Recommendation for a crossover choke

[murphythecat8]

Actually after looking at the values of components in the crossover in the first post, I wonder whether they are correct. The lpad resistors seem to be pretty close together in value, and 1.5uF is an awfully small value!! What is your intended crossover frequency?

Tony.

5khz.
I'm using the pro-38 with a audax pr170mo driver crossover design...

 

[murphythecat8]

It is more important to maximize the quality of the 1,5uf capacitors.
Just my 10 cents.

ok, so the 1.5 uf cap is the most important in ym crossover? I plan on using mundorf m-cap, but if you say its the most important cap, I shall go with the supreme for the 1.5uf...

so in your opinion, I could go with the 7$ coil and it shouldnt influence much the sound? 0.47mH 18AWG Air Core 0.32 ohms DCR Coil 1281 0.47mH 18AWG Air Cored Induction Coil [3140] - $7.50 : SpeakerBug, capacitors, inductors, resistors, crossover parts, speaker supplies

 

[murphythecat8]

I wouldn't call ~$17 a very expensive choke esepcially since it has a DCR of 0.16ohms which is decently low.... yes you could go with the 20ga one at $5.00 but it has a DCR of 0.47 ohms, which I would think will start to make a difference. But obviously there is a point of diminishing returns

Attached is the sim from my crossover for my mtm's. The shunt coil is in a 3rd order network, and is 180uH and had dcr of 87 milli ohms. If I increase the DCR to 470milli ohms I get the blue curve. It may not look that significant but the is 10db more energy getting through to the tweeter at 100Hz with the higher dcr coil. That is what Simon, and Lynn in the thread I linked to are saying is really bad. In a second order (electrical) network the difference may be greater.

Tony.

Very interesting. To be honest, I have the money to go with the 4x 17$ coil, but I have to ask, what about if I go in-between the 5$ coil and the 17$. the 13$ 0.47 mH 15AWG Air Core 0.20Ω DCR 1518 Induction Coil 15 AWG .47mH Induction Coil, Inductor, Air Core, crossover [2625] - $13.20 : SpeakerBug, capacitors, inductors, resistors, crossover parts, speaker supplies looks like a good option? But if you believe that it will affect the sound, I will not hesitate and will spend 20$ more, not a big deal!

 

[pdul]

The in between coil seems like a good option combined with as good a capacitor as you can affort, since its in series with the tweeter. If you have a series resistor, then use a non inductive 7-10 watt

 

[wintermute]

Yes the 15 gauge one is a good option as it is only marginally higher DCR than the 14Ga one. As I said you reach a point of diminishing returns.

The problem that can manifest with high dcr shunt coils will generally only be noticable when the speakers are driven hard (ie high volume levels) and is an unpleasant distortion from the tweeters. So if the speakers will not be run at high levels then it is probably less of a concern.

I wasn't sure about the values in the crossover as 1.5uF seemed a pretty small value but 5Khz is a quite high crossover point, also is the tweeter horn loaded? that would make a difference too Also if the tweeter is much higher sensitivily? I thought that the resistors would create quite a high cut lpad. do you have links to the speaker I googled pro-38 but didn't turn up anything

Tony.

 

[ScottG]

Those last few sources were from Australia.. shipping to Canada would be absurd.

Expensive:
Jantzen 0.47mH 16 AWG Copper Foil Wax Coil 255-508

Cheap (but still good):
Jantzen 0.47mH 18 AWG Air Core Inductor 255-228
(..and you can always "pot" it yourself.)

Middle of the Road:
Jantzen 0.47mH 15 AWG Air Core Inductor 255-408
(..again, pot it yourself.)

 

[wintermute]

yes I wasn't suggesting that he should purchase them from Aus (the "something like this" was supposed to indicate that), I was just demonstrating some options for good quality reasonable priced coils I probably should have said to try and source something similar locally.

Tony.

 

[Pano]

Get a Jantzen from P.E. (see above) or buy the choke from Solen Canada. Easy, peasy.
www.solen.ca

 

[murphythecat8]

Those last few sources were from Australia.. shipping to Canada would be absurd.

Expensive:
Jantzen 0.47mH 16 AWG Copper Foil Wax Coil 255-508

Cheap (but still good):
Jantzen 0.47mH 18 AWG Air Core Inductor 255-228
(..and you can always "pot" it yourself.)

Middle of the Road:
Jantzen 0.47mH 15 AWG Air Core Inductor 255-408
(..again, pot it yourself.)

that is really kind, thanks for the research, I'll take the middle of the road just to be sure and I hope it will be okay.

this is the project. http://www.exdreamnet.de/forum/user/Franky/Pro38_Art.jpg

 

[Pano]

Are you using this fro L1 or L2? See the DCR of the coils in your project.
You can find what you want in either Jantzen or Solen to match the DCR.

 

[murphythecat8]

Are you using this fro L1 or L2? See the DCR of the coils in your project.
You can find what you want in either Jantzen or Solen to match the DCR.

ill be using two coil per speakers, was that your question?

 

[giralfino]

The design calls for a L1 of 0.43mH and 0.6 Ohm, and a L2 of 0.5mH and 0.2 Ohm. Using a coil of 0.47mH for both L1 and L2 means an error of up to 10%, more than I would do. From the Solen catalog you can find a 0.43mH coil (0.44 Ohm - 20AWG), and a 0.51mH coil (0.22 Ohm - 16AWG), that are a good match with the design.
Ralf
(Disclaimer: I'm not affiliated to Solen in any way)

 

[Pano]

I was looking at the 3-way crossover you linked to. It uses 4 inductors per channel. Was just wondering where you were putting this one. L1 (tweeter) or L2 (mid series)?
Or are you doing something else?

 

[murphythecat8]

wow, I though I could get away with two 0.47, thanks... Solen is too expensive when I can get 5$ inductors with almost the same spec. music is not to be played loud... what do you think if I go with jantzen.
so, for
L1: Jantzen 0.44mH 18 AWG Air Core Inductor 255-226
L2: Jantzen 0.50mH 18 AWG Air Core Inductor 255-230

Pano, I'm going active in the bass, so only need crossover for the upper speaker.

 

[Pano]

Get the 0.5 for 0.47 mH and use as is, or unwind it a bit. Jantzen is good stuff.
When I looked at Solen, they were the same price. Am I wrong?

You are doing just the tweeter, or tweeter and mid?

 

[murphythecat8]

Get the 0.5 for 0.47 mH and use as is, or unwind it a bit. Jantzen is good stuff.
When I looked at Solen, they were the same price. Am I wrong?

You are doing just the tweeter, or tweeter and mid?

The crossover is just for the low pass on the mid and highpass for the tweeter. My high pass on the mid is in my preamp and the bass is active.

Why shouldnt I take the exact inductor I need instead of having to unwind the inductors...

Can anyone tell me if the inductors I just propose would be the closest that I need for my project?
L1: Jantzen 0.44mH 18 AWG Air Core Inductor 255-226
L2: Jantzen 0.50mH 18 AWG Air Core Inductor 255-230

 

[Pano]

Thanks for the clarification.

The values you show will be right for the parts you want to build.

 

[giralfino]

The crossover is just for the low pass on the mid and highpass for the tweeter. My high pass on the mid is in my preamp and the bass is active.

Be aware that it is difficult to replicate actively a passive design(*), you need at least the transfer functions (low pass for woofer and high pass for mid).

Ralf

(*) If the passive design is done properly, i.e. not using merely textbook formulas.

 

[Pano]

That's a good point, and it's certainly worth a bit of investigation of the driver impedance to figure out what the passive crossover is really doing. That does not mean you have to duplicate it, but it's wise to at least know what someone else found that works well.

 

[Inductor]

Good point giralfino/Pano. The "low pass on the mid driver" was devised with the "high pass on the mid" component and cannot be separated without affecting the response. You need new crossovers. (Or to validate/test and measure or simulate the new passive "low pass on the mid driver")