This is a review and detailed measurements of the Parts Express C-Note DIY Kit. It was kindly purchased, put together and shipped to me by member @ Winkleswizard . A pair of these with everything you need including the cabinet "flat pack" costs just US $100. And that includes free shipping if you are in US. So quite a bargain if it performs well.Being unfinshed MDF, there is not much to look at as far as asthetics:But there are some technical points to note. First is the inclusion of a waveguide around the tweeter to bring the "directivity" (spread of the sound wave) closer to that of the woofer at crossover point (woofer gets directional there). The tweeter is also moved closer to woofer to reduce the center to center distance as to improve vertical directivity. The waveguide is NOT notched however. The woofer simply overlaps it.The MDF cabinet felt quite stout to me both in feel and in use. There is certainly more to it than what you get in budget speakers.Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS) . This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise.In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.All measurements are referenced to the tweeter axis with frequency resolution of 2.7 Hz.Due to reduced bass response (I think), the accuracy of projected frequency response degraded a lot below 70 Hz. It was an unusual development which I think was caused both by the speaker output and longer distance I used to measure it. So don't be concerned about that portion of the graph not being as clean as it normally is.Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker can be used. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:My first reaction to the graph was "this is not good." But there are really two things that visually look bad as noted on the measurement. The bass level is generally lower and there is peaking around 700 Hz. Sensitivity is on the low side as well depending on where you draw the line (i.e. what frequency range you average).Those issues aside, for a budget speaker the response seems reasonably flat in the critical area. Directivity is reasonable as well around crossover point.Sum of important "early" reflections shows rather smooth response, sans the aforementioned 700 Hz resonance:Predicted response in a simulated "average" listening room reflects what we have already learned:Impedance is rather high for a bookshelf speaker which is easier on the amplifier:Most of the time we see impedance dips below 4 ohm.I didn't note it on the graph but there is a "kink" in the phase and amplitude response around problematic 700 Hz. This does not show up as harmonic distortion though:Instead we see the rising distortion at crossover point which could either be the woofer going too high, or tweeter going too low.Here is the in-room response (of the lab) and absolute level of distortion, this time averaged to 1/20 Hz to make it easier to read:You can see the same shelving of the bass response, 700 Hz boost, etc. Worst case response above 1 kHz is 40 dB below listening level.Horizontal directivity shows that you don't want to toe in/out the speaker too much:Waterfall display shows the pesky resonance at 700 Hz:I was set to not like this speaker, biased by what I saw in the spinorama and that turned out to be the case with the first female vocal track I played. The sound was a bit dull and tonally wrong for a female voice. Before going further, I thought I dial in a parametric filter around 700 Hz and see if it improves things:That it did! Detailed improved as did tonality. I ran through a bunch of my reference tracks that sound good on my system (Revel Salon 2 speakers) and almost all translated well to this little speaker! The sound was quite enjoyable and not too bright. Interestingly, there was good bass there. Even better was the fact that this speaker could play loud, really loud. I am talking filling a very large open space with just one speaker playing and no sign of bottoming out!I think there is something clever going on with bass here. But having it be at lower level it doesn't push the woofer hard. Indeed I could barely see it moving unlike some other speakers I have tested where the woofer cone seems to want to jettison out. Perhaps room enforcement is helping. It is certainly a deviation from "ideal measurement" that seems to work.I should note that I was not entirely happy with the sound of female vocals at the end but with playing more with EQ you could get there possibly.Regardless, I sat there and listened to track after track and did not want to stop. Whoever says you need two speakers to enjoy music is clearly wrong. With the right speaker response, a single one can sound really good.The Parts Express DIY C-Note kit doesn't have an ideal response but seemingly what it has is very good. It can play loud in a pleasant manner with good detail and solid bass. I have tested other budge speakers but they don't play this loud and this well.If can handle a bit of gluing and finishing, you can have a very good sounding budget speaker here.-----------As always, questions, comments, recommendations, etc. are welcome.I bought a ton of chicken to feed the panthers during the pandemic. Well, they are getting tired of it and demanding steaks! Can't blame them other than I am too cheap to spend my own money on it. So I am going to turn to you tousing