SR6500 Tweeter protection

[jimmyjam_]

I just installed a set of SR6500 components and my MBQuart QAA4250 (250Wx4) amp. tons of headroom for these speakers. woofers are installed in the doors and tweeters are in the kickpanels nearby.

after determining the max gain for my HU without clipping, I turned the gain down and turned it back up until the bulbs just barely glow at max HU volume, but this doesn't seem very loud at all.

Does anyone know the specs on the bulb in the crossover? what wattage is it limiting me to?

seeing that the power handling of the speakers is the limiting factor instead of my amp clipping signal (I'm not used to having this problem :) ), what is a good method for setting my amplifiers gain such that I'll protect these wonderful speakers? Do I really want to avoid having the bulb glow or can I just let it do its job when I'm pushing my system?

maybe I should consider putting the tweeters in the A pillars?

[MacLeod]

Well, 250 watts is more than twice what those speakers are rated to handle so thats the problem. Even with the gains set low, that amp is sending out more wattage than the SR's are rated to handle.

[jimmyjam_]

hmm can you explain that, because that doesnt make much sense. The MBQ amps have a digital readout, and with the gain set to +8db, output is at a level where the tweeter protection is not lighting up, even at full volume, but its not very loud. obviously at this gain setting it is not overpowering the speakers. It has the capacity to overpower them but, short of a catastrophic failure in the head unit's preamp, that shouldn't happen.

The reason I posted here is because somewhere I had read that you shouldn't be driving a set of speakers to the point where the tweeter protection is lighting up because you are abusing them. but are you really? isn't the purpose of the tweeter protection lamp to have variable resistance that increases with the current going through it? essentially a current limiter.

I guess what I mean is, does driving your speakers to the point where the tweeter protection lamp glow intermittently cause any damage to the speaker? I don't see why it would, but I was wondering if someone had reasoning to the contrary.

Thanks for your help :)

[MacLeod]

The only thing that willl destory a speaker is too much power. Either by pushing the speaker beyond the limits of its suspension or by building up more heat in the voice coil than it can disipate.

So sending 250 watts to a speaker that is made to handle 120 is sending too much power to it and thus the bulb lights up to let you know youre reaching the thermal limits of the tweeter.

However, I dont understand why you cant get it loud enough. Im running 70 watts to my tweeters and the bulb never comes on and mine is loud enough for me.

Are you wanting normal to stout listening levels as in 95-105 db or are you looking to drive down the road blasting?

[Toxis]

The only thing that willl destory a speaker is too much power. Either by pushing the speaker beyond the limits of its suspension or by building up more heat in the voice coil than it can disipate.

ACTUALLY, it's distortion that will blow a speaker far faster than over powering. Personally, doubling a speaker's RMS is not overpowering. I think you almost have to get to 4 times the power to be overpowering if the speaker is designed well enough (which the SR's are). I've seen components take 3 times their power and not even flinch but the amp was clean as hell. The main limitation is the x-over, not the tweeter.

[Thom]

A reply from one of our engineers:

He should not limit the input voltage to when the lightbulb first lights up. He should set the limit at a level where the lightbulb is fully on and then back it down slightly. The light bulb will do its job in protecting the tweeter.

We've done more than a few installs with SRs so far and most of the time the light bulbs don't flash much. But we've heard from a few people that theirs do, and those guys didn't blow any tweeters yet.

[exalted512]

ACTUALLY, it's distortion that will blow a speaker far faster than over powering.

what do you think distortion does? Why do you think speakers blow with distortion. I can run my components straight distortion from a 45w amp into my speakers and theyll never blow.

Distortion is essentially a square wave, this square wave can essentially put out 200 watts from a 20w amp.
-Cody

[jimmyjam_]

A reply from one of our engineers:

He should not limit the input voltage to when the lightbulb first lights up. He should set the limit at a level where the lightbulb is fully on and then back it down slightly. The light bulb will do its job in protecting the tweeter.

We've done more than a few installs with SRs so far and most of the time the light bulbs don't flash much. But we've heard from a few people that theirs do, and those guys didn't blow any tweeters yet.

Thank you, this is exactly what I was thinking. i think some of my problem is the placement, I think I'm going to relocate them to the A pillars

[PolkThug]

what do you think distortion does? Why do you think speakers blow with distortion. I can run my components straight distortion from a 45w amp into my speakers and theyll never blow.

Distortion is essentially a square wave, this square wave can essentially put out 200 watts from a 20w amp.
-Cody

Won't a square wave make a speaker flex violently back and forth? It will alternate from its maximum excursion to its maximum incursion?

[neomagus00]

it will try, yes... and naturally it depends on how strong the input is, a speaker can do a pretty damn good imitation of a square wave if the voltage and frequency is low... raise either and distortion (relative to the square wave) goes through the roof...

[jimmyjam_]

yeah this is OT but keep in mind that square waveforms kill speakers not only because of cones deforming. this is only if the amplitude of the waveform is high enough. it is usually because the cone has mass, therefore there is momentum when it is set in motion. to emulate a square wave on a speaker you'd need infinite acceleration, which of course is not possible. It is similar to having an electric motor locked while applying current. the stationary magnetic field is causing resistance in the wire which causes it to heat and eventually burn. i could be wrong, i'm a software engineer not an electrical engineer but I think this is the case.

again thanks for your help. giving your speakers more amplifier capacity will not kill them as long as you are smart about lowpass crossover and gain settings. i was running a set of dayton 7" woofers before this set that were rated at 60W rms 90W max giving them 100W a piece and they loved it. I hope that these SR speakers are better quality than those.

[Toxis]

distortion is not ONLY a square wave. Distortion is also lack of control over a speaker which can add heat to the VC causing it to breakdown. Distortion comes in many forms and fashions. BTW, you cannot give a speaker 45w of pure distortion and have them not blow if you have the volume at a decent volume. What you're calling distortion in that sense is a signal of noise. Not the same thing.

[MacLeod]

The ONLY thing that will destroy a speaker is too much power either by pushing it beyond its suspension limts or building up too much heat in the voice coil, period.

A speaker can play a completley clipped signal all day long if its within its power handling limits. A speaker doesnt know or care what the shape of the signal is, as long as its within the speakers thermal limits it will play it fine.

You take a speaker that will die at 100 watts and feed it a 50 watt, fully clipped signal and itll play it all day long with no effect. Now you take that same speaker and play a 200 watt, crystal clean signal thru it and itll fry.

[PolkThug]

You take a speaker that will die at 100 watts and feed it a 50 watt, fully clipped signal and itll play it all day long with no effect.

Have you tried this? I would think it would heat up.

Try it with one of your tweeters and video tape it. ;)

[neomagus00]

of course it would heat up... his point is that, the speaker doesn't know what 'distortion' is... if you have a square wave with an RMS power of 50 watts (a sinewave of a similar amplitude would have an RMS of far less than 50, but that's irrelevant), and a speaker with a powerhandling of 100 watts, the speaker will take it without complaint... if you have a perfect sinewave of 200 watts RMS, into the same speaker, you will kill it sooner rather than later

this does NOT take into account any cooling of the VC by the continuous movement of the cone, nor does it account for exactly how manufacturers come up with their power ratings - some do it with a sine wave, some with a specific test signal, etc.

[MacLeod]

Sure it would heat up, to about 50 watts but since the speaker can handle 100 watts, that means it can disipate the heat generated by 100 watts and since that distorted signal is only 50 watts, the speaker will be fine and dandy.

Take a rope thats rated to hold 100 pounds. Now if you tie a 50 pound weight on the end it aint gonna break and it wont matter what the shape of that weight is.

Now you tie a 200 pound weight onto it and its gonna snap.

[CrBoy]

Mac makes, by far, the best analogies on this forum!
Go Mac, Go Mac!!! :D :D

[Toxis]

I remember when I was 15 and I walked into a very reputable car audio shop. The owner taught me a lesson that I will never forget when it comes to audio. He said "You cannot overpower or underpower a speaker within reason, but it's distortion that will blow a speaker every time." That's when he took a Hart subwoofer (they were good quality then) and hooked it up off a cheap as hell Lanzar amp that pushed barely 100w and the sub could handle 500w RMS/1000w peak. The sub blew in only a couple minutes. Then he took me out to his truck where he had a JL 10w1 rated at 100w rms and had it run off a PPI 400w amp (when bridged). He had the sub cranked beyond belief. I to this day have not heard a single entry level JL sub hit so hard. He had the same sub going for over 2 years in his truck without adjusting a thing. I was extremely impressed and still am to this day. But what did he know, subs only blow from power.

[PolkThug]

Take a rope thats rated to hold 100 pounds. Now if you tie a 50 pound weight on the end it aint gonna break and it wont matter what the shape of that weight is.

For a fair comparison, you have to swing the weight back and forth violently, eventually the rope will wear out.

[exalted512]

I remember when I was 15 and I walked into a very reputable car audio shop. The owner taught me a lesson that I will never forget when it comes to audio. He said "You cannot overpower or underpower a speaker within reason, but it's distortion that will blow a speaker every time." That's when he took a Hart subwoofer (they were good quality then) and hooked it up off a cheap as hell Lanzar amp that pushed barely 100w and the sub could handle 500w RMS/1000w peak. The sub blew in only a couple minutes. Then he took me out to his truck where he had a JL 10w1 rated at 100w rms and had it run off a PPI 400w amp (when bridged). He had the sub cranked beyond belief. I to this day have not heard a single entry level JL sub hit so hard. He had the same sub going for over 2 years in his truck without adjusting a thing. I was extremely impressed and still am to this day. But what did he know, subs only blow from power.

thats because distortion IS overpowering a speaker.

And speakers should not be graded on quality because they can handle 100w more than theyre rated at. If so then Polk blows my ass because I blew a number of their subs at 100w over their 500wrms. But in actuality, theyre very good subs. Granted I think they shouldve been rated at 400w, nonetheless, it doesnt mean Polk is a crappy brand.
-Cody

[MacLeod]

Now when you push a speaker to its limits it will usually distort and then assume room temperature but a distorted signal will NEVER harm a speaker as long as its within the speakers thermal handling limits. I tell ya what, go take a subwoofer and hook it up to a factory head unit. Now stick in some bass heavy rap music and crank the volume all the way up. Thatll be nothing but a distorted, clipped signal of about 35 watts. The sub will play that horrible sounding signal from now til the cows come home and never so much as whimper.

For a fair comparison, you have to swing the weight back and forth violently, eventually the rope will wear out.

No, 50 pounds is 50 pounds. Now when you start moving something, its velocity will add to its mass and make it weigh more but as long as the total weight doesnt exceed the ropes 100 pound capacity, itll never break.

[PolkThug]

No, 50 pounds is 50 pounds. Now when you start moving something, its velocity will add to its mass and make it weigh more but as long as the total weight doesnt exceed the ropes 100 pound capacity, itll never break.

Exactly! Even though its only 50lbs, when its swinging back and forth violently it has the force of 100+lbs, and wears out the rope, just like a lower watt clipped signal, can wear out a higher watt speaker.

;)

[MacLeod]

Well, first off, that 50 pound weight would have to be moving pretty fast to get over 100 pounds.

Second, Im glad you agree with me. Its not the shape of the weight or the movement, its only when its weight exceeds the ropes capacity!

So its not the distortion or the shape of the signal, but only when it reaches beyond the speakers thermal handling limits! ;)

[MacLeod]

Also, people associate distortion with dead speakers for 2 reasons.

1- Usually when a speaker is being pushed beyond its limits, it distorts and then dies. People think it was the distortion the killed it when in fact it was only a noise the speaker made right before it died because it was being pushed beyond what it could handle

2- When you clip and amplifier it makes it extremely distorted but it also signifigantly increases the power. Take a 75 watt amp and our 100 watt speaker. You push the amp into clipping, which distorts pretty bad but also sends out a signal of about 150 watts thus marking the end of our 100 watt speaker (this is also the reason for the belief that underpowering a speaker will hurt it).

In both these instances, distortion was present right before the speaker assumes room temperature but it was not the cause. Kind of like if I shoot you with a gun. There will be a big BANG right before you die. Now, was it the noise or the bullet that killed you? ;)

[PolkThug]

I'm glad I've got MMC's with Kapton voice coils, bring on the heat!!!

[cam5860]

passive crossovers will melt down long before you over power your speakers so why does it matter?

[1996blackmax]

According to Arc Audio:

"Small Amp Myth
Under powering a woofer is fine. This woofer will suffer no
damage from a 100 watt amp if it is correctly tuned. However,
even a small amp that is being over driven (clipped) can destroy
a sub. Use your power wisely. Clipping can be heard as a dull
thud or a popping sound. If you hear any change in the tone of
your subwoofer this is a danger sign. TURN IT DOWN. If you
want more volume get a bigger amp or add another woofer."


A little more:

"Physics
Energy cannot be created or destroyed, only change forms".
What does this mean? Your amp does not make power, it takes
power from your battery and converts it into a different form.
The subwoofer is just another kind of converter. It changes AC
voltage from the amp into changes in air pressure (that's all
sound is) and HEAT. The more energy being converted the
more heat. A speaker can not reproduce DC voltage (produced
when an amp clips) but this energy must go somewhere. It is all
converted into heat. This is why clipping is so dangerous to a
speaker."

http://www.arcaudio.com/arc-05/pdf/arc_series_04.pdf

[1996blackmax]

I would think these guys would know a little something regarding this issue.

[Toxis]

right but neither of those quotes actually applied really. Maybe it's just me but all it did was beat around the bush in terms of what we're discussing.

I can't wait to build my system. I'm going to overpower everything by 2-4 times. I won't have a single problem. I've done it a hundred times. Having worked in the industry for over 7 years, I've overpowered a thousand speakers and haven't had a problem when it's setup right.

[1996blackmax]

I believe they do apply here. Mac had mentioned that overpowering a speaker is the only way to blow a speaker, these quotes say that something else can also hurt a speaker. They even give an example of a 100 watt amp on a speaker (woofer) that can handle a lot more power.

I have also had more power going to speakers without an issue. Nothing wrong with having extra headroom. My sub is getting about 100 watts RMS over its rated power input.