8 Ohm vs 2 Ohm Wiring

[tjcinnamon]

I have a Crown XLS 2002 on sub duty. The drivers are 4 Ohm dual voice coil so my wiring options are 2 ohm or 8 ohm. The drivers can handle 700W RMS. The amp delivers 375W into 8 ohms and 1150W into 2 ohms.
Is there any difference in total SPL as a result of impedance? Are there other differences related to distortion? Or does it really come down to “taxing the amp”?

 

[Slayer]

Wire the subs for 2ohm. You will have more headroom from the amp and be less likely to clip. If you wire at 8ohm, you will never get full potential spl from the subs, and it will be much easier to clip the signal from your amp.
A good rule of thumb is to have 1.5 to 2 X the power required for your drivers. Prevents clipping and less stress on the amplifier. You are setting perfect if you wire at 2ohms at 1.5 times the power.

 

[tjcinnamon]

That makes sense. I posted something like this on AVS a year or so ago and got different responses. Based on my amp available, I wish I would have gotten this advice because I would have selected 2 ohm drivers

 

[Speedskater]

I would think that just driving a 2 Ohm load would be very demanding on any amplifier.

 

[sergeauckland]

Furthermore, unless the subwoofer cables are very short, driving into 2 ohms will require very thick cables, much less so with an 8 ohm setting.

The main difference between series (8 ohms) and parallel (2 ohms) wiring is whether you're more likely to be voltage limited or current limited.

Judging by the difference between the 8 ohm and 2 ohm power delivery of your amplifier, it would seem you're more current limited, so I would wire for 8 ohms. If you're clipping the amplifier, then possibly think again, but otherwise, as long as the clip light stays off, that's what I would do.

S.

 

[tjcinnamon]

Furthermore, unless the subwoofer cables are very short, driving into 2 ohms will require very thick cables, much less so with an 8 ohm setting.

The main difference between series (8 ohms) and parallel (2 ohms) wiring is whether you're more likely to be voltage limited or current limited.

Judging by the difference between the 8 ohm and 2 ohm power delivery of your amplifier, it would seem you're more current limited, so I would wire for 8 ohms. If you're clipping the amplifier, then possibly think again, but otherwise, as long as the clip light stays off, that's what I would do.

S.

I have an Art clean box which I believe adds a ton of current. It converts unbalanced to balanced. The gain on it is violent

unless I’m interpreting current incorrectly.

clip light is when it goes red, correct?
Also, is 12AWG thick enough?

 

[LTig]

I would think that just driving a 2 Ohm load would be very demanding on any amplifier.

This is correct but the amp is specified for 2 Ohms so it should be OK.

 

[LTig]

Furthermore, unless the subwoofer cables are very short, driving into 2 ohms will require very thick cables, much less so with an 8 ohm setting.

This might be a case where biwiring makes sense. The OP should lead both voice coils to separate connector pairs. Helps also to change from 2 to 8 Ohm and back without hassle.

The main difference between series (8 ohms) and parallel (2 ohms) wiring is whether you're more likely to be voltage limited or current limited.

Judging by the difference between the 8 ohm and 2 ohm power delivery of your amplifier, it would seem you're more current limited, so I would wire for 8 ohms. If you're clipping the amplifier, then possibly think again, but otherwise, as long as the clip light stays off, that's what I would do.

S.

I'd say the amp is voltage limited because 375 W is much less than 1150 W.

 

[sergeauckland]

I have an Art clean box which I believe adds a ton of current. It converts unbalanced to balanced. The gain on it is violent

unless I’m interpreting current incorrectly.

clip light is when it goes red, correct?
Also, is 12AWG thick enough?

The ART box converts unbalanced to balanced. It does nothing for a power amplifier's output current capability, which is dependant on the power amp's design. Gain on the ART box is also adjustable, and has also nothing to do with the power amp's current driving ability.

As to the clipping indicator, the Crown amp has a clipping indicator that lights when it reaches its maximum output on each channel. As long as that doesn't light, then there's enough output from the Crown amp.

S

 

[sergeauckland]

This might be a case where biwiring makes sense. The OP should lead both voice coils to separate connector pairs. Helps also to change from 2 to 8 Ohm and back without hassle.

I'd say the amp is voltage limited because 375 W is much less than 1150 W.

I'd say the amp is current limited because if it wasn't, the output into 2 ohms would be a lot closer to 1500 W. If 375 W into 8 ohms is enough to avoid clipping the amp, then that's the way I'd use it. If the amp gets clipped regularly into 8 ohms, then perhaps try the 2 ohm wiring and see if that's any better.

S.

 

[LTig]

I'd say the amp is current limited because if it wasn't, the output into 2 ohms would be a lot closer to 1500 W. If 375 W into 8 ohms is enough to avoid clipping the amp, then that's the way I'd use it. If the amp gets clipped regularly into 8 ohms, then perhaps try the 2 ohm wiring and see if that's any better.

S.

I understand your view but I can guarantee you that the amp will clip at a much lower power when feeding the 8 Ohm configuration due to not enough voltage, than when feeding the 2 Ohm configuration due to not enough current.

 

[MrPeabody]

Wire them in parallel if, but only if, you really, really, really, really are certain that with them wired in series you hear clipping distortion, or else the volume isn't loud enough. If the volume is as loud as you want and you do not hear anything that sounds like amplifier clipping distortion, then you have no reason to wire them in parallel. [EDIT: I had to edit this and change that last word to parallel because I had suffered brain flatulence and had written series when I should have written parallel. Dammit.]

A given level of acoustic loudness (SPL) implies a corresponding level of acoustic power (even though the relationship between SPL and acoustic power is not linear), which means that for a given SPL (perceived loudness), you need a specific value for V x I. Power is also equal to V^2 / R. If they are wired in parallel, R is calculated (4 x 4)/(4 + 4) = 2; if they are wired in series R is 4 + 4 = 8. Since the ratio for R for the two alternatives is 8/2 = 4, this means that the ratio for V^2 will likewise be 4, and that the ratio for the amplifier output voltage will be 4^(1/2) = 2. Thus, for a given SPL (loudness), amplifier output voltage will be twice greater for series compared to parallel, whereas current will be twice greater for parallel compared to series.

If you decide that when wired in series the volume isn't as loud as you like when you can hear the amplifier clipping (or else it is clean but the gain control is fully up and it still isn't loud enough), then you wire in parallel, so that only half as much voltage is needed for a given loudness level. Current will be twice as great as it would be with series, and if this is a problem, the way that you will know that it is a problem is that the amplifier will get too hot and will shut down. Instead of shutting down completely it might do something else that will lower the output voltage in order to lower the current, but if it does this, it will not be subtle. In the worst case scenario you'll see smoke coming out it or you'll get a mild burn when you accidentally bump up against it. But you do not need to be concerned that sound quality is affected by the amplifier not being able to supply the amount of current implied by the output voltage in conjunction with the load impedance.