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Author Topic: Help with possible blown speaker  (Read 5959 times)

Matt Carter

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Help with possible blown speaker
« on: February 28, 2011, 02:31:25 AM »

I have a small PA consisting of a mackie 1200 pushing 2 Klipsch 500w cabinets. These have served me well over the years, but in the last couple of weeks, one of the cabinets sounds like it is cracking.

We are only using one channel of the mackie (600w) and jumping the two cabinets off of this single amp channel. Since each cabinet is rated 500w at 8ohms, I would think that the cabinets could handle being wide open.

When playing recorded music, this cracking doesn't happen, however when the band begins their sets, you can here the cracking, especially with vocals and keys. We are using an active crossover with subs.

before I go spending on new cabinets I was hoping to get some troubleshooting tips from some forum users who are more knowledgeable than myself on possible solutions.

Anyone have any ideas or suggestions?

Thanks!
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Tim Talbot

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Re: Help with possible blown speaker
« Reply #1 on: February 28, 2011, 09:58:49 AM »

Am 90% sure that will be the voice coil rubbing which is normally due to the cabinet being dropped at some point thus shifting the driver magnet of out place causing the rubbing and cracking sound.

Tip the cabinet on its back and push down on the driver, if you can feel and hear rubbing you have found the problem and it would need a new driver.

Good luck

Matt Carter

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Re: Help with possible blown speaker
« Reply #2 on: February 28, 2011, 05:18:38 PM »

Thanks for tip Tim. I fully intend to take this apart and get to the bottom of it.

Whilst I am there, I got to wondering if I am indeed running this system at peak capacity (at least peak as possible).

Forgive my newbie ignorance, but I am trying to learn and make sense of this since I own all of this gear.

Top cabinets are Klipsch KP 320 (i can find no reference to these anywhere) rated at 500W @ 8ohms. Powering these cabinets is ONE channel of a mackie FR-1200 giving them 600w with 2 ohm nominal. That's where I start to get a little confused. Even with parallel inputs on the Klipsch cabinets and jumping them off, how are they getting enough power to blow?

Rain crossover - 2 peavey 118 subs, powered by a QSC 1600. These get one amp channel per cabinet, so plenty of power.

Should I be running these in some different way to maximize the power of the cabinets?
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Bob Leonard

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Re: Help with possible blown speaker
« Reply #3 on: March 02, 2011, 09:40:33 AM »

Thanks for tip Tim. I fully intend to take this apart and get to the bottom of it.

Whilst I am there, I got to wondering if I am indeed running this system at peak capacity (at least peak as possible).

Forgive my newbie ignorance, but I am trying to learn and make sense of this since I own all of this gear.

Top cabinets are Klipsch KP 320 (i can find no reference to these anywhere) rated at 500W @ 8ohms. Powering these cabinets is ONE channel of a mackie FR-1200 giving them 600w with 2 ohm nominal. That's where I start to get a little confused. Even with parallel inputs on the Klipsch cabinets and jumping them off, how are they getting enough power to blow?

Rain crossover - 2 peavey 118 subs, powered by a QSC 1600. These get one amp channel per cabinet, so plenty of power.

Should I be running these in some different way to maximize the power of the cabinets?

There are more possabilities than just a speaker here. I have to assume that you are running the amplifier in bridged mode single channel. If you are not then that should be the first thing you change.
 
You are not presenting a two ohm load to the amplifier. What the amplifier will see is a pair of 8ohm speakers running in parallel. The load will be 4ohms, which according to the Mackie specs for the amp will provide up to 1260 watts of power to a 4ohm load.
 
The speaker rating according to Klipsch is not 500 watts. They spec the speaker at 300 watts continuos, and that is the rating you should work with.
 
Therfore if your speakers are rated at 300 watts, and using the generally accepted rule of thumb, amplifier output = 2x speaker long term handling, the requirement will equal 600 watts per speaker.
 
With the amplifier set to bridged mono and providing 1260 watts into a 4 ohm load you appear to have a matched combination.
 
I would also suggest you check your effects units. Being that you stated recorded music does not create the crackling sound you are hearing I might suspect that you have checked the signal path from the source where the problem can be replicated.
 
Just be aware that lower cost or "budget" effects units will often overload and the result will be a snapping or crackle as the unit is overloaded. The cure for this problem could be to simply turn the units input level down. This overload may be more noticible when your lead singer yells or is accompanied with additional backup vocals.
 
Check the affects path, and route an aux send, or sends if the unit has multiple DSPs, to the input of the effects unit. Take the output of the unit and route it to an unused channel input(s). Set the effcts for the proper input and output levels and leave them alone. Use the vocal channel(s) aux levels to set the individual effects amount for each channel, and use the faders on the channel(s) the effects are routed to for control of the overall output level. This works good and should last a long time. 
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Matt Carter

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Re: Help with possible blown speaker
« Reply #4 on: March 02, 2011, 06:55:41 PM »

Thanks Bob,

Thanks actually pretty awesome troubleshooting, as I do seem to recall us having some issues with our effects unit recently.

We are using a Lexicon MX200, which I thought to be a pretty good "budget" unit. I haven't taken the cabinet apart yet, so I think I'm gonna try tweaking the effects unit before assuming its the horn or blown speaker.

As for the cabinet and its power, I have been trying to find some info myself on this. I downloaded one manual I found and saw the same info you did - 300w. Just so you don't think I'm a complete idiot (may be too late for some) -  I am trying to posta pic as to why I thought it was a 500W cabinet (its printed right on the back "8 ohms nominal 500 watts).

Either way, thats for the tip. I've got some good angles to approach this issue from now, and it looks as if its just gonna take some drilling down to find the real source of the buzz.
« Last Edit: March 02, 2011, 07:01:04 PM by Matt Carter »
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Jordan Wolf

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Re: Help with possible blown speaker
« Reply #5 on: March 03, 2011, 01:02:02 AM »

Matt,

Your picture notes the speaker is rated for 500W @ 8 Ohms and that the testing standard they used was AES2-1984.  This standard sets forth a testing procedure that the loudspeaker components are tested by.

Section 2.a. of this webpage should give a good overview of it.
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Matt Carter

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Re: Help with possible blown speaker
« Reply #6 on: March 19, 2011, 02:56:12 PM »

Okay, so I took it to our local Speaker Doctor and found out the internal crossovers need re-soldering. They took care of that and with one gig down, the cabinet seems to be in good working order.

Thanks for all the advice  :D
« Last Edit: March 19, 2011, 03:08:09 PM by Matt Carter »
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Sheldon Harris

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Re: Help with possible blown speaker
« Reply #7 on: March 19, 2011, 08:40:59 PM »

Okay, so I took it to our local Speaker Doctor and found out the internal crossovers need re-soldering. They took care of that and with one gig down, the cabinet seems to be in good working order.

Thanks for all the advice  :D

matt,
those Klipsch do have a nice sound. glad you got your problem solved, but i think you should take it a step further and invest in 4 neutrik speakon size d panel mount terminals, and swap those 1/4" input terminals out. those things suck and could cause you a lot of grief later on.

sheldon
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Matt Carter

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Re: Help with possible blown speaker
« Reply #8 on: March 19, 2011, 10:02:31 PM »

Thanks for the tip Sheldon. I just acquired a set of Woodworx WA-15A cabinets that have those type of connectors. Being a newbie (I'm actually the drummer in our band, and just happened to have accumulated gear over the years), maybe you could tell me what makes those connectors superior. I could be game, but the 1/4" inputs have been there since I got the cabinets some 11 or 12 years ago, and I'd like to know the advantage/disadvantage to the speakon connectors.
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Tim McCulloch

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Re: Help with possible blown speaker
« Reply #9 on: March 20, 2011, 04:57:20 PM »

Thanks for the tip Sheldon. I just acquired a set of Woodworx WA-15A cabinets that have those type of connectors. Being a newbie (I'm actually the drummer in our band, and just happened to have accumulated gear over the years), maybe you could tell me what makes those connectors superior. I could be game, but the 1/4" inputs have been there since I got the cabinets some 11 or 12 years ago, and I'd like to know the advantage/disadvantage to the speakon connectors.

Primary advantages are: much higher current rating (the contact surfaces are vastly greater than a 1/4" phone plug); they LOCK and can't be pulled out by a simple tug on the cord; they have more contacts available (the NL2 not withstanding) allowing you to double up on conductors for less cable loss or convenient bi-amping.
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Re: Help with possible blown speaker
« Reply #9 on: March 20, 2011, 04:57:20 PM »


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