About "bass frequencies need space to develope" myth

[grendle]

I'm unclear on this.

Sound does need time to develop right? ie, A fundamental tone of 41HZ needs 1/41th of a second to complete its cycle, while a fundamental tone of 440Hz only needs 1/440th of a second to do the same.

Since sound travels as time passes, its normal for people to bundle together 'time passed' and 'distance travelled'.

Its pretty much a terminology. Pissing contest

 

[walterw]

the "developing" myth is that you need the space that a soundwave takes up to hear it, so a low bass frequency would need several yards to "form".

the fact is that at any given point, the air molecules will move back and forth at whatever frequency they're getting hit with; with IEMs, they'll do that just fine inside your ear canal.

 

[Bob Lee (QSC)]

Yep. The composite signal will develop or form in open air away from the antenna. Usually 10-20 feet out

The distance depends on the signal wavelength and the size of the array. The far field on directional AM broadcast antenna systems might not really take shape for a mile or two. OTOH, a two-element array for millimeter waves could have a pretty well-defined directional pattern in less than an inch.

 

[nutdog]

This is a sound wave on drugs.

 

[Bob Lee (QSC)]

I'm unclear on this.

Sound does need time to develop right? ie, A fundamental tone of 41HZ needs 1/41th of a second to complete its cycle, while a fundamental tone of 440Hz only needs 1/440th of a second to do the same.

Since sound travels as time passes, its normal for people to bundle together 'time passed' and 'distance travelled'.

Frequency doesn't require full cycles.

 

[Schizo Sapiens]

I'm unclear on this.

Sound does need time to develop right? ie, A fundamental tone of 41HZ needs 1/41th of a second to complete its cycle, while a fundamental tone of 440Hz only needs 1/440th of a second to do the same.

Since sound travels as time passes, its normal for people to bundle together 'time passed' and 'distance travelled'.

Yes, sound needs time to develop, but people saying "development" thing don't mean "you won't hear low E fundamental until 1/41th of second pass". They usually mean that the lows aren't fully heard unless you're 10-20 feet away from the amp as if sound wave is rope wave. And they don't mean only first 1/41th of second.

 

[Stick_Player]

Yes, sound needs time to develop, but people saying "development" thing don't mean "you won't hear low E fundamental until 1/41th of second pass". They usually mean that the lows aren't fully heard unless you're 10-20 feet away from the amp as if sound wave is rope wave. And they don't mean only first 1/41th of second.

My headphones are firmly on my head, not 20 feet away, and I can clearly hear 41 cycles, even lower.

 

[DukeLeJeune]

One reason why there can be a change in spectral balance over distance is the directional properties of the mid and high frequency sections. Usually they are a lot more directional than the low frequency section. So up close where the direct sound dominates, the mids and highs may be louder relative to the lows. Farther back where the reverberant energy dominates, the mids and highs don't get boosted as much by the reverberant contribution as the lows do, so now the lows are louder.

If the spectral balance is correct back in the reverberant field, but "lean" up in the near field, then one might come to the conclusion that the lows need space to develop. But that wouldn't be accurate.

 

[grendle]

The distance depends on the signal wavelength and the size of the array. The far field on directional AM broadcast antenna systems might not really take shape for a mile or two. OTOH, a two-element array for millimeter waves could have a pretty well-defined directional pattern in less than an inch.

Yeah I did a lot of work with navigational equipment. The VOR stuff takes about 10' off the radials. It's basically AM,FM, and phase mod all on the carrier at the same time but transmitted seperatly. Makes really cool noises before it locks up lol

 

[Bassamatic]

My headphones are firmly on my head, not 20 feet away, and I can clearly hear 41 cycles, even lower.

Headphones are not the same as speakers. There is very little or no "room acoustics". Headphones are essentially working into a non resonant 2-dimensional space and not into the world at large as speakers do.

(I know it is not 2D, but headphone acoustics are very different from speaker acoustics).

 

[Bob Lee (QSC)]

Headphones are not the same as speakers. There is very little or no "room acoustics". Headphones are essentially working into a non resonant 2-dimensional space and not into the world at large as speakers do.

(I know it is not 2D, but headphone acoustics are very different from speaker acoustics).

Even so, headphones prove that sound waves at bass frequencies don't need space to "develop."

 

[Turock]

But for all intensive purposes 30 Hz dosent change after its generated by the speaker.

Does the same hold true for laid back purposes?

 

[walterw]

One reason why there can be a change in spectral balance over distance is the directional properties of the mid and high frequency sections. Usually they are a lot more directional than the low frequency section. So up close where the direct sound dominates, the mids and highs may be louder relative to the lows. Farther back where the reverberant energy dominates, the mids and highs don't get boosted as much by the reverberant contribution as the lows do, so now the lows are louder.

there it is.

up close, you get the mids and highs directly (as long as they're aimed at you). further back, you might get less of that, while the lows start resonating in the room.

the bass isn't "developing" back there, it's just "surviving", and maybe also "resonating".

 

[ggunn]

there it is.

up close, you get the mids and highs directly (as long as they're aimed at you). further back, you might get less of that, while the lows start resonating in the room.

the bass isn't "developing" back there, it's just "surviving", and maybe also "resonating".

I have heard the reverse of that at outdoor shows. Up close the bass is very thick, but the farther back you go, the less you hear. The bass emanates more or less hemispherically from the subs while the mids and highs are more directional, putting energy into a smaller slice of space, so the SPL doesn't fall away as quickly as you move back. This is especially true of linear arrays with subs.

In rooms it is common for the low end to sound louder near the walls, floor, and (especially) corners. I assume that is because the closer you get to a reflecting surface, the closer in phase are the incident and reflected waves. In my rehearsal space, the keyboard player was set up in a corner and was always complaining about the bass volume. The rest of us were puzzled, because it sounded balanced to us. We moved him out of the corner and he was fine after that.

 

[Bob Lee (QSC)]

The bass emanates more or less hemispherically from the subs while the mids and highs are more directional, putting energy into a smaller slice of space, so the SPL doesn't fall away as quickly as you move back.

With spherical wavefronts, even partially spherical, the SPL actually does fall away as quickly as you move back--6 dB per doubling of distance. This is the well-known Inverse Square Law.

This is especially true of linear arrays with subs.

Line arrays emit a wavefront that approaches a cylindrical form. A truly cylindrical wavefront drops 3 dB per doubling of distance.