Stage issues. Help!

Re: Stage issues. Help!

jonathan betts said:
I'm using the crossover in the Itech. This is why I don't think it will work.
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You can easily do aux subs with the Itech. Just like Jay said- use channel 1 for the subs, channel 2 for the mains (or opposite), and adjust as necessary.

If you send me your current preset file, I can modify it for you.

Also, if you're not using both effects, these are Post aux sends, and they probably have a direct output on the back (bypassing the internal processor). One of these could drive your subs while the mains come off the regular man bus.
 
Re: Stage issues. Help!

Jay Barracato said:
Sure it will, the Itech will give you the control you need.

Just think sequentially. Currently you have a single full range signal going into the Itech, which is then split to drive your tops and subs. All you are doing is moving the point at which the signal is split upstream from the Itech to your mixer.

eidt- all the aux or group feed sub is doing is removing things from the signal being sent to the subs that do not need to be there.
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So, set the amp up in stereo. Run from (L channel mixer to channel 1 on amp(tops) / Run from (R channel mixer to channel 2 on amp subs)

Pan everything not going to subs left and pan everything going to subs right.


Is this correct?
 
Re: Stage issues. Help!

jonathan betts said:
So, set the amp up in stereo. Run from (L channel mixer to channel 1 on amp(tops) / Run from (R channel mixer to channel 2 on amp subs)

Pan everything not going to subs left and pan everything going to subs right.


Is this correct?
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Nothing is going JUST to the subs, that is why you leave those channels at center, so the signal is sent both to the tops and the subs.
 
Re: Stage issues. Help!

Jay Barracato said:
Nothing is going JUST to the subs, that is why you leave those channels at center, so the signal is sent both to the tops and the subs.
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Also note, due to the way some pan laws work, channels that are panned center may be quieter in the mains than ones that are hard-panned to one side. So if you have two identical tom channels, and one is in the subs and the other isn't, the one in the subs may have have the fader higher to get the same loudness out of the mains.

This is more of an FYI than a problem though.
 
Re: Stage issues. Help!

Jay Barracato said:
Nothing is going JUST to the subs, that is why you leave those channels at center, so the signal is sent both to the tops and the subs.
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Oops! I'm being a little dense. I will give this a try. Should I put the guitar, horns and congas through the subs?


Here is some more info regarding the Itech 6000 setup ( this setup could probably be made more efficient) I have a feeling the crossover should be closer to 100hz


MRX 515's (2)

Input sensitivity set to 32db attenuators at 0
-3 db bandpass gain
RMS limiter set at 800
Peak limiter set at 100v

Crossover:

HP LR 24 85hz
low pass is not engaged

SRX 718(2)

Input sensitivity set to 32db attenuators at 0
+6 bandpass gain
RMS limiter 1600w
Peak limiter 115v

Crossover:

HP BUT 18 31hz
LP LR 24 85hz

Silas, any recommendations you have would be great seeing that I'm a complete newbie with this amp. Thanks for your help everyone! I'm sure I will have more questions.
 
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Re: Stage issues. Help!

The 718s don't like to be crossed any higher than 80Hz or so. Usually, things sound good when those subs are low passed at 80, and the tops high passed at 100. You'll need to do some system aligning to do this, or put a tad of delay on the tops. Bennett might know the 'average' delay times better.

I would NEVER do any bandpass cutting with an Itech. Make the subs +9 and the tops at 0.

The RMS limiter on the sub channel is doing nothing. Might want to make it like 1000 watts @ 4 ohms, or not bother.
 
Re: Stage issues. Help!

Silas Pradetto said:
The 718s don't like to be crossed any higher than 80Hz or so. Usually, things sound good when those subs are low passed at 80, and the tops high passed at 100. You'll need to do some system aligning to do this, or put a tad of delay on the tops. Bennett might know the 'average' delay times better.

I would NEVER do any bandpass cutting with an Itech. Make the subs +9 and the tops at 0.

The RMS limiter on the sub channel is doing nothing. Might want to make it like 1000 watts @ 4 ohms, or not bother.
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Why is this? I thought setting the rms for 1600w 4 ohms would be ok since they are rated at 800rms 8 ohms.


Will adding that much gain to the subs increase voltage, and possibly make my inputs and outputs clip sooner?
 
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Re: Stage issues. Help!

Jonathan Betts said:
Why is this? I thought setting the rms for 1600w 4 ohms would be ok since they are rated at 800rms 8 ohms.


Will adding that much gain to the subs increase voltage, and possibly make my inputs and outputs clip sooner?
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Gain has no effect on ultimate output voltage, as long as it's above zero. It simply means you need more input voltage to get to a specified output voltage.

It will actually make your inputs clip LESS soon, which is what you want. Itech inputs are notorious for being overdrivable.

The outputs will still clip at whatever the amp determines is clipping. It won't be louder or quieter.

JBL specifies the RMS power at some amount of power compression. In most cases, you can get more out of the speaker with less power, because there is less power compression at lower power levels. Eventually, with increasing of additional power, the speaker will stop getting louder due to heat.
 
Re: Stage issues. Help!

Nice article Bennett. I will have to read it about 20 times before it sinks in. This stuff is way over my head. I am really trying to make an effort to learn this language. I hope my questions are not bothersome.

Obviously I have an amplifier that is plenty capable of destroying my speakers. If this was your system what would you set your peak and rms limiters at, or would you even use them.

Also Silas mentioned something about delay's in a previous post. What are your thoughts on that?
 
Re: Stage issues. Help!

Jonathan,

Usually I set peak "limiters" by using an amplifier that can't provide more peak power than the driver can take. With pro drivers this is usually pretty easy, since even a compression driver can take several hundred watts peak.

Almost any amp can burn up almost any driver nowadays with long term power, so I like to set my RMS limiters at 1/2 the driver's rated "continuous" power. If you're used to playing a numbers game, it may seem very strange to be limiting a 15" woofer at 400 watts or so, but try it. Your rig will be very hard to blow up, you will avoid power compression, and your drivers will thank you.

The peak power limiting is pretty hard to argue.
The RMS, we could debate back and forth all day. For someone in your situation, I absolutely recommend using 1/2 the lowest power spec of the driver. If you're laying into that limiter you need more rig, and on the gigs where you need more rig and you're laying into that limiter you'll be real glad it's there.

The 3dB in between conservative limiting and bleeding edge performance is why I get paid to do what I do.
 
Re: Stage issues. Help!

I will set my RMS limiters to 200w per driver on the tops and 400w per driver on the subs. I hope I have not already caused damage to my cabinets.
 
Re: Stage issues. Help!

Jonathan Betts said:
I will set my RMS limiters to 200w per driver on the tops and 400w per driver on the subs. I hope I have not already caused damage to my cabinets.
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You haven't. While the additional power won't likely help get louder, it won't hurt, as long as it's within the limits of the drivers. Since you set the limiters to the manufacturer recommendations, you are probably fine.
 
Re: Stage issues. Help!

I'm still confused as to where I should set my crossover. I have no experience with setting electronic delays but have some experience with physical alignment.
 
Re: Stage issues. Help!

Jonathan Betts said:
I'm still confused as to where I should set my crossover. I have no experience with setting electronic delays but have some experience with physical alignment.
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You should set it where it sounds good. If there's a question, play with it at a gig until it sounds right. Once it sounds right, you can probably get it even better by measuring the phase alignment with a program like Smaart, and give it the final touches with delay.
 
Re: Stage issues. Help!

Silas Pradetto said:
The 718s don't like to be crossed any higher than 80Hz or so. Usually, things sound good when those subs are low passed at 80, and the tops high passed at 100. You'll need to do some system aligning to do this, or put a tad of delay on the tops. Bennett might know the 'average' delay times better.

I would NEVER do any bandpass cutting with an Itech. Make the subs +9 and the tops at 0.

The RMS limiter on the sub channel is doing nothing. Might want to make it like 1000 watts @ 4 ohms, or not bother.
Click to expand...


Will adding gain in the bandpass change the frequency of the crossover? I was reading that you should not make changes to gain in the crossover when using aux fed subs.
 
Re: Stage issues. Help!

Indeed it will, Jonathan. This is because no crossover has infinite slope. You can demonstrate this by holding your hands flat so they touch at your fingers and form a V, your left hand is the low pass response of your subwoofers and your right hand is the high pass response of your mains. Where they connect is the acoustic crossover frequency. If you raise your left hand up (add gain) and imagine the response continuing to connect, you can see that the effective crossover point rises up your right hand. The way to compensate is to also move your left hand left (lower the crossover point in frequency) you can see how it is possible to get them to match up again.

This is standard practice, since most people like a fairly hot bass environment. The problem is that now the two crossover points are at different frequency, and they experience different phase shift (read: delay). This means you will have to delay your mains to get them to line up in time again. You can probably do this by ear, 1ms at a time. You will probably end up with 2-4 ms of delay, maybe 6, but if you find you want more you have probably gone too far.
 
Re: Stage issues. Help!

So if i were to start off with a LP of 80 hz on the sub and 100hz HP on the tops and then added 7db gain to the sub bandpass what frequency would my LP end up being?
 
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Re: Stage issues. Help!

If I knew, I would tell you! That assumes several things: Your subwoofers and mains are equalized flat, they are equal gain to begin with, they have the same acoustic crossover slope (unlikely), they are time aligned (maybe, to where?).
 
Re: Stage issues. Help!

Jonathan:
The variables involved and the issues of integration that are the basis of your questions are covered very well by Bob McCarthy in
Sound systems: design and optimization
page 87 Acoustic Crossovers
 
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