cup tuning basics.

[liamstrain]

I think what we are wondering is if you go WAY past 1.5, to 2.25 or 2.5, if things start to clear up again. That would answer some questions about what is going on...  but that's also both aesthetically and usability wise challenging (not to mention eating up a lot of wood). 

 

[stratocaster]

Mid, I just checked the length of the olive cups I prefer. Guess what! 28.5mm --> 1.122". Holy s...!

 

[thelostMIDrange]

ok, now what about inside diameter and exit hole diameter?

 

[thelostMIDrange]

so 1.122 = about 1 1/8" correct. I've been wavering between that and the 1 1/4" set...seems like the lows are a touch more muscular on the longer set but the upper mids not as nice, and the other way around on the smaller 1 1/8 set. So , my final size may be in between !  wow this is 'nitty gritty' now.

 

[thelostMIDrange]

btw, would have been nice if somebody knew this a couple months ago, would have saved me from inhaling several lb's of limba sawdust to find out for myself..
 
 
thinking back, all my findings were either by accident or trial and error
 
the limba wood was lying on the shop floor in the corner from a past guitar buid (although I also tried a dozen or more other woods as well)
the length of cup was accidental. I was building 1.5" cups and the wood had a defect towards the end, so I cut it out and resulted in 1.25"
the inner wall thickness came to me because i thought it would look nice if i pared down the end detail into a cove
and my favorite sony headband was listed on craigslist locally. he had 3 for sale.
 
 

 

[thelostMIDrange]

plus you guys don't need to wonder if you doubled that 1 1/8"   to 2 1/4" (doubled the harmonic frequency) if the results would be 'better'......if you heard these cups, you would not imagine there would be a nicer low end imo. how can this low end come out of such small cups was my initial puzzlement.....but my ears have never lied to me. But it does get hard to trust them sometimes when'out on a limb' by one'self

 

[stratocaster]

And you can kill two birds with one stone. Blissful sound and comfort through smaller/lighter cups

 

[thelostMIDrange]

yes, plus, we look less dorky without the longer cups making us look like princess leah
 
 

 

[liamstrain]

that's a really unfortunate picture of that model... 

 

[thelostMIDrange]

you're right, she is cuter. it was the first result in my google search though .

 

[thelostMIDrange]

well I had an interesting afternoon....dear diary...... down to my local mumberyard for the weekly limba purchase. and who do I bump into but bil daly of daly finish, owner of one of the oldest paint anf finish stores here in seattle, and we had a very interesting half hour chat about violin finish, marketing BS, and other misc anecdotes ranging from a violin that came into him for a refinihs that was colored by chinese pigblood of which he had a hard time matching no surprise, to the marketing voodoo used by finish makers and suppliers, or which he is one of. He is an old timer and maybe the most knowledgable guy in my town regarding this stuff. It seemed as if he may not have much more time around here, as he was telling me several trade secrets to the myth of il pentration to encourage consumers to feel the need to put extra layers of material on thier projects to the topic at hand, violin finish. I inquired about belden violin finish, which is a common all in one solution and he pointed me towards a product which is the same thing except it costs 75% less and only difference is it has different alcohols used to speed up drying time. We opened up both products and did a smell test, he went over how to apply, drying times, whether of not another final finish is needed over top, buffing requirements etc.....regarding violin finishes, of which he seemed quite knowledgable andinterested in, apparently there is alot of folklore around it and some of the components are more for the visual enhancement not fou sound considerations, so he quickly learned i am a sound-first guy and directed me to what he felt would be the simplest, cheapest, leas invasive finish for my project. It's actually just a clear sanding sealer, a 'shelac', as is the belden violin varnish......he went into how the words shelac, varnish, poly etc are just words, and depending on the product can be the same thing. When he imports his custom made finish to japan for example they require a certain product to be labeled a shelac because they are very precise while here, the same product is labeled a poly etc........So short story, I have a finish and the correct application method. One day wait after first coat, 4 hours every one after and a week dry time for final cure....along with Liamstrain, it's nice to meet and get infro from guys who 'know their stuff' because it takes some of the voodoo out of it and reduces it down to basics, chemical, physics, acoustics etc and at bottom, that's really all this is. But for a right brainer like myself, it's magic. When i hear something and have no idea how it was achieved, it may as well be.....So now I know to wait a week with this particular finish before I listen and he emphasized that the sound will be dramatically different if listened to before the one week cure time........So wil be giving it a shot on the 'magic cups' I have fashioned. Should be good ! If not, there are a couple other 'varnish' ideas he gave me which may lead to other options.......Oh I also pointed to a can of 'shelac' and I told him I tried that one..Turns out that shelac had a wax mixed in with it..It's not labeled anywhere on the can though...Now I know why that one didn't sound good.....
 
And back to the limba. Had an interesting chat with lumbyard rep and come to find out, limba is actually quite hard to come by in most parts of the world. I always assumed it was easy because everytime i go in there (crosscut hardwoods) the seemed to always have plenty of stock. So if any turner would like to get into the wood and doesn't have access, I'd be happy to box some up and send it out. Shipping wood is not the cheapest thing to ship, but I think it is worth it. I  pay $11/bd ft.  btw for the material itself. I get 8/4 (2") and surface it down to 1 1/4" or I can leave it in rough 8/4 form if preferred........ 

 

[thelostMIDrange]

attn. LIAMSTRAM. Do you think that little ridge towards the bottom end of this cup has any real affect on the sound (waves) compared to if that were not there...meaning if the inside cylinder was totally straight and smooth from end to end would it be any different........I like to have that ridge to hold the grill mesh and it gives more width to the end profile. But if it's affecting sound I will have to remove it.......Would love to know your thoughts and possible theories as to it's importance.......thanks in advance
 

 

 

[liamstrain]

ultimately, I do not think that ridge affects much - I think it is the total length that is important. It might be an interesting test to see though. I would think maybe the differing wood thicknesses *could* have some effect - but I think less of one that the other geometries you've worked out.

 

[thelostMIDrange]

good to know. thanks much.

 

[thelostMIDrange]

had a chance to spend some time with 1 1/8" and 1 1/4"     will be going with 1 3/16"
 
Couldn't be more pleased with what I'm hearing. It's been a long road.
Wrapping up what we've found out. Sort of a summary of my 100's of hours of labor:
 
all wood has problems as a sound chamber, some more than others. Additionally, they all sound different, have different character. Generally I have found soft woods to not have enough attack and solidity in the sound, hard woods tend to be hard sounding and often strident in some area (s). The middle woods work best, meaning medium density. Limba is surely my favorite.
 
The geometry of the cup is as much or more important than the wood species. Even less than perfect woods would benefit from being shaped to a harmonious geometry. Getting the length right being most important followed by making the cup as resonant as possible by paring down the thickness of the chamber walls to 1/8" or less for at least the bulk or middle section of the chamber. The ends need to be beefier to house the driver and to accomodate some sort of decorative end detail, but whenever possible, I'd keep it minimal and non-ostentatious to keep the mass to a minimum. The more resonant the cup, the more alive and intimite the sound is, and this translates to more emotional connection with the sound. Say no to grado type 'endcaps'.
 
The finish matters, thin and non-intrusive is the name of the game. the finish totally changes the sound from raw wood state. It can be ruined or enhanced. The goal is to find a thin finish that doesn't take away raw wood desirable qualities and adds a refinement to the sound. The right finish will make the sound 'finished', less dry and gives more realism and truness to instruments.
 
Tuning the cup can literally change the entire character of a driver and sound. It is a revelation to hear the variation and range of poor wood with poor cup geometry and poor finish (totally detuned) to a fully tuned cup that is light and resonant and has musical geometry. The average cup being made I suspect falls somewhere in between these two extremes with the occaisonal accident of planets being alligned and a musical cup being made, but through the understanding of cup tuning, the guessing game and chance can be taken out of the equation and a cup can reliably be made to maximize the driver's potential. I have done this successfully so anyone wanting to do the same need only take all the hard work we've done here and carefully apply it and build upon it. With cup tuning, one no longer needs a rabbits foot to hang onto in anticipation if the headphone will sound awesome. It can be predictable.
 
violin varnish equivalent. It is a thin oil. two coats on the inside with a very quick and light wet sand (after a week cure time) and 2 coats on the outside seems sufficient to me. 1 day wait after first apply, 4 hours thereafter. This is a very easy to apply finish, goes on thin and dries quick. Doesn't require any top coat. 20 sec. light buff with cotton t shirt after a week cure time. Sound stability will also take a week. This is essetially a violin varnish without any additives for color and light reflection enhancements and a quicker dry time