GK 212MBE/4 4ohms burnt out in 30 Sec.

[1958Bassman]

I just got 9 months old, hardly being used, mint condition GK 212MBE and GK 1001RB II. Before I buy, I tried it with more than bedroom volume levels to make sure everything works fine. It did sound great.

I took to my band practice all excited, but within 30 seconds of playing (I'm not lying, didn't even finish the intro of song.) with rock band practice level of volume, however, it wasn't even turned half way up, cabinet started smelling burnt rubber. One of the speakers was burnt out. Very embarrassing.

I called the GK customer service next day, and he kept telling me "I overpowered the cabinet" as if I cranked the amp all the way up to kill it. But like I mentioned before, it wasn't even turned half way up, and didn't even lasted a minute. He was only defensive about his product, and responsibility was all on end-users.

I think that was a defective speaker to begin with, and attitude of GK's customer rep really made me mad. I even started assuming that they are hiding some known issues about their speakers that they don't want to disclose (or recall) to the public. Only one thing I'm for sure is I'll NEVER ever buy any products from GK ever again!!!! Horrible product and horrible after-care. Definitely WORTHLESS!!!

Did anyone have the similar experience with GK's cabinet?

First off, you're saying GK is worthless when you're not the original owner. Second, you posted NOTHING about the rest of your rig, how the controls were set, your playing style (if you slap/pop, play chords and lots of double stops or slam your palm on the strings, etc) or anything else.

If you play a 5 string, boosted the low end, used the boost control, play lots of chords and double stops and did all of these at the same time, you did a lot of things that are outside of the normal range of the speakers and cabinet. Just having two 12" speakers doesn't mean it can play 20Hz. It's not rated for that, it's not meant to produce that and playing a low E and low B will produce a beat frequency of about 10Hz, which is definitely able to kill a lot of speakers. Add some boost with the Bass control, you just killed your speakers. You think it was a defective speaker, but again, it was 9 months old when you bought it. Is it not possible that the previous owner is the one who did most of the damage?

 

[1958Bassman]

Back of the 1001RB II says;
Speaker Loads/ 700W Amp (Woofer/Master)
One or Two 8 Ohm Cabinets
or One 4 Ohm Cabinet

8ohm or 4 ohm, which one is more durable or resists more against power load from the amp???

I wish I didn't have any problems like you.

Which output jack did you use? If you used the high pass output, it's the wrong one- that one is rated for 8 Ohm loads, not 4 Ohm. Did you read the manual before using it? I would advise doing this, so you know what it can do, what it was made to do and any differences between what you did and what the way it's supposed to do.

8 vs 4 Ohm is for amp designers, more than anything else. Well, amp designers to make sure of what the amp CAN do and for users to follow, so the speaker load falls within the range that will allow the amplifier to perform as intended. A 4 Ohm speaker and an 8 Ohm speaker, each rated for 300W will see different voltage at 100W. An 8 Ohm speaker sees 28.3V and the 4 Ohm speaker sees about 20V when the power calculates to 100W (P=E²/R, meaning P(ower) = E²(Voltage, squared) divided by R(esistance). This doesn't mean you have to measure the voltage, but it does mean that you need to pay attention to the speaker loads, in order to not make the amp do something it's can't. If an amp's output jacks show 8 Ohms, drive 8 Ohms, not 4 Ohms. That causes the amp to overheat and can damage the output section. If it shows 4 Ohms, you won't hurt it by connecting it to 8 Ohms, it just won't develop as much power.

The comment about adding a cabinet is valid- if you use two 8 Ohm cabinets, the amplifier will see a total load of 4 Ohms, because the jacks are wired so they both go directly to the amp's output without sending the signal through one speaker before it can go to the other. This is called 'parallel' and since the load is shared, it's reduced- two of the same cabinets cuts the load in half (the formula for this is (R1 x R2) divided by (R1 + R2). This all goes back to the power formula- if you cut the load, you increase power output (assuming the amp can handle the load) and if you add a cabinet, you also gain output level because you now have more speakers producing sound. If you use one 8 Ohm speaker with a given wattage, you get a certain amount of output level. As soon as you add a similar speaker, you gain output in an amount that's similar to what you would have if you quadrupled the power. Using more power into one cabinet only works to the limits of the cabinet and can lead to problems.

 

[Andyman001]

Also contact place you bought it.

 

[ThisBass]

There is a lot of misunderstanding all along the line regarding to amp power vers. cab power handling.

Cab power handling most of the time refers to the manufacturers speaker power handling AES/RMS.
The power handling is measured with peak limited and band limited pink noise. Peak limited means +6dB Crest which is +6dB Peak To RMS Ratio.
So overpowering the stated power handling does NOT automatically mean that the voice coil will be melting.
A 600 Watt RMS Pink Noise signal contains +6dB hard clipped Peaks which calculate to theoretical 2400 Watt peaks.

So overpowering a 600 Watt cab is not as easy as it looks like.
To tell it with easy understanding words:
it is impossible with 700 Watt amp power to amplify a 600 Watt test signal like the pink noise with which the speakers of the cabs where tested.
To amplify this 600 watt Pink Noise test signal without clipping there is a power of 2400 Watt necessary.
That means that the peaks of the Pink Noise signal are theoretical 2400 Watt but the signals average RMS is based to 600 Watt RMS only.
That's not a cheap trick. The reason why regards to the physics of audio signals.

But I would never anybody suggest to overpower the cab with 4 times the rated RMS/AES power handling, even if it would be possible to do it like that.
But never the less there are some experienced people out there which do it in practice like that.


600 Watt Power Handling AES/RMS does not automatically mean that the speakers received 600 "heating" Watt during the power handling test.
The amount of power handling is of theoretical nature only because it is calculated by Zmin for AES power handling, whereas for RMS power handling the power is calculated by Znominal.
Sometimes the values for Zmin and Znominal are significant different, so the power handling calcultes to significant different values, depending on which method was used for power handling test.

 

[Jerrold Tiers]

A cab rated @ 600w does not mean it can take 600 watts. That is the THERMAL rating at which the voice coil will melt (usually when fed a 1Khz signal). Depending on how much low end EQ you use, the real world mechanical limits are about 1/2 the thermal limit.

Also, "knob position" mean nothing. Most amps are already putting their full output at around 1/2 volume knob based upon how you EQ.

Could very well have overpowered the cab.

This is of course not actually true......

The thermal rating is where something, usually the glue, will be damaged in the voice coil assembly. it isn't where it "melts".

It is perfectly possible to design a cabinet which will take the power acoustically, right up to the thermal limit, over the entire rated range. I have done that, and prefer doing designs that way.

Knob position,.... that is correct, it is not a calibrated power control, it is relative....

It is unlikely that even a cabinet rated at or slightly below the amp rating will get damaged. You are unlikely to damage a properly designed cabinet with DOUBLE the power it is rated for.

The only way you ever get full amp power into a speaker is to somehow hold a note perfectly with no die-out... as with feedback, or testing in the lab. Regular strings will have the note die-out.

And that perfectly stable note is not very musical..... seems to lack that "swing", yah know?

When you are actually playing music, you will work really really hard to get up to 1/2 or even 1/3 of rated power on average.

Since the OP reports a"smell", that suggests a thermal problem, NOT a "mechanical" problem, which may be due to the cabinet having been damaged before he ever got it. (it WAS bought as used, right?).

With 460Watts available, and a 600Watt thermal rating...... if that speaker was even sort-of correctly designed, he should have been pretty darn safe.

In many cases, the power ratings of speakers are what engineers call a W.A.G..... which amounts to throwing darts at a wall.... That's due to marketing getting control of the published ratings.

With GK, I'd not expect that, they know a thing or two and shouldn't have marketing-driven specs.

 

[ThisBass]

The only way you ever get full amp power into a speaker is to somehow hold a note perfectly with no die-out... as with feedback, or testing in the lab. Regular strings will have the note die-out.

Probably the power in this case would only be less then 50% of the rated amp power.

The reason why is very simple. All audio signals like a bass guitar signal have got a very high crest. Even for sustaining notes the crest is significant higher then for sine waves.
That means that the bass signal clips audible long before the rated amp power is reached.

I point out that it is not possible to yield more then 1/3 of the rated amp power with a bass guitar just before the amp starts to clip audible.
Sine waves are very different animals, but we all don't play sine waves. We all produce tons of very complex waves which are impossible to describe by firm numbers.

 

[ThisBass]

Since the OP reports a"smell", that suggests a thermal problem, NOT a "mechanical" problem, which may be due to the cabinet having been damaged before he ever got it. (it WAS bought as used, right?).

That's right. A damaged voice coil does not mean that the speaker does not work at all. Sometimes a pre damaged voice coils works further for a very long time before it dies.
There are some practical methods how a pre damaged voice coil may be identified. Sine waves can detect damaged voice coils.
Playing with the bass guitar is not a reliable cab testing. Little distortion in a small frequency band is very hard to identify with ears.

 

[1958Bassman]

I'm still wondering if it survived 9 months of abuse by the previous owner and it was at the brink of failure when they sold or traded it.

 

[Slowgypsy]

You bought used. What does "mint condition" mean to you, 'cause it means more to me than the outside has been cleaned and looks good. What kind of use or abuse did this get in its former life? GK makes well engineered solid stuff, and I take offense at your mouthing off at this company... GK does not deserve this kind of rant.

 

[Jerrold Tiers]

I point out that it is not possible to yield more then 1/3 of the rated amp power with a bass guitar just before the amp starts to clip audible.

That's about correct.....

But styles differ, and someone playing certain styles might not be overly concerned with a little clipping, so they may stress the speaker more..

Getting over 50%? I very much doubt it.

The case of feedback is special.... it turns the "system" into an oscillator, and tends to produce a fairly good sine wave. The harmonics die out naturally, and only the basic frequency (might not be the string fundamental as-fretted) is reinforced.

I wouldn't worry about the details.... the bottom line is that work as hard as you want, you will not get anything close to the amplifier power rating into the speaker continuously.

The major reason why it is important at all, is that with a very powerful amplifier, you may be able to drive the speakers past their mechanical limits at least on a transient.... that damage adds up over time, eventually resulting in some type of failure.

Also, trying to drive a ported speaker to low low frequencies below the box frequency.... that can also do mechanical damage. The speaker is not well "controlled" in that range.

 

[BassmanPaul]

OP, just as a matter of curiosity, what is your competition (guitar player) using??

 

[2milehighspike]

You bought used. What does "mint condition" mean to you, 'cause it means more to me than the outside has been cleaned and looks good. What kind of use or abuse did this get in its former life? GK makes well engineered solid stuff, and I take offense at your mouthing off at this company... GK does not deserve this kind of rant.

I could not agree more!

 

[bumperbass]

Well, I can't side with the OP on this one. 'Mint condition'? 'Used'? The previous owner could have abused the heck out of the cab in a clean room at Intel, for all we know. Since the OP's not the original owner, sorry about your luck. G-K is one of the most respected companies out there! Bob is a top-notch guy, from what I have seen. I own a NEO212II and couldn't be more happy. It's poor taste to bash them on a BASS FORUM, especially when G-K is a BASS company. Then for you to say "I'll NEVER ever buy any products from GK ever again!!!! is hilarious. If you said that about every brand that ever gives you a problem, then sooner or later you'd have to start making your own amps and cabs, because no product is perfect. Buy a new speaker or two for the cabinet and just play, assuming that cab suits your playing style and your particular demands in the first place.

 

[B-string]

To point out, if you bought used YOU didn't buy FROM G-K in the FIRST place. Someone else did.

 

[Lee Bruton]

YMTJ, Your not going to get anywhere being all pissy with GK. And I don't blame them!