To isolate whether this is truly a hardware or software problem..
Launch /Applications/Utilities/Audio MIDI Setup.app
If it doesn't already show, select Audio Devices from the window menu
Select your Speaker output on the left Sidebar; the tab on the right should show Output highlighted & Input greyed out
Bottom right, select Configure Speakers…
In the new dialog that drops down you should see 'front left' & 'front right' each with a drop menu beneath. The channels are likely just labelled 1 & 2.
- Swap the channels - set left to 2 & right to 1.
- Test with some audio playback.
If the right speaker still crackles - it's a hardware problem.
If the left speaker is now the one affected - it's a software problem.
Add a comment if it's software & we can test further.
If it's hardware, it's a trip to the Apple shop, I'm afraid.
Late Edit:
Because comments seem to be trying to break the laws of physics, let me explain further what is the most likely damage, & why it cannot be due to "magnetisation".
So, lets do a very quick 'physics 101' on the principles of loudspeakers.
The basic elements of a speaker are
- a housing to keep all of the following in place.
- a permanent magnet.
- a coil of electrical wire [usually copper] on a hollow cylinder, placed to intersect that magnet & free to move, within tolerance, inside the magnet.
- a cone of paper or plastic, fixed to the coil at one end & the housing at the other, used to project the sound from the coil into the room.
By definition, a permanent magnet is... permanent. Break it & both halves are still magnets. grind it to powder & every particle will still display the same characteristics. They are, for the purposes of this explanation, immutable.
As alternating current is passed through a coil of wire, it induces a magnetic field in the coil - positive & negative depending on the current flow, first one way then the other. As every schoolboy knows, opposite magnetic poles attract & similar poles repel.
The result of this is that the coil is forced first in one direction then the other in relation to the permanent magnet.
By having the coil connected to a larger cone, this transfers the movement into air pressure waves... sound.
The copper coil can never be permanently magnetised, because that can only happen [broadly] to ferrous metals - those which contain iron.
The most common ways to break this finely-balanced setup are :-
Stressing the join where the cone meets the housing - causing softening &/or eventual fracture at the join. This will make the speakers buzz at high volumes.
Overheating the coil until it permanently distorts. This will cause distortion at almost all volume levels.
Both of the above are usually caused by running the volume too loud for tolerance.
Over-compressed audio [Google 'The Loudness War' for background] or sound applications designed to 'make it all louder' (Boom, I'm looking right at you:/ ) will contribute to early failure.
A third, often overlooked cause is moisture. Paper cones & coil substrates don't like moisture.. whether it's just continuous high humidity or inelegantly-applied soda.
The tolerances between magnet & coil are measured in microns. Distort the coil or the cone & your speaker is as good as dead.
With an analog amplifier, running at low battery power would contribute by adding distortion to the signal at lower volumes. Computers don't really suffer from this, as their batteries are designed to give close to full output until recharge.
Looks like the underlying problem was that the Cirrus 4208 driver installer failed to install any drivers. Not sure what initial problem stopped the driver working but once the driver was uninstalled the bootcamp support software wasn't able to install a replacement driver.
The fix was to manually unpack the Cirrus 4208 driver installer .exe (included in the the bootcamp support software) using 7zip and then update the high definition audio device in device manager by browsing to the folder containing the unpacked Cirrus 4208 installer.
Some posts on the web suggested that it could be fixed by running the Cirrus 4206 driver installer before the running the Cirrus 4208 driver installer but that didn't fix it for me.
Best Answer
Late edit:
Since writing this, Rogue Amoeba have released a simpler & cheaper app specifically to tailor output rather than provide full internal audio routing & recording - SoundSource. You can set up your EQ or whatever as a global or on a per-app basis, making it very flexible.
I wrote this before checking all the proposed apps in the OP; my issue with these kind of things usually is that I tend to avoid the "we can do it all for you" apps, like Boom & Bongiovi; because I always think, "How can you do all that for me? You can't hear my speakers!".
eqMac2 does look like a simpler version of what I'm already doing on the first machine example below... for free. You still need ears, or an analyser, but the investment could become 'merely time' rather than actual cost.
Potentially what you could do if you have access to a smart phone is download a free Spectrum Analyser & find a white noise sample or generator online* then use the EQ to flatten the perceived EQ curve as the phone hears it.
You could do this with Soundflower & a graphic EQ too, or potentially with eqMac2 - for free.
There's a slicker solution than Soundflower, but it's far from free - Audio Hijack - which I use to tame the audio on several machines here, for slightly different purposes.
I get the feeling it won't be what you're looking for, but it's quick enough to throw in here & see if any future Googlers might like it. I do seem to come across as a one-man campaign for this app, but it's just that it's the best I've found for many similar purposes. I have no affiliation whatsoever.
If someone can find a free equivalent, I'm all ears - quite literally ;)
One cool thing, though is you can set timers for it - so to get it to be 'always on' I set it for 23h 59m of every day & let that spare minute be when I'm bound to be asleep.
On one machine, I use it to compensate for cheap external speakers with an odd EQ curve. I simply send all audio through it to flatten the perceived EQ curve.
On the other machine, I use it to compensate for the very high dynamic range whilst watching movies - which are piped through to my powerful 5.1 system, capable of offending the most tolerant neighbour. I use it to simply keep things within a more acceptable range to suit me & my neighbours...
Both these setups just use Apple's built-in AU plugins.
Unfortunately, there is no automatic setting for either of these setups. I do it by ear - but I'm a pro sound engineer & I trust my ears to get it at least close enough to be acceptable to any listener.
*No affiliation, just one I've used before.