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Wiring bullet tweeters
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Earplug View Drop Down
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Points: 7216 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2019 at 6:11pm
" So if i understand it correctly it's best to put an extra passive crossover in the tweeterbox"

No, no, no. That will just negate any advantage you gain when using an active filter.

Passives really need to be designed to match the drivers, but given how difficult that can be, we just stick in off the shelf boards and hope for the best! Very often, the punters (and users) don´t know the difference, so WTH, but really a total waste of time and money in your case. At most, an appropriate capacitor - and 12v light bulb if you´re really paranoid. Don´t overthink this - it´s not worth it!

And the same goes for the horn driver.  Smile
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Points: 6086 		Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2019 at 6:14pm
a single capacitor of the right value will protect you from most issues - at 8Ω around 1.5µF wired in series on the + side should do the job just fine - a high voltage polyester capacitor is best
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Originally posted by Earplug Earplug wrote:

" So if i understand it correctly it's best to put an extra passive crossover in the tweeterbox"

No, no, no. That will just negate any advantage you gain when using an active filter.

Passives really need to be designed to match the drivers, but given how difficult that can be, we just stick in off the shelf boards and hope for the best! Very often, the punters (and users) don´t know the difference, so WTH, but really a total waste of time and money in your case. At most, an appropriate capacitor - and 12v light bulb if you´re really paranoid. Don´t overthink this - it´s not worth it!

And the same goes for the horn driver.  Smile





Makes scence :) think i can get started !
Also forgot to say that we will probably use a limiter to make shure no crazy signals can get trough so fingers crossed ;)

Bless !
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Allright, will note that !
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Originally posted by csg csg wrote:

a single capacitor of the right value will protect you from most issues - at 8Ω around 1.5µF wired in series on the + side should do the job just fine - a high voltage polyester capacitor is best


1.5µF will give a roll-off at 13kHz! A bit high, really. It obviously depends on the actual xover frequency being used. Rule of thumb is to set the roll-off at least one octave below the xover frequency.

So say, xover is 5000Hz, a  6µ8 cap would do it.
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Dub Specialist Sound View Drop Down
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3.3uf or 2.2uf poly gives freq around 5k to around 9k imho...
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Guys, I see many times in many threads mention on a series capacitor for low freq diagram protection, and light bulb as "limiter"
for the capacitor I can find some resources on how to chose the right one regarding xover frequencies, but I struggle to find how to determine the specs of the lightbulb to chose in regard to driver arrangement in the box, equivalent impedance, and power, and how it affects the impedence off the box and how the power is "distributed" between the elements.
From my research the answer to a specific question is "do this for your needs and you'll be fine" but I'd like to be able to understand what's going on an chose by myself the right components.
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Originally posted by Dub Specialist Sound Dub Specialist Sound wrote:

3.3uf or 2.2uf poly gives freq around 5k to around 9k imho...

Yes, this is all dependent on driver impedance - which will vary with frequency, so your nominal 8 ohms used in the calculation could actually be 10, or 12, or more. And the roll-off is just first-order, so not as sharp a cut-off as what you get with an active 24dB/octave filter, etc.

The thing is, this if for protection, not setting the crossover point, so you want a cap that does not interfere, ie set the roll-off (a lot) lower than the actual crossover point you´re using. I´ve seen up to 20uF caps used for this in some old commercial cabs.   Smile

And regarding lamps, I usually use these:
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Originally posted by JBK JBK wrote:

Guys, I see many times in many threads mention on a series capacitor for low freq diagram protection, and light bulb as "limiter"
for the capacitor I can find some resources on how to chose the right one regarding xover frequencies, but I struggle to find how to determine the specs of the lightbulb to chose in regard to driver arrangement in the box, equivalent impedance, and power, and how it affects the impedence off the box and how the power is "distributed" between the elements.
From my research the answer to a specific question is "do this for your needs and you'll be fine" but I'd like to be able to understand what's going on an chose by myself the right components.


You could start by simulating the circuit in SPICE. Then actually test the thing with a signal generator and scope, etc. That´s when the fun begins.   Smile
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studio45 View Drop Down
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Firstly, the lightbulb trick is just a fuse with visual indication and a very slow-blow characteristic. You can use a ordinary fuse instead, but you won't get any warning it's about to blow, and it may blow on otherwise non-dangerous transient peaks. Requiring you to climb up the stack during the dance to replace it LOL
The only rule of thumb about lightbulbs that I've been able to work out, is you should use a 12 volt automotive lightbulb with a wattage rating just about half that of than the drivers you're trying to protect - ie if you have a box of four 25 watt bullets, wired series parallel for a 50 watt rating, use a 25 watt bulb. It will definitely blow if you try to put enough current to get 50 watts thru it for more than a second or so, this gives the protection you need. 
There isn't an infinite range of automotive bulbs available, and actually it's hard to find one rated more than 25 watts without going to super-expensive halogen headlamp bulbs, or xenon arc types which are obviously unsuitable for the job. But, it's OK to use more bulbs in parallel to get the rating up to where you need it, if you have to protect a large tweeter array.
The other thing to think about is sensitivity. If your bullets give 102dB for a watt (108 for 2 watts, 114 for 4 watts, etc) how much power do you actually need before your audience's eyeballs melt? The answer is normally only 1 or 2 watts, and 25 watts through any competent tweeter array ought to be VERY loud indeed. So your protective bulb having a lower rating than the theoretical max, is not usually a problem. 
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" Firstly, the lightbulb trick is just a fuse with visual indication and a very slow-blow characteristic. You can use a ordinary fuse instead, but you won't get any warning it's about to blow, and it may blow on otherwise non-dangerous transient peaks. Requiring you to climb up the stack during the dance to replace it"

Yes - and no!  Smile

The lamp also acts as a compressor, ie more signal = light = higher resistance= more voltage drop across the lamp = less signal getting to the drivers.


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Originally posted by studio45 studio45 wrote:

There isn't an infinite range of automotive bulbs available, and actually it's hard to find one rated more than 25 watts without going to super-expensive halogen headlamp bulbs, or xenon arc types which are obviously unsuitable for the job. 
Blue Aran sell Fuse Bulbs
Look fairly economical to me.
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