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post #61 of 2201
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post #62 of 2201
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Quote:
Originally Posted by gilency View Post
Westone cable is expensive but very nice.
I ended up with two solutions to the same problem. After comparing options between Westone, Ultimate Ears and Sennheiser, I went with the Westone ES replacement cable. http://www.westone.com/index.php?loa...=ACCM&offset=2 After I'd done so, Younglee200 told me about a stock of 28 AWG silver teflon wire on Ebay. So, for this project, I'll go with the Westone, but for future projects, I just ordered the silver teflon wire in a variety of colors. I'll probably braid it, sheath it in clear plastic and solder on the gold plated Neutrik 3.5mm right-angle connectors. That should take care of the wire and cable issue (I also got some 32 AWG tone-arm wire for the connections inside the shell).

Today, I got three more CI-22955's and another TWFK. Yesterday (or perhaps the day before), I got a box of connecting tubes from Micronic. I've got a couple more puzzle pieces to piece together before I assemble it all for the second prototype. But things are coming along.
post #63 of 2201
Thread Starter 
SOME INFO ABOUT ACOUSTIC DAMPERS

At the following site, Mid States Laboratories |Modification Links, there's an interesting discussion about the effects of dampers and tubes, some of which I thought I'd share here. For purposes of organization, I'll number these comments as follows:

1. The number of earmolds that are "modified" in some way is approximately 90%. Experience has demonstrated that an acoustic change produced by an earmold option will result in a more natural sound to a client than one produced in the hearing aid alone.

2. There is a predictable acoustic change occurring when an earmold is modified with a vent. The following are several general comments on the effects of venting on the low frequencies: .031 vent is primarily a pressure vent and it will have very little effect on the frequency response above 400Hz. .062 to .093 vents will tend to increase the acoustic energy in the frequency range between 500 Hz and 1000 Hz. The acoustic energy increases as the vent diameter increases. .125 to .150 vents will also increase the acoustic energy in the frequency range between 500 Hz and 1000 Hz. However, at some point, the vent may become large enough, in a small ear, to shunt the energy below 1000 Hz.

3. Attenuators used in conjunction with earmold modification influence the center frequencies. The amount of effect is determined by the density of the attenuator or damping plug, the number of attenuators used, and the location in the system.

4. Density is the same as damper resistance or acoustic ohms and it is determined by the material. Sintered balls, fiber plugs, even lambs wool, all create some acoustic resistance and influence the mid-frequencies, some more than others. The greater the density(resistance), the greater the reduction in the peaks of the frequency response. This smoothing effect created by any form of attenuator or damping plug therefore reduces the output and gain of the hearing aid.

5. There is an additive effect when using dampers. The damping plug will reduce both gain and output. The placement of the damping plug will influence the frequency response. Generally, the closer the damping plug is to the end of the tubing nearest the earmold, the greater the effect.

6. All manufactured dampers will produce predictable effects on the frequency response. The dampers available from Mid-States are the 680 ohm, 1500 ohm, and 2300 ohm dampers. Others may be secured and added to the earmold system after it is fabricated.

7. Horning or trumpeting is a technique used to emphasize the high frequencies in a hearing aid to create a "Horn" in the end of the earmold. The construction consists of an increase in the diameter of the sound channel to a size allowable within the constraints of the canal dimensions.

8. High frequencies can be enhanced by enlarging the bore of the sound channel.

9. Another earmold modification technique which increases the experience of high frequencies is to shorten the canal.

10. The reverse is also true. The most effective way to "choke" or reduce high frequencies through earmold modification is to reduce the diameter of the bore or lengthen the canal or both.

11. A pressure vent is recommended for all molds where possible. This improves the comfort factor greatly.

12. For high frequency emphasis on a short canal and a large vent is a common choice. Also consider using a bell bore.

13. For frequency response smoothing and alteration, consider Killion of Acoustic Horn construction. The vent may be used for pressure equalization, increase of low frequency response, or reduction of low frequencies.

14. Standard vent sizes are: small - .031, medium - .062, large - .125. Suggested bore sizes are: small - .055, standard - .118, large - .125.

15. Tubing length and diameter will cause changes in location and height of the frequency response peaks in a predictable fashion.

16. Moisture build-up in dampers is a common problem. Reduction of the moisture is possible by using an air blower, or the dampers can be replaced.

17. Accurate measurement of tubing and placement of dampers is essential to maintain published frequency responses.

18. Ear canal sizes will vary and could therefore affect final frequency response curves.

19. The higher the ohm rating for dampers, the greater the attenuation.

20. More attenuation occurs as the damper is moved closer to the earmold, however, this also increases the moisture build-up.

Phonak also has an interesting article about Acoustic Tuning, which is accessible here: http://www.phonak.com/com_028-0580-xx_focus_2.pdf

Acoustic Options http://www.perfect-seal.com/acoustic.html also has a straight-forward introduction to the three methods of "acoustic control." Among other things, it says:

Dampers

1. Lambs Wool - The first damping material used with hearing aids. The density of the lamb’s wool determines the damper effect. It is effective, but not easily controlled.

2. Sintered Steel Pellets - A series of steel pellets with different degrees of porosity which give different levels of acoustic resistance.

3. Star Damper - Star dampers are made of silicone and have no moisture build-up problems. They must be cut to different lengths and measured to know the exact effects.

4. Knowles Acoustic Dampers - These dampers are a refinement of acoustic control. Each damper is in a metal housing with a color coded plastic screen at one end. There are six dampers available: 680, 1000, 1500, 2200, 3300, and 4700 in Ohm values. Knowles Acoustic Dampers are the most convenient to use, but moisture build-up can be a problem.

5. In acoustics, the belling of a tube will enhance high signals passing through the tube. If a tube narrows toward the end, the high frequencies will then be reduced. Many of today’s hearing instruments produce high frequency signals out to 7000-9000Hz. Therefore it is important that the tube and earmold not restrict the resonance in the sound channel and cut off the high frequencies. Thus, in many fittings, a horn of some kind may be essential.
post #64 of 2201
Thread Starter 
I just got another two packages in the mail. The first was from Mouser, which sent me a pair of Knowles Acoustics drivers BK-26824. http://www.head-fi.org/forums/member...-ci-22955.html

These are among KA's most price-friendly drivers. They're a little smaller than the CI-22955 but larger than the TWFK. With an impedence of 29 ohms (16 at 500 Hz), these should be quite easy to drive. KA has no specs on them beyond an SPL of 129 and a sensitivity rating of 118. Because of their modest price ($36/pair), they might make a great introduction to balanced armatures for those who want to taste the difference but don't have a lot of money to do it with. Given the "house sound" of the BK series, they may also make a good midrange driver, especially with the right acoustic filter.
Last night, I found KA filters on the cheap at Microsonic at $13 a package. http://www.head-fi.org/forums/member...m-damper.htmlI don't know exactly how many filters there are in each package, but it's like buying a package of nails. KA recommends 680 ohm dampers, so I bought a package of 680s and a package of 1000s. There are filters that go all the way up to 4500 ohms, but there's no need to buy up the store before hearing these.

My second package was a box of materials, from Microsonic, for making ear impressions. At this stage, the goal is still to start with universals before fully committing to customs. On the other hand, I think the average "universal" could be greatly improved. Those who profit from the premium price of customs have little motivation to let their lower-priced universals directly compete with them in either fit or aesthetics. And while every ear is different, there are also similarities that ought to be built upon. Westone is, in my opinion, the king of ergonomics. Their universals are an amazingly snug fit compared to those of rivals. Universals present some compromises - such as the narrow sound tube between the shell and the tip - that may unnecessarily compromise performance. What if a common-sense bridge could be built between the custom and the universal, one that narrowed the gap? Is it possible to make a better universal?
post #65 of 2201
Bilavideo, Thanks for the great information!
post #66 of 2201
Uhm.... If I were you, I'd buy a bunch of DX orange IEM's, and use the parts/practice
post #67 of 2201
I think I recall reading some app note from knowles or something about termination options--I think the drivers usually come in multiple termination options (flex pcb being one of them) and that soldering directly to the terminals might not actually be what you're supposed to do. After all, someone along the line DOES have to solder these guys--I suspect these aren't actually manufactured by machine given the fairly small market (at least it used to be small) and the fairly complicated handling of the drivers.

The last time I opened my E4s (though there was a bad solder joint--it's been over two years with them, and one channel started getting funny frequency response, as if the bass disappeared slightly--turns out it's probably something with the mechanical seal, so there's really nothing I could do), I was able to successfully redo the solder joints on the guys fairly easily. The thing is, there was already a flex PCB from the knowles driver terminals which bent around to fairly large pads that were actually connected directly to the wiring.

basically, you'll probably want to find some way to do a strain relief on these guys (flex pcb, or anything else) and not attach wires directly to the drivers. btw, the flex pcb was also glued directly onto the drivers, so the flex pcb wasn't going to pull off the terminals itself
post #68 of 2201
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Quote:
Originally Posted by threepointone View Post
I think I recall reading some app note from knowles or something about termination options--I think the drivers usually come in multiple termination options (flex pcb being one of them) and that soldering directly to the terminals might not actually be what you're supposed to do. After all, someone along the line DOES have to solder these guys--I suspect these aren't actually manufactured by machine given the fairly small market (at least it used to be small) and the fairly complicated handling of the drivers.

The last time I opened my E4s . . . . there was already a flex PCB from the knowles driver terminals which bent around to fairly large pads that were actually connected directly to the wiring.

basically, you'll probably want to find some way to do a strain relief on these guys (flex pcb, or anything else) and not attach wires directly to the drivers. btw, the flex pcb was also glued directly onto the drivers, so the flex pcb wasn't going to pull off the terminals itself
Wow. That's an excellent suggestion. You captured the heart of it in two words: "strain relief." On the pair I successfully hooked up, I used hot glue as a form of strain relief for the wires I'd soldered in. I didn't know that that was what I was doing; it just seemed like common sense. Afterwards, I wasn't quite sure what reaction I'd get for following up my soldering with glue. What you're talking about would probably work even better. I appreciate the suggestion. I'm already a lot less stressed about the next phase of things because of it.
post #69 of 2201
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It looks like I'm going to be doing my own acrylic casting. There are inexpensive kits online but I don't really want to wait for shipping. If anybody knows of a major outlet that carries resin and catalyst, drop me a line. I'm not going to use friendly plastic because of its low melting point (100 degrees Fahrenheit). I also don't want to use anything opaque. I love that transparent/translucent look.
post #70 of 2201
Where?

Quote:
Originally Posted by Bilavideo View Post
... acrylic casting. There are inexpensive kits online...
post #71 of 2201
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post #72 of 2201
Hobby Lobby caries an acrylic compound for making "hand print art" with kids.
They do not have an online store do I can't show you a packaging picture but it's there.
In the kids craft section I'd suppose
post #73 of 2201
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Thanks, sugrhigh!
post #74 of 2201
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Awesome idea Bilavideo, kudos to you

I've been a lurker in these forums for some time now, only recently registered and this would be my first post

Wish you luck on your endeavour

Cheers
post #75 of 2201
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Quote:
Originally Posted by meraj.salek View Post
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Awesome idea Bilavideo, kudos to you

I've been a lurker in these forums for some time now, only recently registered and this would be my first post

Wish you luck on your endeavour

Cheers
Thank you for the words of support. You made my day.
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