box rise question

people always argue this and there never has been a clear answer

so my buddy says

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Kinda reminds me of a redneck's last words: "Hey, watch this"

yes and no......... each box different, infact i have seen same air space and port, but postion of sub in box made difference........ like to try diflection panel behind sub to see if it affects it

My 3.2cu box rises to 3.1 @ 50hz whereas my friends box @ 4.5cuft only rises to 2.2 (both wired down to .7), but box rise is irrelevant seeing as impedence is always changing

ok, i feel REALLY stupid. but wtf is box rise?

Matt

When your bass is slapping so hard your enclosure levitates...

=P

ok, i feel REALLY stupid. but wtf is box rise?
Matt

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With a sealed enclosure, as you approach a free-air environment (larger box) the impedance will increase.

With a ported enclosure, you are also introducing a pronounced dip (at tuning) with a peak a bit above tuning.

Many outside factors can also affect impedance (such as temperature, number of coils, etc.) - but understand that impedance rise is only a 'bad' thing from the amp's perspective - as it will put out less power - but the highest efficiency of the system will be around the same point as the highest impedance.

oh! ok, never heard it called box rise. with Tapped Horns when u use multiple drivers in a single horn you can get multiple impedance peaks/ more overall efficency.

Matt

Impedence rise varies with frequency. At some freqs it actually drops. The reason we call it "impedence rise" is because we only measure it for SPL burps and only at our burp frequency. It means absolutely nothing for most of you on this site who play music through your stereo. It will cause you to damage your equipment.

Impedence rise does not have a predictable pattern or formula to calculate it because as stated, there are quite a few things that can manipulate it.

Impedance 'can' be plotted to a reasonable degree (though agreeable, real-life vs. computer simulation leaves some discrepancies)

Impedence rise varies with frequency. At some freqs it actually drops. The reason we call it "impedence rise" is because we only measure it for SPL burps and only at our burp frequency. It means absolutely nothing for most of you on this site who play music through your stereo. It will cause you to damage your equipment. Impedence rise does not have a predictable pattern or formula to calculate it because as stated, there are quite a few things that can manipulate it.

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Impedance 'can' be plotted to a reasonable degree (though agreeable, real-life vs. computer simulation leaves some discrepancies)

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Lol. I know that there are programs that show a projected impedence curve. Compare that after clamping each freq and you'll understand just how wrong you are good sir.

...the projected-versus-real impedance 'values' may be a bit off, sure (and I don't know of any software that takes speaker fatigue, power and/or port compression, etc., and the resulting changes in the T/S parameters into account) but the 'shape' of the curve will be fairly reliable.

If perhaps you are referring to how putting the 'projected' system into a closed, reflective environment (the car) is going to influence this, then I would agree. Calculating the implications of cabin gain are going to be quite messy...

Your comment stops just short of throwing the baby out with the bathwater though.

=)

Lol. I know that there are programs that show a projected impedence curve. Compare that after clamping each freq and you'll understand just how wrong you are good sir.

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...the projected-versus-real impedance 'values' may be a bit off, sure (and I don't know of any software that takes speaker fatigue, power and/or port compression, etc., and the resulting changes in the T/S parameters into account) but the 'shape' of the curve will be fairly reliable.
If perhaps you are referring to how putting the 'projected' system into a closed, reflective environment (the car) is going to influence this, then I would agree. Calculating the implications of cabin gain are going to be quite messy...

Your comment stops just short of throwing the baby out with the bathwater though.

=)

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We are both saying things we aren't going to prove. I made a statement I know to be true through my many SPL builds and testing. You made a statement based on a graph you saw in some software. Then you went on to admit that the graph is worthless when you actually go to USE your woofer and enclosure and tried to mock me for being accurate and telling the truth. You must be a democrat. With what I've seen so far, a discussion would be fruitless.

On the contrary...

I'm not sure I've saved my past graphs here, but I'll fire up WinISD and my DATS this evening, if that's what your wanting to see...

Software is NOT worthless - (your putting words in my mouth).

I've asserted that a software plot is quite helpful, and stand by that. You obviously have your own methods for planning a woofer enclosure, and that's fine, but I thought we were having a civilized conversation here.

You have the scorn in your voice of someone that's spent countless hours planning something out, and been disappointed with the actual result (such is the life of SPL'er - I know...), but I believe you are referring to conditions way outside the scope of the original question.

P.s. I consider myself political affiliation Independent - will have to save your Obama hatin' for another thread. =)

We are both saying things we aren't going to prove. I made a statement I know to be true through my many SPL builds and testing. You made a statement based on a graph you saw in some software. Then you went on to admit that the graph is worthless when you actually go to USE your woofer and enclosure and tried to mock me for being accurate and telling the truth. You must be a democrat. With what I've seen so far, a discussion would be fruitless.

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