EEVblog #1073 - MORE KRK Rokit Black Gunk Speaker Repair - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: April 11, 2018, 06:44:42 am
content: Fixing another two Gen 2 KRK Rokit 6 near field monitor speakers with the black gunk of death and failed capacitors.How wide spread is this problem?

author: Halcyon
author_rank: Unknown
timestamp: April 11, 2018, 09:50:22 am
content: Thanks for the video Dave.I shot an e-mail to KRK (AKA "Gibson Brands") and this was their rather generic response:Our distributors set terms for warranty in their respective countries. Any dispute would need to be made through them. Please contact our distributor from the link below.http://www.krksys.com/worldwide-sales.htmlBest regards,John NapierCustomer ServiceGibson Brands, Inc.1-800-4GIBSONservice@gibson.comwww.gibson.comI've replied reminding them about Australian Consumer Law and their obligations (regardless of the fact they are in the USA, they manufacture and sell products in Australia, so they too are bound by the same laws as Australian manufacturers/companies). We'll see what kind of response that gets me (if anything).It's a bit piss poor in my opinion. I get that they aren't professional or "industry standard" monitors and no one's expecting them to last or perform anywhere near the likes of Dynaudio etc... but at least own up to the problem and offer some kind of token gesture to the poor consumers who bought these things, even if it's a free pair of their smallest speakers. As it stands, I'll never even consider buying KRK's again, I'd rather go down to the local Hi-Fi store and buy a cheap Yamaha or Sony amplifier/decoder and their standard crappy bookshelf speakers.Furthermore, this is straight fromKRK's website:At KRK we take design and performance very seriously. If it's not right...it won't go to market...period! That is the kind dedication we pour into every product. And we do that because we know our customers have come to trust us for that. We know they are dedicated to their music and the products they use deserve the same design dedication. This "design first" mentality is what the company was founded on and has helped KRK become an industry leader in this highly specialized market.Your move KRK / Gibson Brands.

author: madires
author_rank: Super Contributor
timestamp: April 11, 2018, 10:23:28 am
content: I fully agree! When a company treats their customers like this when they screwed up big time they don't deserve any customers at all. Since they have changed the selastic in the next generation they clearly know of the problem.

author: Brumby
author_rank: Unknown
timestamp: April 11, 2018, 11:06:07 am
content: They've talked the talk - now they need to walk the walk.

author: EEVblog
author_rank: Unknown
timestamp: April 11, 2018, 11:16:02 am
content: Quote from: Halcyon on April 11, 2018, 09:50:22 am

author: MT
author_rank: Super Contributor
timestamp: April 11, 2018, 02:59:28 pm
content: Quote from: madires on April 11, 2018, 10:23:28 amMost likely, and i would like to know the manufacturer of the hydroscopin gunk! There was talk about conductinggunk in the first KRK repair thread, ShinEtsu for example have a range of various conductive/resestive gunks like KE-3491https://www.shinetsusilicone-global.com/products/function/conduct.shtmlhttps://www.shinetsusilicone-global.com/products/type/rubb_comp/index.shtml

author: T.Balázs
author_rank: Newbie
timestamp: April 11, 2018, 04:22:01 pm
content: I can't believe how dogy those amps are.I had built my own studio like 10 years ago and considered to buy KRK monitors. Actually looks like some capable speakers but those amps are horrible. Would be a nice project to scrape the amps all together and just replace them with off the shelf modules. Cant be too hard to measure the response of the active filters and replicate it with ready-made op-amp boards. Whack in some nice chip amps or even cheap Class D amp modules from China and it will be a capable little setup.I would also enjoy a tweeter autopsy video to see what kind of coil setup it has. A core made of Kapton may survive the impact of bottoming out in the gap and its thermal insulation promotes burning to open circuit without further notice. An aluminum core must be permanently damaged and scrubbing the gap wall. I cant tell for sure but the first one sounded like scrubbing.

author: Bud
author_rank: Super Contributor
timestamp: April 11, 2018, 04:32:02 pm
content: Quote from: EEVblog on April 11, 2018, 11:16:02 amWhen someone puts a string of dots between words it means the person is unsure / in doubt.

author: PChi
author_rank: Frequent Contributor
timestamp: April 11, 2018, 08:23:39 pm
content: Why did Rokit put the heatsink inside the case instead of on the back panel? No wonder one of the capacitors bulged.

author: EEVblog
author_rank: Unknown
timestamp: April 11, 2018, 10:04:24 pm
content: Quote from: PChi on April 11, 2018, 08:23:39 pmThe heatsink is connected to the metal back panel using thermal compound and a silpad. Albeit a small surface area.

author: EEVblog
author_rank: Unknown
timestamp: April 12, 2018, 01:25:41 am
content: Big debate in the video comments about the best monitor speaker in the low cost range.Most people say Yamaha HS5/7 or JBL LSR305I found this very well done comparisonTo me the JBL's do sound better for music, but for voice mixing, don't you want boring and flat like the Yamaha?

author: Cerebus
author_rank: Super Contributor
timestamp: April 12, 2018, 01:54:37 am
content: That first speaker where the woofer suddenly came to life - I reckon that it had simply mechanically stuck after that big DC excursion and you touching the cone was enough to move one edge and unhook it from whatever it had caught up against.

author: Lightages
author_rank: Unknown
timestamp: April 12, 2018, 02:13:49 am
content: Quote from: EEVblog on April 12, 2018, 01:25:41 amI wouldn't put too much weight on these comparisons. There is no information on the actual testing procedure or set up. Take it with a big grain of salt. Instead have a look at this now dead company's testing:https://www.youtube.com/user/SonicSenseProAudioand their comparison of the JBLs

author: Lightages
author_rank: Unknown
timestamp: April 12, 2018, 02:23:12 am
content: Having listened to Rokits in the flesh, the comparisons on line, I never liked them. Now that I see their way of doing business they will never get my money.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: April 12, 2018, 08:11:39 am
content: Word of advice; when testing any audio amp with a fault, NEVER use directly connected speakers. If the amp puts DC on the speakers, they will be, as the eponymous TV show said,Destroyed in Seconds.Instead, for solid state amps it is generally quite OK to test with no load. Valve (vacuum tube) amps should not be run unloaded, but then they would never put DC on the output due to being transformer coupled.If doing any volume of amplifier repair work, what you really need is a test load, or pair of test loads, consisting of a suitable power resistor, plus a second resistor of higher value (100R or so) with a monitor speaker in series. That way the monitor speaker samples a fraction of the output, and if full DC appears on the output you may lose the test resistors but that's a lot less costly than losing the testbench speakers.RS metalclad power resistors on a decent heatsink with a thermal cutout are ideal. Another option is a pair of old fashioned power rheostats, if you can find a pair of 10 ohms or so. (The rheostat is neat as the wiper can be used as a monitor volume control.)Bear in mind that an amp fault may make the test resistors very hot, so beware of fire or burning yourself. Thermal cutout advised for this reason.LEDs to indicate the presence of DC or a relay to disconnect the amp automatically might be a useful addition, but the basic two-resistor per channel and cutout arrangement is perfectly good.IMHO in the tests, the Yamahas are by far the best (No surprise there) The JBLs are excellent if a little bassy, but at least the bass is clean. The Rokits are dull-sounding with a serious bass boom. (You can't tell one bass note from another)In a studio you don't want over-strong bass anyway because that would predispose you to mixing 'thin' tracks. You want something that tells you exactly how much bass and treble there is, no more no less. The Yamahas do that.

author: Halcyon
author_rank: Unknown
timestamp: April 12, 2018, 10:01:01 am
content: Excellent post Ian! Thanks.

author: madires
author_rank: Super Contributor
timestamp: April 12, 2018, 10:27:49 am
content: Quote from: EEVblog on April 12, 2018, 01:25:41 amIMHO, the purpose of monitor speakers is to get an idea about how your audio sounds on a typical home stereo system (inexpensive, nothing fancy), or on PC/TV speakers in case you like to optimize the audio for YouTube videos.

author: Brumby
author_rank: Unknown
timestamp: April 12, 2018, 02:01:02 pm
content: Quote from: madires on April 12, 2018, 10:27:49 amI disagree. Monitor speakers should present the sound as faithfully to the electronic signal as possible.There is no such thing as a "typical" home stereo system these days - especially when many of them come with a dozen EQ presets that bend the sound in all manner of contortions.Let the published work be as neutral as possible - the consumer is going to colour it to their preference anyway.

author: Fungus
author_rank: Super Contributor
timestamp: April 12, 2018, 02:19:32 pm
content: Quote from: Brumby on April 12, 2018, 02:01:02 pmI agree 100% with your disagreement.If you want to hear how your audio sounds on a "typical home stereo system" then buy a typical home stereo system. Monitors should be as transparent as possible.

author: Cerebus
author_rank: Super Contributor
timestamp: April 12, 2018, 02:26:23 pm
content: You're both right. Proper studio monitors ought to be as transparent, and have as few faults as possible.Nearfieldmonitors, like these, ought to represent a 'typical' system, and one ought to have 'proper' monitors for the majority of your work and nearfield monitors to check that the result you're getting is going to sound OK on less than stellar equipment.The problem is that a lot of people have seen brand X perched on the ends of the back of the mixing desk in a studio and assumed that brand X are very good, good enough to be used in the studio. So brand X get a following when in practice brand X was chosen by the studio not for being good but because brand X are somewhat crap, but not too crap.Note that nearfield monitors are not to be confused with small high quality monitors used as the sole source of reference in places like radio production studios, where the likes of the fabled Rogers LS3/5a will be found doing all the work. These get chosen because radio production studios seem to be universally built into broom cupboards and there just physically isn't space for a decent pair of monitors, so compromises have to be made.

author: rrinker
author_rank: Super Contributor
timestamp: April 12, 2018, 05:41:16 pm
content: Quote from: Halcyon on April 11, 2018, 09:50:22 amSee, it says they take DESIGN and PERFORMANCE seriously. Says nothing BUILD, hence the Huan Hung Lo caps and the black gunk of death.

author: Halcyon
author_rank: Unknown
timestamp: April 13, 2018, 04:31:20 am
content: No reply yet to my follow-up e-mail. Previously they responded within 24 hours. Seems like KRK / Gibson Brands just want to block their ears and pretend the problem doesn't exist.SinceJandsis the only listed distributor in Australia, maybe I'll hit them up for a comment.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 13, 2018, 04:38:19 am
content: Few engineering-related videos, in my experience, can take significant advantage of more than reasonably good audio hardware on the playback side - it just has to sound good enough for the speech to be easily understandable and even a $5 Bluetooth speaker will be enough. In fact, the only engineering-related shows I watch that call for good audio playback often are Fran Blanche and MsMadLemon because they often do something music related.Video is a different story, though. A large percentage do take good advantage of the 1080p resolution that's the most common nowadays. And quite a few are best enjoyed upscaled to 4K full screen.

author: SilverSolder
author_rank: Super Contributor
timestamp: April 15, 2018, 12:37:13 am
content: What is the "right" compound to use for this kind of application (i.e. a good replacement of the "hygroscopic gunk of death")?

author: madires
author_rank: Super Contributor
timestamp: April 15, 2018, 10:15:03 am
content: Electronic grade RTV silicone for example.

author: Fungus
author_rank: Super Contributor
timestamp: April 15, 2018, 11:12:41 am
content: Hot glue?(nb. I don't know how warm the board will get in use...)

author: Decoman
author_rank: Regular Contributor
timestamp: April 16, 2018, 01:51:35 pm
content: Quote from: Bud on April 11, 2018, 04:32:02 pmIn academia, I believe that it is common to use the characters (...) to indicate an omission in a quoted sentence, such that the reader will know that things have been omitted in a quotation. The three dots is called an 'ellipsis' and is meant to obscure some other meaning, by omission.https://en.wikipedia.org/wiki/EllipsisUnfortunately, a lot of people seem to think that using ellipsis in a sentence is ok, so as if to indicate sarcasm, by not explaining themselves when first expressing some opinion in a shortened or a poignant way, which I always find annoying as a reader, as I shouldn't have to guess at what their rationale is for any given point of theirs.Then there are people that like using ellipsis as a pause of sorts. I personally like using .. (two dots) to create this sense of suspence, instead of going full ellipisis with an overwhelming three dots with no brackets (or whatever these are called around this sentence here).Whenever I quote somebody but don't want to quote the entirely of a sentence, I always with no exception use the academic use of ellipsis, making sure to write (...) at the start, or at the end of a sentence I am quoting. I supposed you could use it right in the middle of a sentence as well.I guess I am glad that I have the Yamaha HS80M studio speakers myself.Hopefully I will never get to have the same issue with mine as with the KRK's.

author: T.Balázs
author_rank: Newbie
timestamp: April 20, 2018, 08:29:21 am
content: Thanks For the tweeter video Dave!Actually, i was curious if others may have any chance of rescuing a tweeter after an amp failure like this.It seems just hopeless as the aluminium coil formers are bent after hitting the bottom of the gap.If it would be any respectable piece of gear it could be repaired I have seen much worse damages repaired on speakers wort the price and as someone mentioned in the youtube comments those professional drivers are designed to be repairable like the ones in big pa systems with bolted together magnet units and readily available voice coils, tweeter dome assemblies and so on.

author: Brumby
author_rank: Unknown
timestamp: April 20, 2018, 09:08:58 am
content: I don't doubt that repair is possible - it's just at around $30 to buy a new one, you would have to ask yourself if the effort was really worth it.

author: kevdotcom
author_rank: Newbie
timestamp: May 03, 2018, 07:05:10 am
content: My Rokit 8's had the static noise problem, so I opened them up yesterday to finally do the repair.I could only get the small 1000uF capacitors at my local electronics store because the big 4700uF ones were out of stock, so I only replaced those and the 2.2k resistor.(the one in my right speaker measured with 600 Ohms and the shell was all broken)Put everything back together, plugged them in and voila! No more 100Hz static buzz.You guys can't imagine how relieving this feels.It was quite loud on the right speaker and now they only have the usual very silent hiss you can only notice if you stick your ear to it.Big thanks to Dave for giving me the confidence to solder around in a speaker I wouldn't be able to replace right now if I broke it