How are the Sony MDR-D66SL Eggo's?

[BowerR64]

Quote:

Originally Posted by warubozu Bower, When you make the hole in the membrane, is it possible to carefully use a drill to make the hole instead of a soldering iron? The reason I ask is that I currently don't have a soldering iron. Can the membrane itself be removed from the ear cups?

The membrane is really thin, a drill isnt going to work. I think it will just rip it. Its pretty thin. You could use a metal nail and heat it up with a lighter. You can do the hole any way you like, this was the easiest way for me.
Quote:

Originally Posted by Tucker "WIth headphones i found it to be the oposite" Don't most people say that closed headphones have more bass and less soundstage? That's the general rule right? With the Grados, they have no room behind the speakers at all if they're sealed airtight, so that makes sense to me it would radically change the sound. Still though, I find it difficult to see why a pea sized hole would be needed. Doesn't the DT77o have like a couple milimeter sized hole, and isn't the pea sized hole by volume maybe 10x as large? So if it's just airflow, wouldn't a pencil lead sized hole work for the D66? Not trying to be a jerk, just curious. Also, how was your graph of the D66 pre/post mod generated?

I tried several ways, i have about 12 pair of eggos. First i tried them with the cups off. They didnt seem to sound as good as with the cups on. The cups add the midrange that i like from the eggos. One set i put a pea size hole in, the other set a smaller hole, then i got a set from some one on this site who ripped the membrane completly out. The pea sized hole had the best sound, bigger isnt better, and smaller restricts the air.

What you could do is carefuly remove the membrane and try some other way to plug the 1" hole the membrane covers and just try different size holes. Use model plastic glue to glue the membrane back in for the stock sound.

 

[Tucker]

You have 12 pair of Eggos? wow.

Also, I was hoping you were going to answer these questions:

How did you produce the graph comparing the before and after on the bass?

Also, why do you suppose the mod works? How does aiflow create bass?

 

[Jmmmmm]

Quote:

Originally Posted by Tucker Also, why do you suppose the mod works? How does aiflow create bass?

Everything that I can find says that porting a speaker shifts the frequency response downward, increasing bass. Also, a driver with no box and a driver with a ported box are not the same. I know these aren't specific to headphones, but they are the best I could find:
http://www.amptone.com/demeterssc1.htm
http://www.terrydownsmusic.com/techn...d_openback.htm

 

[Tucker]

Right, I'm aware that porting speakers creates more bass. However, I always thought that was for speakers with sound directed outwards... where all the listeners are: outside the speaker in an open room presumably.

In the case of headphones, the port is going out one side, into the room, where the listener's ears aren't. Meanwhile, the rest of the sound is going inwards to the ear canal, where the port isn't.

So, if someone is saying that the port creates more bass in all directions, just by virtue of being there, and regardless of shape, then I'd like to know how.

Also, how then do closed headphones usually have more bass, as it would seem that closing them should reduce bass.

Something is not adding up for me. Entirely possible it's just my ignorance of acoustic physics, and someone knowledgeable can reconsile these apparent contradictions.... but it makes me curious about how the mod is working.

From my readings of bass ports, they work when "the air suspended in the neck [of the port] resonates" in much the same way as someone blowing into the opening in a jug vreates a deep sound. That would explain why all the bass ports I've seen are shaped. However, I don't see how a simple hole can shape resonance in a membrane placed somewhat randomly, or for that matter a hole drilled in the back of the housing, can create this resonance, unless I'm misunderstanding how this works.

Also, according to the description given in the link you provided "This vent tunes the resonant frequency of the box such that the port vibrates in phase with the speaker cone. The cone driver becomes almost motionless and the sound comes mostly from the port."

So that's what's happening from putting a hole in a plastic membrane? The membrane is now resonating and the cone is nearly motionless? This doesn't seem right to me....

Anyways, it's interesting. Maybe someone familiar with acustic engineering could help out

 

[Tucker]

Interesting read on how speakers work:

http://electronics.howstuffworks.com/speaker10.htm

As I read that, perhaps what is more likely happening is that the port is simply making the speakers less efficient at channeling sound inwards while sending more sound outwards and allowing a less snappy diaphram motion, which could change the sound.

Regarding opening holes to release air pressure it says:

"The disadvantage is that there is no air pressure difference to spring the driver back into place, so the sound production is not as precise."

Maybe if the port was shaped, then it would shape resonance to produce more bass... however any hole=more bass....?

I don't think the mod is technically a "bass port" from my limited understanding on this. It's an air vent that changes air pressure maybe.

One possible explanation for the origional membrane is a design to maintain a certain amount of air pressure behind the diaphram, and also allow movement, maybe to help it snap back after an impulse.

Anyways, maybe the speakers create more bass when they are less snappy, and more loose, due to lack of air containment behind them. Maybe a less precise speaker is a bassier speaker... ?

It might be interesting to try adding the hole on the inside of the earcup, so that any sound escape, breathing, whatever, would be happening near the ear; and see how it sounds.

 

[xluben]

Tucker - If you actually open up the Eggo you can see that there is a hole (port) as described in your howstuffworks link. It is covered by foam (inside the earcup), but I believe it is the same type of hole as the Sony XD series while in 'Movie' mode. This allows the driver to produce two sound waves instead of one, just as the 'Bass Reflex' type subwoofer. There is also a hole that vents air into the slot around the edge of the headphone which directs air into the earpad.

About the membrane; BowerR64's theory (I believe) was that, as you stated,

Quote:

Originally Posted by Tucker One possible explanation for the origional membrane is a design to maintain a certain amount of air pressure behind the diaphram, and also allow movement, maybe to help it snap back after an impulse.

but BowerR64 theorized that the membrane was not flexible enough, thus resulting in the headphone being completely closed.

I believe that opening this membrane allows air to flow in and out much more freely, and thus actually makes the driver less snappy. Because of the decreased air pressure the driver is working against, it is able to move more easily, and thereby create more bass.

Less (air) pressure pulling against the driver = Full driver movement = More air being moved = More bass

While some of this added bass is obviously being lost out the hole in the membrane, much more bass is being pushed towards your ear due to the increased driver movement. The pea-sized hole is also small enough that some air is being pushed out the 'bass reflex' type port directing air towards your ear (but not directly from the driver). With a larger hole you will get more air being moved, but you will also have more being lost out the membrane hole, and therefore less being re-directed back towards your ear. Through experimentation (BowerR64's) I think that the pea-sized hole is the most effective for bass increase.

Herei s a diagram of what I believe is happening:

Here's a summary of my theory on BowerR64's bass mod:

As the size of the hole is increased, overall bass production is increased due to direct sound waves, and 'bass reflex' sound waves, although some bass is lost due to hole in membrane. As you continue increasing the size of the hole in the membrane the bass production due to direct sound waves and 'bass reflex' waves increases more slowing, while bass leakage continues increasing at a constant rate. Therefore bass output (to the ear) will continue to increase until a certain size when the amount of sound lost (out the hole in the membrane) begins increasing faster than the amount of bass gained (due to the decreased air pressure). Any size hole larger than this will result in less snappy bass, but no further increase in bass volume.

 

[BowerR64]

Im not really sure why the membrane is there but i think its to let some sound in. It seems just thick enough to let in a small DB of sound enough that you could hear a car horn honk and a decent volume.

If the membrane was made of a thinner material it could act like a passive filter. Some bass cabnets that are sealed use a standard driver, then use a pasive driver that has no voice coil. This adds some low deep bass, but thats not what i see happening on the eggos.

 

[Tucker]

Xluben-

Thanks for the effort, but sorry, but that description doesn't make any sense to me at all. I don't see any mechanism which is increasing bass in yuor diagram.

You've said "bass reflex" to explain the additional bass. However Bass Reflex is a phrase most people have heard through marketing, however it should refer to a specific design in the speaker cabinet.

Bass reflex is actually caused by either a port letting out air pressure which is shaped to create a bass voice through resonance, or a passive diaphram with physical properties to create bass, and moved by contained air pressure.

Since you've pointed out the enclosure is already vented, air pressure is already free relative to how little the driver actually moves in a headphone.

As far as I can tell, the hole should simply produce sound leakage.

 

[xluben]

OK, I guess this mod must not actually work, and it's all in our heads.

But, let's keep in mind who actually owns these headphones, and has tried it

jk, I'm not trying to be a jerk, but I don't see you disputing the mods for the Sony EX71's and Sharp MD33's which cover the holes behind the drivers to reduce bass.
On the EX71's at least (I don't know about the MD33's) there are holes around the front of the driver so that even with the mod these earbuds are never actually closed.

I think by trial and error it has been shown that, for headphones:
Bass can be increased by porting the headphones (behind the driver), and
Bass can be decreased by closing the headphones (behind the driver),
Even if the rest of the headphone is not totally sealed.

No one has actually described this scientifically, but I suggest you try it and then comment on how well it works.
For example: I did not find covering the holes in the back of my EX81's tightened bass noticeably, but opening the membrane in the Eggo's did increase bass to acceptable levels.


*These are just my thoughts and opinions, you don't have to agree, but please don't be offended by anything I have said.

 

[Tucker]

X-

I think you've misunderstood me. I'm not endorsing the mod nor denying it. I havn't tried it so I couldn't know positivly either way.

Having said that, it still doesn't make any sense to me and I'd hope someone could offer a scientific explanation of how it might work or some objective evidence.

Basically we have a hole being added to headphones, either on the back diaphragm or the back chassis, and that magically increasing bass.... You tell me, does that make sense?

Terminology such as "bass reflex" is being used, but real "bass reflex" actually refers to an engineered system which the hole is only the external visible part of and internal shaping of surfaces and/or additional passive drivers are what actually create the extra bass. The actual hole is just where it comes out.

Simply drilling a hole randomly placed in one's speaker cabinet does not create additional bass. A hole placed randomly on headphones should just let sound out.

Should anyone who wants more bass on some other closed headphones start drilling holes in them? If that's the case, why do many closed headphones have the more bass already, with open headphones often less bassy? Why does closing some other headphones increase their bass?

I know some people posted they had tried the mod and hear no difference. You posted you made the mod when they were quite new and not yet fully burned in, and before you were accustomed to them. Bower is an Eggo lover, having 12 pair. What anyone does with 12 pair.... ? That's great and good for him/her, but I think most readers have to take that kind of enthusiasm with a pinch of salt.

As far as other mods go, the web is filled with all sorts of mods that may or may not work and with something so subjective.... Anyways, that is completly unrelated to whether or not the D66 mod works.

So maybe the mod works, maybe people are imagining it, or maybe something is happening, but not exactly what ppl think. I don't know. I'm just trying to find out if there is any good reason to believe it would work. And don’t be offended if I don’t just take you and Bower’s word for it. Anyone who’d just take someone’s word for anything on the net…. Take my word for it: don’t believe everything you read on the net.

If an acoustic engineer can explain how the hole might work to make more bass, then I'd be very interested because I am curious and trying to learn something. However, from what I've heard and read simply adding a hole doesn’t make sense, although admittedly I'm no expert.

Anyways, I'm just curious and hoping to learn something about acoustics. No offense meant or taken.

I did come accross a post of your's where you said the same thing, that the mod doesn't make sense, so you should understand.. You said:

"I have read about this mod, and I do not see why/how it works. There doesn't seem to be any reason that allowing less are in/out of the driver housing would increase the frequency response at any level (bass/mids/treble)."

 

[Tucker]

Quote:

Originally Posted by xluben mods for the Sony EX71's and Sharp MD33's which cover the holes behind the drivers to reduce bass. On the EX71's at least (I don't know about the MD33's) there are holes around the front of the driver so that even with the mod these earbuds are never actually closed.

BTW: that's possibly a different scenario, like apples and oranges. Also, I don't know whether it actually works or if ppl are imagining it.

If it did work it could be because some earbuds have designed true bass ports, i.e. shaped ports engineered by the maker to create bass. Closing down a designed bass port would then shut down bass.

However, that's not the same thing as a randomly placed hole is it?

According the Bower, the main advocate and inventor of this mod, it works with either a hole on the back of the cups or in the membrane...

i.e. an unengineered ordinary type random hole creates more bass...

That's why I'm saying what you seemed to agree with at one point: this mod makes no sense.

Other ppl have pointed out that rationally what would make more sense is stuffing the chambers with cotton or something to reduce high end.

 

[xluben]

So, you don't believe in anything you don't understand? I think that could lead to a life of questioning.

I would suggest trying this mod yourself.

If you don't think it works, then it is settled, it doesn't work.

If you do think it works, then you can try and explain why.

Your rationale has disproven all of my theories. I cannot explain why a simple hole in the membrane would increase bass, but I still believe it does.
I guess when I'm listening to my headphones it doesn't matter how or why they sound good, just that they're enjoyable to listen to.
I am happy with how my Eggo's sound, so I am also happy I did the mod, whether it actually helped or not.

 

[Tucker]

"So, you don't believe in anything you don't understand? "

Not what I said.

If for example one is a Harvard accredited neurosurgeon, I don't need to understand neurosurgery to make a rational educated guess and believe it.

If it's some anonymous person on the internet making claims about subjective mods where there are plenty of other possibilities, and which seem highly counter intuitive and perhaps even unlikly... well then I'd be a fool to believe that. And I'm not saying I disbelive it either, just that it makes no sense, and some objective substantiation would be nice. It would afterall be nice of the mod did work.

The internet is filled with unreliable and contridictory info. Don't take it personal unless you believe all you read on the internet and suppose everyone else does too.

I just found this info on headwize FAQ regarding bass btw:

" How well headphones reproduce bass depends on several factors such as whether the type of phones is closed-ear, open-air or in-ear. The open-air types tend to leak sound, so the bass may not be as defined as with closed-ear types. Canalphones that form an acoustic seal inside the ear canal have excellent clarity, but the close-coupling tends to highlight the lighter quality of headphone bass."