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Old 10th June 2012, 07:46 PM   #1
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Default Eeek! Pensil 10.2 Response Dips

I finally was able to put a spectrum analyzer on my 3 Pensil 10.2 L-C-R speakers I built a while back. At one or two meters one of the three speakers is quite flat, but the other two have a pair of 15 DB dips at around 160 and 200 HZ, causing this whole 50HZ region to sag.

Could this be a stuffing / tuning issue? Any ideas?
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Old 10th June 2012, 07:52 PM   #2
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Were all three speaker systems in exactly the same location when you took the measurements?
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Old 10th June 2012, 08:04 PM   #3
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By the way, I think I tried the obvious things. Swapped drivers and the good and bad boxes stayed the same, so not a driver issue. Same placement, amp, etc for measurement so it almost has to be a box issue. One has the two dips as described and one has a single large dip from about 160 to 225 hz, or 10-15 db magnitude. The third, as I said, is marvelously flat, within a few db, through this whole range.
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Old 10th June 2012, 08:09 PM   #4
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Sounds like room issues to me.

Edit, later post saying same placement for measures rules out room.

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Old 10th June 2012, 08:24 PM   #5
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There must be a difference in the enclosures. It would have to be a big difference to have such an effect on the response.
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Old 10th June 2012, 09:04 PM   #6
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yup, there may be something going on in the box also, but room is probably the main problem.
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Old 10th June 2012, 09:44 PM   #7
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Ir sure looks like floor/ceiling bounce to me.

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Old 10th June 2012, 10:17 PM   #8
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Agreed, but if the cabinets have been measured in the same location, & the drivers have been interchanged to confirm it's not an issue with those (unlikely from what I gather about MA production tolerances), then I can only conclude there must be a box construction issue. Best guess is that either there's a problem with the damping, or there's a leak / leaks.
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Old 10th June 2012, 11:00 PM   #9
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Some impedance curves might be useful here.

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