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Mackie MR6mk3 - inside pics and personal thoughts

trl

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It's been about 1.5 years since I bought a pair of Mackie MR6mk3 audio monitors. I like the sound...some might call it a bit brighter, but with a tiny of EQ will flatten the spectrum instantly.

These are really nice-looking speakers with high power output, 6.5” polypropylene woofer, 1” silk-dome tweeter, both drivers being powered by separate AB class amplifiers. Inside amplifiers are made with two DMOS monolithic integrated circuits, one for woofer and the other one for the tweeter, sharing the same PCB and heatsink, able to deliver up to 40 watts/4 ohms RMS for woofer (80 watts peaks/music) and 25 watts/8 ohms RMS for tweeter (50 watts peaks/music). Mackie says this will do a total of 65 watts RMS per speaker (some might say that woofer's output power gives total speaker's power), power that translates into a maximum 111 dB SPL @ 1m /pair, enough for most small and mid-sized studio, apartments or homes (up to 40 sq. meters).

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Front view

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Backside view
The cabinet is made of MDF and it has 12 mm thickness on the sides and 25 mm in front. Tweeter is "incapsulated" inside an additional 10 mm MDF small cage, most likely to reduce vibrations transmitted from the woofer. Inside cables are strapped and tighten together nicely, but with no phono absorbent fabric around them. Instead, there’s enough phono absorbent on the sides that should take care of bass reflections from within the cabinet.

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Inside cabinet

After pluging the monitors into the power outlets and RCA cables into my DAC I’ve noticed an audible hum and also a buzz coming from both left & right speakers. It was more pronunced during the evening and night, but during the day it was somehow acceptable (could only hear it between the tracks). Anyway, this was something that needed investigated immediately, because this sounded like a ground loop to me, so unpluging both monitors from the mains and re-pluging them into a custom-made 250 VA isolation transformer created a huge smile to my face: no more buzzing sound coming from my speakers anymore! Isolation, but also lifting mains ground properly did helps in this case.

Now, after lifting the ground, I was having a really hard time to find some noise coming out of these good-looking studio monitors. Standing in front of both speakers I couldn't get any background noise getting out, but moving my ears as close as 25-30 cm in front of the tweeter I was able to hear some hiss, but only if room's background noise was very low. Also, while literally sticking my ear to the woofer I was able to hear some hum and hiss-noise too, but besides me I'm not sure if anyone else would really stick the ear directly into the woofer to search for such noises.

Conclusion: these speakers are very quiet if there are no ground loops and decent signal cables are used, so definitely a big advantage over many other studio monitors in this price range (lot of people complain on the Internet about hiss or hum, even on monitors costing twice this price).

Wile listening ATB - Chapter One I find the bass quite powerful, if not striking, with enough punch and feel into my stomach to please me enough. It took me a while to position the speakers inside my 15 m2 bedroom, on top of the stands, at ear level and I realized that my bedroom creates a couple of spikes around 80 Hz and 125 Hz, so I notched down with -2dB those frequencies directly from foobar's parametric EQ to neutralize the sound. In my 25 m2 living room I couldn't notice these two spikes, so it must be from my bedroom, most likely because both speakers are pretty close to corners or the bedroom (will get some bass traps soon to compensate this).

Sound is full, soundstage is good, but that really depends on room size, shape and furniture installed. I find details as being a strong point of these speakers, sometimes I even felt the need to reduce with -2dB the treble from the rear button, but then I realised I'm maybe too close and upfront to the tweeters, so moving back a bit increased the space in the music and bass was also delivering even more energy, being strong, full and fast enough to hear all the instruments and drums.

While listening Katie Mahan, piano with extreme dynamics, I felt that MR6 mk3 might even be more revealing than my AKG K701 headphones. Basically, I was able to hear even the smallest vibration of air of the recording room, not just piano vibes.

After hearing a few hundreds of tracks, FLAC and DSD as well, I can say that voices are clear, trebles are accurate, bass is probably best in class for such 6.5" woofers, though some people might feel upgrading with Mackie's mk3 10" subwoofer. For the moment I'm OK with the bass, also in my 15.5 sq meters I'm not sure what a subwoofer could do (it's very hard to correctly setup a subwoofer in small rooms and filled with furniture and most of the times it might do more worse than better to the final sound).

Like all the other studio monitors in not-so-well-treated rooms, finding a good spot for auditioning to take advantage of bass reflections from the walls or furniture helps a lot. In my case, standing in front of speakers at about 1-2 meters did helped, but moving on either side or 3-4 meters in front of speakers will decrease the bass punch and will make the MR6 mk3 6.5" woofers to sound like 4" ones. Like I said before, this is going to happen with all studio monitors in small rooms, this is why auditioning speakers from different positions is a must. I was able to find a very good sound in both my living room and my bedroom, so I'm quite sure Mackie MR6 mk3 sound will please most of us looking for 6.5" powered speakers in this price range.

Like all the other studio monitors in not-so-well-treated rooms, finding a good spot for auditioning to take advantage of bass reflections from the walls or furniture helps a lot. In my case, standing in front of speakers at about 1-2 meters did helped, but moving on either side or 3-4 meters in front of speakers will decrease the bass punch and will make the MR6 mk3 6.5" woofers to sound like 4" ones. Like I said before, this is going to happen with all studio monitors in small rooms, this is why auditioning speakers from different positions is a must. I was able to find a very good sound in both my living room and my bedroom, so I'm quite sure Mackie MR6 mk3 sound will please most of us looking for 6.5" powered speakers in this price range.

The inside PCB looks decent, all parts are soldered nicely and caps are glued to PCB to not interfere with woofer’s vibrations. Same PCB is also used for both MR5mk3 and MR6mk3 speakers; this is actually written directly on the PCB.

No toroid transformer inside, instead there's a decent E+I trafo with a basic EMI shield around it. It outputs 2x16V/2A, so a total of 64VA.

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Transformer, bridge and filtering capacitors

Two reputable low-noise 100-Watts TDA7294 chips are used as power amplifiers, one for each driver: woofer & tweeter. These chips are well-known on most Hi-Fi forums and I consider a great advantage to use them inside these speakers. Also, some people would say that A/B class amplifiers might have a lower-noise and a better overall output sound than class-D amplifiers (I also agree with this one too). The two power chips are using rather a low voltage, so output power would be much lower than the max. 100 W advertised by the datasheet, but should be enough to drive these speakers to enough dB.

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The two amplifier chips TDA7294: one for woofer and the other one for tweeter


Anyway, based on TDA7294 datasheet and looking to the transformer output voltage from inside MR6mk3 (+/-16V/2A, but after bridge rectifier and smoothing caps that should be around +/-19...20V when bass is pumping), I'd say that Mackie's output numbers could only be achieved with a THD between 0.5% and 10%. For a max. THD of 0.5% I would approximate an output power of about 35W for the woofer and a bit over 20W for tweeter, still more than enough for my bedroom and good enough for my living room.

TDA7294-output_power.png


Well, no Silmic, no Nichicon, no Rybycon, no ELNA, no PANASONIC, no VISHAY, no WIMA, no SANYO, no NIPPON CHEMI-CON caps inside, just some caps branded "Cap-top" polarised caps and not-labeled polarised caps. I was not even able to find any datasheet or manufacturer name on the Internet about them. Well, at least they're rated at 105C...hope they'll last for a couple of years, though they're half the size of other caps rated the same capacitance and voltage (perhaps ripple current would be different).

There's a big bridge rectifier followed by 2x4700uF/35V @105C caps. For tone correction and low-pass/high-pass filters we have a pair of ST L7812CV/L7912CV used as power regulators.


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Bridge and the two linear regulators that powers tone corrections and low-pass/high-pass filters inside

The 6 x ST4558 opamps from inside just "made my day"; same opamps are used in many low & mid priced audio equipment like Genius, M-Audio, EMI, Logitech, but also in KRK, JBL etc. Is it so complicated to get some decent opamps like NJM5532 (very cheap actually) or NJM2114D or LM4562 that are cheap enough and generally accepted (read as: tolerated) by most audiophiles out there in mid-priced Hi-Fi equipment? Not even dare asking for MUSES 8820 or above this price, of course, but perhaps manufacturers did tested these ST/MC 4558 opamps and considered they're a good wire with gain to use inside these speakers, so please take this paragraph with a grain of salt (or just ignore it).

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ST4558 op-amps from bottom of PCB used for pre-amplification/gain and tone controls
Measurement tests for the original NJR/JRC 4558 opamp and also for many others could be found here.
Opinions about the original NJM4558 could also be read here.

Some specs of the ST4558's datasheet (this is the improved version of the original NJM4558, at least comparing the specs):
- Unity/Gain bandwidth: 2.8/5.5 MHz
- Slew rate: 2.2 V/uS
- Noise: 12nV/SqrHz
- THD: 0.008%

Please, do understand that I'm not happy about the no-name or very low-price and low-quality electronic parts, especially electrolytic caps like: ChengX, Yihcon, KYS, Cap-Top etc. (see Capacitor plague) because I've seen caps blowing away inside amplifiers and I'm also spoiled by the audiophile community forums, but also because I'm a DIY-er that knows something about electronics and about the lifespan of low-quality capacitors, especially when used in power supplies. Even KRK Rockit is using low quality caps in their low-priced monitors and results were shown here:
- M-Audio BX5 D2 - Custom PC Review & Mr. Ives
- ADAM A7X - Gearslutz and the cheap and bad quality caps is using inside.
- KRK Rokit 5 - Gearslutz
- KRK Rokit 6 - Cakewalk forum
- KRK Rokit RP8 - KVR Audio, Gearslutz, FiveFish (not quite caps related, but still interested reading on all 10 pages)
- Mackie MR8 - Youtube

Despite my picky opinion about the electronic components from inside the cabinet, these speakers do sound good indeed, so I can recommend them for their price, especially that Mackie is a respectable brand in this market and totally deserves our confidence. I would probably rate them 4.5 stars out of 5 for their look and sound without hesitation, because they sound neutral and revealing with enough bass for 6.5" woofers.

Some of tracks/albums listened:
  • Dire Straits - Communique
  • Pink Floyd - Dark Side Of The Moon
  • ERA - The Very Best
  • Fone/Native DSD - Natural Jazz Recording
  • ATB - Distant Earth
  • Ayre - Katie Mahan Collection
  • Chesky - Best of Classics and Jazz and Audiophile Test
  • Head-Fi And HDtracks - 2010 - Open Your Ears
  • Manley Lab - Headphones Test Disc
  • BBC - Legendary Sound LS3/5A
  • The Nordic Sound - 2L Audiophile Reference Recordings
  • ABC Special Sampler - Ultimate Demo Disc
  • Michael Jackson - Dangerous
  • Michael Jackson - Blood On The Dance Floor
  • Michael Jackson - Michael
  • Michael Jackson - Off The Wall
  • Musique d'abord - PACHEBEL (Canon & Gigue Chamber Works)
  • Various Artists - Cafe del Mar XXII
  • Various Artists - Pure 80s
  • Various Artists - The Rough Guide To Ethiopian Jazz
  • Various Artists - Hit Zone no. 538, Best Of 2016
Datasheet here: https://mackie.com/sites/default/files/PRODUCT RESOURCES/MANUALS/Owners_Manuals/MR8mk3_OM.pdf, but also attached t this post as PDF.

Note 1: In case you’re trying to lift the ground by removing the ground pin of your mains plug, just don’t do it! Mains ground is directly connected to the aluminium backplate where all the audio connectors are installed, so lifting the ground improperly may cause injuries or even death when touching audio cables or rear backplate of the speakers! So, either you use an isolation transformer, either use dedicated ground-loop removal devices with diodes, resistors and capacitors inside, but don’t lift directly the ground from the plug or from the outlet!

Note 2: One speaker is making a "pop" noise about 5" after powering off, right after capacitors get discharged; on powering on is silent. The other speaker is completely silent on both power on & off. Either workmanship, either Q&A, either some components are having a different value than suggested on original schematic (or high tolerance values).

Note 3: A similar review was posted on SBAF about 1.5 years ago.
 

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pozz

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Really nice review.:)
 

ernestcarl

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I have the larger MR8s. Some people say to me the speakers look ugly, but I think they look pretty nice with the silver accents. They don't measure too bad as well in comparison to other speakers (did some measurements with REW before). Although I found I had to adjust the treble shelf to -2dB as I found the treble just a tad harsh flat. Some EQ in the bass, and they're pretty good -- esp. for the money. Haven't opened to inspect mine though. Thanks for that!
 
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trl

trl

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I like their look, you do tell to those people that they are probably ugly. :)

Speakers measure OK with REW, I like their sound very much, but the front panel (plastic) starts to vibrate (a bit) with sinewaves @ around 150-200 Hz (>90dB sines). Music sounds very detailed, I have no complains.
 

maty

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maty

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http://noaudiophile.com/JBL_LSR305/
Charles Sprinkle the designer of this waveguide said that the M2 (high dollar version of these speakers) waveguide is filled with epoxy on the back to eliminate ringing because the waveguide can act like a bell. From what I can tell this would be a pretty simple DIY upgrade to these speakers if you can source the epoxy and not melt the baffle in the process. There is a lip that follows the outside edge of the baffle to attach it to the wooden box, so you should be able to just pull the plate amp off of the back and fill it up to that point and wait for it to dry.
 
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