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-   -   Serial and Parallel drivers (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers.html)

bvbellomo 30th May 2013 05:45 PM

Serial and Parallel drivers
 
I know this has been asked many times before, but there are many different answers and a lot of wrong information. Is the following correct or incorrect about series or parallel drivers?

If I connect 2 drivers in series:
1) 3db louder at the same wattage
2) half the current at the same voltage
3) twice the impedance
4) twice the wattage before distortion
5) twice the wattage before damage

If I connect 2 drivers in parallel:
1) 3db louder at the same wattage
2) twice the current at the same voltage
3) half the impedance
4) twice the wattage before distortion
5) twice the wattage before damage

The rules for connecting a set of drivers already wired in series or parallel are exactly the same as for connecting individual drivers.

Dissi 31st May 2013 12:47 AM

Hi bvbellomo,

It's always tricky, but I would say 100% correct.:)

From a practical point of view we could add:

If I connect 2 drivers in series:
6) same spl at the same voltage

If I connect 2 drivers in parallel:
6) 6 dB more spl at the same voltage

wolf_teeth 31st May 2013 07:08 AM

Quote:

Originally Posted by bvbellomo (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers-post3509535.html#post3509535)
I know this has been asked many times before, but there are many different answers and a lot of wrong information. Is the following correct or incorrect about series or parallel drivers?

If I connect 2 drivers in series:
1) 3db louder at the same wattage (This should say +3dB efficient, as louder is incorrect in terms of voltage sensitivity being no difference in perceived output level.)
2) half the current at the same voltage
3) twice the impedance
4) twice the wattage before distortion
5) twice the wattage before damage

If I connect 2 drivers in parallel:
1) 3db louder at the same wattage (Again- +3dB efficient, +6dB sensitive)
2) twice the current at the same voltage
3) half the impedance
4) twice the wattage before distortion
5) twice the wattage before damage

The rules for connecting a set of drivers already wired in series or parallel are exactly the same as for connecting individual drivers.

Wattage is usually equated with efficiency, and voltage with sensitivity. See my alterations or comments above.

Later,
Wolf

tinitus 31st May 2013 08:26 AM

2 woofers in series may not give you more output in terms of measured/calculated SPL

but if they are of smaller size it should give better power handling and lower distortion
and you might experience this as being more powerful, and louder

not multiway woofers, but I once in my youth connected two 6" fullrange drivers in series
and it sound better than when in paralel
somehow smoother

but it was common knowledge not to series connect drivers
so I didnt, even when it sounded like better
I guess that was a mistake

I also have some small Foster tweeter horn drivers
sounds like crap one by one
even worse in paralel
but connected in series they sound quite sweet really :scratch:
but who wants two series connected tweeters :clown:

AndrewT 31st May 2013 09:43 AM

A driver will give a certain SPL for a watt of input.
Two drivers each with half a watt of input will give the same SPL.
Except, when the drivers comply with very rigorous conditions. Sometimes the SPL can be upto 3dB louder than the wattage predicts. This is due to the way the air loads the driver. Two drivers very close to each other relative to the frequency they are being asked to reproduce will affect the air loads of each other. When the frequency is low enough there is a full 3dB of extra output due to this air load interaction.
As the reproduced frequency rises the extra 3dB gradually falls off to nothing extra.

This all makes conclusion 1), in both sets, wrong for most conditions of operation.

bvbellomo 31st May 2013 01:04 PM

Quote:

Originally Posted by wolf_teeth (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers-post3510257.html#post3510257)
1) 3db louder at the same wattage (This should say +3dB efficient, as louder is incorrect in terms of voltage sensitivity being no difference in perceived output level.)

1) 3db louder at the same wattage (Again- +3dB efficient, +6dB sensitive)

Wattage is usually equated with efficiency, and voltage with sensitivity. See my alterations or comments above.

Later,
Wolf

Can you please define "efficiency" and "sensitivity" in the context of your comments? "3db louder at the same wattage" is well defined, as an SPL meter measure db and I can measure watts too. If you want to nitpick "3 more db at the same wattage" is a better way of wording what I wanted to say, as it is entirely objective.

bvbellomo 31st May 2013 01:11 PM

Quote:

Originally Posted by tinitus (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers-post3510307.html#post3510307)
2 woofers in series may not give you more output in terms of measured/calculated SPL

Going by what I posted, at the same voltage, they won't.

Quote:

Originally Posted by tinitus (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers-post3510307.html#post3510307)
2 woofers in series may not give you more output in
but if they are of smaller size it should give better power handling and lower distortion
and you might experience this as being more powerful, and louder

I meant this as a theoretical question, 2 smaller woofers might or might not sound better than 1 large one, but that is outside the scope of what I wanted to ask.

Quote:

Originally Posted by tinitus (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers-post3510307.html#post3510307)
not multiway woofers, but I once in my youth connected two 6" fullrange drivers in series
and it sound better than when in paralel
somehow smoother

but it was common knowledge not to series connect drivers
so I didnt, even when it sounded like better
I guess that was a mistake

This is why we need to understand the theoretical, instead of relying on other people's advice.

Quote:

Originally Posted by tinitus (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers-post3510307.html#post3510307)
I also have some small Foster tweeter horn drivers
sounds like crap one by one
even worse in paralel
but connected in series they sound quite sweet really :scratch:
but who wants two series connected tweeters :clown:

IMO comb filtering is more feared than it should be. Of course, this is something else people would benefit from understand the theoretical, instead of just going by standard practices "Never use multiple tweeters" or "Never more than 1/2 wavelength between drivers".

bvbellomo 31st May 2013 01:15 PM

Quote:

Originally Posted by AndrewT (https://www.diyaudio.com/forums/multi-way/236842-serial-parallel-drivers-post3510369.html#post3510369)
A driver will give a certain SPL for a watt of input.
Two drivers each with half a watt of input will give the same SPL.
Except, when the drivers comply with very rigorous conditions. Sometimes the SPL can be upto 3dB louder than the wattage predicts. This is due to the way the air loads the driver. Two drivers very close to each other relative to the frequency they are being asked to reproduce will affect the air loads of each other. When the frequency is low enough there is a full 3dB of extra output due to this air load interaction.
As the reproduced frequency rises the extra 3dB gradually falls off to nothing extra.

This all makes conclusion 1), in both sets, wrong for most conditions of operation.

This is very interesting, do you have links to further information on this? Am I correct in saying everything I said is still correct as long as the drivers are far enough apart not to affect the air loads of each other?

bvbellomo 31st May 2013 01:21 PM

What I am really surprised at is no one commented on 4) and 5), which were guesses on my part, and really important with something like a line array. Suppose I have 16 drivers that individual start distorting enough to sound bad at 20 watts and explode at 40. Using my logic above, the line array should handle up to 320 watts. Different logic can give wildly different power handling numbers, and unless this is well understood, line array builders will either blow all their drivers or never play them near full potential.

AndrewT 31st May 2013 01:25 PM

No !!!!
the drivers need to be VERY close together to get advantage from the coupling of Sd and this only applies at the low frequency end of the passband for that driver combination.
Sometimes the frequency is so low relative to the driver spacing that the +3dB effect is only available below the passband of the driver.


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