ROCKFORD BURNT VOICE COIL - The rep cut my sub in half

[B1B2andB4]

Hey All,

Just wanted to share some info and see what ya's reckon.
I'm not much of a speaker man, so i took my suby to Autobarn to have a sub installed as the mcintosh had been unplugged when upgrading head unit.

After they talked me up to what they thought i would need, i was happy and they installed.
3 months later the sub stopped working, took it to them, they upgraded the sub to Rockford punch.
Now two months later it has happened again, i took it in to them, this time they removed box and sub and would show it to rockford rep.

Yesterday i called to find out, the voice coil is burnt and not covered under warranty?
When i tried to find out why, a host of explanations as to possible causes were given.

TOO MUCH BASS - no one told me not to play radiohead, i bought the thing for bass?
OVERDRIVEN - but you guys chose, installed and set the amp up?
TOO HOT - but you guys chose all the components?

This is why i had them install it! so it could all be done correctly..

Getting no where i asked for my sub back, i was then told " THE ROCKFORD REP HAS CUT IT IN HALF TO TEST IT"
Umm sorry but WHAT , "that is how they test them, he still has it with him"

I am looking into this further, awaiting a response from Rockford Australia.
At moment AUTOBARN (who are good guys) have my sub box, some guy has two pieces of my sub, and i have a useless amp and receipt.

Just thought i would check what you boys think, i must admit it has all left me feeling rather ripped off.

[teK--]

Burnt voice coil is often a symptom of heat (der! ) Causes:

- Amp was clipping which means the gain was not set properly (installer's fault). How did they tune the setup? Did they use a sine wave CD and an oscilloscope on the amp output to properly set the gain, or was it guesswork? Guesswork is OK as long as the installer is experienced, but it is still not ideal when you are paying them for a professional job. When the amp clips the sub heats up very quickly since there is no airflow at the extremes of the cone stroke.

- Excessive use/overload. This is partially your fault and partially the installer. Either for you/them choosing an inadequate sub for the usage intent, or for installing it in such a manner that it is not adequately ventilated. But really, you're just the customer how are you meant to know how to properly use a sub unless they said "No Radiohead for long periods of time!" Did you restrict them to an unrealistic budget?

- Manufacturing defect in the sub and/or amp. Very unlikely.

Perhaps the Rockford rep should be checking the tuning of the amp....

[B1B2andB4]

Hey Tek,

Cheers for help.
When i went back they checked the setup with CD/scope and said it was a clean signal from amp?
I'm guessing, what they were trying to say was.. this means it was my fault.
I first went in with an idea of budget but let them push me a little to this setup, i was only trying to have my mctosh re hooked up, this couldnt be done as not enough outputs from head unit. (previous owner install, all speakers direct from Kenwood head unit)

This issue happened after driving to Gympie other day, and enjoying music on the way up. (Never really been that much bass, no shaking windows,mirrors etc)
I was never instructed on usage nor given instructions after install.
I would assume that a sub once properly installed would be able to just work, no matter of what was played or length of time.
Although maybe not the same,when i play my guitar i am able to turn all volume up to max, playing whatever music for any length of time no hurt to amp/speaker.
If amp/sub installed correctly,i thought i would get the same result from the amp/speaker installed in my car, even if i pushed head unit volume a little.

I really don't expect much love from Rockford, i am just trying to figure out the problem to save myself a few $ when i install a new sub, i don't want it to happen again.

[teK--]

What type of box did they give you? Sealed or ported? Sealed ones are more resilient to being overdriven.

Your ears would have been the best judge. Do you know what it sounds like when a sub is bottoming out or distorting? E.g. just because the head unit goes up to 40 doesn't mean you could listen to it at 38. In that situation I would have tuned the amp to peak out when the head unit is at around 30 which would suit *most* situations (all music is different).

Probably a long shot but if you remember what volume setting you were using at the time, if you hooked up the scope and played the same track(s) again you could replicate the situation and would know if you actually blew the sub yourself.

[Boxer]

Voice coils only get burnt from one thing - clipping or square waves.

Basically it means you were putting straight DC voltage across the coil from and amp that is clipping. DC voltage in a wire wound coil = lots of heat very quickly, just like a toaster

Yes it could have been the installer setting gains incorrectly and overdriving it early(beofre max volume on your head unit) But really they cant set it up for EVERY situation and every type of music.

Your ears should have told you the bass was distored and muddy. Clipping is bad and will destroy the most expensive speakers very quickly.

Generally not ever a warranty issue.

GET A BIGGER AMP!

Also tek - sealed enclosures are good protection (more resilient) to TOO MUCH POWER, saves the driver from maximum excursion, it will do nothing to protect against clipping

[B1B2andB4]

Okay just had a courtesy call from autobarn.
seems someone is going to help (said rockford were coming to party)
but they are going to upgrade me to HERTZ brand apparently better?

It will cost me a little for them to upgrade me to HERTZ, which i am happy with.

At least they want to help (one of the guys has a nice 07 lib, he's the one helping- i think he wants my rims )

In regards to bigger amp, wouldn't this be more power?? i think i'm scared of more power till i stop blowing subs.

[NoOzL47]

Im trying to get my head around why he had to cut the sub in half to check the voice coil...

If he couldn't smell it, push down on the sub and you can feel it

[teK--]

Hertz are beautiful speakers, very smooth as opposed to American speakers like Kicker and RF which are all about being loud. They were Italian made the last time I bought a set, and I'm pretty sure they still are.

[Boxer]

In regards to bigger amp, wouldn't this be more power?? i think i'm scared of more power till i stop blowing subs.

Didn't you read what I wrote above?

You have fucked the voice coil from overdriving the amp into distortion (clipping)

Get a bigger amp for more power to get the bass you want without over driving the amp

Common misconception is blowing up speakers from too much power - 99% of the time it is due to too little an amp driven too hard and causing it to distort.
Too much power will cause the cone to move to maximum excusion and usually give a loud POP as it hits the stopper. In extreme cases I have seen cones launch completly out of the spider


Also - use your ears - if its sounds bad - then it is

Oh and 'upgrading your speakers' will do nothing to alleviate the situation that led to your original damage. But I'm sure Autobarn is full of audiophiles that know what they are doing

[B1B2andB4]

Thing is - i don't want THAT much bass, just some of bass taken away from rest of speakers and a little punch.
It never sounded bad/distorted? just stopped working.
Happy to get a bigger amp-This is what they chose to install.
Am i wrong to think if whatever amp chosen was set correct, it should not clip/distort?