Help with DVC sub and multichannel amp - Car Audio Forumz - The #1 Car Audio Forum

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Old 05-02-2004, 02:39 AM   #1
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I wasn't 100% sure where to post so I figured the General forum was safe (gotta hate that first post on a new board)

Question #1:

I thought this was pretty basic but apparently I'm missing something since a salesman at local 'high-end' audio shop stopped short of calling me an idiot today. I always thought that wiring a single DVC sub to an amp would result in the amp seeing a load of either half or twice the impedence of the sub depending if it is wired in series or parallel. So when I was in shopping for an 8" 4Ohm DVC sub I understood that my amp would either see a 2Ohm load (too low for my amp) or 8Ohm load (too high for my liking given my amp). This salesman persisted in saying that my amp (when bridged) would only 'see' half the load and would run like it had a 4Ohm load. Last I checked this doesn't fit with Ohm's law unless I'm missing something here.... is there any way for a single DVC sub to be wired so that the amp sees the load as the rated impedence of the voice coils (ie a 4Ohm DVC gives a load of 4Ohms to the amp)??

Question #2:

Related to #1 of course, can a DVC sub be wired from 2 seperate bridged channels or two seperate amps (1 to each voice coil)? I've found 3 sites online that clearly state it can (eg. Crutchfield and Audiobahn). The aforementioned salesman, when asked, said no this wasn't possible because the movement due to one voicecoil would induce an electrical current in the other (and vice versa) which would be fed back into the amp causing a failure. This struck me as odd but I don't know enough on this topic and it concerns me that most manfacturers sites do not show this as a wiring option (with the exception of Audiobahn).

Basically what I'm looking to do is pick up a single 8" sub and run it off of my existing system. I have two 4 channel amps (Crossfire cfa404 and a cfa404s), 4 channels are of course spoken for with the existing speakers. So I have another 4 channels (50rms each) which can be bridged (100rms each @ 4Ohms). If it is possible to wire up the voice coils of a DVC sub to the two seperate bridged channels then I wouldn't mind doing this.

Any thoughts, comments, etc. would be greatly appreciated!
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Old 05-02-2004, 09:39 AM   #2
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1) A dual 4ohm sub can be wired in series giving a 8ohm load or in parallel giving a 2ohm load.
Now if the amp is bridged that means the amp is seeing half the ohm load meaning if it is bridged at 4ohms the amp is seeing 2ohm. (look at spec sheets for an amp and you will see them rated at say 4ohm mono and 2ohm stereo as lowest possible impedences, this is why).

2)Yes a DVC speaker can be wired to two identical bridged channels or two identical amplifiers. Either way, the channels just have to be carefully gain matched.

3)You can bridge your 4ch amp to a single DVC speaker. The two bridged channels just need to be gain matched. I would however just sell it and get a nice 2ch or mono amp though.
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Old 05-02-2004, 12:28 PM   #3
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1) This is of course exactly what the spec sheet for my amp says, min. load stereo is 2ohm per channel or 4ohm bridged. So really the best option for me with this particular amp would be to find a 2ohm DVC sub (wired in series) or a 8ohm DVC sub (wired in parallel).

2&3) This is pretty much what I suspected but wanted a little confirmation. Of course I wouldn't mind getting a new amp but gone are the days when I get to change my equipment on a regular basis. Besides it took me well over 2 years just to find the bridge piece to go between the two amps. You're right though, a new amp would be the better solution but overkill for what I'm after I suspect.

Thanks so much for your time.
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