Dayton Audio C-Note MT build progress

[maty]

Parts Express DIY C-Note Speaker Review
https://www.audiosciencereview.com/...arts-express-diy-c-note-speaker-review.12693/

 

[ROOSKIE]

Putting my kit together now and I've got to say the MDF flatpack is a letdown. I had to sand the fuzzies off the routed back panels as well, just like post #18. Just in general it seems not as nice MDF as the DIYSG kits I've bought, likes to soak up Titebond III and fray at the edges. I'm planning on veneering this pair but I can see how prepping these for paint would be irritating.

Obviously nowhere near knowing how it sounds, and it's no secret the money in these goes to the drivers and crossover, but if this was Babby's First Speaker Kit I'd go with Overnight Sensations, the Baltic birch ply flatpack is just nicer and more idiotproof.

Honestly these are $100 shipped. Do the sanding, let em soak up some glue, no big deal right? This is DIY. Nobody says you have to use the included MDF (which IMHO found to be more than adequate) you can always just make your own box out of baltic birth or whatever material and still be cheaper than the sensations. These are better speakers.
Of course the plywood material would be easier to finish for those just want to stain and have a wood look.

 

[Rick Sykora]

Here is my promised progress update investigating some of the outcomes from Amir's testing. I did not get as far as I hoped as our front lawn needed cutting, but here it is:

1. It is pretty clear that the frequency anomaly around 700 Hz is port resonance. I do find it interesting how much more the Klippel test brought this to light more significantly vs others (including my own albeit limited testing). Was not expecting great results from low budget kit, so had not put much effort in initially. I tried some other options like a larger port diameter and looked into the matching passive radiator. Neither was a major improvement without changing the cabinet significantly.
2. Did put some butyl rubber dampening on the joint between the woofer and the tweeter waveguide. During the test sweep, I thought I heard a resonance around 330 Hz. Maintaining that frequency, I could feel the waveguide vibrate. But the dampening did not change it. Nor did external pipe clamps either (I do this trying to change to cabinet panel resonance). The designer mentioned that he thought some internal dampening was in order. Plan to try that again with something heavier than the Dacron I tried earlier.
3. Did not find an exact match but have few inductors that are much lower resistance than the supplied one. This test will require some crossover surgery and will have to wait a day or two.

This experience demonstrates how much further we can take investigating DIY designs than commercial ones. I think it will also give us a better handle on how Amir's measurements correlate to the design issue(s) that his testing finds. Expect that indirectly it will help us better understand when a problem is found with a commercial design. Would not be surprised if some of the commercial budget speakers had port resonances too.

Stay tuned and healthy!

 

[Rick Sykora]

Next round update...

This morning I set up a test to compare the following:

1. Unmodified C-Note
2. C-Note with 5/8" foam sheet lining lower half of cabinet inside
3. C-Note with (shorter) 4" port (no lining)
4. C-Note with shorter port and lining lower half of cabinet inside

Using REW to measure a full range frequency sweep at the 75 dB reference level, there are only small differences in frequency response between the 4 test cases. Distortion measurements however prominently show a spike at around 1kHz. The unmodified C-Note has a fairly large spike and the other cases have none.

Conclusion in this round:

The cabinet modes likely excites the 700 Hz port resonance. Both the foam lining and the tuning change altered the cabinet modes. #4 had the best overall results.

EDIT: in preparing to post the graphs, may have to alter my previous conclusion. The improvements to cabinet modes are very apparent, the effect on the port resonance is not so clear. Will need to measure impedance to make a better determination. The Bassbox sim does clearly show a difference in the port resonance for the shorter port tuning.

 

[Rick Sykora]

Last round was to replace the woofer inductor with one that has a lower DC resistance. The supplied inductor had a resistance of just under 1 ohm and the replacement was about .5 ohm. I had to unwind one of mine to match the inductance and shortly after my LCR meter became a quarantine casualty. Note this was a more expensive inductor and much larger. For some perspective (stock crossover on left):

This had no measurable effect at the middling output level I tested. A higher output test might reveal more, but would have to be with a simulated load. Nobody in my house is going to tolerate this speaker blaring for an extended period. From what I have learned, would only expect a potential difference from sustained high listening levels. If you are not planning to do so, stick with stock inductor.

On to the next build!

 

[xarkkon]

Next round update...

This morning I set up a test to compare the following:

1. Unmodified C-Note
2. C-Note with 5/8" foam sheet lining lower half of cabinet inside
3. C-Note with (shorter) 4" port (no lining)
4. C-Note with shorter port and lining lower half of cabinet inside

Using REW to measure a full range frequency sweep at the 75 dB reference level, there are only small differences in frequency response between the 4 test cases. Distortion measurements however prominently show a spike at around 1kHz. The unmodified C-Note has a fairly large spike and the other cases have none.

Conclusion in this round:

The cabinet modes likely excites the 700 Hz port resonance. Both the foam lining and the tuning change altered the cabinet modes. #4 had the best overall results.

EDIT: in preparing to post the graphs, may have to alter my previous conclusion. The improvements to cabinet modes are very apparent, the effect on the port resonance is not so clear. Will need to measure impedance to make a better determination. The Bassbox sim does clearly show a difference in the port resonance for the shorter port tuning.

Great work, thanks for the update! What are you using the line the cabinet with? And will the new graphs be posted as well?

 

[Rick Sykora]

Great work, thanks for the update! What are you using the line the cabinet with? And will the new graphs be posted as well?

I am planning to share some graphs, but will confirm the sim results before I do. The sim results demonstrate the situation best.

I lined the cabinets with the leftover foam sheeting from the ZA5.2s: https://www.madisoundspeakerstore.com/acoustic-damping/dampers-foam-sheet-27-x-42-x-5/8/

The .5" sonic barrier is probably a bit better and on sale right now at Parts Express.

 

[Rick Sykora]

Next round update...

This morning I set up a test to compare the following:

1. Unmodified C-Note
2. C-Note with 5/8" foam sheet lining lower half of cabinet inside
3. C-Note with (shorter) 4" port (no lining)
4. C-Note with shorter port and lining lower half of cabinet inside

Using REW to measure a full range frequency sweep at the 75 dB reference level, there are only small differences in frequency response between the 4 test cases. Distortion measurements however prominently show a spike at around 1kHz. The unmodified C-Note has a fairly large spike and the other cases have none.

Conclusion in this round:

The cabinet modes likely excites the 700 Hz port resonance. Both the foam lining and the tuning change altered the cabinet modes. #4 had the best overall results.

EDIT: in preparing to post the graphs, may have to alter my previous conclusion. The improvements to cabinet modes are very apparent, the effect on the port resonance is not so clear. Will need to measure impedance to make a better determination. The Bassbox sim does clearly show a difference in the port resonance for the shorter port tuning.

The impedance curves below confirm the Bassbox sim. The first is the unmodified C-Note (#1) and the second is the modified one (#4):

Realize this is subtle, but no blips for modified C-Note...

 

[xarkkon]

Interesting that dampening would affect impedance. As a complete unlearned layman, impedance to me is something completely electronic and not related to the cabinet. That's pretty cool to know!

 

[Prana Ferox]

Did you have anything in the cabinet Amir measured? I just assumed anything this size got a handful of Polyfil thrown in.

 

[Rick Sykora]

Did you have anything in the cabinet Amir measured? I just assumed anything this size got a handful of Polyfil thrown in.

The speakers are built to spec. PE did not supply or specify any fill, so the C-Note was built without it.

 

[outlookrt]

Tempted by these. Been looking for a budget 2 way waveguide based design to try/learn from.
Has anyone every tried a version of these where the woofer is somehow flush-mounted? I suppose you would have to cut into the Waveguide.
And would have to somehow create the woofer rebate in the existing baffle... or maybe just easier to create a new baffle?
Not sure what benefits would be, beyond aesthetic i suppose and if worth the trouble.
Anyone tried them active? I have a miniDSP SHD and 4ch of amplification on hand, I imagine it would allow for easy fixing of some of the issues shown in the measurements (bass level etc).
Without having heard them, they do seem like a solid starting point for further tweaking/improvement/learning...

 

[Rick Sykora]

Tempted by these. Been looking for a budget 2 way waveguide based design to try/learn from.
Has anyone every tried a version of these where the woofer is somehow flush-mounted? I suppose you would have to cut into the Waveguide.
And would have to somehow create the woofer rebate in the existing baffle... or maybe just easier to create a new baffle?
Not sure what benefits would be, beyond aesthetic i suppose and if worth the trouble.
Anyone tried them active? I have a miniDSP SHD and 4ch of amplification on hand, I imagine it would allow for easy fixing of some of the issues shown in the measurements (bass level etc).
Without having heard them, they do seem like a solid starting point for further tweaking/improvement/learning...

Hi and welcome to ASR!

IMO, while a decent budget speaker to learn about speaker design, the C-Note drivers are pretty limited in range. The woofer has fairly high resonance and the tweeter is very high resonance. This means limited lower bass flexibility and limited ability to change the crossover point. I would not throw much time or money at them.

Could suggest some others, but before that, would help to know what your budget is and how you plan to use them?

 

[outlookrt]

Thanks for the welcome! I've been reading the forum for ages but never commented I guess!
I see what you mean regarding the drivers, makes sense. I suppose it's the form factor of the C note that appeals to me.
They would be used somewhat nearfield (<2m) in a small flat (with neighbours) and fairly close to the wall behind them.
I currently use Spendor s3/5r2 sealed passive speakers which work well in this setup, while I like them I'm curious what a small waveguided speaker would do in similar condition. I have a miniDSP SHD so active an option.
Bass output isn't a huge concern, and would be helped by near wall placement.
Budget-wise it's early days. Let say <£300 would make it 'cheap fun' for me. Closer or over to £500 doable but would require a bit more commitment on my end.
Sorry if this belongs in a diff thread or a PM, and thanks!

 

[Rick Sykora]

Thanks for the welcome! I've been reading the forum for ages but never commented I guess!
I see what you mean regarding the drivers, makes sense. I suppose it's the form factor of the C note that appeals to me.
They would be used somewhat nearfield (<2m) in a small flat (with neighbours) and fairly close to the wall behind them.
I currently use Spendor s3/5r2 sealed passive speakers which work well in this setup, while I like them I'm curious what a small waveguided speaker would do in similar condition. I have a miniDSP SHD so active an option.
Bass output isn't a huge concern, and would be helped by near wall placement.
Budget-wise it's early days. Let say <£300 would make it 'cheap fun' for me. Closer or over to £500 doable but would require a bit more commitment on my end.
Sorry if this belongs in a diff thread or a PM, and thanks!

Yes, best that you PM me. Now that I can know you are in UK, there are definitely better options.

 

[Colonel7]

Next round update...

Conclusion in this round:

The cabinet modes likely excites the 700 Hz port resonance. Both the foam lining and the tuning change altered the cabinet modes. #4 had the best overall results.

EDIT: in preparing to post the graphs, may have to alter my previous conclusion. The improvements to cabinet modes are very apparent, the effect on the port resonance is not so clear. Will need to measure impedance to make a better determination. The Bassbox sim does clearly show a difference in the port resonance for the shorter port tuning.

Thanks Rick. I'm building this now and am going with your #4 recommendation of sonic barrier and shorter port. Question on port length though - you did shortest possible port at 4" while the original build was 7" I believe. In any of your sims and experimentation was there a better compromise length between punch/tightness of bass and lower Hz at say 5-6"?

 

[Rick Sykora]

Thanks Rick. I'm building this now and am going with your #4 recommendation of sonic barrier and shorter port. Question on port length though - you did shortest possible port at 4" while the original build was 7" I believe. In any of your sims and experimentation was there a better compromise length between punch/tightness of bass and lower Hz at say 5-6"?

If you pick a middle port length, you get the changes you would expect - in between. If I recall this is an adjustable port. If you want to try different lengths, just masking tape the port extension tube. TBH, I do not have enough experience with this speaker to base results solely on the sim. Suggest you give a listen and see what sounds best to you.

 

[Colonel7]

If you pick a middle port length, you get the changes you would expect - in between. If I recall this is and adjustable port. If you want to try different lengths, just masking tape the port extension tube. TBH, I do not have enough experience with this speaker to base results solely on the sim. Suggest you give a listen and see what sounds best to you.

Thanks for the advice Rick. Went with 4" which sounds very good to me near field, which is how I've decided to use them - really enjoyable

 

[RoyB]

Here is an update on the C-Note kit I just built.....My kit came with plenty of wire, banana jack binding posts and screws. Only thing I needed was glue and lots of clamps. (Although lots of folks build these with duck tape or masking tape to hold together while glue dries.

The MDF parts I received were 100% perfect. I did not need to even touch them with sandpaper. The router bits must have been sharp when the CNC machine made these parts.

I glued and clamped the cabinets together at 8AM and I was listening to the speakers at 8PM the same day.

I used TiteBond glue for the cabinet and Industrial Strength Hot Melt Glue for the crossover components mounted on an ABS plastic board. The board was Hot Melt glued to the bottom of cabinet.

I covered all interior surfaces with 2" of Pink Fiberglass. Not glued to cabinet but tightly fitted.

I did not use the extension of the bass port.

Sanded and awaiting paint.

The final comments..... In a word "FANTASTIC".......I compared them to KEF103.2 and B&W DM601......My wife and I agree they are 98% of the B&Ws and 95% of the KEFs sound quality. Simply amazing for $109!

LIKES: Great imaging when tilted slightly inward....Excellent bass response when 24" from rear wall (24 X 12 X 8 room)......Excellent vocal response

DISLIKES: Very inefficient.....Required about 20% more power from 150W/ch amplifier (Yamaha M-45)

Note: I used them with and without a B&W subwoofer. At one point playing some 80s rock I was impressed with the bass response and thought the subwoofer was on. It wasn't!

I wonder what a stack of these would sound like?

 

[RoyB]

Added to the notes above......I do not posses any speaker test equipment except a Sound Level Meter (left over from my sound reinforcement company of many years ago) and my 68 year old ears. To test speakers I use a set of B&W DM601 and KEF 103.2 as a reference.
I use a simple speaker selector switch to AB the speakers I'm "testing" against either B&W and/or KEF.
I've now tested a whole bunch of speakers I own or borrowed, Polks, ELACs, Boston Acoustics.......All pale when compared to the "reference" speakers....But the little C-Notes stayed right with them! I'm totally blown away by their performance using my God given test equipment....