Dual Voice Coil Subs

[dano]

Many years ago I purchased some Madisound brand dual voice coil 12" subs.They were good subs for their time. However I didn't think they sounded as good wired in series. If separate subs are wired in series the back emf of the subs can modulate each other and might change their sound. However with dual voice coil subs the voice coils are mechanically connected so this shouldn't happen. Also when dual voice coils are wired in series I think the only thing that changes is the impedance and the Le. This shouldn't change the design parameters,or the sound character of the subs other than how loud they sound at the same applied voltage. Has anyone here noticed any change in the sound quality with dual voice coil subs wired in series?


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[Wolf]

Actually- it can change the parameters enough to make them prefer a sealed box over a vented box or vice versa. I believe normally the series-wiring is the one that would prefer a sealed volume, but it's been awhile since I've looked at Ray Alden's first book..."Advanced Speaker Systems". You'd be surprised what changes.
Later,
Wolf

[dano]

So I wasn't just hearing things. What parameters does it change?
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[Wolf]

So I wasn't just hearing things. What parameters does it change?

Like I said- it's been awhile...
I'm sure there is a tech document on the web somewhere...but I'm coming up nil. There WAS one on Geocities, but it's gone now.
Later,
Wolf

[Chris Roemer]

Like I said- it's been awhile...
I'm sure there is a tech document on the web somewhere...but I'm coming up nil. There WAS one on Geocities, but it's gone now.
Later,
Wolf

I'm pretty sure that the "big change" in parms is in running only a single coil, or running both coils. Running both coils (whether in series or parallel) should keep the box parms the same (Vas, Qts, Fs).

Chris

[ocool_15]

I have done some measurements and series or parallel didn't make any significant difference.
If you power one coil and place a resistance across the other you can vary qts to from close to both coils qts to ~double.

[Jeff B.]

Many years ago I purchased some Madisound brand dual voice coil 12" subs.They were good subs for their time. However I didn't think they sounded as good wired in series. If separate subs are wired in series the back emf of the subs can modulate each other and might change their sound. However with dual voice coil subs the voice coils are mechanically connected so this shouldn't happen. Also when dual voice coils are wired in series I think the only thing that changes is the impedance and the Le. This shouldn't change the design parameters,or the sound character of the subs other than how loud they sound at the same applied voltage. Has anyone here noticed any change in the sound quality with dual voice coil subs wired in series?

Everything you said here is correct. All T/S parameters will remain the same between parallel and series wiring of the coils. The only changes will be Re, Le, and the sensitivity. Maybe the sensitivity difference and how hard you pushed your amp is what you are hearing.

[dano]

Thanks for your replies. I know what I was hearing now. I was listening for the timber or the tonal characteristic of the sub. A pseudo frequency and harmonic distortion test if you will. Unfortunately I was running the sub full range without a crossover. When I wired the sub in series it sounded duller and lifeless. I now know this was because of the inductance increase.This caused a quicker roll off in the higher frequencies. I think this is a good lesson. When evaluating the sound quality of a speaker we should listen to it in the pass band its intended to play in.
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[daryl]

The significance of Le will be the same either way.

It does not matter that Le is four times greater with a series connection vs. parallel because all of the drivers other impedances are also four times greater giving the driver the same characteristics with either connection.

The difference is that impedance has been multiplied by four.


Thanks for your replies. I know what I was hearing now. I was listening for the timber or the tonal characteristic of the sub. A pseudo frequency and harmonic distortion test if you will. Unfortunately I was running the sub full range without a crossover. When I wired the sub in series it sounded duller and lifeless. I now know this was because of the inductance increase.This caused a quicker roll off in the higher frequencies. I think this is a good lesson. When evaluating the sound quality of a speaker we should listen to it in the pass band its intended to play in.

[Wolf]

Thanks,
Wolf

[dano]

Thanks Daryl your right. The frequency response is the same either way.
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