Bass Frequency Myth!

[Step]

Sorry, but you are wrong. In fact, if you get further away, say go into the restroom in a club, you will generally hear the bass louder than anything else. Everything I posted came directly from the websites of speaker manufacturers. Maybe you should visit their websites. I never said I agreed with their theory. I simply posted what they are claiming.

uhmm, well show me the speaker manufacturer's websites so I know who not to buy from

 

[greenboy]

Amazing one will support their misconceptions with links that don't actually further their point.

Also amazing so many bass players continue to be clueless about the issues and gotchas for lower frequency sound reinforcement and reproduction.

Anyway, LF does not need time to "focus", "develop" or any of that other tripe, and ROOM EFFECTS withstanding, follows the same inverse square laws as any other frequencies. But the room effects (destructive cancellations due to room-mixed/reflected waves partially or fully out of phase at various freqs and locations) confuse people at times to what is actually going on until they become aware of the phenomenom.

A further fly in the ointment to correctly understanding what is going on with sound is that so many players have their speakers aimed at their knees which I'm sure for the majority of them do not incorporate auxillary ears.

Your teacher is actually somewhat correct. Sound travels in wavelengths. The wavelength is the horizontal distance between any two successive equivalent points on the wave. That means that the wavelength is the horizontal length of one cycle of the wave. The period of a wave is the time required for one complete cycle of the wave to pass by a point. So, the period is the amount of time it takes for a wave to travel a distance of one wavelength.
The lower the frequency, the longer the wavelength so it actually takes longer for the sound to complete each cycle. You will actually hear the bass better if you back away from the source rather than being close to it. Having said that, speaker cabinet manufacturers have tried to reduce this effect by created speakers which move more rapidly and more frequently.

Here are a couple of links.

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http://home.cc.umanitoba.ca/~krussll/138/sec4/acoust1.htm

 

[Rob22315]

Amazing one will support their misconceptions with links that don't actually further their point.

Also amazing so many bass players continue to be clueless about the issues and gotchas for lower frequency sound reinforcement and reproduction.

Anyway, LF does not need time to "focus", "develop" or any of that other tripe, and ROOM EFFECTS withstanding, follows the same inverse square laws as any other frequencies.

Amazing that someone here thinks using the word 'amazing' is more convincing than links.

Anyway, even speakers designed with as few as 2 elements still behave as phased arrays and the mathematics still applies. The near-field distance (distance to form the intended wavefront) is 1-2 wavelengths from the source so if you're using cabs with 2 or more elements, they should be back from the edge of the audience by 2 wavelengths of the longest frequency. Here are three links that talk about 1. acoustic beamforming and 2. directional speakers designed using these principles and 3. see the picture at the top of page 13 of this link to get a good visual on what's happening. Note the third attachment applies to radars but the math behind the theory is the same.

http://en.wikipedia.org/wiki/Beamforming
http://en.wikipedia.org/wiki/Directional_Sound
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These principles and features are well known to the sonar and radar communities. The more sophisticated speaker companies have good engineers well versed in these principles as well.

 

[greenboy]

Got any idea what it takes to make low frequencies directional? I thought not. It's highly impractical until you get into real large venues and even then it's not anything like what can be done with midrange-and-up line/curevelinear arrays.

EDIT: It's certainly not in the province of 2 or 4 subs in clubs type setups, nor in bass players' rigs.

I've seen people make arguments for audio cabling that don't take place within the audio bandwidth ANYWAY, and I'm wondering whether we should be dragging sonar and radar perhaps the likes of Arecibo into this ; }

 

[Ric5]

Well now let's actually add a little science. When talking of low frequency wavelengths, we are talking about the distance of one complete cycle of the wavelength. (eg. a complete cycle of a 41hz wave is 27 ft long) Does that mean you can't hear it up close, of course not. But this measurement is important when it comes to live sound. Take a player playing an open E string at 41hz. 27ft away the wave completes a full cycle. Fractions of a second later, the same 41hz cycle from the stage amp arrives. Depending on how far the backline is from the PA, this can make a HUGE difference in whether the bass is in your face or weak and average. If the bass amp is say 13.5 ft from the FOH stack (1/2 0f a full wave cycle) it will be perfectly out of phase with the sound from the PA. Will you hear the low end? Again of course, but it will be severely compromised. The exact same issue can occur when using a mic and a DI for bass. The DI signal arrives quicker than the mic, and again can result in out of phase, and weak bass. Often switching the phase of one of the inputs corrects the problem, but sometimes the signal isn't exactly out of phase. Using delay on one of the inputs or in the case of FOH can bring the bass into perfect phase and realize the best bass sound possible. Remember, that is some of the science of bass wavelength. Many other factors can influence what can be heard both near and far.http://www.mcsquared.com/wavelength.htm

Excellent post!

 

[greenboy]

As per Jerry's post,

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and the formula

wavelength' = 1130 / frequency

 

[Ric5]

Now, with that being said, you might think that you'd have to stand 8.1 meters (or roughly 25 feet) from a bass cab to hear an open E - except we know that's not true.

Here's why -

That wave is audible along the entirety of it's wave, AND it's going from peak to peak 41 times a second. Whether you're standing 1 foot or 15 meters away, you're going to hear one solid note as this wave passes around and through you. The simple fact, as noted above, is that the bass is perceived (and is comparatively) louder because it doesn't attenuate as easily and quickly as the higher frequencies.

Yes exactly ... the wave is audible along the entire length of its wave

 

[greenboy]

http://www.google.com/search?client=opera&rls=en&q=subwoofer+arrays&sourceid=opera&ie=utf-8&oe=utf-8

I think this one was all right but it's been awhile: Invalid Link Removed

But definitely ProSoundWeb is a place to go as are JBL technical papers. Also Meyer has had some good stuff on aiming LF.

 

[Rob22315]

Got any idea what it takes to make low frequencies directional?

Yes, we do this on sonar systems all the time (gives you a hint as to one of the things I've worked on). Apparently the speaker community does as well.

As I stated already, it takes 1-2 lambda for the wave front to form so if you want the best sound out of your multi-speaker cab, move it back. Obviously you're not doing any beam steering here since essentially the same signal is going to each of the speaker elements at the same time. That simply means you expect the 'beam' to project straight out of the front. The physics and the associated math still apply whether or not you want it to or intended it to.

The math doesn't apply to single speaker cabs but anything with 2 or more speakers could benefit from this if you find you're having issues you can't solve on the sound board. Since it costs you nothing to move the cab (if you have the room), this is the first thing I'd try before going to acoustic dampening tiles or a new amp head or a new sound guy. This is only one of a lot of complex factors that come in to play here so don't expect this to be a cure-all.

You need to take a course in advanced acoustics and run through the math once or twice to get a good sense for what's going on.

 

[BroKenSticKs]

the closer you place a mic to the sound source the more low end is picked up. Its called proximity effect. So what does that say...

 

[JimmyM]

As I stated already, it takes 1-2 lambda for the wave front to form so if you want the best sound out of your multi-speaker cab, move it back.

you know, you sound really intelligent and knowledgeable, but this part trips me up. sound waves do not have to form fully to be heard, and they can be heard at any part of the waveform, not just 30 feet back. or are you referring to something completely different?

 

[Big B.]

the closer you place a mic to the sound source the more low end is picked up. Its called proximity effect. So what does that say...

I am no audio expert but isn't that limited to dynamic microphones? I am under the impression that that is not an issue with condensers or other powered mics.

 

[greenboy]

I am no audio expert but isn't that limited to dynamic microphones? I am under the impression that that is not an issue with condensers or other powered mics.

Nothing to do with powered mics. It has to do with microphone patterns themselves, and really isn't much different than the principles of boundary loading for speakers. Proximity effect as experienced with non-omnidirectional pattens such as cardioid is not any way to prove anything substantial about bass response versus distance.

http://en.wikipedia.org/wiki/Microphone#Microphone_polar_patterns

Just to further muddy the waters with stuff that has little to do with the circumstances most working bassists find themselves in:

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[Rob22315]

you know, you sound really intelligent and knowledgeable, but this part trips me up. sound waves do not have to form fully to be heard, and they can be heard at any part of the waveform, not just 30 feet back. or are you referring to something completely different?

You're right, we can sense the pressure changes where ever the occur. If this near-field effect is an issue for your setup, you'll still hear sound in that range but it won't sound right. The combination of output from all the smaller speakers takes a measureable distance to add up or cancel to eventually form the sound (wave front) you want to create. Another way to think about this is that the speaker size needs to be proportional to the frequency - small tweeters for short wavelength, big speakers for long wavelength. At some point it become prohibitive to make a really big speaker cone and magnet. Fortunately, we've developed techniques to create a virtual 'really big speaker' out of a bunch of small ones but, like all sophisticated engineering approaches, it comes with some warts. I don't want to give anyone a sense that I think this is beyond your understanding because it isn't. Its just that not all of us want to spend our time on this stuff.

If that doesn't make sense, the main 'take-away' is that if you aren't happy with the sound from your multi-speaker cab, one of the things you can try is to increase the distance to the listener to allow time for the sound from each of the smaller speakers to sort themselves out. There's no guarantee it'll fix your issue but there's enough science behind it to at least give it a try and it probably won't cost you anything other than a little sweat. If you don't hear an improvement, move them back and fire the sound guy.

If the wavelength for the low B is 27 ft, you might not have enough rooom to get the really low notes better but there might be enough room to get the higher notes to sound better.

 

[mambo4]

That wave is audible along the entirety of it's wave, AND it's going from peak to peak 41 times a second. Whether you're standing 1 foot or 15 meters away, you're going to hear one solid note as this wave passes around and through you. The simple fact, as noted above, is that the bass is perceived (and is comparatively) louder because it doesn't attenuate as easily and quickly as the higher frequencies.

nailed it.

 

[Coolhandjjl]

Sorry, but you are wrong. In fact, if you get further away, say go into the restroom in a club, you will generally hear the bass louder than anything else. Everything I posted came directly from the websites of speaker manufacturers. Maybe you should visit their websites. I never said I agreed with their theory. I simply posted what they are claiming.

Mainly because when you are in the main performance hall itself, you are encountering lots of boundary cancellation at various places in that room, resulting in a perceived loss of some bass tones. Further away, it all evens out.

The lower the frequency, the longer the wavelength so it actually takes longer for the sound to complete each cycle. You will actually hear the bass better if you back away from the source rather than being close to it.

That's voodoo science.

Having said that, speaker cabinet manufacturers have tried to reduce this effect by created speakers which move more rapidly and more frequently........Everything I posted came directly from the websites of speaker manufacturers. Maybe you should visit their websites. I never said I agreed with their theory. I simply posted what they are claiming.

It's called marketing/advertising. Advertisers are actually allowed to make stuff up. It's called puffery.

 

[Rob22315]

Just to further muddy the waters with stuff that has little to do with the circumstances most working bassists find themselves in:

You're really good with what we call FUD at work - Fear, Uncertainty and Doubt, but light on technical details to back it up. You might try some of these arguments -

1. phased array elements are generally spaced at 1/2 the wavelength of operation so these near-field effects would likely be limited to acoustic wavelengths with harmonics based on the separation of the speakers of the cab. At least, beam forming arrays are designed this way even though we're not trying to steer the beam here.

2. The speaker cones on a normal cab are large compared to the spacing of the speakers and can't be modeled as point sources (which is part of making the math work). (Line array designers seem to be good at exploiting these effects so I don't know if I buy this.)

3. A common speaker design principle when using multiple sources is to place the sources at less than 2/3 of highest frequency apart to avoid band-pass effects (unintentional destructive interference). Cab speakers are intentionally designed this way (are they? I don't know, I'm not a cab designer.) to avoid the effects that phased array designers exploit.

I'm sure the folks on DIY audio could give you more hands-on insights with some of this. There's a group doing cool stuff with line arrays over there. [I did a quick search there, interestingly enough, they suggested coming here to TalkBass. Hmmm]

 

[JimmyM]

I'm not a cab designer.

oof, what a giveaway!



well greenboy is a cab designer, so what he says goes as far as i'm concerned, bro. i'm strictly a musical genius so i leave the cab geniusing to guys like greenie and a handful of other known cab geniuses on here.

 

[greenboy]

So much of what you've said is every bit as unsubstantiated, filled with buzzwords but showing little cognizance of the actual thread's premise. And this ain't long-range submarine detection, and not even high-end touring where the toys are better. I pulled up a bunch of links you can read if you want to understand what's in practical use at the higher end of SR however. But I'm certainly not going to waste tons of time arguing point by point since you don't seem to actually understand how to actually address what was posed at the start of the thread.

Check that link at the Seattle zoo in the google to see how poorly some of the suppositions not yet practically advanced end up playing out.

Again, you seem to be like the guys who talk about skin effect and a lot of other nonsense that isn't especialy pertinent at audio frequencies when discussing cables and wiring, not even coming from the audio sector.

 

[greenboy]

Seatltle zoo linkie: Invalid Link Removed