Calling all sound engineers - how does the soundtube leading from a BA driver affect the sound of an IEM?

[Madebynick]

Hello everyone, I hope you're all well.

I'd like to pose this question to anyone on the forum who perhaps studies/studied as a sound engineer or has a detailed knowledge of the physics of sound...

"How does the orientation and alignment of the sound tube (I'm afraid I don't know a more technical name) leading from the BA driver to the exit ports on an IEM affect the sounds I hear? Specifically, if the sound tube has a curve to it, does this affect the way I hear the sound?"

In short, I am interested to learn how these soundtubes that I can see in clear IEMs - specifically customs - affect the reproduction of recorded sound. I can only imagine that in an ideal world that this tube would be completely straight and lead from the exit of the driver, to point directly at the ear drum. As this is unlikely to be the case in the majority of individuals, how would one determine the best orientation for this driver/tube/exit port in order to deliver the best sound?

In addition, would the length of this tube affect the sound at all?

I would be very interested if someone was able to explain this in a way I, a non physicist/sound engineer, can understand.


Nick

 

[Sonic 748i]

Quote:

Originally Posted by Madebynick /img/forum/go_quote.gif Hello everyone, I hope you're all well. I'd like to pose this question to anyone on the forum who perhaps studies/studied as a sound engineer or has a detailed knowledge of the physics of sound... "How does the orientation and alignment of the sound tube (I'm afraid I don't know a more technical name) leading from the BA driver to the exit ports on an IEM affect the sounds I hear? Specifically, if the sound tube has a curve to it, does this affect the way I hear the sound?" In short, I am interested to learn how these soundtubes that I can see in clear IEMs - specifically customs - affect the reproduction of recorded sound. I can only imagine that in an ideal world that this tube would be completely straight and lead from the exit of the driver, to point directly at the ear drum. As this is unlikely to be the case in the majority of individuals, how would one determine the best orientation for this driver/tube/exit port in order to deliver the best sound? In addition, would the length of this tube affect the sound at all? I would be very interested if someone was able to explain this in a way I, a non physicist/sound engineer, can understand. Nick

Good question, I will like to know also. =)

 

[mvw2]

It's a neat concept. I'm sure some research on the internet can find you some basics. Off the top of my head, I can see tube length affecting frequency response to some extent based off wavelength. It would be similar to running a long versus short tube tip. For example, the Westones come with two Comply tips, one long, one short. The sound signature between the two are a bit different. The only major difference is tube length as the ends terminate the same way.

One of the main aspects has to do with tube resonance. Unless the tube is sealed right at the driver, the system can operate in an open chamber prior to the tube. It ends up being driver diaphragm->open chamber->tube->tube exit. The tube length is effectively a tuned port. Depending on sizing, it may be more than likely tuned within the bandpass of the earphone, and this will affect the end frequency response as well as the operation of the driver itself (think ported subwoofer enclosures and its effect on excursion).

You can get into more interesting aspects when you step away from a single port design. For example, the Triple.Fi 10 is a dual port design. There are issues with the placement of the bass and mid/high end tube relative to the ear drum. This can become a time alignment issue and affect relative blending and presence of the end sound. Driver placement within the earphone becomes important. How you wear the earphone is important. You may be able to run a long tube tip and help negate variation.

 

[ethan961]

My ear canals are slightly kinked, which would place a bit of a kink in customs if I got them. I too am interested how this affects sound. Universal IEMs also don't go as deep in my ears as for others due to this, but I feel I get the same sound that people normally have to insert deeper to get. Unfortunately this makes most IEMs stick out of my ears more than for others, but it works.

 

[Madebynick]

Interesting you say that Ethan as I have kinked ear canals too. Twas another reason why I was asking this question; I am considering custom sleeves but am not sure if they would fit into my ears properly and whether the resulting sound tube drilled in the silicone would ruin the sound from the earphones I have grown to love. Tricky one huh?

Thanks for the info mvw2. Your mention of the multiple ported IEMs is an interesting one. I've seen UE tune their headphones by adhering them to a mic with what looks like plasticine and then moving their drivers and tubes around until they can match a particular sound curve. Very clever!

 

[LFF]

YouTube - Amazing homemade trumpet made out of a hose

 

[semisight]

Quote:

Originally Posted by LFF /img/forum/go_quote.gif YouTube - Amazing homemade trumpet made out of a hose

No way, that's awesome! So I guess it changes resonance frequency. But shouldn't the goal of the engineer in making customs be to eliminate all resonance? Maybe it shifts whatever resonance there is to above human hearing frquencies

.

 

[tatabox]

this might be of interest:

http://www.knowles.com/search/pdf/TB-06.pdf

other pdfs:

http://www.knowles.com/search/technical_bulletin.htm