No. They see the same voltage. Individual current to each woofer is undefined! The TOTAL current is, of course constant. Do you get it?
If two identical drivers are connected in parallel to the same voltage source, then they will each have the same current flowing through them.
The currents can even be measured within the usual limitations (Heisenberg, etc) to be identical.
Chris
OK, I'm being attacked from all sides here. And you guys are plain wrong. So I'll stick to my guns.
First, let's deal with "lobing" from "diyaudio-confused" speaker dave. A guy I respect a lot, a guy who worked at KEF a lot and designed some great speakers. This has NOTHING to do with particular filter functions, more that an MT has a certain below and above axis lobing. If you talked about "combing" with twin drive units, I would have more confidence in you.
Now, Chris, you really shouldn't quote "Heisenberg" at a guy with a knowledge of high-energy physics. I am likely to rip your head off. You completely neglect the way two bass drivers can interact to resonate. And if they can, they will.
Frankly, you're hopeless.
First, let's deal with "lobing" from "diyaudio-confused" speaker dave. A guy I respect a lot, a guy who worked at KEF a lot and designed some great speakers. This has NOTHING to do with particular filter functions, more that an MT has a certain below and above axis lobing. If you talked about "combing" with twin drive units, I would have more confidence in you.
Now, Chris, you really shouldn't quote "Heisenberg" at a guy with a knowledge of high-energy physics. I am likely to rip your head off. You completely neglect the way two bass drivers can interact to resonate. And if they can, they will.
Frankly, you're hopeless.
No. They see the same voltage. Individual current to each woofer is undefined! The TOTAL current is, of course constant. Do you get it?
Slightly separately, how BW3 works really, is it gives far more overlap between the drivers. Which means output falls off far less in all directions at crossover, including sideways. BW3 sounds much better than LR4 off-axis.
I am wondering about the relative merits of using the 3rd order Bessel topology vs the Butterworth topology for an MTM. I have not heard of anyone using a Bessel with an MTM design, but it seems like it should work well based on your explanation above. The Bessel topology has even more overlap than the Butterworth through the X/O region, and theoretically has more linear phase and group delay variation. As I understand it at least.
The two identical drivers are connected to the same low-impedance driving source. How can they have anything but the same current flow?
Even if the drivers do interact, they'll do the same thing to each other, so the same current will flow through each no matter what.
You're also making assumptions of my own knowledge. I too have an in-depth knowledge of physics, as do many of the members here. Perhaps, instead of quoting the same thing over and over again, you might explain yourself a little, and enlighten this little community?
Chris
OK, I'm being attacked from all sides here. And you guys are plain wrong. So I'll stick to my guns.
First, let's deal with "lobing" from "diyaudio-confused" speaker dave. A guy I respect a lot, a guy who worked at KEF a lot and designed some great speakers. This has NOTHING to do with particular filter functions, more that an MT has a certain below and above axis lobing. If you talked about "combing" with twin drive units, I would have more confidence in you.
Oh, I see. You are trying to make semantic distinction between combing and lobing. (A distinction without a difference, my old boss would say.) In either case we are talking about interference patterns, due to multiple elements, giving rise to polar peaks and dips.
Don't make me come over there and try and teach you your own language!!
Merry Christmas,
David
Hi, Speaker Dave.
Don't let us consider combing and lobing to be the same thing. I happen to think that any good MT design can be improved as an MTTM design.
That's all.
As for the physicists amongst us, I encourage you to join the semi-accurate thread: First Signs of Dark Matter, maybe Sterile Neutrinos. - SemiAccurate Forums
Perhaps we should design speakers that include "Dark Matter".
Don't let us consider combing and lobing to be the same thing. I happen to think that any good MT design can be improved as an MTTM design.
That's all.
As for the physicists amongst us, I encourage you to join the semi-accurate thread: First Signs of Dark Matter, maybe Sterile Neutrinos. - SemiAccurate Forums
Perhaps we should design speakers that include "Dark Matter".
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Hi,
Frankly your hopelessly opinionated rather than being right.
Your shooting in the dark as much as anyone else is, and
worse insisting your absolutely right, when your simply not.
Parallel drivers do not resonate in antiphase. There have
been reports of parallel drivers doing strange things under
heavy drive (excursion limiting) that doesn't seem to be
such a problem if wired in series. The problem is caused
by deficiencies in the motor design of cheap drivers and
is not universal.
Its not a resonance issue, its a stabilility issue. Single
drivers with too linear suspensions can "pop" under
heavy drive, due to falling inductance drawing more current
literally "popping" the driver further out of the magnet gap.
(Usually due to assymetry it happens fore or aft for a driver,
and aft it can damage a driver by battering the "endstop".)
And this won't symmetrically happen with two parallel drivers.
One or the other will go first, and if repeated a complex
swapping pattern can develop between the two drivers.
The nub of the idea that series drivers are better is that
of course they must pass the same current, and that by
definition will increase the difficulty of "popping" occurring.
Whether its a problem or not depends on the driver design.
There is no universal principle series drivers are better.
There is no antiphase resonance between parallel
drivers that your "expertly" waffling on about.
Its clear from many posts you severely overate
the veracity of your opinions as almost fact.
The fact is you don't know enough to go round
telling other people that they don't, its tedious.
rgds, sreten.
Most of the time I just ignore opinions presented
as fact, life is too short, but this thread has taken
a wrong turning, into a sea of half baked opinion.
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Let's define terms.
Combing is where you have two identical drivers in a vertical array. Above and below axis, you get an interference pattern of peaks and nulls dependent on frequency. It's similar to double-slit diffraction in Physics.
Nevertheless, multiple drivers have a considerable strength of projection and efficiency that is exploited in PA systems. Combing is less of a problem in the far field.
Lobing is a characteristic of odd order filters even when time-aligned. What is it? 15 or 25 degrees at crossover, I can't remember. LR4 time-aligned has no lobing, but then has a -3dB power falloff at crossover.
MTM D'Appolito is an attempt to correct the lobing with BW3. But it misses a trick because the power falloff with distance is different for the twin woofers and the single tweeter. The woofers tend to a cylindrical inverse-distance falloff, the tweeter has a spherical inverse-square falloff. So the sound balance changes with distance.
As for the series wiring, if you wonder how two parallel wired woofers in the same enclosure can behave differently and interact when connected to the same voltage source, think of a car differential:
How Differentials Work - HowStuffWorks
One back wheel can be stationary while the other one spins twice as fast.
You can take it or leave it, but mainly ENJOY building your speakers! It's all good fun.
Combing is where you have two identical drivers in a vertical array. Above and below axis, you get an interference pattern of peaks and nulls dependent on frequency. It's similar to double-slit diffraction in Physics.
An externally hosted image should be here but it was not working when we last tested it.
Nevertheless, multiple drivers have a considerable strength of projection and efficiency that is exploited in PA systems. Combing is less of a problem in the far field.
Lobing is a characteristic of odd order filters even when time-aligned. What is it? 15 or 25 degrees at crossover, I can't remember. LR4 time-aligned has no lobing, but then has a -3dB power falloff at crossover.
MTM D'Appolito is an attempt to correct the lobing with BW3. But it misses a trick because the power falloff with distance is different for the twin woofers and the single tweeter. The woofers tend to a cylindrical inverse-distance falloff, the tweeter has a spherical inverse-square falloff. So the sound balance changes with distance.
As for the series wiring, if you wonder how two parallel wired woofers in the same enclosure can behave differently and interact when connected to the same voltage source, think of a car differential:
How Differentials Work - HowStuffWorks
One back wheel can be stationary while the other one spins twice as fast.
You can take it or leave it, but mainly ENJOY building your speakers! It's all good fun.
Now load both sides of the differential equally. Why would one side spin any faster?
Ohm's law clearly shows that two identical resistors connected to the same voltage will pass the same current.
Now introduce a complex impedance, where the current flow has frequency-dependence. Both impedance curves are identical, since the same woofers are sharing the same cabinet.
At any given frequency, the two woofers have identical impedance, and are connected to the same voltage source. The same current must flow through both.
This is very frustrating, as you keep repeating the same thing, with analogies that simply don't hold.
The differential, for example, could be seen as a constant-current drive into unequal resistors. Of course the two resistors will see different current: they have different resistance!
Most amplifiers are voltage source, and, for the purposes of this discussion, the resistance is equal.
Chris
Let's define terms.
Combing is where you have two identical drivers in a vertical array. Above and below axis, you get an interference pattern of peaks and nulls dependent on frequency. It's similar to double-slit diffraction in Physics.
Lobing is a characteristic of odd order filters even when time-aligned. What is it? 15 or 25 degrees at crossover, I can't remember. LR4 time-aligned has no lobing, but then has a -3dB power falloff at crossover.
MTM D'Appolito is an attempt to correct the lobing with BW3. But it misses a trick because the power falloff with distance is different for the twin woofers and the single tweeter. The woofers tend to a cylindrical inverse-distance falloff, the tweeter has a spherical inverse-square falloff. So the sound balance changes with distance.
You can take it or leave it, but mainly ENJOY building your speakers! It's all good fun.
Lobing vs. combing is still a distinction without a difference. The terms are interchangable. Combing tends to imply a greater number of nulls causing the plot to look like the teeth of a comb, but they are both similar forms of lobing. As to far field audibility, that certainly is unconnected to root cause.
In both cases we are discussing the interference pattern seen in the farfield when multiple elements are radiating. It doesn't matter if some are mids and others tweeters, or if a crossover point is involved, the goal is to achieve as smooth a polar pattern as possible. If off axis nulls are inevitable then we aim for the widest vertical angle before the nulls.
Sound balance vs. distance is a very minor effect in the dual woofer case. Even long arrays at high frequencies eventually settled down to 1/R drop as you move away (see my AES paper on the subject if you are interested in data). This can be a factor when longer lines are crossed to single woofers but the error is slowly changing and dealt with by voicing at a typical distance, as I did with the Mac XRT 24. I've never measured any significant effect in the dual woofer case.
The problem with stating your opinions so strongly is that you are bound to look silly when errors are pointed out.
David
My new fave quote
BTW - I miss the Snell guys!,.. you, Bob and Wally were the best!
BTW - I miss the Snell guys!,.. you, Bob and Wally were the best!
Indeed. But I'm still waiting to hear what the errors in my MTM analysis are.
There's a lot of good people here, but a few duffers too. It is my thankless task to ruthlessly expose them. It doesn't make me popular, any more than correcting people's grammar does. Do you guys still not instantly grasp the difference between a series wired MTM and a parallel wired one? You amaze me. They are wired opposite!
My new fave quote
BTW - I miss the Snell guys!,.. you, Bob and Wally were the best!
Yes, good times. Were you a Snell dealer?
David
Indeed. But I'm still waiting to hear what the errors in my MTM analysis are.
See the posts above.
It really isn't.
No. Superiority complexes are not generally appreciated, nor do people take kindly to being patronised -especially when [for example] the person who claims to be 'correcting grammar' is in fact indulging themselves in linguistic semantics on a topic where the terms are commonly employed interchangeably.
Do you guys still not instantly grasp the difference between a series wired MTM and a parallel wired one? You amaze me. They are wired opposite!
What is apparent is that you are alone in holding the views you propound above, which you have yet to support with direct evidence. Since you are presenting a view not popularly held and apparently contrary to basic engineering (perhaps you mean something different but have not stated it sufficiently clearly) the onus is upon you to support it, not the other way around.
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The true test of any theory is how it translates the real world.
Let's suppose we have a fully functional PAIR of MTTM speakers. What is going to happen to the imaging, in a stereo pair, with a second point-source HF driver in each speaker?
It's a rhetorical question to provoke thought, as I already know the answer.
Let's suppose we have a fully functional PAIR of MTTM speakers. What is going to happen to the imaging, in a stereo pair, with a second point-source HF driver in each speaker?
It's a rhetorical question to provoke thought, as I already know the answer.
It's a pity you chaps can't meet up in a pub and discuss properly. I'm sure that you would reach a consensus as you would all be peer reviewing ad hoc. Much more gentlemanly. You have me at a disadvantage as I'm not electrically biased.
I've been looking into this subject,have made some posts and have received good advice. I have also come across Tony Gee and his Proteus "Wilson audio CUB" homage. He advocates a completely different argument only using second and first order filter's.
The reason as to why I'm drawn to the cub is It's like a hybrid LS5/9 and to be copied must be a renowned product but would Wilson audio use what Tony Gee advocates? Looking at the rear it would seem so, I'm no expert.
I've been looking into this subject,have made some posts and have received good advice. I have also come across Tony Gee and his Proteus "Wilson audio CUB" homage. He advocates a completely different argument only using second and first order filter's.
The reason as to why I'm drawn to the cub is It's like a hybrid LS5/9 and to be copied must be a renowned product but would Wilson audio use what Tony Gee advocates? Looking at the rear it would seem so, I'm no expert.
Dave,
Curious what crossover orders you used in the XA series on the MTM.
(your profile pic is an XA Ref if I'm not mistaken?,.. outstanding speaker!)
In some of the D'Appolito designs I can hear a phasing mismatch between the mids and tweeters,... but I did not witness the same of the XA's.
Curious what crossover orders you used in the XA series on the MTM.
(your profile pic is an XA Ref if I'm not mistaken?,.. outstanding speaker!)
In some of the D'Appolito designs I can hear a phasing mismatch between the mids and tweeters,... but I did not witness the same of the XA's.
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