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Author Topic: Cardioid array in a 800ppl club. Possible options?  (Read 24101 times)

Art Welter

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #130 on: February 16, 2016, 11:39:37 am »

1)Shouldn't the impedance/frequency graph be the same if the driver is in open air vs any kind of box?
Or... shouldn't it be the same even if we just have the coil itself out of the driver completly. Why does the way coil "moves" at a certain frequency affect it's impedance.  What am i missing?

2)Yes if i start trying to get the most out of the system based on impedance it will sound unbalanced BUT if i know how and where i can get more... then i can tune the system better. I won't boost a certain area just because the driver can take more in that area. But if it drops sensitivity 3dB from 30 to 25hz and i know i can push it more in that area. Then i will, and it's response is going to get a bit flatter from 30 to 25hz
1) The DCR (direct current resistance, what you measure with an ohmmeter) of a voice coil will be the same regardless of it being in or out of a box. In a box, the resistance becomes impedance, and different boxes have different impedance transforms, which is why the impedance curve is different for different designs. Most designs will have an impedance minima very close to or equal to the DCR.

2) You seem to have already forgot that there are two failure modes in a speaker- thermal and mechanical. When you drive your speakers below Fb, (you obviously skipped measuring their Fb, which is probably around 45 Hz) the power is wasted, and the excursion rises rapidly (you would have seen that if you measured it) increasing the muddy sound you complain of, and potentially will tear the cone, surround, or spider, or hammer the voice coil on the back plate if the driver is given enough voltage. Below Fb, it takes very little voltage to exceed Xmax in a bass reflex enclosure.

Art
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radulescu_paul_mircea

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #131 on: February 16, 2016, 12:54:17 pm »

The direct current resistence or DCR of a wire is a propriety of the material and varies only with wire thickness and temperature.
This resistance will be different and will vary with alternative or changing current because of many reasons. The whole amount of factors inclusive wire resistance will impede the flow off current and there is the term "impedance" comming from. You should search about this on the net or books.
In a voice coil in free air wirh a constant temperature the wire has a fixed DCR equal with the declaired RE in Thiele small parameters. When you apply alternative current this coil of wire will have a constant impedance rise as you go higher and higher in frequency because of a thing called skin effect but that starts at a Very high frequency.
If you put the coil inside a magnet system coupled with a diaphragm, suspensio, moving parts, magnetic fields, eddy currents etc the impedance will be very different than the DCR and it will have a resonant frequency where all those factors will sum. If you then put that driver in a closed enclosure you will change some of the mechanical properties of that system and the impedance will be different but it will still have only one resonant frequency. If you put it in a bass reflex you change it more, in a horn even more, add many drivers in a 4 way system, also the crossover components, the wires, interferences, amplifier behavior and you will understand why the impedance curve is not a simple number.
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #132 on: February 16, 2016, 05:55:21 pm »


Ivan:
How are impedance variatons related to how a cabinet affects the driver? The impedance of a coil depends on the material that the coil is made of (copper) and the number of windings.
Shouldn't the impedance/frequency graph be the same if the driver is in open air vs any kind of box?

No-the box can greatly affect the impedance or the loading of the driver to the air.

In fact-you can take a HF driver and set a constant tone impedance meter in the HF range and move your hands above and around the exit (the driver is not on a horn at this time) and watch the impedance change with your hand movements.

There is a lot to be learned from the impedance curve in terms of how the driver is "loaded" to the air.

This is why certain sub designs can actually double the rated impedance of the driver-due to the loading.
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Ivan Beaver
Danley Sound Labs

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Stephen Kirby

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #133 on: February 17, 2016, 01:40:44 am »

Maybe download WinISD and model your Yamaha boxes.  The Eminence T/S parameters should be in there and you can just start with the approximate dimensions you can see.  Now look at the impedance curve and note where fb and fs are relative to that.  Start playing with the port dimensions to try and get the box to play lower.  Now watch what happens with the impedance graph and the xmax excursion graph.  That may help you envision the interrelationship between the box tuning, the impedance curve and the driver excursion.
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #134 on: February 17, 2016, 06:18:38 am »

Yes but i wanted to know why this happens. Then a friend reminded me of some basic electrotechics from school.
Whenever the coil is moving in the magnet gap there is going to be electricity induced back in the coil, by the magnet. This electricity will create resistance to the electricity the amp is pushing to the coil.
I think it's called Lenz's law.
Which means a simple thing. Change the way the coil moves in the magnet gap (put the driver in a drifferent box for an example). And you changed the way that magnet induces electricity in the coil.
In the other words, you changed the coils impedance.
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #135 on: February 17, 2016, 06:28:47 am »

Also, we did some preparations for the party this friday.
Tried out a cardioid array. Runs like shit in a closed room, just as we expected.

Here:
http://i30.photobucket.com/albums/c316/athlon-64/IMG_4220_zpscobjps2x.jpg

You get cancelation in a relatively big spot behind the subs. When you get close to the walls there is just chaos you can not fix. And outside, in front of the subs, this setup brings nothing good.

So we put them down in a standard mono block:

http://i30.photobucket.com/albums/c316/athlon-64/IMG_4222_zpsuoq4s41z.jpg

http://i30.photobucket.com/albums/c316/athlon-64/IMG_4223_zps6n1oovpn.jpg

And i realised they work quiet a lot better like this. When you are standing in front of the stage you are in the power alley of the subs so you hear them, not the room. I hooked them up to my peecker sound amps with shorts cables. Did some tests and even felt the transients, hits of short sub on top of basslines. Quiet a bit better then usual it seems to me. Maybe it's just mostly about the room. When ther are left and right the simple problem is. Wherever you are (unless you are in front of the boxes) you hear sub chaosing around from the room. You don't hear much directly from the boxes. But in a mono block like this everyone in front of the stage feels more from the subs then from the room.

I also tried a compressor trick that seems to work. A friend explained me this a few days ago:
Insert a compressor on the matrix of the subwoofers. Make the transients an peaks activate it, when they do, make it compress everything hard but with a slow attack tome so the transients pass.

What happens when i do this is quiet much... the short hits of sub stay untouched while the subline gets quieter. I liked it a lot because these sublines can overload the room, things start shaking and making a lot of noise. All of that sub just sums into a big mess of mud because it has nowhere to go. So the compressor gets that part a bit quieter. But leaves me those peaks and transients where i need them. This gives me a more dynamic less muddy sound from the subs.

Also we realised we have a dead 18. Just one of them in one of the boxes.
Who knows when this happend. It might be months/years old. I'm not the only one running the system so again, who knows who this happened to.
« Last Edit: February 17, 2016, 06:32:34 am by Eugen Jeličić »
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #136 on: February 17, 2016, 12:09:52 pm »


I also tried a compressor trick that seems to work. A friend explained me this a few days ago:
Insert a compressor on the matrix of the subwoofers. Make the transients an peaks activate it, when they do, make it compress everything hard but with a slow attack tome so the transients pass.


THat is the same thing as a "thermal" limiter.  With an attack time of around 3 seconds all the transients pass fine (which do not cause heating of the voice coil), but the long term power (which overheats the coils) is limited to around 1/4 to 1/2 the continuous rating of the driver.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #137 on: February 17, 2016, 05:25:38 pm »

THat is the same thing as a "thermal" limiter.  With an attack time of around 3 seconds all the transients pass fine (which do not cause heating of the voice coil), but the long term power (which overheats the coils) is limited to around 1/4 to 1/2 the continuous rating of the driver.

Yes, so it's good for the driver and it's a way to slightly accentuate transients
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #138 on: February 17, 2016, 07:22:05 pm »

Yes, so it's good for the driver and it's a way to slightly accentuate transients
The problem I see with trying to use this as you describe is that now YOU are affecting the sound the artist is trying to project to the audience.

The sound system should simply make their sound louder and not change the sound.

If the artist WANTED it that way-they would record it that way.  But you are changing their sound on purpose.

Now, when used as protection to keep the loudspeakers from being damaged-that is a totally different thing.

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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #139 on: February 18, 2016, 04:58:07 am »

The problem I see with trying to use this as you describe is that now YOU are affecting the sound the artist is trying to project to the audience.

The sound system should simply make their sound louder and not change the sound.

If the artist WANTED it that way-they would record it that way.  But you are changing their sound on purpose.

Now, when used as protection to keep the loudspeakers from being damaged-that is a totally different thing.

No, the soundsystem itself because it's not that good, and the room, because it's terrible, are changing the sound of what the artist had in mind. Then my job is to use all the tools i have to get it as close as the soundsystem can get it back to the original.
I try my best to know the music i'm working with that night. I listen to it before on a pair of monitors. Also i use music very familiar to me when i'm soundchecking and i know this system won't push it out nearely the way it should.
I'm not making the transient stand out more then it should. I'm just making sure it stands out like it should if i can because the combination of yamaha subs and the room would destoy and drown it.
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