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2 manifolds?

The highpass makes a huge difference. For the BHD scene, setting it to ~16hz slashes the excursion in half. You lose the 8hz fundamental but you can go for the 12hz+ instead.
 

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Discussion Starter #22
Two manifolds?

Maybe one front and one rear a la the Harman white paper. That would probabaly also smooth out the curve. Of course it wouldn't do much for coupling the drivers... then again I wouldn't have to cut as much. Hmm. This just keeps getting more and more expensive :duh:.
 

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Discussion Starter #23
Here's the latest curve that shows what's going on. I know it doesn't conform to forum standards.

 

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Discussion Starter #24 (Edited)
Here's the final plot without resistors.



This one doesn't have the target level raised like the previous one, but you can easily see how adding the resistors affected output above and below Fs (16 Hz). Since the first plot has the target level raised 6dB, the gain on the amp is turned down 6dB to keep the real volume on the sub the same. Therefor, when comparing the first plot to the second, you have to decrease the EQed response in the first plot 6dB. That really shows off how much the infrasonics are reduced. Please also notice that the peaks in the 55-115 range are not nearly as high in the first plot. That of course decreases the amount of cut necessary in the region.
 

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I'm a bit confused by your plots. Is the blue plot without the resistor and the purple plot with? I assume the dashed lines are the target response with filters? From the looks of things the low end stayed essentially the same but the high end changed... Did you change the volume between the measurements? At any rate thanks for taking the time to show us all the results. This thread has been very educational.
 

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From the looks of things the low end stayed essentially the same
Look at the second plot and observe the flatness from 7Hz-15hz. Now look at the first plot for that same range. Quite a change in Q of the entire plot. Unfortunaltely as Jagman would probably attest to, with regard to this tactic, he won the battle, but lost the war.

brucek
 

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Discussion Starter #27
Look at the second plot and observe the flatness from 7Hz-15hz. Now look at the first plot for that same range. Quite a change in Q of the entire plot. Unfortunaltely as Jagman would probably attest to, with regard to this tactic, he won the battle, but lost the war.

brucek
Bruce nailed it.

I think it was a relatively cheap experiment ($40) that was worth trying. Especially since I had issues in the lower and upper bass regions and the resistor addressed both. It also had the potential to help others who had similar concerns. The problem is the decrease in SQ associated with the resistor. It's easy to say distortion would increase with the addition of a resistor, but you just don't know how it sounds until you try. I've become too acclimated to low distortion bass and the trade off is just too much.
 
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For those who are going to attend RMAF 2008, I have built a device to compare the damping force of nonservo and servo side-by-side The device will be displayed at room 2016 of Marriott. It will address this debate of damping factor issue from a slightly different angle. A nonservo driver and a servo driver are placed on a plateform to allow attendees to push the center of the cone to feel how the cones react differently. Then one can also observe how the damping force diminishes when the cone is pushed in and in contrast, the servo maintains a pretty constant damping force at the same position. The main reason is our sensing coil is a super overhung design and it stays in the gap even when the driver coil is practically out of gap. The sensing coil has a complete control of the cone regardless cone position.
 

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Discussion Starter #30
Something to keep in mind... his servo subs are designed to have the resistor effect. Mine wasn't, so the resistor was a quick fix experiment. It would be very interesting to hear the difference between my quick fix and his fully designed system.
 
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