compression drivers and capacitor |
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sicoroots
Registered User Joined: 11 December 2016 Location: pacific NW Status: Offline Points: 78 |
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Posted: 26 September 2018 at 12:43am |
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Hello everyone I have some questions about
compression drivers and I was hoping someone can give me some advice here… I’ve built a B&C mid top
speaker with 12” and 1” compression driver : http://www.bcspeakers.com/media/W1siZiIsIjIwMTMvMDIvMTIvMTYvMTMvNDgvNzg4L2ZpbGUiXV0.pdf I’m using it as mid top,
active crossed over on a DCX2496 like the rest on the sound system parts.. I
didn’t really follow the electrical diagram on the last page since I was not
planning to have an internal passive crossover. What I’m noticing though,
after doing a bit further reading on the subject, is that in order to protect
compression driver from DC current pulses a capacitor is used in the diagram. This is also mentioned in other
web sources I’ve been reading…basically it’s not recommended to have the CD
connected directly to the amp without a capacitor in between. Now, I’ve been using this set
up for almost a year and haven’t really blown anything although I’m starting to
think if I’m doing something completely wrong anyway. I haven’t wired in a
capacitor before so I will have to look into this but I’d like to know what
your thoughts are on this…. Another question is about the
fact that I’m noticing that the 2 x 1’” CD currently working as tops are
struggling a bit to keep up with the rest of the speakers : 4 x 12” on bass / 2
x 12” kicks / 2 x 12” mids. It seems that they are overpowered by all the 12”
drivers. I was considering of adding maybe
2 more CD horns per side ( 2 on top of each mid-top cab ) to help on that range.
Good / bad idea ?? any
suggestion that I could consider please ? Thanks a lot ! |
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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If you have a good horn and drivers, the HF should easily keep up with a lot of bass. Adding more horns may make it quieter at many positions due to comb filtering and cancellations.
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sicoroots
Registered User Joined: 11 December 2016 Location: pacific NW Status: Offline Points: 78 |
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thank you I haven't thought about the comb filtering effect ....so if I wanted to reinforce the tops range , I have them crossed over with the 12" mid at 1.7khz at the moment, it should be more efficient to have a bigger than 1" comp driver in the two mid tops cabs....? |
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2537 |
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This is also mentioned in other
web sources I’ve been reading…basically it’s not recommended to have the CD
connected directly to the amp without a capacitor in between.
I haven’t wired in a
capacitor before so I will have to look into this but I’d like to know what
your thoughts are on this….
Edited by Conanski - 26 September 2018 at 6:24am |
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sicoroots
Registered User Joined: 11 December 2016 Location: pacific NW Status: Offline Points: 78 |
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sicoroots
Registered User Joined: 11 December 2016 Location: pacific NW Status: Offline Points: 78 |
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….[/QUOTE] If you do add a cap select one that begins to act an octave below the active (DCX)crossover frequency. I'm xover the comp driver at 1.7 khz at the moment, what would be an adequate frequency to look at for the capacitor ? based on the calculation I made for the 8ohm CD with 1.7 Khz the capacitor at one octave below is around 850 Hz...does it sound right ? |
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sicoroots
Registered User Joined: 11 December 2016 Location: pacific NW Status: Offline Points: 78 |
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I'm using an online calculator in order to get the capacitance in microFarad to select the right capacitor...should I consider the 8ohm of a single driver or 4ohm since I'm using the CD wired in parallel ?
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Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7216 |
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850 Hz is fine. And total impedence will be (nominal) 4 ohm, so 4 ohm for the calculation should do it. |
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Earplugs Are For Wimps!
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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God forbid that sound is actually physics, you know, a science. |
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2537 |
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Can you detail exactly what settings you have in the DCX for the whole system? |
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2537 |
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These capacitors should go inside each of the boxes wired in series with the compression drivers, and that means the impedance used to calculate the crossover filter will be 8 ohms. For that you want a 250v non polarized cap of a value as close to 23.38mf as you can find, and you can use several caps together to get that if necessary so for example two 10mf and a 2.2mf for a total of 22.2mf.
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toastyghost
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If it’s a CD horn it should have boost. |
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