math: V = I * R. so: R = V/I
in bridging, the amp channels combine. that means 2x voltage. that means 2x current.
so each amp channel provides normal voltage, but 2x current. thus the speaker appears to each channel as being 1/2 the actual value.
note that this is the amp's perspective. the speaker is still a 4ohm speaker.
in bridging, the amp channels combine. that means 2x voltage. that means 2x current.
so each amp channel provides normal voltage, but 2x current. thus the speaker appears to each channel as being 1/2 the actual value.
note that this is the amp's perspective. the speaker is still a 4ohm speaker.
- Thread Starter
- #3
Exactly. And it would appear you are confirming my point. If the amp sees less resistance when speakers are in parallel (bridged), then I would think the minimum Impedance (resistance or Ohm's) should be 2 (not 4) and the minimum when not in parallel (Unbridged) logically should be 4. Just the opposite to what they're posting. So that's what is ocnfusing to me. They must be trying to tell me something else I am not getting!
- Thread Starter
- #4
ocnfusing=confusing =P
well, lets build a amp. give it the ability to put out up to +-12V, +-3A. this means that the best that can be done without going over either +-12V or +-3A is a 12/3 = 4ohm speakers. a 2ohm speaker would draw +-6A from out +-12V source.
ok, now lets bridge the channels. the output (which is more like a series connection of amplifiers) allows for +-24V, +-3A. 24/3 = 8ohm. a 4ohm speaker would draw 6A, and a 2ohm would draw 12A.
notice that in order to keep within the design specs, the impedance of the speaker must be higher when used with a bridged amplifier.
ok, now lets bridge the channels. the output (which is more like a series connection of amplifiers) allows for +-24V, +-3A. 24/3 = 8ohm. a 4ohm speaker would draw 6A, and a 2ohm would draw 12A.
notice that in order to keep within the design specs, the impedance of the speaker must be higher when used with a bridged amplifier.
Immacomputer
10+ year member
Cloud disappear
Wiring in parallel is NOT the same thing as bridging. Wiring in series is NOT running unbridged.
You are confusing yourself with your terminology. Whether you wire your speakers in parallel or series makes no difference besides what load the amp sees. The amp is not creating the load, the speakers are.
Bridging basically takes two channels of an amp and makes them run on one channel. When this happens internally, each channel sees half of the load that you present to it. If the lowest load each channel is capable of when not bridged is 2 ohms, then when you bridge the channels, 4 ohms is the minimum value you can safely present to the amp.
4/2 = 2
4(load you're presenting)/2(number of channels) = 2(load each channel is really seeing)
Take a look at the pictures of this amp:
http://sonicelectronix.com/item_6517.html#
Notice how on the speaker terminals is says CH1, CH2, and Mono? The mono is for bridging. Does that make sense to you?
- Thread Starter
- #7
Imma, I think you are getting to the crux of my issue here. I have always just assumed "Bridging" meant to run speakers in parallel (ie the positive lead from the left speaker and the positive lead from the right speaker together with the negative lead from the left and the negative from the right on one channel). This would in turn present a resistance cut of 1/2 to the amp and thus draw more current to the speaker and produce louder sound. So this assumption is incorrect??
as per the PM i sent, yes. bridging is basically hooking amplifier outputs up in series -- eg, the voltages add. with 2 channels, thats 2x voltage. because the speaker is unchanged, that means there is 2x current. each amp supplies 1x voltage, but 2x current, thus it sees 1/2x the resistance of the actual load.
keep in mind that there is no reason more amplifiers cannot be "bridged" so long as some method is used to ensure a floating output -- eg, there is no connection between amp1+ and amp2+ or amp3+ or ect... this can be done using transformers, but to my knowledge no one does things this way.
this also explains why HU's are unbridgable -- the outputs of an HU are basically already bridged (eg, 8 channels down to 4)
keep in mind that there is no reason more amplifiers cannot be "bridged" so long as some method is used to ensure a floating output -- eg, there is no connection between amp1+ and amp2+ or amp3+ or ect... this can be done using transformers, but to my knowledge no one does things this way.
this also explains why HU's are unbridgable -- the outputs of an HU are basically already bridged (eg, 8 channels down to 4)
Immacomputer
10+ year member
Cloud disappear
I don't think you have a very good understanding of electronics.
If I have two 8 ohm subs, I can wire them in parallel to one channel and it would only put a 4 ohm load onto the amp. I could also wire two 2 ohm subs in series to one channel of an amp and present a 4 ohm load to the amp. Neither of these cases are bridging the amp. I'm still only using 1 channel of the amp. When I bridge the amp, I am using both channels. Both of the situations I mentioned could be for bridging the amp as well.
Wiring the subs in parallel or series does not matter at all; it's how you wire up the amp that matters. You are correct in assuming that the lower the load you present the amp with, the more power the sub will get. That has nothing to do with bridging an amp though.
- Thread Starter
- #10
Actually I think my grasp of electronics is quite good. My grasp of bridging is where we are having trouble. So if simply running speakers in parallel is not bridging, then how would one bridge an amp correctly? Is there something that has to be done on the amp side to do this?
Immacomputer
10+ year member
Cloud disappear
I apologize; you're correct in that your grasp on Ohm's law is much better than many peoples' here.
Yes, bridging an amp is something that is done on the amp side, not sub side. I thought I made that clear with the link.
Take a look at this picture:
You can see that bridging the amp (running it mono) means that you will only use CH1+ and CH2- to hook up to your speakers. You're basically running the channels in series with each other like others have said. Internally, both channels are seeing 2 ohms each. Have you noticed that bridged power is almost always twice as much as the rated power of each channel at 2 ohms?
- Thread Starter
- #12
I guess I'm really asking how exactly it would be wired up.....I know this is probably getting frustrating for you guys...but keep in mind I don't do this for a living like some of you. Nor have I ever installed anything on my own except maybe some speakers. So for some like me, it's not as obvious as it is to you. =)
Immacomputer
10+ year member
Cloud disappear
Well, what speakers are you trying to hook up to what amp?
All you need to do is have the speakers wired to a 4 ohm load and then run a single positive wire to the positive terminal of one channel and then run the negative wire from the speakers to the negative wire on the other channel. The amp will have the terminals that you will use to bridge the amp labeled
All you need to do is have the speakers wired to a 4 ohm load and then run a single positive wire to the positive terminal of one channel and then run the negative wire from the speakers to the negative wire on the other channel. The amp will have the terminals that you will use to bridge the amp labeled
- Thread Starter
- #14
Ahh, ok. Crystal clear now. In fact I feel silly now. That's exactly what thch was trying to tell me in his PM. That makes sense. And ya, I wasn't having any trouble understanding how the values were coming out. Thanks fopr the help. Sorry if I was frustrating you guys...=P
- Thread Starter
- #15
I posted that last q before I saw the picture. I'm good now.
Activity
No one is currently typing a reply...
About this thread
