[dodap]

In the last years IEM manufacturers crammed ever more ba drivers in their in ears. The latest craze I found is the U 18T that incorporates "8 low drivers and 8 mid drivers with the high and high-mid drivers", 18(!) drivers in total.
I understand that to a certain degree it can be usefull to split the frequency response into three or maybe even four ranges and give it a specialized drive for this range. Of course it gives the problem of the overlap and the difficulty to design a proper crossover to achieve a smooth level over all and no phase errors.
But why this massive amount of parallel drives for a given frequency range? I know that big living room loudspeakers and especially loutspeakers for bigger audiences very often have multiple drives, but sound pressure is obviously not that big problem with in ears. Why is it worth to undergo all that problems to squeeze those ba drives into a tiny shell? Except of course as a big selling point, as for most people more of a good thing equals a better product (faster CPU in a smartphone, more horsepower in a car for instance).

 

[Koolpep]

BA drivers are small - you want more headroom to move more air if needed, you need to put a few in parallel. Newer BA drivers though somehow are more efficient so numbers needed are likely to drop... I assume.

https://www.knowles.com/products/premium-sound/what-is-balanced-armature

Or Interview with a PHD in Audiology (Dr. John Moulton, a.k.a. Wizard of Nobel Audio):
http://audio-head.com/an-interview-with-noble-audio/

Quote from the above:
How does the implementation of more drivers (per frequency group) influence the overall sound?

John: Honestly that is a very difficult question to answer. Something of a mantra concerning the physics of sound in audiology was, “You change one thing, you change everything.” One thing you will see in marketing jargon is “Increased controlled bass, that doesn’t influence the highs…” or things along those lines. That is a lot of hocus pocus, as if you understand bass, and the phenomenon of “upward spread of masking” bass will impact highs. Anyhow, that is a tangent. Your question was how does the implementation of more drivers influence the over all sound. Well lets get back to bass, bass is necessary, if it wasn’t for bass the drum would not exist as we know it, and neither would the bass guitar. If a single driver IEM can not realistically produce bass due to the physical limitations of the driver, then it would be appropriate to introduce a driver into the mix that can do so. Long story short, multiple drivers, when done well, can add more texture, more life, and more realism to the music.

Many IEM manufactures implement BA (balanced armature) drivers similar to the ones found in your products. What have you found to be the advantages of this type of driver? Do you have any plans for a dynamic driver?

John: I like BA drivers mainly because that is what I was exposed to as an audiology student, and even before that. What a lot of folks don’t know about the “Wizard” is that I come from a family of Audiologists. My father also has a Doctorate in Speech and Hearing Sciences, so I was around hearing aids since the days of diapers. I spent a lot of time in hearing aid labs growing up, so I use what I am most familiar with. Beyond that, the laws of physics state that it takes more energy to set an object with a larger mass into motion, it also requires more time/energy to stop a large mass object. (Train versus a car) Keeping this logic into perspective, BAs has a smaller mass than a dynamic driver, so what we find is BAs respond faster, “attack and release” would be the audiology term. Some people feel that faster response results in superior sound quality; I happen to feel the same way. That being said, Dynamic Drivers are much cheaper than Balanced Armature drivers, so from a profits perspective dynamic drivers are a superior driver.

 

[dodap]

What you wrote and quoted, Koolpep, sounds convinving as a general answer. Why BA drivers are used at all and why they set dynamic drivers back to second place. Even the use of parallel drivers seems to help. My oldest IEM, the UE triple.fi 10, had two bass drivers already. But 3 or 4 or even more?? When more loudness dictates more driven volume of air and this can be done more easily with parallel drivers, why not in the good old days od dynamic drivers? Only because the space in the shell did not house more than three or four? And is a series of drivers really to be driven without negatice side effects? Frequency response differrences, phase problems, whatsoever?

 

[Koolpep]

I have a few multi driver IEMs and I find them incredibly coherent sounding. One with 10 drivers per ear piece is especially liquid and organic sounding.
Crossovers, freqphase, etc. have been mastered. However, the recent resurgence of fabulous DD flagships is interesting too CA Atlas, IMR R1, etc.

On the other hand multiple DD drivers were used by Fidue, Tin Audio, some Japanese companies and others before....

BA drivers can be produced with a very good amount of precision nowadays - so I don't see that as an issue. However, technology progresses.

I think that for in ear pieces the diaphragms shape and sound channeling with multiple DD drivers would cause space issues, but is has happened before. Also take a look at the JH Audio Lola https://jhaudio.com/p/lola-custom and , the Ultimate Ears UE6Pro http://pro.ultimateears.com/ue6pro

Different solutions for getting to the same goal - make a great sounding earphone.

And look at speakers:

 

[dodap]

It seems that designers of bigger floorstanding boxes have had the same thoughts: To get those damn big boxes as "tiny" as possible they took several smaller bass drivers and stacked them for a smaller profile. I am not shure why even drivers for midtones were doubled. And in order to minimize the frequency crossover problems very seldom you will find four way designs (costs aside, really big and expensive ones have them of course now and then). At least in advertising hifi boxes the companies vers seldom put emphasis on four way beeing better than three way or two drivers for a range better than one. I have heard quite some boxes in the last decades but 18 drives as an argument I cannot remember anymore if this has ever existed at all outside the lunatic fringe of course.

 

[Koolpep]

With speakers it’s easier to have a wider frequency band per driver and you need less crossovers. BAs can be very specialized to specific bands. And the amount of drivers, well if you want massive bass with BAs some manufacturers use multiple sub and low drivers. But then the mods and highs are too recessed so these drivers need more juice too, so you end up stacking them up. I guess as BA technology evolves, like with the new vented bass drivers that are in some IEMs, less drivers might be needed in the future. Example the Campfire audio Comet. Single full range BA driver. Entry level, but hey, a great accomplishment. So I have a feeling that the need for massive multi BAs IEMs are over. Recent top models of certain brands seem to settle for 4 to 6 drivers to accomplish what needed double the amount a few years back.

 

[Jnjy]

In the last years IEM manufacturers crammed ever more ba drivers in their in ears. The latest craze I found is the U 18T that incorporates "8 low drivers and 8 mid drivers with the high and high-mid drivers", 18(!) drivers in total.
I understand that to a certain degree it can be usefull to split the frequency response into three or maybe even four ranges and give it a specialized drive for this range. Of course it gives the problem of the overlap and the difficulty to design a proper crossover to achieve a smooth level over all and no phase errors.
But why this massive amount of parallel drives for a given frequency range? I know that big living room loudspeakers and especially loutspeakers for bigger audiences very often have multiple drives, but sound pressure is obviously not that big problem with in ears. Why is it worth to undergo all that problems to squeeze those ba drives into a tiny shell? Except of course as a big selling point, as for most people more of a good thing equals a better product (faster CPU in a smartphone, more horsepower in a car for instance).

Not really a secret that “parallelism” benefits the business aspect. More drivers crammed allows higher margins. Its just how consumers minds work, that business folks tap into.

On the technical side, having multiple independent drivers actually introduces phase issues.

 

[Koolpep]

Not really a secret that “parallelism” benefits the business aspect. More drivers crammed allows higher margins. Its just how consumers minds work, that business folks tap into.

On the technical side, having multiple independent drivers actually introduces phase issues.

What do you exactly mean with phase issues? Thanks to multiple sound bores that's pretty much solved, no? Shouldn't we have the same during any live performance with a gazillion of speakers? Anyhow - maybe that's the secret sauce of the MultiBA flagships - they overcame that using different techniques. I cannot hear any phase issues on my 12 (4,4,4) driver in-ear. But again, I don't think that amount of drivers is needed anymore with the latest tech.

And for the marketing part... I find that not to be anymore true. Especially with the resurgence of single dynamic flagships and TOTL IEMs - a dynamic driver even of the highest class cannot possibly be the reason for a $2000 in-ear universal cost wise, as DD are comparatively cheap. I feel it's the limited expected sales volume that drives the prices up as well (besides greed?) - if you have two engineers working on a flagship design (maybe some R&D too?) for 2 years, then the costs for tooling and producing the crap, then bringing it to market with all the associated costs, you gotta charge a pretty penny to break even eventually if your market research tells you, you might only be able to sell a thousand of these....

 

[dodap]

The crazy prices and crazy technologies of current high end IEMs have two sides: Obviously the manufacturing companies pushed these two trends, in regard of the enourmously encreased prices (over the last years at least) it is of course the drive to generate more revenue. And it seems that it was no big technical problem to cram ever more BAs into the IEMs. But the other side had to accept these trends too: As in high end territory very often a high price is one of the "objective" measuring sticks for quality. Expensive things simply must sound better. I am not in the position to decide how much snake oil effects can be seen here too. But if a company can sell these IEMS for instance more or less to professional musicians then the have to deliver on the technical sound level. With audiophiles I am not so sure that everyone of them really hears or "needs" these technological changes/advances. In the end it worked these ways because the IEM companies could and wanted to deliver and the market accepted this. At least in a niche big enough for all those boutique shops that sell theses IEMs.

 

[Jnjy]

What do you exactly mean with phase issues? Thanks to multiple sound bores that's pretty much solved, no? Shouldn't we have the same during any live performance with a gazillion of speakers? Anyhow - maybe that's the secret sauce of the MultiBA flagships - they overcame that using different techniques. I cannot hear any phase issues on my 12 (4,4,4) driver in-ear. But again, I don't think that amount of drivers is needed anymore with the latest tech.

And for the marketing part... I find that not to be anymore true. Especially with the resurgence of single dynamic flagships and TOTL IEMs - a dynamic driver even of the highest class cannot possibly be the reason for a $2000 in-ear universal cost wise, as DD are comparatively cheap. I feel it's the limited expected sales volume that drives the prices up as well (besides greed?) - if you have two engineers working on a flagship design (maybe some R&D too?) for 2 years, then the costs for tooling and producing the ****, then bringing it to market with all the associated costs, you gotta charge a pretty penny to break even eventually if your market research tells you, you might only be able to sell a thousand of these....

It isn’t surprising that live performances with “gazillions of speakers” are attended by folks who resort to alcohol and other unpronounceable substances to compensate for or hide the lack of sonic quality. Hey, I go to venues like that too and sonic quality is not my main motivation.

Phase issues always occur when you have more than one transducer. Say, both of them are driven by the same electrical signal, manufacturing imperfections will always cause them to reproduce that signal differently. Those differences in waves generated will cause destructive interference. Sound tubes do not help because waves still end up interfering with each other at the exit bore. They even make it worse because waves hit so many obstructions inside the tube, creating secondary waves, which in turn cause more interference with primary waves. The only way to reproduce a signal cleanly is to use one driver with a direct path.

 

[Koolpep]

The crazy prices and crazy technologies of current high end IEMs have two sides: Obviously the manufacturing companies pushed these two trends, in regard of the enourmously encreased prices (over the last years at least) it is of course the drive to generate more revenue. And it seems that it was no big technical problem to cram ever more BAs into the IEMs. But the other side had to accept these trends too: As in high end territory very often a high price is one of the "objective" measuring sticks for quality. Expensive things simply must sound better. I am not in the position to decide how much snake oil effects can be seen here too. But if a company can sell these IEMS for instance more or less to professional musicians then the have to deliver on the technical sound level. With audiophiles I am not so sure that everyone of them really hears or "needs" these technological changes/advances. In the end it worked these ways because the IEM companies could and wanted to deliver and the market accepted this. At least in a niche big enough for all those boutique shops that sell theses IEMs.

I agree with you, but audiophiles are a very special breed and flagships getting more and more expansive is an issue for sure. But on the positive side - what you can get today for $50-$100 is spectacular compared to what one could get for that money a few years back. So while flagships go up in price, the entry level and mid level offerings are getting better and better for the same price. So - not a bad development.

Cheers.

 

[Koolpep]

It isn’t surprising that live performances with “gazillions of speakers” are attended by folks who resort to alcohol and other unpronounceable substances to compensate for or hide the lack of sonic quality. Hey, I go to venues like that too and sonic quality is not my main motivation.

Phase issues always occur when you have more than one transducer. Say, both of them are driven by the same electrical signal, manufacturing imperfections will always cause them to reproduce that signal differently. Those differences in waves generated will cause destructive interference. Sound tubes do not help because waves still end up interfering with each other at the exit bore. They even make it worse because waves hit so many obstructions inside the tube, creating secondary waves, which in turn cause more interference with primary waves. The only way to reproduce a signal cleanly is to use one driver with a direct path.

Ok, but why do the multi driver IEMs sound so good then?

 

[Jnjy]

Ok, but why do the multi driver IEMs sound so good then?

“Sound so good” is subjective. I’m not arguing there. If it’s good for you, that’s great to me.

 

[Koolpep]

Sure - hearing is always subjective. However, wouldn't all these musicians using their multi BA CIEM setups complain if they would be riddled with issues? Why do audiophiles love these? I am not saying that single driver IEMs can't sound amazing (the opposite....

I have a feeling we will be asked to move into sound science soon...

 

[Jnjy]

Sure - hearing is always subjective. However, wouldn't all these musicians using their multi BA CIEM setups complain if they would be riddled with issues? Why do audiophiles love these? I am not saying that single driver IEMs can't sound amazing (the opposite....

I have a feeling we will be asked to move into sound science soon...

Science class is over. Nothing more can be said.
I don’t question preference with multi driver devices. Some musicians are, pardon the harshness, sponsored. Nothing wrong with that, but it begs the question of whether they really prefer those or otherwise. Audiophiles enjoy music, and to the point where purity is secondary to an impressive experience. People always tend to go larger than life if they have the chance, don’t they?