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Old 13th September 2011, 12:27 AM   #1
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Default Upside Down Pensil?

I love my micro-tower bipolars I just made with alpair-7's. I am thinking about using three super pensil 12's as LCRs behind my large home theater perforated screen.

They sit on a shelf in a large insulated wall space (4 feet deep by 6 feet high by 8 feet wide). The speakers overhang the front of the shelf which hopefully minimizes reflections from the shelf.

My question - the best way to get the driver at listener height is to put spikes on the top of the pensil 12 and use it upside down. Thoughts on problems this might cause? It puts the port or vent way above the floor, so I don't know if the design counts on interaction with the floor for bass reinforcement, though I will likely use a SW or two anyway. Also, I can see dangers perhaps with the driver just inches above shelf height.
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Old 13th September 2011, 12:42 AM   #2
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How close are the vents to the ceiling then?

I don't see an issue, you might get a bit less boundary loading on the terminus, But in an HT like that i suspect there are subs covering that range.

dave
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Old 13th September 2011, 04:24 PM   #3
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How deep is the shelf on which you're thinking of mounting the enclosures? Super Pensil is over 16" deep, so even if the shelf is more than that to support electronics, etc, you could still pull the enclosures forward enough to avoid diffraction issues that I surmise is your concern.
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Old 13th September 2011, 04:55 PM   #4
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There is plenty of depth. In fact, since it is hidden, aesthetics mean nothing and so the cabinets can actually overhang the end of the shelf, which should reduce diffraction. My sense is that any bad effects are dwarfed by the toll taken by the perforated screen on the sound.
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Old 13th September 2011, 04:58 PM   #5
chrisb is offline chrisb  Canada
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Originally Posted by pizzachef View Post
There is plenty of depth. In fact, since it is hidden, aesthetics mean nothing and so the cabinets can actually overhang the end of the shelf, which should reduce diffraction. My sense is that any bad effects are dwarfed by the toll taken by the perforated screen on the sound.

the latter is quite likely to be more of a concern, although some judicious EQ HF boost might take care of that?
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Old 13th September 2011, 05:30 PM   #6
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Yeah, I EQ it. Mostly it causes an attenuation about about 7500 and increasing in the 10,000+ range of a few db. Stewart sent me along with the screen a box to EQ boost the center channel but not being able to see any specs on it I have always been suspicious of it. Some EQ + Audissey gets rid of the problem, mostly
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Old 13th September 2011, 05:36 PM   #7
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I really don't know the science on this, but my perception is that horn loaded tweeters have less of a problem through the screen than domes. My current speakers are horn loaded, but I have never been happy with the crossover right in the middle of the dialog range, which is why I want to experiment with a full range driver.

The Bipole tower speakers went together so easy I thought I would try the pensils, even if they take a bit more EQ in the high end through the screen.

The only part about the build that was not much fun were the baffles. Tried both hole saws and router for the holes and they were still tedious to cut. Thinking that I can save time this time being less precise and just cutting holes with a jig saw. Can't imagine there is much problem if my baffle holes are a bit ragged.
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