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Post by c61746961 on Feb 2, 2016 2:55:52 GMT
Haven't swapped the drivers as I don't want to re-solder right now, I'm trying more things. The FR is very dependent on pressurization of the cup; if you don't install the baffle foams the bass goes down a good ~6 dB and the lower treble dips as well.
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Post by c61746961 on Feb 2, 2016 4:33:33 GMT
So yeah, there's a pretty difficult to control leak in the left cup, and the right cup was practically sealed so I had to make one vent (1mm hole on the bottom of the cup where the connector is on the left side), here's where I'm at: Now it's listenable. Dunno how it got worse after you measured it, Frans, but it did, it was very wonky sounding. The cup seal is very finicky and the FR is altered dramatically as a result, which is probably the culprit of all the reports of channel imbalance.
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solderdude
Administrator
measureutternutter
Posts: 4,882
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Post by solderdude on Feb 2, 2016 6:12:40 GMT
Looks much better now.
Good idea ... if you cannot seal it create an equal seal on both sides !
If you can post a picture of what you found that would be awesome and beneficial to owners.
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Post by c61746961 on Feb 3, 2016 0:37:47 GMT
I'm gonna try to produce better matching and lessen the dip @ 5 KHz, then I'll make a rundown.
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Post by elmirador on Jun 21, 2016 10:15:02 GMT
Hey guys, new on this forum.
I recently bought DT250-250ohm and found out it has the infamous left-side-is-bassier problem. I bought my pair oversea so repair/replace may not be a option.
After googling awhile, asking someone over head-fi, even sent a mail to beyerdynamic (no response of course) it finally leads me here.
Sorry to bring this post back but c61746961 I'm wondering is the 1mm hole you're referring actually where the cable screw goes?
Another thing I found is if your move the plastic baffle plate / foam altogether, the imbalance problem is gone, so I'm wondering if that could be a way to fix this too...?
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solderdude
Administrator
measureutternutter
Posts: 4,882
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Post by solderdude on Jun 21, 2016 13:16:40 GMT
From what I understood from c61746961 was that one cup has more leakage than the other. Closing the leakage is difficult to do so he created about 'equal leakage' by drilling a small hole in the 'most closed' cup effectively making leakage about the same and restoring channel balance. Every other way to increase leakage (so both cups have about similar) should work as well. As long as the inside of the cups can 'leak' to the outside.
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Post by c61746961 on Jun 21, 2016 15:10:09 GMT
The driver is QUITE finnicky on pressurization, I tried many things with varying results without resorting to permanent cup mods, keep in mind that this pair developed an 8dB mismatch at the lower frequencies. I couldn't bring the thing together without the extra venting. I have another wonky pair coming and will try to document the whole process.
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Post by elmirador on Jun 22, 2016 0:58:24 GMT
Thanks for the response! Very much appreciated! The driver is QUITE finnicky on pressurization, I tried many things with varying results without resorting to permanent cup mods, keep in mind that this pair developed an 8dB mismatch at the lower frequencies. I couldn't bring the thing together without the extra venting. I have another wonky pair coming and will try to document the whole process. Yes I think you're right, the pressurization is another key factor to this problem. I found my pair doesn't have trouble with leakage, the weird behavior is due to the wrong pressurization. There's four little pillar-like buckle on the corners of the plastic baffle, if I push them all into the cup, the problem is here, but once I pull out one of them (don't push it all into the hole on the cup), the left-right channel is almost balanced. I think there's still a slight difference between 500~800Hz though, leans to the right channel more while sweeping through the frequency, but it's almost inaudible in a normal music replay. Sadly I don't have a measurement gear for testing so I'm saying this all by my ear lol
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Post by c61746961 on Jun 22, 2016 15:49:09 GMT
I have received the other pair and it exhibits the same problem as the first one; the venting / bass reflex configuration of the right channel is misbehaving. There are several potential fixes but I'm working on a solution (less involved than the first one) that will offer the best channel matching. So far I can advise you to try making gasket ring from ~1mm thick felt that will put a better seal between the baffle and the earpad assembly on the right channel, there's a depression along the inner edge of the earpad mounting piece where the foam is supposed to be secured, you can use this as a reference for the ring I mention; you have to enhance the seal between the earpad and baffle, but not make a complete seal.
Once I'm satisfied with the fix I will publish it.
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Post by elmirador on Jun 23, 2016 6:07:40 GMT
I have received the other pair and it exhibits the same problem as the first one; the venting / bass reflex configuration of the right channel is misbehaving. There are several potential fixes but I'm working on a solution (less involved than the first one) that will offer the best channel matching. So far I can advise you to try making gasket ring from ~1mm thick felt that will put a better seal between the baffle and the earpad assembly on the right channel, there's a depression along the inner edge of the earpad mounting piece where the foam is supposed to be secured, you can use this as a reference for the ring I mention; you have to enhance the seal between the earpad and baffle, but not make a complete seal. Once I'm satisfied with the fix I will publish it. Okay I'll give it a try! Thanks again for all the effort you put into! Looking forwarding to your solution! I somehow found this annoying problem actually would be a good opportunity for getting into modding lol
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Post by c61746961 on Jun 23, 2016 17:26:34 GMT
BTW, these can be turned into bass monsters just by creating a better seal around the driver oppening on the baffle against the earpad assembly, funny just how sensitive the driver is to pressurization/coupling/whatever.
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Post by c61746961 on Jun 29, 2016 2:05:03 GMT
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Post by elmirador on Jun 29, 2016 2:41:04 GMT
BTW, these can be turned into bass monsters just by creating a better seal around the driver oppening on the baffle against the earpad assembly, funny just how sensitive the driver is to pressurization/coupling/whatever. Yeah maybe that's why there are so many problems around this cup because it's driver is just too sensitive and the factory can't control that precise on this kind of things... Wow, thanks man! Gotta give a try!
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Post by c61746961 on Jun 29, 2016 2:59:02 GMT
Feel free to shoot me any questions.
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Post by elmirador on Jun 29, 2016 4:33:06 GMT
c61746961 So I tried out the first method with sealing the cable with foam and clear tape, that worked very well, the bass on left channel is sounding at normal level. However I still feeling there's a little leaning on the left side (left side volume is a little bit louder than right sid e, and it could be adjusted by ear after listening for a while), haven't tried sealing ring though because I haven't foam big enough to create the ring, but I'd really like to know how the sealing ring is affecting the sound after all.
EDIT: Bought the microfiber cloth, waiting for the delivery.
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