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Old 20th July 2012, 06:59 PM   #1
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Default 10.2 enclosure for center speaker doubling as bookshelf

Hello all,

I have finally decided to start building my new home theater system. The main speakers will be 10.2 pensils, and I want to use the alpair 10.2 for the center speaker too. The idea is that I want the center to match the bookshelves that are already hanging over the tv, or rather be a very thick bookshelf with an inbuilt alpair 10.2 . It should then look something like the attached picture (quick sketch, not to scale and probably not even close to the correct proportions).
To match the other bookshelves two of the outer dimensions are fixed: width has to be 1100 mm and depth 220 mm. The height should be as small as possible, maybe something like 200 mm. With 18 mm wallthickness the volume would add up to 32.1 liters.

Ok, and thats as far as I get on my own.

The question I have now: Is 32 liters ok for a closed box? Or, to match the pensils, should I go for a ported design? I want it to be symmetric, so there would be two ports, one on either side (like in the picture). How would they need to look like?
You see, I am utterly clueless and need help
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Old 20th July 2012, 08:19 PM   #2
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Hilmar_G View Post
Hello all,

I have finally decided to start building my new home theater system. The main speakers will be 10.2 pensils, and I want to use the alpair 10.2 for the center speaker too. The idea is that I want the center to match the bookshelves that are already hanging over the tv, or rather be a very thick bookshelf with an inbuilt alpair 10.2 . It should then look something like the attached picture (quick sketch, not to scale and probably not even close to the correct proportions).
To match the other bookshelves two of the outer dimensions are fixed: width has to be 1100 mm and depth 220 mm. The height should be as small as possible, maybe something like 200 mm. With 18 mm wallthickness the volume would add up to 32.1 liters.

Ok, and thats as far as I get on my own.

The question I have now: Is 32 liters ok for a closed box? Or, to match the pensils, should I go for a ported design? I want it to be symmetric, so there would be two ports, one on either side (like in the picture). How would they need to look like?
You see, I am utterly clueless and need help
There's no reason that a horizontally oriented MLTL couldn't work for your situation, since the floor boundary loading generally designed into something like a Pensil wouldn't be required for the frequencies pass banded to the center channel.

However, as an MLTL, the Pensil is predicated on Quarter Wave action in the long dimensional axis, a critical driver location along that length (that wouldn't be in the center), and a single terminus.

There are however, dual vented enclosure designs for the entire Alpair series*, and while I'm sure the net required volume for the 10.2 would be less than 32liters, it could certainly be compartmentalized into a larger cabinet.

* the Alpair 10.2 design may have even be posted here already
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Old 4th August 2012, 10:00 PM   #3
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I think my only options would be closed or bassreflex.

Quote:
Originally Posted by chrisb View Post
* the Alpair 10.2 design may have even be posted here already
Can you point me in the right direction here? I have only found this for a ported design.

I have started to do some research on speaker design, and from what I have learned so far it seems the Alpair 10.2 is better suited to bassreflex than a closed box. Is that correct?
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Old 5th August 2012, 02:12 AM   #4
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I have a centre channel based on the Mar-Ken10.2. It is 13 litre. A BR box for the 10.2 can be stetched out to as much as 20 litre, but for a centre i'd stay with the small side. The box could be fitted into the centre, with open shelf either side to get the length required.

dave
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Old 5th August 2012, 08:40 PM   #5
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Ok, this is slowly taking shape in my mind. Right now I am thinking about 16 liters bassreflex, minus chassis and bracing. My research has brought me to the point where I can now calculate the dimensions of a standard bass reflex tube (aren't you proud? ). Now, since I want two to keep a symmetrical look, do I just half the area of the calculated tube? Or is it a bit more complicated...
And is there an advantage of an actual tube over a vent like the MarKen has? Whats the difference?
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Old 5th August 2012, 09:45 PM   #6
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I would do slot vents, yes just divide area in half, keep the length the same.

dave
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Old 5th August 2012, 09:50 PM   #7
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Here is one i designed fro A12 for Skeeter:

Click the image to open in full size.

dave
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Old 7th August 2012, 01:12 PM   #8
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I found the original thread and some pictures of the interior. Very interesting how the vents are done. I am learning something every day. Does the short length of the vent after the bend towards the front count as tubelength? Or is a mm more or less not that important anyway?

And thanks for educating me. Its (obviously) the first time I am not building an already proven design. Very exciting and also a bit scary
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Old 8th August 2012, 12:17 AM   #9
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If the distance is substantially greater than the vent width it doesn't count, if it is the same of only slightly more it does count.

dave
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