RoHo Posted June 15, 2023 Posted June 15, 2023 1 hour ago, tripitaka said: Not to dispute what you say, but 'AC nature' and 'sinusoidal nature' aren't the same thing. According to your argument (which incidentally I also believed until reading this thread) you could happily feed a sinusoidal DC wave into a speaker and it would be fine (though you wouldn't get music, of course). Yet, as a result of reading this thread, I now believe the speakers would blow, since there would be recurring periods of zero resistance ('infinite' current flow) that would burn the coils. As usual, I claim no expertise in anything. All we need now is a volunteer to test this hehe Beware the simplistic “just feels right” explanation . To add to the other comprehensive replies, of course music is not the same as constant frequency and amplitude sine wave, yet both are AC. Music is the sum of many sine waves of different frequency and amplitude. The constant, high level sine wave will be at maximum twice every cycle. In a music signal the max amplitude is usually in the bass and will only occur in occasional peaks and other frequencies may only ever reach 10% (I’m guessing) of this level. So which signal poses more of a problem if the volume is wound up to 11? And you use this information to deduce what types of music pose most risk to speakers.
tripitaka Posted June 15, 2023 Posted June 15, 2023 7 minutes ago, RoHo said: Beware the simplistic “just feels right” explanation . To add to the other comprehensive replies, of course music is not the same as constant frequency and amplitude sine wave, yet both are AC. Music is the sum of many sine waves of different frequency and amplitude. The constant, high level sine wave will be at maximum twice every cycle. In a music signal the max amplitude is usually in the bass and will only occur in occasional peaks and other frequencies may only ever reach 10% (I’m guessing) of this level. So which signal poses more of a problem if the volume is wound up to 11? And you use this information to deduce what types of music pose most risk to speakers. I think we can all agree that has been obvious from the start.
tripitaka Posted June 15, 2023 Posted June 15, 2023 9 hours ago, aussievintage said: That's a 50 volt peak to peak ac wave form with 25 volt dc offset added to it. Thanks @aussievintage 1. I will edit my post to include your terminology, since it doesn't affect the thrust of my argument in the least. 2. Your terminology reflects the obvious truth that what I have (rightly or wrongly) described as a sinusoidal DC wave can be constructed as the superposition of a -25V DC waveform and a 50V AC (peak to peak) waveform. 3. None of this changes what I understand to be a fact, which is that if the current is not periodically changing it's direction (in addition to its changing amplitude) then it has no business being called an alternating current.
aussievintage Posted June 15, 2023 Posted June 15, 2023 (edited) 4 hours ago, tripitaka said: superposition of a -25V DC waveform Well, it's +25V actually, the way you framed the example (not that it matters to the speaker - it just won't like it anyway ). Also, as it's a constant voltage level (of 25VDC) then I probably would not describe it as a waveform. but yeah... Edited June 15, 2023 by aussievintage
aussievintage Posted June 15, 2023 Posted June 15, 2023 14 hours ago, tripitaka said: but 'AC nature' and 'sinusoidal nature' aren't the same thing. Why not? As I said earlier, any AC waveform, can be analysed mathematically to show it is the addition of many sinewaves of varying amplitudes and frequencies. So even a squarewave is just a bunch of sinewaves. 1
tripitaka Posted June 15, 2023 Posted June 15, 2023 47 minutes ago, aussievintage said: Well, it's +25V actually, the way you framed the example (not that it matters to the speaker - it just won't like it anyway ). Our truly fundamental point of agreement is that the speaker will not like it ...coz it's DC. All I have tried to do is take a step further to answering the OP question ('why did my speaker blow') by arguing WHY it is that speakers specifically don't like dc. And to my understanding it's because there is no resistance (which in turn is simply due to the current always being in the same direction). I never knew this previously, nor has anybody else has said it within the thread, so maybe it might be of interest to someone, who knows! We all good?
aussievintage Posted June 15, 2023 Posted June 15, 2023 44 minutes ago, tripitaka said: nd to my understanding it's because there is no resistance (which in turn is simply due to the current always being in the same direction). I never knew this previously, nor has anybody else has said it within the thread, so maybe it might be of interest to someone, who knows! Well, there is less resistance, not zero, in a speaker voice coil, and to be strictly correct, we are talking about impedance not just resistance. With DC, the only impedance is resistance, but with AC we also have inductance and capacitance. Now the speaker voilce coil, because it is a coil, has inductance as well as resistance, and so the amount of current that flows is less, than if it was DC. Hence a speaker will burn out due to the higher current that flows when it is presented with DC. 48 minutes ago, tripitaka said: We all good? Of course. 1
Richard Tremain Posted June 16, 2023 Posted June 16, 2023 NAKSA /ASPEN etc. Does anyone on this forum wear a seatbelt?
andyr Posted June 16, 2023 Posted June 16, 2023 3 hours ago, Richard Tremain said: NAKSA /ASPEN etc. Does anyone on this forum wear a seatbelt? Not quite sure of the reason behind your strange comment, RT - but I have used AKSA amps for about 20 years and never had a problem like the OP. Mind you ... I have built all the amps myself - so I know they are built right. None of the 6 or so AKSA amps I have built have spkr protection circuits - and I have never blown any drivers up - even when running the ribbons on my active Maggies directly (ie. with no 'protective' series capacitor).
Richard Tremain Posted June 17, 2023 Posted June 17, 2023 15 hours ago, andyr said: Not quite sure of the reason behind your strange comment, RT - but I have used AKSA amps for about 20 years and never had a problem like the OP. Mind you ... I have built all the amps myself - so I know they are built right. None of the 6 or so AKSA amps I have built have spkr protection circuits - and I have never blown any drivers up - even when running the ribbons on my active Maggies directly (ie. with no 'protective' series capacitor). Post not directed to users such as your self. But to others such as the OP it is one thing to wire up to average cost spk and disintigrate 2 drive units. Quite another if cherished non replaceable units or $10000 speakers. Placing reliance on half constructed kit amplifiers being used by people who have no understanding of speaker protection Very Scary! 1
tripitaka Posted June 17, 2023 Posted June 17, 2023 1 hour ago, Richard Tremain said: Post not directed to users such as your self. But to others such as the OP it is one thing to wire up to average cost spk and disintigrate 2 drive units. Quite another if cherished non replaceable units or $10000 speakers. Placing reliance on half constructed kit amplifiers being used by people who have no understanding of speaker protection Very Scary! Definitely food for thought I'm embarrassed to say I don't even know if my monoblocks have a cutout circuit and my speakers are way more than $10000. Hmmm!
Richard Tremain Posted June 17, 2023 Posted June 17, 2023 Regarding reliability i have a Naim Pre/Power and a original Vallhalla Board both been mains connected 24/7 for 40yrs anyone beat that? 1
mbz Posted June 17, 2023 Posted June 17, 2023 18 hours ago, andyr said: I have used AKSA amps for about 20 years and never had a problem like the OP. Mind you ... I have built all the amps myself - so I know they are built right. None of the 6 or so AKSA amps I have built have spkr protection circuits - and I have never blown any drivers up - even when running the ribbons on my active Maggies directly (ie. with no 'protective' series capacitor). 1 hour ago, tripitaka said: I'm embarrassed to say I don't even know if my monoblocks have a cutout circuit and my speakers are way more than $10000. Sorry guys, but from an electronics perspective above comments almost qualify you (actually your speakers) for a "Darwin award". Sadly silicon does fail. All it takes is a driver or output transistor c-e short which will dump near rails voltage (30-90Vdc?) on your speakers. Also, if you run largish power amps then the common relay based protection circuit is no guarantee as pointed out by the diyaudio guys, https://www.diyaudio.com/community/threads/output-relays.191449/ They did some work on using power FET's instead of relays for such amps, an interesting read. For new-ish gear you would be unlucky to blow a transistor but each time you run the amp, you roll the dice. I don't have a budget to buy new so I run vintage amps, I was fortunate to pick up some Osborn epitome's, rule 1, no speaker protection then the amp doesn't play... If you have smaller amps then kits are available on the bay from our good friends from china, need to check the relay current rating against the amp, probably better to bin the chinese relay (it's a "fake" probably automotive with questionable contact material) and replace with a quality Omron or ... Spkr fuses are too slow 1
tripitaka Posted June 17, 2023 Posted June 17, 2023 1 minute ago, mbz said: Sorry guys, but from an electronics perspective above comments almost qualify you (actually your speakers) for a "Darwin award". Sadly silicon does fail. All it takes is a driver or output transistor c-e short which will dump near rails voltage (30-90Vdc?) on your speakers. Also, if you run largish power amps then the common relay based protection circuit is no guarantee as pointed out by the diyaudio guys, https://www.diyaudio.com/community/threads/output-relays.191449/ They did some work on using power FET's instead of relays for such amps, an interesting read. For new-ish gear you would be unlucky to blow a transistor but each time you run the amp, you roll the dice. I don't have a budget to buy new so I run vintage amps, I was fortunate to pick up some Osborn epitome's, rule 1, no speaker protection then the amp doesn't play... If you have smaller amps then kits are available on the bay from our good friends from china, need to check the relay current rating against the amp, probably better to bin the chinese relay (it's a "fake" probably automotive with questionable contact material) and replace with a quality Omron or ... Spkr fuses are too slow Ok I am suitably chastised, but I also run pretty big amps so is there any hope?
mbz Posted June 17, 2023 Posted June 17, 2023 Not meant to chastise only draw attention, you guys have gear I dream about, would be sad to read something got smoked. Large amps (70-90Vdc rails) then consider the fet type as per diyaudio, they did produce a pcb but it uses a now hard to find IC. Another alternative is http://www.wattsabundant.com/ they designed a protection kit for the Phase Linear 400 I need to do a bit more research on this, I do have boards from both diyaudio and watts abundant. I have 3xPL400's in the shed which will need kits. Kits for smaller amps can be had for about $25- including a transformer and fuse(s). 1
mbz Posted June 17, 2023 Posted June 17, 2023 1 hour ago, tripitaka said: I'm embarrassed to say I don't even know if my monoblocks have a cutout circuit and my speakers are way more than $10000. I would be expecting that the matching amp would also be suitably priced and should include some sort of protection circuit, check you owners manual or google...
tripitaka Posted June 17, 2023 Posted June 17, 2023 (edited) 39 minutes ago, mbz said: Not meant to chastise only draw attention, you guys have gear I dream about, would be sad to read something got smoked. Large amps (70-90Vdc rails) then consider the fet type as per diyaudio, they did produce a pcb but it uses a now hard to find IC. Another alternative is http://www.wattsabundant.com/ they designed a protection kit for the Phase Linear 400 I need to do a bit more research on this, I do have boards from both diyaudio and watts abundant. I have 3xPL400's in the shed which will need kits. Kits for smaller amps can be had for about $25- including a transformer and fuse(s). Quite seriously, it is very kind of you to put this info up. And typical of this forum of abundant expertise. So, a decade-old review from Audioholics says that my Emotiva XPA-1L are protected against 'shorted speaker connections', which indicates to me I should be ok Edit: Hang on, that protects the amp not the speakers. So, I'm none the wiser Edited June 17, 2023 by tripitaka
Jakeyb77_Redux Posted June 17, 2023 Posted June 17, 2023 (edited) I run one of these on my DIY Holton https://sklep.toroidy.pl/en_US/p/Inrush-current-limiter-for-high-power-transformers/454 Also a cheap Chinese speaker protection board like stated above. Both work as they should (tested) and I would not run an amp to my speakers without them Edited June 17, 2023 by Jakeyb77_Redux 1 1
aussievintage Posted June 17, 2023 Posted June 17, 2023 (edited) I find the output transformers on my valve amps to be a pretty safe way of blocking DC from my speakers. Chances of a shorted winding are quite slim, so I don't use any further protection. Edited June 17, 2023 by aussievintage 2
andyr Posted June 17, 2023 Posted June 17, 2023 4 minutes ago, aussievintage said: I find the output transformers on my valve amps to be a pretty safe way of blocking DC from my speakers. Chances of a shorted winding are quite slim, so I don't use any further protection. Great advantage of a tube amp! 1
aussievintage Posted June 17, 2023 Posted June 17, 2023 3 minutes ago, andyr said: Great advantage of a tube amp! Real early transistor amps used transformers too. I had a nice little integrated amp made by Peak back in the 70s (or maybe late 60s) that had transformers in it. Weight and expense made designers find ways around them. Of course cheap ones also suffered bandwidth problems, but I do recall some esoteric audiophile designs still using interstage and output transformers. 1
mbz Posted June 17, 2023 Posted June 17, 2023 2 hours ago, tripitaka said: So, a decade-old review from Audioholics says that my Emotiva XPA-1L are protected against 'shorted speaker connections', which indicates to me I should be ok Edit: Hang on, that protects the amp not the speakers. So, I'm none the wiser The owners manual only talks on a high level, no detail as to what scenarios are protected. No schematic available. The unit is microprocessor controlled which initiates the protection acdtions. Excessive Vdc is a basic fault, the unit has speaker short protection, this is a more advanced feature so would expect Vdc covered. Possibly the unit uses a relay, you may hear a faint relay click 3-8 seconds after power on or at speaker selection on some makes. You are probably ok but would be nice to know for sure. 2 hours ago, Jakeyb77_Redux said: Also a cheap Chinese speaker protection board like stated above. Both work as they should (tested) and I would not run an amp to my speakers without them Good work, keep in mind the relay needs to be suitably rated. As per the diyaudio guy, the relay contacts may "weld" under high currents (for larger amps). 1 1
Addicted to music Posted June 17, 2023 Posted June 17, 2023 2 hours ago, Jakeyb77_Redux said: I run one of these on my DIY Holton https://sklep.toroidy.pl/en_US/p/Inrush-current-limiter-for-high-power-transformers/454 Also a cheap Chinese speaker protection board like stated above. Both work as they should (tested) and I would not run an amp to my speakers without them An inrush current limiter is not a speaker protector. What it does it limits the inrush current on switch on. To market the device to protect transformers is partially correct. The reason you’ll need this is that most power amplifiers deploy a massive bank of electrolytic filter caps that is the main DC supply for your amplifier module. When the amp is off, these huge banks of capacitors are discharged and have around the zero volt mark in respect to ground. When you switch on, the caps represent short in the electrical, in other words it’s a short to the building electrical of 230VAC. As the caps charges and raises its voltage levels, this short is momentarily and gradually the impedance to the mains rises hence if you have poor mains supply you’ll notice the lights will dim when you switch the amp on! What a soft start does is it places a resistor: around the 10 ohm in series of your mains active when the amplifier is powering up! There is a RC network or a timer that operates a relay that shorts this resistor. Other types of soft starts will use a triac that limits the current on switch on and then slowly bring that up to speed. Inrush current wears contact switches and also places a huge stress of the electrical wiring of the building. Also transformers isolating speakers can be advantage in Speaker protection, but what’s protecting that transformer winding when DC is present? No winding like any DC applied, even with solenoids that are specified 24DC don’t survive for long if you place a 24VDC across it! Most solenoids that require a DC applications usually have a safe guard in place where it only operates a specific time: <20sec in service mode incase service rep forgets to disengage it! Myths that assumes DC on mains is just that, If you have any levels of DC on the mains, that primary coil will get hot and if it’s high enough you start to smell it, been there done that! 1
Jakeyb77_Redux Posted June 17, 2023 Posted June 17, 2023 1 minute ago, Addicted to music said: An inrush current limiter is not a speaker protector. What it does it limits the inrush current on switch on. To market the device to protect transformers is partially correct. The reason you’ll need this is that most power amplifiers deploy a massive bank of electrolytic filter caps that is the main DC supply for your amplifier module. When the amp is off, these huge banks of capacitors are discharged and have around the zero volt mark in respect to ground. When you switch on, the caps represent short in the electrical, in other words it’s a short to the building electrical of 230VAC. As the caps charges and raises its voltage levels, this short is momentarily and gradually the impedance to the mains rises hence if you have poor mains supply you’ll notice the lights will dim when you switch the amp on! What a soft start does is it places a resistor: around the 10 ohm in series of your mains active when the amplifier is powering up! There is a RC network or a timer that operates a relay that shorts this resistor. Other types of soft starts will use a triac that limits the current on switch on and then slowly bring that up to speed. Inrush current wears contact switches and also places a huge stress of the electrical wiring of the building. Also transformers isolating speakers can be advantage in Speaker protection, but what’s protecting that transformer winding when DC is present? No winding like any DC applied, even with solenoids that are specified 24DC don’t survive for long if you place a 24VDC across it! Most solenoids that require a DC applications usually have a safe guard in place where it only operates a specific time: <20sec in service mode incase service rep forgets to disengage it! Myths that assumes DC on mains is just that, If you have any levels of DC on the mains, that primary coil will get hot and if it’s high enough you start to smell it, been there done that! I know what the in rush soft start is for. I didn’t say it was for speaker protection anywhere in my post. I just mentioned I install both. It is however good at stopping the large thump at switch on which is not so great for speakers. 1
Addicted to music Posted June 17, 2023 Posted June 17, 2023 3 minutes ago, Jakeyb77_Redux said: I know what the in rush soft start is for. I didn’t say it was for speaker protection anywhere in my post. I just mentioned I install both. It is however good at stopping the large thump at switch on which is not so great for speakers. This is what you said: 2 hours ago, Jakeyb77_Redux said: I run one of these on my DIY Holton https://sklep.toroidy.pl/en_US/p/Inrush-current-limiter-for-high-power-transformers/454 Also a cheap Chinese speaker protection board like stated above. Both work as they should (tested) and I would not run an amp to my speakers without them
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