Zaph zrt advices: components and building doubts

[francorovereto]

Hi all,

I am beginning to build a thrusted project, Zaph ZRT two way, and *obviously* I wish to make all by myself, without madisound cabs.

Now I have some doubts about cabinet sizing and crossover components. I will be a little schematic here, hope this don-t hurt.

1. Cabinet. I would go traslam, a la Magico Mini, tower version. This is leading me to madness, couse I wish let the baffle dimensions identical as the original BUT this maybe excludes the possibility of a largely rounded baffle. I would make substantially an 1 inch radius roundover but how can I obtain the effective, corrispondent dimension of the original project baffle width (sharp edges)?
Should I consider an average point? only the external distance between the side walls?
Please give me any imput about this.

2. Crossover coil(s)
I am choosing the right caps and coils. The original Zaph's scheme claims for a 2,7 mh coil for the woofer, with a rdc of 0.168 ohm. Essentially he go for the cheap way, and I could agree but living in Italy I must use other stuff, not exactly with same specs.
I could go essentially for this 4 solutions>

a. munforf flat foil inductance. Expensive and with an rdc of >0.30 ohm. Worth the extra cost or will simply ruin the damping of the woofer (double the rdc) without evident benefits?
b. Intertechnik generic ferrite coil. wery low rdc (.11). Maybe too much low? Could be a problem?
c. Intertechnik tritec litz hq ferrite coil. Fast right rdc (.15), a little expensive but affordable.
d. Mundorf zero ohm coil. Hilariously low rdc, expensive as a mid level tweeter but maybe a good way to obtain fast, damped bass. Maybe definetively overkill anyway.

What would you use? Eventually a 5th option is welcome.

3. Crossover/ general.
I think going with obbligato caps (tweeter series) and lesser poliprop from jantzen (crosscap) or similar. I have read a lot of different opinion about parallel caps... some people claims for the absolute importance of HIGH quality caps in this places too....other prefer to alternate very good ones in series with cra**y ones in parallel.
What do you think about?

I would hear any feedback, considerations, advices from diyers and people more expert than me.

thanks!

 

[francorovereto]

Ps> sorry for my poor english!

 

[sdclc126]

1. Translam cabinets look nice but are a lot of work - buy or build a traditional, well damped, well braced cabinet and save youself some headaches.

2. & 3. Use the exact component specifications as in the design, but forget the ridiculously priced boutique stuff - you will not hear a difference.

 

[francorovereto]

thank you for the quick reply!

Essentially, i would go translam couse i am bored of the typical rectangular box and building a complex thing will prolong my enjoyment! diy for me is also making a beautiful thing too. And MAYBE this beautiful thing will sound a little better than a regular box. Dunno. Doesnt matter to much.
Anyway,
Given the sad reality (I can't find here exact values) what could be the effect REDUCING the rdc of the coil? Could the Crossover be altered or changed?

 

[sdclc126]

Then go translam, by all means - just keep the internal volume the same.

As for the inductors - best to buy ones that are over specced and then reduce the size to correct by removing lengths of coil. You can use this calculator here:

Inductor Designer / Calculator

Click on the Help button below the value inputs and look at the table to see how to match the dcr as close as possible.

 

[francorovereto]

ok, sorry but I think that my bad explanation has led to misunderstanding. Naturally 2,7mh is a common value and I can easily find it. Is the resistance value the one that differs. A bit less or a bit more, accordingly to examples i made in the first post. I know that more R lead to a more sloppy, muddy bass and less control of the woofer, and reducing R can better this area. My question is about the possibility to have bad effects reducing (only a bit ..say 0.05 ohm difference) the coil resistance or the difference/effect is totally negligible.

 

[jwmbro]

thank you for the quick reply!

Essentially, i would go translam couse i am bored of the typical rectangular box and building a complex thing will prolong my enjoyment! diy for me is also making a beautiful thing too. And MAYBE this beautiful thing will sound a little better than a regular box. Dunno. Doesnt matter to much.
Anyway,
Given the sad reality (I can't find here exact values) what could be the effect REDUCING the rdc of the coil? Could the Crossover be altered or changed?

If the DC-resistance is too low, that's easy to fix. Just ad a series resistor to bring it up to the desired resistance. Simple addition of resistances when in series.

 

[francorovereto]

muble muble muble.
Ok. This is a solution i could go for.
I have seen that madisound sells two crossover, one with a flat foil copper coil and one with sledgehammer coil. I doubt that the rdc between the two coil is the same... so i had argued that be absolutely precise about this value is not worth the pain of find a 0.05ohm/hi wattage resistance or make it with more resistances paralleled.
I am still unhappy thinking to add a resistor in series with the woofer.
I was considering that a lower rdc coil could be conceptually better for this duty, but i was unsecure about the possibility of change, altreing rdc of the coil, the crossover slope , something in bsc or things like this.
At this point, this could be more a curiousity than a pratical issue.. knowing anyway that caps tolerances and other 1000 variables should be anyway considered. And accepted consequently. Obsessive hifimania can lead to severe health problems!!!

 

[tamule]

hi franco , I strongly suggest reading Zaph's "2-way options" for this build. I ended up cutting out the woofer coil after completion and unwinding it to 2.2 mH. At 2.7mH the midrange seemed a little recessed on most pop-rock cds in my room.
For the woofer coil I used 10 ga air-core from North Creek Music.
I've had these speakers 6 months now after Maggie 3.6Rs and have never looked back.
regards,tom

 

[francorovereto]

Right, i've read this part of Zaph's reccomendations but i'll wait to hear the results of original values in my room and then eventually i'll make changes according to my tastes. Probably i'll go for reducing the coil value anyway, I normally like a more forward-sounding speaker. Once the burn-in has ended, i'll go for tweaks (woofer coil and probably tweeter series R adjustment).
You wrote that in your speaker you use an (huge) AIR coil. This coils are really expensive and really thick wired... why have you choosen this way and not a cored coil?
Are ferrite core/transformer coils not enought for your purposes? Do you think that the difference (distortion, core saturation) is worth the extra expense?
Thanks for your feedback.

I'm still curious about the influence of coils rdc vs crossover's slope and woofer behaviour!
ciao

 

[giralfino]

I'm still curious about the influence of coils rdc vs crossover's slope and woofer behaviour!

Download Passive Crossover Designer (free) and play. But if you are lazy here are some results: at 200Hz moving from 0,17 to 0,5 Ohm the SPL will be lowered by 0,4 dB, at 100Hz and 1KHz the difference is only of 0,1 dB. I frankly doubt that you can hear 0,4 dB in a blind test.

For a woofer like the scan-speak I would opt for an air core inductor. Large value inductors with large diameter wire are expensive, but a 2,7mH 2,0mm (0,33 ohm dcr) air core inductor costs about 50 Euro, that is a fraction of the cost of the woofer. You can try a lower cost ferrite core and decide if you hear the difference (you can find a 0,1-0,3 ohm ferrite core inductor in the 5-15 euro range).

Ralf

 

[sdclc126]

If the DC-resistance is too low, that's easy to fix. Just ad a series resistor to bring it up to the desired resistance. Simple addition of resistances when in series.

Yep - better advice than mine - i was hung up on modifying an existing coil.

 

[tamule]

You wrote that in your speaker you use an (huge) AIR coil. This coils are really expensive and really thick wired... why have you choosen this way and not a cored coil?
Are ferrite core/transformer coils not enought for your purposes? Do you think that the difference (distortion, core saturation) is worth the extra expense?

yes -they were expensive and worth it. I wanted air-core after reading about hysteresis losses and the ability of coil to change it's magnetic field with the signal. As long the desired DCR was met-I was willing to pay.
I wonder if any hi-end manufacturer uses 5- 8 lb inductors with their woofers?

 

[francorovereto]

Thanks!
I'll try with an inexpensive ferrite core (low rdc) and then, once found the right amount of bsc and the impedance i want, i'll spend more money and go for air inductors. I think mundorf air coils, 2,5 or 3 mm.
Flat foil inductor are way expensive, don't know if it's wort the results... round wire should do a nice work anyway.
Choosing the right balance for crossover components is ever a pain for me. I'm tempted by high-end stuff, but I don't want to waste my money if the results are totally marginal or if I could spend it more effectively for more important parts of the speaker. (wiring, binding posts, "exotic" damping sheets, etc etc.)

 

[francorovereto]

ps: what about the question n. 1? How should I consider the baffle widht/height adding a consistent roundover to the edges?

In this case, should I consider to mantain the original (given) widht on A,B or C?

 

[francorovereto]

Ps: You all are very nice answering patiently to my doubts.

 

[giralfino]

The width/height is C.

Ralf

 

[francorovereto]

The answer is: C! Thanks. But let me be "avvocato del diavolo" for a minute.
Giralfino you say that the significant dimension is taken when the edge's curve reach 90 degrees, perpendicular to baffle. In this forum I have read in some debates that first diffraction effects begins to appear before reaching c, but the transiction to full radiation is way smoother.
Ok. But:
Given a bsc designed for a sharp edge (with "C" dimensions), the resulting diffraction behaviour of a rounded edge should be a little different I guess. Maybe a resulting smooth dip/peak in the response?

 

[francorovereto]

Anyone here?

 

[francorovereto]

?