impeadence curves/ excursion

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nick mineau
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impeadence curves/ excursion

#1 Post by nick mineau » Fri May 07, 2021 2:13 pm

hi,
I when you have a bass reflex speaker, the lowest point between the 2 impendence peaks, is the tuning frequency of the cabinet, and also the point of minimum excursion.
On a bass horn, how would we determine the points of minimum / maximum excursion, or tuning ?

I attached a random impendence curve from a bass horn, maybe we could use this as a example to teach me? is the low peak, the low limit? and then there are 2 sort of resonance peaks above that ?
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impeadence.PNG

Bruce Weldy
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Re: impeadence curves/ excursion

#2 Post by Bruce Weldy » Fri May 07, 2021 2:30 pm

Not an expert (but I did stay in a Holiday Inn Express once... a long time ago) - Excursion is directly affected by power and frequency. The lower the impedance, the more power will be delivered. The lower the frequency, the more the cone will travel.....so, I'd say the point of the most excursion is going to be the lowest impedance near the lowest frequency.

In that graph, I'd say that the most excursion is going to occur at 50hz and from 30 down.... That's the layman's explanation. I'm sure those more knowledgeable will tell me the capacitor is on the wrong side of the inductor.

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Bill Fitzmaurice
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Re: impeadence curves/ excursion

#3 Post by Bill Fitzmaurice » Fri May 07, 2021 3:39 pm

You use a horn modeling software like HornResp to see excursion. The impedance peaks correspond with excursion peaks, but unlike a direct radiator there are many more of them.

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Re: impeadence curves/ excursion

#4 Post by Seth » Fri May 07, 2021 3:43 pm

nick mineau wrote:
Fri May 07, 2021 2:13 pm
On a bass horn, how would we determine the points of minimum / maximum excursion, or tuning ?
Modeling software will give a calculated value of those performance results/parameters. However, it's a little time consuming learning to use the software and also unraveling the dimensions of the horn path for a given existing design.

http://www.hornresp.net/
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nick mineau
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Re: impeadence curves/ excursion

#5 Post by nick mineau » Wed May 12, 2021 7:30 am

So, ill have to learn to play with that molder, but for sake of argument, would this horn have more excursion at 42hz, then it does at 80ish hz?
and what about comparing 35hz to 42hz? 35hz is a impendence low point sort of, so would it have less excursion then the peak at 42?

I'm guessing the answer is to model it lol

nick mineau
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Re: impeadence curves/ excursion

#6 Post by nick mineau » Wed May 12, 2021 7:31 am

sorry for the spelling errors

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Bill Fitzmaurice
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Re: impeadence curves/ excursion

#7 Post by Bill Fitzmaurice » Wed May 12, 2021 9:42 am

I can't say, that impedance curve is out of the ordinary and suggests that it's not a pure horn. This is a T60 impedance chart:
Image

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Re: impeadence curves/ excursion

#8 Post by Seth » Wed May 12, 2021 11:03 am

Bill Fitzmaurice wrote:
Wed May 12, 2021 9:42 am
I can't say, that impedance curve is out of the ordinary and suggests that it's not a pure horn. This is a T60 impedance chart:
Image
Would you mind also posting the displacement plot? I think the two together may help in his curiosity of the relationship (if there is any) between impedance and excursion.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bill Fitzmaurice
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Re: impeadence curves/ excursion

#9 Post by Bill Fitzmaurice » Wed May 12, 2021 11:49 am

Image

nick mineau
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Re: impeadence curves/ excursion

#10 Post by nick mineau » Mon May 24, 2021 12:48 pm

wow, these 2 charts used with each other is very informative. Thank you all very much for the intel.

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