Pass Labs B4 crossover questions

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Zen Mod

Zen Mod

Official Court Jester
Joined 2003
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HF driver is practically the same on all Pepperpot thingies

though , impedance of VC can vary significantly , from series to series ...... never understood reason for that ....... someone at Tann factory had multiple personality disorder (same reason why I'm having string of green LEDs in every gadget of mine :rofl: )

anyway , you can count on fact that all Pepperpots are the same ...... except down low , where 12 vs. 15" waveguide is making difference , so Fc can be different
 
A

ascaso

Member
Joined 2007
ascaso said:
Do you think it is not appropriate to use your B4 active crossover in place of the passive crossover?
Click to expand...
@Mr. Nelson
I reread this sentence and I would not have explained myself badly.
If so, I apologize
What I wanted to say is:
if you believe that in my specific case with the tanny and since I have no way to take adequate measures it is better for me to use passive xover.

Thanks.
Lu
 
W

woofertester

Member
Joined 2011
luxwinter said:
I would like to do this for the MG15, but I am a newbie. Do I need an oscilloscope to do this?
Click to expand...

You could accomplish it with a sound card and a proper voltage divider. You might need a buffer and/or correction fudge factor(s) for errors in the measurement setup.

Measuring the AC impedance of something that changes with frequency requires some knowledge and careful attention to detail(s).
 
Nelson Pass

Nelson Pass

The one and only
Joined 2001
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In this case, you would be sweeping a low level input to your preamp
and measuring the voltage across the driver terminals. A sound card
and software like ARTA (free version) or other would do the job, but
some care must be taken to ensure that the ground at the load is
the same as the ground on the output of the soundcard. In cases
where there is uncertainty, a line-level type isolation transformer at the
input to the sound card is a good idea.
 
L

luxwinter

Member
Joined 2015
Nelson Pass said:
In this case, you would be sweeping a low level input to your preamp
and measuring the voltage across the driver terminals. A sound card
and software like ARTA (free version) or other would do the job
Click to expand...

That sounds do-able. Is this a situation where you measure the voltages with a voltmeter and do the plotting manually? Or is there some way to do it automatically (as is the case with frequency vs SPL measurements?)

Also, is there anything that runs on the Mac / OS X that will do the job?
 
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olen

olen

Member
Joined 2007
Paid Member
luxwinter said:
That sounds do-able. Is this a situation where you measure the voltages with a voltmeter and do the plotting manually? Or is there some way to do it automatically (as is the case with frequency vs SPL measurements?)

Also, is there anything that runs on the Mac / OS X that will do the job?
Click to expand...

I like FuzzMeasure, it’s $80 for a personal license. Just be aware that the predefined sweep stimulus starts at really low frequency (about 2Hz I think, and I don’t think you can change it, or maybe I just didn’t figure out how) so don’t turn it up too loud when running speaker measurements. Add a umm-6 usb measurement mic from parts express ($65) and you can actually perform decent acoustic measuments. I used a similar setup when setting up my home brew speakers with my B4.

FuzzMeasure - RODETEST
Dayton Audio UMM-6 USB Measurement Microphone
 
fabrice63

fabrice63

Member
Joined 2015
Nelson Pass said:
In this case, you would be sweeping a low level input to your preamp
and measuring the voltage across the driver terminals. A sound card
and software like ARTA (free version) or other would do the job, but
some care must be taken to ensure that the ground at the load is
the same as the ground on the output of the soundcard. In cases
where there is uncertainty, a line-level type isolation transformer at the
input to the sound card is a good idea.
Click to expand...

Here you'll find the measurements , made on Tannoy HPD385, HF an LF drivers , I hope they will be of any use ;)

drivers are in perfect shape and measurements were made in free air.

hpd385 test.doc - Fichier Doc

.
 
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N

nzlowie

Member
Joined 2015
Nelson, do you think the new active xover will have suitable adjustment to level out the dip in the mid range respose of the attached plot?
I currently use a shelf filter in minidsp to drop the FR below 4khz.

I'm sure your active xover will be a lot better than minidsp....

Many thanks, Dave
 

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