Dave
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Post by Dave on Dec 3, 2013 13:33:50 GMT
Hi Guys but particularly Frans, I have just had this thread pointed out to me and wondered if it had any merit in your opinion(s). I am happy doing mechanical mods like adding stuffing or cutting 'windows' in thin sheets of damping material etc. but would not even consider putting a soldering iron anywhere near the insides of the cups. Any thoughts? TIA, Dave.
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solderdude
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Post by solderdude on Dec 3, 2013 15:07:13 GMT
Well I just received the K551 and am going to mod those. They do not differ that much from K550 so you may want to 'hitch along' with that. There is also going to be a passive filter to get rid of the sibilance (designed it already but will have to tweak it most likely) It will be similar to the first HD681 filters (passive filters) but of course different values.
For this the soldering iron is needed but such a filter could be external (in a small extension cord)
I only plan to do some mechanical mods in preventing reflections as the bass seems to be O.K
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Dave
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Post by Dave on Dec 3, 2013 15:28:35 GMT
Hi Frans, I would be more than happy to 'hitch along' with you providing it is within my capabilities - anything that is not within my capabilities I would be willing to pay you if you chose to put together 2 active filters and ship one on to me. TIA and thanks for your response, Dave.
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solderdude
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Post by solderdude on Dec 3, 2013 15:59:04 GMT
the filters will be passive for the K551, I reckon the K550 filter will be very similar
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Rabbit
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Post by Rabbit on Dec 3, 2013 16:36:18 GMT
Frans, have you measured the fr of the 551 yet? Imo, you are right, the bass is at about the right amount and the treble is harsh in quality. It could well be some ringing going on in there - similar to what I heard on k701's.
Other than that, they are a very good headphone imo.
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solderdude
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Post by solderdude on Dec 3, 2013 20:54:47 GMT
Haven't gotten around to it (measuring) Only did some listening and it is not a bad headphone.
I have the feeling something is 'off' in the mids (slightly) and getting proper seal is not easy. The cups can swivel but this is very tight so you have to 'form' it. Once it is on the seal is good. mic cable is very low in microphonics ! There is a slight sharp 'edge' which makes distortion (when in the recording) much accentuated. Good recordings sound good though.
No up to filtered T50RP quality and in initial impressions (no side by side) I prefer the filtered/padded DT1350 over it as it has better bass and no sharp edge and sounds more 'real'. Still, stock a very good headphone and isolation is also above average but not super duper. Very comfortable despite the pleather pads (very soft !)
When I have measured and corrected it/tweaked it I will start a thread. Might even make a pdf if I find it worthwhile.
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solderdude
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Post by solderdude on Jan 25, 2014 16:03:16 GMT
Low and behold ... the measurements of the K550: and compared to a stock K551: Time for modifications. They measure more similar than different so these headphones should be totally transformable as well. The K550 does have slightly less treble energy around 10kHz.
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Rabbit
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Post by Rabbit on Jan 25, 2014 17:54:02 GMT
That's really good news Frans. I rarely use the k550 because it's not long before the top irritates me.
The K551 must be quite jangly then!! I found the K550 too much and Dave found the very same when I sent him a spare one that I had. I thought he might have found it ok with the hearing but he noticed it straight away as well.
The mods might make them more usable for me!!
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solderdude
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Post by solderdude on Jan 26, 2014 21:24:15 GMT
Modifications done... results below: The 'fun' part of this modification is the highs are always damped but the lows/warmth can be adjusted/controled by changing the output resistance of the amplifier. below what happens to the plot when 0 Ohm or 120 Ohm is selected. Of course a value inbetween will have an effect inbetween those lines. CSD (Waterfall plot) of the 'improved' version. right channel, compare to the one above.
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Rabbit
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Post by Rabbit on Jan 26, 2014 21:50:27 GMT
Wow, that was quick, Frans. What an improvement!! It's a lot flatter than it was for sure with that treble peak ironed out.
Is it now similar to the K551? Or are there differences? Looks similar on graphs.
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solderdude
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Post by solderdude on Jan 26, 2014 21:55:34 GMT
They sound exactly the same as my modified K551's. Impossible to tell them apart other than by cable and colour. Been listening to it for the last hour...
Will try to ship the Koss and AKG on Wednesday.
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Post by c61746961 on Jan 26, 2014 22:08:25 GMT
Great! Now I want a pair...
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Rabbit
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Post by Rabbit on Jan 26, 2014 22:30:58 GMT
They sound exactly the same as my modified K551's. Impossible to tell them apart other than by cable and colour. Been listening to it for the last hour... Will try to ship the Koss and AKG on Wednesday. OK Frans. Many, many thanks, yet again. Don't go running around to get it to the post. It takes a long time to get back over the North Sea so I'm ready for a wait!! The T40 is quite amazing so if these are now close, I may have an ideal closed headphone that isn't 'quacky' or boomy with no stinging treble. IE: I'll be able to actually use it for serious listening at last!!!!
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Rabbit
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Post by Rabbit on Jan 27, 2014 20:41:02 GMT
Great! Now I want a pair... I've been blessed by Fran's mods before and from what he describes in the K551 after his mods, I'm really looking forward to this one since it's really close to the 551. I have a modded T40 that was done via measurements on his rig so there was no guesswork involved and no haphazard placing of felt or whatever, and I tell you, the results are unbelievably good. The T40 and T50 are my 'serious' listening headphones as a result. So, I'm looking forward to the K550 a great deal as well as a Portapro that I know is real!!! (Although it looks as though my old one actually was real) The guy's a blinkin' genius and we are very lucky here on DIYAH. None of 'yer bias and bullshite.' Top notch results that are verified with no guesswork involved. Something that you can rely on without the interference of skewed opinions or guesswork!!!
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solderdude
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Post by solderdude on Jan 27, 2014 22:23:59 GMT
Dave, The modifications are described here: www.mediafire.com/view/pzbaqy8nuek1kkq/AKG%20K551%20modifications.pdfthe 3mm thick felt I can provide. You will also need some damping material (self-adhesive felt) on the inside of the cups and to solder some components inside the cups. That last part is tricky... Soldering is mandatory to achieve these results as is having the right materials.
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