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3 way Passive crossover
3 way Passive crossover
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Old 5th March 2020, 10:59 PM   #1
djlivex is offline djlivex  United States
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Default 3 way Passive crossover

So I finished a 3 way cab from a plans site, and I have all the drivers wires feet but not the crossover. It is supplied by another PA supplier but a lot more expensive per board. Now there is a 3 way passive crossover by Eminence (500Hz/3.5kHz) at $68 each 12 dB.slope. So my question is this, this will be used as a 3 way top and I just built ported 2x15 JBL loaded subs under will matter which crossover I use Eminence has the same xover points also will be used for DJ playback role with amps and BBE and EQ.
So will it matter? Custom built by a supplier is designed for 500 watts, while the Eminence 400 watts. I don't need all that power for my customers don't want concert volume backyard parties and small to medium halls capable for <250 peeps.
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Old 6th March 2020, 11:16 AM   #2
Damo s is offline Damo s  United Kingdom
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I guess ideally you probably want the xover to have a rating matching the bass driver. If your amp has a limiter then use it.

Assuming you are high passing your tops at around 100hz or so, for delivering everything over 100 hz then 400rms should be plenty loud enough anyway.
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Old 7th March 2020, 11:21 PM   #3
MAAC0 is offline MAAC0  Portugal
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Beyma FD250 is rated at 600W and has attenuation jumpers for the horns.
It is being used also with a P7000 700W Yamaha amp for long time and no issues till today.
The coils are 1.5 sqmm and caps rated at 200V. So it can handle more than 600W for sure. I have several working fine with several drivers and horns.
Believe me, for 250 people and DJing You really need more than 400W RMS when the party is at the "Heat moment" and in winter You need more because of people's cloth attenuation, and we are talking about 98-100 dB efficiency 15'' low mid drivers, not the chinese 89dB crap.
I would use the crossover only on the tops ans drive the subs with another sub amp.
If You go with an electronic crossover & tri-amping protect at least the horn from DC spikes with a large 20uF motor starting cap. Yes, motor start capacitors sound fine !!.
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Old 8th March 2020, 12:30 AM   #4
djlivex is offline djlivex  United States
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I was going to set the 215 JBLs at 80Hz crossover point in a 3 way electronic crossover and separate amp 750w@4ohm load. Then the 3 way passive tops actually 12"/6.5"/1" will have a passive eminence 500/3.5kHz points. What I like about the Eminence crossover has a high frequency bulb that can help protect it from to much power.
Also since the passives 500 and below, then it will have an overlap at 80Hz.
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Old 8th March 2020, 02:38 PM   #5
Damo s is offline Damo s  United Kingdom
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Quote:
Originally Posted by MAAC0 View Post
Believe me, for 250 people and DJing You really need more than 400W RMS when the party is at the "Heat moment" and in winter You need more because of people's cloth attenuation, and we are talking about 98-100 dB efficiency 15'' low mid drivers, not the chinese 89dB crap.
not sure I agree. 400rms over 100hz probably is enough with efficient drivers provided there is plenty of sub and the tops are located properly. People dont want their ears blasted with midrange. The illusion of a good level is created by having decent sub power.
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Old 8th March 2020, 02:42 PM   #6
chris661 is online now chris661  United Kingdom
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A proper 3-way passive crossover is a complex thing, and should be designed with particular drivers in mind.

A generic crossover will work in that each driver is producing roughly the correct range of frequencies. Ish.

However, there's a lot of stuff that's driver-specific that a generic crossover simply can't account for:
- Impedance curves of connected drivers. If you're using a LF driver with lots of inductance (or even just some inductance, depending on how generic the crossover is), the lowpass slope will be out. Result: extra midrange mush from the bass driver. There's also the fact that any impedance peaks (HF drivers tend to have a few around/below the bottom of the passband) will result in extra power being delivered to those drivers, regardless of what the crossover itself is doing. Result: HF/MF drivers receiving near-full-power out-of-band signals. Excess distortion if you're lucky, and driver death from over-excursion if you're not.

- Driver sensitivities. The crossover might have a 6dB pad for the HF driver. That may or may not be correct. Chances are it won't be.

- Driver frequency response near the crossover points. If your bass driver has a bump just above the crossover point, then the acoustic crossover point will move up to the other side of the bump. Just an example. There's a lot that can go wrong there.

- Driver phase shifts at/near the crossover points, including time alignment etc. There's just no way a generic crossover can always correctly sum three random drivers.


I don't like raining on people's parades, but I do think some realism is required here.

If you're investing any money into this project, then £100-ish to get a half-decent measurement setup together should be the first purchase.

Chris
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Old 9th March 2020, 03:13 AM   #7
djlivex is offline djlivex  United States
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Chris661 you're right I was waiting for this explanation it is clear to me now, will get the crossover for the project no use saving $30 each against a $150 woofer fix,or a $35 HF driver, thanks
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