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Car Forum / Saab Cars / April 2005I think I blew my amp??!!
I just got some new dual 6.5" speakers for the back. when i got them in they really sounded nice but when i turned it up with the bass they stoped working properly. they warrant as loud as the frunt ones. what is the power rating for the amp in my 1990 saab 9000 cd and where is it located. If i get a new cd player like a alpine or something will that fix the problem. > I just got some new dual 6.5" speakers for the back. when i got them in > they really sounded nice but when i turned it up with the bass they > stoped working properly. they warrant as loud as the frunt ones. what > is the power rating for the amp in my 1990 saab 9000 cd and where is it > located. If i get a new cd player like a alpine or something will that > fix the problem. You could have blown the amp, or it may have just failed, but more often when you overdrive an amp it's the speaker that blows from distortion than the amp itself. >I just got some new dual 6.5" speakers for the back. when i got them in >they really sounded nice but when i turned it up with the bass they >stoped working properly. they warrant as loud as the frunt ones. what >is the power rating for the amp in my 1990 saab 9000 cd and where is it >located. If i get a new cd player like a alpine or something will that >fix the problem. Assuming you took the old speakers out and didn't just connect the new speakers across them, then it's unlikely that you damaged the amp. It sounds like the speakers have crapped out to me. Can you try the old ones back in as a test? Cheers, Colin. yes i will do that today and does that mean i need to get i higher watt speacker becuse these are 140 w max i really didnt thing the saab amp can do that much. So what is the watt specs on the amp and where is i located > yes i will do that today and does that mean i need to get i higher watt > speacker becuse these are 140 w max i really didnt thing the saab amp > can do that much. So what is the watt specs on the amp and where is i > located No you more likely need a higher wattage amp. If you drive an underpowered amp too hard it clips, and clipping is very hard on speakers. > No you more likely need a higher wattage amp. If you drive an underpowered > amp too hard it clips, and clipping is very hard on speakers. What is clipping? i looked at it today and i was just a loos wire and all is good but i need to knowe where the amp is so i can bypass it when i get a cd player. i also need to knowe the same thing for a 1992 saab 900 4dr. > > No you more likely need a higher wattage amp. If you drive an > underpowered [quoted text clipped - 5 lines] > need to knowe where the amp is so i can bypass it when i get a cd > player. i also need to knowe the same thing for a 1992 saab 900 4dr. http://www.audiovideo101.com/dictionary/clipping.asp >>yes i will do that today and does that mean i need to get i higher watt >>speacker becuse these are 140 w max i really didnt thing the saab amp [quoted text clipped - 3 lines] > No you more likely need a higher wattage amp. If you drive an underpowered > amp too hard it clips, and clipping is very hard on speakers. Yeak all that limited voltage and current wreaks havoc on the speakers... NOT. Where do you people get this stuff? -Fred W >Yeak all that limited voltage and current wreaks havoc on the >speakers... NOT. > >Where do you people get this stuff? It can happen in theory. i.e. driving an amp hard into clipping can cause it to put out spikes in excess of it's rated output. If the speakers could only just cope with the amp's rated output then they could *theoretically* be damaged. Virtually never happens in practice of course... Cheers, Colin. >>Yeak all that limited voltage and current wreaks havoc on the >>speakers... NOT. [quoted text clipped - 11 lines] > > Colin. If that was true, the only thing I could see is possibly blowing out a tweeter, since the woofer would have plenty of power handling capability and the spikes would be very high frequency and so the crossover network would shunt it away from the woofer and midrange and send only to the tweeter. But I don't see why driving a linear amplifier into its limits (that's what clipping is) would cause spikes... -Fred W >> Virtually never happens in practice of course... >> [quoted text clipped - 12 lines] > > -Fred W I think you would be surprised just how unlinear your linear amplifier becomes when cranked up. That being said there are a lot of factors involved, if your speakers are not very efficient or provide a difficult load for your amplifier, which may be poorly designed, it does not take very long for it to start having problems. Hi-end hifi is my second hobby after Saab's Mike >>But I don't see why driving a linear amplifier into its limits (that's >>what clipping is) would cause spikes... [quoted text clipped - 10 lines] > > Mike Actually, it would not surprise me as I am an EE. I only mentioned linear amplifier to distinguish it from a switching amp or Class C amp. -Fred W > >>But I don't see why driving a linear amplifier into its limits (that's > >>what clipping is) would cause spikes... [quoted text clipped - 13 lines] > Actually, it would not surprise me as I am an EE. I only mentioned > linear amplifier to distinguish it from a switching amp or Class C amp. Never done done C but familiar with A, AB, B, D, G and H. IR has some lovely 100V mosfets just out with 10mohm on resistance - perfect for heatsinkless high power class D. In a surface mount package about 8x7mm too ! Graham >If that was true, the only thing I could see is possibly blowing out a >tweeter, since the woofer would have plenty of power handling capability >and the spikes would be very high frequency and so the crossover network >would shunt it away from the woofer and midrange and send only to the >tweeter. Yep. That's about right. >But I don't see why driving a linear amplifier into its limits (that's >what clipping is) would cause spikes... I don't make a study of it or anything, but I could take a couple of guesses... 1. The amp's power rating will be at a certain, reasonable, distortion level - say 5%. That 5% distortion doesn't happen *at* the clipping point but some way before it. So you can drive the amp harder and get more power than it's rating, but it sounds crap so the manufacturer can't make any claims about this higher rating. 2. If you then continue to drive the amp harder still, and into real clipping, the resulting sharp edges on the output waveform mean the amp is generating much more power at high frequencies than it would normally. The tweeters in the speaker system would normally only expect to see a small fraction of the amp's output, so when the amp starts producing serious power in the tweeter's range, safety margins can get eaten into. Cheers, Colin. > 1. The amp's power rating will be at a certain, reasonable, distortion > level - say 5%. That 5% distortion doesn't happen *at* the clipping [quoted text clipped - 9 lines] > starts producing serious power in the tweeter's range, safety margins > can get eaten into. Actually it's more the rating of the *speaker* that's the issue. A 140W speaker will not handle 140W anywhere near continuously, that rating is music power, which assumes that the average RMS power is much lower. When an amplifier clips hard the output is much closer to DC at the *peak* power of the amplifier which is substantially higher than the RMS. If you don't believe me, take a speaker rated at 140W, assuming it's 4 ohm, connect it to a 24V DC source (which will cause it to draw about 140W) and see how long it takes the voice coil to smoke. You probably won't get more than 10-15 seconds out of it. Tweeters usually go first, but I've seen *many* speakers damaged by an underpowered amp clipping, if you open one up the voice coil is blackened. > Actually it's more the rating of the *speaker* that's the issue. A 140W > speaker will not handle 140W anywhere near continuously, that rating is > music power, which assumes that the average RMS power is much lower. When an > amplifier clips hard the output is much closer to DC at the *peak* power of > the amplifier which is substantially higher than the RMS. No it's not. When an amplifier clips hard it produces a multitude of odd harmonic frequencies of the original. It doesn't produce DC. Other failures of amps can cause DC, but not clipping. > If you don't believe me, take a speaker rated at 140W, assuming it's 4 ohm, > connect it to a 24V DC source (which will cause it to draw about 140W) and > see how long it takes the voice coil to smoke. You probably won't get more > than 10-15 seconds out of it. Tweeters usually go first, but I've seen > *many* speakers damaged by an underpowered amp clipping, if you open one up > the voice coil is blackened. You are comparing apples and oranges. The power rating of a speaker is based on its impedance, not its DC resistance. They are very different things. When using a DC coupled amplifier, it is quite common for the amp to fail and produce a DC voltage. As you noted, this is very bad for the speakers' voice coil, which is a pretty fine piece of wire, and they burn out almost instantly. -Fred W > > Actually it's more the rating of the *speaker* that's the issue. A 140W > > speaker will not handle 140W anywhere near continuously, that rating is [quoted text clipped - 19 lines] > for the speakers' voice coil, which is a pretty fine piece of wire, and > they burn out almost instantly. Indeed, the DC resistance of a speaker voice coil is typically around 60% of its' nominal impedance. More amps flow @ DC = more watts = burn up - not to mention the absence of cooling by movement. Graham >Actually it's more the rating of the *speaker* that's the issue. A 140W >speaker will not handle 140W anywhere near continuously, that rating is >music power, which assumes that the average RMS power is much lower. Absolutely. If an amp damages a speaker, it's virtually always because the speaker is under-rated compared to the amp. Not the other way round. >When an >amplifier clips hard the output is much closer to DC at the *peak* power of >the amplifier which is substantially higher than the RMS. I guess what you mean here is that the output starts to approximate to a squarewave, which has it's RMS value equal to it's peak. If that's the case, then I'm not disagreeing. >If you don't believe me, take a speaker rated at 140W, assuming it's 4 ohm, >connect it to a 24V DC source (which will cause it to draw about 140W) and >see how long it takes the voice coil to smoke. You probably won't get more >than 10-15 seconds out of it. That's not a particularly good test - no cone movement means no airflow over the coil. You'd be better off using a squarewave within the speaker's operating range. Still, again, I don't disagree with the general idea that speaker power ratings are often stupidly misleading. >Tweeters usually go first, but I've seen >*many* speakers damaged by an underpowered amp clipping, if you open one up >the voice coil is blackened. But what is it about the blackening which makes you think it was always caused by clipping? Certainly it's possible for a surprisingly small amp to knacker a surprisingly "high power" speaker, but you seem to be suggesting that the same speaker would survive if driven to the same volume level by a bigger amp running cleanly. That's only very rarely the case. Cheers, Colin. i still do not know where the amp is in my car lol ??????? > >Actually it's more the rating of the *speaker* that's the issue. A 140W > >speaker will not handle 140W anywhere near continuously, that rating is [quoted text clipped - 32 lines] > same volume level by a bigger amp running cleanly. That's only very > rarely the case. You'll be amused to know that 'does clipping cause tweeter burn out?' is a commonly recurring and much discussed topic in the pro-audio groups. Considering they *ought* to know - there's still much debate. In the end it boils down to the long term power rating of the tweeter versus the crossover frequency. Graham > > 1. The amp's power rating will be at a certain, reasonable, distortion > > level - say 5%. That 5% distortion doesn't happen *at* the clipping [quoted text clipped - 22 lines] > *many* speakers damaged by an underpowered amp clipping, if you open one up > the voice coil is blackened. Actually that's not a fair test. Any modestly rated power speaker relies on the voice coil movement to help cool it. In some cases *very much so*. The magnetic assembly also helps provide cooling. You'll see fins on the back of some high power speakers - they're not just there to look good. ;-) I've even seen some high power rock concert systems that pump forced air cooling via 'plumbing' to cool the voice coils ! Graham ( audio genius ) >>But I don't see why driving a linear amplifier into its limits (that's >>what clipping is) would cause spikes... [quoted text clipped - 7 lines] > more power than it's rating, but it sounds crap so the manufacturer > can't make any claims about this higher rating. Yes, you are absolutely correct. Clipping is one (very extreme) form of distortion. > 2. If you then continue to drive the amp harder still, and into real > clipping, the resulting sharp edges on the output waveform mean the [quoted text clipped - 3 lines] > starts producing serious power in the tweeter's range, safety margins > can get eaten into. Yup, and to clarify further, the amount of power in the distortion, while higher than normally seen at those high frequencies would be far less than the nominal power. So the end result may be that the tweeters would blow. But unlike the OPs situation, there would still be some sound from the remaining other drivers (speakers). -Fred W > >>Yeak all that limited voltage and current wreaks havoc on the > >>speakers... NOT. [quoted text clipped - 14 lines] > If that was true, the only thing I could see is possibly blowing out a > tweeter, since the woofer would have plenty of power handling capability Not compared to the square wave output capability of the amp ! That's if your ears can tolerate the abuse of course. ;-) > and the spikes would be very high frequency and so the crossover network > would shunt it away from the woofer and midrange and send only to the > tweeter. > > But I don't see why driving a linear amplifier into its limits (that's > what clipping is) would cause spikes... It doesn't. Graham ( designer of pro-audio for > 30 yrs ) > >Yeak all that limited voltage and current wreaks havoc on the > >speakers... NOT. [quoted text clipped - 7 lines] > > Virtually never happens in practice of course... Actually the amp doesn't put out 'spikes' - it puts out 'square waves' when clipping heavily. This can result in twice the continuous sine wave 'rms' power, never mind the lower 'average' power when playing music. Graham ( audio design consultant ) > >>yes i will do that today and does that mean i need to get i higher watt > >>speacker becuse these are 140 w max i really didnt thing the saab amp [quoted text clipped - 8 lines] > > Where do you people get this stuff? Happens all the time, obviously you've never worked in the consumer electronics service field. >>>>yes i will do that today and does that mean i need to get i higher watt >>>>speacker becuse these are 140 w max i really didnt thing the saab amp [quoted text clipped - 14 lines] > Happens all the time, obviously you've never worked in the consumer > electronics service field. No, you're right. I've only worked in the military and medical electronics service fields for the past 30 years... I know you can overdrive speakers and blow them. What I'm saying is that it is not due to the clipping (unless we are talking specifically about tweeters). It's due to the fact that amplifiers can put out more than their "rated" power. Most people assume a 50 watt amp can only put out 50 watts, so it's safe to hook up speakers that are rated at 50 watts. That's wrong. As Colin pointed out, the amp's rating is at a particular usable distortion level. If you overdrive the amp, you are capable of putting out more power than the "rating" but at higher distortion levels. It's the power, not that distortion that takes out the speaker(s). It might appear to be "chicken and the egg" I suppose... but significant in this case. -Fred W >>>>>yes i will do that today and does that mean i need to get i higher watt >>>>>speacker becuse these are 140 w max i really didnt thing the saab amp [quoted text clipped - 34 lines] > > -Fred W This is all very interesting and highly technical. But to lighten the mood a little, has anyone else ever taken a tiny speaker out of a broken transistor radio, and wired it up to a 100w amp to see how much it would take? I have, and it went pop quite spectacularly. Not that I'm condoning wanton destruction, you understand, I was just bored. That was after making an industrial spud gun with a compressor and a gas pipe. Boredom is a terrible thing... D ;-) > This is all very interesting and highly technical. But to lighten the mood > a little, has anyone else ever taken a tiny speaker out of a broken [quoted text clipped - 3 lines] > making an industrial spud gun with a compressor and a gas pipe. Boredom is > a terrible thing... The kids around here use PVC pipe and deodorant to make their spud cannons. They use a long piece of PVC with a cap glued on one end. Drill two holes in the cap and thread a piezo spark-gap device from a gas grille in one. The other is used to squirt the aerosol deodorant spray into. Tamp a spud part way down the pipe, charge it with hairspray, aim, spark, Thwooob! It hucks those spuds a couple of blocks. Quite ingenious actually! And relatively safe as explosive fun goes. I've never heard of anyone being killed by a potato missile. So long as they don't start spraying gasoline in their instead of hairspray... Boredom? Oh, yeah. I have an older teen-age boy... -Fred W >> This is all very interesting and highly technical. But to lighten the >> mood a little, has anyone else ever taken a tiny speaker out of a broken [quoted text clipped - 19 lines] > > -Fred W It was all quite harmless until my brother turned up and decided to fashion a crossbow-type bolt out of some garden cane and bits of sheet steel, which was to be propelled by the aforementioned spud pellet. This was quite small-bore domestic gas appliance pipe, and it worked quite well. We stopped after numerous holes in the fence and a near-miss with the dog (not to mention a telling-off by She Who Must Be Obeyed). My 7-year old isn't quite at the wanting-to-blow-stuff-up stage yet, but I'm hoping he gets there soon... D :-) >>>This is all very interesting and highly technical. But to lighten the >>>mood a little, has anyone else ever taken a tiny speaker out of a broken [quoted text clipped - 30 lines] > > D :-) OK, I take it all back. Spud guns can be seriously dangerous stuff. Check out this web site, especially the video: http://www.spudtech.com/ Yikes... -Fred W >> This is all very interesting and highly technical. But to lighten the >> mood a little, has anyone else ever taken a tiny speaker out of a broken [quoted text clipped - 19 lines] > > -Fred W Incidentally, I'm very impressed at the use of the word 'thwooob'. Haven't heard that piece of onomatopoeia for.. well... never I suppose... > Incidentally, I'm very impressed at the use of the word 'thwooob'. Haven't > heard that piece of onomatopoeia for.. well... never I suppose... Onomatopoeia huh... I think they have some kind of ointment that can help with that. ;-) -Fred W PS - that word is so cool sounding I just had to look it up. Thanks for the lesson. > Incidentally, I'm very impressed at the use of the word 'thwooob'. Haven't > heard that piece of onomatopoeia for.. well... never I suppose... A friend of mine made one that made exactly that sound, then I improved on his design with a larger combustion chamber, smaller diameter and longer barrel, well oiled with silicone spray and ether as fuel, sounds very much like a high powered hunting rifle. > The kids around here use PVC pipe and deodorant to make their spud > cannons. They use a long piece of PVC with a cap glued on one end. [quoted text clipped - 10 lines] > > Boredom? Oh, yeah. I have an older teen-age boy... I found a coleman camping lantern flint to be simpler and quite reliable. Starting fluid makes an incredible fuel, in the right ratio you can blast a potato right through a piece of 1/2" plywood. I certainly wouldn't call it relatively safe though, a direct shot would kill someone for sure. One of the more amazing things I've done was rip the top inch clean off an onopened can of nasty flavored pop, leaving the bottom portion of the can sitting undisturbed and filled to the brim. Doubt I could do that again though even if I tried a zillion times. > > This is all very interesting and highly technical. But to lighten the mood > > a little, has anyone else ever taken a tiny speaker out of a broken [quoted text clipped - 18 lines] > > Boredom? Oh, yeah. I have an older teen-age boy... Hmmmm - I wish I had that link. A home-made flame thrower ! I kid you not. Graham >Hmmmm - I wish I had that link. A home-made flame thrower ! I kid you not. Sounds good to me. The closest I ever got was when I tested my fuel injectors. http://www.stamp.plus.com/temp/Fuel_injector_testing.jpg Cheers, Colin. > This is all very interesting and highly technical. But to lighten the mood > a little, has anyone else ever taken a tiny speaker out of a broken [quoted text clipped - 3 lines] > making an industrial spud gun with a compressor and a gas pipe. Boredom is > a terrible thing... Not quite. I *did* once connect an old 12" 25 watt speaker of no useful value to a 100 watt amp to conduct a similar test also when bored. The result was quite smoky but absent of flames. In the early days of high power sound reinforcement in the UK a certain brand of amplifiers was popular since they were about the only model made in the UK and available at a sensible price unlike US models. Their internal cooling was 'optimistic' to say the least and it was popular for these to 'go DC'. Such failures were indeed known to cause some spectacular speaker fires. Graham >Happens all the time, obviously you've never worked in the consumer >electronics service field. Obviously you have, and you imagine that it affects the validity of your argument. Cheers, Colin. > yes i will do that today and does that mean i need to get i higher watt > speacker becuse these are 140 w max i really didnt thing the saab amp > can do that much. So what is the watt specs on the amp and where is i > located The *watt specs* on in car audio are utterly bogus and unreliable. They're usually measured at something like 10% distortion too ! If you had a multimeter you could check if the new speakers are still ok - either there will be some continuity across the terminals ( in which case they're ok ) or it's open circuit and they're broken. You can substitute a small wattage light bulb, battery and some wires to do this job too actually. Oh - you can't 'kill' an amp by fitting higher wattage speakers than the amp - that's ok - the other way round isn't so smart. You do need to ensure that the speakers and amp are compatible *impedances* though. In car audio is normally 4 ohms. Graham > I just got some new dual 6.5" speakers for the back. when i got them in > they really sounded nice but when i turned it up with the bass they > stoped working properly. What do you mean by 'properly' ? Do they now make a nasty grating sound ? Graham
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