Design calls for .7mh, is .68 OK?

[fazman]

Just finalizing my project with the Vifa P13 and the XT ring radiator. Found that I like the proven design of the Okara the best. My quick prototype revealed to me that this is a very neutral speaker , so it is this design I will end up with.

The low pass section calls for a 1mh and a .7mh inductor.
I will be ordering the parts from Solen and they have the 1 mh but not the .7 mh. Will a 6.8 mh be OK to use ?
Likewise the high pass calls for a 6.7 mf cap. Will 6.8 mf be good ?
I'd rather not bypass caps to get the value if possible so I can save precious space inside the cabinet. (plus I don't want to spend the extra money)
Also I noticed that all the inductors have resistors preceeding them. I assume it is the value of the DC resistance? Is this really necessary, or will I be alright without them?
The Okara uses 12 gauge foil inductors. As I am on a budget for this I was thinking of using 16 gauge air core inductors. Will all these substitutions seriously compromise the design? Sorry for the multiple questions, I want to get it right the first time and not have to reorder stuff again

[sberube]

its all a matter of how picky you are If you like doing things right and want to use their standard inductors (over the hepa-litz, I think they make more sens for low frequency crossovers, having one large gauge conductor) then I suggest you give them a call and ask if they'll make one of the specific value for you. I've been to their store, and I do believe they roll them on the spot. If not, I suggest you get a 0.75 and unwind it to 0.7.

There's a spreadsheet somewhere that someone designed for calculating how to unwind an inductor, I remember zaph had a link to it on his webpage, but I can't seem to find it anymore. You definately want to find that again if your looking into getting the propper value.

Hope this project is going to turn out nice.

[hongrn]

Passive components such as capacitors and inductors are all manufactured within certain tolerances, typically 5% or even 10%. Even when you use a LCR meter to measure these components, the meter itself has published tolerances. For instance, the Elenco LCM-1950 meter that I purchased from Parts Express has a resistance accuracy between 1 to 5%, and capacitance/inductance accuracies of 5%. So if your capacitor has a 5% tolerance, and your meter has another 5% tolerance, well you can do the math. Hope this helps.

Here's the link for winding your own inductor:

http://lalena.com/audio/calculator/inductor/

Capacitor codes for identifying tolerances:

http://www.montek.com/tutorials/cap_codes.html

Hong

[fazman]

Thanks for the replys, I think I'll end up using the standard 14 gauge inductors for the low pass and I will bypass caps with smaller film and foil to get the exact values. The picky part of me wouldn't have it any other way. Thanks sberube for mentioning it!

This always happens but,... just when I thought I had my design finalized I read info that makes me second guess it.
The Okara design calls for a .22 cubic ft. enclosure tuned to about 63 hz. That is approx. what my test enclosures are now but I read numerous suggestions stating that a good recommended size would be .38 tuned to 60 hz. (slightly larger)
Does this enclosure size call for deeper if not somewhat looser bass? I don't mind this so much as the P 13 lacks bass anyway.
Would the x-over values need to change if I went with the larger enclosures? or would the same x-over be good?
Any one have a thought on this?

[Salas]

When making personal speakers for critical listening of our music collection, I have found that use of say 0.68mH instead of 0.7mH can make a speaker lose magic.

[sberube]

Changing the volume of the box will definately make a big difference, but from what I understand (might be wrong here) only the low frenquency gain will change, your x-o point gain should stay the same. Although it might be possible that the entire range of your woofer's gain changes.

As for giving you a looser bass, I really don't think so.

BTW, if you haven't ordered your parts from solen yet, try this. Get a 47 Ohm resistor, and use it as a bypass on your inductor for your bass driver. Let me know what you think... It gave out some pretty interesting results on my part.

I also used a cascade (instead of just a bypass - eventhough bypass was already real cool) of caps for my tweeter (Vifa XT19 ring radiator) and was very impressed by the change. If you can/will afford very expensive caps, then it might not be worth it, but with solen chateauroux, its definately worth the extra $$ your going to pay.

Too bad your not in montreal, I could have lent you loads of components to do value testing in your x-o.

Good luck and let us know how it turns out.

[Audiophilenoob]

Originally posted by salas
When making personal speakers for critical listening of our music collection, I have found that use of say 0.68mH instead of 0.7mH can make a speaker lose magic.

you've got to be joking

do you buy 0.1% tolerance inductors or something??

what magic anyway??? all it does is switch a little on the xover point

[Bose(o)]

...and adjust the phase change, impulse response. Salas, also said that for "critical" listening that it can change the speaker's tonal quality or, magic. I guess salas has a very keen ear, I'm still working on it.

But then, a passive x-over smears and glitters phase and power all over the place, so then an active xo must be used. And then, and then.....oh no! I'm caught in the loudspeaker designer vortex!!!!

[fazman]

Originally posted by sberube
Changing the volume of the box will definately make a big difference, but from what I understand (might be wrong here) only the low frenquency gain will change, your x-o point gain should stay the same. Although it might be possible that the entire range of your woofer's gain changes.

As for giving you a looser bass, I really don't think so.

BTW, if you haven't ordered your parts from solen yet, try this. Get a 47 Ohm resistor, and use it as a bypass on your inductor for your bass driver. Let me know what you think... It gave out some pretty interesting results on my part.

I also used a cascade (instead of just a bypass - eventhough bypass was already real cool) of caps for my tweeter (Vifa XT19 ring radiator) and was very impressed by the change. If you can/will afford very expensive caps, then it might not be worth it, but with solen chateauroux, its definately worth the extra $$ your going to pay.

Too bad your not in montreal, I could have lent you loads of components to do value testing in your x-o.

Good luck and let us know how it turns out.

sberube, A 47 ohm resistor bypassed on the inductor? I would assume this would be to sove any baffle step issues? There is already a 19 ohm resistor bypassed for this reason. Wouldn't a 47 ohm really exagerate the BSC effect? I'll give it a try anyway just to see but I don't know...

When you say you cascaded the caps aswell as bypass them, do you mean to say that you put one after the other in series with each other? What exactly would be the reason for this?
Sorry for all the questions but I'm learning a lot from you guys (girls?)- don't want to be a sexist you know

[sberube]

no actually its not for BSC. Not that I know of... just a simple bypass (between both leads of the inductor). I think it'll make the lower frequencies take this path instead of the inductor path which will reduce the length of the path to your drivers which makes the bass more defined... clearer. Of course ever so slightly...

As for the caps, I bypassed at first (needed 11uF and used some combo to get there with a 0.47 film and foil) which sounded really good. But then what I did was to go with the following (in parallel):

6 uF 200Vdc
3.3 uF 330 Vdc
1.5 uF 400 Vdc
0.47 uF film and foil 630Vdc

It was really worth it.