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

[hispls 5,000+ posts]

Rise is only important if you need a one note SPL box, in theory to get the most power through the coils as possible. Even then, I have doubts as to how important it is.

In the past it has definitely been worth knowing what impedance is at your burp frequency to plan coils and amps accordingly, these days possibly less important for most folks considering how cheap we can buy full bridge power. My first 150+ was running my old JBL/Crown A6000 into """1.4 ohm""" while in 4 ohm mode. I had determined that impedance at my peak was actually about 6 ohms with that sub/box/vehicle and that it was safe. For reference, I gained nearly 5dB over daily configuration running that same sub/box at 6 ohm nominal.

Also want to point out that IF you know sub and box specs you should be able to predict impedance at any given frequency since every variable can be converted into ohms, henrys or farrads, but for practical purposes, using a constant voltage source and measuring current and doing the math is probably best. Or to shortcut that, Dayton DATS will give you an impedance graph in a couple seconds.

Some googling can break down which variables are what.

Also output from Dayton DATS. This is the wall in my Jeep wired to .7 ohm nominal

 

[Buck 5,000+ posts]

In the past it has definitely been worth knowing what impedance is at your burp frequency to plan coils and amps accordingly, these days possibly less important for most folks considering how cheap we can buy full bridge power. My first 150+ was running my old JBL/Crown A6000 into """1.4 ohm""" while in 4 ohm mode. I had determined that impedance at my peak was actually about 6 ohms with that sub/box/vehicle and that it was safe. For reference, I gained nearly 5dB over daily configuration running that same sub/box at 6 ohm nominal.

Also want to point out that IF you know sub and box specs you should be able to predict impedance at any given frequency since every variable can be converted into ohms, henrys or farrads, but for practical purposes, using a constant voltage source and measuring current and doing the math is probably best. Or to shortcut that, Dayton DATS will give you an impedance graph in a couple seconds.
View attachment 24702


Some googling can break down which variables are what.

Also output from Dayton DATS. This is the wall in my Jeep wired to .7 ohm nominal
View attachment 24703

Nice share man. Yeah, the burp boxes, for sure.

Some my comments around the importance of rise in SPL comps is that I've done daily boxes that win SPL comps with horrible rise surely. Idk what the quality of the competitors were, but I know rise wasn't paid attention to in my design bc it was a daily.

I know that everything contributes to rise, but I've never thought of it quite like an electrical diagram. Thanks for sharing man, that's pretty neat.

 

[Buck 5,000+ posts]

In the past it has definitely been worth knowing what impedance is at your burp frequency to plan coils and amps accordingly, these days possibly less important for most folks considering how cheap we can buy full bridge power. My first 150+ was running my old JBL/Crown A6000 into """1.4 ohm""" while in 4 ohm mode. I had determined that impedance at my peak was actually about 6 ohms with that sub/box/vehicle and that it was safe. For reference, I gained nearly 5dB over daily configuration running that same sub/box at 6 ohm nominal.

Also want to point out that IF you know sub and box specs you should be able to predict impedance at any given frequency since every variable can be converted into ohms, henrys or farrads, but for practical purposes, using a constant voltage source and measuring current and doing the math is probably best. Or to shortcut that, Dayton DATS will give you an impedance graph in a couple seconds.
View attachment 24702


Some googling can break down which variables are what.

Also output from Dayton DATS. This is the wall in my Jeep wired to .7 ohm nominal
View attachment 24703

5db is an ENORMOUS gain. Holy crap dude. Did you go from 145 db to 150 db?

 

[Buck 5,000+ posts]

In the past it has definitely been worth knowing what impedance is at your burp frequency to plan coils and amps accordingly, these days possibly less important for most folks considering how cheap we can buy full bridge power. My first 150+ was running my old JBL/Crown A6000 into """1.4 ohm""" while in 4 ohm mode. I had determined that impedance at my peak was actually about 6 ohms with that sub/box/vehicle and that it was safe. For reference, I gained nearly 5dB over daily configuration running that same sub/box at 6 ohm nominal.

Also want to point out that IF you know sub and box specs you should be able to predict impedance at any given frequency since every variable can be converted into ohms, henrys or farrads, but for practical purposes, using a constant voltage source and measuring current and doing the math is probably best. Or to shortcut that, Dayton DATS will give you an impedance graph in a couple seconds.
View attachment 24702


Some googling can break down which variables are what.

Also output from Dayton DATS. This is the wall in my Jeep wired to .7 ohm nominal
View attachment 24703

Do you have an opinion on the amps that do their 1 ohm power like from 1 ohm to 4 ohms? Example: an amp that says it'll do say 1000w from 1 to 4 ohms?

I wonder if a competitor has had benefits from using one those. JL comes to mind.

 

[hispls 5,000+ posts]

5db is an ENORMOUS gain. Holy crap dude. Did you go from 145 db to 150 db?

147 to high 151s IIRC. Consider my impedance wired to 5.6 ohm nominal was probably 16-20 ohms. Even the big boy Crown amp doesn't make all that much power there but it does put out a lot at 4 ohm. Neodymium motors can give some big impedance numbers.

Do you have an opinion on the amps that do their 1 ohm power like from 1 ohm to 4 ohms? Example: an amp that says it'll do say 1000w from 1 to 4 ohms?

A friend of mine was competing rookie class about 8 years ago with a 500/1 and we got (slightly) better numbers running at .7 than at 3 ohm. Dyno shows the Taramps "smart" 3K made its best power at 2 ohm. The difference for music listening would be inaudible but with competition you really just have to test everything. He was absolutely killing it in the rookie class (up to 2000W limit no test tones no re-bass) doing 142's. He had a couple new children and sold me the sub back, now it's living in my F250, poor numbers in there but I don't haven't made enough space for a proper box.

The whole loudspeaker as a circuit thing was figured out long ago and while it's a bit above my pay grade I suspect that's partly how we can model and predict response.

High impedance isn't necessarily a bad thing, and depending on the region and the competition class, "music" boxes can be competitive.

 

[Buck 5,000+ posts]

Neodymium motors can give some big impedance numbers.

I can see how that would happen.

 

[Buck 5,000+ posts]

The whole loudspeaker as a circuit thing was figured out long ago and while it's a bit above my pay grade I suspect that's partly how we can model and predict response.

It has to be based on the sub, because that's where the power is going. Like your t/s- example: moving X amount of air causes Z amount of resistance in ohms or impedance one. You could just factor in every resistance on the sub, including mechanical, and translate that directly in a singular/total electrical rise number, I would think. Your port is a x b x c tuned to XX hz, that equals Z rise on your sub. Idk testing sounds easier than that LOL

 

[hispls 5,000+ posts]

It has to be based on the sub, because that's where the power is going.

No. Each of those "components" in the circuit is a different variable. If you find the simplified circuit of just a loudspeaker it is different, the coil is an inductor, moving mass and compliance is a capacitor and resistor, etc. Once you add a box behind it that adds resistance and inductance for the spring of the air, add a port and that behaves as a resistance and inductance... and so forth. The key point is that any of those specifics are not just pure resistance but vary by frequency plus whatever pure resistance force.
I do believe that the box design software has all the conversions and math baked in and I doubt anybody has done this stuff long hand since the 70s.
Anyway, if you dig around a bit you can see which "component" corresponds to which variable.

 

[Buck 5,000+ posts]

No. Each of those "components" in the circuit is a different variable. If you find the simplified circuit of just a loudspeaker it is different, the coil is an inductor, moving mass and compliance is a capacitor and resistor, etc. Once you add a box behind it that adds resistance and inductance for the spring of the air, add a port and that behaves as a resistance and inductance... and so forth. The key point is that any of those specifics are not just pure resistance but vary by frequency plus whatever pure resistance force.
I do believe that the box design software has all the conversions and math baked in and I doubt anybody has done this stuff long hand since the 70s.
Anyway, if you dig around a bit you can see which "component" corresponds to which variable.

Thanks for sharing. I really don't know at all, was just guessing. I've never seen a raw conversion. I bet there would be a way to use the overall resistance to define the impedance rise you'll see from the sub, because that's what your powering. Like if you had a formula based around how the sub acts with every single factor that it's exposed to that would change the rise in the coils as it's moving at different frequencies. I bet you could do it that way too, just simple total rise per object or space the sub has to encounter or use.

 

[Buck 5,000+ posts]

And I refuse to ego trip, there's a lot of stuff I don't know about. That's why I stick to my specialty and like experimenting too. Like I was emailing somebody about boxes and talking about 8th order and iirc the quasi-butterworth 12th order or whatever it's called, and horns. Most of the time it's just not even worth it to do, even though it's cool and complicated. So my knowledge on that end is way lower because nobody does them, you know? Just like stuff like this, supply and demand rules.

 

[hispls 5,000+ posts]

I bet you could do it that way too, just simple total rise per object or space the sub has to encounter or use.

But that's not how a circuit works. It's not just additive resistances. Consider when you series two resistances impedance doubles and when you series two capacitors capacitance halves AND vice versa. It would be important to take note of each "component" position in the circuit to see how it's value effects the final impedance. You would need to know which things are doing what and whether they act in parallel or series with other parts of your system.

A horn expressed as a circuit becomes even more interesting because the horn also acts as a transformer between speaker and enclosure and the acoustic load (the air you're trying to play music into).

 

[Buck 5,000+ posts]

But that's not how a circuit works. It's not just additive resistances. Consider when you series two resistances impedance doubles and when you series two capacitors capacitance halves AND vice versa. It would be important to take note of each "component" position in the circuit to see how it's value effects the final impedance. You would need to know which things are doing what and whether they act in parallel or series with other parts of your system.

A horn expressed as a circuit becomes even more interesting because the horn also acts as a transformer between speaker and enclosure and the acoustic load (the air you're trying to play music into).

I'm not saying what I said was a circuit, to be clear. I see what you're saying, I was saying there may be a way just to simply calculate how certain factors cause rise in the sub VC's, not the whole system dynamic.

 

[Buck 5,000+ posts]

I'm not saying what I said was a circuit, to be clear. I see what you're saying, I was saying there may be a way just to simply calculate how certain factors cause rise in the sub VC's, not the whole system dynamic.

Like just for people doing ported boxes, some general type thoughts.

Like an example would just be if you test rise between different port radiating sizes over a frequency bandwidth, leaving all other stats static. That's what I mean, not calculating every factor, but more relative calcualtions based around what people already have in their system. Like they'll know what voltage the subs are seeing if they already have the box everything set up, and to improve upon that, someone could test rise like I was saying with different ports. So if you want to get closer to a certain goal, you can take those generalities and apply them to the next box you build, without getting too complicated. Like there has to be a rise factor specifically based around the size of your port. If we could single out that factor and show the difference between say 8 in^2 per cube and 16 in^2 per cube or 20 even in relations to rise as the woofer plays across a frequency, people will absorb that. You could do the same with enclosure airspace. Or even round ports vs square ports. That would be real world proof too, not just numbers on a program. Sound and electricity are dynamic and alive, real world results are where it's at. We still don't understand electricity that well IMO. It does stuff we still don't understand.

I work on the theory of KISS: Keep It Simple Stupid. You'd want to develop something that most people can use with ease. You see what I'm saying? I'm sure some people have done this before.

I'm not even saying I'm right on any of this, I'm just freely thinking about easier ways for people to get close to the goals they want without needing a physics degree or an electrical engineering degree.

 

[Buck 5,000+ posts]

Even with an enire system calculated in a circuit, you can't control things like the weather, air pressure, temperature, humidity on any given day. That's going to change your system's relationship with the air; it'll act differently. My point sort of is that even with the most specific calculations, you can't predict what nature itself does. Both sound (air properties) and electricity are ever changing properties in our world. Like you can't predict the concentration of magnetism or electromagnetism coming out of the earth's core in your location, and that's going to change the way your electronics act, to whatever extent. Even the amount of cosmic and solar radiation coming in through the atmosphere are going to change the way electronics act, to some degree. There's just things you can't predict, you can get close, but there's diminishing returns when you try to calculate everything so precisely, with there still being many factors you can't really predict.

 

[Buck 5,000+ posts]

But don't get me wrong, I see what you're saying and I'm not arguing against you at all on those diagrams and what they mean.