Jbl vrx burnout.

[nandan21]

I had put 8 vrx 932la- on crown xti 6002 (Brand New). I did an hour
and half of sound check and was done. During the show 2 of the 4 vrx,
on separate channels of two separate amplifiers, coil g ot burned.
Rest are fine. What could be the reason?

[Rupert]

One thing and one thing only burns out coils: overpowering. Did you
check and see if the amps where clipping throughout the show? Were
proper limiters set to prevent clipping? As to why only some drivers
burned out and not others, it could be the others were getting close
as well. It's rare all the speakers would have fried at the same time
though it can happen.

You say you were running two amps. So that's 2 VRXs per channel,
correct? The 6002 puts out 2100 watts max into 4 ohms (2 speakers). So
each box would get ~1050 watts with the amp running full out (which
they only do for sort periods of time normally). rms rating of the
boxes are 800 watts each. If you were clipping the amps frequently it
would possible to exceed 800 watts and toast voice coils. Due to the
damage I can guess that some heavy clipping was involved at some
point. Even heavy compressed music with an amp that produces a couple
hundred watts over the 800 rms rating won't blow drivers if it's not
clipped. There's enough crest factor involved so the rms voltage is
well under what would overheat things. That can change fast with
clipping, especially heavy clipping. Light occasional clipping is
usually not an issue.

So to prevent problems in the future, don't clip your amps. If you
increased your amp size to match the program power rating, you could
squeeze almost 2 more dB of headroom out of your rig before clip. But
you'd be in the same boat if you clipped your amps and you'd blow your
drivers even quicker. The XTi series amps have real time monitoring
using a laptop and the Sound Architect software from JBL. I suggest
you run the software and monitor the amps when you're running the
show. You might look into upgrading your amps to the I-Tech HD series
which have rock solid 3 stage limiting that will will give you rms,
voltage, and clip limiting. With the limiters properly setup, you
could hammer the amps as hard as hell and not blow anything. In fact
you can use really big amps rated at the peak power rating for those
boxes (3200 watts) to get maximum headroom and still not blow them
with the limiting properly setup. JBL already has presets to load into
the amp's processor so you don't' have mess with the settings to give
you out of the box maximum performance. But it comes at a premium.

In any case, setting up the limiters on your current XTi amps should
afford decent protection if settings are correct. I believe there are
presets for the XTi processor as well for the VRX. Not sure if it
includes limiters settings but it make sense that they would.

Rupert

[Phil Allison]

"nandan21"

>
>I had put 8 vrx 932la- on crown xti 6002 (Brand New). I did an hour
> and half of sound check and was done. During the show 2 of the 4 vrx,
> on separate channels of two separate amplifiers, coil g ot burned.

** And you are surprised by this ?

> Rest are fine. What could be the reason?

** The reason for what ?

Why some of the woofers managed to survive ?

They will not all fail simultaneously you know.

Just keep going and they will eventually all burn out.

The Xti 6002 is more than capable of it.




... Phil

[Phil Allison]

"Rupert"

One thing and one thing only burns out coils: overpowering.

** Correct - assuming the voice coil has not suffered prior mechanical
damage.

You say you were running two amps. So that's 2 VRXs per channel,
correct? The 6002 puts out 2100 watts max into 4 ohms (2 speakers). So
each box would get ~1050 watts with the amp running full out (which
they only do for sort periods of time normally).

** The rated power of the amp into a resistive load is hardly relevant.

The actual REAL power handling capacity of the 2262H woofer is

- but JBL will never tell you that one.

If you were clipping the amps frequently it
would possible to exceed 800 watts and toast voice coils.

** No clipping is needed and the Crown amps have anti-clipping limiters.

The Xti 6002 simply has far more REAL power available than the woofer can
handle - particularly if that power is delivered in the band between 150Hz
and 600Hz and / or near the port tuning frequency.

The IEC 800 watt rms rating is pure speaker maker's fantasy.



... Phil

[Checkmate]

Warning! Always wear ANSI approved safety goggles when reading posts by
Checkmate or his many talented socks. Oh yeah... I should also mention
that Phil Allison said this shit:
~
~ "Rupert"
~
~ One thing and one thing only burns out coils: overpowering.
~
~ ** Correct - assuming the voice coil has not suffered prior mechanical
~ damage.
~
~
~ You say you were running two amps. So that's 2 VRXs per channel,
~ correct? The 6002 puts out 2100 watts max into 4 ohms (2 speakers). So
~ each box would get ~1050 watts with the amp running full out (which
~ they only do for sort periods of time normally).
~
~
~ ** The rated power of the amp into a resistive load is hardly relevant.
~
~ The actual REAL power handling capacity of the 2262H woofer is
~
~ - but JBL will never tell you that one.
~
~
~ If you were clipping the amps frequently it
~ would possible to exceed 800 watts and toast voice coils.

Maybe he needs his toaster fixed, Phil. Can you help a brutha out?




~ ** No clipping is needed and the Crown amps have anti-clipping limiters.
~
~ The Xti 6002 simply has far more REAL power available than the woofer can
~ handle - particularly if that power is delivered in the band between 150Hz
~ and 600Hz and / or near the port tuning frequency.
~
~ The IEC 800 watt rms rating is pure speaker maker's fantasy.
~
~
~
~ ... Phil



--
Checkmate
Copyright © 2011
all rights reserved

[Denny Strauser]

True ... but some things like ultra-high frequency oscillation might
heat up voice coils. DC might do the same.

- Denny

[Phil Allison]

"Denny Strauser"

> True ... but some things like ultra-high frequency oscillation might heat
> up voice coils.

** Not true at all.

HF oscillations damage AMPLIFIERS - but not woofers.

BTW:

I am currently preparing an article called:

"Speaker Failure: The Truth "

4,300 words, high res pics and some tech data and link

- but no mind numbing math.

Rod at ESP is going to post it on his site, soon.

http://sound.westhost.com/



... Phil

[Bo...@somewhere.com]

Can't wait to read it. Hopefully I'll get some tips on keeping my spks alive for
a long time!

[Phil Allison]

<Bo...@somewhere.com>
"Phil Allison"

>
>>I am currently preparing an article called:
>>
>>"Speaker Failure: The Truth "
>>
>>4,300 words, high res pics and some tech data and link
>>
>>- but no mind numbing math.
>>
>>Rod at ESP is going to post it on his site, soon.
>>
>>http://sound.westhost.com/
>>
>

> Can't wait to read it.

** The only thing still to do is set up a test rig using the AES " 50Hz to
500Hz " pink noise method.

I will try to borrow a JBL 2226H to do the honours.

> Hopefully I'll get some tips on keeping my spks alive for
> a long time!

** I can tell you them now:

1. No disco.

2. No clipping.

3. Ignore maker's published wattage ratings.



... Phil

[Rupert]

On Nov 11, 7:39 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
> <B...@somewhere.com>

I'm looking forward to the article as well. Item number 3 begs the
question: if you can't trusted the published specs for a given driver
or box, what's the best method of determining the right size amp for
the job short of doing your own destructive testing?

Rupert

[Phil Allison]

"Rupert".

I'm looking forward to the article as well. Item number 3 begs the
question: if you can't trusted the published specs for a given driver
or box, what's the best method of determining the right size amp for
the job short of doing your own destructive testing?

** I do some destructive testing in the article, but will not be burning up
a 2226 just for fun.

Far as your question goes, the article shows how published wattage figures
for woofers are inflated by AES and IEC tests, often by very large factors.

Far as advice goes, Cling Eastwood had the answer when he said:

" Do you feel lucky, punk ? "


... Phil

[nandan21]

As per my knowledge 2 VRX per channel of XTI 6002 is a good match,
without clipping. Also how bad is digital clipping on Driverack 260.

[nandan21]

I'm a bit experienced and make it a point not to clip amps. Only
problem that I could figure out is prior mechanical damage in a show
where I might not be present, other issue being unstable power,
because of a genset failure I was sharing line with stage lights.

[Phil Allison]

"nandan21"

>
>
> >I had put 8 vrx 932la- on crown xti 6002 (Brand New). I did an hour
> > and half of sound check and was done. During the show 2 of the 4 vrx,
> > on separate channels of two separate amplifiers, coil g ot burned.
>
> ** And you are surprised by this ?
>
> > Rest are fine. What could be the reason?
>
> ** The reason for what ?
>
> Why some of the woofers managed to survive ?
>
> They will not all fail simultaneously you know.
>
> Just keep going and they will eventually all burn out.
>
> The Xti 6002 is more than capable of it.
>

I'm a bit experienced and make it a point not to clip amps.

** But what sort of horrible noise were you giving them ?

No answer required, because you are clearly a know nothing idiot.




.... Phil

[Peter Larsen]

nandan21 wrote:

>> In any case, setting up the limiters on your current XTi amps should
>> afford decent protection if settings are correct. I believe there are
>> presets for the XTi processor as well for the VRX. Not sure if it
>> includes limiters settings but it make sense that they would.

>> Rupert

> As per my knowledge 2 VRX per channel of XTI 6002 is a good match,
> without clipping. Also how bad is digital clipping on Driverack 260.

Someone has not done is homework if digital clipping is possible, anyway, it
would result in distortion but probably not in bass loudspeaker damage.
Voiding the crest-factor asumption in the powerhandling specs invariably
will, no matter how it is done, limiting included. That I expect to be
addresssed in the presets, Rupert mention.

Kind regards

Peter Larsen

[nandan21]

Have you in your carrier got away without damaging any driver, or
always knew what caused it? Smart............