Hi all!
Hope I'm posting this in the right category.
I'm planning on adding a sub to my car's audio system, and would like to use the amp I currently have. There's 4 spare channels on it, that I would like to leverage instead of getting a new amp. Couple of snags with my plan so far:
I've read into it a bit further, and ran into an article on Wikipedia about wiring amps in parallel & bridged mode. From what I understand, bridging an amp -theoretically- quadruples power handling, but also halves the impedence the amp 'sees'. Thus, briding two channels would give me the power I need to drive the sub, but would now make it impossible impedance-wise.
The wikipedia article then goes into the possibility of wiring 4 channels into a brdiged-parallel topology: "[...] when both configurations are combined on a set of four single-ended amplifiers, the power output is increased four-fold but the power dissipation of each constituent amplifier is not increased [...]"
Forgive my perhaps somewhat simplified imagery here, but what I understand from this, is that I can set the system up in the following manner to obtain ~320W @ 4Ohm, enough to drive the sub I have my eye on (see image). That being said, Wikipedia isn't all that great a source, and I can't seem to find anything/anyone else on the internet using this setup. This has me a bit worried, and I don't want to blow any equipment in attempting this.
So. Assuming the amp can actually be bridged, some questions pop to mind: Does this actually work? Would there be any drawbacks to wiring it this way?
Many thanks in advance!
Hope I'm posting this in the right category.
I'm planning on adding a sub to my car's audio system, and would like to use the amp I currently have. There's 4 spare channels on it, that I would like to leverage instead of getting a new amp. Couple of snags with my plan so far:
- I don't know exactly how much power it can handle per channel. It's an older car, and despite my best efforts to obtain somewhat of a manual or datasheet on the amp, I'm coming up empty. That being said: I'm using 80 Watt (RMS) speakers in the rear, which seems to work without problems, so it's safe to say it can at least handle that.
- The sub I'm planning to use is rated at 250 Watt (RMS), and 4 Ohms nominal. The impedence is fine, as my current rear speakers are also 4 Ohm, but the 250W seems far off from the 80 I'm sure it can handle.
I've read into it a bit further, and ran into an article on Wikipedia about wiring amps in parallel & bridged mode. From what I understand, bridging an amp -theoretically- quadruples power handling, but also halves the impedence the amp 'sees'. Thus, briding two channels would give me the power I need to drive the sub, but would now make it impossible impedance-wise.
The wikipedia article then goes into the possibility of wiring 4 channels into a brdiged-parallel topology: "[...] when both configurations are combined on a set of four single-ended amplifiers, the power output is increased four-fold but the power dissipation of each constituent amplifier is not increased [...]"
Forgive my perhaps somewhat simplified imagery here, but what I understand from this, is that I can set the system up in the following manner to obtain ~320W @ 4Ohm, enough to drive the sub I have my eye on (see image). That being said, Wikipedia isn't all that great a source, and I can't seem to find anything/anyone else on the internet using this setup. This has me a bit worried, and I don't want to blow any equipment in attempting this.
So. Assuming the amp can actually be bridged, some questions pop to mind: Does this actually work? Would there be any drawbacks to wiring it this way?
Many thanks in advance!
In general, you absolutely can not directly connect the output of two independent channels. There have been a few (very few) amplifiers that would allow you to configure two channels as one single output (not bridged, a single signal line from two channels) but that's far different than connecting independent channels.
There are a couple of class D amplifiers that allow something like this but the channels are isolated by inductors.
You can bridge two channels to one voice coil. If the speaker has dual voice coils, you can bridge two channels to each voice coil.
There are a couple of class D amplifiers that allow something like this but the channels are isolated by inductors.
You can bridge two channels to one voice coil. If the speaker has dual voice coils, you can bridge two channels to each voice coil.
Thank you for the quick reply Perry!
It seemed strange to me too, but it would've been a neat solution. Odd that Wikipedia suggests this as a possibility.
Anyhow, on your suggestion of using the four channels as a double bridged mode:
I've considered this, but for as far as I understand it, it's not an option. Please correct me if I'm wrong, but:
It seemed strange to me too, but it would've been a neat solution. Odd that Wikipedia suggests this as a possibility.
Anyhow, on your suggestion of using the four channels as a double bridged mode:
I've considered this, but for as far as I understand it, it's not an option. Please correct me if I'm wrong, but:
- The sub I wish to use is indeed also available as a dual voice coil type. I take it this means that instead of it being 1x250W/4Ohms, it is now 2x125W/4Ohms.
- Bridging the amp would give me the power needed. Let's assume each channel indeed handles 80W, quadrupling this gives me more than enough to work with, even if this turns out to be much lower that the theoretical quadrupling.
- However, the impedance presented to the amp is now halved, in this case to 2Ohm. I'm pretty sure my amp isn't built for that, so this makes it impossible, right?
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Post a working link to the owner's manual for the amp.
Saying that the 'amp sees' a load other than what's connected is what people do but should not. If you connect a 4 ohm load, that's what the amp 'sees'.
Channels don't 'handle' power.
It takes a very tightly controlled power supply to get near quadrupling power.
Saying that the 'amp sees' a load other than what's connected is what people do but should not. If you connect a 4 ohm load, that's what the amp 'sees'.
Channels don't 'handle' power.
It takes a very tightly controlled power supply to get near quadrupling power.
I don't understand the comment about the impedance. Everywhere I look it says bridging allows the amp to either provide(?) twice, or four times the power, but halves impedance. I guess this is why I'm asking here, since there seems to be no clear newbie-friendly explanation into how this works.
If you care to elaborate, I'd be very interested.
As for the manual: This is a problem unfortunately. The amp came with the car back in 2004, and there seems to be no documentation on it whatsoever.
If you care to elaborate, I'd be very interested.
As for the manual: This is a problem unfortunately. The amp came with the car back in 2004, and there seems to be no documentation on it whatsoever.
The impedance of the load doesn't change unless you use a speaker of different impedance.
When going from 4 ohms (for example) stereo, to 4 ohms mono, the amplifier delivers twice the current at any given output level which is the same as it would with a 2 ohm stereo load but if a 4 ohm load is what's connected, that's what the amp 'sees'.
Is this an OEM amplifier or is it aftermarket?
When going from 4 ohms (for example) stereo, to 4 ohms mono, the amplifier delivers twice the current at any given output level which is the same as it would with a 2 ohm stereo load but if a 4 ohm load is what's connected, that's what the amp 'sees'.
Is this an OEM amplifier or is it aftermarket?
are you referring to the old stetson 7kd that has current limit on the output ? if not, please state which amp(s) you know
The amp is OEM supplied, but was not manufactured by the carmaker itself. Car's a Peugeot (French brand), but the amp is from JBL. Only data I have on it is that it goes by Peugeot's OEM code: 6560J1. The amp has some serial numbers on it, but even for the same car, same year, there seem to be different serials out there.
Back on the topic of bridging the amp: I'm willing to believe what you say at face value, but still feel I don't understand how exactly this works. I don't wish to take up your time explaining this is great detail, so I'll rephrase my ideas on the matter:
Am I getting this right?
Back on the topic of bridging the amp: I'm willing to believe what you say at face value, but still feel I don't understand how exactly this works. I don't wish to take up your time explaining this is great detail, so I'll rephrase my ideas on the matter:
- Assuming that quadrupling power is unrealistic, I take it doubling power at least is. This would put 2 bridged channels at 2x80W=160W. Plenty to drive one of two voice coils on the dual type, which is 2x125W
- Thus, bridging 4 channels into 2, I should be able to drive both voice coils off the 4 spare channels on my amp.
- 'Halving' the impedance of the speaker from 4 to 2 Ohms is a non-issue. The amp is connected to a 4Ohm speaker and drives it as-is impedance-wise, but merely supplies current as if it were driving a 2Ohm speaker, hence the doubling of the power.
Am I getting this right?
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Sorry, but capable (mono) car amps are so cheap that any kind of device to bridge an amp not made for it is more expensive.
If this amp is part of a factory "sound system", just stop. In most cases these amps are bridged already, giving up to 18 Watt rms into a 4 Ohm load. Some are made to be able to drive even lower loads, like 2 Ohm, using specialized speaker. This is all done to cut cost by using incompatible components. A "don't ever change anything" system.
If this amp is part of a factory "sound system", just stop. In most cases these amps are bridged already, giving up to 18 Watt rms into a 4 Ohm load. Some are made to be able to drive even lower loads, like 2 Ohm, using specialized speaker. This is all done to cut cost by using incompatible components. A "don't ever change anything" system.
Thanks for the concern Turbowatch, but this is not what I'm asking. I'm not here to discuss whether or not my amp can handle this setup in the manner you describe. I'm trying to learn something about how bridging works exactly. Please don't derail my inquiry.
Back on topic, are the statements from my previous posts correct?
Back on topic, are the statements from my previous posts correct?
If you want to test your amp for possible bridgeing, measure the output wires of one channel: one of the two has to be connected to ground. If not, it is bridged already.
Next: If you bridge an amp made for 4 Ohm, you got to increase the load to 8 Ohm or it will fail because of too much current.
So in the end you get two times the 4 Ohm power, not 4 times.
Sorry, this is final, no room for any further speculation.
PS if you got two channels of a bridgable amp that can drive 2 Ohm loads, you can use it bridged into a 4 Ohm load and get 4 times the power of a single channel at 4 Ohm.
Next: If you bridge an amp made for 4 Ohm, you got to increase the load to 8 Ohm or it will fail because of too much current.
So in the end you get two times the 4 Ohm power, not 4 times.
Sorry, this is final, no room for any further speculation.
PS if you got two channels of a bridgable amp that can drive 2 Ohm loads, you can use it bridged into a 4 Ohm load and get 4 times the power of a single channel at 4 Ohm.
I'm not here to discuss whether the amp is bridgeable, please read the whole topic. I'm clearly making my statements and questions under the assumption that it is. Whether it is or not is of no concern, as this is all just purely theoretical and for learning purposes.
Again, please refrain from derailing my tread. I'm merely interested in whether bridging works in the manner I'm describing in post #8.
Again, please refrain from derailing my tread. I'm merely interested in whether bridging works in the manner I'm describing in post #8.
#7:
No. It was an older Zed amplifier, ESX amplifiers. The class D amplifier IC that can do this is the attached. Page 24. This is used in the Taramps TS 400x4.
#8:
How do you know that the amplifier can drive 4 ohms mono? Are you sure that it's bridgeable?
Example
Take a perfect amplifier that has no drop in rail voltage and no loss in the output stage.
Let's say that the rail voltage is ±20v and it can drive the full 20v to the speaker on each channel.
If we drive 20v into 4 ohms, we get:
P = E^2/R
20^2 / R
400/4 = 100w for a 2 channel amp, that would be 100w/ch
Then if we bridge 4 ohms across the two channels, the amp can drive 40v into 4 ohms
40^2 / 4 = 400w
For a stereo configuration driving 20v into 4 ohms:
20/4 = 5 amps The output transistors in each channel are passing 5 amps of current.
For the bridged configuration:
40v/4 = 10 amps The output transistors in each channel are passing 10 amps of current.
No. It was an older Zed amplifier, ESX amplifiers. The class D amplifier IC that can do this is the attached. Page 24. This is used in the Taramps TS 400x4.
#8:
How do you know that the amplifier can drive 4 ohms mono? Are you sure that it's bridgeable?
Example
Take a perfect amplifier that has no drop in rail voltage and no loss in the output stage.
Let's say that the rail voltage is ±20v and it can drive the full 20v to the speaker on each channel.
If we drive 20v into 4 ohms, we get:
P = E^2/R
20^2 / R
400/4 = 100w for a 2 channel amp, that would be 100w/ch
Then if we bridge 4 ohms across the two channels, the amp can drive 40v into 4 ohms
40^2 / 4 = 400w
For a stereo configuration driving 20v into 4 ohms:
20/4 = 5 amps The output transistors in each channel are passing 5 amps of current.
For the bridged configuration:
40v/4 = 10 amps The output transistors in each channel are passing 10 amps of current.
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"If you bridge an amp made for 4 Ohm, you got to increase the load to 8 Ohm or it will fail because of too much current.
So in the end you get two times the 4 Ohm power, not 4 times."
Does this mean I can connect the two voice coils in series, changing the 2x125W, 4Ohm into a 1x250W 8Ohm load, and then drive it through 2 bridged channels on the amp?
So in the end you get two times the 4 Ohm power, not 4 times."
Does this mean I can connect the two voice coils in series, changing the 2x125W, 4Ohm into a 1x250W 8Ohm load, and then drive it through 2 bridged channels on the amp?
Thanks you Perry, that clarifies things a lot more.
"How do you know that the amplifier can drive 4 ohms mono?"
How about Turbo's comment on the impedance though? I believe this is what I meant earlier by the speaker 'presenting' itself as a lower impedance load.
And if so, can I solve this problem by way of what I'm describing in post #14; wiring the dual voice coils in series to increase the impedance from 4 to 8?
"How do you know that the amplifier can drive 4 ohms mono?"
- If I'm not mistaken, I'm already doing this. Two of the channels are currently driving two woofers, each 80W, 4Ohm.
- Nope, but I thought that to be of later concern. I figured I'd want to know what I was planning was even feasible and learn something interesting in the process. One thing at a time. If it turns out it's not possible, I'll at least have an idea of what my options are / what to look out for in selecting a different amplifier.
How about Turbo's comment on the impedance though? I believe this is what I meant earlier by the speaker 'presenting' itself as a lower impedance load.
And if so, can I solve this problem by way of what I'm describing in post #14; wiring the dual voice coils in series to increase the impedance from 4 to 8?
If you increase the impedance by 2x, you reduce the power by 2x.
I'm concerned that you're going to brick this OEM amplifier. Why not buy a cheap class D and use that for bass? There are hundreds(?) of dyno runs on cheap class D amplifiers that will easily outperform what you have.
I'm concerned that you're going to brick this OEM amplifier. Why not buy a cheap class D and use that for bass? There are hundreds(?) of dyno runs on cheap class D amplifiers that will easily outperform what you have.
"If you increase the impedance by 2x, you reduce the power by 2x."
- But will I need to do this to guard against "too much current" as Turbo puts it, or can I just present the 4Ohm speaker as-is and not worry about it?
For the channels concerned, do you see signal on both the positive and negative speaker terminals?
On only the positive terminals?
On one positive and one negative speaker terminal?
I think he was talking about driving each channel into a 4 ohm load.
What were these channels being used for, originally?
On only the positive terminals?
On one positive and one negative speaker terminal?
I think he was talking about driving each channel into a 4 ohm load.
What were these channels being used for, originally?
I'm unsure about the output of the channels right now. It's dark and cold out right now where I live, so I'll check this out later, maybe tomorrow.
The original setup was for 8 speakers, but the sound quality was horrendous. I replaced 4 of them for better speakers, already increasing quality significantly. I removed the other 4, so now there's 4 channels left that I'm not using, which got me contemplating putting in a sub to help out with the low end.
"I think he was talking about driving each channel into a 4 ohm load. "
The original setup was for 8 speakers, but the sound quality was horrendous. I replaced 4 of them for better speakers, already increasing quality significantly. I removed the other 4, so now there's 4 channels left that I'm not using, which got me contemplating putting in a sub to help out with the low end.
"I think he was talking about driving each channel into a 4 ohm load. "
- I don't understand this comment. Again: Assuming all four channels are able to supply at least 80W @ 4Ohm, can I bridge them and connect the bridged output of channels 1 & 2 to voice coil 1 of the sub (125W, 4Ohm), and the bridged output of channels 3 & 4 to voice coil 2 of the sub (also 125W, 4Ohm)?
You need to get him to tell you what he meant.
You need to answer the questions I asked to help tell me what I need to know about bridging.
You need to answer the questions I asked to help tell me what I need to know about bridging.