Sunflower Redux, crossover questions

[saroumanjs]

Hi!

(full story first ;))
I'm planning to build the Sunflower Redux from Paul Carmody, it's my first DIY speakers project and I've no so much skills in electronic (basics things). I'm 25 years old, really concerning by improving the sound of all my music style (from Irish traditionnal music to recent eletronic mix, industrial metal include) with all financial and skills possibility, after recomposing and rewiring my rega planar 3 turntable, I decided to change my JmLab speakers. I was trying to purchase the parts here in France but some parts were missing in my "favorites" stores. That's why I decided to command everything in "one shot" from Parts-express, but the electrolytic capacitors of 100 µF are (for moment) out of stock.

That's why I was searching if the possibility to change with an "higher class" capacitors, like the dayton metallized poly. cap, reading that it will be not only ok, but theoretically better, I decided to change all the 12, 33 and 68 µF capacitors (listed in the Paul's BOM) with the µF equivalent dayton polypropylene cap (not so much expensive, unlike Z-serie from Jantzen audio).
I think it's ok for the capacitors, but I'm filling so stupid ("The best is the enemy of the good."), because I readed on blogs that the air core inductors are (theoretically) better than iron core, so, falling in the "best" trap, I decided to change the two original Erse iron inductors (4 and 8 µF) with the air cores Jantzen 18 gauge equivalent.
I received everything yesterday and I was confused when I read another technical specificity on the inductors that I missed on the web: the DCR, which pass from 0.39 and 0.54, to 1.15 and 1.75 ohms... After some research it seems that it can really change the Xover! Now I've in hand the P.E. catalog and understand better what is the "8.2µF P-core" option in the Paul's list, another inductor with a low DCR.

My questions are:
is there a problem with the capacitors change?
is there a problem with the inductors change? (I think it must be fixed) So, I can search an equivalent in Europe with the Erse Iron inductors, or is there a better (don't smack) option which can improve the sound (Jantzen P core? Mundorf?)? I see must 8.2 and 4.7 or 3.9 ohms DCR than 8.0 and 4.0, how to choose?

I know that it was very stupid to change the list as a newby, but, the 'basic' values were respected and I don't wan't to change these futur speakers in short time, I've other "sounds elements" to improve after, when I see the prices a little more expensive I was truly thinking improving the crossover . I was trying to mix all the good things I read on multiple website. It just begin with a out-of-stock electrolitic capacitor... it's true they are not good:p!


By advance, thanks


Best regards from France, sorry for my language lvl...

PS: for others french readers, don't forget that you will have to pay the TVA (french taxes) at the reception of the package... the high price of the shipment don't contain it, it's just because you truly will receive it in the next 4 days!! I was thinking it -_-, it's my first international non-ebay purchase. UPS guy::D "hi, I have a package for you, you must pay 130 € for the taxes :p XD" me: "what the' ?.......ok -_-"

[Chris Roemer]

Re: Sunflower Redux, crossover questions

The cap change will be no problem.

W/out looking at Paul's XO, I can tell you that a higher DCR on a tweeter shunt coil (to ground - or, in parallel with a tweeter/mid) will not be a large deal, BUT, adding an ohm (or more, or even less) of DCR to a "series" coil (on a woofer or midrange) WILL definately change the overall sound of the system. In general, the higher resistance will drop the volume of that driver. It can also change the way the woofer acts in the particular box it's going in.

BUT, If I were you (and you don't mind experimenting), I might consider just using the coils you bought (if you already have them) but with foreplanning so that you'd be able to swap them out later w/out too much trouble, IF you decide the system doesn't sound "right". You certainly won't wreck anything.

Chris

[Paul Carmody]

Re: Sunflower Redux, crossover questions

Chris said exactly what I was thinking. The DCR change wouldn't really matter much in a shunt circuit, but it could have an impact on the woofer coil. But there's no harm in building what you have, and when you get the chance, swapping in more correct parts.

Also, a little tip you could have used in hindsight. If you can't find a certain value capacitor, you can use two smaller values in parallel to achieve the desired value (ie: 50 uf + 50 uF = 100 uF).

[thekorvers]

Re: Sunflower Redux, crossover questions

Monsieur Sarouman: Bienvenue sur le forum!

[saroumanjs]

Re: Sunflower Redux, crossover questions

thanks for your advices!, I will keep these inductors and certainly change later, for moment I need to keep my money for the construction, for the future which values are best? 3.9 and 8.20mH Jantzen P-core? (I don't find Erse dealer here)

I forget to post the crossover schem for those who don't know the Sunflower redux: (inductors concerned circled in pink)


Thx for the tip , I understand the pictures seen with 3-4 capacitors glued together! The dayton poly. 100µF is much much bigger than 2 electrolytics! I will certainly separate the crossover in 2 parts (bass in the bottom of the cabinet, medium + tweet on the cabinet).

[Chris Roemer]

Re: Sunflower Redux, crossover questions

I simulated a crossover simulation for this case. Your 4mH coil swap also should be NO problem. The higher DCR basically has an effect on the mids, but it's in an area way below where they've crossed to the woofer.

The 8mH coil, OTOH, probably will be a problem for you. You've added 1.2 ohms of inline resistance to the bass, and it also has an effect down low, except that it's in the predominant range that you're using that driver in. In short, your system response above 200Hz will mimic Paul's XO, but below that point you'll be losing about 1dB all the way down, with the worst range being a -2dB loss in the range from about 80-100 Hz. There's typically a LOT of bass info right in that range.

So, I wouldn't sweat the 4mH coil you bought, but if your bass seems weak (once you get these built and auditioned, where you intend to listen to them), you'll be able to boost the bottom end by 1-2 dB by swapping out that air-core. The 8.2mH P-core will be an acceptable substitute for you. I also just wanted to make sure that you saw that the cap (on the mids) that's in parallel with the 1.5mH coil, - is VERY small. Be sure you're using a 0.10uF cap here, and NOT a 10uF cap. I know you European guys are used to seeing a "comma" (,) for decimal places, where we use a "period" (.).

Chris

[saroumanjs]

Re: Sunflower Redux, crossover questions

Happy new year to the DIY community!
Thank you Chris for your simulation , for moment the placement will be very bad, so I will keep the air core, but I will certainly move out in the next year and search an apartment with an adapted listen room, this time I will certainly change the 2 bass cores

2014 will be first the Sunflower Redux year to me, step by step I'm finishing the box with a friend, here is some pictures of the project:

design research on Illustrator, I use 2 different grey but in reality I will paint it with 2 blacks, one mat and one satin


Construction

during the first round cut, I used bad measurement... recover with "Sintofer" (a white mastic)


front panel glued with the bass box


tweeter crossover, can you confirm that it's OK?:


medium crossover, same question :p:

[saroumanjs]

Re: Sunflower Redux, crossover questions

and finally, last step done:

more soon!

[saroumanjs]

Re: Sunflower Redux, crossover questions

up , I soldered only one crossover, can you (any one better in electronic than me) confirm this work?)

[Chris Roemer]

Re: Sunflower Redux, crossover questions

Looks good to me. Don't forget proper driver polarity.

[Melby Audio]

Re: Sunflower Redux, crossover questions

Awesome baffles! Very cool.

[saroumanjs]

Re: Sunflower Redux, crossover questions

thank you guys , I will certainly finished the work next week (I hope)

[morris]

Re: Sunflower Redux, crossover questions

Looks like you have countersinked the front of the woofer holes and also chamfered the back on them. Do you think you have enough "meat" for the screws to hold your drivers? Nice build so far!

[saroumanjs]

Re: Sunflower Redux, crossover questions

Thank you! Yes, this is what I have done, for the tweeter and medium the thickness is 10mm ("decorative plate") + 22mm (true front panel), I have countersinked 4mm in front, keep true 5-6mm (at 90°) and chamfered (at 45°), I finished by hand because the tool was too short to chamfer all the rest (10+22-4-6=22mm to chamfer, 20 with the tool, rest by hand). For the bass, I have "only" 22mm of thickness, I do the same but chamfered (22-4-6=12mm) only with the router.
I decided to chamfer after reading this: http://www.troelsgravesen.dk/chamfer.htm
I suppose this is important for this half open baffle.So, I think there is enough "meat", I will use 8x3/4" screws for all drivers, the screws are approx 1 cm far from the internal cut, I have aprox 1,6 cm of thickness at minima.

[saroumanjs]

Re: Sunflower Redux, crossover questions

Final view of all crossovers, I was surprised by the mecanical resistance of the silicon mastic (I try to take off, without success, the big medium coil). I've planned to use 3x1.23mm² silver-copper ptfe wires for medium and bass, 2x1.23mm² for the tweeter