Best Cabling Option?

[onemanband]

Hi,

Just got a new PA System 2 x RCF Art310A plus 1 x dB Technologies Sub12 (all active).

 

Which do you reckon would be the best cabling option (working in mono):

 

1. To feed both independent inputs of the dB sub bass from the L/R mixer outs and then feed the two 310's from the two outputs of the sub bass unit, or

 

2. (my preferred method) To feed the sub bass from the right mixer out and the two 310's (linked) from the left mixer out, giving me independent control of how much sub bass I want (by using either/or pan and level controls).

[SoLiEn]

Hi,

Just got a new PA System 2 x RCF Art310A plus 1 x dB Technologies Sub12 (all active).

 

Which do you reckon would be the best cabling option (working in mono):

 

1. To feed both independent inputs of the dB sub bass from the L/R mixer outs and then feed the two 310's from the two outputs of the sub bass unit, or

 

2. (my preferred method) To feed the sub bass from the right mixer out and the two 310's (linked) from the left mixer out, giving me independent control of how much sub bass I want (by using either/or pan and level controls).

 

 

Whats the Mixer?

 

Personally I would do option 1.

 

If you at any point play music through the system off cd,md,ipod etc, sometimes the tracks are properly mixed in stereo ,so you would get a crappy sounding track..

 

IF the mixer has a mono out and you really want seperate control of the sub, then I would suggest MIX L + MIX R feeding their respetive speakers and the mixer mono feeding the sub.

 

HTH

 

Dan

[Bobbsy]

The other thing to consider is that there are crossover outputs on the sub which filter off the sub frequencies making the ART speakers a bit more efficient because they're not wasting energy on the frequencies covered by the sub. Whether this is a real life issue, only your ears can tell you--but it's another factor for you to look at (er, listen to).

[onemanband]

Hi you two, thanks for the replies, I really appreciate your advice and comments!!

 

The mixer is my good old, trusty, Soundcraft EFX8

 

Dan, yes I do have a mono out and hadn't thought of that one; excellent idea!!

but.............

The reason I suggested the second option, is that I have a mic'd up kick drum that draws a lot of power and I am sure that would overdrive the RCF's and not be good for the HF tweeters, (It damaged the HF's in my old system) !!

Cabling my "preferred" way I thought I could pan the whole kick drum signal to the sub bass, hopefully getting a real "kick drum thump", without risking overdriving the tops. (I can also cut/boost other channel highs and lows by panning accordingly), and then adjust the whole overall sound with the master faders, does that make sense??

The mono/stereo thing isn't really a problem as I only work in mono and very, very, rarely play stereo tracks.

 

All advice and comments greatly appreciated!!

Cheers....Brian.

 

.

[SoLiEn]

Personally Brian, I still would run stereo l + r as nature intended and sub of the mono. as Bobbsy said, let the crossover do its job to make the cabs as efficient as possible, I do see your reasoning regarding damaging, but I wonder if this could be avoided with proper use of a graphic eq to tame the frequencies that the cab doesnt agree with....

 

I happen to have a pair of the ART310 at work and use them relatively regulary, not bad little speakers for the price, but I do find they need the high knocked back a little as they are 'bright'.

 

Dan

[david.elsbury]

The other, more standard way, to do what you want, is to use a spare post-fader aux send (if you have one of course).

 

This allows you to route just the kick and other sources that may benefit from the extra low frequencies to the sub.

HTH

David

 

Edit: It appears that this may not be an option with your current desk.

[BigKev]

I installed a very similar system in a bar about a month ago!

Same sub, same desk (a new efx8) but with pasive Art310's with a qsc amp. Quite uncanny.

 

Anyway, upon testing it I found the tops produced an unexpected amount of low end for a 10" speaker. I wouldn't consider running them full range with a sub.

 

Best option I found was to route L+R from the desk to sub and use the sub outs to drive the tops (as per your option 1).

Then all there is to do is to balance the tops and bottoms with the sensitivity pots on the speakers.

 

As david says the passive versions do need a bit of taming I found but I can't comment on the active boxes.

[onemanband]

Thanks for the additional comments guys.

 

Then all there is to do is to balance the tops and bottoms with the sensitivity pots on the speakers.

Kev,

I was always led to believe that power amps (in this case inside the speaker enclosures), should be run flat out, gains set to maximum, with system levels being set at the mixer; I'm sure this is the case, but I'm ready to be corrected!

 

I think I shall simply try each of the three options, and see which produces the best result to my ear (sound is of course, subjective).

If anyone's interested, I'll post my findings.

 

Thanks for all the advice, greatly appreciated.........................Brian.

[Bobbsy]

Kev,

I was always led to believe that power amps (in this case inside the speaker enclosures), should be run flat out, gains set to maximum, with system levels being set at the mixer; I'm sure this is the case, but I'm ready to be corrected!

 

Actually, there's no hard and fast rule on this. Certainly, depending on circumstances, the "run your amps flat out" can work much of the time but it depends on the rest of the system.

 

The main thing to remember is that the amplifier section provides a fixed amount of gain. You put in a signal at a certain level and the amp adds 20 or 30 (or whatever) dB of gain to the signal and sends this out to the speaker drivers. The level controls on your amps (in the speakers) aren't adjusting the amps themselves; they're just attenuating the level of the input signal.

 

So, basically, I treat the input controls on amps/speakers as just another part of the gain staging of the system. There's little point in running the amps flat out if, to make the system sound good in a small space, you have to keep the master fader on your mixer at a super low (i.e. in the non linear section of the range) level. It's far better to set things so the speakers sound good (and have plenty of overhead available) when your meters (assuming analogue here...the digital dbFS scale is different) are at about 0dB. Ideally, this will also mean that the speakers won't get to clipping until the mixer meters are also getting worryingly high. The main thing you don't want is a situation where the amps are turned down so far that the rest of the system clips long before the speakers. Speaker drivers and high amplitude square waves are a bad combination!

 

The above is purely technical aspect but you can also add in getting an appropriate SPL for the venue you're in. I do mainly theatre and tend to set the input attenuation on the amps so "normal" levels are around or just below the zero point on my meters, giving me 18 to 21dB of headroom for crescendos or loud sound effects...and the ability to pull things back for the quiet bits but still be in the useful range of the faders.

 

So, there's no reason for you not to do small tweaks on the input attenuation of your active speakers to achieve a good balance between subs and tops. As long as you don't turn things down so far that the mixer clips long before the speakers, you'll be fine.

[mackerr]

The main thing to remember is that the amplifier section provides a fixed amount of gain. You put in a signal at a certain level and the amp adds 20 or 30 (or whatever) dB of gain to the signal and sends this out to the speaker drivers. The level controls on your amps (in the speakers) aren't adjusting the amps themselves; they're just attenuating the level of the input signal.

 

This is really a matter of semantics. What is the amp? At one time, the "volume control" was a passive attenuator at the input to the amp. Lots of amps today have an active gain stage between the input and the power devices. This gain stage can have its input overdriven if the gain is down too far and you need to sent too much level to get the sound level you want.

 

Bobbsy's comments are on the money as far as what can affect your choice of how you set the gain of your external amps, or the amps built into your speakers.

 

Mac

[Bobbsy]

 

This is really a matter of semantics. What is the amp? At one time, the "volume control" was a passive attenuator at the input to the amp. Lots of amps today have an active gain stage between the input and the power devices. This gain stage can have its input overdriven if the gain is down too far and you need to sent too much level to get the sound level you want.

 

 

True. The point I was trying to make is that, even turned down, the amplifiers are still able to put out their maximum rated power. It just takes a hotter input signal to achieve this. I probably should have spelled that out more clearly. The issue is that you need a good match of levels throughout the system, rather than having to have artificially low levels on the output of the mixer because the input to the amps are cranked up all the way--just as you don't want the amps turned down forcing you to drive your mixer to high (and into clipping) to get the levels you want out of the amp.

[BigKev]

Amplifier attenuators, or preamps (depending on model etc) are there to match the level of input to the optimum working level of the amplifier.

 

In the O.P.'s case, if the desk's max output is +18dbv and the amplifier's sensitivity is also +18dbv then running the amplifier flat out would be the logical option.

But if the amplifier's sensitivity is +4dbv then in this case then you should apply a -16bdv cut on the amp input pots to give you the full dynamic range of the desk.

Google "gain structure" for further reading as its a well covered subject.

 

For the system in question what I would do it the following:

 

1. Turn down all input gain pots on the active cabs.

2. Run a program signal through the desk to its max output before either clipping or max output you will drive it to.

3. Turn up the tops and bins individually until they are just below compression or peak light (don't turn them up until they distort!).

4. Listen to the overall mix of the tops and bottoms together at this volume and decide which ones to turn down in order to get a balanced sound.

 

Setting up this way (and providing nobody else moves the inputs on the amps) will ensure that, whithin reason, nobody should be able to overdrive the speakers should other folk use it unsupervised.

 

I have echoed some of the other comments here but its all good info.

 

 

[onemanband]

Hi,

 

Well, I have considered all the evidence, and spent all day trying the different options.

 

I have to honestly say that (to my ears), my original option of driving the sub bass and tops separately through the left and right channels of the mixer provided me with the best control over the system, produced the best sound, and no fear that I will fry the HF compression driver with low frequencies from the kick drum (panned toward the sub bass channel).

 

Thanks for all the input (pun intended http://www.blue-room.org.uk/public/style_emoticons/default/wink.gif) and advice, I've learned a lot!!

 

Cheers............Brian

[BigKev]

Its good that you found an option that both sounds good and works for you to control. Thats the important thing.

 

However, sending a kick drum / bass guitar or any signal with a lot of bass in to a full range cabinet with crossover will not fry the HF driver.

Unless of course the signal is clipping somewhere e.g. channel, master, amp, speaker. But this could happen with any signal.

 

Its not my intention to confuse so sorry if I do. I would just like to point out that what destroyed your HF's was due to one or several signal spikes, causing distortion in the chain somewhere.

 

If you don't want damaged or broken drivers just keep an eye and an ear out to make sure you arent overdriving the system.

[onemanband]

Kev,

 

Please don't apologise, I am grateful for all the advice on the thread, that I found interesting and informative (I must admit though, a bit confusing too http://www.blue-room.org.uk/public/style_emoticons/default/smile.gif).

 

I have a routine for setting my system, input gains first, main mixer outs second, making sure I don't get any clipping anywhere along the signal chain and then trying to avoid volume levels that will clip the speaker amps; this the correct procedure is it not??

 

Please don't think I'm a volume junkie and blow HF drivers regularly, it only happened once, but I just want to avoid doing it again!! http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif