Running One VC on a DVC Sub

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haemphyst

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Joined: January 19, 2003

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Posted: August 29, 2007 at 12:47 PM / IP Logged

I don't want to type it all again... (That, and PLEASE use some punctuation, especially commas and periods, and the occasional new paragraph would be helpful as well...)

Read this thread... Another sticky in the forum. Running One VC on a DVC Sub - Page 12 -- posted image.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

proatthagame

Copper - Posts: 65

Joined: April 16, 2006

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Posted: September 17, 2007 at 5:56 PM / IP Logged

This prolly has a real simple answer but.....

Can someone please tell me how to short one of the coils?

Thanks

Yours Truly

DYohn

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Location: Arizona, United States

Posted: September 18, 2007 at 11:42 AM / IP Logged

proatthagame wrote:

This prolly has a real simple answer but.....

Can someone please tell me how to short one of the coils?

Thanks

To short a coil you simply conect a wire from pos to neg. This will change the Q of the speaker, of course...

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proatthagame

Copper - Posts: 65

Joined: April 16, 2006

Location: United States

Posted: September 18, 2007 at 4:44 PM / IP Logged

DYohn wrote:

proatthagame wrote:

This prolly has a real simple answer but.....

Can someone please tell me how to short one of the coils?

Thanks

To short a coil you simply conect a wire from pos to neg. This will change the Q of the speaker, of course...

Thanks, DYohn

Now knowing that....

My amp does 800w bridged. I have two 4 Ohm DVC rated at 400 rms. I want to present a 4 ohm load to my amp. When I hook up one voice coil (shorting the other) on each woofer then bridge the two, I will end up with 8 ohms. According to this diagram ( https://www.the12volt.com/getimage/2_4ohm_svc_8ohm.gif)

So if I present the 8 ohm load to my amp bridged then I will end up with 4ohm correct? Assuming I do, then each speaker should get 400 rms. From Steven's remarks about the power handling not really being cut in half but just dropping a small percentage (10 to 25%). Am I going to be overpowering my woofers? Am I able to do this and just make sure my gain is set properly?

Yours Truly

haemphyst

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Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: September 18, 2007 at 11:07 PM / IP Logged

Yes, you'll be rating your woofers for about 300 to 320 watts, so, yes, you will be overpowering them, technically. Proper setting of the gain, and you'll be fine.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

DYohn

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Location: Arizona, United States

Posted: September 19, 2007 at 9:24 AM / IP Logged

Why do you want to short the unused VC? Are you trying to use a non-standard sized enclosure? Shorting a VC doubled Qms and halves Qes.

If you present an 8-ohm load to your amp you present an 8-ohm load. What amp and again, what are you attempting to accomplish?

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proatthagame

Copper - Posts: 65

Joined: April 16, 2006

Location: United States

Posted: September 19, 2007 at 12:08 PM / IP Logged

DYohn wrote:

Why do you want to short the unused VC? Are you trying to use a non-standard sized enclosure? Shorting a VC doubled Qms and halves Qes.

If you present an 8-ohm load to your amp you present an 8-ohm load. What amp and again, what are you attempting to accomplish?

After reading this....

What about driving just a single coil, and leaving the other open? Well, as you would guess, the push is weaker. The system has a peakier resonance (for the techie types, Qts increases because Qes increases). BUT - let's drive one coil, and short the other. Guess what? Things change from the original (both coils driven) situation, but they also stay the same. The driven voice coil is pushing and pulling, as normal. But what about the shorted voice coil? Well, it's trying to keep things at rest - it's trying to resist ANY motion! The net result is the overall peakiness of the resonance is the same as it was when both coils were driven, even though we are only using half the motor (driving one coil). The other coil helps "tame" the driven coil, so that the system basically behaves the same as before

Kicker kx800.2 - specs - www.realmofexcursion.com/ampguts/Kicker_KX800.2

I was under the impression that when you bridge to the amp, it cuts the impendence in half? Is this correct?

Currently im running to each channel at 2 ohms pushing 400 to each speaker. Its too much for my charging system and myself.

I want to utilize the option of using 1 vc to save the other one incase the one in use blows then i will have another to work with.

I have the option of running 200 to each speaker at 4 ohms but i want more then that. So i figured i would do like mentioned above and get almost the same maybe more power at a higher impemdence thus resulting in the amp not having to work as hard as well as having the other coil available when needed.

Yours Truly

DYohn

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Posted: September 20, 2007 at 8:32 AM / IP Logged

re: "I was under the impression that when you bridge to the amp, it cuts the impedance in half" No, how you connect to the amplifier has nothing to do with the speaker's impedance. If it's 8-ohms it's 8-ohms. Operating a stereo amp bridged into an 8-ohm load generally results in the same power output as the amp's 4-ohm stereo rating. Your Kicker will produce approximately 400 watts bridged into 8-ohms.

Yes, shorting an unused VC results in the same net calculated Qts as using the coil, but the trade off is that Qms doubles, meaning the speaker has twice the mechanical damping it had before and perhaps more significantly the Qes is cut in alf and Le changes in sometimes unknown ways since most manufacturers do not list single coil ratings. All of this means you may need to test the speaker to determine the new T/S parameters as the standard enclosure size will not be optimum and you need to calculate a different size using the changed parameters. Also be sure to de-rate the power handling by about 25%.

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smoothdesignz

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Joined: August 30, 2004

Location: Ohio, United States

Posted: September 23, 2007 at 9:57 AM / IP Logged

I just wanted to pop in and say THANKS!!! for bringing up a huge topic of debate for a lot of people. Unfortunately, I am the one in the position of having to run a single VC or series down to 8 ohms. For those of you that ask "why would you buy it like that?", I didn't, I actually got most of my equipment for free because I did work for someone or traded the free stuff for other things, so I ended up with an Alpine Type-R D4 10" and an Alpine V12 MRT-757 (a two channel for those that don't want to look it up). I did have it running at 2 ohms bridged, but it clipped severely, so, last night I disconnected the second VC and ran it at 4 ohms bridged instead. I will say this in defense, I am planning on getting a second Type-R D4 as soon as the money's right, since we have one at work.

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extacy

Member - Posts: 46

Joined: July 05, 2007

Location: Pakistan

Posted: September 28, 2007 at 5:22 PM / IP Logged

So when you wire up a single VC on a DVC sub ... whats the better option ... short the other voice coil (... done by simple attaching a wire b/w + and - right ?) ... or leave the unused voice coil open ?

What would be the approximate changes for box sizes in both situations ?

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