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Old 5th February 2009, 12:21 AM   #1
Fanuc is offline Fanuc  United Kingdom
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Default Some questions on dual voice coil woofers

Hello,

I was wondering what the advantages and disadvantages of DVC woofers are compared with normal ones. I know it let's you set different impedances etc. Do they suffer from having more moving mass than a normal woofer. ?

Can you still get the very low frequencies of the driver wired in 16r mode ? or would that have to be in 4r paralel mode? I wondered if the power would be halfed in 16r series mode but I can stiill get the really low LF.

Actually the DVC woofers is for a motional feedback design that is in a sealed box. Basically I want a critically damped low Q subwoofer sealed with excellent transient response. Maybe a compound arrangement to boost the LF under 100HZ.

Best Regards

Kevin
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Old 5th February 2009, 06:17 PM   #2
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Well, I'm not expert, but I think the advantage is - flexibility. That is, flexibility in how the speakers can be configured.

A given driver can be either 4 ohms total or 16 ohms total. That mean you can combine two 4 ohms in series and have 8 ohms total, or better yet, you can combine two 16 ohms in parallel and have 8 ohms total.

A parallel configuration would give you a boost in the output levels that a series configuration would not.

This is the only way you can have two woofers in parallel and end up with an 8 ohm total impedance.

Now some people claim that you can use dual voice coil woofers for a Subwoofer, and put one stereo channel on each voice coil on the assumption that the electrical/magnetic signals will combine into a composite signal. I'm not sure how workable that configuration is in reality, but none the less some people do it with Dual Voice Coil speakers.

Other than the flexibility with the resulting impedance, I don't think there are any advantages or disadvantages to DVC speakers.

But again, I'm no expert.

Steve/bluewizard
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Old 5th February 2009, 08:55 PM   #3
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I have also thought about using the second voicecoil as feedback but there are two problems: The first is that using only one voicecoil gives only half the motor power and half the power carrying capacity and secondly; the field from one coil will interact with the field from the other coil and distinguishing the back-emf due to movement from interaction with the driving coil would not be possible.

Using a DVC driver with one amplifier per coil should be OK if both amps are identical (overall gain and power equal and fed from a common signal). I would not drive the 2 coils with different signals (such as L/R from a stereo feed) because on the off chance a song had out of phase LF signals (eg. mastered from a warped record) then the two channels would be fighting with each other making the speaker appear more reactive and possibly overstressing the amps. Given most speaker have very low electrical efficiency (4 ohm speakers measure 3.5-4 ohms at dc) this may not be too much of a problem, still, it doesn't sound like a good idea.

Further to your question of efficiency, most DVC drivers are for car audio applications where the intention is to have as low a frequency extension as possible with the smallest box possible. To achieve this weak motors are used with heavy moving parts and a stiff surround. The efficiency is low as a result of these compromises. The mass of the extra two braided wires and structure to support them are inconsequential in this case. I have not ever seen any high efficiency drivers (Sound Reinforcement for PA systems as an example) that have dual voice coils.
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Old 5th February 2009, 09:32 PM   #4
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Quote:
Originally posted by BlueWizard
Well, I'm not expert, but I think the advantage is - flexibility. That is, flexibility in how the speakers can be configured.

A given driver can be either 4 ohms total or 16 ohms total. That mean you can combine two 4 ohms in series and have 8 ohms total, or better yet, you can combine two 16 ohms in parallel and have 8 ohms total.

A parallel configuration would give you a boost in the output levels that a series configuration would not.

This is the only way you can have two woofers in parallel and end up with an 8 ohm total impedance.

Now some people claim that you can use dual voice coil woofers for a Subwoofer, and put one stereo channel on each voice coil on the assumption that the electrical/magnetic signals will combine into a composite signal. I'm not sure how workable that configuration is in reality, but none the less some people do it with Dual Voice Coil speakers.

Other than the flexibility with the resulting impedance, I don't think there are any advantages or disadvantages to DVC speakers.

But again, I'm no expert.

Steve/bluewizard
I understand that trying to hook up a stereo signal to each VC on a DVC subwoofer is a very bad idea, the concept being that there will be different signals getting sent to each VC, to however much degree. the voice coils are meant to work together, recieving identical signal.
DVC is a benifit for only flexibility, as bluewizard suggests.
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Old 5th February 2009, 11:58 PM   #5
Ron E is offline Ron E  United States
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Quote:
Originally posted by soundemon
I understand that trying to hook up a stereo signal to each VC on a DVC subwoofer is a very bad idea, the concept being that there will be different signals getting sent to each VC, to however much degree. the voice coils are meant to work together, recieving identical signal.
It doesn't matter that they are receiving different signals. Doing stereo bass into a DVC is fine. It is a bit of a waste of power, as the power in out of phase signals will just fight each other and make no sound.

Many older recordings are effectively mono in the bass anyway, from what I understand.
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