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Parts Express DIY C-Note Speaker Review

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Parts Express should call this speaker G Note or A Note. Because the resonance is close to 784hz G5 note or 880hz A6 note.
 

DSoreal

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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:
View attachment 59329

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. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than anechoic chamber. 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.

Spinorama Audio Measurements
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:

View attachment 59331

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:

View attachment 59333

Predicted response in a simulated "average" listening room reflects what we have already learned:

View attachment 59334

Impedance is rather high for a bookshelf speaker which is easier on the amplifier:

View attachment 59335

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:

View attachment 59336

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:

View attachment 59337

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:

View attachment 59338

View attachment 59339

Waterfall display shows the pesky resonance at 700 Hz:

View attachment 59340

Speaker Listening Test
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:

View attachment 59341

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.

Conclusions
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.

I am going to put the C-Note on my recommended list of budget speakers.

-----------
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 to donate what you can to feed these hungry panthers using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Great review! I think one thing that is worth mentioning here though is the sound stage! To me, this is what makes these a mind boggling value. Get kit, assemble, vinyl wrap, enjoy!
CFDF626F-F86F-435B-8FF9-E3142DA305A9.jpeg
 

unco

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Anecdote: thanks to amir catching the 700 Hz resonance, and Rick Sykora going through a lot of trouble to stamp it out in his build thread, I decided to shorten the bass reflex ports on my C-Notes, confident that it would at least do something other than affecting the bass response.

I can't make any ironclad statement because my room acoustics are bad and I haven't had time to listen critically for long, but I think it sounds (far?) better inside my room. I used to place the C-Notes as "Small" on my receiver and wondered at why it sounded so much better vs. the "Large" setting. Limitations of a 2-way design, I thought. Nope! It was the 7" port interacting catastrophically with my room.

Midbass is now a bit overwhelming, but everything in the midrange sounds much better and that small woofer no longer sets my ears on fire (not as much at least). I won't miss the bass extension.
 

JoelG

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I've been looking forward to a detailed review of the C-note for quite a while now. Thanks Amirm! (dang, you test alot of speakers!)

This is pretty much what I was expecting.

The 700 Hz peak is most likely a resonance, or combination of resonances. I'm not sure if Winkleswisard added any damping inside the enclosure, but I'm guessing not (no problem, I agree with testing the kit as it comes). Internally the cabinet is 10" high, which is just about 1/2 the wavelength of 700 Hz. I assume that is the majority of the issue, a standing wave can add a couple dB peak to vented enclosures. I recommend significant damping in any enclosure to keep that under control (It is not included in the kit just to keep cost down, $100 was a hard target to hit, lol). Also, the side panels have a resonance in that area, so that is adding to it a bit (just a little), adding a brace tying the sides together would help a little. Port resonance might add to it a little, but 700 Hz just seems higher than I would expect for a significant port resonance. You could stuff a sock in it, but you'll kill the bass... Nobody wants that.

I doubt the peak has much to do with a leak around the tweeter. It would be easy to check for that, just play a tone around the tuning frequency. About 40 Hz. You'll hear significant chuffing around the tweeter/woofer overlap if there is a leak. Pressure in the enclosure is highest at tuning, air will get out anywhere is can.

Speaking about the bass response, I'm glad that you are happy with it. The C-note is designed to be used near a wall, so that will add quite a bit of boost if you are looking for flatter low end response. But in my experience, extended low end is better than flatter low end, if you have to choose between the two (small speakers). Your brain is good at filling in dips in low frequenies, but there has to be something there to begin with. So, the C-note enclosure is not exactly optimum, more of an extended bass shelf alignment (EBS). Plus, that keeps excursion under control for better power handling (like amirm said, "I could barely see it moving"). I'm not a fan of speakers tuned to 50 Hz or higher unless it is specifically designed to be used in a system with a subwoofer. That is just a recipe for over-excursion disaster... Just go sealed at that point.

About the higher distortion at the crossover. Yeah, the 3,000 crossover is really pushing the limits of that little tweeter. It was a compromise to get better vertical dispersion. There were many crossover designs, some had crazy flat response, but had many more parts ($$$) and in side by side listening tests the difference was negligible.

The C-note was fun to design..
Yep, the C-note is one of mine. I am the speaker building product line manager at Parts Express, I have a hand in a lot of our kits.

The 1/2" sonic barrier will work great. Line all walls. A lot of people think that 1/2" material won't do much, but keep in mind that the sound waves are bouncing around a lot and at all angles. So after a few reclections at odd angles sound waves will have passed through a buch of material and will attenuate quickly. Everyone worries about the first reflection, but you can never add enough material to really make any significant difference to the first reflection at the frequencies that the most noticable enclosure resonances will occur. You just want to make them decay faster, dont bother trying to eliminate them (well, maybe in a really good transmission line design).

Heck, I usually just add some lightly teased Acousta-Stuf, fill the enclosure about 1/2 way. But really, the 1/2" Sonic Barrier will be much more effective and won't affect tuning enough to worry about. Plus, the adhesive is so aggressive on that stuff it will couple to the walls enough to even lower the panel resonances a little (not that it is a huge issue, but better is always better). After the adhesive cures (I recently learned that the adhesive actually cures in about 12 hours, who knew?) it will actually pull off layers of the MDF if you try to remove it! Seriously sticky stuff!

-Chris P
I have a C-note kit on the way. Merry Xmas to me!
What about laminating additional mdf to the baffle and side panels? In other words, making them 3/4 inch. Would a stouter/more rigid cabinet change anything?
Thanks for doing what you do!
 

Rick Sykora

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I have a C-note kit on the way. Merry Xmas to me!
What about laminating additional mdf to the baffle and side panels? In other words, making them 3/4 inch. Would a stouter/more rigid cabinet change anything?
Thanks for doing what you do!
Welcome to ASR!

Sounds like more work for little clear return. There is no obvious need to bolster the cabinet, but if I did, would just do some internal bracing. A dowel round between the side panels would make them more rigid, but you might also raise any lower resonance to higher (and likely more audible) one...

If you did not order any damping material, the 3/4" Sonic Barrier might be worth considering. Otherwise. enjoy the experience and save your money for other fun stuff. Merry Xmas!
 

Head_Unit

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A dowel round between the side panels would make them more rigid, but you might also raise any lower resonance to higher (and likely more audible) one...
Hence, the idea of a rigid dowel but coupled to the side panels at one or both ends with something viscoelastic.
--> BUT, exactly WHAT viscoelastic material
...that won't harden over time? Those felt pads for the bottom of chairs wouldn't try out, however they are not really viscoelastic and therefore not as dampening.
- It also begs the question, how to attach such? In the past I've cut dowels slightly over-long, wedged them in place, wood glue all around the junction. But if you don't want a totally ridgid coupling, what is holding the dowel in place?
 

Head_Unit

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$100 was a hard target to hit, lol
Yeah speaking as a loudspeaker engineer, my congratulations to you. And to your purchasing department!!

As for "the C-note enclosure is not exactly optimum, more of an extended bass shelf alignment (EBS)" I have to niggle with your verbiage. I think what you did IS optimum. As I've posted elsewhere, folks get WAY too hung up on the -3 dB point like it is some kind of magic. NO, it was just a mathematical convenience for Dick Small's thesis (and I presume following electrical filter design convention). In actual rooms, the -6 or even -10 dB points are more relevant. I was lucky enough to meet Dick when he worked for Harman in Indiana and when I brought that up he agreed, after expressing great surprise I had a copy of his thesis ("we only printed like 100 of those!" - too bad I didn't have it with me for him to sign). Now the "shelf" part of the alignment...ah that always bugs me a bit. I prefer to have a continuous droop without the "shelf" flattening but must admit that is not based on any scientific listening tests at all ha ha.

On a different note (ha ha) what happened to the 12" Dayton waveguide? And any wild thought about a kit with the remaining 10"? THAT would be a heck of a thing- "The Quad 10": 10" woofer, 10" waveguid, twin 10" passive radiators! I suppose commercial considerations preclude any such thing, but if you have advice what to drive that 10" waveguide with, I'm planning to use one as a kind of gigantoid in-wall (behind the wall is a giant cavity under a stairwell. AirPort Express --> nice equalizer of some sort --> power amp --> speakers. Should be FUN).
 
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Finished building my C Notes. I covered them with a cherry paper veneer with a tung oil finish. May wax or varnish over that or poly.
I covered the insides, side, back and top with cotton insulation. https://www.amazon.com/gp/product/B004Y6SX1Y/ref=ppx_yo_dt_b_asin_image_o03_s00?ie=UTF8&psc=1

My listening room (sun room) may be the worst from what I understand 3 walls of glass windows and the fourth is brick. A frame open ceiling.

That said they sound clear but the bass seems muddy? Is that more the material I put inside or the room acoustics?
IMG_4409.JPG
IMG_4406.JPG
 

JoelG

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Finished building my C Notes. I covered them with a cherry paper veneer with a tung oil finish. May wax or varnish over that or poly.
I covered the insides, side, back and top with cotton insulation. https://www.amazon.com/gp/product/B004Y6SX1Y/ref=ppx_yo_dt_b_asin_image_o03_s00?ie=UTF8&psc=1

My listening room (sun room) may be the worst from what I understand 3 walls of glass windows and the fourth is brick. A frame open ceiling.

That said they sound clear but the bass seems muddy? Is that more the material I put inside or the room acoustics? View attachment 102097 View attachment 102096
Could definitely be some soundwaves bouncing around in a room like that. Carpet, acoustic tiles on the walls and a ceiling... And/or;
If the ports are too close to the wall it can create muddiness.
"They" say to put small speakers on stands clear of walls. Especially ported ones, unless one is trying to get more bass extension by proximity to a surface.
The length of the port is 7 inches. A shorter port will reduce bass extention but make it tighter. (Per the building instructions. I'm no audio engineer, just a musician obsessed with good sound)
Another consideration is a subwoofer with a high-pass crossover. If small speakers get the full frequency spectrum much of the power is wasted on low frequencies which they are incapable of producing anyway, so they can sound muffled.
I only use wav or flac files. MP3 is dead to me. To me mp3s sound like mud even through a great system.
Your speakers look great!
 

Head_Unit

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they sound clear but the bass seems muddy? Is that more the material I put inside or the room acoustics?
Can you temporarily move them way out from walls? Or outside or in a garage or something? How do they sound then? And what do you mean by muddy?
- Because if too strong/boomy then you could stuff the rest of the enclosure with fiberglass which will absorb more midrange, cause the enclosure to appear somewhat larger to the woofer (due to modifying the heat curve of the expanding/contracting air), and thus effectively lower the port tuning a bit. Those things would reduce boominess a bit, though the room will tend to be the dominating factor.
- If by "muddy" you mean they sound distorted, tell us more: what are you playing? How loud? How much are the woofers visibly moving? Are you certain your amp is not clipping?

Meanwhile, the finish looks GREAT!! How hard was that to do? I have never veneered. Is there a seam on the back? Or the veneer just goes on the sides? How did you cut the top and bottom?
 
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Odd that Parts Express sells the C-Note MTM center kit for the exact same $100 price as the C-Note MT. So you get an extra woofer, larger cabinet and presumably greater performance for the same price. Same footprint in vertical orientation but twice as tall.

CORRECTION: C-Note MTs are $100 per pair.
 
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Odd that Parts Express sells the C-Note MTM center kit for the exact same $100 price as the C-Note MT. So you get an extra woofer, larger cabinet and presumably greater performance for the same price. Same footprint in vertical orientation but twice as tall.
The center is $100 each, while the MT are $100 for a pair.
 
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Can you temporarily move them way out from walls? Or outside or in a garage or something? How do they sound then? And what do you mean by muddy?
- Because if too strong/boomy then you could stuff the rest of the enclosure with fiberglass which will absorb more midrange, cause the enclosure to appear somewhat larger to the woofer (due to modifying the heat curve of the expanding/contracting air), and thus effectively lower the port tuning a bit. Those things would reduce boominess a bit, though the room will tend to be the dominating factor.
- If by "muddy" you mean they sound distorted, tell us more: what are you playing? How loud? How much are the woofers visibly moving? Are you certain your amp is not clipping?

Meanwhile, the finish looks GREAT!! How hard was that to do? I have never veneered. Is there a seam on the back? Or the veneer just goes on the sides? How did you cut the top and bottom?
I’m definitely going to play with room placement, the room isn’t optimally arranged.
The veneer took time and effort but wasn’t too difficult.
I first veneered the top and bottom. Then one piece wraps from one side across the front and to the other side. Rear I painted black.
Had to use veneer softener to get it to wrap against the radius.
Doing the sides and front last allowed me to overlap with the top and bottom pieces edges.
I adhered using Titebond applied to both the MDF and the veneer, let dry. Then position the piece and using a hot iron on wool setting adhere the veneer.
I think I’ll do the same with the Swans 3.1.
 

Colonel7

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Finished my Christmas gift C-note. From the build thread for Amir's sample, I took the advice based on results from Rick's tests and I used sonic barrier in the bottom half of the cabinet and made the port the minimum size from the kit. Originally I had thought a compromise between 4 and 7 inches but then I tried them near field and 4" it is to control boom/muddiness. My first build but man, I made some silly mistakes but it was very enjoyable. Also had planned just some duratex and veneer but then I became fixated on making them look different and "reverse klipsch"; definitely look DIY. Next time I'll stick to the veneer! Really like them near-field though. Don't know how some members have such powerhouses for nearfield when I see 6.5 or even 8" desktop monitors for listening enjoyment. C-notes are more than enough db for me.

c-note reverse klipsch_resize.jpg c-note close_resize.jpg c-note straight on_resize.jpg
 

xarkkon

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Finished my Christmas gift C-note. From the build thread for Amir's sample, I took the advice based on results from Rick's tests and I used sonic barrier in the bottom half of the cabinet and made the port the minimum size from the kit. Originally I had thought a compromise between 4 and 7 inches but then I tried them near field and 4" it is to control boom/muddiness. My first build but man, I made some silly mistakes but it was very enjoyable. Also had planned just some duratex and veneer but then I became fixated on making them look different and "reverse klipsch"; definitely look DIY. Next time I'll stick to the veneer! Really like them near-field though. Don't know how some members have such powerhouses for nearfield when I see 6.5 or even 8" desktop monitors for listening enjoyment. C-notes are more than enough db for me.

View attachment 110618 View attachment 110619 View attachment 110620
That's a beautiful build, well done! What paint did you use? How'd you get such a nice smooth sheen?
 

Colonel7

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That's a beautiful build, well done! What paint did you use? How'd you get such a nice smooth sheen?
Thanks - the baffle is Krylon fusion Copper metallic and the rest is a Rustoleum textured metallic called Midnight Copper, all topped with rustoleum clear satin enamel for protection. The Krylon is some nice paint and easy to use; Rustoleum is not forgiving. There's probably about 6 coats all told with the zinnsser bin shellac for the original primer and then some leftover black for a secondary. I didn't go nuts with sanding- think using 250 first pass and then topped out at 400 grit or so for last couple on baffle. Keep in mind this is the better half of the pair. I clamped a little too hard and dented the baffle on the other although it's not too bad
 
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