Germanium crossover...

[headless 10+ year member]

You kind of answered that your self. They are there to protect the tweeter from excess wattage so they do not blow. How much power are you feeding them? You wont need much power when going active we usually run a max of around 120 watts, which on an active setup is pretty loud. 75 watts will do must justice.

Not really; i still don't know the answers to the questions i posted. Every time i ask direct questions i get vague responses like yours. I know WHY the bulbs are there; to protect your tweeters from overcurrent of course.. - i want to know how they function and what causes them to glow. Is it overpower, or simply power? Do the bulbs act as glorified fuses, or are they only supposed to light when you're pushing too much power to the set? If they only light up when you're overpowering the set, it appears that they consider 110w per side as too much power...and 4x50w biamped too! I don't think that's the case, because the specs read 150w per woofer and 150w for the tweeter as their rating. Why have protection that cuts on at less than 100watts input if your components are rated @ 150w each? I'm starting to think that nobody who speaks english really knows how these crossovers and protection circuits work.

I was feeding them 4x50w biamped, and the lights came on then at reasonable volumes, though they were nothing like what i'd consider 'loud'.

Then i swapped the 4x50 to bridged @ 2x110w or so, and the lights came on then. Louder, but not 'loud enough' in most cases for my liking.

I was suspicious of my 4x50/2x110w eclipse amp and thought maybe it was clipping the signal at higher volumes, thus causing excessive power RMS values which would cause the PTC to engage...but

Now i've got a 4150XXK, bridged to 2x320 or so...and the lights still come on at high volumes. I've got the gain at an extremely low setting and my HU is not clipping the signal. I'm fairly sure i'm not clipping the amp as it's not even pulling 200watts on the input side before the lightbulbs start glowing happily.

Do you think that removing the passive x-overs would result in an overall increase in volume? I find that the lightbulbs come on well before i get to a volume that i consider 'loud' and that's considering i've only got a 12w6 (version one!) on only 300watts..SEALED... so I'm not drowing them with bass.

While they get loud, and they stay clear, the lightbulbs make me wonder if going active would result in damage to the speakers.

What do you think? Do the lightbulbs indicate that the tweeters would be damaged right then if they were not present? or do they indicate that power is flowing and nothing more? If i were to go active, it would be with my 4150xxk which can put out about 100watts*4 @ 4ohm.

 

[nismos14 5,000+ posts]

Going active wont harm them because you have more direct control over the xover frequencies you use and can be (hopefully) more aggressive with your slopes. You would be alright with the power you have because you can adjust accordingly. You don't HAVE to run the full power to them and with the XXK running in stereo you'd be more than fine.

Also based on your explanation, I do believe the lights to be indicators of the presence of power going through the xovers. You would have a problem when a bulb does NOT show power. I'm guessing that at very low volumes the lights are still on, just not as bright as when you begin to raise the volume.

 

[headless 10+ year member]

Going active wont harm them because you have more direct control over the xover frequencies you use and can be (hopefully) more aggressive with your slopes. You would be alright with the power you have because you can adjust accordingly. You don't HAVE to run the full power to them and with the XXK running in stereo you'd be more than fine.
Also based on your explanation, I do believe the lights to be indicators of the presence of power going through the xovers. You would have a problem when a bulb does NOT show power. I'm guessing that at very low volumes the lights are still on, just not as bright as when you begin to raise the volume.

I think trying to push 350w into one of these tweeters would be a great way to release the magic smoke //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif I've got gains set extremely low; barely above absolute lowest setting possible (say the nob starts it's travel @ 8 o clock...it's set to 9 o clock)

Re: your theory on the light bulbs, i personally believed that power would always flow through them and they should lighten up progressively as power is increased...but at lower volumes, they don't glow at all. Does the glowing indicate that something's frying...or does the blowing of the bulb indicate that something was about to fry...is the real question. I haven't blown any bulbs; does that mean i'm OK, even if the bulbs are glowing brightly enough to read a book in my trunk? Nobody seems to know the answer to this question on how exactly these are designed to do their job.

 

[PremierAudio 10+ year member]

The light bulbs filament takes away some of the power you are giving, so you do not blow the tweeter. So yes, if you went active with them 320 watts would fry that tweeter. They do not glow at lower volumes because you are not giving them any power there. Im sure you know that your not always giving them 320 watts at all times.

The lights will blow out before anything happens to your tweeter so you are fine.

When I had mine hooked up they use to glow like a flashlight. MB Quarts crossovers have this feature in also. Just remember you are on the edge with power requirements, but that doesnt mean you should turn it down at all //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[headless 10+ year member]

Thanks for the response! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

So could i safely say if i'm pushing that much power now (obviously nowhere near 320watts; yes, i understand how the amplifier functions) that it would be safe to leave the same gain settings when going active? Or would i need to tweak them down because i would now be providing more power to the tweeters than i used to, since i wouldn't be losing any to the lightbulb filament?

Also, i'm still not clear on weather the lightbulb glows because all power for the tweeter passes through it and lightbulbs simply glow beyond a certain watt input, or because power is actually being diverted through the bulb because i am sending the crossover too much. Latter, or former?

 

[PremierAudio 10+ year member]

Tweak them down. You wont need that much power going active at all.

 

[Motovet 10+ year member]

The polarity reverse is the ticket! The comps now just walk on my Boston Pros I run in my truck....soon to be changed to some Rainbow Powers though. I too can light up the bulbs with the 150W per side I'm feeding them, but with most music it's a bit on the loud side at that point. With some tracks though I can use more volume than the bulbs like.....I'll try to be careful.

 

[thch 10+ year member]

Considering at higher volumes (but not high enough for me) i'm seeing the lights glowing merrily on the crossovers, do you think i should be worried about switching to an active setup and losing the PTC tweeter protection?
I've asked about these lights before and nobody really seems to know if they only light up when there is excess current or if they glow relative to the amount of current flowing through the x-over, or if they glow more when you choose to attenuate the tweets more and less when you turn off tweeter attenuation, etc.

What's your knowledge of the light bulbs?

What do they do?

Why do they come on?

If they are coming on, is there a problem?

And if so, what problem does it indicate?

If the lightbulbs are glowing, should i be scared i'm about to fry things?

If i shouldn't be worried, and the reason is because 'they are doing their job and protecting your tweeters', then should i be scared if i switch to active and leave the same gain settings & try to play them at that same volume? Should i expect a blown tweeter?

Thanks for the input!

as the wire gets hot (due to excessive current), it begins to glow (blackbody radition now produces visible light) and it turns out that the resistance of the bulb quickly moves from "low resistance" to "medium resistance". as the resistance increases, the power to the tweeter decreases, along with trebel.

(the shift in the frequencies from blackbody radiation are why you don't see a progressive shift -- the bulbs do glow, but at infra-red that you can't see, or at intensities that are not bright. you have to wait until the bulbs produce a high intensity, higher energy light)

because amps provide output voltage, instead of directly outputing power, the tweeters end up receiving less power. the bulb doesn't absorb more power or anything, but rather the entire circuit (bulb + tweeter) absorbs less power.

(this would tend to cause the bulb to cool down, but if the bulb cooled down, the resistance would decrease, which would allow more power. clearly some equilibrium is reached where the bulb receives enough power to stay hot, but not enough power to starve the tweeter and itself of all power)

as for the power question, thats something for the manufacturer. they might set the bulb up to glow at moderate outputs, within their power specs, or they might use it as a purely protective feature. possibly the tweeters sound poor at high volumes, and the added resistance is beneficial to sound.

given the protective nature of these bulbs, i'd probably stick with the passives, as the actives will probably not perform this automatic gain compensation that the bulbs are providing.

glad to hear about the successful polarity swap. (Linkwitz-Riley filters depend on good phase properties to provide their key benefit of phase-coherance, which is why they are more buzzwords in car audio).

 

[headless 10+ year member]

THCH, thanks for the explanation, you got the right idea on what i was looking for. I had heard that when the protection cuts in on some sets, you can notice the volume decrease on the tweets, but i've never had a noticeable decrease in volume...in fact, even with the bulbs glowing away merrily, turning the volume up still results in volume increasing from both the tweets and the woofers. I expect loss of volume would be the very end of it's range where it's resistance spikes extremely high causing very little current to flow.

 

[theothermike 10+ year member]

****, now i wonder if my decision to go 3 way was a good one when i could have gotten the rainbow germs for the same price instead of the cdt hd-642. o well i bet when i go active they will sounds just as good as the germs if not a tad better

Mike