acceptable amount of impedance rise?

ok, we all hate imp rise, but how much is considered bad or abnormally high? Have some of you veterans determined a percentile of impedance rise that is common or very high? I would consider 0.4 or less to be excellent (or maybe I'm wrong, and depending on the "goal" resistance how much the margin or % should be) but what is just way too much? I built a box for a friend and clamped his amp this weekend, i have the gain barely up because his sub is a little more than half the rms of the amp.

His sub is a Dual 2ohm 12" L7 wired in parallel, i barely cranked the gain up and clamped 695w rms on a 60hz tone
40.9 VAC
17 amperes
= 2.4 resistance

Amp: ED Nine.1
manufacture rating 450w x1@4, 900w x1 @2, 1200w x 1@1ohm @12.5v

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The only idea i have right off the top of my head to help attenuate this rise is upgrade his speaker wire a little, we used 14 AWG for starters and I'm going to bump him up to 10 AWG. Any idea's or input? Comments? Insults or criticism?

alot of amplifiers wont like .4 after rise and would most likely clippy

i have always told myself that 1.4-.9 is where i wanna be after rise this has always been where i saw the most power from my amplifiers on 16v

now on 12v its a differant story since you can run with less rise due to having less voltage

Keep in mind that your lowest impedence will occur at box tuning. If you tuned your box to 40hz, then your nominal imp plus a little will occur at 40hz. At 60hz it could be anywhere from 2 -8ohm. The imp rise depends on the box size and port tuning.

sanman wrote:

alot of amplifiers wont like .4 after rise and would most likely clippy

i have always told myself that 1.4-.9 is where i wanna be after rise this has always been where i saw the most power from my amplifiers on 16v

now on 12v its a differant story since you can run with less rise due to having less voltage

I mispoke i guess, i didn't mean .4 after rise, i meant .4 on top of the dc resistance load. I forgot to measure the dc resistance of the coils in parallel, i'm sure they are readying .8-1.2 ish, and i'm seeing a double that in impedance.
I'm going to up my wire size to hopefully reduce the voltage drop and maybe put a layer of glass inside the box to see if it smooths things out. I used 3 4" aero's to help prevent turbulence and rounded edges here and there. After i cut the amp off i measured the resistance of the speaker wire at the amp, while still connected and read 1.5 ohms. I didn't trust the reading much because i do not know if it is also reading a parallel resistance inside the amp as well.
Also, you say you want 1.4-.9 after rise, but is this wiring down to a half ohm load?

XFL-Leader wrote:

Keep in mind that your lowest impedence will occur at box tuning. If you tuned your box to 40hz, then your nominal imp plus a little will occur at 40hz. At 60hz it could be anywhere from 2 -8ohm. The imp rise depends on the box size and port tuning.

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Just playing around with this box for now to see what it does, it's tuned in the upper 50's because my friend wants to try a little 0-600 to see what happens. I'm trying to get him interested in spl. H has a 3rd gen eclipse and i heard those resonate in the mid 50's. I'm thinking about dropping his box resonating freq down after we get on the meter to get a base reading.

actually my sdime almost always had 1.2 in rise no matter what my starting ohm load was

the cactus pf600.1 at .25 would rise to .9 but that was due to lack of power ill guess, but was quite impressive

so, no need to freak out if i'm rising from 1.2 up to 2.4 ish.. which is 2 times as much resistive load. In which your saying in some cases you saw over triple.

I guess all i can really do is live with it and improve where possible.

Now.. ready for a possible dumb question? Sure you are...

Seeing as how the vehicle is an extension of the box.. you think it possible was a bad idea that i took these reading while the back hatch was open? I guess i should have crawled in to the back seat and done this with the hatch closed..

Yea close it! Even closing the door a little will change tuning and rise!

Well, personal fail then.. guess i get to re-do this..

i got almost a 3 ohm rise ....lol

The_Rowlands wrote:

i got almost a 3 ohm rise ....lol

what was the dc resistance?

for me right now i start at 1 and go to 2.9 to 3.4 depending on how i stand/sit at the door.

back when i was using a us-2000x at 4 ohms i was rising to around 12 ohms... lol

best part, still got 1000 watts out of it....

well rising from 1 ohm dc to an impedance of 3 is no different than 4 to 12 as far as the amp is concerned, but i guess as long as you still got your true rms power, then no worries..
Sadly, out of the thousands of setups i have installed working at shops, i never had clamped an amp or tested for an actual impedance load, because it never really mattered, and back when i competed i was 18-19 years old and had not gotten my electronics degree yet, so i didn't even understand the difference between resistance and impedance.
Now that i am actually trying to get down to business on this, i was just curious what kind of improvements people have seen and have improved from there starting rise, doing this and that to attenuate it, and what kind of improvements have been made.. killing off half the rise? barely any...

I normally see 3-4x my nominal imp....example wired to .25 I rose to .82