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Old 10th November 2002, 01:11 AM   #21
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Very nice
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Old 10th November 2002, 02:47 AM   #22
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Default Re: Best way to cover a box?!?!

Quote:
Originally posted by WhiteBoyChriss
I was thinking laminent.
Laminate has the advantage of stiffening the box up & helping to push the box resonances up where they won't get excited as easily.

It is also fairly easy to do.

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Old 10th November 2002, 02:53 AM   #23
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Default Re: thanks Stew

Quote:
Originally posted by WolfmanX
I am thinking of laminating the entire cabinet in 1/4" or 3/8" cherry and sanding that down and adding a neutral stain and urethane to finish.

I didn't know if it would sonically harm the originally intended sound.
One of my buddy's (ChrisB) favorite finishes:

Click the image to open in full size.

He did up my pyramids in cherry. They look way better than when raw, but don't sound quite as good. I have to go in and add a few braces to push the wall resonances back up. I have some other (radical) mods i'm going to do as well -- inspired by the beautiful expanse of cherry on the back and the availability of some 6" PVC pipe.

Click the image to open in full size.

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Old 10th November 2002, 02:55 AM   #24
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Quote:
Originally posted by pinkmouse
Wolf, don't worry about the sound, the effects will be negligable,
I have to disagree... adding extra thickness to your panels will change the boxes resonance characteristics -- sometimes for the bad. You need to design with the extra wood in mind.

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Old 10th November 2002, 03:01 AM   #25
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Default Piano Finish

Below is a complete post from BASSlist member Delwin Fandrich on getting a "piano finish". It was posted 7/21/98.

=========== Delwin's post below ==============

OK. About that "Piano Finish" we hear so much about. There are two distinctly different finishes being talked about here. The traditional "hand-rubbed" piano finish and the more recent "high-gloss" finish. The high-gloss finish is polyester -- a plastic. Since we don't care for the look that this finish gives to pianos we don't use it and I'm not qualified to comment on its application.

The hand-rubbed finish is usually nitrocellulose lacquer. This material is quite easy to work with, just remember that it is extremely flammable -- explosive even -- so take care. It also stinks and it's not real good for your insides. You will need lots of ventilation, both to reduce the fire danger and to reduce the wear and tear on your lungs and your brain.

The following procedure works for both clear and colored lacquer finishes. If you are using black, I'd suggest using an automotive acrylic lacquer. Especially if you want a high-polish finish. Traditional nitrocellulose tend to look a bit blue or gray when polished out.

Step 1) Surface preparation. All surfaces must be sanded to a dead flat finish. We dry sand with an open coat aluminum oxide paper -- not stearated -- starting (usually) with 120 grit and working up through every grit to 320. When sanding flat surfaces the paper is always used with a firm rubber sanding block. All surface dings, scratches, blemishes, etc., are filled or fixed after the first sanding with 120 grit. All imperfections must be fixed before either the stain or the first coats of finish are applied. (The obvious exception being with a black finish which can be patched at any time.) After the final sanding we "break" the edges to a nice uniform radius using 220 or 320 grit paper backed up with sensitive fingers.

Step 2) If the wood is an open pore wood and the finish is to be closed pore, the next step is to pore fill. Pore filler is a silica base material that is thinned to approximately the consistency of heavy cream and brushed on both with and across the grain. Pore fillers can either be applied in their natural color -- a light creamy tan -- or stained to accent the pore texture of the wood. Once the pore filler is partially dry (the surface is just dull) it is wiped or scraped off across grain. A tiny amount of pore filler will be left in the open pores of the wood leaving the surface quite flat. Allow the remaining pore filler to dry for at least 24 hours and sand the surface lightly with 220 grit and 320 grit dry paper.

Step 3) If the wood is to be stained, now is the time to do it. We also stain the wood of pianos that are going black. It helps later when Johnny runs into the leg with his new toy truck and chips the finish. There are a variety of different types of stains available. Books have been written on the subject. For most amateurs the selection is going to be somewhat limited to what can be found at the local HomeBase or hardware store. These are usually oil based or water based stains. All I can say here is to follow the directions on the can.

Step 4) After the stain is dry apply the first coats of finish material. You can use sanding sealer if you wish, we do not. Sanding sealer is simply lacquer with some additives blended in to make it easier to sand. If you've done your prep work well you won't have to do that much sanding anyway and lacquer without the added stearates bonds better and is more durable.

(Note: If I were putting a black finish directly over MDF or particleboard, I'd first spray on a coat of black or dark gray automotive primer. These are very heavy bodied filling primers designed to fill in rough metal work and leave a fairly smooth sanding surface. It might take two coats.)

We spray three coats of lacquer straight over the stained wood surface. Allow this to dry (we allow 24 hours) and wet sand with 320 grit wet-or-dry paper on a firm rubber sanding block. Don't over do this. You're only trying to knock off the high spots here. Lacquer chemically bonds to lacquer so you don't need to "rough-up" the whole surface. You're getting rid of raised grain, dust particles, etc. (You didn't get any runs in the vertical surfaces, did you? If so, sand them out also.) What you don't want to do is sand through your nice new surface into the stained wood.

Step 5) Spray three more coats of lacquer on the surface. You're more experienced now so you won't get any more runs, right? Again, allow 24 hours of drying time and wet sand with 400 grit paper still on a firm rubber block. This time you want to sand the surface pretty well flat. Always sand with the grain and be extra careful around the edges.

Step 6) Spray on three more coats of lacquer. This time let the surface dry for at least three days. Wet sand, starting with 400 grit paper and working through 500, 600. If this is to be a "hand-rubbed" finish stop here. The final rub is most easily done with plastic wool sheets (the white kind without any built in abrasive) and pumice or rottenstone. If you can't easily find these, good old Ajax will work. So will automotive rubbing compound.

If the finish is to be more highly polished, continue sanding through at least 800 grit. Now switch to polishing compounds. We use 3M, but McGuires (sp?) is more commonly available. Visit your local auto paint store. There are about a million different compounds available and I don't even pretend to keep up with them. Find someone at the store who knows what they sell -- if you can -- and ask. The final polish will be done with a random orbital buffer. These might be available for rent. Otherwise, check Sears and/or head back to your local auto paint store.

The above is not intended to answer all of your questions about finishing wood. It's a complicated subject, but it's not an impossible subject for one who has already figured out how to build a speaker system. If all of this whets your appetite for fine finishing, might I suggest two excellent books: Understanding Wood Finishing by Bob Flexner (Rodale Press), and Spray Finishing by Andy Charron (The Taunton Press).

Achieving a fine finish on your work is not all that difficult. It does require some knowledge of the the materials you use and the proper techniques used to apply them. And some patience. Good luck.

Del Fandrich Piano Designer & Builder Hoquiam, Washington USA

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Old 10th November 2002, 09:09 AM   #26
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Quote:
I have to disagree... adding extra thickness to your panels will change the boxes resonance characteristics -- sometimes for the bad.
Really, Dave, I have never had this problem, and I have built a dozen or so pairs using this construction, and all have performed better than basic prototype mdf boxes.

Using dissimilar materials( sometimes called, incorrectly, constrained layer construction) means that the resonant frequency of exitation of both materials is different, and thus, if fixed together properly, will give a box that damps itself.
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Old 10th November 2002, 09:54 AM   #27
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Default RESONANCES.

Hi,

Quote:
I have to disagree... adding extra thickness to your panels will change the boxes resonance characteristics -- sometimes for the bad. You need to design with the extra wood in mind.
I agree with Dave here.
When deigning boxes you better know what it sounds like when it is excited by the woofers.

As with turntables there are basically two schools of thought:

1/The less resonance is better,so heavy,dead materials.

2/The lightweight approach,defending the fact that all lighter materials convert energy faster and therefore the resonance will be less bothersome.

IMHO,there is little point in going to great lenghts to avoid the cone break up mode if your box if going to sing along in the same range.

You can still go for the lightweight approach but I would then opt for mechanically stiff materials such as the Aerolam sandwich as used by some companies.

Cheers,
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Old 10th November 2002, 10:19 AM   #28
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I have discussed this before...

DIY aerolaminate for speaker box


Yes, the effect of adding a different material could be to add mass, but what I am talking about here, is decreasing resonances by using dissimilar materials, which is not the same thing

Quote:
IMHO,there is little point in going to great lenghts to avoid the cone break up mode if your box if going to sing along in the same range.
I agree totally, and the use of differing materials can help avoid sharp resonance peaks in a cabinet.
Quote:
2/The lightweight approach,defending the fact that all lighter materials convert energy faster and therefore the resonance will be less bothersome.
Yes and no, lighter materials on their own merely shift the resonances higher in frequency, for this to work, any light material has to be very, very, rigid.
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