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View Full Version : How does box rise work?

shpatb
07-24-2012, 10:01 AM
What causes box rise? Area of box? Sealed vs ported? How can a person calculate box rise? Right now I have two, 2 ohm subs, in compartmentalized box with about 1 cube each sealed, or other box compartmentalized with over 3 cube each ported for my subs. Just wondering what kind of ohm load my amp is actually seeing.

Flex68
07-24-2012, 10:07 AM
How can a person calculate box rise?

Copied and Pasted this into a file I saved....don't recall where it came from:

To calculate “box rise” you need an AC clamp meter and a DMM. You will need to measure the AC voltage output going to each of your subs (or if they're bridged just the wires going into the amp). Once you get the AC voltage you will need to find the AC current. You do this by clamping the negative wire going to the set of speakers.

Example:

You clamp your wire and get 38.6 amps of current
You probe the + & - wires and get 61.7 volts

Next you would take the 61.7 volts and multiply the 38.6 by it to find your MAX power which would be 2381 watts

Next to find out your impedence rise you would divide the voltage 61.7 by the amperage 38.6 which would be 1.59 ohms

So if you were to have a nominal or starting resistance of .5 ohms you would have a rise of 1.09 ohms, for an overall reactive load of 1.59 ohms.

kushy_dreams
07-24-2012, 10:08 AM
there is no way to calculate it, only way to find out is to clamp your amp, its different at every frequency

wickedwitt
07-24-2012, 10:13 AM
There is none if you bolt it down. :naughty:

CAT MAN
07-24-2012, 10:16 AM
There is none if you bolt it down. :naughty:you saw that on caco also? lol....

Flex68
07-24-2012, 10:20 AM
there is no way to calculate it, only way to find out is to clamp your amp, its different at every frequency

Technically you're correct, but if you play you standard/favorite genre of tunage and set the AC clamp meter to record the max via a "Hold" function, you're going to be able to get a pretty good idea of what your rise is....

wickedwitt
07-24-2012, 10:32 AM
you saw that on caco also? lol....

Yep, that was freaking hilarious.

shpatb
07-24-2012, 10:35 AM
Do sealed boxes get more rise than ported? I think I'm going to go back to ported because the output from sealed is pretty poor, I mean they sound nicer and have the punch that I like but when I listen to rap it's just not the same... I'll try to borrow a clamp and DMM and see what happens.

Fiendstolemyamp
07-24-2012, 10:38 AM
It's not something you need to worry about playing music.

LBC
07-24-2012, 10:57 AM
Technically you're correct, but if you play you standard/favorite genre of tunage and set the AC clamp meter to record the max via a "Hold" function, you're going to be able to get a pretty good idea of what your rise is....

No. He was dead-on correct. Your rise changes with every frequency. Sometimes there is no rise. There is impedence drop. Google: impedence curves for loudspeakers and you'll get a better understanding. You can't clamp 1 frequency and then assume you're rising that much on every other frequency. That isn't true. You rise the most at your port's peak frequency. That is going to be your loudest frequency also. This is all pretty simple stuff. There are just so many people out there spreading bad information it's kind of getting out of hand.

Flex68
07-24-2012, 11:14 AM
No. He was dead-on correct. Your rise changes with every frequency. Sometimes there is no rise. There is impedence drop. Google: impedence curves for loudspeakers and you'll get a better understanding. You can't clamp 1 frequency and then assume you're rising that much on every other frequency. That isn't true. You rise the most at your port's peak frequency. That is going to be your loudest frequency also. This is all pretty simple stuff. There are just so many people out there spreading bad information it's kind of getting out of hand.

I've read enough of your idiocy on other threads to discount anything you say....especially since you apparently didn't even read the entirety of the one sentence I posted.

Go back to nuthugging cthedinger, and spreading more of your disinformation about how his product compares to others in the industry.
Anyone on here who has half a brain knows how irrelevant a little lamb you are, lol.

LBC
07-24-2012, 11:17 AM
I've read enough of your idiocy on other threads to discount anything you say....especially since you apparently didn't even read the entirety of the one sentence I posted.

Go back to nuthugging cthedinger, and spreading more of your disinformation about how his product compares to others in the industry.
Anyone on here who has half a brain knows how irrelevant a little lamb you are, lol.

What are you talking about? All you have to do is look it up. I'm not going to come in here and lie... and I wasn't attacking you. You're just not correct and I attempted to properly inform you. Calm down.

Falcons
07-24-2012, 11:22 AM
Ish just got real.

Flex68
07-24-2012, 11:47 AM
What are you talking about? All you have to do is look it up. I'm not going to come in here and lie... and I wasn't attacking you. You're just not correct and I attempted to properly inform you. Calm down.

As usual, you wish to bandy semantics.
You are trying to correct something that did not need correcting.

Technically you're correct, but if you play you standard/favorite genre of tunage and set the AC clamp meter to record the max via a "Hold" function, you're going to be able to get a pretty good idea of what your rise is....

Both you and kushy are technically correct that the varying freq's in music will not allow one to pinpoint a single, accurate impedance to be able to say, "I have a xx.xx box rise."
However, if one follows the very basic guideline I posted, and play one's favorite "style" of music, then one can at least get a general idea of what to expect in terms of box rise, which allows one to account for something rather than nothing.

Your statements are kind of like someone saying they would rather know zilch if they can't know it all; its gotta be black or white, fukk all that gray; etc, etc.

So, again, I say to you, P!ss off

LBC
07-24-2012, 11:56 AM
As usual, you wish to bandy semantics.
You are trying to correct something that did not need correcting.

Both you and kushy are technically correct that the varying freq's in music will not allow one to pinpoint a single, accurate impedance to be able to say, "I have a xx.xx box rise."
However, if one follows the very basic guideline I posted, and play one's favorite "style" of music, then one can at least get a general idea of what to expect in terms of box rise, which allows one to account for something rather than nothing.

Your statements are kind of like someone saying they would rather know zilch if they can't know it all; its gotta be black or white, fukk all that gray; etc, etc.

So, again, I say to you, P!ss off

Ok, I'm glad you clarified. Your posts prove that you know nothing. The clamp results need voltage and current. You assume you can just look at the peak current and know something. You can't. That doesn't make sense. Nobody would know you aren't smart if you'd stop talking so much.

Flex68
07-24-2012, 12:09 PM
Ok, I'm glad you clarified. Your posts prove that you know nothing. The clamp results need voltage and current. You assume you can just look at the peak current and know something. You can't. That doesn't make sense. Nobody would know you aren't smart if you'd stop talking so much.

Jaysus, you're an idiot..... so ur insinuating that someone should clamp to find the lowest current so they can adjust/account for minimum or negative box rise?

Using the "Range" and "Hold" functions on the clamp meter will tell 95% of folks what they wish to know using with their standard music selection/preference playing, since surely most are looking for nominal - to - max box rise.

I am not the one who needs to stop talking, here, poodlenutz, lol

LBC
07-24-2012, 12:22 PM
Jaysus, you're an idiot..... so ur insinuating that someone should clamp to find the lowest current so they can adjust/account for minimum or negative box rise?

Using the "Range" and "Hold" functions on the clamp meter will tell 95% of folks what they wish to know using with their standard music selection/preference playing, since surely most are looking for nominal - to - max box rise.

I am not the one who needs to stop talking, here, poodlenutz, lol

You missed the point genius. What do you multiply that number with? At this point everyone realizes that you need the current AND the voltage. You are explaining how to find the maximum current the amp puts out over a specific period of time. How would a person get a relevant voltage to plug into the calculation? This is why you should stop talking. It doesn't matter what you say here.... it will prove that you have NO CLUE what you're talking about.

Flex68
07-24-2012, 12:28 PM

LBC
07-24-2012, 12:30 PM

AKA you realized you have no idea what you're talking about, decided to throw a few putdowns and exit before you do any more harm to your already tarnished name. Awesome idea bro.

kushy_dreams
07-24-2012, 02:22 PM
Flex- I know you're not an idiot and I get what you're trying to say but I'm gonna have to side with lbc on this. Music has a range of different freqs and rise will be different at every note and because of that the only true way to know how much rise you are incurring is to clamp a variety of single note tones and then graph the results.

Flex68
07-24-2012, 02:44 PM
Flex- I know you're not an idiot and I get what you're trying to say but I'm gonna have to side with lbc on this. Music has a range of different freqs and rise will be different at every note and because of that the only true way to know how much rise you are incurring is to clamp a variety of single note tones and then graph the results.

Thank you.
That is cool, but anyone who wants to obtain basic ranges or a "peak" box rise is going to be able to do that via the method I posted.
Def going to work for most daily drivers....In fact, for those seeking a basic idea of how much box rise they have, I don't know any other way to go about obtaining such info.
Folks in SPL comp's are likely going to go deeeeeper, but such likely doesn't apply to the original question OP posted, and thus the "caveat" that I put in my second post in response to yours.

Regardless, I still say that LBC never even bothered to read my two posts in their entirety before attempting to "rebut."
Don't expect much more from his ilk, anyway......

Its all good

Kangaroux
07-24-2012, 03:08 PM
Holy butthurt batman.

n8skow
07-24-2012, 03:08 PM
You can't calculate impedance rise by reading AC voltage alone, (see Ohm's law). You would also need an ammeter to clamp the AC amperage (Voltage divided by Amperage = impedance), and both numbers vary greatly throughout the musical spectrum (and is influenced by your enclosure design, as well as the driver parameters).

Peak hold will be worthless while playing music because you wouldn't be measuring peak voltage and peak amperage at the same time. You would either need to take measurements one frequency at a time, or use a device capable of plotting both measurements simultaneously (as far as music is concerned).

LBC
07-24-2012, 03:11 PM
You can't calculate impedance rise by reading AC voltage alone, (see Ohm's law). You would also need an ammeter to clamp the AC amperage (Voltage divided by Amperage = impedance), and both numbers vary greatly throughout the musical spectrum (and is influenced by your enclosure design, as well as the driver parameters).

Peak hold will be worthless while playing music because you wouldn't be measuring peak voltage and peak amperage at the same time. You would either need to take measurements one frequency at a time, or use a device capable of plotting both measurements simultaneously (as far as music is concerned).

Exactly. It's good to know there are others on here who understand.

07-24-2012, 03:19 PM
UniBox - Unified Box Model for Loudspeaker Design - Kristian Ougaard (http://audio.claub.net/software/kougaard/ubmodel.html)

shpatb
07-24-2012, 03:22 PM
Thanks guys, for the information and entertainment.

n8skow
07-24-2012, 05:55 PM
The bottom line is - don't treat impedance rise as a 'bad' thing, it's simply a function of physics.
All setups are going to have some rise, learning to manipulate it, that is the trick.

wenn_du_weinst
07-24-2012, 05:57 PM