FX850 "j444 mod" version 2
This is a refinement of the earlier described
j444 mod. In addition to the original mod, modification of the back vent makes it even more effective.
Q: Why even mod the FX850? They're perfect as is / perfect after xyz hour of burn-in / perfect with the xyz cable.
A: Why even bother to read this post? By all means, stay with what you think is perfect.
Q: Ok, they're maybe a tiiiny bit warm / bassy on certain songs. I understand this mod reduces bass, but is it safe?
A: I obviously can't accept responsibility, so try it at your own risk. That said, I've been doing similar mods for quite a long time and never encountered an issue.
Q: Ok, and what if I end up not liking it?
A: This mod is completely reversible.
What this mod does:
To make it short, JVC's
drivers are the best dynamics I've heard to date, but in my book the overly bassy / warm tuning of their
IEMs doesn't bring out the best in them.
FX850 stock frequency response:
The j444 mod v2 attenuates bass and balances out the sound signature. It consists of modifications at the FX850's front and backside, which may be implemented separately or together. (Apart from bass, there's also a slight effect on treble, which has been left out in the following illustrations.)
Effect of front-mod:
Explanation: the front-mod adds a tiny amount of front leakage which avoids over-pressurization in the ear canal and reduces bass quantity. Attenuation is a bit stronger in deep bass than in mid/upper bass, resulting in a bass-lighter, but slightly more mid-bassy signature. Because of the leakage, isolation is slightly reduced.
Effect of back-mod:
Explanation: the back-mod restricts airflow through the back vent, resulting mainly in mid/upper bass attenuation. Deep bass remains unchanged and strong. Due to partial blocking of the back vent, isolation is slightly increased.
Combined effect of front and back-mod:
Explanation: the combination of front and back-mod yields the largest amount of bass attenuation and results in a significantly more balanced signature than stock.
(Disclaimer: these curves are just rough estimates based on listening tests.)
Step by step instructions for the front-mod:
(this is identical to j444 mod v1)
Step 1: Find some surplus tips made of thin silicone, e.g. Sony hybrid tips.
Step 2: Cut off a small stripe, about 1x7mm.
Step 3: This is the tricky part. Place the stripe alongside the nozzle, so that it protrudes about 1mm at the front end. Hold it carefully in place with your fingertip as you mount the silicone tip.
Step 4: Check the result - it should look like this from the outside.
Step 5: Check the result - it should look like this on the inside. Make sure that the stripe protrudes only a tiny bit at the edge of the nozzle, or else it will diffuse the sound.
Step by step instructions for the back-mod:
Step 1: Find a thin drinking straw of 5mm (or slightly less) diameter.
Step 2: Cut off two slices of 2-3mm width. Thinner slices will result in a more inconspicuous mod, but make it harder to undo.
Step 3: Carefully widen the slices until they fit the back vent. The thin plastic will thin out further in some spots, which is intended to retain airflow.
Step 4: Use your fingers (and an optional plastic pen) to gently push the slice into the vent. Do not use metal tools to avoid scratching the earpiece.
Step 5: The completed back-mod should look like this:
Step 6: Listen to a track with drums and/or bass. You should hear a pronounced bass attenuation vs. stock, but dynamics should still sound natural and lifelike.
If you feel that dynamics are badly lacking, chances are that the back vent is completely blocked. In that case, repeat the mod with a thinner / smaller drinking straw.
If you like the sound you're hearing, then you've successfully completed the "j444 mod v2" http://files.head-
fi.org/images/smilies/smile_phones.gif
Modding the FX1100:
The FX1100 are different from the FX850, in that they have even more mid/upper bass and warmth. Therefore an even larger restriction of airflow at the back vent is needed, in order to achieve a balanced sound signature.
While the front-mod is the same as for the FX850, you'll need to find a slightly larger straw for the back-mod, which will fit the vent without the need for widening. This means that Step 3 of the back-mod is not desired for the FX1100, but everything else is the same as for the FX850.
(left: straw for FX1100, right: straw for FX850)
Fully (back and front) modded FX850 and FX1100:
Ratings (provisional):
I've only been listening to the v2-modded FX850 and FX1100 for a few days, so this section may be subject to change.
In stock form, I'd take the FX850 over the FX1100 any day. The latter's overly warm and somewhat congested tuning is a bit of a mess imo. However, the FX1100 have slightly more potential than the FX850, because of smoother and more refined treble, a smidgen better mids presence and a tad tighter bass. Subjectively speaking, the j444 mod v2 is a huge improvement for
both phones, but it vaults the FX1100 from the undoubtedly worse stock phone even slightly ahead of the modded FX850. Therefore my personal ranking from better to worse reads as follows:
FX1100 (modded) > FX850 (modded) >> FX850 (stock) > FX1100 (stock)
Edit (1/4/15):
Modding the FX750:
Interestingly, the back-mod doesn't do much on them, which suggests that the stock FX750 have already more rear-damping with less airflow than the stock FX850 and FX1100. I recommend skipping the back-mod on the FX750 altogether.
However, the front-mod does a great job of attenuating bass impact, so I recommend performing just the front-mod on the FX750.
Listening to the modded FX750/850/1100 side by side, I feel like the FX850/1100's larger drivers sound noticeably better (more detailed / refined) overall. Their advantage in sound quality over the FX750 strikes me as more pronounced on the modded phones than when comparing all three IEMs in stock form.
Edit (1/10/15):
Other IEMs that benefit from the front-mod (imo): KEF M200, Zero Audio Carbo Tenore, IE8 (set bass dial to max!)
