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Author Topic: Cardioid array in a 800ppl club. Possible options?  (Read 25289 times)

g'bye, Dick Rees

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #120 on: February 15, 2016, 06:56:47 pm »

You didn't understand me.

I realize that the amp just regulates and rises voltage and the power that is going through the coil is determined by the impedance at that moment.

BUT, We have Driver 1 and we have driver 2.

They both have exactly the same sensitivity curve.
They are both rated at the same RMS power.
They are both rated at the same nominal impedane of 4 ohms.
And they are both connected to an amp that shouldn't run under 4ohms and it's power is the same as the RMS power of the driver. So it's slightly underpowered for those drivers.

Now, the only thing that is different between these drivers is that driver 2 stays consistantly around 4 ohms over the entire frequency spectrum but driver one has peaks up to 8 ohms at many spots.

This basicaly means that driver 1 will run quieter of this amp generally.
Because it will be using it's power not as much as it could at all frequencies.
If we had a more powerfull amp, we could compensate for drivers impedance jumps by boosting power at frequencies at which the driver has higher impedance.

So in a way, the impedance graph will have a connection with how loud the driver can get unless you have an overpowered amp and can push it as hard as possible at all frequencies.

You have quite an imagination.
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #121 on: February 15, 2016, 08:59:53 pm »

You didn't understand me.

I realize that the amp just regulates and rises voltage and the power that is going through the coil is determined by the impedance at that moment.

BUT, We have Driver 1 and we have driver 2.

They both have exactly the same sensitivity curve.
They are both rated at the same RMS power.
They are both rated at the same nominal impedane of 4 ohms.
And they are both connected to an amp that shouldn't run under 4ohms and it's power is the same as the RMS power of the driver. So it's slightly underpowered for those drivers.

Now, the only thing that is different between these drivers is that driver 2 stays consistantly around 4 ohms over the entire frequency spectrum but driver 1 has peaks up to 8 ohms at many spots.

This basicaly means that driver 1 will run quieter of this amp generally.
Because it will be using it's power not as much as it could at all frequencies.
If we had a more powerfull amp, we could compensate for drivers impedance jumps by boosting power at frequencies at which the driver has higher impedance. Because if the driver can take 500w rms at all frequencies. And the amp needs let's say a 50v output at four ohms to use all of drivers headroom then if the impedance jumps to 8 ohms the amp needs to rise the voltage in order to use all of the drivers headroom.

So in a way, the impedance graph will have a connection with how loud the driver can get unless you have an overpowered amp and can push it as hard as possible at all frequencies.
I really do not know how to respond to this.

There are so many things that are wrong with the "thinking".

You need FORGET about "equal power thing".

If 2 speakers have the same sensitivity TO THE SAME VOLTAGE (Notice I did NOT say power), then they will be the same loudness at all levels.

Who said loudspeakers handle the full power at all freq?

No manufacturer that I know of.

The way the wattage is determined is a noise signal is applied at a certain VOLTAGE (notice no power is mentioned) and they can handle this voltage with no damage.

The power is then CALCULATED using the nominal impedance and the voltage applied.

At freq that the impedance is higher-there will be less power being USED by it. 

It is NOT a good idea to "think" that you can get greater loudness by boosting at the freq at which the impedance is higher.

SURE-you can do that- if LOUDNESS is THE ONLY thing you are interested in.  The sound quality will get all kind of screwed up.

NO measurement system used for freq response measures the power going to a speaker.  They simply look at how loud it is.

If some freq as as loud as others-but only 1/10th the power is going to them-GOOD.

But nobody (almost nobody) ever even thinks about trying to have equal power at all freq.  It is about equal loudness.

I don't know if that helps.

Not to be rude-but you really need to change your way of thinking about this.
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radulescu_paul_mircea

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #122 on: February 16, 2016, 05:37:58 am »



You didn't understand me.

I realize that the amp just regulates and rises voltage and the power that is going through the coil is determined by the impedance at that moment.

BUT, We have Driver 1 and we have driver 2.

They both have exactly the same sensitivity curve.
They are both rated at the same RMS power.
They are both rated at the same nominal impedane of 4 ohms.
And they are both connected to an amp that shouldn't run under 4ohms and it's power is the same as the RMS power of the driver. So it's slightly underpowered for those drivers.

Now, the only thing that is different between these drivers is that driver 2 stays consistantly around 4 ohms over the entire frequency spectrum but driver 1 has peaks up to 8 ohms at many spots.

This basicaly means that driver 1 will run quieter of this amp generally.
Because it will be using it's power not as much as it could at all frequencies.
If we had a more powerfull amp, we could compensate for drivers impedance jumps by boosting power at frequencies at which the driver has higher impedance. Because if the driver can take 500w rms at all frequencies. And the amp needs let's say a 50v output at four ohms to use all of drivers headroom then if the impedance jumps to 8 ohms the amp needs to rise the voltage in order to use all of the drivers headroom.

So in a way, the impedance graph will have a connection with how loud the driver can get unless you have an overpowered amp and can push it as hard as possible at all frequencies.

Pfiu! No, as Ivan said, you first have to learn how drivers in speakers work. A driver/speaker has a variable impedance curve Because it is a reactive load. The sensitivity of the speaker is given as the voltage sensitivity in reality. They find out what is the nominal impedance rating in the usefull bandpass, and if it is 8 ohms they teat it with constant 2,83 V, if it is 4 ohms they use 2.0 volts etc. Remember, it is a constant voltage and not constant power. It is the way it works.
So, now, if you have a driver rated 100 db at 1w/meter at 4 ohms, and 1000 watts and another at 100db/w at 8 ohms and 1000 watts, and an amp capable of 1000 watts/8ohms and and another at 1000/4ohms they will both get to max 130 db and no more if you use the correct amp for the correct driver. The difference is that one is rated at a higher voltage than the other.
Now if you would switch the amps and they are both stable at even 2 ohms, then you will see what impedance is doing. The 8ohms driver on the 1000watts/4ohm amp will get only 500 watts Nominal. The other one on the other amp will get 2000watts nominal. One will burn one will be underpowered.
There are current based amplifier, that have constant power at variable frequencies but they have to work with special speakers, designed!!!! to work with that kind of amp. Our speakers and our amps are designed to work with constant voltage. If you know how to play in Hornresp you have the posibility to see what constant voltage and what constant power does to the frequency response of a speaker
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #123 on: February 16, 2016, 06:23:17 am »

Okay there seems to be one majour thing i understood completly wrong here and therefore got all these wrong assumptions.

Sensitivity is measured with voltage. If 2 drivers have 100dB sensitivity at 500hz that means that if any of them gets 50 volts at 500hz they will play exactly the same loudness.
BUT if their impedance is not the same at that voltage, one of them will pull more power then the other one.

Okay, that's all quiet clear. BUT again. If they are both capable of handling the same amount of power at 500hz then the one with a lower impedance will be a less capable driver. Because when we give them both the same voltage. The one with a lower impedance is going to be closer to it's thermal limits.
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radulescu_paul_mircea

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #124 on: February 16, 2016, 06:30:17 am »



BUT if their impedance is not the same at that voltage, one of them will pull more power then the other one.

Okay, that's all quiet clear. BUT again. If they are both capable of handling the same amount of power at 500hz then the one with a lower impedance will be a less capable driver. Because when we give them both the same voltage. The one with a lower impedance is going to be closer to it's thermal limits.
If you put a sine wave at that freq , yes, you are right. The one with lower impedance will get more amps and heat and will have the same Spl. To the other, ypu could rise the voltage to get the same amps and heat and it will give more spl. You understood correctly
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radulescu_paul_mircea

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #125 on: February 16, 2016, 06:45:23 am »

As another example, if you have a closed sub and it has a liniar resp from 30 hz with a maximum given power and it doesn't reach xmax at max power but it has a rising impedance from 30hz down, one could rise the voltage to get more Spl at those frequencies without risking to burn the coil. So if you apply your theory like this, it is usefull. Also, this is why in subwoofers, horn subs are (not really  a rule) capable of getting not only a better sensitivity but also a better power(read voltage) handlling, because in the bandpass, the impedance is more variable and the average dissipated heat in a music program (not sine wave) will be less at the same voltage.
Also, I see why everybody gets confused qith these terms. It always is the power that is specified in products. This is because most if the time, power is the thing that limits us. But the speakers are made to be linear with a constant voltage and also it will allow a specific maximum heat dissipation.The average power a driver can dissipate, the max power vs time an amp can generate etc. But having more data about impedance curves, , response curves, electric phase curves, specific heat, temperature rise times,max temperatures,  and so forth for the drivers and also more infos about the capabillities of amplifiers(power vs time,  clipping behavior, max voltagevs frequency, thd, imd and so forth) one could create a very high performance system, that would push the limits but never exceeds them.
« Last Edit: February 16, 2016, 06:51:44 am by radulescu_paul_mircea »
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #126 on: February 16, 2016, 07:08:47 am »

Yes, well the point is understanding this teory well so i can use it in reallity.
Many soundguys tell me how pushing subs too low is dangerous because the lower the frequency is the more power a driver will need and lower frequencies will heat up the coil exponentialy more...
But this is a completly wrong statement.
Yes, pushing subs lower then you should might not be a great idea because of some other reasons. But in reality. If i take a good look at the impedance graph of my subwoofer and realise it starts jumping impedance under 40hz but starts dropping impedance between 40 an 60hz. That might mean that my drivers are going to be safer if i push them hard under 40hz and keep them a bit quieter between 50 and 60 then they will be if i lowcut them at 35 and force the hell out of them at 50 and 60hz.

And yes, in order to understand theory i try making my questions and examples in them as simple as possible but i am aware of the amount of factors that i need to be counting on when i try using this in reality.
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radulescu_paul_mircea

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #127 on: February 16, 2016, 07:27:53 am »

A subwoofer starts to loose efficiency under Fs so at the -10 point if you need ten times the power to reach the level over fs. So it is not a good thing to do that, they are right. Best case scenario, if some speakers have the impedance rising A Little under F3 so one can get a few hertz extension, and not always linear but with a down curve. Take care
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #128 on: February 16, 2016, 07:35:21 am »

Yes, well the point is understanding this teory well so i can use it in reallity.
Many soundguys tell me how pushing subs too low is dangerous because the lower the frequency is the more power a driver will need and lower frequencies will heat up the coil exponentialy more...
But this is a completly wrong statement.
Yes, pushing subs lower then you should might not be a great idea because of some other reasons. But in reality. If i take a good look at the impedance graph of my subwoofer and realise it starts jumping impedance under 40hz but starts dropping impedance between 40 an 60hz. That might mean that my drivers are going to be safer if i push them hard under 40hz and keep them a bit quieter between 50 and 60 then they will be if i lowcut them at 35 and force the hell out of them at 50 and 60hz.

And yes, in order to understand theory i try making my questions and examples in them as simple as possible but i am aware of the amount of factors that i need to be counting on when i try using this in reality.
No freq heats up a driver any more than any other freq-AS LONG AS the impedance of the driver is the same.

At different freq the heating will be different.

Now EXCURSION is a completely different issue.

What the lower peaks on the impedance curve tell you is where the cabinet is tuned.

In a ported cabinet you will see 2 peaks.  If it is properly tuned, they should be equal.  The tuning freq is the freq at the low point between the 2 peaks.

You REALLY REALLY NEED to STOP thinking about how hard you can drive your cabinets based on the impedance.

You should be more focused on the freq response or amplitude of the system.

Unless the ONLY thing that is of interest to you is loudness-no matter what it sounds like.

If you start to "get the most" due to the impedance-you will end up with a very unbalanced sound.

For example-let's say a DJ does a sweep- and you have boosted certain freq due the impedance idea.

Well the sweep is going to louder and quieter at different freq  Is that what you want?  I doubt it. 

But if it makes you feel better to say "Well I am "pushing" the maximum out of the system", then OK .  But people don't care about that-they care about how it sounds-at least most people do.
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #129 on: February 16, 2016, 07:55:53 am »

Yes i understand there is no more point in pushing the speaker when it hits anything above a -6dB drop in sensitivity. I didn't say i should push subs lower then they can go in reality. But i shouldn't push them from different reasons. Not from a reason that lower frequencies heat up the coil more. As Ivan said, the amout of heat a coil generates depends only on the amount of power going through it and the resistance that the coil makes. Or in the other words heat depends on the voltage the amp is giving it and the impedance of the coil at a certain frequency.

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?
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?

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
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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #129 on: February 16, 2016, 07:55:53 am »


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