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Author Topic: Using the 31-band main EQ as high pass filter  (Read 2131 times)

Andrew Yakin

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Using the 31-band main EQ as high pass filter
« on: September 28, 2014, 12:53:49 pm »

Greetings to all,

Recently, our church has acquired a pair of Behringer active sub woofer (EUROLIVE B1800D-PRO) however the church leaders are not convinced to get a crossover unit yet. Meanwhile, the existing system only consist of Yamaha mixer, one L-R 31-band EQ, and an amplifier which powers a pair of full-range speakers for FOH.

My question is, since the Behringer subs already have built-in crossover for input (70-150Hz), can I use the main 31-band EQ as high pass filter (ie bringing all sliders bellow 125Hz all the way down) as shown in the picture? Will it cause damage to the EQ or affect the sound coming out from the full-range FOH? The source for the subs are drawn from subgroup outs and are independent to the main stereo out

thanks, looking forward to your helps and advice :)

Andrew
« Last Edit: September 28, 2014, 12:56:42 pm by andyjazz07 »
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Re: Using the 31-band main EQ as high pass filter
« Reply #1 on: September 28, 2014, 01:23:51 pm »

Andrew...

The sub contains a cross-over.  There is an output for you to use to send the properly filtered signal to the amp running your tops..  No need to try and kludge a fix with the graphic...which is really not a good solution if you care about how it sounds.

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Scott Holtzman

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Re: Using the 31-band main EQ as high pass filter
« Reply #2 on: September 28, 2014, 07:12:46 pm »

Andrew...

The sub contains a cross-over.  There is an output for you to use to send the properly filtered signal to the amp running your tops..  No need to try and kludge a fix with the graphic...which is really not a good solution if you care about how it sounds.

Those are one of the better products out of Behringer.  They are as good as the EL ELX and any other 18" powered subs that cost less than $1000.  If you move them around do yourself a favor and put some good casters on the back.

Dick is spot on.  Connect the main mix to the Behringer then connect the amplifier for the mains to the Behringer High Pass out.

If you want to keep the subs aux fed.  You need to have a crossover.  I just bought a used DBX crossover in the Marketplace on this forum for $60 that works perfect.

Why is the leadership at the Church leary of expending such a small amount?   Do they need to be educated on the subject?  If they simply want another opinion is will start that ball rolling -

Expert Opinion (or at least well experienced) - You need a crossover if you intend to continue aux feeding the subs (the best method) if if using integrated crossover is logistically difficult due to placement.

Speaking of placement make sure you test different different locations.  It is always best to have the subs stacked or next to each other.  The worst sound will come from having them in a stage left/right configuration.


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Andrew Yakin

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Re: Using the 31-band main EQ as high pass filter
« Reply #3 on: September 29, 2014, 12:25:25 am »

Andrew...

The sub contains a cross-over.  There is an output for you to use to send the properly filtered signal to the amp running your tops..  No need to try and kludge a fix with the graphic...which is really not a good solution if you care about how it sounds.
Hi dick rees, thanks for your advice. That did run across my mind as well but my concern is that the subs are placed in front near the stage where as the amp for the tops are at the sound booth at the back (about 60 feet apart). That means, I need to draw main stereo output from the mixer into the input of the subs then from the subs output back to the amp then to the tops again right? would this affect the audio signals in any ways? I don't think my church would agree to bring the amp to the front area

Andrew
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Andrew Yakin

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Re: Using the 31-band main EQ as high pass filter
« Reply #4 on: September 29, 2014, 12:33:34 am »

Those are one of the better products out of Behringer.  They are as good as the EL ELX and any other 18" powered subs that cost less than $1000.  If you move them around do yourself a favor and put some good casters on the back.

Dick is spot on.  Connect the main mix to the Behringer then connect the amplifier for the mains to the Behringer High Pass out.

If you want to keep the subs aux fed.  You need to have a crossover.  I just bought a used DBX crossover in the Marketplace on this forum for $60 that works perfect.

Why is the leadership at the Church leary of expending such a small amount?   Do they need to be educated on the subject?  If they simply want another opinion is will start that ball rolling -

Expert Opinion (or at least well experienced) - You need a crossover if you intend to continue aux feeding the subs (the best method) if if using integrated crossover is logistically difficult due to placement.

Speaking of placement make sure you test different different locations.  It is always best to have the subs stacked or next to each other.  The worst sound will come from having them in a stage left/right configuration.

Hi Scott, thanks for the valuable advice. I'll get the church to buy crossover then..Its interesting though when you mention about the placement of sub woofers because most setup that I've seen normally setup in stage left/right placement. Would you mind explain any reason for that? However, I will try your advice to put them next to each other and see the result

Andrew
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Scott Holtzman

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Re: Using the 31-band main EQ as high pass filter
« Reply #5 on: September 29, 2014, 03:14:54 am »

Placement on either side of the stage is done for the human desire for symmetry and because the manufacturers put pole mounts on them.  It's easy.

The more you tell the more problems you have that a professional engineer could make your system sound much better.

Placing the amplifier 60ft back from the speakers is wasting probably half the pour to push the power to the speakers.  On the other hand, balanced, high impedance wiring can run 1000 feet with no appreciable degradation or breakdown of induced noise rejection.

I also doubt that your mains are time aligned with the subs.  This will result in smearing and muddy sound within the crossover overlap region.

To answer your question WRT to placement.  Frequencies as low as a subwoofer reproduces are not directional.   The farther apart the subs the farther they are out of time alignment resulting in a less even coverage pattern and a loss of energy in the boundary areas.  Additionally when you put the subs within a wavelength of each other you get coupling gain.  That's 3db for free.

Now having a single source for the sound will sound cleaner and louder.

It's the same with mains.  Very often in a smaller venue it is much better to center hang the speakers and splay them for all the same reasons as I explained with the subs.

One of the churchs I worked with got passed the mental block and installed a cluster of three Renkus Heinz speakers right up by the projector.  The project was engineered both acoustically and structurally from the start.  The modeling of the arrangement looked great.  Now there is not a bad seat in the house.

It seems that people like the idea of spread apart speakers.  That is how a home stereo looks might have something to do with the bias.





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Scott AKA "Skyking" Holtzman

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g'bye, Dick Rees

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Re: Using the 31-band main EQ as high pass filter
« Reply #6 on: September 29, 2014, 05:23:43 am »

Hi dick rees, thanks for your advice. That did run across my mind as well but my concern is that the subs are placed in front near the stage where as the amp for the tops are at the sound booth at the back (about 60 feet apart). That means, I need to draw main stereo output from the mixer into the input of the subs then from the subs output back to the amp then to the tops again right? would this affect the audio signals in any ways? I don't think my church would agree to bring the amp to the front area

Andrew

Andrew...

I need to know the brand and model of the amp in the booth, the type of connectors on it and whether or not you have any extra, un-used channels left in your audio snake.  If you're lucky, you can just re-configure things with little or no expense.

DR
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George Dougherty

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Re: Using the 31-band main EQ as high pass filter
« Reply #7 on: September 29, 2014, 11:52:04 am »

Andrew...

I need to know the brand and model of the amp in the booth, the type of connectors on it and whether or not you have any extra, un-used channels left in your audio snake.  If you're lucky, you can just re-configure things with little or no expense.

DR

And hopefully the answer isn't, "Well if we unplug the speaker cables from two of the returns, we can move the amp and use those channels to send signal to the amp onstage."

Andrew, if that is the answer, you definitely need to move your amp up front.

Sub placement can be a tricky thing.  Sometimes the center clustered sub doesn't work as well, despite the evenness in coverage it can provide.  Often, everything is a tradeoff.  For instance, I've setup in many rooms where a wide spread to the tops is required for aesthetic or offset screen visibility purposes and center clustering the subs gives nice even coverage, but leaves things sounding thin near the mains due to the shift in balance. 
If you can tolerate it onstage, often the best simple option with a center cluster of subs and wide mains is to move the sub to the back of the stage.  Of course that puts you in a position for frequent complaints about bass onstage and possible feedback with low frequency mic'd instruments.  Flying a sub to increase distance to the front rows and give more consistent overlap with the mains is the better option but only if done by a qualified professional willing to guarantee their work and accept the liability risk.  In other words, unless you're a licensed rigger don't do that or let anyone else in the church do the work for you.
All that to say sometimes split subs are not an entirely bad option and sometimes room interaction helps out to provide more even coverage.  Run some full range pink noise through them and walk the space.  If the volume fluctuates wildly as you move across the room between the subs I wouldn't worry about it.  Google "power alley" to get a visual idea of what kind of patterns you might expect to hear with split subs.
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Re: Using the 31-band main EQ as high pass filter
« Reply #7 on: September 29, 2014, 11:52:04 am »


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