Impedance Rise

[jellyfish420 0]

so my box is tuned @ 49? cause i'll play tones all the way down to 20 and around 20-25 is where the cone almost stops, and it feals like i turned the a/c on max, thru the port

[Supa_c 1]

I love sealed enclosures.

<{POST_SNAPBACK}>

queer !

<{POST_SNAPBACK}>

Don't make me tell your secret!

<{POST_SNAPBACK}>

oh no you wouldnt

[EFFENDI 0]

secret? what secret?

[jellyfish420 0]

It's odd because ported's generally PEAK around the tuning freq. Not dip to the lowest. But thats a generalization... I dunno the SS woofers well enough to go furhter there. Soory.

<{POST_SNAPBACK}>

here's another question nick...if the above is true than what is this...

i did another graph and went down to 11Hz this time. a couple are off the graph...11Hz=10ohm, 12Hz=12.9ohm, and 13Hz=6.83ohm. how would i flatten out the impedance? i know a diff box...but what aspect of the box changes what? ie. smaller port=peakier or smaller box = flatter...you get the point. here's the new graph...

[Nikuk 1]

bbp6 doesnt do a bad job of predicting it, but it doesnt account for emf ripple in the motor... nor does it account for the damping factor of the amp.

Each of those things contribute to imp rise. As does port area, the shape of the box, and anything that effects the electrical Q of the woofer. It's hard to explain, and quite a bit of that is over my head as yet. To tell You the truth, I dunno why You have such a peak an octave above Your tuning / fs.

Maybe we can get Dave Edwards to chime in on that again.

To try to get it down, i usually try my hand at internal loading, or reflection boards, resin, upping port area.

-Nick

[Aaron Clinton 2,372]

Nick I know you saw that loading wall in the Pioneer truck from Nationals last year,

you think that it would have any advantage in smaller classes? and can I ask how does the dampening factor affect the amp effect the impedance? (I understand it deals with control of the driver, hence the reason I want Zapco amps so bad,)

[Nikuk 1]

the loading wall - Yes it can help in non-extreme classes. Usually, they are not needed in street / daily type boxes, as You won't 'hear' the difference.

The other thing, it's hard to get them to show a benefit in street type comp. classes, from what I understand. I spent a few days trying it with my stroker in the trailblazer... after 10+ attempts i'd gained 0.2 or so.

Dampening... basically the electromagnetic design of the motor (like any electric motor) has feedback voltage. The dampening factor of the amp can cancel / absorb that back voltage... allowing more efficient use of the power that the amp is putting into the woofer.

Lemme find a link, I suck at explaining LoL

[Nikuk 1]

Magnetic effects. A driver motor is subject to all of the same considerations as a rotary DC motor. Therefore, one important thing to recall is that when a DC motor is turned, it becomes a generator. Even when running, a motor's inductance will generate a "back EMF" - a voltage opposite of that which is driving it. All motors, even linear motors, exhibit this effect. In a speaker, it means that at the same time as an amplifier is trying to drive the speaker, the coil in the speaker is simultaneously trying to drive a counter-signal back into the amplifier. How successful it will be is determined by the damping factor of the amplifier. For the speaker designer looking to achieve maximum linearity, dealing with or counteracting back EMF is a crucial part of the design process. A side effect of back EMF is that the magnetic field in the gap distorts the flux in the gap as the VC moves.

www.ldsg.com

That covers more about the back emf then the dampening... but it's the same topic - just fromthe woofer side instead of the amp side.

Hope it helps.

[Aaron Clinton 2,372]

[Nikuk 1]

try... http://ldsg.snippets.org/motors.php3#MAGNETIC

[jellyfish420 0]

bbp6 doesnt do a bad job of predicting it, but it doesnt account for emf ripple in the motor... nor does it account for the damping factor of the amp.

Each of those things contribute to imp rise. As does port area, the shape of the box, and anything that effects the electrical Q of the woofer. It's hard to explain, and quite a bit of that is over my head as yet. To tell You the truth, I dunno why You have such a peak an octave above Your tuning / fs.

Maybe we can get Dave Edwards to chime in on that again.

To try to get it down, i usually try my hand at internal loading, or reflection boards, resin, upping port area.

-Nick

<{POST_SNAPBACK}>

reflection board...like a board in front?? internal loading???? and upping port area...you seen my box, ain't making that thing any bigger w/o doing a full blown wall the though has crossed my mind though.....

in your experiance does tuning higher usually flatten the rise out or make it peakier?

because i was thinking of getting inside my box with a saw/something, and cutting the port down, then adding a 4x4 to fill in some of the room, and try to get it to around 6ft^3net @ ~30. i've never had a box tuned this low before and i thought it would be cool as hell....but its kinda overkill for car, HT's a diff story but in the car i think i'd rather have my little hump in responce back.

[mrray13 30]

ok, i just plotted my enclosure, using a clamp meter, at 50 out 80 (75 is where my gains are set to peak) on the volume knob.

what does this do for overall impedence at the higher volumes? will it change (not referring to amp and volt readings, but do impedence total)? do i need to test again at full tilt?

i'll get it graphed out later...i did get a reading of 26.5 volts at 60 on the volume knob..lol....15 more to go..hehe

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[jellyfish420 0]

ok, i just plotted my enclosure, using a clamp meter, at 50 out 80 (75 is where my gains are set to peak) on the volume knob.

what does this do for overall impedence at the higher volumes? will it change (not referring to amp and volt readings, but do impedence total)? do i need to test again at full tilt?

i'll get it graphed out later...i did get a reading of 26.5 volts at 60 on the volume knob..lol....15 more to go..hehe

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

<{POST_SNAPBACK}>

it WILL make a differance...how much? not likely to be that much, but maybe. the reason is when coils warm up (more power) the impedance goes up. the heat in the wire raises resistance...make sense?

[mrray13 30]

ok, i just plotted my enclosure, using a clamp meter, at 50 out 80 (75 is where my gains are set to peak) on the volume knob.

what does this do for overall impedence at the higher volumes? will it change (not referring to amp and volt readings, but do impedence total)? do i need to test again at full tilt?

i'll get it graphed out later...i did get a reading of 26.5 volts at 60 on the volume knob..lol....15 more to go..hehe

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

it WILL make a differance...how much? not likely to be that much, but maybe. the reason is when coils warm up (more power) the impedance goes up. the heat in the wire raises resistance...make sense?

yeah..i did a couple of readings...the sub was plenty warmed up..lol..

btw, what's the formula to figure real world power? at about 70 outa 75, i got just over 70 volts of output, at 10.11 or 11.11 ( i can't remember) amps at 52hz....(i was just goofing around)

also, how in the hell do i make a graph on excel?? i have no clue as to how to use it....does anyone already have the spreadsheet or what ever with the formula (v/a=i) so that i can just input the damn numbers?

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[Nikuk 1]

70 vac, 10.1 amps = 707.0 watts or 6.931 ohm

*edit*

Told yah the Mojo woulda been fine

[Nikuk 1]

Shoot me Your list... I'll plug it into excel and figure out a way to host it.

[mrray13 30]

70 vac, 10.1 amps = 707.0 watts or 6.931 ohm

*edit*

Told yah the Mojo woulda been fine

that is weak!!! and it got me a 144.4 outlaw...fo go figure..

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[mrray13 30]

Shoot me Your list... I'll plug it into excel and figure out a way to host it.

ok...

it'll be right over..lol..

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[Nikuk 1]

70 vac, 10.1 amps = 707.0 watts or 6.931 ohm

*edit*

Told yah the Mojo woulda been fine

<{POST_SNAPBACK}>

that is weak!!! and it got me a 144.4 outlaw...fo go figure..

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

<{POST_SNAPBACK}>

for the ump-teenth time... that's not a bad score for Your setup. And now especially, You can see why.

If You could triple power ACTUAL You'd be looking at a theoretical 148.4ish. Get my point? LoL

[mrray13 30]

70 vac, 10.1 amps = 707.0 watts or 6.931 ohm

*edit*

Told yah the Mojo woulda been fine

that is weak!!! and it got me a 144.4 outlaw...fo go figure..

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

for the ump-teenth time... that's not a bad score for Your setup. And now especially, You can see why.

If You could triple power ACTUAL You'd be looking at a theoretical 148.4ish. Get my point? LoL

yeah, i know..lol...

i've got plans..hehe

but ygpm.... mrray13@gmail.com

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[Nikuk 1]

YGM

[mrray13 30]

i've got it done..lol...

i've just got to get it emailed from the wife's computer to mine and i can upload it...lol..

jsut as a screen pic...if u wnat it emailed...maybe..lol

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[djjdnap 78]

Ok, so if you are playing a song with varying freqs, why does 1 spike really matter?

[mrray13 30]

Ok, so if you are playing a song with varying freqs, why does 1 spike really matter?

it doesn't really....but when ur playing tones and trying to break 150....

btw, here's my graph....

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[Tirefryr 1,742]

YOu guys and your fart machines.

Funny thing is, most people never realize how much this will affect your typical DD sytem.

Yeah, my amp puts out 111111111111111111111000000000000000000000 watts at 1 ohm no matter what the impedance. I know, I designed and built it myself.

***Disclaimer***

The owner of this post is a theoretical genious and should nowforth be considered a car audio god amongst men. Further note, he is also a moronic fool who has a gas problem. Viva la Taco Bell!