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bobsinclar 16th November 2006 11:38 AM

Impedance curve measurement
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Hi all,
I am trying to set correctly a loudspeaker system with this combo: JBL 2426H +altec 511B (HF) and JBL 2234H 15inch woofer
the first problems I had where coming from the 2426h and 511horn combo, resonnating quite audibly 400Hz , 800Hz and 1.6Khz.... this was well solved using Wayne padham damping resistor method ...
For info I use bi amp and the active crossover is a DBX drpa driverack,
it allowed me to choose the Fc quite easily, that I set at 650hz...
and to damp a bit and equalize the horn I used a resistordivider 15Ohm parallel/25Ohm series and a bypass cap (0.47mf)
this giving an attenuation of about 10db with a 6db/octave rise after 3kHz

Sound is quite good, But now I'd like to really confirm that by easy measurements, and here comes my question, considering that I am not a "computer guy" would anyone know an easy way to measure impedance curve from the horn with simple equipment, like a voltmeter and of course Low frequency generator? like setting diffrent frequencies and taking it point to point to draw the curve...
I know there are softs for that but Really would take me a year to get how they work:D
any advice would be cool

pinkmouse 16th November 2006 11:52 AM

Hi Vince, I love the speaker stands! :)

I think, rather than talking about measuring impedance, you mean frequency response. You can do this with a tone generator and a SPL meter as you said above. If you do mean impedance, then have a look at Rod Elliot's site for a manual method. However, I would encourage you to use the existing software packages that do the measurements for you. They may be slightly more expensive, and have a steeper learning curve, but once you are up and running then you will have a much faster, more powerful and flexible suite of tools to work with.

bobsinclar 16th November 2006 11:59 AM

Thank you very much Pinkmouse!
sure the cabinets stands are audiophile approved:D

As your advise I'll look at Rod Elliots' method , thanks for the link!
yes I was meaning impedance curve...
I already took the response curve but the impedance could help me confirm everything is ok...
I will also try to follow your advises concerning softwares, but I really take time to get into it!

bobsinclar 16th November 2006 12:08 PM

Hey Pinkmouse, I can't manage to find the section in Rod site concerning impedance, any help ?

pinkmouse 16th November 2006 12:10 PM


bobsinclar 16th November 2006 12:17 PM

You are the one Pinkmouse!
Many thanks;)

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