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Old 26th August 2012, 08:40 AM   #21
Bon is offline Bon  Australia
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Quote:
Originally Posted by Moondog55 View Post
Makes the use of "T-Nuts" look a little wimpy.
I have to ask; what the heck are you going to be using as the sub-woofer for those boxes??
Sub-woofers? We don't need no stinkin' subwoofers.
The Peerless 830452 are used below 150 Hz. I can equalise them flat down to 25 Hz in my room with good power handling. My room is has solid brick wall and is well sealed, so maintains good bass. I'm as far from SET as it is possible to be.
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Old 26th August 2012, 09:43 AM   #22
Bon is offline Bon  Australia
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Default Bracing

The internal bracing is pretty much standard. I preferred 25 mm plywood for internal braces with 5 mm rebate locating grooves routed into the front and rear internal baffle. I discovered a superior bracing technique which I would have used more had I known how effective it was. The sides, front and rear are locked together by shelf braces. I wanted an effective way of bracing the base and top. I came up with the scheme shown in the photos. Subjective knuckle raps suggest these are the stiffest panels. In hindsight I would like to have used a similar bracing on all the panels.
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Old 26th August 2012, 11:45 AM   #23
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Quote:
Originally Posted by Bon View Post
Sub-woofers? We don't need no stinkin' subwoofers.
The Peerless 830452 are used below 150 Hz. I can equalise them flat down to 25 Hz in my room with good power handling. My room is has solid brick wall and is well sealed, so maintains good bass. I'm as far from SET as it is possible to be.
I think my tongue may have been firmly in my cheek when I asked that.
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Old 26th August 2012, 05:21 PM   #24
Paul W is offline Paul W  United States
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Great work!

Post 9, seems to show a straight-sided "pipe" on the mid...so maybe consider relieving the sides into more of a cone shape to reduce restriction and resonance.
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Old 26th August 2012, 09:14 PM   #25
Bon is offline Bon  Australia
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Post 9, seems to show a straight-sided "pipe" on the mid...so maybe consider relieving the sides into more of a cone shape to reduce restriction and resonance.
Yeah, that's a point I have considered. It arises from the plastic bucket used to mold the the resin. Because the baffle tapers towards the bottom, the depth of the hole is 90 mm on the high side and 40 mm on the low side, so hopefully will not support a strong resonance. I will evaluate the effects when I mount the drivers soon. I did file off the sharp edge of the hole but it is hard on tools. Resin does not like to be ground at high speed. It smokes and stinks. If I can arrive at an effective low speed technique I will certainly have a go. It does not have to look pretty inside the box.
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Old 26th August 2012, 09:40 PM   #26
mightym is offline mightym  United States
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Fascinating build.

As to the mid baffle, and bearing in mind the excellence of hindsight in general,....why didn't you put the buckets into the baffle from the rear when you were pouring the resin?

Keep on posting your build please!

John
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Old 26th August 2012, 10:09 PM   #27
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Quote:
Originally Posted by Bon View Post
Yeah, that's a point I have considered. It arises from the plastic bucket used to mold the the resin. Because the baffle tapers towards the bottom, the depth of the hole is 90 mm on the high side and 40 mm on the low side, so hopefully will not support a strong resonance. I will evaluate the effects when I mount the drivers soon. I did file off the sharp edge of the hole but it is hard on tools. Resin does not like to be ground at high speed. It smokes and stinks. If I can arrive at an effective low speed technique I will certainly have a go. It does not have to look pretty inside the box.
Just want to say great job Bon. I love to see DIY speaker projects with cabinets built to these standards. This has got to be in the top five list of all DIY cabinets that I have seen.

Regarding the resin, it may be possible to take it down quite rapidly with a course wood rasp while it is curing and is still in a kind of soft state. Past the sticky stage but before it gets hard.

The other option would be to make a sacrificial fillet out of foam that can be broken out after the resin hardens. You can also add clean sand to the resin to make it more dense and require less resin.
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Old 26th August 2012, 11:01 PM   #28
Bon is offline Bon  Australia
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,....why didn't you put the buckets into the baffle from the rear when you were pouring the resin?
John
Hi John. For the actual laying up I did reverse the bucket to what is shown, so the slight outward flare is towards the inside. You can see this in post #9. I just considered myself lucky to find something to fit the hole snugly in the first place but I will definitely consider widening the flare with a rasp. As a matter of record, I used a plastic storage container from my local hardware chain (Bunnings), for the smaller tweeter hole.
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Old 27th August 2012, 12:45 AM   #29
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Default Marine ply cladding

I decided to attempt a good furniture finish. I have no experience with veneering but found a supplier of high-grade 9 mm marine plywood with a very nice pinkish outer ply. Furthermore he was happy to select the sheets to closely visually match. The extra 9 mm skin will further stiffen up the enclosures and I finished the edges with 9 mm Tasmanian oak quarter round molding. The marine ply was accurately trimmed to size and applied to the mdf shell with liberal PVA. My advice to anyone trying this is to be liberal with the glue since the mdf is very thirsty for moisture. But definitely wipe up the squeeze out PVA. I find that PVA tends to shrink when drying, so a slightly proud glue line will pull in, whereas a flush one will sink and leave gaps. Also use fine (1.6 mm) nails to pin the panels, as they will tend to float. I used pins to hold the tassie oak edges in place too. I found that the bright nails I used to secure things while the glue dried, reacted with the PVA escaping around the nail to give a dark stain. Most of these are invisible after filling and sanding but some I could not hide. The stain seems to migrate into the timber. I donít know if galvanized nails would resist this, or even if they come in such small gauges. The marine ply improved the knuckle rap test result even more. The cost was the same as the mdf cost but the mdf was a lot more material. The cost of the wood products was not an extravagant amount of the build cost and considering the aim of this project is high, I donít consider the wood costs excessive. The corner moldings are applied after the marine ply and tolerances were set to allow the quarter rounds to be slightly proud and then trimmed flush with a straight router guide bit. Be aware that the size of hardwood molding vary considerably. After matching 3 m lengths for colour, I the found when I got them home, that the width could be Ī1 mm from the nominal 9 mm. The corners were rounded by hand sanding. The marine ply is sanded 120 and 240 grit. I found that the edges of the marine ply tended to swell slightly up against the hardwood molding. I went around each edge with maple timber filler and sanded back smooth. The plan is to stain the marine ply with a maple finish (Wattyl contemporary maple) and finish with polyurethane clearcoat for durability. An oiled finish has been suggested but this seems like it would require too much maintenance. Anyway I already have the clearcoat and spray equipment ready to go. I tried two maple stains on a piece of scrap, one waterbased (Cabots) and the other oil based (Wattyl). The water based raised the grain quite noticeably but the oil based, not at all. Apart from which, I prefer the colour of the oil based. So that is decided. This is where I am currently. Waiting for perfect spraying conditions. I have a cut-down gazebo erected in my garage as a spray booth. I use shower curtains for the walls and clear builders plastic for the roof. Itís worked fine for the baffle spraying which I will describe soon.
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Old 27th August 2012, 04:08 AM   #30
Bon is offline Bon  Australia
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Default Baffle painting

The bass baffle is straightforward to finish. I filled the joins between the hardboard and edge molding and sanded smooth with 240 grit paper. The hardboard surface needs slight roughness to key the undercoat/primer. After masking to protect the marine ply, I applied three coats of water based primer by HVLP gun, sanding lightly between coats. Then five coats of flat black water based acrylic, sanding between coats with 240 grit and 400 grit before the final coat.
The upper enclosure baffle was trickier. Firstly I masked up the baffle to protect the marine ply. Where the baffle joins the edge molding, and the join between the hardboard front and mdf faces, required relatively deep filling and was done in a number of shallower layers, sanding between layers and leaving 24 hours between layers. These were sanded slightly proud and then the complete mdf area is filled with a thin coat of wood-filler and sanded back flat. It took four cycles of filling and sanding before I was happy with the smoothness. I softened the filler before application by partially immersing the container in hot water. This softened the filler sufficiently that it could be applied by a wide (10Ē I think) plastic wallboard spatula. I prefer this heat softening to watering down. It is much less messy and dries much quicker. Looking at the surface under direct sunlight is very revealing of imperfections that you canít feel under the fingers, or see with artificial light. Then undercoat and base coat as for the bass baffles. Out of interest I painted a scrap hardboard panel the same as the baffles and clear coated one Ĺ and compared to the non clear coated Ĺ. The clear coat reveals many blemishes that are otherwise undetectable. I guess that is why ceiling paint is always matt finish.
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