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Capacitor to protect Tweeter in active speaker, cheap or quality?
Capacitor to protect Tweeter in active speaker, cheap or quality?
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Old 14th March 2018, 04:01 AM   #1
mikes875 is offline mikes875  Australia
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Default Capacitor to protect Tweeter in active speaker, cheap or quality?

I am building 4 way active speakers and am going to add approx 30 uF capacitor to protect the tweeter from low freq and DC current. Is quality important in this situation? I am using a high quality Scanspeak tweeter, so don't want to limit it, but on the other hand no point buying a quality cap if it wont make any difference in this scenario. It will be cutting off way below the active crossover point.
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Old 14th March 2018, 04:36 AM   #2
asuslover is online now asuslover  Romania
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Capacitor to protect Tweeter in active speaker, cheap or quality?
I have the same dilemma . I think I'LL use the 1st order passive crossover value for the tweeter. But quality cap for sure.
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Old 14th March 2018, 04:50 AM   #3
mikes875 is offline mikes875  Australia
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You could do that, from what I have managed to find online it seems that the general consensus is to go 2 octaves below the crossover point so it has no direct impact. I was thinking of just using a cheap Dayton Audio DMPC-33 33uF 250V Polypropylene Capacitor.

Tweeter is 8 ohm (ScanSpeak D2908/7140 Beryllium Dome) so that should cut off at 600 Hz (+2 octaves being 2400 Hz)
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Old 14th March 2018, 04:51 AM   #4
stratus46 is offline stratus46  United States
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Quote:
Originally Posted by mikes875 View Post
I am building 4 way active speakers and am going to add approx 30 uF capacitor to protect the tweeter from low freq and DC current. Is quality important in this situation? I am using a high quality Scanspeak tweeter, so don't want to limit it, but on the other hand no point buying a quality cap if it wont make any difference in this scenario. It will be cutting off way below the active crossover point.
Every crossover I've seen has at least a series cap for the tweeter already to prevent low frequencies and DC (the ultimate low frequency). Why do you need another?

G
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Old 14th March 2018, 04:54 AM   #5
asuslover is online now asuslover  Romania
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Capacitor to protect Tweeter in active speaker, cheap or quality?
Wow, that's a tweeter ! Spend a few more bucks for a matching cap!
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Old 14th March 2018, 05:02 AM   #6
benb is offline benb  United States
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Why not use a lower value capacitor and use it (I think as asusliver was saying) as part of the crossover? This would "require" a high quality cap, but at a lower capacitance the cost increase wouldn't be as much, and a lower value will better protect the tweeter.
Quote:
Originally Posted by stratus46 View Post
Every crossover I've seen has at least a series cap for the tweeter already to prevent low frequencies and DC (the ultimate low frequency). Why do you need another?

G
The OP said "active" meaning the crossover is done at line-level, before the amplifier (and there's an amplifier for each driver). The amp's output would connect directly to the tweeter without the cap.
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Old 14th March 2018, 05:08 AM   #7
suzyj is offline suzyj  Australia
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I found that unless I used a really really enormous cap the phase shift really stuffed the time alignment around. Rather than a capacitor larger than the tweeter, I build a DC protection circuit instead, which ensures the tweeter can't be blown apart.
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Old 14th March 2018, 05:26 AM   #8
mikes875 is offline mikes875  Australia
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Quote:
Originally Posted by stratus46 View Post
Every crossover I've seen has at least a series cap for the tweeter already to prevent low frequencies and DC (the ultimate low frequency). Why do you need another?

G
I am going for an active crossover, so this will be the only component between the amp and the driver (no passive crossover)
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Old 14th March 2018, 05:37 AM   #9
asuslover is online now asuslover  Romania
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Capacitor to protect Tweeter in active speaker, cheap or quality?
Quote:
Originally Posted by suzyj View Post
I found that unless I used a really really enormous cap the phase shift really stuffed the time alignment around. Rather than a capacitor larger than the tweeter, I build a DC protection circuit instead, which ensures the tweeter can't be blown apart.
Yes, but what if....I have way cheaper tweeters than him and I am still going to use a capacitor.
He wants his 8 ohms tweeter to be crossed at 2400hz, I would(but I might be wrong)use an 10uf(or more) /100v(or more) capacitor , according to this :

ERSE - Crossover Calculator - First Order 2 Way

The size for such cap will not be that big.
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Old 14th March 2018, 05:37 AM   #10
mikes875 is offline mikes875  Australia
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Quote:
Originally Posted by suzyj View Post
I found that unless I used a really really enormous cap the phase shift really stuffed the time alignment around. Rather than a capacitor larger than the tweeter, I build a DC protection circuit instead, which ensures the tweeter can't be blown apart.
I am going to use a DSP for the crossover so from what I can understand will be able to adjust the phase to compensate without too many issues. Wouldn't know how to build a DC protection circuit I am afraid
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