Pensil 7 (Alpair 7) - Page 3 - diyAudio
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Old 27th April 2010, 01:05 AM   #21
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2nd Measurement. For reference the enclosure's front panel, which of course is secured on all edges.

The energy here is a little lower in frequency.
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File Type: jpg Pencil 7 Undamped Side Front Panel.jpg (180.9 KB, 1561 views)
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Old 27th April 2010, 01:10 AM   #22
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3rd Measurement. The same side panel as in the first, but at a later date with a bituminous damping applied. I have used an aqueous waterproofing material, it goes on as a thick spreadable goo. I applied it very liberally to the side, stapled a 5mm waste cotton felt to it, and then saturated the topside of that as well. It takes a few days to dry, and remains a little flexible.

The blue trace is a previous dataset of the undamped panel, the yellow after damping. Obviously more effective at higher frequencies. I had hoped it might have reduce the energy around 200-500Hz as well.

The bottom trace is the ambient noise prior to measurement for interest.
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File Type: jpg Pencil 7 damped Side Panel.jpg (190.6 KB, 1507 views)
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Old 27th April 2010, 01:14 AM   #23
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4th Measurement. The damped side panel with the rear panel screwed in place. This is indicative of what might happen if additional bracing was added.

There is a large reduction in the 200Hz energy, but also a little more at 500Hz. Above that it is improved again a little over the damped panel alone.
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File Type: jpg Pencil 7 damped Side with rear.jpg (192.5 KB, 1449 views)
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Old 5th May 2010, 04:51 AM   #24
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Ok, at last. All assembled and hooked up. Running it at very low level...
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Old 7th May 2010, 07:19 AM   #25
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Haven't yet quite reached 20hrs, but quiet replay of piano piece is indicating substantial promise....
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Old 19th May 2010, 10:45 PM   #26
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OK, got a few more hours on these now. I have to say I'm impressed. Congrats to Mark for the drivers, and Scottmoose for the cabinet. Good lf extension for a small driver.

I have a difficult room, and have yet to optimise placement, but even now there are indications these will throw a big and believable image when placed right.

They hold up well against the Quad ESL57s.
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Old 19th May 2010, 10:57 PM   #27
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I'm always interested in how much drive loudspeakers need, and I have collected data from a range of system, and circumstances.

Here is the Pensil 7 running at about 84dB peaks in my room. Subjectively this is a comfortable listening level for the material involved... Grey De Lisle - The Graceful Ghost - Walking in a line.

The image shows accumulated voltage at the speaker terminals over the length of the track.
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File Type: jpg Pensil 7 Voltage 84dB.jpg (270.7 KB, 1259 views)
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Old 19th May 2010, 10:59 PM   #28
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And here is the same track but this time looking at the loudspeaker current demand. Although the display is 500mV per division it should be read as 500mA per division.
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File Type: jpg Pensil 7 Current 84dB.jpg (254.7 KB, 1142 views)
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Old 19th May 2010, 11:18 PM   #29
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Lastly here is the artist mentioned...

Grey De Lisle

and a bonus... a nice track where she is mostly an observer...

Murray Hammond
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Old 24th May 2010, 09:25 AM   #30
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One further update here... finally went to work on my room. Used CARA to model and suggest optimum placement. These loudspeakers are now really shining!!

Of interest too is that the rear located port is absolutely working as required.
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