MC-6C Speaker Measurements and Analysis
Impedance / Phase Measurements of the MC-6C
System impedance doesn’t dip below 8 ohms and maintains a very uniform phase response of – 30 to + 20 degrees throughout most of the audio range. Any decent receiver with a good amplifier section should drive these speakers with ease, but don’t feel shy feeding them some high quality power as they can take it and will also reward you with excellent sound quality.
In Room 1 Meter
Frequency Response (1/12th octave smoothed)
Green – on axis,
Yellow – 15 deg off, Red – 30deg off
the MC-6C’s exhibited an extremely linear response with text book off axis response that would be an NRC members wet dream.
It’s not often I second guess my measurements as being too good for a speaker system, but the MC-6C’s forced me to measure them twice because I was almost dumbfounded by how exemplary they measured. Above 300Hz (below which all the room modal issues were mucking up the measurements), the MC-6C’s exhibited an extremely linear response with text book off axis response that would be an NRC members wet dream. Between the 1-5kHz range, the MC-6C’s were smooth as butter and avoided the typical saddle effect I see on many speaker systems whose design goals are for boom and sizzle effect. You can tell you’ve got a good speaker system on your hands when the manufacturer doesn’t try to cover up its poor midrange performance by boosting the top or bottom end.
Nearfield Frequency Response of MC-6C Woofer
The typical rule of thumb for the acousti-mechanical roll-off rate of a sealed system is 12dB/octave. The roll-off rate for the MC-6C measured a tad steeper (14.25dB/octave attenuation at 30 Hz which is 1 octave below the rated 60 Hz cutoff frequency). This is a function of the slightly elevated Q of the woofer system which has a Q value of approximately 1.
The driver is the MC-6C is virtually the same driver RBH Sound uses in their in-wall/ in-ceiling speakers which operate in a free air/ infinite baffle type environment, so they pretty much have to be bullet proof. The bumped back plate on the motor structure along with the enhanced driver suspension pretty much eliminates any chance of the driver bottoming out. If the driver is severely overdriven with bass frequencies it will eventually burn up, but it should not bottom out. The fact that the speaker is an acoustic suspension design further protects the driver from bottoming out. It’s important to note that even with a roll-off rate of 14.25 dB the roll-off is not as steep as a typical vented speaker which rolls of at 18dB/ octave. Most vented speaker will bottom out without too much effort because the port unloads the driver below the tuning frequency. As you can see from the graph, these speakers don’t produce much tactile bass below 50Hz or so which is why I highly recommend pairing them with a quality subwoofer or two.
Frequency Response Comparison of the RBH MC-6C vs the Status Acoustics Decimo’s
I was curious to see how the MC-6C’s measured up to my reference bookshelf speakers – the Status Acoustics Decimo’s since tonally I found them to be very similar. Sure enough they also measured very similarly, both with very linear frequency response, and superb off axis response. The Decimo’s had more bottom end but also were more susceptible to bottoming out which is why I run them through my processors bass management and couple them with a powered subwoofer.
As an interesting aside, I asked Shane Rich what his design target was when he designed the MC-6C’s and he told me he was shooting NOT against one of their competitors products, but instead for similar performance of the, you guessed it, Decimo’s. Looks like they hit the target quite nicely.
