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

[Swifty]

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:



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:

[DYNABLASTERTUNERS]

nice enclosure

I have a question, does it need time allignment with the DSP for the bass?

[Swifty]

Originally Posted by DYNABLASTERTUNERS

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.

[DYNABLASTERTUNERS]

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 (((

[Swifty]

Originally Posted by DYNABLASTERTUNERS

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.

[Swifty]

Progress!

[kristleifur]

LOOKS GOOD !

Keep going - thanks for the pic

[Swifty]

Progress! Yesterday I finished veneering the first cabinet, and managed to put in all the holes. next up: sanding and adding dampening.

[Andy17]

Originally Posted by Swifty

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.

[Swifty]

Trial fit: