[MacAttack7]

A good question!
Actually, it took me some time to understand, so it definitely needs some explanation.

First, upon using an impedance adapter, the volume is expected/implied to be matched to the same levels for proper comparisons.

Second, the primary purpose of impedance adapters is to better match a source and a transducer. A most common case is for a too powerful source that can deliver only few % of its power before making a transducer sound too loud, often with some background noise. In this case, a proper impedance adapter can dissipate some energy, so the source will be used at its higher (more optimal) power levels, often with less noise. (Again, volume matching is assumed).
An important point from here is that using impedance adapters implies having strong sources that can provide more power. Weaker sources, like phones, may not have sufficient driving voltage when used with impedance adapters.

Now, the third and most relevant to your question point, which I actually missed before, is that using impedance adapters may strongly affect power distribution to different drivers for multi-driver IEMs. Taking AST as an example, the bass BA takes most of the power in the AST crossover design, leaving less power for multiple treble drivers. As a result, AST sound bass heavy (too much for many) and somewhat gentle/anemic in treble (definitely too gentle for me). Using an impedance adapter with AST makes power distribution more even (more story to it, just not to be overly long). As a result, bass BA gets less power and treble BAs more with the great overall effect (to my ears, at least).

Now a bit of the background, the effect of the impedance adapters was brought to HIFiers' attention with KZ AS16 pro, where KZ admitted using wrong source setting of 18 Ohm for the source impedance, while tuning (they dialed the IEM impedance of 18 Ohm instead). So 18 Ohm impedance adapter should bring an original tuning (that is noticeably leaner (less bass, more treble again) and closer to original AS16; I like both versions). KZ actually promised to produce a properly tuned version of AS16 pro, but it did not materialize, likely because the "wrong tuning" actually worked out well, if not better, for most.

After learning from AS16 pro, I decided to test other all-BA KZs, and AST seem to be a similar case, as I described above. Given AST impedance of 30 Ohm, 25-40 Ohm adapters make the bass leaner, and treble more pronounced.
Also TRI Clarion tips are great for AST.

@cqtek and @paulwasabii may chime more on this, from them I learned most what I summarized above, my big thanks!

I miss Master Slater so much! Under his patience quidance, I started some simple moding to enjoy this hobby. He would be a really great person to contribute here with more insight and his great explanations.

Great and very timely mods now that KZ may feel to make KZ PR1 less relevant by the Pro version.

I will definitely try what I can do along your lines after I get my Pro (it is in a local post office since Friday, Canada Post do not do weekends...)

Thanks for the impedance class! I may order an adapter and see if I can hear the difference now that I'm curious.

 

[PhonoPhi]

Thanks for this great and clarifying post. I put AST bass down too much by PEQ. I think a mod would be better. I just dont know if I can go balanced. Impedance adapters are all single ended

Vety much ttue for the lack of the balanced adapters. I made few of my owns, but it would have grean they were available. Thinking about it, it may be more profitable for ChiFi to sell different versions of IEMs than adaptors.

Most important, good equalizers should give the same effect (the adapters are passive elements, not affecting the drivers), so if you are happy with equalizers - you can retune the power distribution to different drivers yourself.

 

[cqtek]

A good question!
Actually, it took me some time to understand, so it definitely needs some explanation.

First, upon using an impedance adapter, the volume is expected/implied to be matched to the same levels for proper comparisons.

Second, the primary purpose of impedance adapters is to better match a source and a transducer. A most common case is for a too powerful source that can deliver only few % of its power before making a transducer sound too loud, often with some background noise. In this case, a proper impedance adapter can dissipate some energy, so the source will be used at its higher (more optimal) power levels, often with less noise. (Again, volume matching is assumed).
An important point from here is that using impedance adapters implies having strong sources that can provide more power. Weaker sources, like phones, may not have sufficient driving voltage when used with impedance adapters.

Now, the third and most relevant to your question point, which I actually missed before, is that using impedance adapters may strongly affect power distribution to different drivers for multi-driver IEMs. Taking AST as an example, the bass BA takes most of the power in the AST crossover design, leaving less power for multiple treble drivers. As a result, AST sound bass heavy (too much for many) and somewhat gentle/anemic in treble (definitely too gentle for me). Using an impedance adapter with AST makes power distribution more even (more story to it, just not to be overly long). As a result, bass BA gets less power and treble BAs more with the great overall effect (to my ears, at least).

Now a bit of the background, the effect of the impedance adapters was brought to HIFiers' attention with KZ AS16 pro, where KZ admitted using wrong source setting of 18 Ohm for the source impedance, while tuning (they dialed the IEM impedance of 18 Ohm instead). So 18 Ohm impedance adapter should bring an original tuning (that is noticeably leaner (less bass, more treble again) and closer to original AS16; I like both versions). KZ actually promised to produce a properly tuned version of AS16 pro, but it did not materialize, likely because the "wrong tuning" actually worked out well, if not better, for most.

After learning from AS16 pro, I decided to test other all-BA KZs, and AST seem to be a similar case, as I described above. Given AST impedance of 30 Ohm, 25-40 Ohm adapters make the bass leaner, and treble more pronounced.
Also TRI Clarion tips are great for AST.

@cqtek and @paulwasabii may chime more on this, from them I learned most what I summarized above, my big thanks!

I miss Master Slater so much! Under his patience quidance, I started some simple moding to enjoy this hobby. He would be a really great person to contribute here with more insight and his great explanations.

Great and very timely mods now that KZ may feel to make KZ PR1 less relevant by the Pro version.

I will definitely try what I can do along your lines after I get my Pro (it is in a local post office since Friday, Canada Post do not do weekends...)

I really don't have much more to add to this comment, which is very well explained, by the way.
Just a question regarding the output impedance of the sources. Ideally, sources should have an output impedance close to zero. The reason is very well explained in this link, which I have shared dozens of times:

https://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html

As discussed in this article, a source with a high output impedance can transform the FR of the connected headphones, especially the more sensitive headphones with BA drivers. By placing an impedance adapter, the rule that the connected load must have 8 times the output impedance can be minimised. This may be another suitable use for impedance adapters.

https://penonaudio.com/accessories/earphone-adapters/3.5mm-impedance-adapter.html
https://penonaudio.com/l-shaped-impedance-adapter.html
https://penonaudio.com/accessories/earphone-adapters/dunu-3.5mm-impedance-plug.html

 

[G777]

Can someone explain what exactly a 25-30 Ohm impedance adapter would do for the sound of the AST?
I googled impedance adapters, but I can't find anything the really explains how it would affect the sound.
The ASTs are plenty loud already coming from my iPod.

Here's what it does to the FR:

 

[MacAttack7]

Here's what it does to the FR:

Does it depend on your output source as to what exactly it does?
I have an iPod Touch. I think it's output impedance is 1.74 ohms....not 100% positive as it's hard to find, but that was what I wrote down a long time ago from somewhere on the internet.

 

[G777]

Does it depend on your output source as to what exactly it does?
I have an iPod Touch. I think it's output impedance is 1.74 ohms....not 100% positive as it's hard to find, but that was what I wrote down a long time ago from somewhere on the internet.

The difference between 25ohms and 27ohms isn't significant in this case, so your iPod's OI probably won't have much of an impact.

 

[Aramaki]

 

[IEMbiker]

KZ EDX is in the mix. one of the best values.

 

[Aparker2005]

My AS16 Pros came in today. Absolutely love them! Only thing is when I was swapping tips, the silver mesh on the earpiece got pushed in some and unattached. Is this a big deal?

 

[MacAttack7]

My AS16 Pros came in today. Absolutely love them! Only thing is when I was swapping tips, the silver mesh on the earpiece got pushed in some and unattached. Is this a big deal?

My left one wasn't working properly, extremely muffled due to something being wrong with mesh as far as I could tell.
After I removed it, the sound was back to normal volume. It was slightly different from my other earpiece that still had the mesh, but not in a negative way, at least to me.
Just sounded like the mesh dulled the sound a bit, and after removal it was opened up. It wasn't that big of a difference.
If you remove one though, I'd remove the other also.

 

[Carpet]

My AS16 Pros came in today. Absolutely love them! Only thing is when I was swapping tips, the silver mesh on the earpiece got pushed in some and unattached. Is this a big deal?

Is that the new one with the altered impedance?

 

[lushmelody]

My left one wasn't working properly, extremely muffled due to something being wrong with mesh as far as I could tell.
After I removed it, the sound was back to normal volume. It was slightly different from my other earpiece that still had the mesh, but not in a negative way, at least to me.
Just sounded like the mesh dulled the sound a bit, and after removal it was opened up. It wasn't that big of a difference.
If you remove one though, I'd remove the other also.

Is it ok to keep listening to it filterless? No risk for the BAs?

 

[Aparker2005]

Is that the new one with the altered impedance?

Not sure, I got it during the 11.11 sale. And yeah I was wondering mostly on it being safe to listen to with the filter broken lol

 

[Carpet]

Is it ok to keep listening to it filterless? No risk for the BAs?

Some of the resin 3D-printed IEMs have multiple sound-tubes and no filter. None of mine have shown any problems with spontaneous BA failure (yet).

 

[lushmelody]

Some of the resin 3D-printed IEMs have multiple sound-tubes and no filter. None of mine have shown any problems with spontaneous BA failure (yet).

I think i'll try. My AST is temporarily shelved because the left cloth filter collapsed and lost shape last time I cleaned it. I was thinking of a low density non affecting tuning foam to substitute the terribly thin stock cloth