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Old 31st August 2008, 12:05 PM   #41
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Default some things to think about

Some things to think about are:

What is the core material of the plywood in question? Veneer wood might contribute a greater than 1/32 to the sound where it is used on both sides in 1/64 thickness on 1" thick material... but who knows....

It is my opinion that the characteristics of the core material, for various reasons will dominate the panel's resonant and aesthetic behaviour. Also, the core profile, being lumber core, 5 ply, 9 ply, etc. all changes things up a bit.

most plys in america are poplar, apple, birch core. I am likely leaving so many out, but I tended to stick with poplar and birch core plys as they are readily available and tend to sound quite good if used well. From rumor, I am really wanting to try out bamboo, but the sticker shock kept me from experimenting with it in any of my old "blumenstein" product. but if it had been custom ordered, that would have worked. I definitely have a willingness to bleed from splinters in the name of good music!

Finishing (either or both inside and outside the cabinet) really effects the sound. After a fair amount of research, I landed on Tried and true varnish oil as my personal best compromise, which is a polymerized linseed oil with no toxins whatsoever. It is incredibly easy and relatively quick to apply if you are patient and careful not to slop it on. (besides old t-shirts for application and clean up, and a shop kept above 70 degrees farenheit, patience is the only prerequisite tool). As a "proof" stunt, I would even taste a bit of the finish in front of a skeptical prospective customer (it did not taste great, but it also did not make me sick whatsoever...)

Terry Cain's contraction of Lou Gherrig's disease, some of us thought, might have had something to do with his ages spent as a cabinet maker in close proximity to burning woods in the winter that had finishes and paints on them, applying his finishes with no protection, sanding dust, etc with no protection. Back then, no one knew any better. But late in life, after his exhaustive research on the subject, Terry became a safety nut about toxins of all types. However, the research regarding the causes of Lou Gherrig's disease is still inconclusive and with my dad being a statistician in the medical field, I know much better than to draw -definitive- conclusions off the sort of data that has been collected so far (though there are some VERY interesting articles out there if you dig a bit...). But in either case, after all that went down, Terry's philosophy totally rubbed off on me and I resigned to be in intimate proximity with ANY sort of potentially toxic junk, no matter how good it looks on wood's surface.

So hence, my research was limited to the tonal aspects of only non toxic or low toxic finishes that a monkey could put on (big priority for me). Tried and True came out on top for BB. Highly recommended, and relatively cheap to boot!

Space bars me from giving all the details of application I figured out over the years of this relatively unique finish. but suffice it to say, the more hand rubbed the better, go to sherwin williams they should have "non washed" (new material) t-shirt rags. Clean just works better. A benefit of the stuff is that it does not pick up crap and leave it on the woods surface. it is a hand rubbed oil finish with no unnatural drying taking place. see a piece of poo somewhere? just wipe it off! even weeks later! wow, this did not happen with the high gloss laquers I tried.

There is "thin coats" noted everywhere on the can. They are NOT pulling your leg by saying this...it takes skill built up over a fair amout of time to get a truely beautiiful finish with the stuff, and even after all the cabinets I slopped this junk on, I am hardly a "master" at it. Considering that the formula is modeled after some of the stuff used in the old days, the skill factor does not surprise me...

Also, noting some issues of the old days, it is mentioned to not throw all the linseed oil soaked rags in a trashcan. they might cause a fire. used to happen all the time, apparently.

BB, at least the grade of it I was dealing with (and considering the dryness of walla walla), was incredibly thirsty wood. This particular linseed oil likes to REALLY flow into the pores of ANY wood, so unless extreme care is taken, the BB grain is risen, and all that nice sanding work is lost. The oil gunks up sandpaper quickly. Steel wool seemed like crap to me (leaving steel splinters everywhere, yuck!) So the only answer is to not eff up your work in the first place... not leaving any mistakes that cannot be taken out by further hand rubbing (and maybe just a tiny bit of finish sanding). Go quick and thin. The thirstyness of the wood, the wetting of the finish, and the kindof "syrupiness" to the finish I think all compound to contribute well, if only slightly to the damping of the surface resonances of BB panels.

Along with sanding, applying this stuff properly was a bit of a work out for me. For a speaker shop a good loud shop stereo (to get through the hearing protection...) is a must. I would throw on death metal, chaos metal (for those kind of nights), house, techno, tango music, reggaeton, african drum stuff, whatever got the blood pumping and got a good body rhythm going. Work up the tempo of your music as you learn the finish? Perhaps this aspect is just because of my age. No do not make yourself look like a workout video. Rhythm yeilding presicion is a very serious, very important aspect to repetitive labour, IMO. Man making machine that is supposed to sound like man.

I would tend to slop the stuff around a little more on the inside of the cabinet as a bit of raised grain gives a slightly more desirable unevenness to the surface texture? like a golf ball? I dunno. It was quicker to do it that way. A perfect surface textures for the insides of musical instruments, (or any non visible part of any piece of furniture for that matter...) tends to be avoided by builders, historically. Then again, the insides of many instruments are historically not finished anyways, so that is a key point where musical instruments and speakers diverge, perhaps.

Another thing I landed on seemingly was a concept that the same stuff ought to be used inside and out in order to give comparable acoustic environments. The outside maybe a little wax or something in addition to the finish only to polish 'er up, but it seemed that for instance if poly is used outside and thin shellac inside, while it diminished the sonic glare of otherwise all bare wood, still did not match up the inside and outside acoustic environments very well and robbed the "wholeness" to the sound slightly. Truely, this is just a theory though. I have not tried this out on enough surfaces and speakers to make a general conclusion. YMMV.

There are other options to explore with other wood types, and perhaps there is even other stuff out there that I have no idea about. but I really liked the linseed oil with birch. There are violin varnishes, shellacs, so many options out there, that might give a lighter, dancier sound. I dunno. It is really fun to explore these options, because if you are dealing with high quality finishes in the first place, by trying out different ones you usually end up with various "flavours" to the sound rather than stuff that "works" and stuff that "doesn't." So barring an individual's lack of preparation and training for each finish leading to crappy looks, you almost always end up with an acoustically and visually usable result (ALWAYS try each new finish out on several pieces of scrap wood first and treat them like as if they were the finished product...really get a handle on the stuff before going for prime time).

Ok, freak out in a moonage daydream ohhhh yeah.....!

-Clark
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Old 31st August 2008, 01:36 PM   #42
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Default Re: diy varnish like the masters...

Quote:
Originally posted by moray james
http://www.instrumentmaking.keithhil...invarnish.html

wow... fantastic link...

any more hidden treasure like this keith hill guy you know of?
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Old 31st August 2008, 01:55 PM   #43
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speaking of...

yeah. his book is rather appealing...If I had the money...

WOW!
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Old 31st August 2008, 01:56 PM   #44
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Default Re: Re: diy varnish like the masters...

Quote:
Originally posted by blumenco



wow... fantastic link...

any more hidden treasure like this keith hill guy you know of?

Project Guitar

The PG Forum

You will struggle to find people better at woodwork anywhere else on the net than at this site ^

They can also be incredibly helpful and patient.

The guides in the first link aren't much to do with building speaker cabinets, but they'll teach you all the tricks instrument builders use to get flawless quality.

However, I would strongly suggest keeping questions within the tangible world if you sign up at the forum.
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Old 2nd September 2008, 12:27 PM   #45
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Default Wood thickness?

I noticed that in the Nagaoka Tetsuo book of speaker plans that some of enclosures specify 12mm, and others 15mm and 21mm, depending on the design. My question is; would it be detrimental to the design of the enclosure to use 3/4" BB, for a design that specified 1/2", assuming I made the necessary dimensional changes to keep the exact same horn path widths? I have a lot of extra 3/4" wood laying around in the shop and would like to build the F-81 (small FE83 based design) from book #5. I also like to use my biscuit joiner with 3/4" for quick assembly.
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Old 2nd September 2008, 02:30 PM   #46
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Take a look at my website:

blumenstein-ultra-fi.com

Striking resemblance, huh?

It is not the same speaker, I went beyond (evolved) the original dims to the new version FE83e) (larger in some areas, different expansion rate) but is the same basic layout.

Marvelous speaker, IMO. Highly recommended bang for the buck, assuming that you can keep the wood cost down (they actually use a fair amount). Don't skimp on the amp!

I think that 3/4 will be fine. pretty thick though... There is a "confined" energy that can be present from too thick of wood, IMO. Stronger for the sake of overbuilding is not always an "advantage, IMO" It is all aesthetics in the end.

You could also try a lighter wood, like douglas fir, poplar core 3/4 material. that might have a little more "bounce"

be sure to finish the insides, and, well, just DO IT. you can saw off the bottom panel to later try damping materials, sand it flush, stick a spacer back in there and put on a new bottom (with screws). glue is important though. I think that in the book, after I had it translated, said to put damping "along the bottom" meaning the bottom panel. I later moved beyond this, but it is a good place to start.

in the end, enjoy!

-Clark
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Old 2nd September 2008, 11:51 PM   #47
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Clark,

Thanks for all the info! You're the first person that writes about finishing the insides and I'll take your advice for this pair.
Your website and speakers are eye candy for an audiophile for sure. Love the photography on your site also!
I'll let you know how the speakers sound, but I'll likely not get started on them for a couple of weeks yet.

Thanks again,

Derek
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Old 3rd September 2008, 02:05 PM   #48
Colin is offline Colin  United Kingdom
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This topic comes up so many times in one form or another, would a permanent thread of links (or Wiki) be a good idea?
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Old 3rd September 2008, 02:48 PM   #49
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Good idea Colin afaic. Made this thread permanent.
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Old 3rd September 2008, 02:52 PM   #50
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I second that.

I would be willing, and I know that alot of other people here would be willing to put up information about "construction details." of all sorts of speakers. There are many different approaches that can be covered.

Sure, some professionals will hold onto a few of their trade secrets. But I personally feel that sharing as much information as I can is essential to the growth of the community and craft. People sharing information with me has brought me great happiness and saved me lots of money and unnecessary tedium. I can only hope to even begin to be able to give back what I have learned from this and so many other communities.

the thing is, that yes, if approaches are outlined, there is the fear of many people taking a less creative approach. however I think that more often than not, it will help keep people from needing to "reinvent the wheel." To encourage further creativity after being given a head start is essential though.

Can we add a wiki function to this forum?

It would not be too hard to write, especially if people stuck to more positive statements about each technology than simply "bashing MDF," or any sort of approach for that matter.

I personally try very hard not to succom to "value rigidity" as outlined in Zen and The Art of Motorcycle Maintainance. So any approach holds water if done well, IMO.

-Clark
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