Wood & Varnish

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
 
Re: Re: diy varnish like the masters...

blumenco said:



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.
 
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.
 
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
 
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
 
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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Good thread, I read the entire thing from start to finish. Next speaker project I will revisit for a refresh on good finishing technique.

My last ones were baltic birch ply and are not deliberately adding something to the music, but perhaps are not as non-resonant as I would prefer.

The emphasis Clark has put on non toxic finishes is appealing to this asthmatic..
 
Although I've referenced these in other threads, they always get buried in the natural course of things, which is a shame. A selection of posts giving woodworking advice hints from our much-missed friend Terry Cain.

Suggestion for finishing birch, in response to the query below:

>Which would be the better choice for speaker cabinets with 4 mm Baltic Birch sides and easier to maintain for the long term? Yes, I am anal retentive and really love wood. TIA.

On birch I like a lighter look than tung oil. The air will darken birch nicely after a year or so regardless. Tung oil is very durable and fine for darker woods like gunstocks etc. but birch goes blotchy a bit. A better goo is polyurethane (oil based, Sherwin Williams or any oil based varnish gloss) mixed 60%poly-40%mineral spirits (maybe stiffer weather permitting) with min spirits and applied like a tung oil. Brush on and wipe off about 3-8 coats (24 hrs between coats min) sanding with 320 grit on a padded block. Then use a nice beeswax diluted into min spirits (shave the beeswax with a chisel a few days ahead)add lilac or juniper oil maybe some cheap perfume. Apply wax with #0000 steel wool and buff with cotton. And you have a faux French polish that will wear better than shellac. Has a stronger film against abrasion and moisture than tung. Smells good too. Basicall this is Simon Watts and Jason La Trobe Bateman's finnish, cabinetmakers to the Rothchilds, drawers and furniture etc. Some of the better Italian finishers inspect the cotton seed feilds the varnish is squished from, Varnish-o-philes. TC

Commenting on the sins of doing anything unnatural to pine...

Staining pine is tantamount to using dome tweeters and non polarized caps and playing LinkinPark all day. If you want pine darker, just put the boxes in the sun for a day or two. Or make a weak lye mixture (drano=1ea.tbsp to 1 qt water, spray with a plastic plant sprayer) to darken the wood with. This farkenniong has no pigment to gum up the look. Pine loves a rubbed varnish clearcoat (oil based). I like oil based varnish for it's darkening quality especially on pine. But applied like a French polish. Better water resistance and depth of color.

On natural products for staining woods...

Tea has ultra small well blended and mild pigment(s). Food always has worked better than common grounds and grindings for shading wood. This was well known to Parisian Haut'e finishers in the 1920's. Coffee and tea, another goodie is walnut husks soaked with a nail in some water, best on walnut for walnut. This brew d'noir evenly coats woodgrain without stiff looking saturation that ground mediums exhibit when they collect at the surface, right elow where you can wipe it off. Plant dyes will also work well as colorants in solution. I suspect that green tea may become a favorite of mine now that I'm thinking about it. I'm a pine guy tho, floors, dents and everything so I'll take mine straight thank you. It never looks good till after at least a year anyway. TC

There are many others of course, but that's a handful of some of Terry's more interesting remarks that people might find useful.
 
The original BBC research into damped, thin wall enclosures (as used in the LS5/3A) is a download at

http://www.bbc.co.uk/rd/pubs/reports/1970s/reports1977.shtml

The one you want is RD1977/03 "Factors in the design of loudspeaker cabinets." H.D. Harwood, R. Matthews

There is a similar article by

Art Ludwig

The thin wall ply approach is still used by Harbeth. and they also have some descriptions of the methods used and advantages.

The BBC site has some good stuff on speakers, courtesy of their research department (now disbanded).
 
It sounds a little like the "Sam Maloof Finish". Most of the recipes I've seen call for 1:1:1 BLO, tung oil and polyurethane. Others reference a recipe that includes mineral spirits (for enhanced wipeability) but as I understand it, it doesn't build as quickly.
 
Hi

My father was a furniture maker and french polisher; so I have been messing with wood work and polishing wood all my life. I have made a few sets of speakers usually from solid wood. Yes, I probably do like the sound of solid wood. The engineer in me tells me that solid wood cabinets are not neutral but, I still like the sound.

If you use a french polish or a varnish you can get a nice finish by applying more and more layers and thinning the layers as you add more. A good finish and highly valued by many. The problem is that it is a surface finish and marks easily. If you treat your speakers well - like no kids - it will survive. If you want a more resilient finish then danish oil, tung oill or some other oil are better as they go into the wood and are therefore more resilient.

I have used french plish on a set of LS3/5a and used danish oil on a set of Kef 107 clones.

If you want to clean/revive the surface finish the best treatment I have found is a mixture of equal parts of;
linseed oil
white spirit
meths
vinegar - spirit

Just wipe it on then wipe off and the surface will sparkle and be slightly oiled. Wax polish is not usually a good idea as it slowly builds up a layer of dirt that is trapped in the wax.

Enjoy the speakers.

Don
 
Bob Brines said:
While I stand behind my choice of MDF/cement board sandwich, I have been beaten into submission. I am now using plywood for my commercial speakers. It seems that the market equates MDF with "cheap" and is not interested the the real reasons for this choice of material.

Anyway, there is another argument going on: Should the speaker cabinet contribute to the speakers sound or should the cabinet be absolutely silent. My vote is for the latter. My logic is that a HiFi system should reproduce exactly what is on the recording.

I suppose that it is possible to build a cabinet that adds to the driver output equally at all frequencies, but I doubt that it will ever happen. Plywood and real wood cabinets that add to the driver output do so at high frequencies that produce "brightness". This synthetic brightness is perceived as "life". Have we had this discussion before?

I used to build cabinets out of a 3/4" MDF -- "Liquid Nails" -- 1/4" cement board sandwich. Any sound that escaped from the cabinet walls was inaudible at the SPL's common to single-driver speakers. I am now building cabinets out of 1" plywood. Again, any sound escaping from the cabinet walls is inaudible. I have played speakers made of the two materials side by side. I can here no difference. Mission accomplished.

Bob


Your cabinet design i built for the FT1600s are the best cabinets i ever built with regard to sound. They don`t contribute to sound reproduction, they just let the drivers and network do their job. I now use your cement board approach in all the cabinets i build. Thanks Bob, Steve.