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Old 3rd June 2009, 02:50 PM   #1
Dr_EM is offline Dr_EM  United Kingdom
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Default Multiple driver connection, impedance

Hi, probably an easy question for some of you but something I can't be sure of!

I'll start with a link to the driver in question:

http://www.monacor.de/typo3/index.ph...pr=EN&typ=full

but the important parameter is the 2x8ohm voice coils.

Say I want to wire up 4 of these drivers, which at some point I intend to. If I only had 1 amplifier capable of driving a 4ohm load, I can create an ideal load with these drivers by connecting each dual voice coil unit as parallel (4ohm each), then a series parallel combination to get 4ohm overall.

What concerns me is the series connection of 2 drivers. By doing this, does each driver essentially see a 4ohm series impedance, thus reducing effective damping factor to 1? This would not be an ideal situation for subwoofers!

Ideally I'd have 4 amps driving a 4ohm connected DVC driver each, but this is expensive.

Any thoughts?
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Old 3rd June 2009, 04:37 PM   #2
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You could also connect the coils of each DVC driver in series for a 16 ohm driver, then parallel all 4 to get back to a 4 ohm load.

According to JL Audio, series connections between subs can create distortion. Additionally, the effective Thiele-Small parameters of the DVC drivers will change due to the wiring of the voice coils (single, series, or parallel), be sure to account for this in your enclosure design.
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Old 3rd June 2009, 04:53 PM   #3
Dr_EM is offline Dr_EM  United Kingdom
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Thanks for your input!

Perhaps that is the best way then, I just thought any series connection was bad, but I guess if the voice coils are both integral to the speaker it'd be the same as a 16ohm driver?

My "enclosure" will actually be a pair of W-Profile open baffles; hence the need for so much driver area . Combined with active EQ these should work well, I've seen measurements from some used this way and they are impressive! Strangely, the drivers don't seem that useful for much else, always give a peaky response in enclosures.
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Old 3rd June 2009, 05:10 PM   #4
tinitus is offline tinitus  Europe
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Quote:
Originally posted by littlemike

Additionally, the effective Thiele-Small parameters of the DVC drivers will change due to the wiring of the voice coils (single, series, or parallel), be sure to account for this in your enclosure design.
Not sure its significant
I believe there should be only major change in Qts if only one of the two voice coils of a single driver is used

You could consider two boxes with each 2 drivers
They could still be driven by the same amp
But you will have the oppertunity of later on buying another amp
In case of that I would make sure to get one that can drive 2ohm properly fore best result
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Old 3rd June 2009, 09:38 PM   #5
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Oops!



I stand corrected - I just checked measurements of a DVC woofer I took recently, the biggest changes are when only a single coil is driven. The basic parameters (Qts, Vas, and Fs) are all within the error bounds of my measurement technique regardless of series or parallel wiring of the coils.

Some of the other parameters (Le, BL) are significantly varied by series vs parallel wiring of the coils, though these parameters are less significant for the design of a conventional enclosure. This must have been what I was remembering, as most of my simulations have been done in hornresp lately.

I am sorry for any confusion I have caused, and a very big thank you to tinitis for catching and pointing out my error.
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Old 3rd June 2009, 09:44 PM   #6
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Series between the coils of the same driver is fine. This will double the impedance of the driver and increases the inductance and BL of the driver when compared to parallel wired coils.

None of this really matters for open-baffle use, just get your target impedance and polarity of the wiring between the drivers and coils correct, things should be fine.
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