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Hi-Pass Settings
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j.robinson389
Prenoob

Joined: 03/11/2011 17:27:04
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Will be putting in an SL24 next week at our church and I wanted to get some pointers on using the HPF. I know the filter is 6dB/octave which is less steep than most would prefer from what I understand.

I assume with a 6dB/octave curve you can turn uo the frequency a little bit to help compensate but where do you like to set them for?:

Vocals:
Soprano
Alto
Tenor

Instruments:
Guitar
Keys
Bass (I assume you leave it off here)

I also assume you put a HPF on monitors as well? If so at what frequency?




I know this is mostly a preference thing, but I'm just looking for somewhere to start.


Thanks in advance,
Jake
gadget69
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Hi,
This is a subject that can make or break your "performance" as an audio technician. The Hipass, and lowpass are your best friend. Allowing a (microphone especially) source to cover the full range of (whatever the mic can do) is asking for trouble. The idea is to place each instrument in it's place in the mix.

One of the bad things about having a whole bunch of open mics (like most live situations do) is all the low frequencies that permeate the stage environment. Those low frequencies for instance vibrate the mic stands as well as get picked up by the mic elements. Multiply this times the number of open mics can quickly add up to a LOT of unnecessary low end in the system, and monitors;

Here, an HPF can make have a HUGE affect on the room swell, and stage volume. Lets look at the female voice for instance... There rarely is any useful content in a female voice below about 200 hz, yes there are harmonics and things, but for all practical purposes these will get lost in a dense mix anyway. There is also nothing much above 8K (again except harmonics and overtones) that can get through a live event.

We can keep much of the low end from being reproduced in that mic by setting an HPF. We can also keep a lot of the cymbal sound out of the mic by setting a LPF as well.

Where the HPF and LPF need to be set is largely a function of the frequency range of the instrument/vocal, and the slope of the filter. The fact that the HPF on the console is 6dB/ octave is a bit of a problem however. This means that if you set the filter @ 200 hz, that 100hz is only about 3dB down, and not enough to be inaudible by any means.

So what does this mean for you? What I have found is that on the channel strips the best thing is to adjust and listen. I have a cue wedge at my side that is pretty much fullrange active, and I select a channel I want to work on and activate the HPF and start rolling it up till the desired effect is achieved. If we look at that female voice again this may have the HPF set in the 400hz area to have any attenuation @ 200hz and below. In any case setting it lower than 200 hz isn't going to give sufficient attenuation to the frequencies below the 200 hz we spoke of and 400hz might be a bit high...

In monitors I have also found that a lot of information in the LF simply adds to the stage din, and makes the volume you need to get to in order to get over the stage volume that much higher. It also clutters up the stage sound so that it also seems to always creep up and up... one way to counter this is to set the HPF fairly high, I usually get the best results setting this @ 150-225hz. It allows some channel strip and Aux fat channel equalization to be added, but keeps the majority of the undesirable low end out of the monitors.

So, in summary, with a 6dB/ octave filter (I would really like to see this addressed and set to at least an 12-18dB 'preferably 18dB...' per octave filter) you are going to end up with the HPF set higher than you would suspect you would need to...here is a chart that shows the primary frequency range of various sources:

http://i227.photobucket.com/albums/dd145/gadget69/main_chart.jpg

Use it to visualize where the HPF needs to be set for that source.
main_chart.jpg
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This message was edited 3 times. Last update was at 05/04/2012 19:59:15

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CHIP ROBERTS
Prenoob

Joined: 09/08/2011 07:20:38
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Yeah, this is why I had to switch to aux fed subs. The HPF has proven useless. The variable HPF was one of the reasons I bought an SL24.4.2. Yeah, the 6dB/octave is just nowhere near enough.
MikeRivers
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Short answer is that you don't set high pass filters for vocals or instruments, you set it for the presence of low frequency noise that you want to get rid of.

For any type of equalization or filtering, the best initial setting is OFF, then you use what your ears tell you to use. There are some rules of thumb, or rather, settings that rarely will do any harm, like when you're on a stage, setting all the high pass filters for mic channels at around 80 Hz., but beyond that, only use them when you hear a problem.
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Jerryd
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Joined: 28/07/2010 16:01:24
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You can get very close to a BW18 Slope by using the LOW SHELF with a full cut (or close to a full cut). You will still need to use the High Pass.

It is difficult to have standard high pass numbers for vocals or other instruments simply because it depends on how the PA system is set up.

For example -- the flatter the system response -- the less High pass or Low shelf will be needed. If the Low end response is haystacked by plus15-20dB -- you will be very surprised at the settings you will have to use to control it.

In a church setting -- it will probably not be haystacked much at all so it will take less high pass and low shelf.

Bottom line: Your ear has to be the guide. Start with low numbers and adjust frequency upwards with careful listening.
samuel2230
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Digico SD series has 24db/octave HPF and LPF on every channel! I definitely miss that when working on a Presonus....
Monolithent
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Would be sweet for the next iteration of the StudioLive. Just call it the pass filter and a single button.

First press gets you the high pass and the second press gets the low pass. Then set the slope in the display. Or maybe just set that one solid at an 18.

Just thinking out loud...continue please.

I hi pass just about everything. I tend to leave fully digital items alone like keys and most digital drums. It's definitely getting a filter if it's got a mic. I hate rumble!

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MikeRivers
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samuel2230 wrote:Digico SD series has 24db/octave HPF and LPF on every channel! I definitely miss that when working on a Presonus....


But I'll bet you don't miss the cost saving.
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gadget69
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Ok Mike, I have to respectfully ask (and maybe I simply read it wrong, it certainly wouldn't be the first time) what is it that you see as a downside to using HPF (and LPF as Jon pointed out...although we really don't have that with this console, other than a shelf filter like Jerry said) on a per channel basis?

The fact that there are numerous mics in contact with the stage and it's pervasive low frequencies, and those that are transmitted by air have proven to create loading of the stage and building with LF energy. Being able to limit the range of frequencies to a given instruments/vocalists range of usable frequencies allows for, in the dense spectrum of typical live sound reinforcement, us to concentrate on the mixing in stead of the typical putting out of fires, or simply damage control over quality sonic decisions.

I'd be very interested to hear your thoughts on this.

Best regards
NOTE: If your having an issue, open a tech support ticket and bring the number here if you want help!
http://support.presonus.com

Tools:
OHCI tool and Latency mon:
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We, the few, that have done so much, for so long that now we can do everyything with nothing

dbx forum moderator

Lenova Ideapad Z565
Best connectivity Express card/firewire 2 port (400) that does NOT suggest having the TI chipset. (always worked great)
BYTECC Express card (400/800)07150358281

Asus/AMD processor tower. This setups just works on all firewire devices.

Belkin N450 dual band router, works with SL and Ai mixers
Studiolive 16:4:2
SL Ai24.4.2
ABUSB 1818VSL
Faderport
USB pre interface
Studio one Pro V2
LABsubs

loads of audio, and studio gear, and audiophile sound gear (gearslut)
[Email] [Yahoo!]
MikeRivers
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gadget69 wrote:Ok Mike, I have to respectfully ask (and maybe I simply read it wrong, it certainly wouldn't be the first time) what is it that you see as a downside to using HPF (and LPF as Jon pointed out...


Oh, there's no downside to using it if you need it, but to assume you need it and ask for suggested settings is, in my book, wrong. You might be cutting out something that's supposed to be there. Though, admittedly, with the gentle slope of the StudioLive filters, unless you start cutting at 250 Hz or so, you can probably still hear plenty. Sure, if I'm working outdoors and there's some wind and a resonant stage and truck traffic going by, if I have 12 or 18 dB per octave low cut filters, I'll switch them in on everything except maybe the bass and kick drum, but I'll listen to what's happening on stage to be sure I'm not cutting something that I don't want to cut.

I feel the same about the question "What's the right EQ setting for an acoustic guitar?" My answer to that is "Flat, until you hear something that needs fixing, then whatever it takes to fix what you hear." I just don't take too kindly to folks who think that this job can be done by formula. It's about listening first, without something in the way to change what's going into the mic.

Visit http://mikeriversaudio.wordpress.com for some useful audio info
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Big Joe Daddy
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That's a handy chart Gadget. Thanks!
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