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Author Topic: Blown Subwoofers and Looking for Replacement  (Read 9772 times)

Ivan Beaver

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Re: Blown Subwoofers and Looking for Replacement
« Reply #20 on: May 22, 2016, 12:28:36 pm »

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.
How would hooking up a dummy load make it any "safer"?
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MikeHarris

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Re: Blown Subwoofers and Looking for Replacement
« Reply #21 on: May 22, 2016, 05:36:50 pm »

The CDD and CSX series don't have pole mounts as they are install speakers. I believe the CDD8 to be too small to cover what you have..at least 10 or 12 might be more appropriate.
The S15+ does have a pole mount socket but I don't know if the CDD12 yoke mount will fit a speaker pole.
The new CDD Live is powered.
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Lee Buckalew

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Re: Blown Subwoofers and Looking for Replacement
« Reply #22 on: May 22, 2016, 05:46:52 pm »

The CDD and CSX series don't have pole mounts as they are install speakers. I believe the CDD8 to be too small to cover what you have..at least 10 or 12 might be more appropriate.
The S15+ does have a pole mount socket but I don't know if the CDD12 yoke mount will fit a speaker pole.
The new CDD Live is powered.

The CDD LIVE series have pole mounts.  The CSX LIVE-118 has a threaded fitting for a pole mount.  The CSX LIVE-218 does not have a fitting.
Standard CDD and CSX are for install and do not have handles or pole mount capability.

Lee
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TJ (Tom) Cornish

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Re: Blown Subwoofers and Looking for Replacement
« Reply #23 on: May 23, 2016, 08:42:20 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.
I think you are confusing voltage and current measurement.  For current measurement the meter is placed in parallel with a shunt resistor (the shunt resistor is in series with the main load you are measuring the current of).

For voltage measurement putting the leads of the meter directly across the voltage to be measured is the correct procedure.  A "dummy load" not only makes your readings incorrect (subject to the value of your load), it could actually increase measuring danger as an under-sized dummy load could overheat and start a fire.

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Jean-Pierre Coetzee

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Re: Blown Subwoofers and Looking for Replacement
« Reply #24 on: May 23, 2016, 12:46:01 pm »

I think you are confusing voltage and current measurement.  For current measurement the meter is placed in parallel with a shunt resistor (the shunt resistor is in series with the main load you are measuring the current of).

For voltage measurement putting the leads of the meter directly across the voltage to be measured is the correct procedure.  A "dummy load" not only makes your readings incorrect (subject to the value of your load), it could actually increase measuring danger as an under-sized dummy load could overheat and start a fire.

My worries were that you are completing the circuit with your mm therefore your mm would be the dummy load which may not be rated to handle the current regardless.

Also could you explain to me in a pm measuring current in parallel since I thought that according to kirchovs law current would be split between the two circuits and thus would make your measurement incorrect.
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Ivan Beaver

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Re: Blown Subwoofers and Looking for Replacement
« Reply #25 on: May 23, 2016, 01:20:54 pm »

My worries were that you are completing the circuit with your mm therefore your mm would be the dummy load which may not be rated to handle the current regardless.

Also could you explain to me in a pm measuring current in parallel since I thought that according to kirchovs law current would be split between the two circuits and thus would make your measurement incorrect.
When measuring voltage, the MM is a VERY HIGH impedance.

Yes current will flow, but it a VERY MINIMAL amount.

Not enough to provide any sort of load.

Back in the 'ol days, we have things like the Simpson 260.

A great utility meter.  It was fine for most things, but could load down a high impedance circuit.

For those we used a VTVM (Vacuum tube volt meter).

It had a high input impedance.

All modern digital meters have a high impedance.

But even the old Simpson 260 would not load down the output of an amp.  Because the amps output impedance is VERY LOW as compared to the analog volt meter.
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TJ (Tom) Cornish

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Re: Blown Subwoofers and Looking for Replacement
« Reply #26 on: May 23, 2016, 01:52:23 pm »

My worries were that you are completing the circuit with your mm therefore your mm would be the dummy load which may not be rated to handle the current regardless.

Also could you explain to me in a pm measuring current in parallel since I thought that according to kirchovs law current would be split between the two circuits and thus would make your measurement incorrect.
Expanding on what Ivan said, yes - when doing a voltage measurement your meter does indeed complete the circuit (which is how you can get a reading), however the current flow is VERY small due to the extremely high impedance of the meter - usually greater than 10,000,000Ω.  Doing some math, the current flowing through the meter when you measure a 240v mains socket is 240v/10,000,000Ω, which equals 0.000024A.  Multimeters can directly measure voltage up to their full rated potential - i.e. 1000v or whatever - directly without risk of damage.  Plugging in a dummy load will give you the wrong answer as you are no longer doing a no-load measurement (assuming that's what you were trying to do) and may be dangerous.  At least, it's a waste of time.

RE current measurement:

I need to clarify the difference between using your multi-meter set to current mode and using an external shunt.  Many multi-meters have an internal shunt resistor - i.e. they can measure up to 10A internally if you use the current jacks on the meter.  If you are doing this kind of measurement and are sure that you will not exceed the current that the meter can handle, then no additional wiring or calculation is needed - set your meter to current mode, put the meter in your circuit in series with the load, and read directly.

The general case of current measurement - including what your meter does internally and automatically - is actually a voltage measurement across a shunt resistor of a known value.  For example, you insert a 1Ω high-power capacity shunt resistor in series with your load and wire your meter set to voltage across this shunt resistor.  Ohm's law tells us that current = voltage/resistance and with a nice round number of 1Ω for our shunt resistor, the formula becomes current = voltage (that the meter reads across the shunt resistor)/1, so if 5 amps are flowing through the circuit under test, your voltmeter will display a reading of 5 volts.

Yes, some current does go through the multi-meter, but you need to consider the magnitude of the current through the shunt vs. the current through the meter.  The meter is 10,000,000Ω and the current shunt is 1Ω, which means only 1/10,000,000 of the current will be lost to the multimeter, and 9,999,999/10,000,000 will pass through the shunt resistor.  You'll have much more error in the tolerance of the shunt resistor and its connections than the measurement error due to the meter.
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Jean-Pierre Coetzee

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Re: Blown Subwoofers and Looking for Replacement
« Reply #27 on: May 23, 2016, 02:24:58 pm »

Expanding on what Ivan said, yes - when doing a voltage measurement your meter does indeed complete the circuit (which is how you can get a reading), however the current flow is VERY small due to the extremely high impedance of the meter - usually greater than 10,000,000Ω.  Doing some math, the current flowing through the meter when you measure a 240v mains socket is 240v/10,000,000Ω, which equals 0.000024A.  Multimeters can directly measure voltage up to their full rated potential - i.e. 1000v or whatever - directly without risk of damage.  Plugging in a dummy load will give you the wrong answer as you are no longer doing a no-load measurement (assuming that's what you were trying to do) and may be dangerous.  At least, it's a waste of time.

RE current measurement:

I need to clarify the difference between using your multi-meter set to current mode and using an external shunt.  Many multi-meters have an internal shunt resistor - i.e. they can measure up to 10A internally if you use the current jacks on the meter.  If you are doing this kind of measurement and are sure that you will not exceed the current that the meter can handle, then no additional wiring or calculation is needed - set your meter to current mode, put the meter in your circuit in series with the load, and read directly.

The general case of current measurement - including what your meter does internally and automatically - is actually a voltage measurement across a shunt resistor of a known value.  For example, you insert a 1Ω high-power capacity shunt resistor in series with your load and wire your meter set to voltage across this shunt resistor.  Ohm's law tells us that current = voltage/resistance and with a nice round number of 1Ω for our shunt resistor, the formula becomes current = voltage (that the meter reads across the shunt resistor)/1, so if 5 amps are flowing through the circuit under test, your voltmeter will display a reading of 5 volts.

Yes, some current does go through the multi-meter, but you need to consider the magnitude of the current through the shunt vs. the current through the meter.  The meter is 10,000,000Ω and the current shunt is 1Ω, which means only 1/10,000,000 of the current will be lost to the multimeter, and 9,999,999/10,000,000 will pass through the shunt resistor.  You'll have much more error in the tolerance of the shunt resistor and its connections than the measurement error due to the meter.

Thanks Tom & Ivan for clearing that up, as I said was not sure but now I see I would be safe.

Still nothing from op regarding the crossover frequency though...
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Andri Irawan

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Re: Blown Subwoofers and Looking for Replacement
« Reply #28 on: May 23, 2016, 10:39:55 pm »

Hi all,

Thank you for all your replies.

Here are some data I gathered:
1. The amp was set to max output voltage of 165.  This should have been set to sqrt(350 W*8 Ohms) = around 52V, according to what Don suggested.
2. X-Over Freq is 150Hz
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Jean-Pierre Coetzee

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Re: Blown Subwoofers and Looking for Replacement
« Reply #29 on: May 24, 2016, 03:44:06 am »

Hi all,

Thank you for all your replies.

Here are some data I gathered:
1. The amp was set to max output voltage of 165.  This should have been set to sqrt(350 W*8 Ohms) = around 52V, according to what Don suggested.
2. X-Over Freq is 150Hz

I still don't agree with limiting to long term ratings, limit to peak, you pretty much wasting your money if you limit to program power.

Xover seems high to me at 150hz but check the manufacturer information on the subs to make sure

EDIT:

The SI2 max output level is 21.5dBu while the outline T5 needs 25dBu to output max power to the speakers from what I can pickup so there is no way for you to ever have sent the amp into clipping but you could have exceeded the long term power rating of the system by running it close to max which would have caused the voice coil to burn.

150Hz might be a bit high but its within the manufacturers recommendation so doubt that was causing any issues setup wise, likewise the amp is matched correctly to the subs so there is no reason to change anything there.

IMHO there isn't enough rig for the gig and that is a whole other matter. Limiting to program power will prevent your from destroying the drivers in the same way in the future but if there wasn't enough previously there isn't going to be near enough after you limit it as such.
« Last Edit: May 24, 2016, 04:38:28 am by Jean-Pierre Coetzee »
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Re: Blown Subwoofers and Looking for Replacement
« Reply #29 on: May 24, 2016, 03:44:06 am »


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