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Re: 4 pi speakers + 3 pi subwoofers, pics & measurements [message #81364 is a reply to message #81363]

Thu, 28 May 2015 14:36

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

I think we can rule out the microphones, because two different ones show the same trend. And I think we can rule out the waveguide, both because its properties are known and also because measurements show it hasn't modified response. We would expect no response change from a waveguide or CD horn. But that still leaves the compression drivers and the measurement system.

The DE250/H290C driver/waveguide combination has less rolloff up high than what I would expect, which is why the crossover has no capacitor in position C1. Traditionally, one would expect to have compensation for mass-rolloff in the form of a first-order high-pass filter in the crossover's tweeter circuit. But not all drivers are like that.

Mass-rolloff is expected, and it's really more unusual to not have it on a CD horn or waveguide. So the DE250/H290C combination is unusual.

Which leads me to this question: Is the driver you're testing a DE250? If not, you might consider installing a capacitor in position C1 to provide mass-rolloff compensation. The response curve shown looks like it could use it. So if the driver isn't a DE250, this may be all that needs to be done.

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[Message index]

		4 pi speakers + 3 pi subwoofers, pics & measurements By: vandevoordekoen on Tue, 26 May 2015 13:29
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: Wayne Parham on Tue, 26 May 2015 13:39
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: vandevoordekoen on Wed, 27 May 2015 08:05
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: Wayne Parham on Wed, 27 May 2015 11:04
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: vandevoordekoen on Wed, 27 May 2015 16:23
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: Wayne Parham on Thu, 28 May 2015 11:19
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: chrisR on Thu, 28 May 2015 11:32
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: vandevoordekoen on Thu, 28 May 2015 12:59
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: Wayne Parham on Thu, 28 May 2015 14:36
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: vandevoordekoen on Sat, 30 May 2015 11:28
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: Wayne Parham on Sun, 31 May 2015 09:48
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: tom-m on Wed, 03 June 2015 18:12
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: Wayne Parham on Thu, 04 June 2015 10:19
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: vandevoordekoen on Thu, 04 June 2015 10:53
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: Wayne Parham on Fri, 05 June 2015 17:37
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: vandevoordekoen on Tue, 26 May 2015 13:47
		Re: 4 pi speakers + 3 pi subwoofers, pics & measurements By: tom-m on Fri, 05 June 2015 22:09

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