Bass In Closed Back Headphones Is Greater Than Open Back...but why?

[boomboxx]

I was having a discussion with someone about bass response in closed back headphones. Without technical knowledge, I always assumed this is because if the sound can't leak out it can't escape and will eventually travel to your ear through reflections instead of leaking out. However, the person I was speaking with tried to explain that bass does not reflect inside of headphones and can't bounce around but instead just traps it. This is where I am confused I thought trapping response will instead of reflect but create standing waves and create nulls instead of increasing bass response? But like I said I don't understand this subject at all and am not sure what is correct. Google was too vague so here I am hoping someone with a better understanding could help.

 

[alex-z]

Yes, closed back headphones generally have better bass than open back. Some of the low frequency energy will leak out, but a significant portion is reflected against the housing and returned to your ear.

Whoever you were speaking with is talking in circles. There will be reflections inside the headphone at all frequencies, which are "trapped" until they dissipate. The job of the headphone designer is to make sure the direct sound from the driver is vastly higher in level.

It is analogous to an infinite baffle vs sealed speaker.

 

[solderdude]

Bass response of closed headphones is determined by porting (rear side to the outside of the headphone) and the pads being 'not leaky'.
It is also baffle dependent, whether you have some extra porting to the rear side to control frequency response (not just bass, this affects the midrange the most)
When it is fully closed you get better bass extension but as a downside more seal dependent variation and some other side effects.
Speaker cabinets and headphone enclosures differ more than one might think due to the sealed front volume (pads)

 

[boomboxx]

Yes, closed back headphones generally have better bass than open back. Some of the low frequency energy will leak out, but a significant portion is reflected against the housing and returned to your ear.

Whoever you were speaking with is talking in circles. There will be reflections inside the headphone at all frequencies, which are "trapped" until they dissipate. The job of the headphone designer is to make sure the direct sound from the driver is vastly higher in level.

It is analogous to an infinite baffle vs sealed speaker.

Thank you, this is what I was assuming was happening but not sure if that leads to the increase in spl in lower frequencies or if it was just the way drivers are created that I think solderdude was implying. Regardless, I think he (the person I was speaking with) was very wrong about a few points. He tried to convince me sound waves were like electromagnetic waves (he used this because he first sent a picture of electromagnetic waves and how they pass through objects at different frequencies) and said sound waves act the same and the lower frequencies will most likely just pass right through the headphones but they're low energy enough to not hear them standing next to someone. I felt this was wrong because my understanding is that sound waves are similar to electromagnetic waves but different enough that they don't travel exactly the same at the same frequencies, which is why I thought some of the waves, lower freq included will reflect and return to the ear. But like I said I'm not by any means knowledgeable enough to know the right answers and was hoping someone with real knowledge could help which is why I am here. So I appreciate the responses.

 

[dasdoing]

The explanation never made sense to me, since plastic wont stop bass.
and actually when you look at leakage graphs on Rtings they don't differ much in the bassrange between the too.
there must be a better explanation

 

[kemmler3D]

The explanation never made sense to me, since plastic wont stop bass.
and actually when you look at leakage graphs on Rtings they don't differ much in the bassrange between the too.
there must be a better explanation

I assumed it was because closed naturally increases pressure, ability to pressurize the pad-ear space would be the limiting factor for SPL in the low frequencies, I guess? Don't really know though.

 

[DVDdoug]

and actually when you look at leakage graphs on Rtings they don't differ much in the bassrange between the too.

Of course that's the important thing! You can get good & bad headphones with either design.

I assumed it was because closed naturally increases pressure, ability to pressurize the pad-ear space would be the limiting factor for SPL in the low frequencies, I guess? Don't really know though.

If they were sealed around your ears you could "pressurize" the ear-side either way. But since they aren't sealed, with an open-back headphone the (out of phase) soundwaves can (theoretically) leak-around can cancel. I don't really know if it's an issue in the real world.

With open-back headphones the driver is only getting air pressure resistance on one side (the back side is an infinitely-large box), but I don't know if that's an advantage since with a closed headphone, the closed back side air-volume is usually larger than the ear-side volume.

 

[olieb]

headphones, here in a simplified sectional view

It seems clear that an open headphone has difficulties with bass.
Not so clear is this with semi-open ones (many planars). I doubt the acoustical short around the phone through the pads seems will have a very strong impact but some effect may be possible.
Perhaps it's not the principle, but the actual implementation that makes the difference:
diaphragm size , pad material, different tuning (ports).
All this does not have to be different between semi-open and closed. And many open planars are actually known for quite substantial bass.
So the question is first, whether comparable headphones do actually have different bass in open and closed versions.
(Beyer DT880/770, Audeze LCD2C/closed come to mind.)
And what is different? Max SPL? Frequency response?
Some of Crinacle’s measurements.

The Audezes look very similar with only a minor dip around 400 Hz for the closed one and slightly less deep sub bass.
The Beyers look like essentially like different headphones with different geometry and maybe other differences. Bass of DT770 (closed) is uneven and stronger below 100 Hz with a strong dip at 200 Hz.
This is not really conclusive.

 

[dasdoing]

Of course that's the important thing! You can get good & bad headphones with either design.

What I meant is that none of the materials used in over ears will ever isolate bass below 100Hz, so the trapping bass thing doesn't make sense.
here are the best passive bass isolators on Rtings (note that the bass definition goes up to 250Hz). no passive over ear does have any significant isolation below 100Hz where open headphones generally roll off

Headphones Table Tool

www.rtings.com