Impedance Rise

[Nikuk 1]

I've been meaning to write this up and post it here for sometime... thankfully Aaron pushed me a little.

A couple of quick comments: I've tried to make this as straight forward and digestible as possible; I've explained these things to the best of my knowledge... bear in mind, I am no Electrical Engineer.

What follows is the result of monthss of research and hours of playing / testing my own equipment.

Lastly - I'll leave this locked until Denim gets a look at it.

-Nick

[Nikuk 1]

At your service

[Nikuk 1]

Resistor method:

You are going to need the items mentioned above, but, in addition:

• An additional VOM/DMM would be helpful.
  * A 10 ohm resistor. Preferably non-inductive and able to handle 10 watts or better.
  

That

[Nikuk 1]

There are other ways to do this. Though, for me, they are the same difficulty level (low). It

[Nikuk 1]

Now

[Nikuk 1]

Thanks Denim.

[Acidburn 10]

sheesh, thats an amazing write up Nick

now i just need to get off my lazy ass to install and test my subs

[Tirefryr 1,742]

What a waste of time. I already know this much. You suck!

On a serious note, I can't wait for Dave, Mike, or Nick to enlighten us more in the actual EE department. I'd love to get into further deyail on this.

One thing I've been wondering is how these newer amps coming out with their ability to produce a continous amount of the same power into any nominal impedance account for the shifts in impedance. I know the JBL/Crown amps are wired differently for different nominal loads, therefore, I'm led to believe they will not work to full potential with shift involved. The JL and PG amps, I just have no clue on.

[Nikuk 1]

Yes Ryan, I know you know this. So do some others... but lot's of folks dont know, or dont know how to account for it.

Yea, I'm curious in the same fashions.

Someone asked me to post this up...

-Nick

[Supa_c 1]

If only my DMM werent broken

[Tirefryr 1,742]

Yes Ryan, I know you know this. So do some others... but lot's of folks dont know, or dont know how to account for it.

Yea, I'm curious in the same fashions.

Someone asked me to post this up...

-Nick

I was just kidding. I actually like reading things like this that actually get into detail. It helps to refresh yourself once in a while. Keep the brain functinononuibm mnbo/

Whoops.

[Nikuk 1]

you know... thats a damned fine point.

I dunno much about the Crown, with it being so out of reach...

Seperate circuits? It's not like you can make the same board into a variable output and still step up to that much voltage...

[ANeonRider 3]

Good post, nothing new, but always nice to have there for reference

[Aaron Clinton 2,372]

you know... thats a damned fine point.

I dunno much about the Crown, with it being so out of reach...

Seperate circuits? It's not like you can make the same board into a variable output and still step up to that much voltage...

thats one reason why I want to try the Crown amps so bad, they were awesome in club's and bars that I worked in, rock solid and just abused the speakers while holding a low temperature the whole time

[dave_Edwards 1]

Nice write up----I myself am in stages of testing differant classes of amplifers and back EMF and impedence rise within the amplifer itself-----I am also trying to get a patent on one of my new ideas----will tell you when/if I get it.

As for the write up-----you covered alot of questions anyone would have about the little known(and mostly understood----or not cared about) subject.-----Jeeesh I'm tired. B)

[Aaron Clinton 2,372]

so there can be box and amplifer impedance rise?

what I am curious about a dual 2 ohm sub wired in parallel to a 1ohm stable mono amp could possibly end up showing a true final impedance of around 1.75 to 2 ohms maybe?

[Nikuk 1]

so there can be box and amplifer impedance rise?

what I am curious about a dual 2 ohm sub wired in parallel to a 1ohm stable mono amp could possibly end up showing a true final impedance of around 1.75 to 2 ohms maybe?

<{POST_SNAPBACK}>

Yes, different amps will play into it. Maybe not much, but yes. This is really where the amp's dampening factors come into play. Read up about the EMF link when you have time. You;ll get a better Idea.

[jellyfish420 0]

so what exactly do i do with this graph now? i did all of this and have a graph. but what does it tell me? i now know my box is actually tuned @ 23Hz. but that is all. look at this and tell me what i'm looking for.

[Nikuk 1]

what that tells You is that You have a suprsing spike at 48-49 hz...? You say Your box is tuned to 25? Odd - impedance usually spikes around tuning, IMExperiance.

For example, my DD 99 with Dual 0.9 coils - each coil reads 9.25ohm in box @ 47hz (tuning).

Okay, well, I'll ASSUME that when You adjusted the sensitivity on the amp, You set it at 50hz (Per James' tutorial)... if so, You did something like: 40 volts x 1 ohms (for example) and called it a day.

What this graph shows you is that in real terms, you set the amp for 40 volts x 3.2 ohm actual. Instead of getting 1600 watts, You are getting 500 watts. A difference of 1100 watts.

I don't know what the dcr is for your setup though. RLP's are Dual 4.0ohm are 6.1 in series... so standing dcr should be 3.05 per coil (standard TC coils ). If You wired all (4) coils in parrellel, then You should see 0.7625 actual free air (27.8hz - fs).

Now, per Your work up there, at 28 hz, actual in box impedance is: 1.5ish.

Make sense?

[jellyfish420 0]

why is 23Hz odd? i though impedance was at its lowest at tuning? thats real sad about the big spike. you were pretty close with the .7625...it measures .8. i guess this is where the amps that keep a constant V at varing impedances shine.

after seeing this i think i might look into a diff amp. i read somewhere that most (decent) amps will run .6ohm under rated...so looking at the graph would it be safe to assume that i would be ok getting an amp that does around 1200@2ohm. its sad cause i know my last box peaked (db) at 50Hz, and by ear this one sounds like its in the 40ish range....but up that high i'm lucky to be getting 250w a piece

[Tirefryr 1,742]

I love sealed enclosures.

[Supa_c 1]

I love sealed enclosures.

<{POST_SNAPBACK}>

queer !

[Tirefryr 1,742]

I love sealed enclosures.

queer !

Don't make me tell your secret!

[Nikuk 1]

why is 23Hz odd? i though impedance was at its lowest at tuning? thats real sad about the big spike. you were pretty close with the .7625...it measures .8. i guess this is where the amps that keep a constant V at varing impedances shine.

after seeing this i think i might look into a diff amp. i read somewhere that most (decent) amps will run .6ohm under rated...so looking at the graph would it be safe to assume that i would be ok getting an amp that does around 1200@2ohm. its sad cause i know my last box peaked (db) at 50Hz, and by ear this one sounds like its in the 40ish range....but up that high i'm lucky to be getting 250w a piece

<{POST_SNAPBACK}>

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.

Looking at your graph, with that box the lowest imp is 1.2ish. Any amp, stable to 1ohm will be just fine for music.

As far as varying V goes... You still need the amp to adjust the amperage as well.. to maintain power.

If you were to try to burp these @ 50hz, then You would want a BIGASS amp that is 4ohm stable. FOR BURPS, not music.

But otherwise, I hope the thread here helped You.

-Nick

[Nikuk 1]

......after seeing this i think i might look into a diff amp. ....

<{POST_SNAPBACK}>

That's why SPL competitors can run 134KW nominal to a (9) 3kw woofers.