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Post by videoguy on Oct 11, 2016 16:48:14 GMT
I have the Mark II's. Modded them using Frans's suggestions after checking BMF & other modding threads. Using Shure 840 pads & built up Frans's filter board. I am building a measurement rig after several other projects are finished. Just got the test disc files from HD Tracks & burned the disc. Results: You can feel & hear the 25hz tone clearly & the 31.5 hz tone nearly normal listening level; there is no bloat, just clean. The organ selection on the test disc appears to be very near 30hz. Overall the modded 50's sound fairly flat; just some slight peaks & dips across the spectrum. Properly modded T50RP Mk II are my main pair. Driving w a modified SCHA running on +-20vdc.
I am using some master tapes I from the mid to late 60's; when I did location master taping for several small record labels in the U.S. Back then there was much discussion in professional recording circles doubting the preservation on the high frequencies on tape over a long period of time. The masters sound as good as the day I recorded them, nearly 50 yrs. ago. Yes I am older but still have excellent hearing in my good ear.
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Rabbit
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Post by Rabbit on Oct 11, 2016 17:52:34 GMT
Is the treble ok? My biggest problem with mk2 minus a Kameleon was the lack of air up top.
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Post by videoguy on Nov 5, 2016 19:30:56 GMT
Yes Ian, the treble is very clean & clear. I never listen to them w/o the eq. filter. By the way I am using LME49860's in on the eq. board as I am running my SCHA at +-20vdc & these chips are rated +-22vdc. They are the same as LM4562 but for 22volt operation. My filter derives power from the ripple filter board in the SCHA via 1/4" stereo phone plug. It has taken the amplifier to a whole new level of performance. Am just testing AKHA amplifier & bringing it on line today.
It will be interesting to compare the two.
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Post by videoguy on Nov 8, 2016 20:03:07 GMT
Finally got the AKHA finished & on line. I immediately noticed more air around program material. Everything sounds super clean, no hint of any distortion & no background noise of any kind. The audio really shines w modified Fostex T50RP's. The cost of parts for this amp was well worth it. Together they make a winning combination.
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Rabbit
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Post by Rabbit on Nov 12, 2016 11:10:12 GMT
Glad it worked out for you Bill. That amp has been developed very carefully over quite a period of time, I think. Never heard one.
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Post by videoguy on Nov 12, 2016 22:40:39 GMT
0You really need to take a listen, it is dead quiet & very clean.
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Rabbit
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Post by Rabbit on Nov 12, 2016 22:53:47 GMT
Not many over here seems to have one Bill. It's a self build amp isn't it? I think it might have been Alex who designed it?
Don't really know much about it tbh.
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Post by Mr Trev on Nov 15, 2016 23:31:38 GMT
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solderdude
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Post by solderdude on Nov 16, 2016 10:08:20 GMT
Nope ... You would also have to buy the Alpha pads.
For a T50RP (mkII) + printed cups + alpha pads you could buy other headphones that perform better. Apart from that the T50RP drivers (IMHO) need EQ or a Kameleon to sound really good due to the upper treble roll-off adding to costs. Also, to adjust the bass port screw perfectly you would need to have access to a measurement rig. Adjusting bass L-R to match by ear will be quite difficult.
And I don't think a slightly larger and somewhat differently shaped cup and baffle will change the sound much. Internal padding (done correctly) will have a much bigger effect.
The idea is nice though. I reckon Dan is not selling Alphas that much any more. Focus is on the ETHER which are in a totally different league.
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solderdude
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Post by solderdude on Feb 7, 2017 21:10:45 GMT
Bought a set of T50RP mk3 because I was curious. Mine, however, has one driver that is performing poorly. My findings are found HERE on the websiteThe frequency response is shown below ( left, right) And to those wondering what the differences are between the 'old' T50RP and the new T50RP mk3 see the plot below. I think its an overall improvement except for the bass. Bass extension is not so good and the bass 'foundation' and dynamics of the bass has also not been an improvement. Need to fix the left driver first... have a look HERE to see what I mean. Too busy with a bunch of other projects now...
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Post by vampula on Feb 9, 2017 5:33:20 GMT
Bought a set of T50RP mk3 because I was curious. Mine, however, has one driver that is performing poorly. My findings are found HERE on the websiteThe frequency response is shown below ( left, right) And to those wondering what the differences are between the 'old' T50RP and the new T50RP mk3 see the plot below. I think its an overall improvement except for the bass. Bass extension is not so good and the bass 'foundation' and dynamics of the bass has also not been an improvement. Need to fix the left driver first... have a look HERE to see what I mean. Too busy with a bunch of other projects now... Did you try to close that holes in jack socket from inside of the cup(left one)? Those ventilate much, so its different demping in left and right driver. That may be the cause of faultiness...
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solderdude
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Post by solderdude on Feb 9, 2017 6:00:55 GMT
I only measured it and listened to it briefly. Had a modified HD688 with me as well and that one sounded much better.
Will probably remove the cable socket anyway because it is intermittend (with all the Fostex'es I heard and still own) The thought of the socket and the wire thru's has come to my mind.
Also the baffle purposely 'leaks' sound outwards (for the 100Hz-400Hz peak I reckon) which may also differ somehow.
Hope to find some time for it next month or so... am swamped with work atm. Will certainly look into the socket. Thanks for the tip.
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solderdude
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Post by solderdude on Feb 18, 2017 11:12:29 GMT
The distortion issue in the Left channel had to be looked into. On the website it was suggested that it may be caused by leakage of the (crappy) TRS socket. Indeed the socket has a substantial opening into the world around it. Not only through the hole but also around the connector itself. The plug, however, seals that hole almost completely off. The hole was sealed on the inside applying maleable eraser around it. This did not make any noticeable difference in distortion and also not in frequency response. Sealed connector, stock. Below some plots made during the investigation. Top left is the stock left channel. Top right is the stock right channel. As can be seen a substantial difference in distortion below 500Hz. Around 30Hz the left channel reaches almost 20% where the right channel reaches 2%. This was measured with 1kHz at around 90dB SPL. It looks like the driver has problems with larger amplitudes. To test this I remeasured at 80dB SPL (mid right plot). This showed the bass distortion is lowered to around 7%. I decided to give the driver hell and played an hour long extremely loud music with the bass dialed up a lot. As the driver can take a lot of power it was turned up till it started to distort. After an hour I remeasured. The distortion around 30Hz was only slightly down but the peaks around 200Hz, 300Hz and 4ooHz had come down. Based on the observations made I came to the conclusion that the driver cannot make larger swings and the membrane may be too tightly tensioned. Fortunately the Fostex drivers can easily be taken apart. I loosened all the screws and as the membrane was sort of stuck on the chassis I pried it free. Tightened the screws again and remeasured (picture bottm right). On the bottom left above the stock left driver for an easier comparison. Sure enough the distortion at 30Hz had dropped to slightly over 2% and is around the same as the right driver. Driver fixed... The frequency response altered somewhat though. stock versus fixed. 2dB more bass around 100Hz. The driver drops off a bit sooner as well though, maybe a seal issue ? The sound did not change in any obvious way despite the distortion being much lower and the bass being slightly higher. Next step is to add a little subbass and improve on the clarity and make the treble of better quality. This is done using a Kameleon filter. Below the stock T50RP (Right challel) and via the Kameleon. The bass response is much improved (+ 10dB at 20Hz). A bit more 'body' is added given the area between 100Hz and 300Hz is raised by about 2dB. The dip around 3kHz is improved by 2.5dB. This doesn't seem like it would be quite audible but it is. Clarity has improved noticeably. The treble 'peak' aound 9kHz is lowered a few dB as well. Treble extension has improved somewhat. The treble level is now more even between 4kHz and 18kHz which results in more 'air' and a more realsitic treble. Below L and R of the stock T50RP mk3 via Kameleon. The frequency response is more linear now. Good bass response, good clarity and better quality treble. More plots HERE
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Rabbit
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Post by Rabbit on Feb 18, 2017 11:51:41 GMT
Mine still have Shure 1540 pads on them. Some find them dark, but I'm ok with them. They are quite firm and push the cups slightly further away from the ears. Unfortunately not cheap though. I always think of them as 'aloe vera' pads but they're alcantara which is some kind of mix of velour and something else.......
I can even drive them with an IPod Touch, no amp, which is surprising. They have a good solid bass too.
I've been lucky with that left cup connection. Mine never played up.
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Rabbit
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Post by Rabbit on May 1, 2017 9:18:37 GMT
You know, revisiting these this morning with the alcantara pads - they are a fine headphone. The bass in particular is very punchy and they have a smooth sounding treble. Quite funny that going back to stock pads makes them relatively 'toppy' sounding. Much prefer the darker pads. I always meant to ask whether you were aware of the bass distortion or left/right imbalance when listening, Frans? I do wonder whether you got a duff headphone given the plug problem as well!! Mine never played up at all and I thought the issue might have been fixed. The bass in particular has this lovely 'springy' quality. Not particularly deep, but a rather nice quality to it. I guess that's the strength of planar drivers? I must admit, they have always made me want to listen to a higher quality planar headphone...... I have read that there were some issues with QC on the mk3. I find them absolutely fabulous at more lifelike volume with the Shure pads. For me, headphones need to have some bass punch in particular or else I feel that the 'drive' and 'guts' of the music is missing. good grief..... it looks like Shure have noticed a demand...... £41.50!!!!!! www.amazon.co.uk/dp/B00HXAV0UY/ref=sxbs_sr_ss_b1?pf_rd_m=A3P5ROKL5A1OLE&pf_rd_p=1302047307&pd_rd_wg=jsgLM&pf_rd_r=C67ZV2XMQMVPHVA7ZBYY&pf_rd_s=desktop-sx-bottom-slot&pf_rd_t=301&pd_rd_i=B00HXAV0UY&pd_rd_w=Y1FBm&pf_rd_i=Fostex&pd_rd_r=17MP5C1E9Z8YTN588B81&ie=UTF8&qid=1493633643&sr=1
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