Can we stop saying "box rise"? Explanation/rant

[Buck 5,000+ posts]

That's just going to be too complicated for most, I'm fairly certain.

 

[jt4x4]

I was reluctant to start this thread because I am confident in my relative knowledge of electricity but not acoustics. I expected to be flamed by those more familiar with acoustics and pressure. Total impedance HAS to (in my mind) include electrical resistance as well as physical resistance. When I hear people say "box rise", I equate it to a pump or a fan driven by an electric motor, because that is what I focus on in my profession. A fan motor or a pump motor uses a given amount of electricity without a load, but uses more electricity based on how much water or air is incoming verses how much is outgoing. Similarly, if a space is already pressurized, it's going to take more power to further-pressurize it, which is what a speaker does when it extends into that space. I'd also expect speakers to bottom-out easier in spaces with higher air pressure. So given that theory, SPL's should be relative to elevation, since air is thinner when you get further from Earth.

I'm speculating here, and I'm probably wrong, but I like what Buck started with thinking out loud. It's fun to learn!

 

[hispls 5,000+ posts]

simply calculate how certain factors cause rise

There's probably some direct relationships to be found, but really for our purposes we're not trying to dial in an impedance with box build/tweak, rather just building a good efficient box then using the measured impedance at our one burp frequency to plan amp and coil configuration to maximize power output from the amp. This should be the absolute last thing done as any changes to the port or box or even opening windows or whatever will effect the impedance curve of the system
I do not believe air pressure within normal conditions or humidity will change anything dramatically and acoustic coupling between a loudspeaker and the air is very poor in general (hence why impedance matching via compression horn gains so much efficiency) so it should be negligible in these circuit designs.
Dunno if anybody around here is better at number crunching with electrical circuits to throw some numbers at those and see what can happen with changes. It's been longer than I care to think about since I did any of this stuff in school.

SPL's should be relative to elevation, since air is thinner when you get further from Earth.

Most people gain a little bit closer to sea level and in cold weather but EMF recently did video of testing at various elevations that proved inconclusive. Again, acoustic coupling of a loudspeaker to the air is poor so differences based on atmospheric conditions are generally very small. Also it is vehicle specific. I know a guy who always gains on really hot days.

 

[Buck 5,000+ posts]

I was reluctant to start this thread because I am confident in my relative knowledge of electricity but not acoustics. I expected to be flamed by those more familiar with acoustics and pressure. Total impedance HAS to (in my mind) include electrical resistance as well as physical resistance. When I hear people say "box rise", I equate it to a pump or a fan driven by an electric motor, because that is what I focus on in my profession. A fan motor or a pump motor uses a given amount of electricity without a load, but uses more electricity based on how much water or air is incoming verses how much is outgoing. Similarly, if a space is already pressurized, it's going to take more power to further-pressurize it, which is what a speaker does when it extends into that space. I'd also expect speakers to bottom-out easier in spaces with higher air pressure. So given that theory, SPL's should be relative to elevation, since air is thinner when you get further from Earth.

I'm speculating here, and I'm probably wrong, but I like what Buck started with thinking out loud. It's fun to learn!

Yeah I would agree with the electrical and air/mechanical total for sure.

 

[Buck 5,000+ posts]

I know a guy who always gains on really hot days.

That may be because of a tuning change because of air density.

 

[hispls 5,000+ posts]

That may be because of a tuning change because of air density.

The guy in question is a 20 year veteran in the lanes and he and his teammates have some big world finals builds under their belts. Honestly I don't think any of them really have any good explanations on why some of the stuff they do works, they just do a shitload of builds and testing and have a good feel for how to get results.

 

[Buck 5,000+ posts]

The guy in question is a 20 year veteran in the lanes and he and his teammates have some big world finals builds under their belts. Honestly I don't think any of them really have any good explanations on why some of the stuff they do works, they just do a shitload of builds and testing and have a good feel for how to get results.

Yeah, that's what I was saying about nature, it's alive. We can't account for everything that affects a system.

 

[hispls 5,000+ posts]

Yeah, that's what I was saying about nature, it's alive. We can't account for everything that affects a system.

That and I mean like everything else, box size/shape/etc. I've heard some utterly nonsensical explanations on why they do certain things but at the end of the day the meter doesn't lie so whether the logic behind it is nothing but quackery they've figured out what works.

 

[Buck 5,000+ posts]

That and I mean like everything else, box size/shape/etc. I've heard some utterly nonsensical explanations on why they do certain things but at the end of the day the meter doesn't lie so whether the logic behind it is nothing but quackery they've figured out what works.

The meter is the true true

 

[JustBri]

Damn! For not being an expert you gave the most detailed & easy to follow explanation I think I've ever heard. Awesome job man