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Originally Posted by sugrhigh /img/forum/go_quote.gif
Universal is a good place to start for sure I just figured someone making it them self would just go custom but that's good. As far as mold goes, if you need CAD work done let me know cause I would love to help out with the project and if it saves you some money even better
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Wow! That's cool! Thanks!
You're right. Why stop at a universal if you can go for a custom? My thinking is this: When the drivers arrive, the day after tomorrow (probably after 6 p.m. Eastern, because I'm always the last stop for my local UPS delivery guy), I'm going to take a lot of pictures, with hopes of posting them here. You don't get many pictures of these things, either from Knowles Acoustics or elsewhere, so I think various pictures of the drivers, in a real environment and from a variety of angles, are overdue. I want to hold them in my hand and give the curious an idea of their relative size. For some, that may be unnecessary, but I'm sure there are those out there who'd like a view of them outside any molds and in an environment a little more familiar than a small pic in a catalog.
Early on, I intend to solder some wire and experiment with them in different capacities. Each driver has a diminutive sound tube. I'd like to hear what it sounds like to do nothing more than place one or both in the vicinity of my ear canal. (Freaky, huh?) I'd like to also take some acoustical tubing and try different configurations. One experiment I'd like to try is to connect the tubing directly to a variety of ear pieces, just to see what these drivers sound like before they've been properly housed. In short, I'd like to try a few things, soundwise, prior to encapsulating them.
Project #1 will be the CI-22955 by itself, with a variety of universal fittings and configurations. With tongue firmly planted in cheek, I am calling this the Bilavideo 1.
Project #2 will be the TWFK by itself, as a dual driver, with a variety of universal fittings and configurations. This, you guessed it, will be the Bilavideo 2.
Project #3 will be the CI-22944 and TWFK paired together, without a passive crossover circuit. I'm curious to see, going in, what these two drivers, with different impedences and different SPL, sound like in the rough. This will be the Bilavideo 3.
One issue I am attempting to resolve, which is also an issue -=Germania=- has spoken of, is what to do for a crossover circuit. I've built my own crossover circuits in the past. I love doing it. It's really a lot of fun and gives you more of a hands-on experience in designing the "sound signature" of your system. But neither I nor any of my friends have ever built a crossover circuit small enough to fit inside an IEM shell. What's more, I'm not even sure about the necessity or utility of a crossover circuit here. Passive crossover circuits perform two functions: (1) They protect tweeters from being blown to bits by the wattage of a typical woofer; and (2) They separate frequencies so that different specialized speakers are able to do their job efficiently. After all, even if woofer wattage didn't give your $400 tweeters a stroke, who would want their tweeter to think it's a woofer? As I've run systems with and without crossovers (without blowing up anything), my more immediate issue was to keep my woofers from trying to sound like a tweeter. Without a decent crossover setting, woofers end up handling signals best leave to a midrange and tweeter, giving dialogue a kind of Darth Vader tone (Not every actor should sound like James Earl Jones in need of a cough drop).
But the mere claim, by a headphone maker, that an "integrated passive crossover circuit" is part of the mix, is not much to go on. It's a bit more complicated than that. If there's a crossover, at what frequencies it it set? What components are being used? With the kind of minimal wattage running through an IEM driver, how much is a crossover needed, at least to protect the driver? Having seen some of these little grease stains being referred to as crossovers, I'm wondering what kind of quality to expect? How good can a crossover really be when you're working that small? I'm wondering if the "crossover" claim isn't just a gimick.
Here's another wrinkle to the crossover question: If both of these drivers are really wide-range drivers, to what extent does the crossover issue even apply? The CI-22955 isn't a dedicated woofer; it's a wide-range driver with strong bass and midrange. The TWFK isn't a dedicated tweeter. It's a dual driver with an unusually flat response across the bass and midrange, with extended HF. If both of these are basically wide-range drivers, I'm not sure to what extent an integrated crossover is much more than cosmetic.
Going in, my assumption is that the use of acoustic filters - which is a mechanical way of controlling frequency output - will be much more influential. Knowles Acoustics sells tubing and dampeners, but the tubing is metal and the dampeners are $100 each, making them beyond the budget and beyond consideration. I'm not sure why tubing would need to be metal or why dampeners would need to cost more than $100, but plastic acoustic tubing - used in hearing aids and medical devices - is actually pretty inexpensive. Acoustic filters are also fairly inexpensive, even when sold by other IEM makers as replacement items. I intend to experiment with these before encasing any of these drivers into molds.
For those looking to extend their DIY mindset into the world of IEMs, one good source of materials is the world of hearing aids. These folks got here before we did and abound in supplies and materials useful to our particular endeavor. While looking for good acoustic tubing, I got a good chuckle while looking at supplies and materials used by the FBI in maintaining their stock of earpieces. Never in my wildest dreams did I ever envision myself pouring over descriptions of equipment used by the feds. Who knows? Maybe when the Secret Service is walking around, maybe they're just jamming out to the Stones. Hopefully it's not the Grateful Dead or Body Count.
If it turns out that the CI-22955 and the TWFK don't play well together, because the SPL on the CI-22955 shouts down the TWFK, simple resistors can be used to restrain the CI-22955 the way L-Pads are used to attenuate the mid/tweet and compensate for the 3 dB baffle effect. On my home stereo, my woofers were drowned out by my midrange and tweeters, and I got lousy bass until I bought a pair of L-Pads, which allowed me to scale back the mid/tweet. Through something as simple as volume control, I was able to restore some sense of balance, which unleashed my bass (which then had to be properly sculpted by setting a crossover frequency that would keep the bass from muddying up the midrange).
The nice thing about using resistors as in-line attenuators is that IEM bass can be properly tweaked. Once we take ownership of the IEM, and use our DIY intelligence to take a more hands-on approach, we won't have to sit at the feet of an IEM manufacturer and content ourselves with their explanations for why we should accept their choices as "good for us." I don't want to turn this into an Apple 1984 Commercial but somebody, preferably a blonde, needs to run forward with a big hammer in hand and hurl it through the big-screen TV so we can unchain ourselves and take control of our own sound.
With in-line attenuation tweaked according to the listener's tastes, IEMS can become "customized" by their sound signature, and not just by molds. But once we have what we're looking for, we'll be able to take the last step and encase the final product. I can envision an objection having to do with changes in sound after encasement, but if that's the case, why can't molds be made to be opened up, when necessary, for repairs or additional tweakings? Delusions of grandeur notwithstanding, there's no reason why we puny people can't reinvent the IEM to fit our own needs rather than what some company has decided we need.
