Difference between open dome Small and Large... why use one over other?

Just wondering what the purpose of using different size open dome ends?
Reason I ask, I had to buy my HAs (P90) on a short trip back to states, audiologist had to order them and then ship them to me. So no in office fitting or discussion. When I received aids, my left had an open dome small, right open dome large. But they gave me 4 packs of extra domes, all open large. I’m waiting for audiiologist to return from holiday to do remote care/questions. in meantime, what is the purpose - is it for ear canal size?
My loss is mild/moderate. both ears are similar up to around 4k then the left drops off just a tad bit faster than the right. although the left is worse than the right by a tad the entire range.
i’m thinking the small dome was just a mistake/missed when they setup and programmed the aids. since my left is worse, i would think you’d want a larger dome to provide more volume??

thanks in advance.

Think it all depends on size of ears. No two ears are the same size.

Open vs closed vs power will determine how much outside sound is blocked. The size, s,m,l is for the size of the ear canal only. Small vs medium open domes work exactly the same on different sized ears. Make sense?

Thanks. I understood the open vs vented vs closed. Wasnt sure of the sizes in each. That clears it up.

I’ve always kept supplies of S/M closed domes and L closed domes for using with my aids. In some cases my LEFT ear canal seems to swell up a bit, and if that lasts more than a day, I swap in the smaller dome size for a more snug fit.

No dome is absolutely perfect - and I’d even say the same for custom-molded cases! My ear canals swell during the night, and even in different climates (humid vs dry). It almost seems an oversight that your aids ARRIVED with the different sized domes tho. Unless the audio actually measured or deduced one of your ear canals was markedly narrower than the other?

It absolutely depends on the size of your ear canal. Your audi gave that to you just incase you find your current domes uncomfortable, or if you find them constantly slipping out of your ear.

In my case, I have ridiculously small ear canals, so I always go for the smallest dome available. Otherwise, they start to hurt.

Pain in your ear canal is not a nice feeling.


So audiologist responded by email, saying the dome difference was for my different left/right hearing loss…

i’m not talking difference between types of domes, both are open. just one is small and one is large.

i’m wearing them with both large, open domes installed. feel fine.

Maybe upload your audiogram. It may help

Sure, when I get back home next week I can.
But my confusion is- if the size of the dome is strictly for differences in ear canal sizes then my audiogram wouldn’t come into play on what size dome is being used. And the reply from the audiologist would be more of a brush off than a thoughtful response as to why his office shipped on aid with a small dome, one with a large, and 20 replacement large domes.

It’s purely down to the size of ear canal.

My left wears a medium and my right wears a small. (I wear power domes at night to be able to listen to the radio.)

Same with my previous aids. I had a medium dome in my left and large in my right. The ReSound type is use right now seems to be fine with both being medium.
I can tell my ear canals are different sized from how a q-tip feels/fits in each ear