I purchased this subwoofer immediately after I got the two MR6mk3 studio monitors. I felt like I need more punch in the bass, so I said to myself that I deserve it, hence here it is: MR10Smk3 subwoofer.
Front view with cover
Front view without cover
Rear view with controls
Inside view - DMOS transistors heatsink and the big transformer
Inside view - mains EMI/RFI filter on the left, inputs and tone control on the right, also transformer and amplifier on top
Based on Mackie's documentation manual http://mackie.com/sites/default/files/PRODUCT RESOURCES/MANUALS/Owners_Manuals/MR10Smk3_OM.pdf, the MR10Smk3 subwoofer is powered by a 120W RMS (240W peak) Class A/B monolithic integrated circuit amplifier with DMOS power stage, exactly like in MR6mk3 active monitors. If inside the active monitors there's indeed a Class A/B monolithic IC, inside the MR10Smk3 there is actually a Class D amplifier instead! Fine with me, but I was expecting the specs and datasheet to state that in the first place...although, I'm sure I wouldn't purchase it anymore if I knew it's class D, but I'll call myself too subjective.
For example, inside the MR6mk3 there are two reputable low-noise 100-Watts TDA7294 Class A/B amplifier chips, so I thought that inside the MR10Smk3 would be something similar, instead I found one IRS2092S Class D chip followed by three TO-220 transistors soldered on the back of the PCB and mounted to a big heatsink. Two of them are probably IRF6645 or similar, based on the datasheet and recommended schematic. Also, on main PCB is written Class-D v1.0 amplifier, so I don't know why the specs from their website says otherwise. Also IRF datasheet here: http://www.irf.com/product-info/fact_sheet/audio-irs2092.pdf.
The IRS2092S Class D chip
However, probably amplifier's schematic is similar with the one found on pag. 2 of https://www.infineon.com/dgdl/an-1138.pdf?fileId=5546d462533600a40153559a077610d1 and the two MOSFETs are the ones already mounted on the big heatsink; also, the coil could be seen in the pictures. As per chip's specs, there are no Turn-ON and -OFF audible click noise, so when powering ON I need to check the LED if it's lighten or not, yes that quiet, which is great actually.
The two MOSFET transistors on top
The two MOSFET transistors on top
I wrote Mackie a message about this, through their website, over 1 year ago, but no reply yet, although their website got updated to reflect the reality and correct their initial "mistake":
Too bad the PDF datasheet and all vendor are still using the AB class wording.
The internal mixer and analogue controls is getting power from the internal EI transformer (2x15V/0.5A), then is regulated through a small rectifier bridge and ST L7815CV/L7915CV 3-pin LDO chips. The power amplifier gets the power from the same EI transformer (2x32V/1.8A) that is regulated via a big rectifier bridge and two big 6800uF/80V @105C CapTop capacitors. The opamps used are JRC 4558, similar with the ones found in MR6mk3: ST 4558.
The two linear regulators powering the internal mixer and analogue controls
Top view of the class-D amplifier
Despite the JRC4558 opamps and the thread from here, my MR6mk3 speakers sound very good connected through this subwoofer. Basically, the sound coming from the DAC enters the subwoofer where is getting mixed with the subwoofer's amplifiers, so JRC4558 opamps are there as additional output buffers that act as a sound mixer/preamplifier circuit. However, there's no additional noise injected into the two MR6mk3 studio monitors connected to this sub and clarity and details are really good, definitely above average. Also, retrieval of details and audio quality is not affected in any way by the mixer from inside this subwoofer.
I found the gain/amplification for the subwoofer as being too high. Even if I'm feeding it with a normal 2V RMS DAC, via single ended TRS plugs, I keep the LEVEL knob to about -25dB to match monitors volume, which is very low. This is not something bad, but I was hoping the LEVEL should be somewhere around 0dB.
I really like the EMI/RFI filter from mains, just before the transformer. I wasn't expecting for such a filter on a not so pricey subwoofer.
All the internal components were very well soldered and also glued on the backplate: caps, bigger resistors, cables were mostly wrapped together, so no strange noises could be created inside the speaker. Even the big heatsink was very well glued on the backplate as well. All holes, all PCB and backplate screws and input/output plugs/connections were sealed too with incolor or with black sealing glue, so all air movement is done correctly only from the front bass port.
I'm not a fan of CapTop capacitors, but at least all of them are rated to 105C; hope they'll last enough years to please my ears.
The padding/stuffing from the internal cabinet was above average glued and size, so I needed to glue again some part of the padding, just to be sure the air will not move the padding inside. Also, the black vinyl coating was getting unglued when I was moving the sub with my hand, probably I was not paying too much attention to the edges, so a bit of glue fixed it instantly. I will be treat it with good care after.
External coating pealing off from corners
Case is 15 mm thick on all sides and the 4 corners and sides are reinforced with small pieces of wood of 20-25 mm thickness. Under the case there are 4 generous rubber feet that minimise bass vibrations and make the subwoofer's case very steady on the floor.
Speaker itself has exactly 3.5 ohms of internal resistance and is connected to the power amplifier through about one feet of 20 AWG cables. Kinda thin cables I'd say, but should probably sustain the max. 5-6 ampers that feed the 3.5 ohms speaker for average-to-high listening levels. After all, this subwoofer is not a house-shaker, but it has plenty of power for my 15 m2 bedroom and also for my 25 m2 living room when I test it recently (actually 40 m2 open space, but plenty of bass for entire space). The main issue is the furniture I'm using that is shaking and gets "noisy", not the sub itself.
I'm not using the Auto Power "feature" because either is not working as expected in my setup, either it has some flaws. I'm keeping it ON for 100% of time, this is the only way I can get the Green-light and to hear the music.
Power consumption written on the back of the subwoofer, 250W, seems unrealistically high for a 120W RMS Class-D amplifier, but to be honest I wasn't testing how much power it drains from the outlet. This amplifier should have a power efficiency of 90%, so I estimate that power consumption is somewhere lower than 200W
PRO:
- bass sounds very good, well extended
- great punch (though, could sound a bit relaxed with some tracks)
- crossover freq goes down to 40Hz, that should help out in paring with lot of monitors
CON:
- no RCA in/out (some could still use non-balanced cables)
- no XLR out (though, there is XLR in)
- gain is just too high, I use volume level knob at 9 o'clock (half volume is at 12 o'clock, max. volume is at 5 o'clock)
PDF datasheet attached to this post as well.
Front view with cover
Front view without cover
Rear view with controls
Inside view - DMOS transistors heatsink and the big transformer
Inside view - mains EMI/RFI filter on the left, inputs and tone control on the right, also transformer and amplifier on top
For example, inside the MR6mk3 there are two reputable low-noise 100-Watts TDA7294 Class A/B amplifier chips, so I thought that inside the MR10Smk3 would be something similar, instead I found one IRS2092S Class D chip followed by three TO-220 transistors soldered on the back of the PCB and mounted to a big heatsink. Two of them are probably IRF6645 or similar, based on the datasheet and recommended schematic. Also, on main PCB is written Class-D v1.0 amplifier, so I don't know why the specs from their website says otherwise. Also IRF datasheet here: http://www.irf.com/product-info/fact_sheet/audio-irs2092.pdf.
The IRS2092S Class D chip
However, probably amplifier's schematic is similar with the one found on pag. 2 of https://www.infineon.com/dgdl/an-1138.pdf?fileId=5546d462533600a40153559a077610d1 and the two MOSFETs are the ones already mounted on the big heatsink; also, the coil could be seen in the pictures. As per chip's specs, there are no Turn-ON and -OFF audible click noise, so when powering ON I need to check the LED if it's lighten or not, yes that quiet, which is great actually.
The two MOSFET transistors on top
The two MOSFET transistors on top
I wrote Mackie a message about this, through their website, over 1 year ago, but no reply yet, although their website got updated to reflect the reality and correct their initial "mistake":
Too bad the PDF datasheet and all vendor are still using the AB class wording.
The internal mixer and analogue controls is getting power from the internal EI transformer (2x15V/0.5A), then is regulated through a small rectifier bridge and ST L7815CV/L7915CV 3-pin LDO chips. The power amplifier gets the power from the same EI transformer (2x32V/1.8A) that is regulated via a big rectifier bridge and two big 6800uF/80V @105C CapTop capacitors. The opamps used are JRC 4558, similar with the ones found in MR6mk3: ST 4558.
The two linear regulators powering the internal mixer and analogue controls
Top view of the class-D amplifier
Despite the JRC4558 opamps and the thread from here, my MR6mk3 speakers sound very good connected through this subwoofer. Basically, the sound coming from the DAC enters the subwoofer where is getting mixed with the subwoofer's amplifiers, so JRC4558 opamps are there as additional output buffers that act as a sound mixer/preamplifier circuit. However, there's no additional noise injected into the two MR6mk3 studio monitors connected to this sub and clarity and details are really good, definitely above average. Also, retrieval of details and audio quality is not affected in any way by the mixer from inside this subwoofer.
I found the gain/amplification for the subwoofer as being too high. Even if I'm feeding it with a normal 2V RMS DAC, via single ended TRS plugs, I keep the LEVEL knob to about -25dB to match monitors volume, which is very low. This is not something bad, but I was hoping the LEVEL should be somewhere around 0dB.
I really like the EMI/RFI filter from mains, just before the transformer. I wasn't expecting for such a filter on a not so pricey subwoofer.
All the internal components were very well soldered and also glued on the backplate: caps, bigger resistors, cables were mostly wrapped together, so no strange noises could be created inside the speaker. Even the big heatsink was very well glued on the backplate as well. All holes, all PCB and backplate screws and input/output plugs/connections were sealed too with incolor or with black sealing glue, so all air movement is done correctly only from the front bass port.
I'm not a fan of CapTop capacitors, but at least all of them are rated to 105C; hope they'll last enough years to please my ears.
The padding/stuffing from the internal cabinet was above average glued and size, so I needed to glue again some part of the padding, just to be sure the air will not move the padding inside. Also, the black vinyl coating was getting unglued when I was moving the sub with my hand, probably I was not paying too much attention to the edges, so a bit of glue fixed it instantly. I will be treat it with good care after.
External coating pealing off from corners
Speaker itself has exactly 3.5 ohms of internal resistance and is connected to the power amplifier through about one feet of 20 AWG cables. Kinda thin cables I'd say, but should probably sustain the max. 5-6 ampers that feed the 3.5 ohms speaker for average-to-high listening levels. After all, this subwoofer is not a house-shaker, but it has plenty of power for my 15 m2 bedroom and also for my 25 m2 living room when I test it recently (actually 40 m2 open space, but plenty of bass for entire space). The main issue is the furniture I'm using that is shaking and gets "noisy", not the sub itself.
I'm not using the Auto Power "feature" because either is not working as expected in my setup, either it has some flaws. I'm keeping it ON for 100% of time, this is the only way I can get the Green-light and to hear the music.
Power consumption written on the back of the subwoofer, 250W, seems unrealistically high for a 120W RMS Class-D amplifier, but to be honest I wasn't testing how much power it drains from the outlet. This amplifier should have a power efficiency of 90%, so I estimate that power consumption is somewhere lower than 200W
PRO:
- bass sounds very good, well extended
- great punch (though, could sound a bit relaxed with some tracks)
- crossover freq goes down to 40Hz, that should help out in paring with lot of monitors
CON:
- no RCA in/out (some could still use non-balanced cables)
- no XLR out (though, there is XLR in)
- gain is just too high, I use volume level knob at 9 o'clock (half volume is at 12 o'clock, max. volume is at 5 o'clock)
PDF datasheet attached to this post as well.
Last edited:
1x Mackie MR10S Mk3
