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Author Topic: Blown Subwoofers and Looking for Replacement  (Read 9755 times)

Rob Spence

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Re: Blown Subwoofers and Looking for Replacement
« Reply #10 on: April 03, 2016, 12:05:04 am »

Watts is NOT the answer!!!!!!!!!!!!!

Output is what you are looking for.

Sometimes a speaker with a lower wattage rating can actually be LOUDER.

If you blew up the current drivers, it means that you don't have enough speakers for the job you are trying to do.

You can either turn the levels down or set some limiters to help protect them.

Or get more of the SAME speaker.  It is not generally a good idea to mix different sub models.

Or, do you have a proper high pass and cross over for the subs? Sending too much signal at frequencies lower than the sub can deal with can hurt them.



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Scott Holtzman

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Re: Blown Subwoofers and Looking for Replacement
« Reply #11 on: April 03, 2016, 12:17:32 am »

Watts is NOT the answer!!!!!!!!!!!!!

Output is what you are looking for.

Sometimes a speaker with a lower wattage rating can actually be LOUDER.

If you blew up the current drivers, it means that you don't have enough speakers for the job you are trying to do.

You can either turn the levels down or set some limiters to help protect them.

Or get more of the SAME speaker.  It is not generally a good idea to mix different sub models.

It's sexier to advertise watts than efficiency even though it takes you to the same place.  The marketing folks have conditioned the populace to focus on one number specs.

As you say "it depends" 

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Luke Geis

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Re: Blown Subwoofers and Looking for Replacement
« Reply #12 on: April 03, 2016, 06:06:35 pm »

I would say that the subs were very well powered and appropriately so. They were simply driven to fail. This is a user error, not a component or equipment issue. Red lights are bad MMMM K.......

It sounds like they may have failed while under your ( the OP ) watch? Were you running sound at the time they cooked? If so what did it sound like before they went? There is usually pretty obvious signs of distortion before the subs burn up. Other tell tale signs include a loss in volume over time and of course blinking red lights. Interestingly enough I would say the worst thing you could do is simply unplug the speaker once you realize it is starting to burn. The movement of the coil causes air to move around it. Reducing volume before it quits may help save it? The lower volume will keep the coils from getting any hotter and the movement of air will actually help cool them down.

What also doesn't help is the loss of one sub from the week before. So now you were asking the single, lone sub to do the work of two...... Not going to happen. It doesn't get better, it only gets worse. Part of being a sound engineer is playing by the rules and incidentally knowing what those rules are. Break them and you break expensive things.

I would buy either the direct replacement speaker or one as close in spec to the original as you can. The speaker you blew was of pretty good spec though. The two of those speakers placed next to each other should provide plenty of output for church service uses. They are rated at 135db peak, which for a 15" sub is really good. Realistically you won't get close to that, but I doubt you would need to get much beyond 120db at 1m in either case for a church service? There won't be a cheap replacement that meets the same spec and at the same size. There is nothing wrong with what you have, you simply are not using it correctly. It must be deployed correctly and used correctly. Not knowing any other information it is hard to say. Crossover points, subs on an aux, the overall level of the PA at the time it went as well as the venue size and desired SPL may help us determine more. That info can give us clues about pitfalls and system design constraints.
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Andri Irawan

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Re: Blown Subwoofers and Looking for Replacement
« Reply #13 on: April 06, 2016, 02:39:03 am »

Thank you everyone for your replies. I have to admit there are a lot to learn.

We are going to consult a professional service but it will take sometimes. For a small church, the process will take longer time.

Meanwhile, we are only running the two tops without any subs. It's barely sufficient for 30 x 60 ft room and I have to be careful not to clip them.

There are two pairs of RCF Evox 5 available for rent in the venue for rent and I have tested them. They are very loud but I found them to be too harsh after using outline for so long.

Due to busy schedule (I am pretty much running the sound system alone), I did not check whether the T Five amp was set properly or not. Anyway, we're only using the other amp (Outline T-44) for the tops and monitors.

I also found out that there is a dbx driverack 260 but currently not being used. We could have used this as xover? The subs were obviously on aux send but I dont understand what could be the impact or contribution to the failing.

Yes, I was the one watching over when the subs were cooked.  There was distortion and from the ipad I saw prolonged red lights on L&R channel but not on the Sub channel. But I did increase the sub volume a bit. After about 5 minutes later, the 'cooking' happened. :(

Honestly I still dont understand what happened. All I know is I made it too loud.

Thanks,


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« Last Edit: April 06, 2016, 07:29:41 am by Andri Irawan »
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Ivan Beaver

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Re: Blown Subwoofers and Looking for Replacement
« Reply #14 on: April 06, 2016, 07:54:45 am »

Thank you everyone for your replies. I have to admit there are a lot to learn.

We are going to consult a professional service but it will take sometimes. For a small church, the process will take longer time.

Meanwhile, we are only running the two tops without any subs. It's barely sufficient for 30 x 60 ft room and I have to be careful not to clip them.

There are two pairs of RCF Evox 5 available for rent in the venue for rent and I have tested them. They are very loud but I found them to be too harsh after using outline for so long.

Due to busy schedule (I am pretty much running the sound system alone), I did not check whether the T Five amp was set properly or not. Anyway, we're only using the other amp (Outline T-44) for the tops and monitors.

I also found out that there is a dbx driverack 260 but currently not being used. We could have used this as xover? The subs were obviously on aux send but I dont understand what could be the impact or contribution to the failing.

Yes, I was the one watching over when the subs were cooked.  There was distortion and from the ipad I saw prolonged red lights on L&R channel but not on the Sub channel. But I did increase the sub volume a bit. After about 5 minutes later, the 'cooking' happened. :(

Honestly I still dont understand what happened. All I know is I made it too loud.

Thanks,


Sent from my SM-G925I using Tapatalk
We all learn from our mistakes.  I have made PLENTY.

I have no idea how many hundreds of loudspeakers I have blown up.  That is why I got into reconing-to save myself money  :)

Ask questions, learn-pass on that knowledge so maybe somebody else does not have to go through the learning curve so much.

That is what I believe in.
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Don Sullivan

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Re: Blown Subwoofers and Looking for Replacement
« Reply #15 on: May 19, 2016, 09:39:09 pm »

If you have a drive rack -- I would use it. Don't bother with driving your subs from an Aux. Use HPF on inputs with no little low frequency content. Replace your drivers with exact duplicates. Here is how you will keep from blowing your speakers. Either with your drive rack or your amps you will use a zero attack limiter on the output to your sub amp. The key is to limit your output to the RMS rating of the speaker, not the peak. You have to measure the amp output with no load attached, and measure the voltage across the amp terminals while driving the amp with your mixer and crossover.
Get an AC voltmeter or DMM set to AC volts. attach the leads to the speaker terminals on your sub amp. Shut of your top amp. Set a 60 hz oscillator to come from your mixer -- raise your mixer master output and oscillator output so your mixer is at 0 VU or just above. This is your reference output level. Set your sub amp volume controls all the way up. You will bring your limiter threshold down in the Drive Rack (or amp) until the voltage coming out of your amp is at the right voltage. How do we know what that voltage should be? Take the RMS rating of your speaker / driver ( in your case AES), multiply it by the resistance of the driver, and take the square root. Since your subs are rated at 350 Watts and are 8 ohm, 350* 8 = 2800, sqrt(2800) = 52 volts AC. I would round down to 50 VAC. Do NOT make the mistake of bridging your sub amp. that merely doubles your output voltage and increases your risk of blown drivers. If you really need to get louder, get more subs.
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Jean-Pierre Coetzee

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Re: Blown Subwoofers and Looking for Replacement
« Reply #16 on: May 20, 2016, 05:59:03 am »

If you have a drive rack -- I would use it. Don't bother with driving your subs from an Aux. Use HPF on inputs with no little low frequency content. Replace your drivers with exact duplicates. Here is how you will keep from blowing your speakers.

Either with your drive rack or your amps you will use a zero attack limiter on the output to your sub amp. The key is to limit your output to the RMS rating of the speaker, not the peak. You have to measure the amp output with no load attached, and measure the voltage across the amp terminals while driving the amp with your mixer and crossover.

Get an AC voltmeter or DMM set to AC volts. attach the leads to the speaker terminals on your sub amp. Shut of your top amp. Set a 60 hz oscillator to come from your mixer -- raise your mixer master output and oscillator output so your mixer is at 0 VU or just above. This is your reference output level. Set your sub amp volume controls all the way up. You will bring your limiter threshold down in the Drive Rack (or amp) until the voltage coming out of your amp is at the right voltage. How do we know what that voltage should be? Take the RMS rating of your speaker / driver ( in your case AES), multiply it by the resistance of the driver, and take the square root. Since your subs are rated at 350 Watts and are 8 ohm, 350* 8 = 2800, sqrt(2800) = 52 volts AC. I would round down to 50 VAC. Do NOT make the mistake of bridging your sub amp. that merely doubles your output voltage and increases your risk of blown drivers. If you really need to get louder, get more subs.

I don't know if I agree with this methodology. There could be significant current and voltage across those terminals and with no load you are putting the voltmeter in series instead of in parallel as a voltmeter should be used. You should at the very least use a dummy load. It's not that hard to work out all the needed number mathematically if the specs are available for all the related information regardless with a lot less risk of severe bodily harm.

The fact that you burn the drivers seems to me more like sending too much HF content to the driver. This could be from excessive limiting(or not enough power being sent, using the peak rating of a speaker to match the amplifier is fine as long as it's properly limited and not run at max all the time, there is more danger in running the speaker with a lower rated amplifier), or simply an incorrect crossover frequency.

I agree with everyone here in that you should find out why those burnt up rather than replace immediately.

A few questions:

1. What is the crossover frequency to the subs?
2. Why did you not turn down the system when you saw red lights?
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Rob Spence

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Re: Blown Subwoofers and Looking for Replacement
« Reply #17 on: May 20, 2016, 09:01:39 am »

I don't know if I agree with this methodology. There could be significant current and voltage across those terminals and with no load you are putting the voltmeter in series instead of in parallel as a voltmeter should be used. You should at the very least use a dummy load. It's not that hard to work out all the needed number mathematically if the specs are available for all the related information regardless with a lot less risk of severe bodily harm.

The fact that you burn the drivers seems to me more like sending too much HF content to the driver. This could be from excessive limiting(or not enough power being sent, using the peak rating of a speaker to match the amplifier is fine as long as it's properly limited and not run at max all the time, there is more danger in running the speaker with a lower rated amplifier), or simply an incorrect crossover frequency.

I agree with everyone here in that you should find out why those burnt up rather than replace immediately.

A few questions:

1. What is the crossover frequency to the subs?
2. Why did you not turn down the system when you saw red lights?

To clarify the above on amplifier size...

Low power into a speaker does not damage them. However, having an undersized amp can lead to running it into clip which raises the average power into the speaker which may overheat it and cause it to fail.

And, what is the high pass on the subs vs manufacturers recommendations?

Running frequencies into a speaker below the manufactures spec can cause over excursion thereby damaging the driver.

As was stated previously, find out the failure mode in order to determine what to do to avoid further failures.




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Ivan Beaver

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Re: Blown Subwoofers and Looking for Replacement
« Reply #18 on: May 21, 2016, 04:20:43 pm »

I don't know if I agree with this methodology. There could be significant current and voltage across those terminals and with no load you are putting the voltmeter in series instead of in parallel as a voltmeter should be used. You should at the very least use a dummy load.
Sorry, but I disagree.

The method is totally valid.

Adding a dummy load will (should not anyway), not do anything to the voltage coming out of the amp. 

A least a solid state amp-as most PA amps are.

HOWEVER-if you are trying to set the limit voltage ABOVE the capability of the amp into a particular load, then that CAN be an issue.

You should use the LOWER of either the speaker power voltage OR the amps capability of voltage swing in to the impedance load that is hooked to it.
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Jean-Pierre Coetzee

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Re: Blown Subwoofers and Looking for Replacement
« Reply #19 on: May 22, 2016, 05:39:35 am »

Sorry, but I disagree.

The method is totally valid.

Adding a dummy load will (should not anyway), not do anything to the voltage coming out of the amp. 

A least a solid state amp-as most PA amps are.

HOWEVER-if you are trying to set the limit voltage ABOVE the capability of the amp into a particular load, then that CAN be an issue.

You should use the LOWER of either the speaker power voltage OR the amps capability of voltage swing in to the impedance load that is hooked to it.

I'm thinking more in terms of safety rather than whether you will get the correct end result. You are still dealing with power here whether it is at 50/60hz or anything higher, take the correct precautions.
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Re: Blown Subwoofers and Looking for Replacement
« Reply #19 on: May 22, 2016, 05:39:35 am »


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