MoFi Sourcepoint 8 or Q Acoustice Concept 50s

@pryso Thanks for the insight.  I have spent 30 years rolling gear and scrounging for older high end components that I could not afford when new and I hope to be at the end of that endeavor.  Just finished the Linn LP12 with better arm, MC cart, and very fine phono stage.  I really enjoy my Magnapans, but they do not fill the house like a vintage Klipsh would.  You know - that sound of live music in the next room.  Now that i have settled on my equipment, it is time to listen to the music (not in just the sweet spot) and stop listening to the equipment.  I will try the SP8 and see if they fit the bill.

If the goal is to address only the impedance rise around 2 kHz (as MoFi did with the SP-10 ME), a more refined approach is required.

There is a Audiogoner who PM me to ask about this.  Instead of replying back privately, I will share here for the benefit of the group.  In order to notch down the impedance spike at a specific frequency, such as 75ohm at 1.6khz in the case of SP-8 (see the above imp.-phase chart), you need a so-called LCR serial components in parallel with the driver, which consist of an inductor, a capacitor and a resistor.  Here is how you design the LCR serial components.  First, since the target impedance we try to notch down is the nominal impedance of 8 ohm, use the voltage divider formula to back track the required resistor value, i.e., R = (75x8) / (75-8) = 9 ohm.  Then select a proper capacitance value, preferably from a higher quality part commonly available in the market, say, C = 10 micro Farad (uF) and use peak freq. = 1/[2 pi (LC)^.5] to back track the required inductance, L, which can be calculated as 1/C/(2 pi peak freq.)^2 = 1.0 milliHenry (mH).  So now you have acquired the 1st set of trial values for LCR, i.e.,

L = 1.0 mH; C = 10 uF and R = 9 ohm;

Next check the resulted Q value which define the shape of spike = peak freq. / bandwidth.  The Q = 1/R x (L/C)^.5 = 1/9 x (0.001/0.00001)^.5 = 1.1, meaning the resulted bandwidth of the notch filter is approximately 1.45 khz which seems to cover the shape of the spike reasonably well.  So this seems a good starting point.  It will take some iterations to ultimately iron out the peak as shown in the SP10 ME but this process should give you a pretty good idea how to design a proper notch filter.

I have the Concept 50 in my 17’x17’ room and they are fantastic. I have used them with the following amps and they perform well with all of them. If you want sound stage, imaging, and smooth treble, slight warm mid range, strong bass response the Concept 50 are hard to beat IMO. 
 

Amps: Kinki Studio EX-M1+, Orchard Audio Starkrimson Ultra, Orchard Audio Starkrimson 25 Mono Blocks, Willsenton R8. 

I would go for the Sourcepoint 8s.

I have owned dozens of speakers between the $3K and $12K price points, dozens… The Concept 50s were one of the most disappointing of them.

They were smooth and warm, but that’s where their strengths ended. The bass was very “one-note”, the imaging was just OK, and they homogenized everything played through them. And despite all the work they allegedly did to quell cabinet resonances, I could still detect a good bit of cabinet noise. Overall, an overhyped speaker. They had the looks and feel of $3K speakers but the sound quality of $1K speakers. 

The Sourcepoint 8 probably isn’t perfect either (no speaker under $5K is) but based on measurements I would expect it to be considerably more neutral. Plus, no MTM speaker (mid-tweeter-mid) can match a good coaxial driver for imaging. 
 

Neither. Save some money and buy the Sonner Legato Unum with stands. 

https://pt.audio/2020/12/18/sonner-audio-legato-unum-loudspeaker-review/

https://www.monoandstereo.com/sonner-audio-legato-unum/