Speaker overload (tweeter) protection using bulbs (repost)

[Meat Plow]

On Sun, 16 Nov 2008 05:03:47 -0500, "George's Pro Sound Company"
<bmoas@yahoo.com>wrote:

"Meat Plow" <meat@petitmorte.net> wrote in message
news:2blg24.qbq.19.4@news.alt.net...
On Sun, 16 Nov 2008 04:25:13 +0000, Eeyore
rabbitsfriendsandrelations@hotmail.com>wrote:



Meat Plow wrote:

"George's Pro Sound Company"wrote:
"Meat Plow" <meat@petitmorte.net> wrote in message
Eeyore wrote:

This is a well established technique for preventing voice coils
burning
out under conditions of 'overdrive'.

There is a stage monitor I'm having problems with that uses this
method.

The HF sounds very distorted and almost cuts in and out.

I looked closely inside and found some damaged push-on terminals. Ah,
I
thought, probably a poor contact causing the probelm, replaced them,
checked driver DC resistances etc, reassembled thinking I'd probably
fixed it.

But no, the low level HF and distortion continued.

I'd checked the DC resistance of the protection bulb but later it
occurred to me that it might have 'very nearly' burnt out and have a
weak spot that wouldn't show up on a DVM but passing signal would
heat
it and cause this trouble. I'll be able to find out soon enough but I
wondered if anyone else had ever encountered this ?

In the meantime I brought the HF driver home to check it's not voice
coil rub.

Been using some Wharfedale stage gear for a year or so. The mains are
all protected by lamps. I've replaced two in a year but not
experienced a distorted HF. You'll find problems in the xover or
drive
I would assume rather than the lamp.

or maybe it's time to upgrade from that MI grade junk your using
George

Who, me?

From what I've heard they're well considered and in the IAG group now.
http://www.internationalaudiogroup.com/

The Chang brothers don't believe in messing about AIUI.
http://www.internationalaudiogroup.com/executive_summary.php

Graham



We've been using the Warfe pro-audio stuff for a year and have had few
problems. One 2500 watt power amp we used for our 18" subs got sent
back because it was too sensitive and would fault when pushed hard at
4 ohms. The replacement did not exhibit this behavior under the exact
conditions. I've replaced a couple lamp protectors elsewhere.

I wouldn't call Wharfedale junk. It's usable, sounds good and reliable
and a lot less expensive than other name brands.

I consider W home stereo grade gear, not suitable for Pro Live Sound, below
behringer

Glad to hear it. I don't suppose you're a musician who uses Wharfe
gear or repairs pro audio gear for a living, but rather just another
consumer or retailer who has an opinion.

As far as the Behringer gear goes I have no experience with it so
other than seeing a lot of negative comments about it from those who
do use or repair it i have no opinion.

 

[Eeyore]

"Dave Plowman (News)" wrote:

George's Pro Sound Company <bmoas@yahoo.com> wrote:
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
George's Pro Sound Company <bmoas@yahoo.com> wrote:
"Ron Johnson" <ron@lunevalleyaudio.com> wrote in message
Eeyore wrote:

This is a well established technique for preventing voice coils
burning out under conditions of 'overdrive'.

here is a novel thought
DON"T OVERDRIVE THEM
simple and effective

Easily said - but not so easy to do when setting up this sort of
equipment. Let alone when that equipment is being used by all sorts.

it's what I do the easiest way to overdrive a speaker is to use a amp
larger than the
speakers rateing

Doesn't stop the amp having greater than the HF driver's rating !

Strangely that's not always so.

The best solution would be a decent limiter on the amp input - but
these cost if it's not going to sound horrid when it operates. A bulb
is a very cheap solution to help protect the speakers.

No lamps in my meyers. setting up a system that both sounds good and
stays within the limits of the equipment used is NOT hard, it simply
requires one know what they are doing.

These days always having 'someone who knows what they're doing' is rare.
And even less likely with a small band starting out. So you need to make
equipment as idiot proof as possible.

a amp equal to the speaker rms
rateing will never burn out the speaker unless the amp is clipped hard
and long it will never exceed the excursion of the speaker unless
someone fires a gun a inch from a mic at foolish gains set your system
up properly and you have no need for these foolish lamps.

Either the amp cannot produce enough wally to damage the speakers or it
can - so the gunshot thing is rubbish. But no speaker is designed to
handle DC for long - which is what you can get from a grossly overloaded
amp. To be certain that DC couldn't wreck the speakers would require a
*much* smaller amp than would otherwise make sense. Or, of course, use an
amp which can't pass DC.

Or ensure the amp you have is fitted with DC 'crowbar' protection such as I
design in.. Or output relays but these can oxidise their contacts degrading the
sound, and if they don't have enough clearance will arc-over on a DC fault.

create cheap
MI gear that is used improperly and you need to limit the abuse idiots
can administer, to save on the warrentte costs I have never heard a
speaker with lamps(I've owned plenty) sound as good as a speaker with
out lamps

Correctly designed the lamp should have little effect on the sound as its
cold resistance will be very low. Only when it starts to 'protect' will
the resistance increase.

again no lamps in my meyers, I do have alimiter but it is set well
above any threshold I pass music at. why buy a 1000 watt amp then limit
it to 300 watts, why not just buy a 300 watt amp?

Why are you using a limiter at all, then?

I think you summed it up pretty well there Dave.

Graham

 

[Eeyore]

William Sommerwerck wrote:

amp
larger than the speaker[']s rateing [sic]

Actually, the easiest way to overdrive a speaker is to play it at a level
where it produces audible distortion. But as most listeners have no idea
what distortion sounds like...

Exceed X max (not difficult with ported cabs) and you can do a lot of damage
to the LF driver too.

Graham

 

[Eeyore]

George's Pro Sound Company wrote:

a amp "can" put out several times it's rated power for a instant, enough to
throw a cone. been there already

UTTER and complete rubbish. If you're referring to the difference between an rms
and peak voltage or power, that's already taken into account in the speaker's
rating. Yes, you can get a bit more out of an amp on toneburst but rarely much
over 1-2dB at the very most. Certainly not for long enough to do any damage.

You're straying into tech territory here George that you don't understand. Stick
to rigging and mixing.

Graham

 

[Eeyore]

George's Pro Sound Company wrote:

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message

the easiest way to overdrive a speaker is to use a[n] amp
larger than the speaker[']s rateing [sic]

Actually, the easiest way to overdrive a speaker is to play it at a level
where it produces audible distortion. But as most listeners have no idea
what distortion sounds like...

OTOH distortion does not destroy speakers, speakers are as happy to play
distortion as clean signal
only when you exceed the heat dissipating ability of the motor do you burn
out a speaker

Generally. But not exclusively by far.

Exceeding X max can trash an LF or HF driver without as much as even a
discoloured voice coil. And there are many easy ways to do it.

Graham

 

[Eeyore]

William Sommerwerck wrote:

in practice, audible distortion is a warning that you should
turn down the volume.

Couldn't agree more.

The distortion I was talking about was the sort that comes from pushing it
into its excursion limits.

(X max)

Precisely. I have a lovely pair of Altec diaphragms in my "rogue's gallery" that
demonstrates this perfectly. The voice coils meaure 100% OK and look OK.

Graham

 

[Eeyore]

George's Pro Sound Company wrote:

bottoming(or farting) a woofer is truely a horid sound

That's technically exceeding X max (Thiele and Small parameters). Easy to do
with ported cabs and no suitable high order HPF.

Mine (my client's) is 24dB/octave @ 35Hz.

Graham

 

[liquidator]

"Meat Plow" <meat@petitmorte.net> wrote in message
news:2bmjnj.v86.19.1@news.alt.net...

On Sun, 16 Nov 2008 05:03:47 -0500, "George's Pro Sound Company"
bmoas@yahoo.com>wrote:


"Meat Plow" <meat@petitmorte.net> wrote in message
news:2blg24.qbq.19.4@news.alt.net...
On Sun, 16 Nov 2008 04:25:13 +0000, Eeyore
rabbitsfriendsandrelations@hotmail.com>wrote:



Meat Plow wrote:

"George's Pro Sound Company"wrote:
"Meat Plow" <meat@petitmorte.net> wrote in message
Eeyore wrote:

This is a well established technique for preventing voice coils
burning
out under conditions of 'overdrive'.

There is a stage monitor I'm having problems with that uses this
method.

The HF sounds very distorted and almost cuts in and out.

I looked closely inside and found some damaged push-on terminals.
Ah,
I
thought, probably a poor contact causing the probelm, replaced
them,
checked driver DC resistances etc, reassembled thinking I'd
probably
fixed it.

But no, the low level HF and distortion continued.

I'd checked the DC resistance of the protection bulb but later it
occurred to me that it might have 'very nearly' burnt out and have
a
weak spot that wouldn't show up on a DVM but passing signal would
heat
it and cause this trouble. I'll be able to find out soon enough
but I
wondered if anyone else had ever encountered this ?

In the meantime I brought the HF driver home to check it's not
voice
coil rub.

Been using some Wharfedale stage gear for a year or so. The mains
are
all protected by lamps. I've replaced two in a year but not
experienced a distorted HF. You'll find problems in the xover or
drive
I would assume rather than the lamp.

or maybe it's time to upgrade from that MI grade junk your using
George

Who, me?

From what I've heard they're well considered and in the IAG group now.
http://www.internationalaudiogroup.com/

The Chang brothers don't believe in messing about AIUI.
http://www.internationalaudiogroup.com/executive_summary.php

Graham



We've been using the Warfe pro-audio stuff for a year and have had few
problems. One 2500 watt power amp we used for our 18" subs got sent
back because it was too sensitive and would fault when pushed hard at
4 ohms. The replacement did not exhibit this behavior under the exact
conditions. I've replaced a couple lamp protectors elsewhere.

I wouldn't call Wharfedale junk. It's usable, sounds good and reliable
and a lot less expensive than other name brands.

I consider W home stereo grade gear, not suitable for Pro Live Sound,
below
behringer


Glad to hear it. I don't suppose you're a musician who uses Wharfe
gear or repairs pro audio gear for a living, but rather just another
consumer or retailer who has an opinion.

As far as the Behringer gear goes I have no experience with it so
other than seeing a lot of negative comments about it from those who
do use or repair it i have no opinion.

Behringer is like any company...some usable for semi pro, some absolute
garbage.

Thee odd thing is most negative comments about Behringer do NOT come from
users as you say.

Almost all negative posts about Behringer are from users of other brands.

It's no worse than any other cheap stuff, better sometimes. I don't us it,
but plenty of weekend warrriors do.

If Behringer was a s bad as people try to say, they would be out of
business.

Conclusion- many aof the negative posts are bull.

I don't use Behringer, or Mackie, or any of that kinda stuff. But I am not
gonna insist everybody drive the same brand of car I do.

 

[Eeyore]

George's Pro Sound Company wrote:

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote

What gets you up so early on a Sunday? (I'm on the west coast,
and have been up since 2AM.)

went out had a couple of dogfish 90 minutes and that set me down
early(8pm) some days your just not tired at 4 am

As in...

http://www.dogfish.com/brewings/Seasonal_Beers/Punkin_Ale/3/index.htm

Same brewery but this IPA
http://www.dogfish.com/brewings/Year_Round_Beers/90_Minute_IPA/11/index.htm

Are you familiar with the origin of the name 'IPA' ?

Graham

 

[Eeyore]

Tony wrote:

I like to protect gear from whatever might come, so I like lamps and polyswiches. I would
be almost as happy with a frequency-selective limiter that could independently account for
the thermal and displacement limits of the tweeter, mid and woofer (with appropriately
different time constants - an even greater challenge), but the reality is that a lamp in
the tweeter circuit handles 80% of abuse, so it's cheap insurance.

That's how I see it too. We don't get many lamps blown but it does happen, even in the EV
QRx's (almost once a year on average).

But an interesting twist is that with the simple 2nd order HPFs I have been trying (with a
very high Fc, eg 8 kHz, to flatten CD horn response and match sensitivities), a lamp or
polyswitch in the INPUT to the crossover has the nice benefit of also seeing more MF, and
so potentially account for both thermal and displacement limitations. Admittedly the time
constants cannot be independent as would really be required, but it's still better than
having the lamp in the crossover output circuit, and a LOT safer for the amp, which
becomes UNLOADED when the protection operates, instead of shorted.

Indeed it should ALWAYS be on the input side. Which is how ours are arranged. It just
disconnects the HPF.

Graham

 

[Eeyore]

"Dave Plowman (News)" wrote:

liquidator <mikeh@mad.scientist.com> wrote:
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message

But no speaker is designed to handle DC for long - which is what you
can get from a grossly overloaded amp. To be certain that DC couldn't
wreck the speakers would require a *much* smaller amp than would
otherwise make sense. Or, of course, use an amp which can't pass DC.

Jeez...a little knowledge is a dangerous thing.

Suggest you try driving a DC coupled amp into heavy clipping and see the
results to speakers which can nominally handle its output.

That's why I use 'clip eliminator circuits'. Did my first 18 years ago in the
1200B. Used a transconductance amp in a feedback loop (inactive until clip
sensed so no effect on normal signal).

Graham

 

[Eeyore]

George's Pro Sound Company wrote:

put a 100% distored signal from a 1 watt amp into a 600 watt woofer and you
will not live long enough to see it burn out.

Uh ?

A 100% distorted signal would be a square wave of 2W rating. That's not going to
bother ANY 600W rated voice coil.

Graham

 

[Eeyore]

"Michael A. Terrell" wrote:

George's Pro Sound Company wrote:

this is the PRO LIVE SOUND newsgroup

No, it isn't. You are cross posting to these groups:

news:rec.audio.tech
news:alt.audio.pro.live-sound
news:sci.electronics.repair

More correctly I was, since the original question was relevant to all.

George should have trimmed the groups for pro-sound comments only.

Graham

 

[Eeyore]

"Michael A. Terrell" wrote:

George's Pro Sound Company wrote:

this is the PRO LIVE SOUND newsgroup

No, it isn't. You are cross posting to these groups:

news:rec.audio.tech
news:alt.audio.pro.live-sound
news:sci.electronics.repair

In practice, I think you'll find the subject matter is still of interest in
all of these.

Graham

 

[Eeyore]

"Dave Plowman (News)" wrote:

And to suggest no pro equipment ever gets abused by pros is pie in the
sky...

Many a JBL D150 went to meet its maker in the 70s. In flames quite often.

Graham

 

[Eeyore]

liquidator wrote:

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message

Any one have some hip boots ? my normal boots aren't tall enough!

Jeez- another idiot to killfiter- where are you pointing out what I said was
wrong?

Jamie is notorious (with me at least) for having some very odd ideas sometimes
in the electronics groups. I think he's a little bit out of touch with current
practice in this area.

Graham

 

[Eeyore]

liquidator wrote:

Dave we've gooten off on the wrong foot, but what happens is Eeyore starts
these damn crossposts.

He has been asked a number of times to stop.

He's a nice fellow but he keeps staring into space and mumbling
"crossposting is good".

What it does is throw groups of people together who don't know each
other...it ALWAYS wstarts fights .PERIOD.

I wish Graham (Eeyore) would stops as he's been asked to- but he's convinced
he's right, and no amount of logic is gonna change that..

According to the currently accepted rules of netquette, a post that is relevant
to several groups SHOULD be cross-posted. Most certainly not multiposted.

Explain how it is off-charter in rec.audio.tech or sci.electronics.repair where
a lot of audio is discussed daily. It was a repair question after all ! And
technical.

Graham

 

[Eeyore]

Jamie wrote:

Boy!, you're way out of your league..

Typical Jamie response.

Liquidator knows his stuff 99+ odd % of the time.

Graham

 

[Eeyore]

Meat Plow wrote:

"George's Pro Sound Company" wrote:
"Meat Plow" <meat@petitmorte.net> wrote in message

I wouldn't call Wharfedale junk. It's usable, sounds good and reliable
and a lot less expensive than other name brands.

I consider W home stereo grade gear, not suitable for Pro Live Sound, below
behringer

Glad to hear it. I don't suppose you're a musician who uses Wharfe
gear or repairs pro audio gear for a living, but rather just another
consumer or retailer who has an opinion.

He's a US (NY state AIUI) audio hire company operator.

As far as the Behringer gear goes I have no experience with it so
other than seeing a lot of negative comments about it from those who
do use or repair it I have no opinion.

Seen and heard of more Behringer gear die prematurely than any other brand that
one ought presumably to be able to take seriously.

Ron (UK) tried 2 of their big amps. Both went U/S just outside warranty.

OTOH, the venue I help out still has 2 of my Studiomaster D series amps working
day in, day out and both are 10+ yrs old. Only maintence needed, blowing out the
heatsinks and replacing a couple of scratchy gain pots. And you can replace those
pots in 15 mins compared to the over one HOUR it takes for a QSC RMX !

Graham

 

[Eeyore]

liquidator wrote:

Thee odd thing is most negative comments about Behringer do NOT come from
users as you say.

I've experienced their stuff fail on one of my clients. He will NOT buy
Behringer any more. He has a BUSINESS to run that requires RELIABILITY.

Graham