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Author Topic: Importance of basic understanding & fundamentals  (Read 3891 times)

Luke Geis

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Re: Importance of basic understanding & fundamentals
« Reply #10 on: March 24, 2017, 08:06:19 pm »

I was more interested in the rather wacky trussing used to support the mains! While I am sure it works, I wouldn't entirely trust it.....

The subs setup was definitely a lol moment.
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Ivan Beaver

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Re: Importance of basic understanding & fundamentals
« Reply #11 on: March 25, 2017, 06:56:15 am »

Lets assume someone out of your control decided the subs should be against the wall. Would you place them alle facing forward or alle facing backwards?
It depends on how high the subs are being used.

But "assuming" the input jacks would not be a problem (but they probably would be in most cases), the would be better (sonically) to face them towards the wall-but keep them maybe a foot away from it.

My big concern in most shows would be that either or both the cables/jacks would get stepped on or the subs would get shoved up against the wall.

By facing them into the wall, you have eliminated the reflection that would be coming off of the wall.

But since those subs are not very deep, this reflection would be higher in freq and may not cause an issue.

SO, once again, the freq of usage determines if it is a problem or not.

Without knowing the highest freq,, it is only guess work

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Ivan Beaver
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John Roberts {JR}

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Re: Importance of basic understanding & fundamentals
« Reply #12 on: March 25, 2017, 04:27:43 pm »

Relative to the original signal (from the loudspeaker) the reflected signal would be lagging-due to the later arrival, by whatever the difference of arrival times is.
The reflected signal is inverted polarity "and" time delayed.

Phase shift is a little messy for anything other than fixed sine waves.

Perhaps why I am not a speaker guy...  8) 

JR

PS: The polarity police are not happy.

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Chris Grimshaw

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Re: Importance of basic understanding & fundamentals
« Reply #13 on: March 26, 2017, 06:03:21 am »

It depends on how high the subs are being used.

But "assuming" the input jacks would not be a problem (but they probably would be in most cases), the would be better (sonically) to face them towards the wall-but keep them maybe a foot away from it.


Huh, interesting.
I'm not sure I understand why it'd be sonically better to fire them at a 1' wide slot.

Sure, you might (might) get a little bit of bandpass effect that'll cut down a little on harmonics produced when you push the system, but chances are there'll also be an out-of-band peak. If it's far from the crossover, probaby not too much of an issue. If it's close to the crossover, the associated phase shift as you go over the peak might make integration with the tops more interesting.
The peak would also impose itself on the distortion profile, since it's an acoustic effect.

In short, I can see it sounding different. I'm not so sure it'll sound any better.

Chris
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Ivan Beaver

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Re: Importance of basic understanding & fundamentals
« Reply #14 on: March 26, 2017, 07:46:45 am »

Huh, interesting.
I'm not sure I understand why it'd be sonically better to fire them at a 1' wide slot.

Sure, you might (might) get a little bit of bandpass effect that'll cut down a little on harmonics produced when you push the system, but chances are there'll also be an out-of-band peak. If it's far from the crossover, probaby not too much of an issue. If it's close to the crossover, the associated phase shift as you go over the peak might make integration with the tops more interesting.
The peak would also impose itself on the distortion profile, since it's an acoustic effect.

In short, I can see it sounding different. I'm not so sure it'll sound any better.

Chris
Most subs are essentially "omni" at their lower freq.  Some more than others

When they are placed a couple of feet from a boundary, there will be reflected energy off of the boundary that will then "mix in" with the front radiation and cause combfiltering cancellations-due to the different time arrivals.

With the main energy going to the boundary, this "source" of energy will be at a single time-so the cancellations would be limited to the much lower energy radiating off of the rear of the cabinet.
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Ivan Beaver
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Ivan Beaver

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Re: Importance of basic understanding & fundamentals
« Reply #15 on: March 26, 2017, 07:49:49 am »

The reflected signal is inverted polarity "and" time delayed.

Phase shift is a little messy for anything other than fixed sine waves.

Perhaps why I am not a speaker guy...  8) 

JR

PS: The polarity police are not happy.
OK I guess I will have to take a warning ticket on that one.

The phase (due to the time of the signal path) would be "added to" the polarity shift of 180* of the reflection.

Yes, both are happening-so it is not just the simple distance that is affecting the overall phase of the reflected signal with respect to the original signal
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Ivan Beaver
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Tim Gurske

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Re: Importance of basic understanding & fundamentals
« Reply #16 on: April 19, 2017, 11:38:40 pm »

Hopefully in my lifetime we will get a good way to visualize sound waves, something better than Schlieren flow visualization or computer models. Like a FLIR camera for sound waves. Imagine being able to actually see what the sound is doing inside the venue. I know it would help me understand what is happening.
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Ivan Beaver

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Re: Importance of basic understanding & fundamentals
« Reply #17 on: April 20, 2017, 07:08:17 am »

Hopefully in my lifetime we will get a good way to visualize sound waves, something better than Schlieren flow visualization or computer models. Like a FLIR camera for sound waves. Imagine being able to actually see what the sound is doing inside the venue. I know it would help me understand what is happening.
Seeing it is one thing.

Knowing what you can and cannot do about it is quite another.

The more basic understanding you have, the better the chances of being able to resolve the issue.

But with many room, there is little you can do regarding the lower freq.

Due to the physical size of the room or where you can actually put speakers.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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PHYSICS- NOT FADS!

Tim McCulloch

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Re: Importance of basic understanding & fundamentals
« Reply #18 on: April 20, 2017, 10:22:43 am »

Hopefully in my lifetime we will get a good way to visualize sound waves, something better than Schlieren flow visualization or computer models. Like a FLIR camera for sound waves. Imagine being able to actually see what the sound is doing inside the venue. I know it would help me understand what is happening.

The problem in teaching or explaining sound is that it's invisible, but no amount of visualization is likely to create an "ah ha!" moment that can't be done already.
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John Roberts {JR}

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Re: Importance of basic understanding & fundamentals
« Reply #19 on: April 20, 2017, 10:38:59 am »

The problem in teaching or explaining sound is that it's invisible, but no amount of visualization is likely to create an "ah ha!" moment that can't be done already.
A classic visualization medium is the old pebble dropped into a mud puddle. While only in 2 dimensions.

JR 
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