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Help me diagnose what is destroyed


mantis

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That was a lot of fun, I have no idea what caused it, it was an act of god. Huge sound, shook the house, no idea what frequency ranges, no idea if it was 2 speakers or 1. Anyway, they sound shot. The bass isn't as clear, the mids sound ok, the tweeters are definately screwed up (They are staticky even though they do make sound). I put a sine wave generator and the speakers do it without big dips, but they don't sound right. How should I go about figuring out exactly what is ruined so I can get these things back up. Measure ohms across woofers to see if they are out of spec? They were 4 and 3.8 a few weeks ago. Should I look to see if something in the crossover blew up? I have no idea what caused it, where it came from, or what so I have no idea where to start.

Thank you, please help!!!

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That was a lot of fun, I have no idea what caused it, it was an act of god. Huge sound, shook the house, no idea what frequency ranges, no idea if it was 2 speakers or 1. Anyway, they sound shot. The bass isn't as clear, the mids sound ok, the tweeters are definately screwed up (They are staticky even though they do make sound). I put a sine wave generator and the speakers do it without big dips, but they don't sound right. How should I go about figuring out exactly what is ruined so I can get these things back up. Measure ohms across woofers to see if they are out of spec? They were 4 and 3.8 a few weeks ago. Should I look to see if something in the crossover blew up? I have no idea what caused it, where it came from, or what so I have no idea where to start.

Thank you, please help!!!

Hi there;

What were you doing with the stereo when you heard the noise?

We need to find out what caused the problem first.

Sound source?

Amplifier?

Does the amplifier have speaker fuses?

What size and type?

After the major noise, did the music or whatever continue at a lower level?

Have you done anything in the way of modifying the speakers or amplifier?

If you are measuring the impedance at the terminal connections, it is not the mids or tweeters, it is only the woofers that you are testing.

What size and type of fuses are you using on each speaker?

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Hi, I'm sorry, it wasn't a spike, it was a prolonged spike. It was a constant noise, I should have worded that differently.

It was massive.

Speakers were connected to Adcom GFA-2 amplifier with standard speaker wire.

Adcom GFA-2 was connected to Marantz 2270 preamp section with a standard RCA wire.

Marantz 2270 was connected to my soundcard with mogami 2524 1/4 to rca wire.

Marantz gain was set to 0.

Soundcard gain was set to 0.

I turned marantz on first, so as to avoid any hum or pop from turning it on.

After marantz is on, I turn the adcom on. As soon as it clicked on the sound was HUGE and full, it sounded like a huge 50HZ or something, I couldn't tell it was just so much and so sudden. I rushed to turn things off but they were already off. If I recall correctly, As soon as it came on I was situated in front of the soundcard and did not expect teh sound so I rushed forward and turned the knob of the soundcard all the way down but it was already there, so I ran to the amp and turned it off.

So I figured I blew it all and unplugged it all. I have no idea what caused it, there should not have been any noise, everything was set correctly. A few hours later, I plugged the soundcard directly into the amplifier and tested it out. The tweeters were at a significantly lower volume than before, and things sounded off. This was beyond the impedance mismatch between the output of the card and the input on the amp.

The adcom shuts off if it receives a load below about 3 ohms, and has fuses for each channel, however it is older and I cannot confirm if that works! I have never had the issue before or sense, the marantz has never acted up like that and neither has the soundcard. The adcom has been used a bunch and had never done that.

Now, I notice that even with no music playing, there is a slight bit of noise coming out of the tweeters, I guess that means they are blown. The mids sound good though, the pots turn em up loud and there doesn't seem to be any noise.

The woofers sometimes sound good, but I can't even tell anymore, I just don't know.

Hope that provides something. Thanks.

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Guest matty g
Hi, I'm sorry, it wasn't a spike, it was a prolonged spike. It was a constant noise, I should have worded that differently.

It was massive.

Speakers were connected to Adcom GFA-2 amplifier with standard speaker wire.

Adcom GFA-2 was connected to Marantz 2270 preamp section with a standard RCA wire.

Marantz 2270 was connected to my soundcard with mogami 2524 1/4 to rca wire.

Marantz gain was set to 0.

Soundcard gain was set to 0.

I turned marantz on first, so as to avoid any hum or pop from turning it on.

After marantz is on, I turn the adcom on. As soon as it clicked on the sound was HUGE and full, it sounded like a huge 50HZ or something, I couldn't tell it was just so much and so sudden. I rushed to turn things off but they were already off. If I recall correctly, As soon as it came on I was situated in front of the soundcard and did not expect teh sound so I rushed forward and turned the knob of the soundcard all the way down but it was already there, so I ran to the amp and turned it off.

So I figured I blew it all and unplugged it all. I have no idea what caused it, there should not have been any noise, everything was set correctly. A few hours later, I plugged the soundcard directly into the amplifier and tested it out. The tweeters were at a significantly lower volume than before, and things sounded off. This was beyond the impedance mismatch between the output of the card and the input on the amp.

The adcom shuts off if it receives a load below about 3 ohms, and has fuses for each channel, however it is older and I cannot confirm if that works! I have never had the issue before or sense, the marantz has never acted up like that and neither has the soundcard. The adcom has been used a bunch and had never done that.

Now, I notice that even with no music playing, there is a slight bit of noise coming out of the tweeters, I guess that means they are blown. The mids sound good though, the pots turn em up loud and there doesn't seem to be any noise.

The woofers sometimes sound good, but I can't even tell anymore, I just don't know.

Hope that provides something. Thanks.

Hi -

The GFA-2 has clipping protection which will shut it down immediatley if it approaches anything close to DC on the output terminals. It should have shut down instantly and then reset after 5 seconds or so. If this is not what the GFA-2 did, there may be a problem with it and I would not recommend hooking your speakers up to it until you can diagnose what happened. You might try disconnecting the Adcom from the Marantz, re-install the pre out/main in jumpers on the 2270 and connect the speakers to the 2270's speaker terminals for now. Power it up but be ready to shut it down FAST if anything seems out of character. I would suggest using a reliable line level source for the input, such as a known good cd player. Sometimes sound cards do funny things. Also check the cables leading to the GFA-2. If they go bad the amp will put out full power uncontrolable hum or static, and at 100 watts rms that's freakin' loud!

Were the 3A's pots working correctly before this happened? Also what's the condition of the surrounds (especially now)? You are probably going to have to remove the grills to examine them closely, but if the surrounds blew it's not the end of the world. It takes quite a lot to ruin those woofers electrically, they are pretty tough.

Let us know what you find!

Matt

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Hi -

The GFA-2 has clipping protection which will shut it down immediatley if it approaches anything close to DC on the output terminals. It should have shut down instantly and then reset after 5 seconds or so. If this is not what the GFA-2 did, there may be a problem with it and I would not recommend hooking your speakers up to it until you can diagnose what happened. You might try disconnecting the Adcom from the Marantz, re-install the pre out/main in jumpers on the 2270 and connect the speakers to the 2270's speaker terminals for now. Power it up but be ready to shut it down FAST if anything seems out of character. I would suggest using a reliable line level source for the input, such as a known good cd player. Sometimes sound cards do funny things. Also check the cables leading to the GFA-2. If they go bad the amp will put out full power uncontrolable hum or static, and at 100 watts rms that's freakin' loud!

Were the 3A's pots working correctly before this happened? Also what's the condition of the surrounds (especially now)? You are probably going to have to remove the grills to examine them closely, but if the surrounds blew it's not the end of the world. It takes quite a lot to ruin those woofers electrically, they are pretty tough.

Let us know what you find!

Matt

Hey Matt,

Thats what I thought- the adcom should have shut down. I have used it since the incident, going directly from my sound card (incidentally a daw box, it doesn't do funny things so I know its a good unit), and it has worked fine... so who knows.

The cable issue is interesting, I have not used the same cables I had used during the incident, though if that were the problem wouldn't teh adcom have still shut down with such signal?

The 3a was working flawlessly, I just had the surrounds replaced and was about a week into the enjoy phase, where I knew everything else was good. Now I'm back to square one, great. The tweeter controls and mid controls were working before, though a little spotty at the far end, but it was good enough I know the pots aren't perfect, now the mids still work great on both units though the tweeters are putting out noise where there should be (no sound going to it, and a bit of noise, not a lot but I never noticed it before), and the highs seem not as loud or clear as before.

As I said, I ran sound checks and all frequencies are apparently beign produced (Whether they are the real frequencies, I have my doubts... 20k is really audible for 20k).

Anyway, there are no physical signs of trauma on either speaker, both surrounds are good since they were just replaced, I haven't opened it up to look at anything else so beyond that I can't say.

Thanks for helping me out, this was a real nightmare.

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Update guys. I started using the 2270 amp section with one of the speakers, just to see if the static was gone, and it seems to have disappeared. I still think the his are a bit quiter than before, but that static is gone and it sounds ok. What do you guys think? how can I look into this further? Since the tweeters are making sound, they are not totally dead, could the crossover inside be messed up? Could that surge have fried the innards which is causing this static when the highs go?

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Guest matty g
Update guys. I started using the 2270 amp section with one of the speakers, just to see if the static was gone, and it seems to have disappeared. I still think the his are a bit quiter than before, but that static is gone and it sounds ok. What do you guys think? how can I look into this further? Since the tweeters are making sound, they are not totally dead, could the crossover inside be messed up? Could that surge have fried the innards which is causing this static when the highs go?

Hi -

If you are lucky, just the crossover caps need to be replaced and the pots cleaned and coated with anti-corrosion compound. Ideally this should have been done when the woofers were out of the cabinets for re-edging. The caps in there are very old and are likely out of spec, and of course we all know how troublesome the pots can be. Unfortunately the tweeters in those systems are not nearly as robust as the woofers, and the best insurance against damage to them would be to re-cap. It is quite possible that the surge from whatever happened may have damaged the already challenged caps, and it's probably best to stop using them until everything is straightened out. I would suggest removing the woofers and going through the trouble of re-capping and cleaning the pots, then see where you stand. It's a little bit of work, but those speakers are well worth it.

Matt

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  • 2 weeks later...

UPDATE

Hey guys, thought I would update things. I am currently listening to the speakers on the same setup as before, with some problems fixed. The source of the problem was the poweramp rca/phono inputs that were not always making ground contact. I have fixed that. I also tuned it up, the bass is now AWESOME and TIGHT. So the tweeter issue seems to be weird. I originally thought it was too quiet and distorted, but after extended listening it sounds fine. The volume is still like 2dB or 3dB off from what I thought it was, but listening to real instruments on it sound perfect, adjusting the brightness makes it sound less realistic, so maybe what I am hearing with these is how they are supposed to be, the +2 or +3 was what I am used to on other *bright* speakers/headphones. Pretty big relief here, those tweeters would have been a nightmare. I still need to do the caps, but I really don't feel like doing them right now. Can I keep listening for a while and eventually replace them?

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Of course you can. You shouldn't, but you can. Think of it like driving on a tire you know really, really needs some air. You might not run it off the rim, but I wouldn't be taking any sharp curves too quickly or pushing it too hard.

Bret

<_< Maybe I have runflat caps!

Where, what, and how much for the replacements? Additionally, is there a place that would sell replacement foam sealer things for the woofers? I saw the prices for some of the kits, and they are WAAAAY too much for me. I would think replacement parts would be dirt cheap, the pots or whatever device used, more. Ideas? Thanks.

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