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Old 30th May 2013, 02:55 PM   #1
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Default Basic Crossover help.

Ive got some 4 ohm full range speakers that I want to add a mid/bass driver to.

Found a calculator online:

Click the image to open in full size.

If I just buy the 4 components, Do I just solder as the picture shows and run the two circuits in parallel to the amplifier?? Will it keep the correct impedance?

Are they a special kind of caps?? And open air coils??


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Old 30th May 2013, 03:22 PM   #2
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I've moved this over to the speakers section.

1. Yes solder as shown. The word parallel doesn't really apply when the signal is being split into HF and LF, the impedance will remain at nominal 4Ω.
2. Poly caps will be good enough.
3. Air colis are often preferred.

Do you happen to have the impedance plots for the drivers so you know what actual values of caps and coils you need?
Are you using a zobel network?
How about BSC?
L-padding?
Notch filters?
Are the mid basses being added to an existing cabinet?

If any of these questions have you scratching your head, you may be in deeper than you want to be. Tell us in detail what you are doing and maybe we can get you headed down the right path.
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Old 30th May 2013, 04:50 PM   #3
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I know I'm over my head. Its a fun place to learn things :P

I'm trying to bridge the gape between the full range speakers and the subwoofers.

I'm running two full range speakers off of a 100wrms amp that isnt really doing much in the way of sound.

PUNCH Speakers - PPS4-8 - Rockford Fosgate®

Was thinking about adding these midbass drivers. You can buy the crossovers for them but they're at 1.5khz or around there. I want something @ about 500hz

All the drivers are 4ohm
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Old 31st May 2013, 01:03 PM   #4
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If I change the crossover frq to 425hz its says I need a 47uf cap and a 3mh Inductor.

Can I used this? (Looks okay to me. 100wrms at 4 ohms is 20 volts.)
JAPAN 3pcs Nichicon MUSE FG?Fine Gold) 47uf 63v Audio Capacitor for audio cap | eBay

And these cheap inductors? (I'm guessing no, because the good ones are expensive and
look more impressive)
Inductor 3MH 3 mH 3000uH 3 pcs | eBay
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Old 31st May 2013, 01:22 PM   #5
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Speaker crossover caps need to be non-polar, Nichicon FG's a polarised caps so are not suitable. You need to use either film caps, or non-polar (bipolar) electrolytic caps.

Film caps are prefferable but are bigger and more expensive. Bipolar electrolytics are good for experimenting Nichicon DB/DG are bipolar specifically for crossover networks...

The inductors look, well a bit flimsy Not sure they would take speaker level signals. for "low cost" inductors cored inductors like this 3.0mH 18 AWG I Core Inductor 266-558 would be an option. Slightly more expensive would be Jantzen pcores. Air cores are the best but for low DCR they are expensive.

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Old 31st May 2013, 01:50 PM   #6
ODougbo is offline ODougbo  United States
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Crossing over that low is tough, better off active.

Although, here's an idea, buy off the shelf 3-way and modify it (which would be easy).

6Db 375Hz / 3Khz Crossover 3-Way | CRX-3003K (CRX3003K) | Distributed By MCM

http://www.mcmelectronics.com/product/60-10575

Last edited by ODougbo; 31st May 2013 at 01:57 PM.
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Old 1st June 2013, 10:55 AM   #7
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thanks guys. If thats too low, what would be a more realistic crossover point?

Ive seen three way component speakers that are at 500hz but they're expensive.
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Old 1st June 2013, 05:25 PM   #8
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You know when you look inside a cheap two way speaker and there is just a cap on the tweeter wire. Does this mean that its not a crossover but two speakers in parallel with a cap to limit the bass from the tweeter?
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Old 1st June 2013, 05:52 PM   #9
ODougbo is offline ODougbo  United States
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80 -100hz

Are you sure you want to go down this road, I tried something very similar not that long ago (before found this site (and saw the light ))

It didn't work at all; the 8"RF sound great in cars/trucks, I had no luck inside, just a noisy thumping mess.

However, if you want to give it a whirl, you'll need a xo, can use car xo and 12v power pack; tons of them out there. You'll need another power amp.

Quote:
Originally Posted by Sounduser View Post
thanks guys. If thats too low, what would be a more realistic crossover point?

Ive seen three way component speakers that are at 500hz but they're expensive.
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Last edited by wintermute; 2nd June 2013 at 12:45 AM. Reason: replaced cop smily
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Old 2nd June 2013, 10:18 AM   #10
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Sounduser View Post
thanks guys. If thats too low, what would be a more realistic crossover point?
I don't mind crossing any driver passively regardless of the frequency. I'm not saying it's always ideal but there's nothing especially wrong with it either. Besides, there is a lot that goes in to crossing properly and doing this right is more important than the method you choose to do it. Even iron cored inductors and electrolytic capacitors can be a part of a good sounding system.

Quote:
Originally Posted by Sounduser View Post
You know when you look inside a cheap two way speaker and there is just a cap on the tweeter wire. Does this mean that its not a crossover but two speakers in parallel with a cap to limit the bass from the tweeter?
I'd still call it a crossover. Drivers have mechanical and electrical behaviours similar to crossover filters so the crossover filters themselves don't define things, they adjust and augment them.

But I'd agree with you. I'd call them a cheap crossover.
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