Bass- at what frequency does it change from sounding like a string to just a low tone?

Strings produce a bunch of different frequencies that make them sound like a string. The technique used to vibrate the string changes the frequency profile, if you will, of the sound. A hard pick produces different frequencies than fingers, etc.

One good example song is "Snuggle Up" by Brian Bromberg. If your low end is clean and clear enough, there’s a lot of very low frequency pitches mixed with textures on top from fingerstyle playing with muted plucks. A pure synthetically produced sine wave at the same fundamental frequencies would just sound like pure tones, without the overlaid textures.

I agree with gladmo but will try to answer directly. 60hz grabs the kick drum impact and is as high as you need to go with good speakers imo. At 80hz you are clearly into the bsss guitar range and it can get hard to match tone even with a highpass it sounds like a sub/sat combo to me. At 60hz you get bass slam but could lose a touch of texture at 40-50hz if you have VERY capable speakers  

But if you listen to just the subs with no speakers right around 35hz it is just tones or at least very slow cycles and it is just tones more or less. At 35 you are below an electric bass guitar. 35hz is what shakes the room for home theater. 
 

I have had subs in 3 systems while electronics and speakers changed a few times the subs always stayed. rough speaker specs and casual measurements in my room confirmed the specs more or less (large room with minimal nodes). It is different for each system room.  

thiel 2.4=flat to 32hz, used a 60hz highpass, thiels have great low bass but it is tuned too light for my tastes.   

revel 228be=flat to 45hz? used a 60hz highpass, Revel has no low bass, totally mixing in action… in bad need of subs  

JBl 4367=flat to 40hz, use a 40hz highpass. Amazing bass texture from these JBLs and they outperform the subs from 40hz up with more texture and tone but they drop lock a rock at 40hz.  
 

Thanks, y’all.

All this information is quite helpful. My subs are SVBs, So I’m using a low pass filter set at 58 for Atc Speaker’s that go down to 48, measured at six not three drop off.

I guess what I’m really after is when subs are operating properly, or even with just floor standers, how low am I supposed to be able to hear notes as they would sound with actual Instruments in the room?

I am worried that my system doesn’t sound as good as it could, and that maybe other people hear much more than tones at frequencies lower than mine.

Beats me.

What are your main speakers? btw, always good to post your system in your profile, saves asking additional questions:)

There's not a lot going on below 40hz,except maybe electronically enhanced tones or pipe organ tones.What there is normally are low tones and resonances. If your floors and walls are "singing" along than those tones won't sound as clear as you'd like. This is a link to some frequency charts that illustrate where the instruments and vocals reside that might interest you.https://www.bing.com/images/search?view=detailV2&ccid=fjNn8kLi&id=981426F355CF8B0314AEA0066F324A52613C25B5&thid=OIP.fjNn8kLitMiphe7sH3ZolgHaIR&mediaurl=https%3A%2F%2Fexternal-preview.redd.it%2FG-ZpqOjDR1r1xMXzByqv2OX0cRK5KXIpz3VGMfXYpkw.jpg%3Fauto%3Dwebp%26s%3Dfe5718bae0049cc23247e7345c320538c4fe93fe&cdnurl=https%3A%2F%2Fth.bing.com%2Fth%2Fid%2FR.7e3367f242e2b4c8a985eeec1f766896%3Frik%3DtSU8YVJKMm8GoA%26pid%3DImgRaw%26r%3D0&exph=2151&expw=1924&q=frequency+chart+for+instruments&simid=608000213540172012&form=IRPRST&ck=98CFCCC39A2D2047CC2604D79D0D6323&selectedindex=7&ajaxhist=0&ajaxserp=0&vt=4&sim=11