C-Note Speaker Kit Major Modification???

[mtg90]

While I am gracious you feel that way about the design, I'm not sure what parts you ordered where it cost $200, I just added up the current cost of the crossover components for the Nexus TM and arrived at only $33.27 per speaker.

 

[Robski]

To install the larger tweeter, I lopped the ND25 tweeter off the wave guide and siliconed the ND28F-6 in it's place. It fits exactly the same and one would be hard-pressed to see any difference once installed.

The extent that Matt went to w/ the X-over probably tells us something about the original C-note's

I think you aren't making a sensible comparison.
The work Matt did isn't directly applicable to the C-Notes as it uses a completely different tweeter, and your wave-guided, siliconed, 'Franken-tweeter', as interesting as it is, is a different animal again. The different cone materials in the DS135 (Nexus) and DSA135 (C-Note) probably make them less than comparable, too.

You don't say what you find unimpressive about the C-Note.
If you told us that maybe we could understand what you are trying to achieve with the new xover.

I will have to look into the Nexus series.

 

[Trdat]

I like this idea of adding a 8 inch woofer, perhaps crossed over at around 300hz/400hz and you won't need a a directivity match at that point with only a high and low pass and a match with the SPL. Sounds easy enough, but I have no idea how to do it. That should give a decent bookshelf speaker at low cost as essentially were keeping the original design.

What I'm confused about is why modify the original crossover when the measurements were decent enough? The abovementioned I get but changing the crossover, kind of defeats the purpose. Have we identified from where the 700hz resonance is coming from?

 

[Robski]

Have we identified from where the 700hz resonance is coming from?

Wasn't the resonance issue with the Nexuses, which was fixed?

I wonder if an 'unsuitable' crossover might make the Al cone of the DSA135-8 in the C-Note 'ring'.
Just something I picked up from building a Carmody Isetta (https://sites.google.com/site/undefinition/portable-and-tabletop-speakers/isetta).
He found the the HiVi B3N rings and needed more filtering to counter it. I built the original Fountek FE85 version as I found a pair, despite them being discontinued.
Personally I am a curmudgeonley, traditional, old so-and-so and I prefer the look of the Founteks to the HiVis, unlike Paul C himself.

 

[mtg90]

Wasn't the resonance issue with the Nexuses, which was fixed?

I wonder if an 'unsuitable' crossover might make the Al cone of the DSA135-8 in the C-Note 'ring'.
Just something I picked up from building a Carmody Isetta (https://sites.google.com/site/undefinition/portable-and-tabletop-speakers/isetta).
He found the the HiVi B3N rings and needed more filtering to counter it. I built the original Fountek FE85 version as I found a pair, despite them being discontinued.
Personally I am a curmudgeonley, traditional, old so-and-so and I prefer the look of the Founteks to the HiVis, unlike Paul C himself.

On the Nexus TM the response peak in that region (~900hz) was a combination of a on axis peak from baffle diffraction and port resonance, not the driver itself. I suspect it's a similar source for the resonance on the C-note and the odd behavior seen between 700-900hz on the directivity plot points to port resonance as well.

Typically the ringing issues with aluminum cone drivers occur near their breakup region, while there is an optional capacitor for the C-note crossover to act as a tank filter across the low-pass inductor for taming the cone breakup resonance there is nothing additional in the crossover that does not exist on the Nexus TM which would cause additional ringing if used. That said the Nexus crossover is designed for different drivers and cabinet so I don't recommend its use for modifying C-notes and can't help but think it would make the response worse then the original crossover so I am surprised motomech felt it made an improvement on his modified C-notes.

 

[Robski]

Thanks for that.
Very enlightening.

It's still very early days in my learning about speaker design.

BTW I did put the extra 0.22uF cap in my C-Notes after I saw it recommended by the designer, Jeff Bagby, when I was doing my initial research into building a pair.

 

[motomech]

First off, I would like to apoligize to the designer, even though I used an air core inductor and purchsed a different port tubes (did not use) and the pre-made PCBs, the entire parts cost was less than $100. Not sure why I thought they were more expensive.
Secondly, it was thoughtless of me to "hack" someone elses design and I understand how doing so could ruffle some feathers.
In my defense, I'm retired living on a fixed income (actually, it's shrinking), I was just trying to do something w/ a pair of speakers I wasn't using, I certainly wasn't trying to "imporove" the Nexus. I also suffer from "trinkeritis".
As far as my modified C-note and the Nexus TM being two entirely different speakers, well, I looked at P.E.'s parameters for the DSA and the DS woofers before I started and i think it would hard to find two "different" drivers that spec'ed more closely. I didn't think it be worth spending the extra $70 for what I was trying to do.
An I did use the ND28F-6 tweeter, mounting it on the ND25's waveguide because that was by far to easiest way to use it in the C-note's box. I had no sonic exspectations and seeing how well it fit, I figured whatever the WG did for the ND25 woul be no worse or better w/ the ND28.
I reduced the C-notes box volume by 10% and while it is still a little larger that the specified Nexus volume, the two baffles are very close in diamensions.
I had no clue that what I was doing had such a great pontential for disaster. But I guess the Audio Gods were smiling down on me as these sound absolutely fabulous The woofer particually impresses me. I have usied different alum. coned woofers over the years (RS150 and ND140) and although I would never say "they ring" in a well designed speaker, there is something about them that never allows one to forget they are alum. A slight metalic after-taste if you will. There is none of that in my "Frankenstien" application. They are quite "snappy", go fairly low and overall, give these speakers a warm and enveloping quality I apprieicate in their desktop application. Likewise, the tweeter, while being "on-point", is slightly subdued, another plus in my application.
Bottom line, this was a fun and easy project that way exeeded my expectations, and I guess that is what matters to me.

 

[Robski]

Thanks for that.
Very enlightening.

It's still very early days in my learning about speaker design.

BTW I did put the extra 0.22uF cap in my C-Notes after I saw it recommended by the designer, Jeff Bagby, when I was doing my initial research into building a pair.

It was principally designed Chris Perez, actually.

Apologies Chris!

 

[scrubb]

Not a major modification, but I didn't like the look of the woofer frame simply attached at the surface. I routed around the woofer opening to a depth of about 3.5mm which included part of the tweeter's wave-guide. The woofer frame is now flush with the baffle and the wave-guide. It was nerve-wracking to route the wave-guide. I covered the opening with masking tape to keep particles off the tweeter surface and moved the router methodically. I don't know if this changed the sound much - I doubt it - but I like the appearance much better.

 

[Robski]

I believe the C-Note was designed specifically around the flush mounted wave guide tweeter and the surface mounted mid-woofer.
The resulting step together with the waveguide positioning the tweeter dome back a few millimetres gets the time alignment as they wanted it.
It isn't an accident.

Personally I like the quirkiness of the flush-to-surface driver overlap!
I have recessed all my other speakers' drivers.

But this is DIY so it's up to you.

IIRC Wharfedale use cutaway tweeter surrounds (ports too) to cram everything on to a small baffle so you are not alone.

 

[XMechanik]

I routed around the woofer opening to a depth of about 3.5mm which included part of the tweeter's wave-guide.

If the waveguide is routed, why not to align the tweeter with the front panel? I guess that sharp edge of the tweeter's flush, which seems a bit too deep, is causing a ripple on the spl (possibly narrowband) .

This metallic paint finish looks pretty cool!