Impedance Plots (POST THEM HERE FOR DISCUSSION)

[rocking.that.eclipse]

4 hours ago, WalledSonic said:

@rocking.that.eclipse , can you guys measure impedance of that setup?  That would be VERY cool and would really tie some interest into this thread.

This setup is unfortunately gone. I will see if I can get ahold of an imsg to redo this whole thing. I think this would show tons of information

 

[the_garynator]

52 minutes ago, Triticum Agricolam said:

You have that part a little backwards.  Impedance is at a low point (along with excursion) at the tuning frequency in a ported box.  With a sealed box impedance peaks at the sealed resonance frequency.  

When looking at impedance plots for sealed and ported boxes, sealed boxes have one impedance peak (at the resonant frequency) and ported boxes have two, one above and below tuning.  

I was only referencing rise in sealed boxes in relation to ported boxes regarding rise in general being lower.

As far as impedance being lowest at tuning frequency, all of my test results showed it being highest at those points. I seem to remember reading it somewhere too. I could be wrong and open to that possibility but will have to see some data or a irrefutable source to change my current standing.  Only thing I can think of is my data was based on peak frequencies of the whole system (enclosure, driver and vehicle) and while my port tuning was the same as the peak in the ported tests that I recall, it could have been slightly different due to whatever reason. And if you're saying that the high points could be relatively close to the low point, I can see that while my results seem to contradictory on the surface, they could actually support it if the margins are slightly adjusted within the margin of error.

[WalledSonic]

Dang, I'd love to get some 4th and 6th impedance plots.  I'm digging the input, but some cold, hard, raw data would be nice.  

[the_garynator]

2 hours ago, Triticum Agricolam said:

You have that part a little backwards.  Impedance is at a low point (along with excursion) at the tuning frequency in a ported box.  With a sealed box impedance peaks at the sealed resonance frequency.  

When looking at impedance plots for sealed and ported boxes, sealed boxes have one impedance peak (at the resonant frequency) and ported boxes have two, one above and below tuning.  

Just found an article that confirms that you are correct.

http://audiojudgement.com/speaker-impedance-curve-explained/

I'm thinking my results in the past that lead me to the incorrect conclusion were just skewed due to several factors.  Thanks for the correction.

[WalledSonic]

On 6/17/2017 at 9:48 AM, WalledSonic said:

That funny little peak around 36Hz?

Last weekend I pulled my subs and measured the Free Air Resonance (Fs) with the IM-SG.  The subs all came in at 35Hz.  A far cry from the 26Hz listed on PSI's website.  However, I did add the HP package which adds another spider, stiffening the suspension, and raising the Fs.

Is it possible that the 36Hz peak on my impedance plot is due to the speakers' Fs and due to the fact that I'm tuned at a much lower frequency (26Hz)?  Interesting.

[06RTCharger]

Partner sleepin on the job lol

[Triticum Agricolam]

I don't think that little spike around 36 hz is from your subs Fs.  The Fs changes once the sub is in a box.  I bet that spike is from resonance in your system.  Could be a standing wave frequency inside your vehicle.  

[rocking.that.eclipse]

On 9/7/2017 at 7:34 AM, WalledSonic said:

That funny little peak around 36Hz?

Last weekend I pulled my subs and measured the Free Air Resonance (Fs) with the IM-SG.  The subs all came in at 35Hz.  A far cry from the 26Hz listed on PSI's website.  However, I did add the HP package which adds another spider, stiffening the suspension, and raising the Fs.

Is it possible that the 36Hz peak on my impedance plot is due to the speakers' Fs and due to the fact that I'm tuned at a much lower frequency (26Hz)?  Interesting.

try clamping around the leads and see if there is a change from going through the bolt... 

 

Just an idea

 

[WalledSonic]

Triticum, i didnt consider that the mass of air in the port effectively adds mass to the cone and that the springiness of air in the box changes the effective suspension compliance.

However, Ive heard not to tune below Fs and i assumed it had something to do with suspension. Wasnt sure if the original suspension compliance fighting the box volume compliance could cause some impedance. Thanks for chiming in. Since i'm wiring down so low on this new setup, i'll just deal with my 36Hz peak.

Eclipse, i'll try that out for science. 

[WalledSonic]

4th Order Bandpass with (4) 8's for my buddy's JK Wrangler.  Wired down to 0.4ohmDC.  Almost 8 times rise at 63ish Hz, but only 3 times rise at 30Hz.  The amp will never see lower then 0.55ohm.  

You can see the tuning frequency is at 35Hz with the dip 'pulled' a bit to the left.  The subs would like to have the box tuning a little bit higher, but we're gonna break them in like this.  After break in, we'll re-evaluate the tuning and cut the port shorter if we dont like the low tuning (doubt it though).  In about a month or so I'll post an overlayed impedance curve to show the difference between fresh and broken in.  Will also post some free air resonance numbers.