Finished Zaphaudio b3s project :)

[jaygeorge1979]

I am finally done with the HIVI b3s project from zaphs web page, and i am very pleased...these things really do have clean sound...

you may remember all of my crossover issues/questions and such that i dealt with a few weeks ago...i avoided the issue and just built the filter as he showed just to see how it turned out...i thought maybe i could adjust the EQ on the minisystem enough to make this work, but i decided that this wasnt the best idea, so I have decided to start researching the most reasonable options for fixing this issue...

my search led me to the partsexpress Fmods, shown here:

http://www.partsexpress.com/pe/showd...number=266-256

would this be an effective solution? it seems a bit easier than designing one myself since finding the input impedence of the minisystem amp might prove to be more trouble than its worth...i would rather drop 25 bucks on this is i knew it would work...but it is a caraudio Fmod...would it work in this case?

PS thanks to all who helped me get this project rolling

[Bose(o)]

Isn't the so called FMOD just a passive line-level crossover? It doesn't require any power and it is inline with the signal before any serious amplfication stages take place.

If this is the case then you'd have similar types of impedance matching problems as building your own, only, it won't be optimal for your system. Impedance matching is really only stabilizing the circuitry to perform at it's optimal potential.

Anyway, please correct me if I'm wrong, which I probably am.

[jaygeorge1979]

yes, thats what an Fmod is

but when it comes time to choose which one i want, it doesnt have different ones for different impedences, they are all specified by their crossover freq and slope...

soo i was hoping it was kind of like a one size fits all kinda thing

[phidauex]

Well, one of those would work, but you don't want a 150hz low pass for the B3S! A 150hz high pass would probably be fine.

However, 25$ is a little 'up there' for passive line filters, seeing as how they are a jack, two resistors, and two capacitors each.

They are second order, passive line level cross over filters, which are very simple, and aren't hard to design.

Here is what I'd do... Chop up a simple interconnect (or make your own), and use a little piece of perfboard (or just in the air point to point wiring) to make the filter with the interconnect wired along it. I make little attenuators this way all the time to balance out channels or whatnot.

Passive line filters aren't perfect, but they are way better than a passive speaker level filters for something simple and cheap like this.

Check out this page for how to design the line level filter. Use decent metal film 1% resistors, and decent polypropylene film caps. They won't cost much, because they don't need high voltage ratings.

http://www.t-linespeakers.org/tech/f...ssiveHLxo.html

Good luck! I'm building three of the B3S speakers soon, once I get access to my friend's table saw and router.

peace,
sam

[phidauex]

More about passive line level crossovers: http://www.silcom.com/~aludwig/Sysde....htm#Bi_amping

[sreten]

Originally posted by jaygeorge1979
...would it work in this case?

Hi,

It would be useful if you describe the complete system
and how you intend to use the line level filters.

If the mini system has a line level input, and you are using
an active sub, and you are driving both from a line output,
then an inline high pass filter for the mini system will work.

/sreten.

[jaygeorge1979]

my mini system does have line level input, and i am using an active subwoofer, but not with the mini system...this is all for my computer setup, so i am using the front speaker output on my soundcard to run to my minisystem for the mids/highs, and the rear speaker output on my soundcard for the active sub...so im guessing the Fmod would work

and yes i know i need a high pass fmod, i just posted the wrong link....DOH!

i would rather design it myself, but last time i researched this it said i needed to find input impedence of the amplifier, and i didnt have the tools to do it, so i figured why not spend a little extra and get one thats already built....unless this thinking is frowned upon by the DIY community

thanks to all replies thus far

[Bose(o)]

I was trying to imply that you'd still have the same impedance matching problems with the Fmod as you would with any other PLL XO.

If you designed your own 'Fmod' you'd be at the same place as you would be with purchasing your own 'Fmod' except that you'd have paid more money.

P.S.,
You may consider 'borrowing' some $$ for the tools because if you're just entering DIY you'll eventually learn that you'll use them very, very often.

[jaygeorge1979]

for the Fmods tho, they dont specify anything about input impedence, so how would i go about choosing which one that works? there is only one high pass 200 Hz crossover that i see

so im asking how this differs from building your own...cuz to build your own the input impednece must be known, but to buy one, i cant find anything mentioning input impedence

[Bose(o)]

If you built your own you'd have the impedance matched exactly to your amplifiers and thus would have less distortion, clipping and more head room. UNLESS, the fmod that you buy happens to be designed for your amp's impedances.

From what I've read about the B3s, it seems that they are useless from 100-300Hz so maybe 200Hz. is not going to work.

Can your woofer produce some mid-bass into the listening area?