As per Sonion document & chart I dont see tube length affecting bass frequency response. The chart shows highs being affected.
Tubing and damper will shape overall frequency response. With high damper value sound will become more bass-prominent. Also few dampers in series will result in low-pass filter which could actually shape bass response. The same thing is with tub diameter. Very very small tube (~0,1mm) will work as a low pass filter shaping bass response. But those are pretty extreme conditions rarely seen in IEMs.
Resistor in series with driver will actually cut bass quantity but will also make bass faster more precise. Good case-study would be CI driver which is warm and slightly bloated in sound but with resistor it becomes quite flat and fast, but would probably retain it's depth or note texture.
As for further crossover details I'll use graph. Below you see measurement of drivers. Both graphs present the same drivers with the exception green graph has woofers wired in opposite polarization than midrange and tweeter the result is canceling of low frequencies between two drivers.
Cap and resistor values, tube lengths and diameters are exactly the same, the only thing changed is polarization. Result: One set will sound warm and smooth, second will be more precise, faster, with more mid-presence overall brighter sound.
Hello all. This will be my first post to the thread. Awesome that it has been going on for so long. I have some various questions about iem construction that I would welcome any advice on. I've read all posts on this thread and have started buying some supplies to start my own builds. First, a little about what I'm doing and why.
I'm a musician and bandleader for a band that plays frequently. I run the P.A. on gigs. For six years we have used in ear monitors for the stage and will never be going back to on-stage speakers. I have always purchased iems for all members of the band. We have used custom molded single or dual driver designs from good companies. Most sets have lasted about one year on average before having connectors go bad or being sweat out. Needless to say even with more economical cans this is still a considerable expense for the band. Worse still is the down time of getting new ones made. I'm a very handy guy and have decided to try and make them myself. I have made some decisions already about what I want and do not want in my design. Maybe some of you can lend me your expertise regarding the design idea.
First off I will be using the Knowles dual driver design which is basically two BA drivers put together with one sound hole. I will use one acoustic damper in the connecting tube. I know there are TONS of driver/crossover possibilities here but for starters I'm shooting really straight on this one. If all goes well I'll use the newer triple driver on the next set of cans. This brings me to my first questions. What inner dimension tubing can I use for the Knowles GQ-30783-000? I bought some 2mm x 4mm silicone tubing but it's too big for the sound hole. Also, what do you use to secure it to the driver? I got some 1500 ohm and 2400 ohm dampers to smooth the peaks. Any opinions which might serve that driver better? I'll probably be placing the damper about mid way in the tubing which will be no longer than half an inch I'm guessing at this point.
As for the cable I'll probably be using donor cable from some of our graveyard iems. I want them to be fixed cord because they will break less often and if they do I'll be the one fixing them.
It seems that DIY acrylic shells have been the toughest part for many here. I won't be outsourcing them as that does not help my cause because of slow turnaround. I have some stuff and some ideas so I would really like some feedback on this part. I'm going to try a UV curing acrylic. I just received a tube of Loctite 3972. It's perfectly clear with a syrupy consistency. A test drop cured hard in sunlight after about two hours. I'm going to use a 36 watt UV hand box for acrylic nails. It should show up soon. This should closely mimic the processes shown in the factory videos of some of the pro companies. I've been pondering what to use for the negative cast to form the shell. I'm thinking of using clear ballistics gel. There's a company that sells a mixture in two different densities. clearballistics.com/ I'm thinking the stiffer stuff should be able to form on a wax coated silicone ear mold that's been properly dremeled. It would be clear so the UV light could do it's job on the liquid acrylic. Has anyone done anything similar to this?
Anyway, I'll be documenting as I go but I'll take all the advice I can get before I jump in.
I dont want to discourage you but DIY will be more expensive. The drivers if bought in small quantities will be more expensive. The whole trial and error with ear impressions and diy UV shells will also be more money. Other equipment like soldering iron , UV curing and crossover electronics, measuring mic etc. Also note the fit can be an issue with DIY, if you play for long hours with band it can be bit discomforting.
The reshells are lot cheaper these days you can reshell your old ciems or else other thing you can do is you can get normal iem where you can change cables and connectors and then just make custom tips from some professional guys.
You guys do know how to discourage one from doing some fun project...
Dan Jarros, good luck with your DIY. Obviously it takes trials and errors to make proper shell and IEMs and it's far more time/labor/cash-consuming than getting remold or even new IEMs. But the fun is completely different
It will be more economical than the ones I purchase. No doubt. A dual driver set from a company will be $300+. Here's a simple breakdown of what I'm shooting for:
Knowles dual drivers- $106 a pair. Triples would only be $140 a pair
Tubing -$1 I know you shouldn't use shrink tubing. Ebay stores are selling 2mm or 1mm silicone tubing for less that 2$ a yard. Anybody used this? Or does anybody know a distinct advantage for using the expensive hearing aid stuff?
Cabling- free-$25 some companies are selling iem cables for their product at this price. I've got at least 4 sets already from dead cans.
Silicone ear mold kit - 2$ Mega-Sils from an audiology online store
Wax for mold coating - $.02
Clear 20% gelatin ballistics gel for negative cast (if it works) - $12/lb - reusable lifetime supply
Clear containers for negative- $1 art store supply or other
Loctite UV acrylic material for shells- $20 on ebay - probably enough to do 8 sets.
36W acrylic nail oven - $20 on ebay
Dremel- got it
Time - got it
So, it's not gonna be close to what I'm paying now. And I'm not using $12 drivers like some of the cans we have. And I could do this in 2 days and that's the most important part.
All I need is some people with experience to help me with some of the details. So, my biggest questions so far:
Tubing size/supply for Knowles BA driver (smaller than 2mm ID) ?
Glue/ other way to attach tubing to the driver ?
Location and ohm recommendation of damper inside the tube ? I currently have 1500 or 2400 ohm.
Experience of anybody who has tried to do casting with UV acrylic material. Anybody know of a better clear material for the negative? Has anybody tried to use Knox gelatin for a negative cast? If so, is it strong enough to hold form and is it clear enough (it's brownish) for UV light to pass through?