Bose QuietComfort Headphones Mods & Conversions
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Starting a thread to document some of the stuff I did on my Bose QuietComfort phones.
If you have done mods/repairs to your QC's please contribute.

my reasons of wanting to playing with Bose QC's:
* Bose active-noise-canceling is very effective, especially in reducing the low frequency noise. Even the older generation such as QC2 is effective enough for daily noise blocking purpose.
* the QC's are comfy and light, can be worn for very long sessions.
* the consumable parts are standardized, inexpensive and widely available. Replacement headband and comfy earpads can be had for around $10...
* The QC's have built-in amplification, there is no need to use external amp.


I have QC15 and QC2. While the QC15 noise-canceling is about twice as effective as the QC2's, therefore great for air traveling, it is too powerful for daily office use. At times the QC15 ANC makes me feel like I am on a plane, want to lower my jaw and "equalize" the inner-ear pressure, while sitting at the desk. The QC2 has good enough ANC and is as comfy as the 15, can be worn all day long.

Modes and Experiments so far:
Headband chassis replacement: page-1, post #2
Driver upgrade, iGrado drivers: page-1, post #3, #5
Cable upgrade, SPC/Teflon: page-1, post #6
Driver upgrade, Nhoord Red drivers: page-2, post #18
Craftsman's damping mods (link): page-2, post #19
 
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Headband replacement (more robust steel headbands)
* this was done on QC2. For QC15 it is about the same.

I bought a pair of used QC2 for cheap (~$20) from powerbookMedic, mainly to see how the older model's ANC compares to the QC15. The plastic is old and the yokes soon disintegrated at the swivel joint...



I found an old PC phone chassis laying around, why not just do the handband transplant... the result: about as comfy as the before and weights about the same (~2 grams heavier). The steel band/wires construction should hopefully last a while.



 

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Driver Upgrade
QC2 and QC15 have 40mm 32 ohm drivers. If I want to improve the sound maybe I can put in some better drivers. The entry level grado drivers are 40mm and 32 ohms, might be a good fit.... how about using the drivers from iGrado (available on ebay for $35).

To remove the Bose driver, remove as much of the yellow/tan glue around the driver as possible, using a pair of fine-tip tweezers. unsolder the wires and lift the driver up and out.



iGrado driver extraction:
first remove the foam ear pads and pry out the two plastic plugs


undo the screws and separate the driver housing from the neckband



Snip off the four baffle locking tabs and separate the baffle from housing





Unsolder the wires;
Bend the tab by hand and the pry the driver off...



And, surprise!! (to me at least), the iGrado driver is NOT 40mm! Not a direct fit! What the #%^&!!! where did I get the idea that entry level Grado's are 40mm?


However, all is not lost... the space allowance is 44mm max, by trimming off the little ridge around the driver recess the Grado drivers can still be mounted...
 

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okinear

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Drivers are not solely characterized by their size and impedance, it would be too easy :o2smile:
What about their response curves to start with?
 
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Driver upgrade, (using iGrado drivers) continued

Looks like the max allowable driver size is around 44mm; But to use such drivers the partition wall in the cup will need to be removed.


And... it turned out that the iGrado driver will fit the baffle without needing to trim off the little ridge. The driver simply fits over it.


Cutting off the partition wall in the outer cup is still needed, though


I attached the two pieces together using some thick tape for easier handling. It is probably easier to just glue/hot-glue them together.


The driver leads are too short to reach the iGrado soldering pads --> add short extensions wires.


Put everything together and powered up for a listen...everything works, no crazy oscillation. the iGrado driver phase marking matches the stock driver phase marking, no need for reverse wiring.

so how does it sound... (quick A/B between iGrado'ed QC2 and a stock pair )
-- with the iGrado drivers the volume is noticeably louder. Better efficiency?
-- ANC works about the same
-- sound from iGrado pair is a bit more detailed (but not by too much), wider sound stage and more up front. Clear and Very warm sound.

so far so good, now the problems:
-- bass is over-powering. Even with 1 gram of Acousta-stuff per cup (was barely able to keep them in there), the bass is still boomy at times. Definitely falls into bass-head category.
-- for some reason the right side is slightly louder, needing 5 steps of adjustment (out of total of 63 steps) to balance out. It might be because of the iGrado drivers (diaphragm of one driver has a white hazy look, the other one is clear), or Bose uses non-matched drivers and relies on the gain adjustment in circuitry to match the final output.

Would I recommend the iGrado driver transplant.... if you are a bass-head, sure; otherwise, maybe not, the improvement is noticeable but not as much as I have hoped.
 

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Audio Inputs:
the socket module has a 4-wire ribbon.

in the photo, from top down:
connects to the tip, not sure what it is for
right
left
(red wire) ground



the left signal goes through a 20 ohm resister and to a 2.5uF ceramic capacitor (circle in red in the photo)
the right signal goes directly to pad #9 on the board --> handband cable --> right ear cup.

Cable Upgrade?
since the QC has internal amplification, the cable functions more as an interconnect than a headphone cable. I got curious and made a RCA --> 4-ring-plug cable to try out.

Cable length 5ft, ground wires (yellow) are 24awg silver-plated-copper with Teflon insulation; signal wires (black) are 32awg silver-plated-copper, Teflon insulation as well.
To match Bose's "king of consumer grade headphones" prestige, I terminated this fancy cable with Monster RCA ends! (though the Monster ends were taken from some old component video cable...)



Plugged the new cable into my USB soundcard (Musicland 2.0 which has both headphone jack and RCA line-out) and did a quick A/B between the RCA cable (connected to line-out) and with a 3-ring-input headphone cable (plugs into headphone jack):
The first thing I noticed right away was the sound stage widened a lot with the RCA cable setup. The low level details are a bit better as well. It felt much more "there", actually took some getting used to.
Switched to the headphone cable setup: the sound stage is smaller, more focused and a bit distant. Overall doesn't sound as clean.

I much prefer using the line-out -> RCA cable setup. Not sure if the difference was mainly from the different cables, or from the different signal source (line-out vs headphone jack), though. Probably both.
 

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Craftsman

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Driver Upgrade
QC2 and QC15 have 40mm 32 ohm drivers. If I want to improve the sound maybe I can put in some better drivers. The entry level grado drivers are 40mm and 32 ohms, might be a good fit.... how about using the drivers from iGrado (available on ebay for $35).

To remove the Bose driver, remove as much of the yellow/tan glue around the driver as possible, using a pair of fine-tip tweezers. unsolder the wires and lift the driver up and out.



To be continued...
Before replacing the drivers themselves, I would recommend that you try the modification I did by putting in additional sound deadening into the cups and see how you like the sound.

I've found in the past with regular loud speakers that most cabinets in the lower end speakers can and should be modified to improve the cabinet's response which in turn will improve the performance of the drivers. Closed headphone cups probably fall into the same possible performance improvements as the design philosophies are very similar to speaker cabinets.
 
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okinear

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Owning neither Grado nor Bose...
Best luck for your modding. Sounds like a difficult art.
Fuzzy science?
 
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Not reall
Owning neither Grado nor Bose...
Best luck for your modding. Sounds like a difficult art.
Fuzzy science?
Not really fuzzy science...

Many of the points about speaker cabinet and sound deadening have been proven time and time again on a larger scale with loud speaker cabinets and car audio - see https://en.wikipedia.org/wiki/Loudspeaker_enclosure. As such, the science itself isn't fuzzy. The problem really is the lack of the proper application of the science on the headphone level especially when it comes down to lighter weight headphones.

Granted many of the techniques used in loud speaker construction cannot be applied at the headphone level due to size and space limitations. However, a few basics, like increasing the perceived volume of the can by using some filler material, or loading the can's surface to reduce the echo or reverberation effects not part of the original sound, can and should be applied to headphones. These relatively simple and low cost modifications will maximize the performance of the existing drivers and therefore, improve the performance of your headphones. Will they cure all of the headphone's ills? No of course not. But even if you cure some of them, things will sound better!
 
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Owning neither Grado nor Bose...
Best luck for your modding. Sounds like a difficult art.
Fuzzy science?
who said anything about science? It is just for some simple DIY fun...
 
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Not reall


Not really fuzzy science...

Many of the points about speaker cabinet and sound deadening have been proven time and time again on a larger scale with loud speaker cabinets and car audio - see https://en.wikipedia.org/wiki/Loudspeaker_enclosure. As such, the science itself isn't fuzzy. The problem really is the lack of the proper application of the science on the headphone level especially when it comes down to lighter weight headphones.

Granted many of the techniques used in loud speaker construction cannot be applied at the headphone level due to size and space limitations. However, a few basics, like increasing the perceived volume of the can by using some filler material, or loading the can's surface to reduce the echo or reverberation effects not part of the original sound, can and should be applied to headphones. These relatively simple and low cost modifications will maximize the performance of the existing drivers and therefore, improve the performance of your headphones. Will they cure all of the headphone's ills? No of course not. But even if you cure some of them, things will sound better!
yes damping is needed but the stock drivers simply don't have enough resolution. And since we are using the internal circuitry which runs on just 1.5V and even includes ANC function... I suspect the iGrado drivers will be about as "high-end" as it needs to go.
 
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yes damping is needed but the stock drivers simply don't have enough resolution. And since we are using the internal circuitry which runs on just 1.5V and even includes ANC function... I suspect the iGrado drivers will be about as "high-end" as it needs to go.
Are you basing your observation on just listening to the stock drivers in the stock environment or do you have actual specifications on the drivers themselves?

If you are basing it on the listening to the stock drivers in the stock environment, then the driver itself only makes up a portion of the resolution. The echoing and reverberations from the enclosures themselves will create a lot of 'noise' or resolution destruction that won't be there if the enclosure was well dampened. As I noted in my original post (https://www.head-fi.org/threads/bose-headphone-mods.503432/page-3#post-14419424),
When I got the QC15s, I did a quick listen to them using a few bassy passages and you can feel the bass causing the cups to vibrate even at relatively low volumes. Just put your fingers on the cups and feel the vibration. That's not good... Once I opened them up and removed the cups, points 1 and 3 were clear. The plastic is so thin in some parts that it was translucent if you shine a bright light on it from the other side (you can clearly see the oval of the silver trim from the backside of the cup) so chances are, given the right music at the right volume, the whole oval area with the Bose logo will start to vibrate - not cool.
So, there's a lot of noise being created by the cups themselves that's interfering with the sound. Then, if you factor in the ANC function which may also introduce resolution issues through the internal amplifier as well as possible feedback from vibrations from the music through the cabinet (after all, the microphones are in close contact with the drivers), there might be a lot more to improving the resolution of the headphones than just the drivers themselves.
 
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agree, we can probably do a lot with stock drivers in place, but is it worth the effort? I are not trying to do R&D work for Bose on their now discontinued models. If I am putting that much effort into my QC2's, might as well start with some "audiophile-approved" drivers and build up from there.

( to me the QC15 ANC is too powerful, I will leave them alone for plane uses)
 
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Actually, yes. One has to believe that Bose for all of their poor reputation for producing actual audiophile stuff has put at least some thought into the initial engineering for the QC series headphones - after all, it's what they are really known for and have the largest market lead as even their older models blow the doors off of many current competitors when it comes to ANC. It was only after the accountants and the production engineers got their hands on it that they really started to make things cheaper while charging the same amount of money to their customers.

So, if we take the premise that Bose did good engineering in their electronics and the general set up of the QC headphones, then you can also make the jump in thought that Bose might have matched the drivers, microphones and the electronics together. There are various reports across the 'net about how some QC owners have replaced blown or dead drivers with others only to have them perform poorly in comparison. If Bose actually used the lowest of low end drivers, some of those who replaced the factory drivers should have seen some performance increase with the new drivers... but they didn't.

Bose actually answered your question with the QC25 - they made massive cup design change by encasing the driver in it's own 'mini-cup' rather than depend on the larger 'outer-cup' like in the QC2/QC15 - they knew there were issues with the quality of the cups. In comparison reviews, users reported better sound from the QC25s over the QC15s which if you look at basic speaker design theory and what a sealed enclosure does to bass response (it tightens it up but at the same time dampens it) which is just want the QC25 does.

As for the amount of work, really it will take you 5 minutes to do what I did as you have already taken apart the cups. You just need to get some sound deadening material which I would say would be much easier to get (and cheaper as well as you only need about a quarter sized piece for each side - about $1 worth of materials) than replacement drivers from a iGrado.

As for doing R&D work for Bose, that's basically what any mod'er is doing... applying their knowledge and the knowledge of the community to a product that has been produced by a manufacturer in order to improve the product's performance.
 
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I am not sure if the mini cup over the driver in the 25 is an attempt to improve the sound, though. The driver cup could just be for cost saving (simple outer cup and simple inner cup, instead of a single complex shape with a partition wall in the middle. I suppose it is more difficult to add the partition wall in a metal mold).

Is there any damping material under the 25's driver cup?
 
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