Fostex TH500RP

Foreword

 
I bought these headphones in February this year from fellow head-fier @dieslow, and got them after about three weeks, courtesy of Swiss customs. After reading Steve Guttenberg's rave review on Cnet, I was all too excited to try them out on my new iDSD BL. Boy was I disappointed! They sounded dull, veiled, flat to the point that my Fidelio X2 (a VERY good heaphone, btw, especially considering the price) was miles ahead of them in terms of everything, really. So I decided to put them on the chopping block, pretty much for the same price I had paid for them, and recover the investment. No such luck. But really? More of that at the very end of this review.
 
Enter Spirit Labs. This small but very professional Italian outfit is run by founder Andrea Ricci, mainly intent on heavily modding Grados and Beyerdynamics. I bumped into his Facebook home page while I was trying to get rid of the TH500RP and saw in a corner of the page the name "Fostex" among the brands of cans Spirit Labs would mod, so I hit them up and explained what was wrong with my headphones, imo. Andrea listened carefully, then explained to me what he thought could be done. It didn't take much to convince me at that point, also because the price he quoted for the whole job, new premium cable included, was a very affordable EUR 140. So I shipped them out. What follows next is your typical ugly duckling story.
 

Pre-Spirit Labs mods

 
I got the headphones in really excellent conditions, just as described by @dieslow. Build quality and presentation are really outstanding. 
 

 
Soundwise: overflowing and uncontrolled bass, mids not well defined and "foggy", rolled-off treble, meh soundstage, needed to be played really loud to get something out of them.
 

The Spirit Lab mods

 
Before the mods:
 

 
   The famous RP drive
 

 
 

The mods

 
 

Basic design change, from open to closed back.                    
Removal of the mat covering the drive. Total internal recabling 
Removal of the mid paper layer behind the drive, baffle/driver armoring
 

 
Final product with new cable.
 

The final sound results

 
Bass:
 
Powerful, tight and detailed. Clear and rhythmic mid-bass.
 
Mid-range:
 
Open and transparent, a major improvement over the pre-mod version! Can be played at low volumes and still retain clarity and detail.
 
Mid-highs and highs:
 
Crisp and well defined, without ever becoming sibilant. 
 
Soundstage: 
 
As odd as it may sound, there is a much better soundstage now, after being transformed into a closed design, than there was before as an open design. I believe this may be due to the vast improvement in transparency and clarity.
 
Power:
 
Before the mods, I really needed to drive them hard with my iDSD BL in full turbo mode, and the result was still questionable to say the least. Now, the BL drives them effortlessly (in turbo mode), but I have achieved amazing results in terms of their ability to play real loud or at low volume by using the headphone stage of an icon of the '80s, the Audiometric A10P/Adcom GFP1 semi-pro preamp, which to this day I consider one of the best preamps, bar none. However, I'm not even thinking of using them on the go, the BL being the maximum portability you can get with these cans.
 

Conclusions

So, thanks to these rather extensive but inexpensive mods (take a look at the cost of the Lawton mods to see what I'm talking about, and they are d.i.y!) the ugly duckling has become and elegant and powerful swan. Boy am I happy I didn't get to sell these cans when I wanted to! If I had, or if they had been sounding reasonably well, even though not amazing, I would never had them go through the Spirit Labs treatment and therefore I would not nearly enjoy them as I am enjoying them now. Yes, the cable is a little heavy, and my ears get warm after some time, but I still can't take them off after several hours!
I am therefore renaming my headphones the Spirit Labs SL1000AR. Thank you Andrea!

Edited 8/23/18:

I have 150 hours active listening and another 150 passive/occasional on these.

Equipment: see sig

Low bass: reticent, lacking drive when unmodified.

Mid/upper bass: flabby, not much impact either.

Highs: starts to drop at 7-8k, clearly down at 12k (2-3 db), 14k just not there

Soundstage: can be wide, and change size depending on recording, but never gets tall (an issue with this technology)

These remind me Maggie SMG's. If you never listened to live or other better equipment you might conclude that they are very good indeed.

IMO, the Senn HD-600's, MD 4xx, and by a massive margin the HFM HE-500 are better. I mean really, what do the Fostex do better? A little fuzzy romantic gauze in the mids?

I have gotten nowhere with pad changes. The stock are the best. Making them balanced didn't help much.

However the modifications I've done have changed things. I cut out the plastic grid with the mesh, and added batting between the driver and the outer mesh (very. subtle changes), but the big one is putting white tack on the outer screens. Too much, and the they start to sound boomy and ridiculous. But with 8 pieces cut into 1/4" x 1/2" pieces and oriented somewhat around the middle with spacing the bass is easily better than the HD-600's (quantity but also maintaining a sense of being lithe and quick) Might be a bit less energy then the MD 4xx, but I'd say quicker. I've tried about 15 layouts of the tack before I found this combo. I'd like to test it to see if I can improve it.

I have never been irritated by these, but, the politeness comes from lack of detail and high end that falls off at 9k and is essentially done by 13k. A stronger bass foundation helps the treble sound a bit more pronounced. at times, but, its just sense of more, it still lacks air, sparkle, and subtle definitions.

They are now on my keeper list which is a step up for me.

This is an update to the review I wrote shortly after purchasing the TH500RP. By now I have these cans for over a year and I listen about 25% of the time with them (10% EL8 Open and the reminder LCD2 and LCDX). Mine has serial #419
 

Besides the TH500, I own Audeze EL8, LCD2.2, LCD-X, TH900, HD650 and a Bayer DT1350 and the Oppo PM3
 
In short I would consider the following order of quality
 
PM3 < TH500 < LCD-X.
 
All of these three cans are quite neutral and you will see the respective differences when you compare them directly. 
My impression is actually limited to the type of music I am listening to - mostly classical music and opera. Having said this, I prefer a quite balanced sound, which does not overstate, nor understate the different part of the spectrum.  All the the can above (with the exception of possibly LCD2 / HD 650) fulfil this requirement to bigger or lesser degree. I am going to discuss the following three cans: PM3, TH500, LCD-X.
 
As said all of them are in mu view quite neutral and have a similar sound signature. The warmest representation of the three is the PM3 and the most neutral possibly the LCD-X (had difficulties to make a pick between TH500 and LCD-X). This means that the TH500 is in my eyes really good. [A good indicator of a headphone is to just play your preferred piece and listen to it - you will immediately find outliers - both positive and negative.] From the three can the TH500 surprised me most positively. You would expect a very good sound from a LCD-X; the TH500 is almost there.
 
Now where are the differences between the three.
 
a) The resolution of both TH500 and LCD-X is higher than with Oppo PM3 (on a stand-allone basis difficult to judge - it becomes only apparent when directly comparing them)
b) The bass of the PM3 is possibly overstated - but not as precise as LCD-X
c) The bass of the TH500 is precise as the LCD-X up to a certain degree. If you push it too hard (-say the thunderstorm in Handels Rinaldo), you will see that the bigger transductors of the LCD-X will outperform. I think this is a not too big sin, since a lot of dynamic cans have the same flaw and you do not listen every day to music massive amounts of energy in the 10 -25 Hz spectrum.
 
d) The mids are very good for all three cans - TH500 and LCD-X winning in terms of precision over PM3
 
e) Highs: Same as d), here the TH500 has 'slightly' less energy. (but by far more than the LCD2 for example)
 
Conclusion:
I like the TH500 quite a lot and do not really understand the negative comments I have read in the thread before. If you like either PM3 or LCD-X you will almost certainly enjoy the TH500. In particular the price seems to be very competitive. You get about 95% (say) of the performance of the LCD-X for a fraction of its price. With respect to PM3 there is quite an improvement in quality (however PM3 is closed and TH500 is open)
 
Now where is the dark side?
 
a) The TH500 needs considerable amount of power. The sensitivity is in the order of the one of LCD2 and you almost certainly do not want to run it via your iPhone. It works very well with Chord's Hugo (TH500: c93dB per 1mW, PM3: c102dB per 1mW, LCD-X: c103dB per 1mW) 
 
b) The weight of the can is something personal. The TH500 is quite light (as the TH900). So it is not that heavy as the LCD-X.
 
Comment on sources:
 
I have used the cans with Chord Mojo, Hugo and AK 240 and the TH500 plays very well with all of them. Given the higher power available from Hugo the latter one outperforms vs the others, but AK240 works well (sound level at about 124 / 150 vs TH900 with 90/150). This might indicate that TH500 can not play excessively loud with AK 240.
 
In terms of sound quality the order is as follows AK240 < Mojo < Hugo. Having said this I almost ever use AK 240 stand alone when travelling but use mainly Hugo when working at the Mac.