sad story, blew up pair of speakers. my mistake, ignored some things. this is a noname sound system with speakers (brand labels reads as A♥WA)
i have been using this amp for years for pc music/movies. i tested the amps speaker out and dc reading is 0mV for left 10mV, which i believe is acceptable, right? so i tested with disco remixes and after like 15minutes or so, i heard harsh sounds from speaker and amps speaker protection keeps tripping off. but its too late, the left speaker is blown while the other one is shorted.
i retested amps dc and its still 0mV and 10mV on each channel. is it possible to know how much wattage the power amp is giving off? since i believe the speakers blew because its overrated(60watts, 4ohms 4" diameter cone). i have another speaker form sony SS-L90VH which is 8 ohms, but i can only search from net for its rated output at 120 RMS and i dont want these speakers to suddenly blow also. i dont have schematic for the amp but it is based on C4468/A1695 pair with 30-0-30v 150VA toroid. will my speakers possibly be safe?
thanks.
i have been using this amp for years for pc music/movies. i tested the amps speaker out and dc reading is 0mV for left 10mV, which i believe is acceptable, right? so i tested with disco remixes and after like 15minutes or so, i heard harsh sounds from speaker and amps speaker protection keeps tripping off. but its too late, the left speaker is blown while the other one is shorted.
i retested amps dc and its still 0mV and 10mV on each channel. is it possible to know how much wattage the power amp is giving off? since i believe the speakers blew because its overrated(60watts, 4ohms 4" diameter cone). i have another speaker form sony SS-L90VH which is 8 ohms, but i can only search from net for its rated output at 120 RMS and i dont want these speakers to suddenly blow also. i dont have schematic for the amp but it is based on C4468/A1695 pair with 30-0-30v 150VA toroid. will my speakers possibly be safe?
thanks.
sounds like you played too loud for too long with a pair of speakers not designed for that duty cycle. Ratings for cheap gear are usually just numbers and do not link to the ability to handle the power all the time.
Sorry about your problem, but it sounds like you had a good time! 😀
That amount of DC offset is OK for speakers. The cap to the tweeter will stop it from hitting tweeter anyway. The amp is probably fine, it is behaving as it should by protecting itself when connected to a short circuit.
Measuring amp's power is usually done with an oscilloscope, you connect a known resistor load, then increase the voltage rails with a variac until the signal starts to clip on the oscilloscope, then compute the power based on the output voltage into the load.
If amp protection is tripping, then there is a short in the speaker. Probably a shorted voice coil in one of the drivers, probably the woofer. This is the mode by which most speakers fail. The voice coil overheats when power rating is exceeded, melts the nylon insulation on the voice coil conductor, then the coils short together increasing the load until the amp protects.
You can't rely on power ratings to prevent speaker or amp damage. The only way to avoid blowing up speakers is to listen to them and don't push them. If they sound bad then they are overdriven and heading toward failure. The speakers are probably rated for 25W. Look on the individual drivers for power rating and nominal impedance. Now you know these speakers aren't loud enough for your needs. But it can work the other way too, a speaker with too low impedance played too loud can overheat a transistor. A small tube amp can distort so badly when overdriven that the HF signal can melt and damage planar ribbon tweeter, that's a case of amp too small breaks the speaker! It happened to me.
You'll need to replace the broken woofer, but if you can't identify the exact part then we can help you choose a suitable replacement part.
Open up the speakers and check everything out to see where you really are. Inspect the crossover and wires for signs of burning or melting and check that all wire connections are tight, like at speaker posts and tight connectors on the drivers. Check any electrolytic capacitors (metal cans) for bulging or leaking. Disconnect one wire from each driver, one at a time, and check their resistance with ohmmeter across the two driver tabs. A shorted voice coil will show <2ohms DC resistance. An open voice coil will show 0 Ohms. You have to disconnect one lead of the driver in order to measure the voice coil resistance.
Post a pic of front and back of any blown drivers.
Sounds like the power rating of your speakers was a bit too optimistic.
Don't rely too much on the ratings anyway, nobody runs 120W_RMS into his/her speakers all the time. Just hang a multimeter or scope on your speaker terminals to see for yourself. Real world power requirements are much lower than that.
Don't rely too much on the ratings anyway, nobody runs 120W_RMS into his/her speakers all the time. Just hang a multimeter or scope on your speaker terminals to see for yourself. Real world power requirements are much lower than that.
here are pics of the sound system + speakers...
no other identifying labels can be found like real model numbers, or power rating of amp etc. no labels also on tweeters and woofer, only a sticker at back that says 60watts, 4 ohms. anyways im not gonna use this anyways and instead use the Sony speakers. i found some service manuals and read that these L90VH are paired with system with about 100-120watts. i just want to have a possible idea or estimate on amplifier power so i wont blow these again and since i dont have oscilloscope nor a dummy load resistor.
no other identifying labels can be found like real model numbers, or power rating of amp etc. no labels also on tweeters and woofer, only a sticker at back that says 60watts, 4 ohms. anyways im not gonna use this anyways and instead use the Sony speakers. i found some service manuals and read that these L90VH are paired with system with about 100-120watts. i just want to have a possible idea or estimate on amplifier power so i wont blow these again and since i dont have oscilloscope nor a dummy load resistor.
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I usually listen to average signals that are 20dB to 30dB below the amplifiers maximum rating.
i.e. a 60W power amplifier is putting out an average of 0.6W to 60mW.
Speakers rated for domestic duty are sometimes rated for domestic duty type of reproduction, i.e. the manufacturer of the speakers receiving only 0.6W on average will work well with a 60W amplifier. The label on the back of the box states 60W. It might even state 150W because the Manufacturer has tested his speakers with a 150W amplifier reproducing non clipped music in a domestic type environment. i.e. average levels 10dB to 20dB below maximum rating.
i.e. a 60W power amplifier is putting out an average of 0.6W to 60mW.
Speakers rated for domestic duty are sometimes rated for domestic duty type of reproduction, i.e. the manufacturer of the speakers receiving only 0.6W on average will work well with a 60W amplifier. The label on the back of the box states 60W. It might even state 150W because the Manufacturer has tested his speakers with a 150W amplifier reproducing non clipped music in a domestic type environment. i.e. average levels 10dB to 20dB below maximum rating.
An amplifier rated for 120W of maximum output power, when fed with nominal mains voltage will produce more output if the test signal is clipped.
A 120W into 8r0 test load is equivalent to 43.8Vpk for an unclipped sinewave.
If the input is increased by 6dB the output is still limited to 43.8Vpk because the supply rails won't allow any more voltage. But the power delivered to the test load will have increased substantially, maybe now measuring 150W.
If the input signal were a square wave, the maximum power output would be 240W
That would do a lot of damage to domestic type speakers rated for 120W using unclipped music.
A 120W into 8r0 test load is equivalent to 43.8Vpk for an unclipped sinewave.
If the input is increased by 6dB the output is still limited to 43.8Vpk because the supply rails won't allow any more voltage. But the power delivered to the test load will have increased substantially, maybe now measuring 150W.
If the input signal were a square wave, the maximum power output would be 240W
That would do a lot of damage to domestic type speakers rated for 120W using unclipped music.
A two channel amplifier powered from an 150w transformer is a small amplifier.
If you push hard this amplifier will clip continuously. This clipping is catastrofic for loudspeakers
keep in mind as general rule,it's easyer to damendge a speaker using small amplifier than using a big one.
If you push hard this amplifier will clip continuously. This clipping is catastrofic for loudspeakers
keep in mind as general rule,it's easyer to damendge a speaker using small amplifier than using a big one.
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Many different things are at play here.... First: power handling capacity of drivers. Whatever they say, don't believe the stickers they put on those drivers. There are many different -refined- methods os measuring and specifiyng driver power handling capacity, that can grossly mislead the unsuspecting user. Generally speaking an 8" woofer with 1" dia voice coil is able to handle around 20-30 watts of real power (at the best). If you play soft jazz, or classical music, with occasional high peaks, that's OK, but rock, disco, metal, and similar types of music with high "signal density" can kill a woofer very quickly.
Think about it. The thermal resistance of such a voice coil is (depending on the former's material) somewhere around 4-8 °C/W, that means with 30 watts of continous power fed into them they can quickly heat up to 200-240 °C, where paper, and the insulation on the V.C. wire starts to burn, and melt.
With black anodized aluminium former the situation is somewhat better, but still, no way they can handle 100 Watts of continous power for too long.
Second, a quite often discussed fact, that a lower power amplifiers can fry a speaker much easier than high power ones. Why? A low power amplifier- when overdriven- quickly runs into clipping mode, that means, the "clipped" portion of the signal shows up on the output as DC, which seriously increases the heat dissipation on the voice coil, burning it sooner or later. An easy way to prevent this, is show some common sense, because clipping means distortion, so when you hear your speakers distorting, just turn the volume down a bit, so you might save your speakers.
Of course this is not easy to excercise in the middle of a heated-up party, but then you must face the consequences.....
I just saw an almost "parallel" comment, where Thimios said the same things....
Think about it. The thermal resistance of such a voice coil is (depending on the former's material) somewhere around 4-8 °C/W, that means with 30 watts of continous power fed into them they can quickly heat up to 200-240 °C, where paper, and the insulation on the V.C. wire starts to burn, and melt.
With black anodized aluminium former the situation is somewhat better, but still, no way they can handle 100 Watts of continous power for too long.
Second, a quite often discussed fact, that a lower power amplifiers can fry a speaker much easier than high power ones. Why? A low power amplifier- when overdriven- quickly runs into clipping mode, that means, the "clipped" portion of the signal shows up on the output as DC, which seriously increases the heat dissipation on the voice coil, burning it sooner or later. An easy way to prevent this, is show some common sense, because clipping means distortion, so when you hear your speakers distorting, just turn the volume down a bit, so you might save your speakers.
Of course this is not easy to excercise in the middle of a heated-up party, but then you must face the consequences.....
I just saw an almost "parallel" comment, where Thimios said the same things....
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thanks everyone for the comments. i never thought "clipping" passes DC to speakers, that might have been possibly the reason. while i was doing te test before speakers blew up, i was monitoring V+ and it was stable at 42-43vdc at no signal, and often dropped to 38-39v during heavy bass. was there clipping there or is it a sign since voltage dropped?
A 30-0-30 150VA toriod will produce 100 watts per channel at 4 ohms. Not indefinitley, but over 15 minutes - sure. Heavily clipped you can exceed that. But the average power is probably no more than half, or about 50 watts. There was probably no more than 50 watts going to the speaker when it died. 1" VC is good for 20-30 watts of average power. A 4" woofer playing bass heavy "disco" music will be driven WAY beyond Xmax, and when you do that the thermal power handling is further reduced. An 8" or larger bass driver with a 1.5" VC would take it with no problems, but tweeters in such a system would still die from the excessive clipping unless they were way oversized with the intention of being used this way. I seroiusly doubt the Sony's would be up to the task either. You could likely DIY something, but it wouldn't be cheap or small.
Clipping does not put DC to the speaker. It simply raises the average power level. Since clipping contains a lot of harmonics, it also raises the average power level sent to the tweeter - but at an increased rate compared to the woofer. This is why tweeters usually fail first when clipping. For the woofers to fail first, you've got to be really beating the tar out of it. Turning up the bass with such a small woofer does make it easier to overdrive it.
With the supply dropping to 38V, you're putting out closer to 140 watts peak. That supply is holding up better than I would have expected from an Aiwa system. That doesn't help the speakers any 🙂
hmm.. so in order to continue using the same amp, ill need a higher rating speaker system. in order to use the sony speakers ill need a diy amp-which what was i really planning in the 1st place, but only held back because it would mean getting a new toroid and power caps(which are not cheap).
Higher rated speakers would make the most sense to spend money on. Building yourself a bigger amplifier and doing the same thing with it will cause the Sony speakers to suffer the same fate. You could build a 20 watt amp and go ahead and 'blast' it, but you won't be satisfied with that.
Take this as your cue to get into speaker building. You can build them bulletproof if you set out to do this in the first place. You won't want to use a 4" woofer - that's too small for a midrange.
Take this as your cue to get into speaker building. You can build them bulletproof if you set out to do this in the first place. You won't want to use a 4" woofer - that's too small for a midrange.
No.
That is not what you are being told.
We are saying that clipping creates distortion, audible distortion.
Clipping sends out more power.
A sensible operator would turn down the volume control when the distortion becomes evident.
It is a senseless operator that destroys a speaker.
I have done it only once in ~48years.
Higher efficiency, not higher rating. You'll need a lot less power to bust your ears with a 95 dB/w speaker system, than the probable ~83dB of the Aiwa.
I usually recommend a cheap pro coaxial system in situations like this, if you can live with the size. The Eminence CX-12 and associated tweeter will deliver more acoustic output than you will ever need in an average domestic space, and with under 20 watts of amplifier power.
There's a nice thread in the multi-way section with some designs and hints on the entire CX series.
Higher efficiency AND higher rating. It's not too hard to beat a 4" woofer with a 1" coil for power handling. A typical 6" car coax will do that.
I'd steer towards a 10" 3 way. An inexpensive 10 will handle the watts and provide satisfying bass. 3-way lets you cross a tweeter high enough so you can use a cheap $15 bullet horn, which will need to be padded some 10dB. The pad will save it from overpower when you do clip the tar out of the amp. A good 5 or 6" mid with a 1.5" coil can handle a LOT of power crossed over at 800 Hz (typical of a pre-made 3 way). Get one that's smooth on top and about 5dB LESS sensitve than the woofer. Appropriate 10" pro drivers are $40-45, and a mid less than $20. Similar home stereo drivers (say, Dayton Classic) will be less money but give up the efficiency advantage. More low bass, though. Decide what's important. Either way when you do get a real amplifier, the speakers will be up to it. And the amp you have now will overheat and die long before the speakers cry uncle.
Pro coaxials and "econowave" designs are good and are a higher fidelity solution but will end up costing more because the HF drivers are expensive and the crossovers need to be carefully designed. A great idea if you're willing to embark on such a project.
I'd steer towards a 10" 3 way. An inexpensive 10 will handle the watts and provide satisfying bass. 3-way lets you cross a tweeter high enough so you can use a cheap $15 bullet horn, which will need to be padded some 10dB. The pad will save it from overpower when you do clip the tar out of the amp. A good 5 or 6" mid with a 1.5" coil can handle a LOT of power crossed over at 800 Hz (typical of a pre-made 3 way). Get one that's smooth on top and about 5dB LESS sensitve than the woofer. Appropriate 10" pro drivers are $40-45, and a mid less than $20. Similar home stereo drivers (say, Dayton Classic) will be less money but give up the efficiency advantage. More low bass, though. Decide what's important. Either way when you do get a real amplifier, the speakers will be up to it. And the amp you have now will overheat and die long before the speakers cry uncle.
Pro coaxials and "econowave" designs are good and are a higher fidelity solution but will end up costing more because the HF drivers are expensive and the crossovers need to be carefully designed. A great idea if you're willing to embark on such a project.
wow! those are some professional speakers there. i don't think i have the tools to make baffles for that unless i will have it outsourced.
anyways, i opened up the Sony SSL90VH speakers and did some measurements and screenshots.
speaker diameter(up to outer metal frame) is 6 3/4", 3 3/8" height. it has double magnet with diameter at 3". voice coil is probably 1-1 2/8". probably good for like 30 watts continous, right?
anyways, i opened up the Sony SSL90VH speakers and did some measurements and screenshots.
speaker diameter(up to outer metal frame) is 6 3/4", 3 3/8" height. it has double magnet with diameter at 3". voice coil is probably 1-1 2/8". probably good for like 30 watts continous, right?
I am paranoid about blowing up speakers.
I usually use an amp with half the power of the speakers.
So even with a square wave it will only hit the speakers highest power.
I also use a DC speaker protector circuit which turns off a relay if there is DC on speaker lead.
Someone will probably pooh pooh my views but I have yet to blow up a speaker in 40 years and that's with home, disco and guitar use.
I usually use an amp with half the power of the speakers.
So even with a square wave it will only hit the speakers highest power.
I also use a DC speaker protector circuit which turns off a relay if there is DC on speaker lead.
Someone will probably pooh pooh my views but I have yet to blow up a speaker in 40 years and that's with home, disco and guitar use.
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