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Old 31st October 2011, 10:33 PM   #21
JimM is offline JimM  United States
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I removed some of the stuffing from when the picture was taken. I started with 1/2 pound per cuft but ended up with some where around 1/4 pound per cu ft. (estimate)
I would recommend going to WalMart and buying poly pillow stuffing it's cheap and seems to work as well as acousta-stuff, at least untill you get an idea on stuffing quanity.
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Old 2nd November 2011, 11:53 PM   #22
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Ok Jim, I have ordered the timber. Just a thought and wonder if anyone has considered putting another driver on the back and running these as bi-polar ? I use to have bi-polars and the soundstage as absolutely staggering.
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Old 3rd November 2011, 12:37 AM   #23
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Quote:
Originally Posted by Barbieboy View Post
Just a thought and wonder if anyone has considered putting another driver on the back and running these as bi-polar ?
Fine as long as you double the cross-section and ports. Also a good idea to make it wider than deep (i figure a 3:1 is a good compromise)

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Old 3rd November 2011, 04:31 AM   #24
JimM is offline JimM  United States
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I have no idea what putting another driver on the back side would do to a mass loaded transmission line. If I were going to try this I think I would just do a bass reflex design with the two drivers. Interesting idea let us know the results if you try it. Planet10 may more insight to this type of design.
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Old 3rd November 2011, 12:20 PM   #25
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Wish I knew someone in the same town who has a couple of these drivers so we could experiment. Ok, will take a look at Planet 10 Jim
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Old 3rd November 2011, 12:27 PM   #26
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Originally Posted by planet10 View Post
Fine as long as you double the cross-section and ports. Also a good idea to make it wider than deep (i figure a 3:1 is a good compromise)

dave
Ok Dave, so basically means different cabinets. Have ordered the wood for these ones so will see how that goes for now.

I use to have a little known bi-polars - Musical Fidelity MC6s, about the same size as Jim's but with about six or eight drivers of which three were on the back. I was such a fool to ever get rid of them and have been craving that expansive sound ever since...
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Old 19th November 2011, 03:43 PM   #27
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Originally Posted by planet10 View Post
Fine as long as you double the cross-section and ports. Also a good idea to make it wider than deep (i figure a 3:1 is a good compromise)

dave
Hi Dave,

Come to the conclusion that doubling up the size of those cabs will be too big for my living room, plus at 300litres is huge. I have a drop down screen for the cinema so can't place them closer. But def want to go the bipolar / dipol route.

So last night set up a poorman's bipolar setup with whatever came to hand and bingo: glorious ! Wide open and still keeping focus.

How about me making four of the recommended seas cabinets for the FA22RCZs and just stacking them with the bottom one facing backwards ?!

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
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Old 19th November 2011, 11:19 PM   #28
JimM is offline JimM  United States
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You may won't to think about this 2 drivers wired in series, I would assume one in front one in back wired out of phase in a reflex enclosure rather than MLTL. The dimensions would be (outside dimensions) 45.5inX12inX15.5in HXWXD mount the front driver so the center is around ear height when seated (34in to 35in). Two ports of 3in diameter by 8in length will give you a F3 of 30.55Hz, but cone excursion may limit power input.
If you have a sub then a better alignment may be two 3in dia. by 4in long which will give you a F3 38.8 Hz may still run into excursion problems at around 50 watts but it will be at around 108 db (this is loud) so probably not a problem. You will probably still need a zobel at least on the front driver such as inductor with resistor in parallel. Look at application note for Fa22RCZ (google). Those are cool blue speakers did you build them?
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Old 20th November 2011, 12:04 AM   #29
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Thanks Jim,

The blue speakers are Blueroom minipods which I use on my desk, but I took off the skinny legs and replaced them with cones:

Blueroom Loudspeakers Minipod (Carnaby Blue) - Speakers & Speaker Systems - CNET Archive

With bipole is there a preferred position for the rear facing driver do you know ? Some say not to place them behind one another. Putting it down low would enforce the bass and up high would be good for the 'spacial' feeling perhaps ?
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Old 20th November 2011, 04:13 AM   #30
JimM is offline JimM  United States
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I have no idea I guess I would split the difference and put the back side driver lower than the front but above center line of the enclosure. If you made the back removable then you can flip the back from top to bottom and see which works the best.
Also I'm not sure if the two should be in phase or out of phase but that would be easy to change and see which works the best. The question is what happens when the two wave fronts sum within the listening area.
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