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convert powered sub to passive by bypassing internal xover/amp?


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4 replies to this topic

#1 of 5 OFFLINE   sammy segask

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Posted November 04 2006 - 12:21 PM

I have an 10 year old Boston Acoustics VR500 subwoofer. 10 inch 100 watts. Has worked great over the years, but just this week it has started to blow fuses (2A 250V). Put two new fuses in and they both blew as soon as I turned power on. I unscrewed the amp/crossover/input module from the back of the cabinet to take a look inside. Didn't see anything burned or melted out inside. My receiver has SUB/LFE out and I have a spare 100 watt Carver amp. Can I bypass the built in amp/crossover by doing the following?:

1. plug SUB/LFE out from my receiver to my spare 100 watt Carver amp, then
2. connect speaker output from my spare 100 watt amp directly to + and - terminals of the subwoofer cone inside the cabinet?

Would that work? Or would I blow up my amp and/or the subwoofer cone? Do I have to add things like resistors and capacitors inbetween the amp output and the terminals on the subwoofer cone?

#2 of 5 OFFLINE   Wayne A. Pflughaupt

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Posted November 04 2006 - 02:36 PM

Quote:
1. plug SUB/LFE out from my receiver to my spare 100 watt Carver amp, then
2. connect speaker output from my spare 100 watt amp directly to + and - terminals of the subwoofer cone inside the cabinet?

Would that work?
Yep – that’ll do it. Posted Image

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#3 of 5 OFFLINE   RichardH

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Posted November 06 2006 - 07:43 AM

The frequency response is likely to be different, the largest difference being low end extension. But, since you already have the spare amp, might as well get your sub working again.

Also, you may need something to attenuate the sub-out signal if your Carver amp doesn't have a trim control on the input.

#4 of 5 OFFLINE   chuckg

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Posted November 06 2006 - 07:59 AM

I did almost exactly the same thing with a sub that had a dead internal amp. there's really no difference between an internal amp, and an external one except for a couple of extra goodies like low pass filter, and phase switch. I needed neither, so i'm good.
--ignore the man behind the curtain

#5 of 5 OFFLINE   John Garcia

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Posted November 06 2006 - 08:04 AM

Well, it depends on whether the old amp had any kind of boost built into it for that particular design. Will it work? Yes, it should. Will it work perfectly? We won't know until you try it Posted Image

I would recommend you run leads from the wires to some binding posts that you insert into the cabinet wall (drill holes) so that you can use whatever amp you like. Like this:

Posted Image
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