

I just spent an hour or so playing the Revival dread against it and it talked me right into keeping it for a while longer until we become fully 'acquainted"

This is the kind of stand I'm talking about - like 46 bucks at Amazon....

I definitely think you should keep the Revival a while longer
That siad::
Hate to be the Debbi Downer here but something to think about : While reflected sound can often be to fun to hear.... I would never attempt to "evaluate" using it,,,, enjoy yes, play around with it yes ,,,,,,evaluate no..

Because.......it is an "Artificial" type of sound and is not really "Natural" . The only "natural" sound would be with no reflections, that is to say, the sound goes from the soundboard of the guitar to you ear uncolored by any reflection.
In fact if you step back and think about it, using close reflection is more or less a different version of using a reverb or delay effect. Just sayin'.

[OPJ77]

Originally Posted by Howard Emerson

A few years back I channeled my 10 year old self to satisfy the old guy that occupies the current premises, and I bought this. It works really well!!

Flexible Flyer Metal Snow Disc... https://www.amazon.com/dp/B0006N8WYM...p_mob_ap_share

Regards,
Howard Emerson

This is very intriguing. I wonder painting it with something thick like plasti dip would tame some of the sound reflecting back.

[fitness1]

Originally Posted by KevWind

goes from the soundboard of the guitar to you ear uncolored by any reflection.
In fact if you step back and think about it, using close reflection is more or less a different version of using a reverb or delay effect. Just sayin'.

I guess that's the whole point - it doesn't go to your ear - it goes outward away from you and the guitar. I find myself bending over the guitar terribly to "hear" it.

[KevWind]

Originally Posted by fitness1

I guess that's the whole point - it doesn't go to your ear - it goes outward away from you and the guitar. I find myself bending over the guitar terribly to "hear" it.

Actually the sound does go to your ear , sound waves travel in all directions. Now it may be that that the energy is more in a cone shape out from the sound hole

But if you are having to "bend over the guitar to hear it " , honestly that sounds more like a hearing issue, than an issue of the physics of sound propagation ?
Do you play finger style ?

[fitness1]

Originally Posted by KevWind

Actually the sound does go to your ear , sound waves travel in all directions. Now it may be that that the energy is more in a cone shape out from the sound hole

But if you are having to "bend over the guitar to hear it " , honestly that sounds more like a hearing issue, than an issue of the physics of sound propagation ?
Do you play finger style ?

EVERY guitar I've ever owned sounds completely different when I lean over in front of the guitar as much as I can. My hearing is very, very keen. You said it yourself - "cone shape from the soundhole" - it is simple physics - the sides and the back of an instrument are mostly inert compared to the top where the energy of the strings vibrate. I'm just trying to hear what it sounds like from the "other" side. Part of the evaluation .is trying to hear more clearly what a microphone would hear.

[KevWind]

Originally Posted by fitness1

EVERY guitar I've ever owned sounds completely different when I lean over in front of the guitar as much as I can. My hearing is very, very keen. You said it yourself - "cone shape from the soundhole" - it is simple physics - the sides and the back of an instrument are mostly inert compared to the top where the energy of the strings vibrate. I'm just trying to hear what it sounds like from the "other" side.

Well I think you are overlooking some important physics considerations

If you wish to discuss them we can But I am not trying to debate,,, so we can just leave it at,,,, you do what you think is best.

[fitness1]

Originally Posted by KevWind

Well I think you are overlooking some important physics considerations

If you wish to discuss them we can But I am not trying to debate,,, so we can just leave it at,,,, you do what you think is best.

Yes - best to let it die. I've been doing it wrong for 30 years or more now.

[dirkronk]

This thread is giving me deja vu. Or nostalgia. Or some amalgam of the two.

Growing up in a 2-bedroom/1-bath house, I could access the bathroom "concert hall" only if my parents were elsewhere. However...

I spent my freshman year in college (1968-9) at Baylor before transferring to UT Austin. In order not to get the stinkeye from my dorm roommate, I looked for other places to play my guitar. The bathroom was out...our old dorm only had communal bathroom/showers, not unlike a school gym locker room. But a few modern classroom buildings on the Baylor campus had outside stairs down to the basement level entrance/exit, with all brick or concrete surrounds. Nights and weekends, I'd go by myself or with my guitar-playing buddy Mike, stand or sit in these stairwells, and play. All sorts of reverb/amplification going on for our acoustics, and enough feedback for us to work on PP&M-style vocal harmonies (we needed the practice).


Dirk

[RussellHawaii]

Originally Posted by OPJ77

What is a parabolic reflector?

Parabolic refers to a shape like a satellite dish or radar antennae. This type of curve reflects sound ( or any waves) and concentrates them in one area.

[mcmars]

Huge metal corrugated culvert pipes are pretty famous for amplifying sound. Just west of Moab UT is a big (10ft diameter?) culvert that goes under a railroad track to access a popular hike and it is also a popular place to go play music.

Moab also has many natural sandstone rock alcoves and canyons that are destination musical locations. The Moab Music Festival seeks out many of these locations and has performances, like the Grotto along the Colorado River where they boat in and out a grand piano every year.

I got curious about metal culverts and googled culvert pipe acoustics and found out there is quite a bit of research of the physics of how culverts amplify and create tones, like whistling, and how these resonant sound can also become destructive in industrial applications. I guess all of us need our own 8ft diameter section of culvert in our back yard for a great practice place? https://www.researchgate.net/publica...Pipes_A_Review

[fitness1]

Originally Posted by RussellHawaii

Parabolic refers to a shape like a satellite dish or radar antennae. This type of curve reflects sound ( or any waves) and concentrates them in one area.

I remember back in the early 70's the Ontario Science Centre in Toronto had two large parabols facing each other maybe 60-70 feet apart. Someone could whisper in one, and the person at the other end could hear it clearly.

[Birdbrain]

Originally Posted by fitness1

It seems to me at one time someone was marketing a small plexiglas parabol on a stand.

I saw this recently too...

https://www.ebay.com/itm/203339725359

Just a tapered box on a post stand. Might not be an ideal design, but it might add something, and it's not ugly. I left uncertain about how large it is.

Utilizing some kind of passive acoustic reflector seems more natural and honest than electronic devices that actively add vibration to a guitar's back for greater volume (Transacoustic, anyone?). The best reflector would have to be stiff and solid, so it wouldn't shake and absorb sonic energy. The park shelter I mentioned earlier was solid and resonant, with a pyramid shape that broadcast the sound down from the lower heavens. I'd like to have that experience again, but at home.