Keep blowing up my monitor rig

[Chewey]

Hi guys, May I get a quick word of wisdom?

 

I use a mackie dlm12 as a monitor with my keyboard rig. I love it. However, it is starting to exhibit that burning speaker smell in certain situations. Typically I run a Moog sub phatty and a computer/controller. At my loudest I am running into both inputs from a line mixer. Volumes on dlm is at 6, mixer is rarely above 5. I really want to protect the dlm, but I need to hear myself.

 

I have tried powered speakers, passive monitors with a power amp, and in all situations I keep blowing up gear. I think the Moog is the culprit, what can I do to protect my rig? Thx,

[PianoMan51]

I'm going to assume that the mixer is active. If so, it's buffering the signals from both sources, and any weird DC or grounding issues from your sources would be stopped.

 

So, I would troubleshoot this from two points of view:

 

1). The mixer or cabling is defective. Borrow a replacement from a friend and try it out.

2). The Moog may be outputting a lot of sub-sonic signal that you can't hear, but is overloading your speaker. Put in a filter to drop out the super lows. Forgot to ask if you're using the Moog for bass. ???

[Jim Alfredson]

My Voyager popped the driver on my Yorkville powered speaker twice. Those babies can put out some frequencies that we can hear, both subsonic and supersonic and they can fry cheap speakers.

 

Gonna have to filter it, bro.

[Chewey]

Thx. What would be an example of a filter I could use? I've blown qsc k's, carvin passive speakers, and now my $600 mackie dlm 12 is suspect... these are not cheap speakers.

[mate stubb]

Just how loud are you playing? If you are really cranking it, I'm not sure typical modern powered speakers can handle the load.

 

You might try going old school - big passive JBL cabinets with PA quality power amps.

 

Or go find one of these bad boys:

 

[Chewey]

Yes active mixer. Alesis line 8. Yes lots of bass and everything in between.

[Jim Alfredson]

Thx. What would be an example of a filter I could use? I've blown qsc k's, carvin passive speakers, and now my $600 mackie dlm 12 is suspect... these are not cheap speakers.

 

Yeah, they kinda are. I mean not cheap to you and me, but compared to like a JBL Vertex system or something, they are.

 

You need something that can handle extended frequencies. And maybe with a fuse between the driver and the amp.

[Ledbetter]

Have you tried a 15"?

[GRollins]

You need subwoofers. Let them handle the low end.

 

Grey

[Chewey]

Well, I play in a 5 piece rock band with 2 guitarists and a bass player. The guitarists have a Vox AC30 combo and the other has a 100w Hiawatt head through 2x12 cab . They are never above 5 on the dial and we are very conscious about trying to manage our volumes. Our lead guitarist is usually sitting at 3-4. But its a rock band, its loud... and 2 on a tube amp is louder than most keyboard amps max, most of those amps are completely useless imho. I am just loud enough to hear myself on stage.

 

With a 5 piece it is very common to show up to a gig that has only 2-3 monitors, making it a big maybe weather or not I can run keys through the house monitors and actually hear myself. This is why I would rather bring my own monitor support and control the situation. When I can rely on the house, I do.

 

There are other gigs where there are no available house monitors and we are all expected to run all run through our amps. In those scenarios, I run a 250w solid state 2x15 vintage Kustom rig which is great for this application. It colors the sound a tad, but in a good way and not to the degree that a tube amp would. It works for all my keyboard sounds, looks cool, and keeps up in spades.

 

But hell, I don't what to have to haul that thing around to every gig. Might as well bring the Hammond.

 

Seems there is a major gap in the market place when a guitarist can purchase a 100w tube combo for under $300 bucks and a keyboardist has to purchase a $1200 high end pa wedge as Jim suggests just to keep up.

 

I have tried a 15". I used a passive Carvin SCX 15" wedge for a while with a 2k watt power amp. That was around $600. Then there was the 1k watt QSC K12, that was $800. And now the 2k watt Mackie DLM12, which actually retails for around $800. It has been awesome... I love the format, but that smell is foreboding.

 

There must be something in my chain that is destroying these rigs. I gotta figure this out. I am tired of tossing money down the drain.

 

Thx everybody for your input.

[Chewey]

Like the subwoofer suggestion... that makes sense

[J. Dan]

You can't compare what number (0-10) one amp is compared to another. It has absolutely nothing whatsoever to do with volume.

 

The subwoofer is a good suggestion, just make sure there is a crossover so it's filtering out the lows to the other cabinet.

 

Also, if you already are smelling "that burning smell" then you've already damaged the speaker even if it still sounds OK.

 

Another suggestion would be to add a limiter to prevent you from pushing it over the edge.

[mate stubb]

Don't fall into the trap of looking at guitar player watts or low numbers on a volume dial. It all means less than nothing.

 

The amount of watts (especially tube watts) needed to destroy your ears via a midrangey guitar is frighteningly small.

[Chewey]

I don't think it is vol thing. My loudest project is not that much louder than my other two projects and we have shared the stage with way louder bands and I am not maxing out the gear?

[DanL]

You are getting that burning "band aid smell" but the speaker is not blowing up? I get that band aid smell with my EV's once in a while. My bass player gets it with his rig too. Neither of us has blown up anything.

[Chewey]

Ha! Yea... totally "band aid smell"

[GRollins]

The windings of the voice coil are held on the coil former with adhesive. There are different grades of adhesive, depending on temperature. When you heat the stuff, it can start cooking, which can be smelled. The insulation on the wire (urethane, shellac, etc.) can also give off odors. The coil former can be made of different materials; some smell when heated (e.g. plastics), some don't (e.g. metal or paper).

 

General rule of thumb: Smells are bad.

 

What causes the heating? This could turn into a lengthy post and I'm short on time at the moment. Quick overview:

1) Too much wattage. Note that you could be frying your amp, in addition to, or instead of your speakers. And, no, I don't want to hear that your built-in Class D amp has three million watts. This is where the post could turn into a dissertation.

2) Oscillation. If, for whatever reason, you have circuit instability anywhere ahead of the speaker, that generates ultrasonic oscillation. That power goes through the speaker. You can't hear it, but it's there. If you're running a passive crossover, the tweeter will go first in a full range speaker. If you're bi/tri amped, everything's up for grabs.

3) Clipping. Again, I don't want to hear about how you've got enough power to run New York City. Clipping turns everything into square waves. Apply Fourier Analysis and you'll see that you've just added high frequencies to your signal. Yep, clipping can sound good. Adds texture to your tone. But...you can kill drivers that way. Ask Jimi Hendrix, et. al.

4) Overexcursion. Asking your drivers to exceed their Xmax (how far they can safely travel back and forth before destroying themselves) is a sure way to kill them.

5) Etc. There are some much lower probability things that I will leave for another day.

 

Without having examined the corpses of your dead speakers, I have no opinion as to which of the above applies. I'm just offering some background.

 

Grey

[The Real MC]

There must be something in my chain that is destroying these rigs. I gotta figure this out. I am tired of tossing money down the drain.

 

I play in a 5 piece rock band with 2 guitarists and a bass player.

 

Take it from someone who has gigged with loud bands since the 1970s: today's gear doesn't measure up, and there is better gear not found in stores or online retailers.

 

That "something" that is destroying your rigs would be class D amplifiers and inadequate drivers.

 

Wherever you see a speaker with an integrated amp, it's a class D amplifier. Class D is a widely adopted architecture that can deliver more watts with much less weight and far less heat - but at a cost. Despite the 2000 watt tag of the Mackie, the devil is in the details. One, class D isn't entirely reliable either in reproduction or power delivery. I've seen too many of them in repair shops. Your Moog may be the acid test of these things; the Moog isn't the problem, the amps are.

 

Two, in the cost competitive race to deliver lower priced products to musicians like us, corners have to be cut somewhere and those corners are often the drivers. EV is renowned for their speakers but the drivers they install in their self-contained monitors aren't the good stuff, they are a compromise.

 

Three, being an EE and well versed in PA sound reinforcement (including different classes of amplifiers) there is NO WAY that a single speaker in that Mackie can handle the 2000 watts that amp can put out. NO WAY. The best speakers can handle around 500 watts.

 

You're up there competing against two guitars, bass guitar, and a drum kit. There is no way that a single speaker is adequate for keyboards in that environment, and I know this from YEARS of gigging.

 

I started gigging before class D amplifiers were available. Back then, class AB amplifiers ruled. In today's professional PA and monitor world they STILL rule. Yes they are heavier. You may not want to haul around that "heavy stuff", but I still use class AB because they have almost never let me down.

 

Choice of drivers: I don't much faith in the stock drivers in cabinets anymore. I have a Peavey 2x15 cabinet that I used for bass guitar or for a subwoofer when I need a biamped keyboard rig for the stage. The stock Peavey Scorpion speakers kept blowing - even when I wasn't pushing them that hard! After too many times of getting them reconed, I replaced them with heavy duty EV drivers.

 

Probably the one exception are my Bose 802 speakers. I bought a used 802 in the late 80s and found it to be a great stage monitor for keyboards. Don't let the tiny speakers deceive you; combined with the 802c controller (mandatory with 802 speakers) these puppies can deliver on stage. Since they're modular you can stack multiple 802s - a pair of 802s has no trouble competing with a guitar player's 100 watt amplifier. When I am playing LH bass synth I combine the 802s with the Peavey 2x15 to comprise a biamp rig. While the 802s are great, they don't do everything.

 

802s are still made as series IV; I haven't tried them, but they would be more promising for stage work.

 

Moe suggested the Moog Synamp and he is not kidding. You don't need those huge speakers though. I bought a used Moog Synamp and it has been an excellent stage system. Again, class AB amplifier. It is a heavy bastard but it has never let me down. I don't mind lifting heavy gear as they have kept me in shape and I am still strong at 54. The Synamp can be configured as biamp so it was ideal for my Bose/Peavey setup. It evens works great for electronic drums, and they are more demanding than keyboards.

 

Seems there is a major gap in the market place when a guitarist can purchase a 100w tube combo for under $300 bucks and a keyboardist has to purchase a $1200 high end pa wedge as Jim suggests just to keep up.

 

It's not a "gap". It's the demand of your instrument. A guitar amp only needs to amplify a limited bandwidth and they don't need much dynamic range. Keyboards need full bandwidth and dynamic range so the demands on the amp are much higher. Building guitar amps and keyboard amps are worlds apart. Keyboard amps cost more because they require more parts and larger components. That's the nature of the design.

 

I would highly recommend consulting with someone other than who you are buying your speakers from. Your professional needs often conflict with the salesperson, whose greater concern is the commission from high quantity but unreliable products they keep pushing on customers. You will not find stuff like the Bose 802s in stores, very seldom in catalogs or online sellers like MF.

 

Be VERY wary of online reviews as they may be deceptive, negative reviews may be from "user error" (musicians who don't know how to use them or bought them for the wrong application), or posters are actually dealers or distributers impersonating satisfied customers.

[Chewey]

Cool. Thx for the wise words. So before I throw another stash of benjamins at this... in the meantime, will any limiter do... as a patch.... or are the potential oscillations that grollins mentioned outside of the scope of a limiter? I the short term I need this gear to cover my butt. Jim mentioned a filter... will a simple pedal filter that rolls off some highs and lows help? Seems that would cut tone though. Jeez, those other guys have it so easy.

[The Real MC]

A limiter is not a solution.

 

A filter that rolls off the lows may help, but it will not solve the problem with dynamics.

 

Yes those other guys have it so easy. Nature of the beast.

[mate stubb]

Chewey, tell us a bit more about how you are using the Moog. Are you running bass lines, subsonic to supersonic sweeps, lead lines, what?

[Chewey]

Maybe time for in ears?

[Chewey]

Moog gets used for some leads, some big tom sawyer'ish bass drops, efx's like wind and reso bleeps that sweep across the filter spread, some dedicated pedal like bass sounds. Its all over the map.

[GRollins]

Limiters will not help oscillation problems.

 

I'm not a big fan of Class D amps, either. Again, this could be an entire thread on its own, but in the process of designing and building Class D amplifiers, they tend to put minuscule power supplies in them, both for reasons of cost and weight. Small power supplies collapse under load. As far as you're concerned, they have no dynamics compared to a "real" amp, like a Class AB. This also limits your perceived low end. So what do you do? You turn it up to try to get your missing low end and dynamics. Which means you're that much closer to clipping. Note also that collapsing power supplies mean that Class D amps don't deliver anything like the claimed wattage in the real world.

 

Case in point. I've got an ancient Hafler P500 (Class AB, two channels, 250W each) which will absolutely, positively, completely crush Class D amps claiming far higher power ratings. Why? It has a halfway decent power supply, amongst other things. No, Class AB, in and of itself, is not a guarantee of better sound quality. There are scads of other factors involved. If you put a puny power supply on a Class AB amp, it's going to sound like crap, too. It's the sum of the parts, not any one of them alone.

 

Grey

[mate stubb]

I just looked at a picture of the Mackie. It's a tiny box, barely large enough to hold the 12" speaker it contains.

 

That means that it will not develop low end naturally from moving air inside a cabinet and port sized and tuned to the speaker. This is not particularly unusual in powered speakers, but it does mean that the low end has to be artificially EQed into it with the dsp.

 

Mackie is not particularly renowned for the quality of its drivers or its dsp algorithms, so it may just be getting asked to do too much.

 

You say you need to get by for awhile - do you have another amp/speaker you can add to the Mackie to shoulder some of the load?

[Chewey]

Ill have to lean on the mackie or kustom rig for now. I have been pleased with it so far. I know it looks tiny, but it is just as loud if not louder than the qsc k12 that I had. But that smell preceded the failures in the other speakers... sigh. I do have the Carvin scx1115 cabinet still, I suppose I could load that up with some beefy drivers get a class a/b amp down the road or try and find some of those bose 802's. Anyways, thx for the advice everybody. Cheers.

[J. Dan]

If you believe specs, the Mackie has a max SPL of 128 while the K12.2 has a max SPL of 132. That's a pretty significant difference.

[Chewey]

Must have been perceived.... or I'm just bitter that it died on me.

 

How about the Carvin TS100 tube power amp, class ab 100w bridged, 50w stereo... looks like it would be a pretty sweet, not a bad price either.

[J. Dan]

Maybe I'm confused. The Mackie is powered. Are you talking about trying to bypass the internal amp or are you talking about using the car in amp with a different speaker?

 

I think there is some misunderstanding on tube amps and amp class especially mixed with guitar vs keyboard. While it may be true that the Class D amp in the Mackie doesn't measure up, there isn't anything inherently worse about class D than Class AB. If shortcuts are not taken and it is designed properly, a class D amp can supply plenty of power. Some of the earlier models gave them a bad name and the shortcuts used in order to keep the price down end up sacrificing performance, but that as nothing to do with class D. A poorly designed class AB amp will suck as well,

 

Guitar amps are designed to distort and pass a much narrower band, that's why less wattage is needed, and tubes have more pleasing distortion. You are playing keyboards, not guitar, and will not be running it to distortion, so a 100w tube amp won't give you the volume of a guitar amp.

 

The spec to look at is Max SPL.

[Chewey]

Thx Dan. The consideration was to build up a cabinet with appropriate drivers in it and loose the mackie.