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[Mario Castro]

How do you guys deal with the boomines of the sub?

[Nathan DePaulo]

How do you guys deal with the boomines of the sub?

One of two things.  I either cut 80Hz and boost 45Hz, or I give the sub to DJs who think it's the best thing since cupping the mic.

I have  a lot of good things to say about the LS800P: It's output to size is fantastic. It's so close to bullet proof it's not even funny.  It's easy to get ROI, because it's cost is not so great, and it's capability is significant.

The LS800P squarely fills a very specific set of critera.  I have however considered replacing it because I'd like a sub that be handled by one person easier (in and out of a van/suv) and takes up even less space.  For so many of my gigs I have to dial the LS800P down to match the tops or venues that a lower output sub doesn't sound like a bad thing, especially if it's flatter and/or plays lower.  But the LS800P just keeps earning it's keep, dry rental at a time, so it's hard to complain.

I have had a problem with the amp module rattling lately, however.  I recently went over the edges of the module with foil tape to try and reseal where it had separated, but it's still noticeable. Anyone else had this problem?

[Mario Castro]

One of two things.  I either cut 80Hz and boost 45Hz, or I give the sub to DJs who think it's the best thing since cupping the mic.

Thanks.

I have considered setting the shape control on the back to deep (+3db @ 50Hz) to try and balance the sub, I'll experiment cutting @ 80Hz.  How much do you usually boost/cut at those frequencies?

[Reggie Kendrick]

One of two things.  I either cut 80Hz and boost 45Hz, or I give the sub to DJs who think it's the best thing since cupping the mic.

I have  a lot of good things to say about the LS800P: It's output to size is fantastic. It's so close to bullet proof it's not even funny.  It's easy to get ROI, because it's cost is not so great, and it's capability is significant.

The LS800P squarely fills a very specific set of critera.  I have however considered replacing it because I'd like a sub that be handled by one person easier (in and out of a van/suv) and takes up even less space.  For so many of my gigs I have to dial the LS800P down to match the tops or venues that a lower output sub doesn't sound like a bad thing, especially if it's flatter and/or plays lower.  But the LS800P just keeps earning it's keep, dry rental at a time, so it's hard to complain.

I have had a problem with the amp module rattling lately, however.  I recently went over the edges of the module with foil tape to try and reseal where it had separated, but it's still noticeable. Anyone else had this problem?

Maybe one of those DJs you rented to caused it.  Try some rubber cement or JB Weld.

[Sheldon Harris]

Bob,

Same goes for things such as THE inverse square law.  There are actually a few inverse square laws and all are based upon theory that can not be recreated in the real world so, they are truly a general rule of thumb.
Lee

sir,
this is a technical forum: it is browsed and read by many people even more than those who post. to some, they take what they see posted here by the "pros", as audio gospel.


the inverse square LAW is not based on theory, that's why its a LAW, like the law of gravity, not like relativity theory

THEORIES are what is used to explain LAWS  theories can be and some eventually are disproved but LAWS always stand. that is why, its inverse square LAW and not inverse square theory. theories by themselves can not be laws. laws however are absolute and irrefutable based on what is observed or measured.

sheldon

[Lee Buckalew]

sir,
this is a technical forum: it is browsed and read by many people even more than those who post. to some, they take what they see posted here by the "pros", as audio gospel.


the inverse square LAW is not based on theory, that's why its a LAW, like the law of gravity, not like relativity theory

THEORIES are what is used to explain LAWS  theories can be and some eventually are disproved but LAWS always stand. that is why, its inverse square LAW and not inverse square theory. theories by themselves can not be laws. laws however are absolute and irrefutable based on what is observed or measured.

sheldon

Sheldon,
My point was that we must be careful in stating things such as "The Inverse Square Law..." when there are more than one and we also should not reference a law when we can not actually recreate the requirements to follow that law in the real world.

I stand by my comment that, there is not a single inverse square law and, in the real world the LAW can not be applied as it would be in the laboratory. 
There are inverse square laws pertaining to: gravitation, electrostatics, electromagnetic radiation, light and maybe others. 
There are a few that pertain to audio.
The two most common are those that relate to the sound pressure level of a spherical wave front and the sound pressure level of a cylindrical wavefront.
Since none of the loudspeaker requirements posited for either version of this law is actually available to us in the real world it is ridiculous to reference a halving of SPL per doubling of distance in a concert situation (or its converse).  In the real world this is more of a "general rule of thumb".
The law certainly is true but, my point was, you must conform to all stated parameters in order for the law to be properly applied and virtually none of the stated parameters can be conformed to in the real world.

If I am incorrect here please explain to me, within the context of sound reinforcement:
Where have you encountered an actual point source (by scientific definition) loudspeaker?
Where have you encountered a free field?

Where have you encountered a true cylindrical wavefront?


Lee

[Rob Spence]

If I am incorrect here please explain to me, within the context of sound reinforcement:
Where have you encountered an actual point source (by scientific definition) loudspeaker?
Where have you encountered a free field?

Where have you encountered a true cylindrical wavefront?
Lee

Lee, it turns out that the Inverse Square Law does NOT need those things to still be true.

For example, when you are a sufficient distance from a speaker system, it behaves as if a point source from a calculation perspective.

Your examples are not examples of the LAW as such but are examples of the use of the LAW.

What it seems to me that you are trying to get across is that while sound will diminish in volume by the Inverse Square Law, the perceived and/or measured sound in a specific venue may be affected by reflections from surfaces such as walls and ceilings or addition/cancellations from other sources (such as other speakers) and therefore, at certain measurement points not diminish precisely at the rate specified by the LAW.

However, when planning for SPL at a certain location, you do use the Inverse Square Law to figure out the required source SPL.

[Lee Buckalew]

Lee, it turns out that the Inverse Square Law does NOT need those things to still be true.

For example, when you are a sufficient distance from a speaker system, it behaves as if a point source from a calculation perspective.

Your examples are not examples of the LAW as such but are examples of the use of the LAW.

What it seems to me that you are trying to get across is that while sound will diminish in volume by the Inverse Square Law, the perceived and/or measured sound in a specific venue may be affected by reflections from surfaces such as walls and ceilings or addition/cancellations from other sources (such as other speakers) and therefore, at certain measurement points not diminish precisely at the rate specified by the LAW.

However, when planning for SPL at a certain location, you do use the Inverse Square Law to figure out the required source SPL.

This has strayed too far.
My point was, and is, that the various laws of physics applying to acoustic audio, while they are most certainly true, are only true when the rules governing them are held to.
Beyond that, in the real world, we can use them as guidelines but, our results will not always follow "The Law" the way that some would expect because many oversimplify it.  Our configurations contain many anomalies that are not accounted for in the definitions.  These can include boundaries, phase interaction, non-linear drivers, listening planes that are not at 90 degrees to our wavefront, etc.  All of these cause a deviation or deviations from the expected result.

And, per your last point, I do use one of the inverse square laws (whichever is appropriate) as a starting point (rule of thumb) to determine required SPL but, I then use much more accurate measurements taken from the real world.  When using the inverse square law calculations I would not say that I could determine a precise loss but rather that the loss would be approximately xx dB/SPL average.


Lee

[Brad Weber]

Buddy,

We're doubling the drivers, and we're doubling the power delivered. Double the drivers is 3dB. Double the power is 3dB. Together, 6dB. How you would double the drivers without doubling the power using any modern amp run below maximum load is beyond me, anyway.

I fucking guarantee it.™

Adding a second equal level source, which inherently implies doubling the power, with a random relative phase relationship equates to a 3dB gain.  Adding a second equal level, coherent source that is is in phase with the original source at the measurement point is up to a 6dB gain, however having two sources does not implicitly equate to their being in phase.

Inverse square law applies to a point source in a free field condition and good luck on finding a real world application that actually meets that criteria, if it did apply then we would not have to worry about things like near to far field transitions, Critical Distance, etc.  However, assuming inverse square law is a simpler and more conservative (ignoring air absorption) approach so it is often used for the purpose of estimating maximum distance losses.

The acoustic centers of each transducer need to be within 1/4 wavelength in order to couple additively.  At sub frequencies, that means anywhere from 2'-6'.  It is not necessary for the transducers to occupy the same virtual space.

If you mean exhibit more than the 3dB gain associated with two sources with random relative phase, then that is where the 1/4 wavelength factors in.  Two coherent sources having 1/4 wavelength or 90 degrees of relative phase is a 3dB gain and if the relative phase is less than that, which is guaranteed by the sources being withn 1/4 wavelength of one another, then you can get more than a 3dB increase in amplitude.  Unfortunately, many people seem to believe that two sources being within 1/4 wavelength of one another equates to a 6dB gain when the 1/4 wavelength dimension actually equates to a 3dB gain and it takes two coherent sources with 0 relative phase difference, or two sources occupying the same location, to get the full 6dB gain.

[Sheldon Harris]

Adding a second equal level source, which inherently implies doubling the power, with a random relative phase relationship equates to a 3dB gain.  Adding a second equal level, coherent source that is is in phase with the original source at the measurement point is up to a 6dB gain, however having two sources does not implicitly equate to their being in phase.

from going through the posts i think its understood, if not implicitly stated that sources are equally powered and in phase.

sheldon

[ProSoundWeb Community]