Subwoofer mixed impedance question.

aceinc

Member
2007-05-11 5:18 am
I want to use two identical DVC woofers in a single plate amp powered sealed sub enclosure. Each of the voice coils is rated at 2 ohms. If I configure things symmetrically I can get;

0.5 ohms (everything parallel)
2 ohms (coils series and woofer parallel or vice versa)
8 ohms (everything series)

The amp isn't rated for less than 4 ohms. At 8 ohms I leave some power on the table I think.

My question is what would the impact be if I were to wire one woofer's VCs in series, one woofer's VC in parallel and the two woofers in series?

I do not have the experience to guess at the outcome.

What impedance would the amp see?

How would having one woofer running at 1/4 the impedance of the other impact power handling?

If the parallel VC woofer would push more air at a lower power level, would the other woofer's cone travel stop?

I profess total ignorance, and am rather curious.
 

aceinc

Member
2007-05-11 5:18 am
3 ohms which is still too low, and 1 driver would do most of the work so there is no point to this arrangement, just wire everything in series and call it good.

If I wire woofer's VCs 1 parallel I would get 1 ohm the other woofer's VCs series I would get 4 ohms and then the two woofers in series wouldn't that be 5 ohms?

I am still concerned about the imbalance and whether the high impedance woofer would contribute much if anything to the sound.
 
Power to "leave on the table....". Guessing, you prolly have lots of power to spare. So go with 8 Ohms in series.

Amps operate at a certain voltage. Their power supplies can pump out current into different loads until they are forced to compromise their output ability when the power demand gets high. So lower impedance speakers harmonize with that design better than higher impedance and just how much "free lunch" depends on the amp circuit. But the higher impedance speakers work just fine and might be safer for your plate amp.

B.
 

academia50

Member
2013-01-16 2:52 pm
I will put my spoon here.
Is the OP amplifier supposed to be a conventional board - class AB - or a class D board amplifier?

In class D amplifiers, can we use the same criteria (calculations) for the correct load impedances as in a conventional class AB?

I would believe that they must be different, that a class D amplifier when working switched like the PSUs of a computer, have higher tolerances at low loads, even Bheringer has developed "Impedance Compensation - SmartSense" technologies


NX3000D | Portable | Power Amplifiers | Behringer | Categories | Music Tribe - Behringer)
 

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aceinc

Member
2007-05-11 5:18 am
I will put my spoon here.
Is the OP amplifier supposed to be a conventional board - class AB - or a class D board amplifier?

In class D amplifiers, can we use the same criteria (calculations) for the correct load impedances as in a conventional class AB?

I would believe that they must be different, that a class D amplifier when working switched like the PSUs of a computer, have higher tolerances at low loads, even Bheringer has developed "Impedance Compensation - SmartSense" technologies


NX3000D | Portable | Power Amplifiers | Behringer | Categories | Music Tribe - Behringer)

For sake of this post, let's assume this class D amp;

Dayton Audio SPA1200DSP 1200W Subwoofer Amplifier with DSP
 

conanski

Member
2013-03-31 3:53 am
If I wire woofer's VCs 1 parallel I would get 1 ohm the other woofer's VCs series I would get 4 ohms and then the two woofers in series wouldn't that be 5 ohms?

I am still concerned about the imbalance and whether the high impedance woofer would contribute much if anything to the sound.

You are right there I messed up the total impedance calculation. But with the two drivers in series you have created a voltage divider where 4/5 of the voltage the amp generates appears across the 4ohm driver and 1/5 across the 1ohm driver, this means the 4ohm driver does most of the work(dissipates most of the power) and the other wouldn't even be audible, thus there is no point to this arrangement.

And in case this is your next question, using resistors to balance the load doesn't help, the extra power going to the 1ohm driver side is just wasted as heat at the resistors and makes no difference to sound output.
 
In class D amplifiers, can we use the same criteria (calculations) for the correct load impedances as in a conventional class AB?

I would believe that they must be different, that a class D amplifier when working switched like the PSUs of a computer, have higher tolerances at low loads, even Bheringer has developed "Impedance Compensation - SmartSense" technologies
Both conventional class AB and class D work according to Ohm's law, and both generally use current limiting to protect output devices from over-current failure when driven into loads below rated impedance.

Class D uses an output LC filter (inductor/capacitor) to tame EMI (electro magnetic interference), the circuit needs to be "tuned" to the nominal impedance driven, or VHF (very high frequencies above 10kHz) response will slightly rise above "flat" response with higher impedance, or droop with lower impedance.
Behringer's "Impedance Compensation - SmartSense" probably mitigates the LC filter problem, but that won't have any bearing on the impedance the amplifier can handle without current limiting. The NX3000D example you mentioned has exactly the same rated output at different impedance loads as the NU3000 (without "Impedance Compensation - SmartSense") it replaced.

The NX3000D weighs .3kg (.9 lb) more than the NU3000, perhaps the "Impedance Compensation" circuit switches between various LC components depending on HF impedance sensed.
 

aceinc

Member
2007-05-11 5:18 am
You are right there I messed up the total impedance calculation. But with the two drivers in series you have created a voltage divider where 4/5 of the voltage the amp generates appears across the 4ohm driver and 1/5 across the 1ohm driver, this means the 4ohm driver does most of the work(dissipates most of the power) and the other wouldn't even be audible, thus there is no point to this arrangement.

And in case this is your next question, using resistors to balance the load doesn't help, the extra power going to the 1ohm driver side is just wasted as heat at the resistors and makes no difference to sound output.

No that wasn't my next question because "Resistance is futile." I felt that the impedance differential would cause the one woofer to do most of the work and the other very little, but I am not an EE, so I need to ask.
 
Both conventional class AB and class D work according to Ohm's law, and both generally use current limiting to protect output devices from over-current failure when driven into loads below rated impedance.

Class D uses an output LC filter (inductor/capacitor) to tame EMI (electro magnetic interference), the circuit needs to be "tuned" to the nominal impedance driven, or VHF (very high frequencies above 10kHz) response will slightly rise above "flat" response with higher impedance, or droop with lower impedance.
Behringer's "Impedance Compensation - SmartSense" probably mitigates the LC filter problem, but that won't have any bearing on the impedance the amplifier can handle without current limiting. The NX3000D example you mentioned has exactly the same rated output at different impedance loads as the NU3000 (without "Impedance Compensation - SmartSense") it replaced.

The NX3000D weighs .3kg (.9 lb) more than the NU3000, perhaps the "Impedance Compensation" circuit switches between various LC components depending on HF impedance sensed.


Thank you weltersys for your response, much appreciated.:)
 
Hi.
How about leave 1 voice coil unused on each driver leaving each driver with 1 -(2) ohm coil, then wire both of those in series providing a 4 ohm load to the amp.
You won't be able to push full power into them but it'll be quite usable.
Another thing, if you happen to burn the first coils you have a spare set ;)... maybe.
 
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aceinc

Member
2007-05-11 5:18 am
Hi.
How about leave 1 voice coil unused on each driver leaving each driver with 1 -(2) ohm coil, then wire both of those in series providing a 4 ohm load to the amp.
You won't be able to push full power into them but it'll be quite usable.
Another thing, if you happen to burn the first coils you have a spare set ;)... maybe.

That brings up a question I've thought about, but never asked. "What is the impact of using only one VC in a DVC woofer?"