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Dialing-in your subs: Methods?  Test Hardware / Software?
Dialing-in your subs: Methods?  Test Hardware / Software?
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Old 12th June 2019, 07:55 AM   #11
ICG is offline ICG  Germany
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Quote:
Originally Posted by chris661 View Post
Omni mics are usually flat to very low frequencies. I'd expect the previously-mentioned B&K omni to do just fine.
Omnidirectional mics aren't ideal for measuring speakers.

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Originally Posted by chris661 View Post
With regards to the crossover debate, Linkwitz-Riley crossovers are -6dB at the crossover point. Butterworth crossovers are only -3dB.
That does not really matter because the acoustical slope and addition will look a lot different, you have to decide from the result, not the theoretically best filter.

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Originally Posted by chris661 View Post
Here's how I'd set it up:
- LR4 at 120Hz for highpass and lowpass
- Invert lowpass
- Play a 120Hz test tone
- Play with the delay on the lowpass until you've cancelled out the 120Hz tone.
- Set lowpass to correct polarity, and you should have lots of 120Hz tone.

Job done.
That works in general. You forgot a very important point though: The correct addition only works if the sub is at the same volume. Usually, it's not though. If the bass amp gain is increased (because more bass is needed), the crossover frequency will shift to higher frequencies (the slope also rises in level) and you'll get a bump there. That means you have to adjust the level of the subs before and - like already said - pull the HP and LP frequencies a bit apart.
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Old 12th June 2019, 02:04 PM   #12
Cableaddict is offline Cableaddict
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Originally Posted by ICG View Post
Maybe it's time to retire the greybox?.
Can't do that! Greybox theoretically has a lot of little eq fixes, plus dynamic phase compensation, plus the Dunness focusing.
I wish they let you add "compensation" EQ within the EAW Pilot software, but they don't. (Once you select a greybox, all other settings are locked out.)
Luckily I can do it upstream in my digital mixer.


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Originally Posted by ICG View Post
.... The acoustical crossover point can be vastly different from the electrical one and since the most subs got a rising response towards higher frequencies, that's very likely the case. The phase might also be off and that can't be fixed without different placement or a dsp. Having a gap between them can help to make it less obvious.
Oh man... This is slightly past my level right now! I understand it, but have no idea how to deal with it. (Hence this thread) I'm going to get the measurement software you mentioned, above, and hopefully that will get me there, but -
Can you recommend any good websites, videos, etc that would help me learn more about this stuff?

Also: Can phase issues be measured, or is it just a case of adding some delay and listening?

Last edited by Cableaddict; 12th June 2019 at 02:06 PM.
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Old 12th June 2019, 02:11 PM   #13
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Quote:
Originally Posted by chris661 View Post

Linkwitz-Riley crossovers are -6dB at the crossover point. Butterworth crossovers are only -3dB.

Here's how I'd set it up:
- LR4 at 120Hz for highpass and lowpass
- Invert lowpass
- Play a 120Hz test tone
- Play with the delay on the lowpass until you've cancelled out the 120Hz tone.
- Set lowpass to correct polarity, and you should have lots of 120Hz tone.

Job done.

Chris
Thanks, Chris.

That's a brilliant idea about flipping the phase to dial-in the delay !!

I'll use that later today when I'm able to set up / test again.
- Plus ICG's idea of shifting the frequency point slightly to compensate for any LF volume boost. (I understand this now.)


HOWEVER: I can't cross at 120Hz, though. EAW processors (which are used for the whole system, like a Driverack) don't let you add anything to the greybox settings, so you HAVE to use whatever EAW set. @#$%$@ I can do anything I want with the subs outputs, though, since there is no greybox data added to those channels.

My gut says not to high pass the KF394's at 120 Hz, anyway. They clearly are "happy" where EAW set them, and I'd rather have the low end of male vocals up in the air. Plus, in my limited experience, subs sound punchier when their LPF is lower, though that could just be a quirk in the particular gear I've owned.

So I'm curious why 120Hz would be your choice as a starting point, assuming that were possible?

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

And FWIW - I'm still not sure exactly what EAW is doing within that greybox. (I haven't been able to get them to tell me yet.) They definitely use Linkwitz-Riley, but I think it's more than just a HPF down there. There must also be some boost around 80 hz, or those boxes wouldn't be flat to 80, so that might complicate the subs' LPF.

I'll report that here when I find out, plus of course any good result I get as I make all these changes.


THANKS, guys, this is all incredibly helpful.

Last edited by Cableaddict; 12th June 2019 at 02:37 PM.
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Old 12th June 2019, 03:14 PM   #14
chris661 is offline chris661  United Kingdom
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Originally Posted by ICG View Post
Omnidirectional mics aren't ideal for measuring speakers.

That does not really matter because the acoustical slope and addition will look a lot different, you have to decide from the result, not the theoretically best filter.

That works in general. You forgot a very important point though: The correct addition only works if the sub is at the same volume. Usually, it's not though. If the bass amp gain is increased (because more bass is needed), the crossover frequency will shift to higher frequencies (the slope also rises in level) and you'll get a bump there. That means you have to adjust the level of the subs before and - like already said - pull the HP and LP frequencies a bit apart.
Omni mics do just fine for measuring speakers. Their low frequency response makes them better than most other polar patterns which have a LF response that varies with distance.

If the system is set flat and more bass is desired, that should be done via overall system EQ instead of turning up the subs.

Chris
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Old 12th June 2019, 04:34 PM   #15
ICG is offline ICG  Germany
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Originally Posted by chris661 View Post
Omni mics do just fine for measuring speakers. Their low frequency response makes them better than most other polar patterns which have a LF response that varies with distance.
Omnidirectional mics got a big disadvantage, they are, well, omnidirectional. If you are alone in a venue, that's sometimes not a problem. If others still work there (bar/kitchen, stage setup, road noise, audience or band arriving, talking, interviews etc) the non directional pickup of noises can make measurements completely impossible. Reflections can be a big issue for phase measurement, depending on how it's done.

Actually, it does not really matter that much, if the mic got a roll-off at the lower end if you want to create a dsp setup for sub/top xo, it's often enough to know the mic and to measure how good the addition is.

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Originally Posted by chris661 View Post
If the system is set flat and more bass is desired, that should be done via overall system EQ instead of turning up the subs.
Yes, that can work. There are good reasons not to do that though.

First thing you throw off with that is the gain structure, it's very easy to get something within the signal chain to become overdriven and it's the least thing you want if there's a digital stage anywhere in the chain. The second thing is, you cannot EQ subs at any frequency at will since it's very easy to get the subs then to exceed the maximum excursion or boost something below the tuning frequency and effectively cancelling the low cut of the controller, which will also kill the subs because of too much excursion. You can avoid that if you eq the subs at the tuning frequency since the membrane movement is the lowest in the whole of its frequency range, that should be done at the controller, not at the console. But before such tricks you have to adjust the level of the subs to the tops. With the EQ you can fine tune after that but not with a lot of + but instead prefer - of the rest, remember, +3dB is already double the power! Especally if it's a digital console you don't know how it behaves that saves your butt if you keep to that.
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Old 12th June 2019, 04:45 PM   #16
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Just to clear something up: Measuring microphones are usually omnidirectional. Sometimes it's better to use a directional mic instead though.
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