21stcenturyquaker Posted June 11, 2023 Posted June 11, 2023 Yesterday I was enjoying music at a decent volume - but not remotely distorted - when I heard a short noise through the right speaker: the sound went quiet and both bass drivers of the right speaker began to smoke. Speakers are 9 year old epos elan 35 - rarely played loud but the offending speaker was toppled over by children last year. Obviously I don't want to plug another set of speakers in incase they suffer the same fate. I assume the power amplifier is the most likely candidate. How do I test it to see if it's the culprit? Recommendations and suggestions would be most welcome. Philip.
Dean Gale Posted June 11, 2023 Posted June 11, 2023 Your Amplifier is putting DC onto the voice coils of your speakers , don't sacrifice another pair the same thing will happen . Do the speakers have fuses ? Get your amp checked straight away
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 Thanks Dean; I don't think the speakers have fuses. I'll get it checked out.
tripitaka Posted June 11, 2023 Posted June 11, 2023 (edited) On 11/06/2023 at 2:57 PM, Dean Gale said: Your Amplifier is putting DC onto the voice coils of your speakers , don't sacrifice another pair the same thing will happen . Do the speakers have fuses ? Get your amp checked straight away Do passive speakers have fuses? That's a new one on me. I've blown my fair share of speakers and it was usually me playing them too loud (coz when the sound is not distorted one doesn't always realize how loud it is) BTW, what other kind of current would you expect an amplifier to be putting into a speaker, if not Direct Current? Edit: PS. I've been asking idiotic questions for years on this forum, it's how I learn Edited June 12, 2023 by tripitaka
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 They definitely weren't being played overly loud at the time of failure.
rocky500 Posted June 11, 2023 Posted June 11, 2023 Hi Philip What is the brand and model of the power amplifier?
tripitaka Posted June 11, 2023 Posted June 11, 2023 2 hours ago, 21stcenturyquaker said: They definitely weren't being played overly loud at the time of failure. It's possible there is a short of some kind and your amp is outputting max voltage on one channel - easy enough to check with a $5 dollar multimeter from Jaycar. I would also be looking at an internal speaker short due to your children topping it over. Open it and take a look? 1
Addicted to music Posted June 11, 2023 Posted June 11, 2023 4 hours ago, Dean Gale said: Your Amplifier is putting DC onto the voice coils of your speakers , don't sacrifice another pair the same thing will happen . Get your amp checked straight away Most likely possibility is that something has failed and is outputting DC. Get a cheap multimeter set it to max DC volts range to see if output has DC. 4 hours ago, tripitaka said: Do passive speakers have fuses? That's a new one on me. some do, if you check the Magnaplanar range out, they have a fuse in series with the input. 4 hours ago, tripitaka said: I've blown my fair share of speakers and it was usually me playing them too loud (coz when the sound is not distorted one doesn't always realize how loud it is) This is the other cause, playing loud can over heat the voice coil to the point where it will just stop and you have an open circuit in the coil. Driving amplifiers clipping (Beyond the Rail voltage where the limit is will output DC that’s not good. Any DC energy will heat the coil fast. 1 1
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 With the multimeter set at DCV 1000 I get a reading of 039 in the right channel. Nothing in the left channel. Does that mean it's putting out 39 volts DC in the right channel? 2
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 This is so weird: I bought these speakers 9 years ago to replace another pair of speakers that had the right channel speaker driver blow - the cause: a different power amp putting out 37 V DC according to the technician at the time. 1 1
ThirdDrawerDown Posted June 11, 2023 Posted June 11, 2023 Glad you've tracked it down. I came here late to suggest the pure quill DC injection is happening from your amp to the speakers. Cutout or fuses are required. or a delay circuit if it's ever possible when you turn the amp on. Crisped drivers. I love the smell of napalm cigarette smoke in the mornings NOT! It costs manufacturers very little to put in protection, but even so, too few do it. 1
andyr Posted June 11, 2023 Posted June 11, 2023 16 minutes ago, ThirdDrawerDown said: It costs manufacturers very little to put in protection, but even so, too few do it. Aah but fuses ... degrade the sound, Murray! I removed the fuses on the mid-range panels and ribbons of my Maggies ... long ago.
andyr Posted June 11, 2023 Posted June 11, 2023 6 hours ago, 21stcenturyquaker said: Hi; it's a Aspen Naksa 70. I run 2x NAKSA 80s on my active spkrs - and they should only be putting out minimal DC, if they have been adjusted to spec. If you've measured 39v DC in one channel ... then something is seriously wrong with that channel of the amp. Although as @tripitakasaid ... maybe there's a fault with the spkr that was knocked over - which has caused the fault in the amp? You need to get in touch with Hugh to request a circuit diagram for the N70, so you can give this to a tech. 1
Jakeyb77_Redux Posted June 11, 2023 Posted June 11, 2023 58 minutes ago, andyr said: Aah but fuses ... degrade the sound, Murray! I removed the fuses on the mid-range panels and ribbons of my Maggies ... long ago. Lots of things are more pleasing without protection but new speakers and child support are expensive 2 10
tripitaka Posted June 11, 2023 Posted June 11, 2023 7 hours ago, 21stcenturyquaker said: This is so weird: I bought these speakers 9 years ago to replace another pair of speakers that had the right channel speaker driver blow - the cause: a different power amp putting out 37 V DC according to the technician at the time. Not the same brand of amp, were they.?
Addicted to music Posted June 11, 2023 Posted June 11, 2023 (edited) 5 hours ago, Jakeyb77_Redux said: Lots of things are more pleasing without protection but new speakers and child support are expensive Speakers are usually one of. Child support is continuous to the age of 18 Edited June 11, 2023 by Addicted to music
Addicted to music Posted June 11, 2023 Posted June 11, 2023 7 hours ago, ThirdDrawerDown said: . Cutout or fuses are required. or a delay circuit if i fuses are useless for speakers. A speaker protection should have DPDT relays that will physically disconnect your output if it detects DC or if the signal starts to clip, fuses cannot do this as this requires logic. Fuses only protect for over current drawn. There is no protection that I know of if you overdrive a speaker, this is also a major cause of speaker failure. Lot of people, me included will use a powerful amp to drive speakers, you just have to be careful of what you’re doing. 1
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 2 hours ago, tripitaka said: Not the same brand of amp, were they.? No, previous amp was a Naim 250. 1
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 9 hours ago, andyr said: You need to get in touch with Hugh to request a circuit diagram for the N70, so you can give this to a tech. Thank you Andy -I'll get on to Hugh.
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 (edited) 9 hours ago, andyr said: maybe there's a fault with the spkr that was knocked over - which has caused the fault in the amp? There's certainly a fault with it now Edited June 11, 2023 by 21stcenturyquaker 1
VanArn Posted June 11, 2023 Posted June 11, 2023 A high DC voltage at the amplifier's speaker terminals is an indication that the output transistors have failed. Modern high power direct coupled transistor amplifiers should at least include foldback protection circuits. Fuses are necessary to prevent expensive mishaps such as burnt circuit boards and power transformers. Fast acting relay ccts. are an additional measure to avoid speaker damage. 3
21stcenturyquaker Posted June 11, 2023 Author Posted June 11, 2023 2 minutes ago, VanArn said: A high DC voltage at the amplifier's speaker terminals is an indication that the output transistors have failed. The previous Naim amplifier putting out 37 V DC did indeed have a faulty transistor.
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