Ampeg 610HLF 'Lighting Up'

[NJW]

Hello hello.

Just in from a gig, and the support band used my Ampeg 6x10 cab with their Ashdown bass head. In the soundcheck, I was just standing minding my own business when I noticed out of the corner of my eye that the top 2 speakers in my 6x10 were glowing a violent orange.

I absolutely pat my shants and ran over and turned his head off. I then got him to play quietly and checked that both the speakers were functioning properly and sounding ok - which they were. He then told me that this was normal, and he has it all the time with his ampeg 8x10. He told me it is simply a 'level light' in the top of the cab.

I've played about 160 shows with my cab and NEVER had this happen before.

Did my cab just get buggered? I convinced him to play the show more quietly, and it didnt happen again... but this aint right, is it?

[warwickhunt]

Nothing on the Ampeg site or in the user manual. No mention of this being a 'feature' in reviews on Harmony Central. I'm certain Ampeg would make owners aware of a 'level light'!

I have a distinct feeling that this was the coils approaching toaster status. You don't say what he was using for an amp!

If it appears to be running OK you may have gotten away with it but I'd be testing it out at your normal and possibly higher levels (preferably before the next gig) to make sure nothing cr*ps out.

[Bigwan]

It could have one of those pxb lightbulb fuses in the crossover. Could explain it...

[andyonbass]

If its anything like an Eden cab, there is a lightbulb in the tweeter protection circuit which will illuminate when pushed hard, and will blow if pushed too hard, like a fuse.
Here's a quote from the Eden site
"[b]Calibrated light bulb[/b]. This is the one I think, in general, has the best overall performance and sound quality . This was introduced way back in the early 70s as a concept for tweeter protection. We have used variants of this circuit type since the mid 70s. The operation of the light bulb (if properly calibrated) happens in three phases:

Easy-over Compression
In the first phase of operation, the bulb appears to the circuit as a straight piece of wire. At low power it does not effect the circuit at all except for adding a couple of Ohms of resistance (impedance). due to its filament resistance. (Most other devices also add some small resistance or impedance.) At medium power, the bulb begins to heat up rapidly and its internal resistance also begins to go up causing a general rise in the total circuit impedance to the tweeter. This causes a soft, easy-over compression to begin to take place at the threshold predetermined by the bulbs internal current handling characteristics.

Hard Limiting
If the system power continues to rise until the total current capacity of the bulb is reached, a constant current source is achieved. This effectively acts as a hard limiter. This happens by the light bulb reaching the maximum current that it can allow to pass through itself. This in turn causes the load to develop mostly across the bulb. Most of the dynamic signal is dropped across the bulb, thereby protecting the load (tweeter). It is very important to all of the above that the bulb calibration match the tweeter characteristics exactly.

Fuse link
The final phase of operation by the bulb takes place only after some considerable time and in our case after 100 Watts (above kHz) is placed on the tweeter continuously. (This is real abuse - a Very Bad Thing.) The bulb finally becomes a fuse opening up and removing the tweeter from the circuit. This lets the player know that they have gone way over the top power-wise. The bulb is a snap in cartridge type and is located on the back of the rear crossover / jack plate. It is easy to service by removing the crossover plate.

[b]Additionally, the light will give early visual warnings that you are approaching the system limits. It is visible though the surrounds of the loud speakers. Having the light on occasionally is fine. It should not be on a majority of the time. The light only becomes visible when the voltage across it exceeds 24v to 28v or 72 to l00 Watts across the tweeter circuit[/b].

Protecting tweeters is always a compromise. We are always looking for better ways to protect the tweeters and, of course, ways to improve the power handling of the device itself. This represents the best of current technologies that are affordable in the real world today."


Similar thread to yours [url="http://www.eden-electronics.com/forum/topic.asp?TOPIC_ID=1159&SearchTerms=aircraft,bulb"]HERE[/url]

It [b]may[/b] not be as bad as you think

[warwickhunt]

Actually now that I've had a 'proper' coffee and woken up...

Where exactly was the light showing? I don't see how I could have thought it would be the coil, as you wouldn't be able to see that! However, a glow showing through the speaker cone indicates the source is behind the speakers. My slowly clarifying thoughts also make me realise that my H&K combos used to have a bulb for tweeter protection but I never had it light up. I seem to recall a few top end USA cabs used to have a similar protection (as Andy says), in particular the cabs Alphonso Johnson used (red carpet covered things... my memory/brain is shot this morning), had one of the speakers that specifically had this feature in/behind it.

[Oxblood]

Interesting...

Ampeg's user manual for the 610HLF doesn't mention any lightbulb protection device, which leaves me wondering just how they are hooking up those 6 drivers + tweeter to achieve 4 Ohms.

The manual doesn't mention a crossover either, so I guess we have to assume that the horn is a piezo (in which case it won't figure in any impedance calculation).

Why am I banging on about impedances? Well, there's more than one way to achieve a 4 Ohm load using six drivers. The commonest way is to use a set of matched 6 Ohm drivers and wire them in a pair of parallel trios. The trios are then wired in series with each other, like this:



If they are wired in this way, the power from the amp should be equally spread across all the drivers. But what if the internal wiring between the pairs of drivers is less than ideal for whatever reason: a poor solder joint, perhaps, or a guage of wire that is a bit...er...on the weedy side? Believe it or not, this is a possibility. I've seen inside several cabs from big-name manufacturers, and often been appalled at the pathetically thin wire they use to hook up the drivers.

If this were the case, the first driver in each trio would be forced to handle more power than the ones further down its ladder, because the thin wire would be unable to transfer enough current down the chain.

This is pure conjecture on my part, you understand. I'm just chucking ideas into the mix here. Tell you what though, NJW: I'd really like to see what's going on inside that cab, and find out how they've wired up all the drivers.

ADDED LATER:
I've just shot Ampeg an email asking how the drivers are hooked up and whether the cab uses a lightbulb protection device. We'll see what they say...or even if I get a reply!

Edited August 19, 2007 by Oxblood

[Oxblood]

Well that's a good start. My initial email to Ampeg's support dept resulted in an automated "out of office until the 25th" reply, which suggested that I send the query to [email protected]

So I did. Ten minutes later, it got bounced back: "User does not exist".

[andyonbass]

There's a few similar threads on T*lkbass, pertaining to Ampeg cabs so I would assume there is a bulb in there.

[NJW]

Wow thanks everyone, this is interesting.

Basically, the reason I felt stupid is that I usually think I'm quite up to scratch when it comes to the technical details of my equipment.

It certainly did look like a light source, rather than a heat source that was providing the light - but I panicked because I have never read or heard of Ampeg cabs including this feature. As you say, reading all the website information and manual - there is no mention anywhere of any sort of 'overload light' - but it seems to be exactly like the Eden. At the same time, I could see no way that anything in the cab could provide this light WITHOUT a bulb of some sort. I have seen PA speakers get toasted and it wasnt anything like that.

I suspect the reason it was happening was that the guy was using one of those Ashdown heads with the sub-bass (octave down) feature and he was pushing loads of unneccesary low end rubbish through the cab. Using my SVT, I can get a tonne more volume from the cab without having this light problem, so I think it was probably something along those lines.

Oxblood - if you do hear from Ampeg, I'd love to know what they say about the matter - because if there is a tweeter protection circuit in there, i'd like to know about it!

Thanks everyone!

[alexclaber]

Definitely a tweeter protection lightbulb. JBL pioneered this and many bass cabs have it. I believe the bulbs are usually in series with the tweeter, after the L-pad and crossover. If you put too much treble through your cab then the bulb will light, absorb the power and eventually blow. If you turn the L-pad down then less power will hit the bulb and it will not light - however the L-pad will have to dissipate that power and it may blow - quite a common problem. If you don't use the tweeter, disconnect it completely to avoid this.

An interesting thing about Acme cabs is that the protection circuitry (which used to be a bulb but is now a polyswitch which self-resets and doesn't blow permanently) protects the tweeter, midrange and L-pads. I gather that the increased resistance from the bulb in basic protection circuitry can lower the crossover point and cause more power to hit the bulb/tweeter and cause premature blowing of either - this was a problem with the earliest Acmes (Series I - replaced in '99) but the Series II cabs have impedance compensation which prevents this. I doubt many other cabs have this impedance compensation to prevent the crossover point shifting so although the bulb should protect your tweeter, it may not always.

[quote name='NJW' post='47359' date='Aug 19 2007, 01:23 PM']I suspect the reason it was happening was that the guy was using one of those Ashdown heads with the sub-bass (octave down) feature and he was pushing loads of unneccesary low end rubbish through the cab.[/quote]

Aha! What happens when you try to push too much bottom through a rig? Your amp clips! And what happens when your amp clips? The amount of treble energy increases substantially - and there's the problem. When I first had my Acmes I had a less powerful amp and was still in the habit of boosting my lows (so unnecessary, there's a ton of bottom with the EQ flat) thus causing my amp to clip. I used to blow bulbs quite frequently at the end of gigs when we were rocking out really loud, often using distortion too. The light effects were cool, seeing bright rings of light round each woofer surround. I now have tons of power, and haven't blown a bulb in years.

All that guff we hear about 'underpowering' being dangerous for cabs and clipping being dangerous for woofers is such rubbish. The only risk is having too little power for your given situation, thus clipping your amp and blowing not your woofers but your tweeter!

Alex

[MythSte]

i might install a light in my 810 just for kicks actually. Think it would look quite cool in a ported cab like mine. haha.

[Muppet]

Yup, I've got a 610HLF and it has this bulb. The 410s have them too. Protection system I agree, but it doesn't half need some seriously bad EQing to get it to light.

[Hamster]

[quote name='ste_m3' post='47530' date='Aug 19 2007, 11:26 PM']i might install a light in my 810 just for kicks actually. Think it would look quite cool in a ported cab like mine. haha.[/quote]

Inside and underneath perhaps? - You might start a trend



Hamster

[Tech]

[quote name='Hamster' post='47784' date='Aug 20 2007, 03:56 PM']Inside and underneath perhaps? - You might start a trend



Hamster[/quote]

wow, you guys just reminded of the coolest feature of my first ever giggable amp, a fender rumble 100 combo.

that thing had red LEDs in it, on the bottom of the cab, that lit up to your playing. hah that was badass.

[Cantdosleepy]

You guys really know your stuff.

Hats off gentlemen!

[NJW]

Has anyone got any concrete information on this yet?

Did we conclude that it was a tweeter protect light only?

The reason I've brought it back up is that this happened again the other day, this time with a bassist using a Mesa 400+ head through my cab, and a Boss ODB pedal. Everytime he hit the distortion, lots of light. Having a look at his EQ afterwards, again he was pushing a shitload of low end through the cab, but was complaining that he couldnt hear himself.

Hmm...

[MythSte]

I had this happen to my nemesis a few months ago when i pushed the "Boss HardComp" setting, i think it was due to a mixture of real high end feedback and a compressor pushing the signal more than i had intended too.

[Bill Fitzmaurice]

[quote name='NJW' post='103569' date='Dec 12 2007, 04:13 PM']Everytime he hit the distortion, lots of light.

Hmm...[/quote]Distortion boosts the high frequency power content, and that would cause the tweeter protect lamp to light up brighter than otherwise. Low frequencies won't light it up. To test this, turn the high EQ all the way off, the light will dim.
BTW, the increased HF content caused by distortion can fry a tweeter in a heartbeat, so if you use distortion turn the tweeter down.

[jammie17]

[quote name='alexclaber' post='47396' date='Aug 19 2007, 01:58 PM']Definitely a tweeter protection lightbulb. JBL pioneered this and many bass cabs have it. I believe the bulbs are usually in series with the tweeter, after the L-pad and crossover. If you put too much treble through your cab then the bulb will light, absorb the power and eventually blow. If you turn the L-pad down then less power will hit the bulb and it will not light - however the L-pad will have to dissipate that power and it may blow - quite a common problem. If you don't use the tweeter, disconnect it completely to avoid this.

An interesting thing about Acme cabs is that the protection circuitry (which used to be a bulb but is now a polyswitch which self-resets and doesn't blow permanently) protects the tweeter, midrange and L-pads. I gather that the increased resistance from the bulb in basic protection circuitry can lower the crossover point and cause more power to hit the bulb/tweeter and cause premature blowing of either - this was a problem with the earliest Acmes (Series I - replaced in '99) but the Series II cabs have impedance compensation which prevents this. I doubt many other cabs have this impedance compensation to prevent the crossover point shifting so although the bulb should protect your tweeter, it may not always.



Aha! What happens when you try to push too much bottom through a rig? Your amp clips! And what happens when your amp clips? The amount of treble energy increases substantially - and there's the problem. When I first had my Acmes I had a less powerful amp and was still in the habit of boosting my lows (so unnecessary, there's a ton of bottom with the EQ flat) thus causing my amp to clip. I used to blow bulbs quite frequently at the end of gigs when we were rocking out really loud, often using distortion too. The light effects were cool, seeing bright rings of light round each woofer surround. I now have tons of power, and haven't blown a bulb in years.

[i][b]All that guff we hear about 'underpowering' being dangerous for cabs and clipping being dangerous for woofers is such rubbish. The only risk is having too little power for your given situation, thus clipping your amp and blowing not your woofers but your tweeter!
[/b][/i]
Alex[/quote]


Hmmmm...will disagree with you here...you can damage woofers and tweeters all sorts of ways....as for the Ampegs..they have a bulb in the tweeter circuit for protection...

On the schematics (wiring diagram) for your 610hlf, here is a link that may be helpful to you.. [url="http://www.ampeg.com/support.html"]http://www.ampeg.com/support.html[/url]

If you need further help, I have a friend who works in Ampeg. Please email me and I'm sure I could get more answers for you about your cabinet.

Jim

Edited December 12, 2007 by jammie17

[jammie17]

[quote name='NJW' post='47269' date='Aug 19 2007, 01:53 AM']Hello hello.

Just in from a gig, and the support band used my Ampeg 6x10 cab with their Ashdown bass head. In the soundcheck, I was just standing minding my own business when I noticed out of the corner of my eye that the top 2 speakers in my 6x10 were glowing a violent orange.

I absolutely pat my shants and ran over and turned his head off. I then got him to play quietly and checked that both the speakers were functioning properly and sounding ok - which they were. He then told me that this was normal, and he has it all the time with his ampeg 8x10. He told me it is simply a 'level light' in the top of the cab.

I've played about 160 shows with my cab and NEVER had this happen before.

Did my cab just get buggered? I convinced him to play the show more quietly, and it didnt happen again... but this aint right, is it?[/quote]

I had a 410hlf which is the same design, minus two tens, and never lit up the protection bulb....but that's what it's there for....and what do you expect from an ashdown bass head? .....(Ducking for cover).....good name for them, as I hear they burn up now and then....

[MB1]

[quote name='Tech' post='51140' date='Aug 27 2007, 12:50 AM']wow, you guys just reminded of the coolest feature of my first ever giggable amp, a fender rumble 100 combo.

that thing had red LEDs in it, on the bottom of the cab, that lit up to your playing. hah that was badass.[/quote]

MB1.
It has a little slot vent in the front below the speaker which comes in handy for roasting chesnuts or toasting marshmallows .