FAST build with Alpair 7.3 and Seas L26ROY and Hypex AS2.100 - diyAudio
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Old 14th March 2012, 09:27 PM   #1
Swifty is offline Swifty  Netherlands
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Default FAST build with Alpair 7.3 and Seas L26ROY and Hypex AS2.100

About 5 months ago I started thinking about doing a FAST build with the then just released Alpair 7.3. I had just finished a Pencil 10.2 build, and was surprised by the wonderful quality of the Markaudio full range driver. However wonderful the Pencils are, I still was looking for cleaner, better defined bass. There is plenty of bass in the Pencil design, it just lacks a bit of definition and texture.

To keep the cabinet slim and acceptable to everybody in this household, the bass driver will be mounted in on the side of the cabinet. To get this to work I need to cross below the point where the bass driver will start to radiate in 2 pi space. On my cabinet which is 37cm deep this means I have an upper limit of about 250 hz with a steep slope.

All this means that active filtering will be a big advantage. Enter the Hypex AS2.100: A plate amp with two 100 watt ucd amps including a DSP. Perfecto!

I decided on the Seas L26ROY based on its stiff cone, low distortion and high excursion capability. The plan is to get them to 25 hz or so @ -6db in a 30l cabinet. This will require a LT via the DSP.

First things first, buiding a prototype:

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Early measurements and listening sessions gave me enough confidence to go ahead and start building in earnest.

I am using the "Translam" method, mainly due to my limited access to nice tools like a table saw (or even a shed for that matter) All I have is a router, jigsaw and a workmate.

The sides will be made from 24mm baltic birch ply and will function as the L26ROY's baffle. The middle 8 slices are water proof MDF. Bracing is extensive. to get the resonating frequency above 200hz as much as possible. (200 hz will be the crossover point between the two drivers)

The Alpair 7.3 will be housed in a separate chamber, designed to minimiste standing waves. This chamber will be made heavy and thick by adding car audio deadening mats to keep it's resonating frequency below 200 hz as much as possible. Here are a few pics of the progress so far, one cabinet is ready for finishing. All holes will be routered after veneering:

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Old 15th March 2012, 08:06 AM   #2
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nice enclosure

I have a question, does it need time allignment with the DSP for the bass?
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Old 15th March 2012, 11:21 AM   #3
Swifty is offline Swifty  Netherlands
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Originally Posted by DYNABLASTERTUNERS View Post
nice enclosure

I have a question, does it need time allignment with the DSP for the bass?
Yes it will. I will have to put a delay on the Alpair.
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Old 15th March 2012, 11:52 AM   #4
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can you tell me why then Boenicke in his SLS doesn't time allign the side firing fullrange? maybe the tweeters are wired out of phase to the fullrange?!
Boenicke Audiomanufacture SLS ))) Raindrop Audio (((
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Old 15th March 2012, 12:25 PM   #5
Swifty is offline Swifty  Netherlands
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Originally Posted by DYNABLASTERTUNERS View Post
can you tell me why then Boenicke in his SLS doesn't time allign the side firing fullrange? maybe the tweeters are wired out of phase to the fullrange?!
Boenicke Audiomanufacture SLS ))) Raindrop Audio (((
You'll have to ask him :-)

I am not in the measuring phase yet. I will have to see if and how much time alignment is needed. the acoustic centre of the Seas is 14 cm behind the Alpair so theory predicts the need of some time alignment.
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Old 23rd March 2012, 10:18 PM   #6
Swifty is offline Swifty  Netherlands
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Progress!

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Old 24th March 2012, 09:34 AM   #7
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LOOKS GOOD !

Keep going - thanks for the pic
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Old 26th March 2012, 09:37 AM   #8
Swifty is offline Swifty  Netherlands
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Progress! Yesterday I finished veneering the first cabinet, and managed to put in all the holes. next up: sanding and adding dampening.
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Old 26th March 2012, 10:44 AM   #9
Andy17 is offline Andy17  Germany
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Originally Posted by Swifty View Post
You'll have to ask him :-)

I am not in the measuring phase yet. I will have to see if and how much time alignment is needed. the acoustic centre of the Seas is 14 cm behind the Alpair so theory predicts the need of some time alignment.
It depends on your crossover (cut off) frequency. At 100Hz the wavelenght ist >3m and the effect of the room and speaker position (in the room) is greater then the bit of phase displacement.
With 14cm "in simulation" the first little effect can be seen >500Hz.
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Old 27th March 2012, 09:54 AM   #10
Swifty is offline Swifty  Netherlands
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Trial fit:

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