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Multiple Small Subs - Geddes Approach
Multiple Small Subs - Geddes Approach
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Old 21st January 2020, 06:35 PM   #2171
beige is offline beige  Europe
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Hi Earl,

thanks for your comments!

I can provide single plots, no problem! I'm just about to do some more testing.
Yes, room is small, approx 70m3 with mostly 8" damping.

No filters are activated on the subs, I re-checked the settings again.
First two plots (one in the corner and other near mains) are from SUB2.

Please, see here, I measured each sub (I have 4 equal subs). I didn't place the mic close enough to the cone so probably room is affecting the measurements. Am I seeing this right - that 45 and 100 Hz are room modes?

Not sure what can I do to deal with 100 Hz issue. Elevate the subs?

Seems like you had similar situation here:
Multiple Subwoofer after Geddes

What did you do here at 100 Hz?
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File Type: jpg 4subs.jpg (78.0 KB, 79 views)
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Old 21st January 2020, 06:40 PM   #2172
gedlee is offline gedlee  United States
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The mic should be at the listeners position, not near field. The measurements have to contain the room. That's what we are trying to tame.

So those are the four subs? Where is the sharp 50 Hz. LP seen in the previous plots?

I'd say modes are at 30, 55 and 75 Hz, from what I see.
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Old 21st January 2020, 06:52 PM   #2173
beige is offline beige  Europe
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No, no. These 4 subs were measured just for testing purposes. To see if they all output the same signal. That's why I took nearfield measurements.

The 6 plots on previous page were taken with mic on listening position.
And here are plots for each sub - mic of course on seating position.

EDIT2: you are right, there was a HP filter. I didn't see it. Sub1 now has similar curve as Sub2. Thank you, Earl, I'm thankful you saw that. That's mileage, which I don't have.
Attached Images
File Type: jpg stereo.jpg (157.2 KB, 71 views)
File Type: jpg sub1.jpg (84.2 KB, 70 views)
File Type: jpg sub2.jpg (80.5 KB, 69 views)
File Type: jpg sub3.jpg (81.5 KB, 67 views)

Last edited by beige; 21st January 2020 at 07:03 PM.
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Old 21st January 2020, 11:13 PM   #2174
AllenB is online now AllenB  Australia
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Multiple Small Subs - Geddes Approach
If all plots are on the same graph you can better see what is EQ and what is a room mode.
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Old Yesterday, 08:45 PM   #2175
gedlee is offline gedlee  United States
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Beige

Personally I would want at least one of my subs to go above 100 Hz to better overlap the mains and help the mains issue at 100 Hz.

I am unclear how a sub cannot have much above 80 Hz as you show, is it a bandpass design? This is why I prefer just a simple closed box with a big driver. I can EQ this to be whatever I need it to be even up to 200 Hz + if I want. I gave up on bandpass and ported years ago.
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Old Yesterday, 09:24 PM   #2176
beige is offline beige  Europe
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To me it looks like the room is sucking up 45 and 100 Hz tones. Subs are closed design, declarated from 15-120 Hz (+/- 3dB)

Here's a test:
Velodyne DD-15+ Measurements & Analysis | Audioholics
(Mine are without +)

I have to try elevating the subs, perhaps it would make a difference.
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