Modding c-notes

[greenskin]

Hi, I have a plan to buy the C-notes component set, but make a different enclosure, while keeping internal volume, port cross section and volume, and the cross-over circuit unchanged.

What I want to do:
- replace rear port by a front-facing slot port
- remove the overlap between the mid-range driver and the tweeter (so, basically, move the midrange driver 1cm or so lower)
- make the cabinet slightly narrower
- use 18mm (more or less 3/4 inch) MDF and and add an internal cross brace
- play with height and depth to achieve the same internal volume, and the same cross-section and volume of the port as the original.

I have to admit, I do not have any objective reasons to do this, except cosmetic preferences. So, what I am asking is this: is it likely that I'll badly screw up acoustic characteristics with this change? (I assume it will sound slightly different, I hope it won't be bloodbath)

[celef]

i do not know anything about c-notes, but in general, the results will depend on how meticulous the original design is you want to alter, if it is a sloppy design the outcome will be minor. like moving a port can have profound effect depending on how the internal layout is done, likewise moving drivers around and changing box materials and so on

[TBTL]

A port might leak midrange sound which becomes more audible if it is located at the front.
Removing midrange-tweeter overlap slightly increases their centre-centre spacing and therefore slightly degrades vertical dispersion.
Making the cabinet narrower can make the baffle step correction incorrect. Difficult to say as celef notes above. I think that this has the largest influence on the sound.


These changes will not screw up the sound.


What can screw up the sound is placing the speakers against a wall, if that is the reason you want to move the port to the front.

[xrk971]

Changing driver center to center distance and baffle width will change the crossover. You can change most other things but not the physical layout of CTC and baffle width/round over.

[greenskin]

Thank you both.

The speakers will probably be 30-40 cm from the wall, so, not ideal, but not the worst case either, I think.

The main reason for the change, really, is that the raw underbite in the driver positioning bugs me aesthetically, for some reason.

I take the point about the degradation in the vertical dispersion. Can I assume it will be be less severe the farther the listening position is from the speaker? Also, I am not building them as near field monitors aiming at a precise spot, but as general purpose speakers, to listen to some music while moving around the room.

Thanks again. The purpose of the project is to have a go at speaker cabinet making and finishing, without buying the premade kit. You reassure me that it probably will not be a pile of mess.

[greenskin]

xrk971 - thanks for the input.
Food for thought. How does the worst case sound like, speculatively?

[planet10]

Originally Posted by xrk971

Changing driver center to center distance and baffle width will change the crossover.

That was my 1^st thot as well. At the crossover frequency 1” is a huge distance. There is very solid reasoning for getting a tweeter as close as possible to the mid or midbass.

You are trying to reach a quarter-wavelength at the XO, almost impossible with a typical tweeter, and getting as close as possible helps solve issues with an XO where C-C is larger than optimal.

dave

[greenskin]

Thanks for the input, guys.

I guess, I will have to get ready to fine tune the cross over circuit after the build.
One more thing to try / learn ;-)

[jReave]

An alternative would be to router out the waveguide portion of the tweeter so the woofer fits flush with it. Just make sure you don't take out so much that you break the tweeter's seal with the baffle.

See this CC by Troels for an example. If you do it, I would suggest taping over the dome of the tweeter so it will remain free of any dust and debris as you make the cut.

Moving the woofer back to flush fit it with the baffle will also have a small effect on the sound but for this speaker and your listening habits, I wouldn't worry about it.

Also in general, if you change the baffle width by less than 10% the effects are usually acceptable. Adding more height to the speaker is also generally ok if you add it in at the bottom, or in other words you keep the drivers the same distances from the top of the front baffle as the original.

[greenskin]

Also in general, if you change the baffle width by less than 10% the effects are usually acceptable. Adding more height to the speaker is also generally ok if you add it in at the bottom, or in other words you keep the drivers the same distances from the top of the front baffle as the original.

I think, actually, this fits my case pretty well - the overall baffle width in the standard c-note is 190,5mm (7,5 inches). The full diameter of the driver is 134,9mm (5,3 inches). I planned to remove 16 to 18mm (8-9mm each side), so it would fall under 10%.

The routing out the overbite is a nice approach, looks very clean and integrated. I'll think about it. Thanks