Impedance phase

[diy speaker guy]

What options do I have to fix my impedance phase? It dips too low at the xo point.

[johnnyrichards]

What options do I have to fix my impedance phase? It dips too low at the xo point.

Stay away from tube amps and I bet you will be fine

[Pete Schumacher ®]

Stay away from tube amps and I bet you will be fine

+1

Look at the impedance phase around the woofer resonance. It's no big deal.

Modern amps with low output impedance won't have a problem with your XO, as long as the impedance doesn't dip too low.

[Jeff B.]

What options do I have to fix my impedance phase? It dips too low at the xo point.

What impedance and how much phase angle are we talking about?

[diy speaker guy]

At about 2khz it dips down to slightly below -60 degrees. Wolf's blog says keep it between +\- 30 if possible, and says some amps may have a problem with going further than -60.

(Thanks for the quick replies.)

[Pete Schumacher ®]

At about 2khz it dips down to slightly below -60 degrees. Wolf's blog says keep it between +\- 30 if possible, and says some amps may have a problem with going further than -60.

(Thanks for the quick replies.)

Lesser amps with marginal stability might have a problem.

But most won't, as long as the impedance doesn't dip too low.

[Jeff B.]

At about 2khz it dips down to slightly below -60 degrees. Wolf's blog says keep it between +\- 30 if possible, and says some amps may have a problem with going further than -60.

(Thanks for the quick replies.)

Yes, but what's the impedance when it hits -60 degrees? It's the combination that matters. If it is -60 degrees and 20 ohms, it probably won't make much difference. If it is -60 degrees and 4 ohms, it will be much harder to drive at that frequency.

[diy speaker guy]

How's that? Most of my amps are rated at 8 ohms and I would expect them to run these without shutting down or smoking. (I've used these amps to drive 4 ohm loads plenty, even car subs, as long as I keep the volume reasonable)

[diy speaker guy]

Ok, so assuming that chart is ok then all is good.

But if it's not ok, what are my options? Nothing I've tried so far in the tweeter circuit has changed this impedance phase issue, including changing the tweeter and nuking it's fs impedance. Reducing the L and/or C in the woofer circuit fixes everything right up, but the values I am using for L and C are important for my xo. Using a parellel resistor on the woofer works too but I think that's a fire hazard. Flattening the woofer impedance by other means will probably work but I'm not sure where resistors can be safely used in a woofer circuit. I assume the problem here is the massive impedance spike at about 1khz but I'm not sure how to safely tame that (without starting a fire).

[Zilch]

LRC series notch across the entire crossover at the peak frequency will pull the impedance down. Not sure what that'll do the the electrical phase above there, but it should not affect the frequency response....

[diy speaker guy]

Thanks for the response. I have 2 questions.

1. Based on the graph I posted, is this necessary?
2. How do you enter this into PCD? (As far as I can tell it has to be entered into the woofer low pass section or the tweeter high pass section, I don't see a section for applying a notch to the whole crossover.)

[diy speaker guy]

http://techtalk.parts-express.com/sh...d.php?t=220355

For a look at the design I'm talking about, check the link above.

[kendomusic]

Thanks for the response. I have 2 questions.

1. Based on the graph I posted, is this necessary?
2. How do you enter this into PCD? (As far as I can tell it has to be entered into the woofer low pass section or the tweeter high pass section, I don't see a section for applying a notch to the whole crossover.)

I believe if you scroll to the right of the PCD you will see the area where you can enter the LCR values for the whole circuit.

[Jeff B.]

How's that? Most of my amps are rated at 8 ohms and I would expect them to run these without shutting down or smoking. (I've used these amps to drive 4 ohm loads plenty, even car subs, as long as I keep the volume reasonable)

Your impedance is fine. Z is still relatively high when presented with this capacitive load.

[diy speaker guy]

Thanks everyone!