Anyone else having an issue with MarkBass heads melting speaker cabs?

[BigBottomNYC]

Hey All-

I've been a satisfied owner of Mark Bass heads since 2007. As a full-time freelance player, I've used them for a variety of gigs, 3-5 times per week with no technical problems until last month when two different bass speaker cabinets overheated (smoke pouring from speakers after resistor in the crossover melted) within a two week period.

The first rig was a LittleMark2 with a 4 ohm Avatar 210B cab, and the other was a MarkBass SD800 with an 8 ohm Eden 410XST cab. I wasn't pushing the voulme levels very hard in either situation, and both heads are well matched for the power requirements of the speakers.

The only apparent connection is that both of these meltdowns occurred with the same wedding band that has a large, elaborate lighting system. An audio engineer friend of mine suggested that the draw of the lights on the current might cause the special lightweight MarkBass transformers to work too hard, but the sound guys for the band completely dismiss any suggestion that the stage setup is a possible factor.

If anyone with knowledge of MarkBass heads has any insight or theories, I'd greatly appreciate it. Thanks!

-Trevor

[KJung]

Nope. Seems like something else in your signal chain is causing you to overload your tweeters. Two different cabs, two different heads with very different types of designs... same problem. That typically means something else is the causal factor.

[Handyman]

Did you have the tweeter turned all the way off when this happened?

[greenboy]

Originally Posted by Handyman

Did you have the tweeter turned all the way off when this happened?

Bingo, underdesigned underspec'd crossover.

[Nightlyraider]

What they said. Too much heat built up in those little rotary resistors = poof!

[Eublet]

Sounds like what others have said. I suggest that you run the tweeter at 9 o'clock or higher on all cabs, and then use the wondefully effective VLE knob on those MB heads to pull out additional HF if you wish. The combination should still give you a warm tone without all the potential for destruction.

[billfitzmaurice]

Originally Posted by Eublet

Sounds like what others have said. I suggest that you run the tweeter at 9 o'clock or higher on all cabs.

+1. If your highs are too much don't automatically turn down the tweeter control. That just burns off the highs from the amp, literally, with potentially catastrophic results. Turn down the high EQ on the amp so that the amp doesn't send that high frequency power to the speaker in the first place.

[KJung]

I'd be a bit surprised if that was the cause. I've known guys running Eden cabs with the tweeters turned off for years at stupid high volumes with no trouble.

I guess it could happen, but I thought most of those issues were way back in the day, and long ago fixed (i.e., having issues if you turn the attenuator all the way down).

Who knows though, just never heard anyone having an issue like this, at least in the last 20 years or so.

That being said, I guess if it is a situation like Bill describes, where he has the attenuators all the way dialed down, AND a huge boost in an active treble control, it could be a problem. I guess we will wait and see what he says.

[rodl2005]

Originally Posted by billfitzmaurice

+1. If your highs are too much don't automatically turn down the tweeter control. That just burns off the highs from the amp, literally, with potentially catastrophic results. Turn down the high EQ on the amp so that the amp doesn't send that high frequency power to the speaker in the first place.

I bypassed the tweeter in my Mark Bass HR115. This is an ok way to 'exclude' it without possibility of 'burnout'?

[fdeck]

That's what you get for buying an amp that puts out its rated power.

[billfitzmaurice]

Originally Posted by rodl2005

I bypassed the tweeter in my Mark Bass HR115. This is an ok way to 'exclude' it without possibility of 'burnout'?

That depends how you bypassed it. If you totally removed the crossover OK. If you just disconnected the tweeter there's potential for amp damage.

[rodl2005]

IIRC, I wired the 15"driver straight to the input, so should've bypassed the whole 7-over. Must double check. Thanks.