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Re: [OM] First pass at dual sub integration--plot thickens

Subject: Re: [OM] First pass at dual sub integration--plot thickens
From: Wayne Shumaker <om3ti@xxxxxxxx>
Date: Thu, 24 Dec 2020 16:41:54 -0700
At 12/23/2020 05:37 PM, Mike wrote:

><<The passive sub response curve is light brown curve, #1, the UC-10 #2 green 
>and 
><<the best i could do in time alignment --#10 blue. 
>
><<http://zone-10.com/tope2/main.php?g2_itemId=23680
>
>Learning to navigate the REW (room Eq wizzard) software.
>
>The passive sub THD skyrockets and the powered sub THD never gets above 10%.  
>Apparently the distortion is not as easy to hear in these frequencies but the 
>stratospheric levels can't be good.
>
>I highlighted the THD curve and kept in the noise floor. 
>
>http://zone-10.com/tope2/main.php?g2_itemId=23683
>
>Tempted to put a brick  wall filter on that channel where the THD takes off.  
>There must be a better woofer that would work in that enclosure.  I don't know 
>enough about the Thiele-Small parameters for this ported design but it can't 
>be that hard to reverse engineer a new driver for it.  The one speaker guy I 
>contacted didn't want to touch it. 

Having designed many filters during my career - just a note: brick wall filters 
have large overshoot in the step response. The shaper the filter the more the 
overshoot. 

THD is the most common distortion usually caused by some clipping on the 
waveforms (it could be a soft clipping or other non-linearity). Hence, a 
non-linear response that attenuates the higher amplitude levels can cause it. 
You may find that the THD is dependent on signal levels. Non-linear transient 
affects will not necessarily show up in frequency responses. Also, the THD may 
be coming from a non-linear woofer element. Any filtering before the speaker 
won't change that. Testing at lower signal levels vs higher levels might be an 
interesting test. (this assumes I know what you are doing, which I don't 
fully...)

WayneS
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