Using 1 amp in a 3 or 4 way setup

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JM, thanks again for the advice. From what I've read I understand the 2 main driver damage causes are:
-Overheating from to much power.
-Over excursion over too low frequencies.

I'll be taking your advice on getting a weaker amp for the compression driver. But I still don't understand why you think the mids or the subwoofers are in such great risk.

2 channels bridged @ 4 ohm will output around 1,8kW for 2 drivers rated 1,5kW RMS combined. Seeing that people usually recommend having anywhere from 1,5x to 2x power on the amp as the RMS of the driver, 150W headroom per driver is well bellow that recommendation. I'd think it's pretty conservative isn't it?
well, if "people" recommend that, they can´t be wrong, can they?;)
truth is , that´s a poor quote taken out of context.
It applies to Hi Fi home systems, full range, which means passive crossovers, listening to, say, Classical Music, the favourite type of 50´s Hi Fi fans.
Clipping sent all distortion products straight into the tweeter ... easily 10X what it could handle, and quickly killed it.
Simplest solution is to have a powerful amplifier so it NEVER clips, but of course use it at an average 10% of its rated power.
If you will listen to Classical Music at home, use your 900W per speaker amp at no more than 90W average power and everything will be fine.
Oh, but you are a DJ, aren´t you?
Then forget that advice you read which does not apply to you at all.

The same for the mids, powering 2x12" rated 800W RMS with a 600W @ 4 ohm channel, seems pretty conservative as well, doesn't it?
read what I wrote about he woofers ... same thing.
On to the limiters subject. I hadn't really thought about it. I was planning on hooking DJ mixer to active crossover to amps.
Just get those limiters and set them as described.
I just thought of not letting the clip indicator (0dBFS Limit indicator per channel according to manual) light up frequently.
Famous last words.
Just get those limiters and set them as described.

Though I have a big question here as I read that the input signal from the mixer could come clipped into the amp and in that case the amps clip indicator wouldn't light up. Anyone any advise on how to avoid this?
You will hear the dirty/distorted signal ... I hope.
Not too sure you will even notice that in the middle of a hot party.

I suspect that instead of Classical Music at a Senior retirement home you will play something similar to:
https://soundcloud.com/dj-craios-colombia/overdosis-trip-001-by-dj-craios-2k17-free-download

or maybe some Tropi music.
In any case your unlimited overpowered speakers won´t last much.

You can´t keep an eye on the Peak Led when surrounded by:
normal_chicas_aguila_2.jpg
 
What's with all the ranting? Op is asking reasonable questions and eager to learn. No offense, some words of warning are ok to keep less experienced users aware of the dangers. But your posts come across as quite sarcastic and patronizing to be honest.
 
On to the limiters subject. I hadn't really thought about it. I was planning on hooking DJ mixer to active crossover to amps.

I just thought of not letting the clip indicator (0dBFS Limit indicator per channel according to manual) light up frequently. Though I have a big question here as I read that the input signal from the mixer could come clipped into the amp and in that case the amps clip indicator wouldn't light up. Anyone any advise on how to avoid this?

Please let me know what you think, really appreciate all the input I've been getting here!

I would suggest you experiment with your system at low volumes to get a better understanding. Connect everything as you would for an event, but keep your amplifiers turned down very low so that it doesnt become too loud. Play some music, and experiment with the different parta of the system. Turn up channel input gain until pfl indicator goes red, and listen on your headphone when it starts to distort, how it sounds. Can you notice the distortion? Turn up the master channel and run it to maximum until it becomes red. watch the input of your dcx, does it clip? How does that sound? Can you notice it? etc......
Then play with the limiters in the dcx.....


But while doing all this, use common sense, protect your equipment and ears. The purpose is to get a feel for how your equipment works, when does it distort, how to set gain structure etc. It's very important that you recognize distortion, and know the limits of each component. In real life application this will help you avoid disasters and broken loudspeakers. When you start to properly set up your system, you obviously want to set your amps at unity gain or maximum, and avoid distortion or clipping in any part of your system.
 
"Clipping sent all distortion products straight into the tweeter ..."

Pull the other leg !!!


Two things damage speakers:

Mechanical damage (from too much excursion).

Too much average power.

(notice that clipping is not one of those two things?)

Compression raises average power, and thus burns out drivers.

---------------------------------------------------------------------------------------

Clipping blows out drivers, not because of the clipping, but because of the increased average power in the program material during the time when the amplifier is not clipped.
 
"Clipping sent all distortion products straight into the tweeter ..."

Pull the other leg !!!


Two things damage speakers:

Mechanical damage (from too much excursion).

Too much average power.

(notice that clipping is not one of those two things?)

Compression raises average power, and thus burns out drivers.

---------------------------------------------------------------------------------------

Clipping blows out drivers, not because of the clipping, but because of the increased average power in the program material during the time when the amplifier is not clipped.
I'm going to tske up your challenge. and try pulling your other leg.

Take a 1kHz sinewave that is just short of clipping while delivering 100W (40Vpk 5Apk) from a 100W amplifier. Pass that to a crossover and thence to two drivers with a crossover set to ~2kHz. The lower driver will receive most of the 5Apk. The upper driver might see -12dB to -20dB of that signal, i.e. somewhere between 1.2Apk and 0.5Apk
Now massively increase the input so that the output becomes a 1kHz squarewave. The total power in the 1kHz square wave with a 40Bpk level is 200W
The 1kHz sinewave portion of that square wave is still 40Vpk and 5Apk equivalent to 100W and that is still delivered via the 2kHz crossover to the lower driver.
The higher harmonics of the squarewave starting from the 3rd and all the odds above that get delivered to the upper driver. The total power of these odd harmonic frequencies is that other 100W (for the 200W total).
The upper driver is receiving 100W continuously. This is very different from the 1W (-20dB) to 25W (-12dB) of transient signal that the upper driver is designed to handle without damage.
 
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"And you believe that?"

You are an intelligent guy, what part of that didn't you understand?

The article was peer reviewed in the JAES, visit your library and read the discussion (it's too expensive for non-members otherwise).

"Clipping increases the average power,"

The input overdrive that produces clipping increases the average power during the un-clipped portion of the program material, this increase in average power is what burns out the HF driver, not the clipping per se.
 
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You would also burn out the tweeter if you used a larger amplifier not clipping at all producing the same average power. It would sound a lot louder, because of the increased dynamics. 10 or 20 dB above the speaker's nominal design limit is too much, regardless of how you get there.

If you used an tweeter which could handle an average power level of say, half or more of the RMS rating of the amplifier, you would have a hard time burning out the tweeter, regardless of how much you clip it. Not as hard as it sounds - a 2 inch CD with 10dB of pad to match a typical 15, used on a 500 watt amp. Of course you need 200 watts worth of resistor in the L-pad to keep from starting a fire. And the 15 will need a 4 inch voice coil to handle the average power as well. That kind of speaker combo is what you need for DJ gigs where you are expected to 'blast' it. The same speaker could be used with a MUCH bigger amplifier, if you kept the levels tame.
 
If you used an tweeter which could handle an average power level of say, half or more of the RMS rating of the amplifier
The OP is talking a 400 or 500W RMS into 8 ohms amplifier; for your suggestion to be possible the driver voice coil should need to handle some 250W RMS.

Pity those don´t exist :rolleyes:
(Well, maybe in a NASA lab or similar, while here we are trying to help a real world DJ who just bought a 6000W amplifier and is trying to build a real, usable system)

One practical solution would be to lower power amp rating to, say, 60W RMS and then proceed to limit it further down to some 25/30W RMS ... what a regular driver voice coil can realistically handle.

Not surprisingly, that is what I suggested :rolleyes:

As for misquoting poorly understood JBL, Rane or any other serious PA components manufacturer, read it again until you understand what they mean and the real worls implications.

FWIW only Andrew T provided real world calculations, most others calculate nothing, just try to back their statements using the "principle of Authority" ... fully out of context of course.
And NOT helping the OP at all.

Changing subjects: those are real beautiful Colombian girls :p
And beautiful girls in any Country are often attracted by the DJ ..... just don´t ask me how I know that :cool:
 

ICG

Disabled Account
Joined 2007
I could say a lot about how much power is needed (or not) but I have the feeling that's futile anyway. Why? It looks like it's a theoretical and not an actual setup and that means noone knows how much power is needed or how much is really too much. So let's look at it from another perspective.

For a PA you want

  1. reliability
  2. flexibility
  3. quick and safe setup and troubleshooting

If you ever got a problem with the amp, you're losing one side of the PA. Well, every amp can fail, what's the problem with that? It's build up 'vertically'. If you change one amp, you have to change the setup of the controller and that means you'll have different settings right and left because the power does not actually scale the same with the impedance on every amp. That may be because of the maximum rail voltage (-> clipping), power supply limits or simply bad design. So if you have to replace an amp in this setup, you need to change the whole setup, limiters and level adjustments. That takes much more time and a quick change isn't possible. And you have to keep an eye on the amps for clipping or other things. I don't even go further onto how different amps sound different (especally class D and tweeters).

For the points above: This setup got none of it. -> This setup is BAD!

Much better: Horizontal build. One amp for the tweeters, one for the mids (and so on). That way, if one amp fails, you replace it and only have to deal with the level and limiter setup of ONE amp and don't need a different one for right and left! Which also means, you have much less chances to 'forget' a setting for one side or have to go over ALL settings for all channels on two sides. A hot swap can be a thing of a minute instead of 15 mins (or more? depending on the controller). Or you could just swap the sub amp to a more potent one if you need much more power & more subs because of an open air or much larger location. Or generally amp upgrade, it will be much easier if you can swap the one which got the best power and sound for the right f-range. Or just get a rental replacement amp that sounds right.

Ofcourse you can also use a multi-channel amp for a 'horizontal' build but planning it vertically is not a good idea. Really.
 

ICG

Disabled Account
Joined 2007
I disagree entirely.

I'd rather lose one side than all the mids. To most people, only running one side will mean it's quieter, while losing all the mids/bass sounds terrible.

You don't lose the mids because you always have at least one amp more with you (monitor) which you can use for it, just use mono for the mids and monitor. Or repurpose one ch. of the sub amp. So with a liiiitle bit flexibility you get your gear working again completely with much less 'loss'. Naturally, that makes your argument fade away quite quickly.
 
Hi,
I’m reviving this thread as I’ve come across a couple of additional questions:

-Can anyone recommend some paper or text on how to set up a compressor with the purpose of protecting the drivers?
I’ve found plenty on how to use them for mixing when recording or for compressing an instrument channel. But I’m planning on using one channel for bass, one for mids and one for HF and I’m not really sure on how to set the thresholds.

-Right now I have only bought the bass drivers. I already have the crossover and the compressor. So I was wondering if I could connect them to a regular home use stereo system through the aux input to try them out and hear their effect. So the setup would be:
o DJ Mixer. OUT: 2 RCA
o Active Crossover. IN: 1 XLR OUT: 1 XLR. (on the mids so I have a wide range to test)
o Compressor/Limiter. IN: 1 XLR, OUT: 1 XLR
o Home stereo system: IN: 2 RCA.

I’m going from stereo (mixer with 2 RCA) to Mono (crossover and compressor, 1 XLR) back to stereo (aux input on home system).

Is there anything wrong with trying this? Can it be done? It's just to try and get familiar with the effects of processing before using it with the actual drivers and amps.

Thanks.
 
You don't lose the mids because you always have at least one amp more with you (monitor) which you can use for it, just use mono for the mids and monitor. Or repurpose one ch. of the sub amp. So with a liiiitle bit flexibility you get your gear working again completely with much less 'loss'. Naturally, that makes your argument fade away quite quickly.

Not really.

Even if you can re-patch things in a minute, you've still lost the midband for that minute. I'd rather lose one side and keep things intelligible rather than all of the bass/mids/highs disappearing.


To the OP, bypass the crossover if you want to play with adding a compressor to your home HiFi. Ideally, you want both peak and rms limiters on each crossover output so that you can control how much power each band gets seperately.

Chris
 
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