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Old 4th April 2011, 04:45 AM   #861
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Quote:
Originally Posted by tb46 View Post
Hi 4pyros,

I'm with djk, but a 1000 Ohm resistor is large enough. Then you can use the precision 10 Ohm resistor in place of the speaker for an initial calibration. If any of this is unclear, get a WT3 :-).

Regards,
I actually prefer using a much smaller high-power resistor (e.g. 4 ohms) and using the method I suggested. It's a longer approach, but it also allows me to generate much higher voltages across the speaker and therefore track how t/s params might shift under higher drive levels.
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Old 4th April 2011, 04:48 AM   #862
Djim is offline Djim  Netherlands
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Djk and Oliver, the first method I presented was based on

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Old 4th April 2011, 04:54 AM   #863
Djim is offline Djim  Netherlands
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Yes you are right Brian, for accurate measurements your should change the 10 Ohm resistor in at least half the Re of the loudspeaker. You also need to measure the resistance of the cables.

Last edited by Djim; 4th April 2011 at 04:57 AM.
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Old 4th April 2011, 05:07 AM   #864
djk is offline djk
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"I'm with djk, but a 1000 Ohm resistor is large enough."

No, it's not.

Some low Qes drivers can have impedance peaks in excess of 200Ω. A 1000Ω resistor in series with that kind of driver is hardly constant current, and will result in inaccurate parameters.

I generally use a Crest amplifier that will drive 92V RMS.
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Last edited by djk; 4th April 2011 at 05:09 AM.
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Old 4th April 2011, 01:31 PM   #865
tb46 is offline tb46  United States
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Post #864

Hi djk,

It's probably mostly irrelevant to the discussion of the SS15, but 1000 Ohm is quite a normal value for this measurement. I have never heared of anybody that applies 92Vac to the constant current circuit for measuring loudspeaker impedance, but that just proves, that I have to get out more. :-)

Regards.
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Old 4th April 2011, 08:36 PM   #866
djk is offline djk
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I realize that that is the value that most people use, and I explained why it is an incorrect choice.

BTW, my HP 200 generator (tubes) can put out 40V into 600Ω.
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Old 4th April 2011, 08:56 PM   #867
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back to ss15 projects

here i just started today, didn't order the 3015 yet, will do that this week. going to dinner now will continue construction later on tonight!

good ol made in USA ply
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got everything cut, started tracing out on the side piece. i also added some angled cuts to the pieces that don't meet at 90 deg to make it go together a little better.
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should i add corner reflectors in every corner? i don't mind the small amount of extra added weight if they'll help and i have the wood sitting here....
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Old 4th April 2011, 10:47 PM   #868
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Quote:
Originally Posted by m R g S r View Post
I have a Mac so I can't as far as I know unless hornsresp works on a Mac now ? (not running windows on a Mac)

And woopss I meant 4pi Aka Into free space (that's how I'll be using my ss15)
Hi, FYI hornresp works fine on Intel Macs under "WineBottler" (windows emulator)
Give it a search, just my 2 pence.

Al
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Old 4th April 2011, 11:40 PM   #869
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should i add corner reflectors in every corner? i don't mind the small amount of extra added weight if they'll help and i have the wood sitting here....
I only used corner reflectors to rid the box of parallel sides in the wave path. Look at pic in post #827. I only needed 3 at 15 degrees each. Andy
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Old 5th April 2011, 01:38 AM   #870
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Here are the unofficial results. I wish it was better down lower but I got a good peak at 180Hz. I am calling it good to make more. Any other thoughts? Andy
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