Amp questions

[TLS Guy]

You are talking like you are the authority, know more/better than the manufacturers. What is nonsense, the theory? Come in, how much do you know about electrical theory? Now I am done...

The onus is on you to explain how the back EMF differs from one amp, or two driving a passive crossover. The filter sections in the standard parallel crossover net works, are just that in parallel. Series crossover networks are very rare, these days, and you could not passively biamp one anyway. So please explain how the back EMF is of any different magnitude or consequence whether the speaker is passively biamped or not.

 

[PENG]

The onus is on you to explain how the back EMF differs from one amp, or two driving a passive crossover. The filter sections in the standard parallel crossover net works, are just that in parallel. Series crossover networks are very rare, these days, and you could not passively biamp one anyway. So please explain how the back EMF is of any different magnitude or consequence whether the speaker is passively biamped or not.

I read my own post just now to see how it was not clear to you. I did find one typo in my 2nd sentence "...effects on the heavy current etc.............." It should have been effects “of”, not “on”. To me this does not explain why you responded the way you did.

Now, let me be clear, I did not believe in the benefit of passive biamp because I know any resulting difference won't be audible to me. In my post I simply reported (i.e. not quoted word for word) what some manufacturers are saying about the theoretical benefits. I did say I believe in the theory, by theory I meant the electrical/electromagnetic theory.

Having clarified what should have been apparent to you if you bothered to read it first before responding by saying it is "nonsense", do you still think I have the onus to explain? If so, explain what, explain why I believe in some theory, or call it claims if you prefer? I don’t know what in my post provoked you enough to turn a somewhat technical conversation into accusation. I used words like "please be reminded"; you use "This is nonsense". Your response to mtrycrafts puzzles me even more!

Regarding your question "how the back EMF differs from one amp, or two driving a passive crossover." This question need not be asked in the first place. I am not aware of anyone saying that there is a difference. What I referred to in my post was about the alleged benefits of separating out the heavy bass signal currents from the high frequency signal currents so that each will have its own path/cable. Back emf or not, the lows and highs flow in separate cables, that’s the physical difference. To save me from unintentionally misquoting anyone, you could if you wish, follow the following links to read the descriptive yourselves. You may also visit some British speaker sites e.g. B&W, KEF, among others.

http://www.vandersteen.com/pages/Answr7.htm
http://www.axiomaudio.com/tips_biwiring_and_biamping.html

Thanks!

 

[TLS Guy]

I read my own post just now to see how it was not clear to you. I did find one typo in my 2nd sentence "...effects on the heavy current etc.............." It should have been effects “of”, not “on”. To me this does not explain why you responded the way you did.

Now, let me be clear, I did not believe in the benefit of passive biamp because I know any resulting difference won't be audible to me. In my post I simply reported (i.e. not quoted word for word) what some manufacturers are saying about the theoretical benefits. I did say I believe in the theory, by theory I meant the electrical/electromagnetic theory.

Having clarified what should have been apparent to you if you bothered to read it first before responding by saying it is "nonsense", do you still think I have the onus to explain? If so, explain what, explain why I believe in some theory, or call it claims if you prefer? I don’t know what in my post provoked you enough to turn a somewhat technical conversation into accusation. I used words like "please be reminded"; you use "This is nonsense". Your response to mtrycrafts puzzles me even more!

Regarding your question "how the back EMF differs from one amp, or two driving a passive crossover." This question need not be asked in the first place. I am not aware of anyone saying that there is a difference. What I referred to in my post was about the alleged benefits of separating out the heavy bass signal currents from the high frequency signal currents so that each will have its own path/cable. Back emf or not, the lows and highs flow in separate cables, that’s the physical difference. To save me from unintentionally misquoting anyone, you could if you wish, follow the following links to read the descriptive yourselves. You may also visit some British speaker sites e.g. B&W, KEF, among others.

http://www.vandersteen.com/pages/Answr7.htm
http://www.axiomaudio.com/tips_biwiring_and_biamping.html

Thanks!

Thank you for those references. The Vandersteen posting flies in the face of Fournier analysis. There is only one signal at a given time, the waveform changes. The axiom statements are honest, and you can tell they really don't believe a word of it.

My reply to mtrycrafts, was to point out that looking at the impedance curve of a speaker in isolation is meaningless, except in so far as it rlates to the ease of the amp drive. There is a misconception about, including these forums that the impedance curve has some bearing on a loudspeakers frequency response. It does not.

The issue from my point of view, is to help steer new comers in the direction of sound science and not bogus science and superstition. It is a pity when scarce funds are wasted on spurious tweaks of highly questionable value. Passively biamping, with a large amp just driving a tweeter is one such. This was the whole point of this thread.

I think I pointed the original member in the right direction. The thread should have stopped there in my view. All this serves to confuse the original questioner, and not get him not a wit nearer to the "The closest Approach to the Original Sound." And I quote Peter Walker's slogan advisedly, as he was a dogged and persistent debunker of audio myth. I for one will carry that on in his memory.

 

[PENG]

Thank you for those references. The Vandersteen posting flies in the face of Fournier analysis. There is only one signal at a given time, the waveform changes. The axiom statements are honest, and you can tell they really don't believe a word of it.

I am familiar with Fourier analysis and have used Fourier transforms. I think you might have misunderstood Vandersteen’s article. To analysis the claimed effects, I believe it has more to do with the superposition theorem and a few electromagnetic theories. Fourier analysis allows us to determine the harmonic contents of the waveform at any instant (one per instant as you said, but time varying of course), other than that I do not see any correlation with what was said in Vandersteen’s article.

As for Axiom, I also felt that they really don't believe in the benefits of bi-amp or bi-wire, but I see no evidence of them not believing in the theory regarding the interference between the low and high frequency currents. Most other North American sites I visited typically just cite the theory behind, but warn that there may not be any audible difference. The British manufacturers, e.g. B&W, KEF seem to be the believers.

FYI, I have quit participating in any bi-wire/bi-amp topics long ago, but this time I thought I should let codexp3 know that believers bi-amp for reasons more than just giving more power to the speakers. I do agree with you however, that in doing so, I could have confused him since he clearly is only interested in making use of the power available to him from his two 2X250W amplifiers.

Regarding mtrycraft's post, I didn't see anything in it that has anything to do with what you said in your response. On the other hand, if you look at those impedance curves in his link, some of the speakers have lower impedance in frequencies way above the 400 Hz mark that you talked about. I thought may be that was the point he was trying to make but that's just my own interpretation.

 

[mtrycrafts]

Impedance curves having nothing to do with how a speaker sounds or as to whether it s any good or not. We seem to be heading down a route of massive ignorance, misunderstanding and pseudo science. I other words a huge BS factor.

You mean that if one speaker has high impedance between 500Hz and 1kHz and the next speaker is low, that band will sound the same on both, or could, with the same signal input?

But, my response to avrat was about this
I believe the S8 is designed to split the incoming power evenly between the two sections so it doesn't matter which way you use the amp.

 

[TLS Guy]

You mean that if one speaker has high impedance between 500Hz and 1kHz and the next speaker is low, that band will sound the same on both, or could, with the same signal input?

The speakers may well sound different, but it will have nothing to do with the impedance curve per se.

All moving coil drivers have voice coils which are inductors. Therefore the impedance must rise with frequency. So lets take a full range driver. The impedance curve will rise with frequency, but spl will be constant with frequency, assuming an input of constant voltage. This is assuming a well designed driver. However if we now make that driver a woofer, we usually have to correct the rising impedance with some type of network, like a zobel, or the choke/chokes in the crossover can not cut the driver off. As the impedance of the driver increases, the the impedance of the choke/chokes increase with frequency, and the driver does not cut off without some impedance correction. You never have to correct the impedance of a full ranger.

Now there will be impedance humps related to bass tuning. One bump for sealed, and two for reflex and TL loading. These humps are confirmation of correct tuning and do not need correction.

Frequency response aberrations are the result of nonlinear suspension, uncontrolled and unpredictable cone break up modes, cancellation and reinforcement of cone edge termination reflections. The crossovers play a big part. There are comb filtering interactions from driver overlap and misjudgement of the sum responses at crossover. There are also the problems of baffle reflections. These are the major factors that have to be considered in achieving flat response. The impedance curve reflects the sum total of the inductive, capacitative loads, total DC circuit resistance, and the effects of box tuning.

Basically when doing a design you try to achieve as flat a response as
possible, especially in the midband, while minimizing aberrations from phase and time delay. This also includes the off axis response. The art is the sum of compromise. Then you look at the impedance curve. You then see if it is feasible to improve it, to make the speaker an easier drive without upsetting the apple cart. But honestly correcting the impedance curve is low priority. The speaker designer lets the amp guy worry about that!

 

[TLS Guy]

I believe the S8 is designed to split the incoming power evenly between the two sections so it doesn't matter which way you use the amp.
[/QUOTE]

Look at page 9 of the user manual, speaker connections. It states clearly that one set of terminals supplies the mid/bass and the other the HF.

 

[mtrycrafts]

I believe the S8 is designed to split the incoming power evenly between the two sections so it doesn't matter which way you use the amp.

Look at page 9 of the user manual, speaker connections. It states clearly that one set of terminals supplies the mid/bass and the other the HF.[/QUOTE]

Since that speaker can be bi-amped, it has two sets of terminals. How does that split any incoming power evenly? Unless you mean the music content power below and above 500Hz are about even?

 

[TLS Guy]

Look at page 9 of the user manual, speaker connections. It states clearly that one set of terminals supplies the mid/bass and the other the HF.

Since that speaker can be bi-amped, it has two sets of terminals. How does that split any incoming power evenly? Unless you mean the music content power below and above 500Hz are about even?[/QUOTE]

That's the whole point, it doesn't split it evenly. The amp connected to the low pass/band pass filters will do all the work and the one connected to the high pass filter will deliver milli watts. A waste of time and money. As I stated previously for most program material the power divide is around 400 Hz.

 

[mtrycrafts]

Since that speaker can be bi-amped, it has two sets of terminals. How does that split any incoming power evenly? Unless you mean the music content power below and above 500Hz are about even?

That's the whole point, it doesn't split it evenly. The amp connected to the low pass/band pass filters will do all the work and the one connected to the high pass filter will deliver milli watts. A waste of time and money. As I stated previously for most program material the power divide is around 400 Hz.[/QUOTE]


And now we are back where we started :
I believe the S8 is designed to split the incoming power evenly between the two sections so it doesn't matter which way you use the amp.


the crossover only splits the point where the musical power is divided, not an amp's power. That is what is not clear what they mean, what they are dividing.

Why would the amp care what frequency it is supplying power to as long as the clipping point is not reached.

 

[TLS Guy]

That's the whole point, it doesn't split it evenly. The amp connected to the low pass/band pass filters will do all the work and the one connected to the high pass filter will deliver milli watts. A waste of time and money. As I stated previously for most program material the power divide is around 400 Hz.

And now we are back where we started :
I believe the S8 is designed to split the incoming power evenly between the two sections so it doesn't matter which way you use the amp.


the crossover only splits the point where the musical power is divided, not an amp's power. That is what is not clear what they mean, what they are dividing.

Why would the amp care what frequency it is supplying power to as long as the clipping point is not reached.[/QUOTE]

The amp won't care! It is just that the amps will be supplying power at the frequencies the filters they are connected to allow them to pass. In the case of the S8, one amp will pass only the power fed to the tweeter and that is minute compared to the other amp, and a wast of time. To share mower evenly you would have to be able to connect to a filters passing frequencies above and below 400 Hz, assuming equal sensitivity of the speakers above and below that divide, and that would not likely be the case either.

If the S8 connected one set of amps to the woofers, and the other to the Mid /HF there would be some merit, as then there would be power sharing. However on page 9 of the manual it clearly states that this is not the case.