Monster amps that are happy bridged to 4ohm?

[Jon_Logan]

No stool was ambushing you, no need to get defensive. I merely pointed out an incorrect statement, and tried to clarify. Note, what you said was not true, and it is still not true. Hence my piping up with the comment that the bridged amp does not see a speaker half the impedance of the non-bridged amp.



Thanks for correcting the link. The earlier link to graphic and parametric equalizers didn't make too much sense in this context. Now, if you had read the link you provided, you'd see something like this mentioned:



This supports exactly what I was trying to communicate to you earlier. When you put two amp channels in series (bridged), it is easy to see you get 2X the voltage. When 2X the voltage is applied to the same load, the result is 2X the current. Your claim that the amp would see half the load would result in 4X the current. But, this is not what happens. Please read that link. A bridged amp does not see half the impedance.

I do certainly agree (as noted in my previous post) that each half of the bridged amp must be stable into one half of the attached load. But, a half of a bridged amp does not make a bridged amp. From the point of view of the bridged amp, it sees the load for what it is.

I essence, I believe we are in agreement. It is just that you erroneously worded your position, twice. Oops, make that thrice.

Here's a little mental exercise for you: If a single-ended amp supplies 8V to an 8ohm load, it will produce 1A of output current. In your world, if a bridged amp supplies 8V to an 8ohm load, it will provide 2A of current. In the real world, the bridged amp suppling 8V to an 8ohm load will provide the same 1A that a single-ended amp will deliver. Wacky, huh? I understand you don't care, but perhaps some day, long into the future, you may think about this.

MarkW is right.


Single-ended vs. Bridged. A single-ended amplifier producing an 8V (rms) waveform into an 8 ohm load produces 1A of current.

A bridged version of the same amp now produces 16volts across the load. The waveforms are out of phase which produces a virtual ground, or null, in the center of the load. That would be 4 ohms. 8v across 4Ohms in a bridge.

 

[electroking]

A bridged amp does not see half the speaker impedance, if you consider the
amplifier as a whole. But of course the virtual ground does exist and each
individual amplifier does see half the impedance. Someone should write a small
essay about all this, complete with figures and calculations, as well as real world
examples.

 

[kevzep]

House de Kris is actually completely correct, I dont know why people take such offense when someone tries to post the correct information....

No the Crowns are not that expensive, I picked up two recently for $1500US each....
But they are very complicated amplifiers, and unless you are a serious tech I wouldn't buy one.
They have their little quirks, essentially they are one of the most reliable amplifiers I have ever known, but they do have certain things which can go wrong that require an in depth knowledge of electronics....
I have service notes which I have complied for everything that goes wrong with them.....

If you have difficult speakers, the Crown will deal with them without breaking a sweat....:thmbsp:

Moderator.........are you allowed to say 'stool sample' in an amp discussion??? Yikes....this has turned serious.......

Consider BRYSTON amps too.

Kevin....those Macrotechs are cool...........................costly?

 

[Jon_Logan]

House de Kris is actually completely correct, I dont know why people take such offense when someone tries to post the correct information....

I think that we're talking about the viability of a bridged amp connected to a 4 ohm load. In that case, I think it's perfectly reasonable, even necessary, that we talk about what impedance the amp "see's". I don't mean the amp as a box. I mean the amp as an amp channel.

If the desire is to bridge an amp, it stands to reason that more output is wanted. If more output is wanted and the speaker is 4 Ohms, then I think it's right to explain that each amp channel "see's" 4 (Ohms)/2 or 2 Ohm's that each amp channel "see's". You couple that with large voltage swings and you start to leave a Safe Area and operation gets riskier and riskier.

If that's the reality of the intended setup, then an amp with special circuits and thermal management to deal with the extra heating and current is in order.

 

[laatsch55]

THAT is the ugly truth. It makes the fascination for more power seem silly.

It's all about the SOA, is it not Jon??

 

[Jon_Logan]

It's all about the SOA, is it not Jon??

Yeah, I hear ya.

But, regarding SOA, an amp with more output capability (higher rails and the dissipation that goes with it) is riskier to operate and is more likely to blow up, all things being equal. In other words, two identical amps, just that one has half the power supply voltage, the one with the higher supply voltage is more likely to blow up.

If you mean SOA with regards to a tweeter more likely to be damaged by a clipping amp when compared to a "clean power" amp, I think there's been some new study into whether that really is the case, or not. I used to believe that there was an extra layer of safety by using more power, but I'm not so solid on that right now.

I really wish that speakers did more with the electrical input that they're given. When you see that there's a need for 2000 watt speakers, that's kind of a strong indicator the technology is getting to it's limits. 2000Watts..... ......that's more than a space heater. Liquid cooling will soon be required.

If your speaker can take (comfortably) what a bridged amp can throw at it, what does that get you? It will only be a little louder than 10 Watts, but to get that "a little louder" takes immense increases in power. ... let alone cooling. That is only if your system is very linear. The B&W 801 (series 3, I think?) cannot get loud. We were powering it with a Kyocera B-910. It had about 250 Watts per channel, so we started to crank it........It got louder than we normally played them at, but we could talk over it. We kept trying to crank it up, but after some point it actually got quieter, the more we turned it up. That was definitely thermal compression in action. The point is, if you want output, it's best to start with a relatively sensitive (efficient) loudspeaker.

 

[laatsch55]

Jon I have some severely modded Kornerhorns. Crites 1526S woof, B & C DCM -50 2" throat driver with the wood Martelli tractix horn and Crites CT 125 tweets,. Al K's universal crossover.
I drive them with a White Oak converted Phase Linear 700. We call em WOPL 1000's cause they will 500+ before clipping. I have run my horns routinely in the 250-400 watt range with excellent results. Of course when playing on the edge after every song I let the voice coils cool for awhile. Thermal compression is real. So is the meltdown right afterwards if you don't heed that warning. I still am enthralled with tons of clean power as that setup will take a BIG transient and keep going. I have actually sat in the sweetspot and had my eyeballs vibrate---WHY? ---you ask, for the live concert experience. Not everyday, but often enough The WOPL's in the main rack.
I have not blown anything but the swamping resistor and cap for the tweets. I'm still amazed that ,that efficient a speaker will take it.



PS---There is no hope in hell of talking over my setup when it's cranked...

 

[Jon_Logan]

Hey Laatsch55, the K-horns are some of the most efficient speakers out there.

When you say you run them at 250 watts or so, are you determining that with an O'scope? If not, try it and put tick marks on the scope's display showing 1W, 10W and 1000W and see the change in volume amongst these levels. 10W ain't that different sounding than 1000W. ...and 10W on a K-horn is pretty damned loud.

 

[House de Kris]

MarkW is right.


Single-ended vs. Bridged. A single-ended amplifier producing an 8V (rms) waveform into an 8 ohm load produces 1A of current.

A bridged version of the same amp now produces 16volts across the load. The waveforms are out of phase which produces a virtual ground, or null, in the center of the load. That would be 4 ohms. 8v across 4Ohms in a bridge.

OK, if you want to make an example using 16V instead of 8V, that is fine. But, you didn't finish the analysis. What current are you suggesting this 16V source will develop in the 8ohm load? If you answer 2A, then you are agreeing with me. If you say 4A, then you are agreeing with MarkW. But, if you say 4A, then you are violating Ohm's Law, and as far as I know, breaking Ohm's law will make the universe, as we know it, implode.

I think that we're talking about the viability of a bridged amp connected to a 4 ohm load. In that case, I think it's perfectly reasonable, even necessary, that we talk about what impedance the amp "see's". I don't mean the amp as a box. I mean the amp as an amp channel.

If the desire is to bridge an amp, it stands to reason that more output is wanted. If more output is wanted and the speaker is 4 Ohms, then I think it's right to explain that each amp channel "see's" 4 (Ohms)/2 or 2 Ohm's that each amp channel "see's".

Which brings us back to my original post that MarkW viewed as an ambush and felt name calling was an appropriate answer. Where he said a bridged amp sees a four ohms speaker as a two ohm speaker. A two ohm speaker implies a single two ohm speaker. I merely stated a bridged amp would see a four ohm speaker as two two ohm speakers. Since you say, "each amp channel "see's" 4 (Ohms)/2 or 2 Ohm's that each amp channel "see's"," and we're discussing two channel amps being bridged to one, then it would seem that you too are saying the bridged amps hooked to a four ohm speaker sees two two ohm speakers. Everything you've written seems to agree with what I was saying. And, I agree with you. And yet, you say that MarkW is right.

 

[Jon_Logan]

OK, if you want to make an example using 16V instead of 8V, that is fine. But, you didn't finish the analysis. What current are you suggesting this 16V source will develop in the 8ohm load? If you answer 2A, then you are agreeing with me. If you say 4A, then you are agreeing with MarkW. But, if you say 4A, then you are violating Ohm's Law, and as far as I know, breaking Ohm's law will make the universe, as we know it, implode.

(Now) I am saying 16(V)/4(Ohms)= 2A. I never insinuated anything different. I think the issue is you are using semantics to change the nature of the discussion.

Aren't we talking about the safety, usage, and viability of using a bridged amp on a 4 Ohm load?
If so, then we should (I think) talk about the risks of doing that. One of the risks, that MarkW correctly pointed out, was that the "amplifier" see's half the impedance. You know what he meant and I know what he meant. You decided that he was wrong because he used the word "amplifier", and to you that meant a stereo amplifier. "Amplifier" to me, means a circuit that amplifies current, or voltage. It doesn't mean stereo amplifier, or mono amplifier, or 7 channel amplifier.

Do you really want to cloud the point of operational safety and margin with arguments buried in semantics?

Here's a question for you.

Is it safer to run a 4 Ohm speaker single-endedwith 28.2 volts or a bridged amp with 4 Ohms hanging between them with the same input signal??

Which brings us back to my original post that MarkW viewed as an ambush and felt name calling was an appropriate answer. Where he said a bridged amp sees a four ohms speaker as a two ohm speaker.

Again, I think we both know what he was saying. Are you arguing the gist of what he's saying to be the semantic police?

A two ohm speaker implies a single two ohm speaker. I merely stated a bridged amp would see a four ohm speaker as two two ohm speakers.

Where did you say that? I must have missed that.

 

[House de Kris]

(Now) I am saying 16(V)/4(Ohms)= 2A. I never insinuated anything different. I think the issue is you are using semantics to change the nature of the discussion.

Aren't we talking about the safety, usage, and viability of using a bridged amp on a 4 Ohm load?
If so, then we should (I think) talk about the risks of doing that. One of the risks, that MarkW correctly pointed out, was that the "amplifier" see's half the impedance. You know what he meant and I know what he meant. You decided that he was wrong because he used the word "amplifier", and to you that meant a stereo amplifier. "Amplifier" to me, means a circuit that amplifies current, or voltage. It doesn't mean stereo amplifier, or mono amplifier, or 7 channel amplifier.

Do you really want to cloud the point of operational safety and margin with arguments buried in semantics?

Here's a question for you.

Is it safer to run a 4 Ohm speaker single-endedwith 28.2 volts or a bridged amp with 4 Ohms hanging between them with the same input signal??



Again, I think we both know what he was saying. Are you arguing the gist of what he's saying to be the semantic police?




Where did you say that? I must have missed that.

Semantics are an important part of language and communication. You could claim I'm doing a semantics police thing, I may think I'm doing a bizzar-o statement police thing. Either way, I'm stiving for clarity here. I was just trying to clarify a statement that, on the surface, makes an outlandish claim. That a bridged amp sees a four ohm speaker as a two ohm speaker. You yourself brought up the concept of virtual ground in the middle of the speaker. Yes indeed, this makes the bridged amp see the four ohm speaker as two two ohm speakers. This clarification of a minor point (which I did say it was minor at the get-go) makes the confusing statement clearer. Yes, I did know what he meant, and I wanted this point to be clear to others who may not be able to read through the murky water MarkW was posting.

To say I decided he was wrong based on my belief of what wrong word he used is trying to read my mind. As is typical with mind readers, it isn't right. I think you and I have the same understanding of amplifier, and I wasn't making any assumptions about it being stereo or not. That is why in my subsequent examples I always was trying to be clear with my wording of just talking about a bridged amp. For example, I was asking about the current from a single-ended amp delivering 8V to an 8ohm load and a bridged amp delivering 8V to an 8ohm load. You, then, assumed it was a stereo amp and that it therefore MUST be making 16V instead when bridged. That wasn't the case at all. I was trying to illustrate that a bridged amp sees a load for what it is, not half of what it is.

In your question to me, "Is it safer to run a 4 Ohm speaker single-endedwith 28.2 volts or a bridged amp with 4 Ohms hanging between them with the same input signal??" What is the 'them' to which you refer? I could make assumptions about what you are meaning, but better clarity in writing would be of greater value. I could also assume that the 28.2 volts is an output voltage, or it could be a rail voltage. But, what does that have to do with anything? On the one hand, I've got a mono-block single-ended amp from one manufacturer, and the other I've got a mono-block bridged amp from another manufacturer. The single-ended amp has a gain of 24dB, and the bridged amp has a gain of 17dB. The single-ended amp has eight total output devices and the bridged amp has 24 output devices. Both have the same input signal. Which is safer? Based on only the data I provided in filling in the blanks in your question, I'd say the bridged would be safer. Clarity is important, is it not?

All I was doing was pointing out a clarification to a confusing statement.

Go back and check post #23, right before your post #24. That was my ambush.

 

[Markw]

My statements were quite clear and accurate. It's you who were incapable of comprehending them and chose to make this a confusing issue to publicly stroke your "ego".

And yes, I am very anti-semantic.

 

[laatsch55]

Hey Laatsch55, the K-horns are some of the most efficient speakers out there.

When you say you run them at 250 watts or so, are you determining that with an O'scope? If not, try it and put tick marks on the scope's display showing 1W, 10W and 1000W and see the change in volume amongst these levels. 10W ain't that different sounding than 1000W. ...and 10W on a K-horn is pretty damned loud.

No Jon, output meter levels and a Fluke 179 measuring output AC.

 

[Jon_Logan]

No Jon, output meter levels and a Fluke 179 measuring output AC.

Meters are going to be good for steady state signals, but for music, they are a bit too slow. Peak LED's or some super fancy meters like the one's found on a Yamaha P-2200 can work, but a scope is the ideal tool for observing peaks. You could calibrate your system (with say a 400Hz tone) and use some selectable input pads to hear the level differences between 1, 10, and 100 watts. All I can say is, "the first time you hear it, it's surprising".

Music has variable peak to average ratios, where most of the time you're listening to the average sound level, but the peaks can be 20dB (electrical) higher.

It takes a doubling of the voltage to get +3dB more power, so you can see it's a slog after about 10 watts to make major increases in acoustic output.

The K-horns are a good speaker to get a lot of output without racks of power. In doing so, they really can play loud for a long time and have a lot of margin from thermal compression.

 

[House de Kris]

It takes a doubling of the voltage to get +3dB more power, so you can see it's a slog after about 10 watts to make major increases in acoustic output.

A doubling of the voltage is a 6dB increase. But you'll probably just claim I'm the semantic police again, and that you are actually correct. Go for it!

 

[Jon_Logan]

A doubling of the voltage is a 6dB increase. But you'll probably just claim I'm the semantic police again, and that you are actually correct. Go for it!

You mad bro?

 

[House de Kris]

You mad bro?

Not at all. Does this disappoint you? BTW, I don't think we're related.

 

[ron-c]

Back to the original post. Most amps that are bridgeable will caution against using speakers below 8 ohms when the amp is bridged. Since the amp will see a 4 ohm speaker as 2 ohms when bridged this will trigger the amp's protection circuit or worse.
If you had a McIntosh with output autoformers you could run it bridged into 4 ohms but most direct coupled amps will limit you to 8.
Just use a big stereo amp that is rated into 4 ohms and your speakers will be happy.

Thanks,
Ron-C

 

[89grand]

A doubling of the voltage is a 6dB increase. But you'll probably just claim I'm the semantic police again, and that you are actually correct. Go for it!

True, a doubling of voltage at the same impedance is also twice the current, and that does equal 6db, or 4 times the wattage.

 

[KentTeffeteller]

ron-c's advice is recommended and practical.