Dipole 15" specs with coils in parallel?

[studiotech]

Someone help me out here...I forgot the rules for wiring the coils in parallel. Specifically what does this do to the QTS? I need to end up with a 4 Ohm load and can only fit one 15 one the baffle.

Greg

[simon5]

It doesn't change the Qts at all.

Three parameters will change :
Sensivity will be higher since it's measured at 2.83V, so at 4 ohms you have more current than 16 ohms.
Re will decrease to be 4 ohms instead of 16 ohms.
BL will decrease since magnetic force will be less because you have less voltage.

But since BL (magnetic flux) and Re (resistance) are both decreased in the same proportion, it all evens out. That means all other parameters will stay exactly the same.

Power handling will be exactly the same.
Frequency response will be exactly the same.
Efficiency measured at 1 watt will be exactly the same.

The only way you can change Qts, is by using only a single coil instead of using both coils in series or parallel. Using a single coil is usually a bad idea anyway, due to reduced powerhandling, reduced sensivity, reduced efficiency...

[studiotech]

Thanks Simon! Quick on the trigger there are ya? I'll be placing my order tomorrow.

I would think that power handling would go up since you are putting the power into a parallel load. It works for resistors, so why not voice coils?

Greg

[simon5]

Let say you have two 100 ohms 1W resistors...

In series, it's now a 200 ohms 2W resistor...

In parallel, it's now a 50 ohms 2W resistor...

Same powerhandling !

On the other hand, I think I understand what you are saying. Yes usually you use parallel resistors to increase power handling, by using higher value resistors of the same power handling that you parallel.

For example, 4 resistors of 400 ohms and 1W each will give 100 ohms paralleled and 4W power handling, versus our example of a single 100 ohms 1W resistor, so you get quad the power handling.

But, you could do the same by putting them in series, 4 resistors of 25 ohms and 1W each will give 100 ohms in series and 4W power handling, versus our example of a single 100 ohms 1W resistor, so you get quad the power handling also.

We usually parallel a bunch of resistors instead of serializing them, because it's easier, only two soldering points, and also higher values resistors are usually cheaper. Maybe there's also other arguments of doing it, but I don't know them.

[Aura Audio]

Could you please post a frequency graph for the dipole 15s.
Possible one on its own and another with the driver on an open baffle.

Thanks

[Aura Audio]

Another question about the 4ohm verses 16ohm.
At 4ohms (parallel wired) what is the efficiency and what is the power handling?
Ya that's what we need to know.

[simon5]

Efficiency is the same at 4 ohms or 16 ohms.

Maybe you want to talk about sensivity ? If yes, add 6 dB to 16 ohms sensivity number.

Power handling is the same also.

[Aura Audio]

Then do you get more volume out of 16 ohm? Same power plus the 6db you talk about.
Actually I thought there was 6db more sensitivity at 4 ohms but needed 4 times the power.

[simon5]

A Dipole15 has a Pe(max) of 200Watts and an efficiency of 1WSpl: 90.1dB

Sensivity on the other hand is often measured at 2.83V, so that means 87.1 dB at 16 ohms and 93.1 dB at 4 ohms.

It will not be louder at 4 ohms than 16 ohms if you stay with the same power input, it just gives higher volume on 2.83V because more current will pass in a 4 ohms coil than a 16 ohms coil, so the power input is not the same at all.

The 16 ohms version will have 0.177 amps at 2.83V, that gives 0.5W.
The 4 ohms version will have 0.708 amps at 2.83V, that gives 2W.
That's why you will get higher numbers, at 2.83V the amplifier produce 4 times more power into the 4 ohms load.

The 4 ohms tuned amplifier will produce 200W with 28.3 volts and 7.08 amps.
The 16 ohms tuned amplifier will produce 200W with 56.6 volts and 3.54 amps.

On the other hand, if your amplifier doesn't have a problem to climb high in voltage and is tuned for a 16 ohms load, there's no problem because 200W is 200W.

Whatever coil configuration you choose, it will stay a 200W max woofer. At 16 ohms you will have low current and high voltage, and at 4 ohms you will have low voltage and high current. It just depends on which amplifier you want to use. Both will have exactly the same loudness at full power if both have a properly tuned amplifier for their coil configuration.

[Aura Audio]

Thank you Simon, I understand that totally and its as I thought but is it not better to wire everything in parallel?
If two drivers were to be used for each channel which way would net the most efficiency with best sound if the amp used was stable in 2 ohms?
I have always thought that series parallel wiring was not as officiant (I mean max. volume) as all parallel.

[Aura Audio]

Can you post a frequency graph of the dipole 15 for me please in 4 ohms and 8 ohms.
I'd like to know where it lies at 30hz and what the max. volume the driver will play to 30hz.

Yes, the question is it's max volume at 30hz and what volume will it be playing at 100hz.

[simon5]

Thank you Simon, I understand that totally and its as I thought but is it not better to wire everything in parallel?
If two drivers were to be used for each channel which way would net the most efficiency with best sound if the amp used was stable in 2 ohms?
I have always thought that series parallel wiring was not as officiant (I mean max. volume) as all parallel.

Well people use all parallel because most amplifiers will deliver more power when you go lower in impedance, that's why it's better to parallel than series usually.

But, other than that, no real gain. If the amplifier is tuned for a certain impedance load, it is tuned for that load, so putting two woofers in parallel, so 4 ohms, on a 16 ohms amplifier will result in lower SPL than putting them in series to better match the output impedance of the amplifier.

[simon5]

Can you post a frequency graph of the dipole 15 for me please in 4 ohms and 8 ohms.
I'd like to know where it lies at 30hz and what the max. volume the driver will play to 30hz.

Yes, the question is it's max volume at 30hz and what volume will it be playing at 100hz.

Unfortunately, I have no frequency graph for a Dipole15, I will ask John if he can make one. At 4 ohms and at 8 ohms it will have the same graph anyway.

You want to know about 30 Hz SPL in open baffle use ? That's a bit hard to tell, you need to know baffle width, baffle height, etc... Did you try "The Edge" ?

[Aura Audio]

I understand your answers to my last questions and think the only way for me to see what I need to see is to get the graph.
Like all drivers are tested,,,,what is it's max volume at 30hz and what volume will it be playing at 100hz at the same max volume, forget about the baffle size, measured like all others are (open/no baffle I think).
I know the baffle is everything but I need to know if this is the driver for me.

Thanks again,
Ron

[simon5]

All drivers are usually measured on an infinite baffle.

Max SPL at 100 Hz will depend on the room, but with 200W input it will be 113 dB, let say 119 dB corner loaded.

At 30 Hz it's excursion limited to about 108 dB SPL or 114 dB corner loaded.