WAW / FAST build with Alpair 7.3 and Seas L26ROY and Hypex AS2.100

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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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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.
 
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.
 
Placing the woofer on the side has the obvious advantage of being able to use a large woofer without compromising on baffle width and therefore imaging. Right now I am making nice progress of dialling these in. The crossover is done via the DSP of the AS2.100 units. I am crossing over at 250 hz, LR4. I added a 5 db low shelf with a centre frequency of 595 hz. The woofer has a LT with a pole Q of 0.5 and a pole freq. of 27 hz.

While I will likely slightly modify things here and there, this already sounds amazing.
 
These are almost finished now. I am very happy with the results! Combining the Alpair with a woofer really pays dividends in imaging, clarity and composure of the total system. Not to mention the effortless dynamics. Here are a couple of pictures of the finished cabinets:

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I am crossing over at 250 hz, LR4. I added a 5 db low shelf with a centre frequency of 595 hz.

You could probably eliminate the shelf by level adjustment between the drivers??

Did you ever measure these? I helped a guy on another forum with his A7 FAST. He measured the A7 with an LR4 at 300hz high pass. I didn't do the measurement, but I processed it. The gate is 2.7ms because he measured to close to the floor, so the high pass isn't well defined in the measurements. He got this:

An externally hosted image should be here but it was not working when we last tested it.


That was in the cab. I'm surprised by the baffle step region. He may have done something wrong there. But it leaves me thinking your 5db shelf might be aggressive.

These must make great bass :D Are you using the minidsp?
 
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