The object here is to figure out what amps work with these speakers.
Knowing why would be beneficial too.
The amps that B&W actually uses to test their speakers are
- Rotel
- Classe
- Levinson
- Krell
There may be others - but Rotel and Classe are part of the B&W group.
However, people who actually own B&W Nautilus, Signature or Diamond speakers often use
- Pass Labs X250.5, X350.5 and class A mono blocks
- Conrad Johnson tube pre ===> MF2500A power
- McIntosh 6900 integrated
I strongly suspect a
a BAT tube pre ==> BAT ss power amp will be a match too.
Another clue is here - In the liner notes of
Haydn Violin Concerti No. 1 & 4
Rachel Podger
Channel Classics CCS SA 29309
it says - Mastering room
Classe 5200 Amp ==> B&W 803d - all cables are Van den Hul
What is it about these amps that make them capable of driving these speakers ?
- they have huge passive power supplies (Except Levinson)
- they have many paralleled output transistors (the MA6900 has autotransformers)
- From this list, the preferred amps have MOSFET's in the output stage.
Looking at the Pass Labs X350.5 the DF = is only 150
However - Iout(max) = 28 Amps per channel
BTW: here is an impedance curve for a N801.
Knowing why would be beneficial too.
The amps that B&W actually uses to test their speakers are
- Rotel
- Classe
- Levinson
- Krell
There may be others - but Rotel and Classe are part of the B&W group.
However, people who actually own B&W Nautilus, Signature or Diamond speakers often use
- Pass Labs X250.5, X350.5 and class A mono blocks
- Conrad Johnson tube pre ===> MF2500A power
- McIntosh 6900 integrated
I strongly suspect a
a BAT tube pre ==> BAT ss power amp will be a match too.
Another clue is here - In the liner notes of
Haydn Violin Concerti No. 1 & 4
Rachel Podger
Channel Classics CCS SA 29309
it says - Mastering room
Classe 5200 Amp ==> B&W 803d - all cables are Van den Hul
What is it about these amps that make them capable of driving these speakers ?
- they have huge passive power supplies (Except Levinson)
- they have many paralleled output transistors (the MA6900 has autotransformers)
- From this list, the preferred amps have MOSFET's in the output stage.
Looking at the Pass Labs X350.5 the DF = is only 150
However - Iout(max) = 28 Amps per channel
BTW: here is an impedance curve for a N801.
Attachments
Last edited:
AndrewT said:
Okay fine, so the amplifier has a very small role in the "control" of the cone. Case closed then. The speakers own damping, VC inductance and the rooms damping provides the control, almost regardless of what amp it is hooked up with, assuming I'm right. I did not receive an answer to that, so what am I to think? I could ask the question again and instead of getting an answer I'll just have more jargon thrown my way.
It's not about reading comprehension. It's just confusing period. If someone had told me, "you're right, the woofer control is related to enclosure damping, VC inductance etc) then I would have an idea of which direction I'm in. If I'm not right, then please educate me, but do so intuitively. If it's not difficult to understand then one should be able to explain it rather simply ...
Last edited:
DF of 30 is good enough, so no need to go higher. However:Vaughan said:
- some speakers may be designed for a lower damping factor
- SS amps tend to have a very high DF for other reasons
- the cable and any crossover network will reduce the effective DF
Wattage is completely irrelevant in this context.
To understand all this you need to learn about electronics and damped resonance (both mechanical and electrical). Don't complain that we are not explaining it in terms you can understand; it is up to you to gain understanding of what are actually quite elementary concepts.
DF96 said:
I refuse to believe that it's somehow not possible to explain technical topics intuitively. Either it's simple to understand or it's not simple. I understand impedance more or less, without understanding the math, the equations etc. I understand other technical topics without requiring in-depth knowledge of the math.
Some of these concepts you assume I know, like "Rs". It was just introduced mid-way through the thread, it was not explained what Rs is. How am I supposed to understand that? It wasn't explained or defined! It's just assumed that I know what it is. So I ask more questions, then a member gets frustrated that I'm not reading properly?!?
I clearly don't have a background in electronics, but if I have to wade through text books to have a question answered (one which I find interesting nonetheless) then I'm probably better off just googling an answer. Instead, I came here to ask the question because I'm sure there are EE's posting here, or at least those far more knowledgeable than me who can explain these elementary concepts in an easily understood way.
I mean, if it is up to me as you said, then why bother posting at all? I should have just bypassed this forum altogether, dug up a textbook and crossed my fingers hoping I could make sense of the literature.
If the type of reply I'm going to get is basically, in a nutshell, "go and do your research, study the electronics, the math, etc, before posting", then perhaps this thread should be closed.
Last edited:
If you don't know the maths, you don't know the concept. Do you have any background in science or engineering? Do you always expect to 'understand' things without understanding them?Vaughan said:
What do you know about resonance? e.g. car suspensions, arm-cartridge resonance, tuning forks, tuning a radio (I am trying to think of everyday examples of resonant systems). Do you understand the concept of damping a resonance?
DF96 said:
No, I don't have a background in science or engineering. No surprise there. I do understand the basic concept of damping a resonance. I understand how sound propagates, I've read the Master Handbook of Acoustics, I've read a number of books that explain things intuitively without bombarding you with mathematical equations.
It is possible to understand the basics of *something*, without knowing everything there is to know. I have acoustic treatment in my room, I understand how it absorbs the sound and I can measure the room to see the results. I don't know everything there is to know about it, but that is kind of irrelevant.
I know, more or less, how a speaker operates, ported, sealed operation, the whole "mass on a spring" concept, etc. But among all this stuff there is a lot of misinformation, a lot of added confusion that does not help matters. Chalk it up to advertising fluff or whatever. But there is a lot of confusion out there. Certain things about speaker design I have no idea about, but I've never had to learn about it. I ask for advise not just to learn, but also for reassurance that what *I* know is actually correct.
OK. You probably know that the mechanical bass resonance of the speaker cone is damped by some combination of the suspension, the packing in the speaker box etc. In most cases this is (deliberately) inadequate to provide sufficient damping, so the speaker would 'ring' at its bass resonance frequency for a short while after any bass note was played through it.
We can add electrical damping too. Damping is basically taking energy away from whatever is oscillating, and (usually) turning it into heat. The speaker voice coil is sitting in a powerful magnetic field so as it moves it generates a voltage. This voltage sets up a current through the speaker, cables and amplifier output circuit. The size of the current depends on the total resistance in that circuit. The current through the coil causes an opposing force which tries to stop the speaker from 'ringing'. The mechanical energy of the speaker is turned into electrical energy then heat energy (mainly in the voice coil).
The most damping occurs with zero external resistance, so the voice coil resistance is the only resistance in the circuit. For an 8ohm speaker this could be 4-6 ohms, say 5 ohms. So you can't have more damping than 5 ohms worth. If the rest of the circuit is also 5 ohms then you only get half as much damping. As it is the total resistance that matters, there won't be much difference between 5.08 ohms and 5.8 ohms, yet this is a DF of 100 and 10 respectively.
(Sorry, I need to go and do something else now.)
We can add electrical damping too. Damping is basically taking energy away from whatever is oscillating, and (usually) turning it into heat. The speaker voice coil is sitting in a powerful magnetic field so as it moves it generates a voltage. This voltage sets up a current through the speaker, cables and amplifier output circuit. The size of the current depends on the total resistance in that circuit. The current through the coil causes an opposing force which tries to stop the speaker from 'ringing'. The mechanical energy of the speaker is turned into electrical energy then heat energy (mainly in the voice coil).
The most damping occurs with zero external resistance, so the voice coil resistance is the only resistance in the circuit. For an 8ohm speaker this could be 4-6 ohms, say 5 ohms. So you can't have more damping than 5 ohms worth. If the rest of the circuit is also 5 ohms then you only get half as much damping. As it is the total resistance that matters, there won't be much difference between 5.08 ohms and 5.8 ohms, yet this is a DF of 100 and 10 respectively.
(Sorry, I need to go and do something else now.)
One of the main reasons I use more power than is needed to sound loud enough is the fact that a lot of music has a high ratio of peak to average level - or high dynamic range. What you dont want to do is clip the amp on peaks. So, to avoid that possibility, you need headroom.
Most lower power amps and especially lower sensitivity speakers and larger rooms clip fairly regulary. That is the reason powerful amps sound so clean and effortless... they are not clipping periodically and throwing out distortion harmonics when they do clip.
-RNM
Vaughan,
I suggest you read my last post about amps that are known to work with Nautilus speakers.
The list of amps comes from people who have tried lots of amps with these speakers.
Here is a great article on speaker impedance.
http://komkris2000.webs.com/The story of Tube Friendly Speakers.pdf
Look carefully at the impedance curve in the middle of page 3.
He says "Nows lets look at some un-tube-friendly impedance graphs.
That is the impedance curve of the B&W N801 - as I've show above.
He says "there is a steep capacitive phase angle that intersects with a low [magnitude of] impedance. "
So |Z| = 3.0 ohms, during a wild swing in phase angle
How a speaker has a capacitive phase angle - I'm not sure.
But will leave that for a discussion on another day.
The article continues and discusses how some amps use current limiting.
Current limiting is a protection technique used in some amps.
The last thing needed with your N803's is an amp trying to limit current,
when |Z| goes down to 3.0 ohms.
Basically, an amp is needed that will double down to 2 ohms.
Another approach to these speakers, may be to bi amp them.
Use a small Class A MOSFET amp for the mid/tweeter.
and Bryston brute bi polar push pull amp for the bass.
But I'm not sure if the phasing would get messed up.
.
I suggest you read my last post about amps that are known to work with Nautilus speakers.
The list of amps comes from people who have tried lots of amps with these speakers.
Here is a great article on speaker impedance.
http://komkris2000.webs.com/The story of Tube Friendly Speakers.pdf
Look carefully at the impedance curve in the middle of page 3.
He says "Nows lets look at some un-tube-friendly impedance graphs.
That is the impedance curve of the B&W N801 - as I've show above.
He says "there is a steep capacitive phase angle that intersects with a low [magnitude of] impedance. "
So |Z| = 3.0 ohms, during a wild swing in phase angle
How a speaker has a capacitive phase angle - I'm not sure.
But will leave that for a discussion on another day.
The article continues and discusses how some amps use current limiting.
Current limiting is a protection technique used in some amps.
The last thing needed with your N803's is an amp trying to limit current,
when |Z| goes down to 3.0 ohms.
Basically, an amp is needed that will double down to 2 ohms.
Another approach to these speakers, may be to bi amp them.
Use a small Class A MOSFET amp for the mid/tweeter.
and Bryston brute bi polar push pull amp for the bass.
But I'm not sure if the phasing would get messed up.
.
If you have an electrical resonance, or good electromagnetic coupling to a mechanical resonance (as in a speaker), you will generally find that the impedance is inductive on one side of the resonance and capacitive on the other. It becomes purely resistive somewhere near the peak of the resonance. The details vary, but that is the general pattern.Uunderhill said:
I think I understand.
In the LCR section of an oscillator or band pass filter, the British used to use the word tank.*
On one side of resonance of the LCR, current laggs - and on the other side, current leads.
BTW: I should ask, are you a retired British or European analog designer ?
* Not as in a Military Tank - but as in a Tank of Water.
At resonance, the water swishes back and forwards between kinetic and potential energy.
.
What older British analog designers know about analog and RF design is very humbling.
When I think of damping factor - it goes back - way back - to Laplasse Transforms, Zeta = 0.707, step functions, settling time and all that stuff.
Certainly, in terms of damping, there is some sort of magic between a push-pull EL34 amp and Tannoys.
A lot of guys rebuild Eico amps with EL84's to match with Tannoys - but I think EL34's are better.
What I don't understand about the "Audio" amplifier term "Dampening" is that it is specified into a real impedance of 8 ohms.
Name me a speaker that has a real impedance of 8 ohms ?
This is fantasy Island.
What happens to the amp when the speaker has a complex impedance that goes down to 2.9 ohms ?
600 series B&W's, used to have impedances |Z| >= 3.9 to 4.3 ohms.
These speakers sounded great with British integrated amps.
Like a Roksan Caspian (MOSFET's).
Again more magic.
But there is not a chance in hell a Roksan Caspian Integrated can drive a B&W Nautilus, Signature or Diamond series speaker.
Nautilus speakers need an amp that can deliver tons of current into a difficult Z.
.
Damping Factor is simply a measure of amp output impedance. Instead of being specified in absolute terms (e.g. 0.16ohms) it is given in relative terms (e.g. 50 for a nominal 8 ohms). There is not a straightforward relationship between DF and electrical Q. DF should be regarded as a rough guide to LF speaker damping, and no more. Fantasies only arise if people attach too much meaning to it.Uunderhill said:
I really don't know.
To me, damping factor means putting in a step function and there will be a settling time.
Think a grain of salt is required with the audio version of "Damping Factor."
Certainly, with a load like 803 signatures - the supply rails on most amplifiers will sag pretty badly.
Plus for an amp to have a Zout and to be able to handle the current - amp designers usually parallel many output devices.
.
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.