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Old 31st December 2016, 07:59 PM   #1
bk856er is offline bk856er  United States
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Default SEAS A26 build

Finally starting construction of the SEAS A26 speakers.

A while back I started a thread in the Pass Labs area, but it makes sense to move it here until the load is ready for an amp.

I've built a few other MDF flat-pack kits, but this will be my first kit from a full sheet of real wood. I'm using it as a tune-up for my skills and to get familiar with techniques and tools. I have a new track saw and a router with the necessary bits (no table saw and no elaborate shop).

All the components came from Madisound. I opted for Mundorf SGO caps and will stick with the SEAS circuit values initially. Material is good quality Baltic Birch @ ~18mm thickness and 13-ply. Interior will be lined with GR Research No-Rez.

I'll follow the SEAS cabinet plans for exterior dimensions and openings. Edges will be joined with rebates and then flush trimmed with a router after glue-up.

One area I'm not yet committed on is the interior bracing. I know I want some, but I'm not sure of the best approach. I'm tentatively planning to use the "World Designs" method implemented here. This approach was also published in 2006 for the floor-stander WD25T variant by Peter Comeau. Supporting the magnet structure seems like a good idea and is endorsed by SEAS, but the vertical brace behind the woofer strikes me as odd. Any opinions on this?

Some pics of yesterday's progress below. Any hints/tips/recommendations along the way would be appreciated!

BK
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File Type: jpg 1-IMG_3149.JPG (401.7 KB, 930 views)
File Type: jpg 2-IMG_3151.JPG (410.6 KB, 883 views)
File Type: jpg 3-IMG_3152.JPG (229.0 KB, 865 views)
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Old 31st December 2016, 08:14 PM   #2
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subscribed! I like a build that uses everyday tools and ingenuity... and that's is some very nice plywood, will surely look very nice when your done.
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Old 31st December 2016, 08:22 PM   #3
zman01 is offline zman01  Bangladesh
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Hi BK,

You might want to take a look at the "holey" bracing structure that P10 uses:

http://www.frugal-phile.com/boxlib/P...map-090810.pdf

A more elaborate one for a larger cabinet:

http://www.frugal-phile.com/boxlib/p...nsil12-map.pdf

Bracing the woofer is a good idea but be careful so that you don't make the brace too shallow as to stress the woofer frame when it is screwed on tight on the baffle. Probably better to keep a few mm gap and then use some material in the gap that compresses as the woofer magnet presses on to it. That way contact is still made with the brace and the energy is distributed.

Also read that vertical bracing is more effective in increasing cabinet rigidity. The vertical brace should be slightly offset from center as to divide the cabinets into unequal sections.

Please note that bracing sometime makes it difficult to install lining and the crossovers.
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Old 31st December 2016, 11:55 PM   #4
bk856er is offline bk856er  United States
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Great idea, Zia. I think with some creativity I can re-work the brace panel I already cut. If not, that's why I brought home three panels of ply when one was "enough" LOL.

Will be tricky to support the woofer magnet and keep the brace offset. Maybe I can add a "side-car" to the brace.

I've read of folks shimming with card stock to get a correct fit between the magnet and the brace. At my skill level, woodworking is a game of "mm's" and not "thousandths" like CNC.

BK
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File Type: jpg A26.JPG (32.2 KB, 794 views)
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Old 1st January 2017, 06:11 PM   #5
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Quote:
Originally Posted by zman01 View Post
Hi BK,
Bracing the woofer is a good idea but be careful so that you don't make the brace too shallow as to stress the woofer frame when it is screwed on tight on the baffle. Probably better to keep a few mm gap and then use some material in the gap that compresses as the woofer magnet presses on to it. That way contact is still made with the brace and the energy is distributed.

Also read that vertical bracing is more effective in increasing cabinet rigidity. The vertical brace should be slightly offset from center as to divide the cabinets into unequal sections.

Please note that bracing sometime makes it difficult to install lining and the crossovers.
This is what I did. Happy with the results. My build report including bracing plans is available here: https://www.vandomburg.net/audio/do-...ject-seas-a26/

To install lining and the crossover, I first left the top and bottom open. This gives ample room to work with.
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Old 1st January 2017, 07:14 PM   #6
bk856er is offline bk856er  United States
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roderickvd,

I have your excellent page linked in my initial post.

What Zia is suggesting is a vertical brace that runs front to back and buts up against the magnet, a la P10 as shown below on the left.

The WD brace format that you implemented is a vertical brace that runs left to right (and intersects with a horizontal brace). Lower section shown below from your site.

My reservation with the WD brace format is the proximity of the ~100mm (?) tall section immediately behind the woofer, on either side of the circular cut for the magnet bump. I don't know if this is a valid concern or not wrt to reflections and air movement.

BK
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File Type: jpg brace_2.JPG (21.7 KB, 117 views)
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Old 1st January 2017, 07:19 PM   #7
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Thanks for the compliments. These speakers have been my primary pair ever since I've built them, and so far zero problems with the screws in the front baffle.

I see no reason for concern, my thinking is that the spider frame is rigid and shouldn't move. It's more a question of building tolerances. It's really hard to glue the brace mm-perfect, so I suggest having a little leeway and filling it with foam.
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Old 6th January 2017, 05:11 PM   #8
zman01 is offline zman01  Bangladesh
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Hi BK,

How is the build coming along?
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Old 7th January 2017, 05:25 AM   #9
bk856er is offline bk856er  United States
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Quote:
Originally Posted by zman01 View Post
Hi BK,

How is the build coming along?
Strained my back a bit working on that 5x5' at ground level. Didn't come on until a day later - not as young as I used to be! Also decided I needed a good method of holding the work for routing. Ordered some gear to build a T-track clamping station out of a beater bench that some years ago was my eating table. With some luck and dry weather I'll be routing next weekend.

BK
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Old 7th January 2017, 05:49 AM   #10
zman01 is offline zman01  Bangladesh
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You take care and get well soon!
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