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Old 10-14-2003, 05:56 PM   #1 (permalink)
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whats are ohms in amp?

i wanna run a 1300watts 12" Audio bahn Dual 4 Ohm subwoofer. Prob is....
WTF is ohms, the sub can run at only 2 Ohm or 8 Ohm Operation, but my amp can only run at 750watts at 4 ohms or at 1 ohm @ 1000watts.

anyone have any ideas on ohms and dual coils?

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Old 10-14-2003, 06:01 PM   #2 (permalink)
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what kind of amp you have?
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Old 10-14-2003, 06:14 PM   #3 (permalink)
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i'm deffinately no audio buff, but here's my understanding of it

ohm's are the amount of resistance, or 'impedence'. its just a average rating, it wont run constant at the given impedence but will still only have about a +/- 1ohm difference from the rating at a given time. for instance 2ohms gives less resistance than 4ohms, and 8ohms is less resistance than 16, etc.

if you have a 4ohm amp you need to somehow get your speakers or subs to match it as close as possible, and there are 2 types of ways you can wire it, series or parallel. i cant remember which one does which but say your subs are 2ohms a piece, you can wire it to where you can keep both at 2ohms or wire it to where you can combine the ohms (2ohms a piece + 2subs) would equal 4ohms, 4 subs would yeild 8ohms etc.

i would think it would be safer (if the amp was running on 4ohms) to run the subs at 8ohms, which would reduce power output (almost by half) but keep the amp from overheating. and i dont think it is possible to change the factory amp ohm settings

my knowledge on this is very limited, and i only know what i know so far from experience with guitar amps and cabs so it may be a little different for car audio.
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Old 10-14-2003, 06:21 PM   #4 (permalink)
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here's a couple diagrams i was able to find on series and parallel setups...
oh and to correct what i just said, series will multiply impedence times the number of subs/speakers (4ohms x 2subs)=8ohms. and parallel will divide the impedence by ohms (4ohms / 2subs)= 2ohms

series:


parallel:
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Old 10-14-2003, 06:26 PM   #5 (permalink)
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adonis is running a DVC setup though. so you would treat those 2 speakers as one.
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Old 10-14-2003, 07:00 PM   #6 (permalink)
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Wire both voice coils up in parallel for 2ohm operation. As long as your amp is capable of running at 1ohm, you'll have no problem.

Make sure you are using no less than 4 guage power wire directly from the battery to the amp and fuse it at the battery. Also, be sure your ground wire is the same guage as your power wire and it makes a good ground.

If you plan on using all the amp's resources then you'll need to upgrade your alternator and go with no less than 2 guage power wires to the amp.

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Old 10-15-2003, 04:56 PM   #7 (permalink)
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thanks for the replys guys.
I went to see my mate today (audio buff) he told me my amp can run 4 of them Audio bahn subs at 1ohm LOL
The Amps Vibe Digital VP4 1200 RMS, Vibes pretty decent ICE company over here in the UK.
Isnt parallel called Bridged (bridgeable)? or is that just over here?
neways thanks for the help guys
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Old 10-15-2003, 05:13 PM   #8 (permalink)
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Quote:
Originally posted by adonis_bimmer@Oct 15 2003, 05:36 PM
Isnt parallel called Bridged (bridgeable)? or is that just over here?
Actually, bridging refers to the amp itself. It's when you take a two channel output and use it as one output. Some amps have a switch that must be set and some do it automatically -- but not all amps have this capability so don't hook it up this way if it's not specified in the manual.
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Old 12-08-2003, 10:57 PM   #9 (permalink)
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If it is a DVC sub than you can still run is as either parralel or series- I used to run my JL12W6 that way, bridged in parralel.

Anytime you run two voice coils in parralel, you are effectively halving the ohmage: example- if you took two 4 ohm voice coils and ran them in parralel, your amp would see a 2 ohm load (4 / 2) if you ran it in series it would see an 8 ohm load. ( 4 x 2 )

Alot depends on what your amp can handle and how clean you want your bass to sound. When you bridge 2 amp channels together, you ARE NOT halving the ohmage, that has nothing to do with the amp- ohmage is derived from the speaker. However, if you bridge an amp into mono, you're inherently going to get more power or current out of it- it is more demanding on the amp and also takes away from sound quality. Asking an amp to drive a power-hungry DVD sub set up as a 2 ohm mono load (running your amp bridged and then wiring the two voice coils in parralel) can be very demanding on any amp- it will also likely run hot and your output will suffer in terms of quality. I used to run my 12W6 with a ZR240 bridged in parralel- it was getting about 180 per coil, and even though it was in a sealed enclosure of 1" MDF (yes, 1 inch, not 3/4) it was not as accurate as I would have liked! 1 reason is because JL's aren't very accurate, but the bridged/parraleled setup didn't help sound quality. I ran a seperate channel to each voice coil and set the source to mono and it helped keep soudn quality real clean and the sub still had nice output in terms of dB.

It all depends on what you're going for. IF you have any idea of what you're doing than you should know there's alot more to systems than watts - or just number on paper. But even if you know nothing about how sound and systems function, all you need to know is what you intend to do- do you want sound quality (SQ) or do you want it to be loud and not give a shit about sound quality??? Let us know and you'll get the most appropriate advice given what gear you have

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Old 12-09-2003, 06:48 AM   #10 (permalink)
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Quote:
Originally posted by MrM3@Oct 14 2003, 05:54 PM
i'm deffinately no audio buff, but here's my understanding of it

ohm's are the amount of resistance, or 'impedence'. its just a average rating, it wont run constant at the given impedence but will still only have about a +/- 1ohm difference from the rating at a given time. for instance 2ohms gives less resistance than 4ohms, and 8ohms is less resistance than 16, etc.

if you have a 4ohm amp you need to somehow get your speakers or subs to match it as close as possible, and there are 2 types of ways you can wire it, series or parallel. i cant remember which one does which but say your subs are 2ohms a piece, you can wire it to where you can keep both at 2ohms or wire it to where you can combine the ohms (2ohms a piece + 2subs) would equal 4ohms, 4 subs would yeild 8ohms etc.

i would think it would be safer (if the amp was running on 4ohms) to run the subs at 8ohms, which would reduce power output (almost by half) but keep the amp from overheating. and i dont think it is possible to change the factory amp ohm settings

my knowledge on this is very limited, and i only know what i know so far from experience with guitar amps and cabs so it may be a little different for car audio.
thats pretty much ohms law
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Old 01-02-2004, 12:19 AM   #11 (permalink)
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Amps dont have ohms or resistance.. Amps are output devices, they are designed to be ran with a certain "load" on them (resistance)

Many modern amps run at 1 - 100(ex) ohms. Some even going less than 1.
If it is a regulated amp that is stable down to 1ohm there wont be a problem with heat and degraded sound quality because the circuitry does not allow the amp to increase it's power because of less resistance (ex: JL Audio amps)

Now if your amp is 200w @ 4ohms, 400w @ 2ohms, running at 2 ohms will cause some sound quality loss and the amp will get hot, but it will be fine. The sound quality lost (to most people) is inaudible, however. While the power difference is definitely noticeable.

A simple way to determine the resistance in a chain of speakers is this:
Assuming all of the speakers (or voicecoils) in the chain have the same resistance..
If the setup is in parallel, divide the resistance of the speakers (or voicecoils) in the chain bye the amount of the speakers (or voicecoils). (ex: 4 (2ohm) voicecoils in parallel would be 2 / 4 = 1/2 or .5 - the load is one half of an ohm)
If they are connected in series, simply multiply the number of speakers (or voicecoils) by the resistance of each (ex: 4 (2ohm) voicecoils in series would be 4 x 2 = 8, the load would be 8ohms.)

That is just a simple way and it could be totally innaccurate of some combination of series / parallel was used or if the load is bridged and you dont account for that or if one of the voicecoils is different than the other. (NOT recommended)

Running a sub in a chain with a different resistance than the other subs is a very bad idea, and will cause a loss in sound quality. The sub with the different resistance will cause the power distribution to be messed up and the subs will work with different levels of power, possibly even causing cancellation (leading to LOSS of bass)

A lot of this info is probably useless, but i figure it might help someone out. If theres anymore questions or you want something explained in detail, let me know and ill post it up.
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