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Old 23rd July 2010, 06:41 AM   #6771
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Originally Posted by soongsc View Post
Ahh, now I have some idea what the Ariels might sound like. I've listened to their 30th aniversary model (can't remember the exact name), and also the some of the Evidence series.
They aren't exactly the same. The Dynaudios have stupendous dynamics for a low-efficiency speaker. I'm actually at a loss how the SC X manages to be as inefficient as it is: they claim 86 dB/metre/2.83V, with a 4-ohm impedance no less, which implies that each 7-inch driver is an astounding 83 dB/metre/2.83V. The Esotar tweeter has to be around 90 dB, if it's anything like the classic Esotar, so the low efficiency rests with the pair of 7-inch drivers. Maybe the voice coil is very long and mostly out of the gap; I dunno. The Ariel is a genuine 92 dB/metre/2.83V, so there's a big difference there.

The Ariels do not sound good on most transistor amps - flat and 2-dimensional. Even so, they are better than the Sonus Faber Cremonas, which had much more limited dynamics than I expected, based on the glowing reviews. Nice balance, no obvious and gross flaws, and attuned to acoustic music, but dynamically less than the Ariels by maybe 5 dB or so. Higher efficiency always helps with dynamics, both micro and macro.

The Dynaudios might have a slightly cooler balance, but I'm not sure about that. In terms of transparency and immediacy, they are quite similar - this was the big difference between the Dynaudios & Ariels compared to B&W, which I found very, very disappointing. The Kevlar midrange coloration was very obvious, and the crossover evidently doesn't bother to filter it out. The metal-dome tweeter had the usual generic metal-dome coloration in the upper treble. It just didn't sound all that good on the kind of acoustic music I like - maybe for recordings of heavy-metal rock concerts?

There are lots of high-end speakers where I just don't understand the appeal. Anything by Wilson, for example. Never liked the Watt/Puppy when it first came out, and I don't like them today. Wretched tweeter with obvious and impossible-to-ignore resonances, a colored and coarse-sounding midrange driver, grossly over-emphasized bass, and a crossover with poor driver integration. I guess the cabinets are good if you ignore diffraction. This is a speaker I just don't get, never mind the price. I don't see the appeal at $100 each, much less $20,000 or more.

Don't get the Magico Minis, either. A tipped-up minimonitor with constrained dynamics is what I hear, with some nasty upper-mid and HF resonances. No thanks.

My only conclusion is that audio reviewers have weird tastes, or at any rate, tastes that have little or nothing in common with mine. The kind of records they mention in the reviews is music I despise and wouldn't listen to if you paid me. Sonically, they're on a different planet than I am - most of the reviewer-speak is just gibberish to me. I've heard some of their own systems in their own homes, and I just didn't understand why they liked what they were listening to.

It gets embarrassing when I'm asked point-blank "how I like it". This has happened more than once; the dealer or reviewer just wouldn't give up, and kept pestering me to tell them what I really thought - well, I told them and didn't get asked back. Ever. This has happened several times, so I try my best to just keep quiet and not say anything at all.

In a way, it simplifies show-going. Most of the rooms drive me out within seconds. A few other rooms, the exhibitors throw me out when they hear my demo material. A few rooms might sound interesting, so I rush around and try to find them before the show ends. Maybe one, two, or three might sound really good. I try and give these a writeup when I find them. It doesn't mean that I'd necessarily like them in my own home, it just means it was a fun discovery at the show. A few that come to mind are Dr. Geddes' Summa, anything by AudioKinesis, the Orions, the Harbeth and Spendors, the Oswald's Mill Audio system, and a few others. All fun and enjoyable. The others, not so much, so I keep on walking.

Last edited by Lynn Olson; 23rd July 2010 at 07:06 AM.
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Old 23rd July 2010, 06:52 AM   #6772
sba is offline sba
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Twice a week I do volunteer work at a resale shop, where some little old ladies sort out the donations and put aside all the electronic stuff , and anything else that gets “plugged in“, for me to test.

Tons of Sony, Denon, Onkyo, Yamaha, & Pioneer HT receivers come through. Many of them are DOA ( and at a very young age), while the rest just sound dismal at best.

Even worse than the mediocre sound are the poor designs that are so counter-intuitive to good function. I‘m always wondering when I come across this crap, “whatever happened to intelligent industrial design?” I used to be able to figure out how to operate a receiver by just looking at it from half way across the room (like with a Marantz, for example). Now I need glasses and a flashlight just to find the basic functions, which, even then, might require several steps to get at.

Every once in a while something decent will come in. Last week it was an early 90’s Yamaha receiver, and one with a big power supply. (the model number is….hold on, let me get my glasses and a flashlight…..okay, it’s rxv870) The display light had gone out, so, as usual around here, someone just donated it. It’s in my office now and sounds super…the only decent sounding Yamaha that I’ve heard…out of hundreds. Thanks, in part, to a decent power supply.
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Old 23rd July 2010, 10:43 AM   #6773
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Originally Posted by mige0 View Post
Reply to your review, John



Ad 6)
A paradox situation at a first glance, but I hold to my position as clearly shown in my simus. The point to focus at is, that the “summation to null” is a process *after some time* and not an immediately process (hence your math is incomplete).
Meaning we can add any signal we like at any time we like – the overlay towards “summation to null” will happen later - so “the signal of desire” can *always* be created until overlay with the virtual source happens.
As the overlay always happens later on, we can push and push and push just as may times we like.
That we will rapidly run out of steam is quite another thing (as said: ”practically” out of reach forever, though *theoretically* possible).

Michael
I don't have to refute any of this. What I have said covers it all. 1) The output of a system is the input signal convolved with the system impulse. 2) Any MP response can, (in theory), be equalized to any other desired MP target response using MP equalization and the impulse of the equalized system with be that of the target.

If your results don't agree with those two statements then they are incorrect. You have pontificated for several pages on this subject and all you have done is to obfuscate what was my correct response to Lynn initial statement about equalization in the frequency domain making things in the time domain worst.
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Old 23rd July 2010, 12:57 PM   #6774
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Originally Posted by gedlee View Post

That there is some transfer function F(w) that when multiplied by the rear source will yield an ideal cardioid polar response should be apparent. It's easy to show. It is also obvious that achieving this polar response will also require additional EQ to the "system" to make the axial response flat, so lets call this transfer function G(w). Hence, if we source the front driver with G(w) and the rear driver with F(w) * G(w) we will simultaneously achieve both a flat axial response AND a polar cardioid response - the ideal. Now how close can we get to this ideal if we 1) don't want cardioid down to low F's and 2) we want to do it passively. That I do not know, but its an interesting exercise. But I don't think that your comments shed any light on the answer.
Backman showed that it is possible to use an all pass filter so that at low frequency the front and rear source sum in phase and as the frequency rises the all pass delay combines with the source separation to yield a cardioid, but as the frequency continues to rise the polar pattern continues to morph since the all pass delay is not constant. I have experimentd with Backman's approach and never found it very satisfactory. I would like to see what what your transfer function isas I seem to have missed it.

In the case of real drivers, the rear (180 degree) response from the front driver is either equal to that on axis (wave length large compared to source and box dimensions, below the baffle step) or has some frequency dependence (above the baffle step).

If I consider the figure to the left below,

Click the image to open in full size.

representing a speaker box with front and rear mounted drivers. The circle represents the polar response of the front source at frequencies where the wave length is much greater than the box dimensions, so the response is omni-directional. If I look only at the response at 180 degrees, then the question is what would the rear driver have to radiate to null the response at 180 degrees? Obviously the amplitude would have to be equal to the amplitude of the front source at 180 degrees, which is just the amplitude at the front source since it is omni at this frequency. The rear source's phase would have to be 180 degrees relative to the front source plus a delay defined by the additional propagation distance the front wave must travel around the box. This is on the order of d/c. This is the classic two source cardioid generated using two omni source (conventional drivers at low frequency).

Now looking at the figure to the right. Here we are looking at the polar response of the front source at higher frequency where the box shadows the response. So the polar pattern is no longer omni. It is weaker to the rear. At 180 degrees, to null the response, the rear source would again have to match the back side amplitude from the front source with inverted phase (now less than the front source on axis) with the addition of the same delay due to propagation distance differences. Of course, the polar response of the front source will change as the frequency changes once the box shadows the front response, much like a disk at the end of a long pipe. In any event, I would agree that it would be possible to high pass a rear driver so that at low frequency only the front, omni polar response would be obtained and at higher frequency, where the box shadows the front response the rear source could have its amplitude tailored to null the 180 degree response. But a delay would still be required due to propagation distance differences and while the 180 degree response could be nulled, the radiation pattern of the rear source would have to have very unique characteristics to create a classic cardioid, or so it seems. And the rear source would potentially still have some effect on the on axis response of the system, thus requiring additional eq as you note.

But over all this seem very little different than just choosing a baffle size so that the transition form 4Pi to 2Pi radiation occurs over the frequency range of 100 to 200 Hz, no?
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Old 23rd July 2010, 02:22 PM   #6775
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Originally Posted by john k... View Post
But over all this seem very little different than just choosing a baffle size so that the transition form 4Pi to 2Pi radiation occurs over the frequency range of 100 to 200 Hz, no?
I don't know, I'm not sure that I understand the comment. In my model this transition occurs naturally so its not something that can be gleaned by looking at the curves.

What I did was to model a piston in a sphere - complete polar and frequency response at all far field points. Now take this model and add to it (superimpose) the same model rotated by 180 degrees, this represents the forward and rear facing sources (equal in area for simplicity, but this is not required). By finding a transfer function for the rear source that exactly causes the rear radition to be zero, everything is accounted for, including diffraction (2Pi to 4Pi transition) etc. The exact solution does have delay requirements, but I simulated doing this without delay as well. You cannot get a pure cardiod without delay, but you can get some directivity.

Whats the advantage over an OB - clearly efficiency - it can be a monopole at LF so that there isn't the low efficiency dipole problem which requires seperate amps and EQ. Having now tested the Orion, the EQ and all the amps required are a real killer of value in that design. Is there a way to get the Orion directivity at LFs without the need for that extreme level of complexity and cost?

If I get some time I'll post the curves that I derived.
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Old 23rd July 2010, 02:56 PM   #6776
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I guess the question I would ask is , over what frequency range? Clearly the piston in a sphere is omni directional at low frequency. So it seems to me, since you are interested in omni at low frequency, you are using the high passed rear driver to cancel the rear radiation form the front driver in the baffle step and above range. I.e. where the front piston does not radiate omni directionally. Be it a sphere or box, it seems you are looking at frequencies where the front driver directionality and size of the spherical enclosure (or box) are limiting the magnitude of the rear radiation of the front piston. No?

Certainly if I place a mic at 180 degrees and measure the response I can generate the inverse transfer function and HP filter it and correct the delay to null the rear radiation as a function of frequency. I'm just not sure what that would actually do to the on axis and polar response????
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Old 23rd July 2010, 04:20 PM   #6777
gedlee is offline gedlee  United States
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Originally Posted by john k... View Post
I'm just not sure what that would actually do to the on axis and polar response????
Thats in my book, but, as I said, if I get the chance I will post the figures.
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Old 23rd July 2010, 04:33 PM   #6778
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Originally Posted by Lynn Olson View Post
They aren't exactly the same. The Dynaudios have stupendous dynamics for a low-efficiency speaker. I'm actually at a loss how the SC X manages to be as inefficient as it is: they claim 86 dB/metre/2.83V, with a 4-ohm impedance no less, which implies that each 7-inch driver is an astounding 83 dB/metre/2.83V. The Esotar tweeter has to be around 90 dB, if it's anything like the classic Esotar, so the low efficiency rests with the pair of 7-inch drivers. Maybe the voice coil is very long and mostly out of the gap; I dunno. The Ariel is a genuine 92 dB/metre/2.83V, so there's a big difference there.
Hello Lynn,

I have never found the 2 to be mutually exclusive, having high efficiency doesn't mean having bigger dynamics, interesting you should say so...
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Old 23rd July 2010, 04:51 PM   #6779
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Generally speaking, lower efficiency speakers do not have the headroom that high efficiency speakers have. While there are some exceptions, my experience parallels Lynn's.

Best,
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Old 23rd July 2010, 05:01 PM   #6780
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Originally Posted by chrismercurio View Post
Generally speaking, lower efficiency speakers do not have the headroom that high efficiency speakers have. While there are some exceptions, my experience parallels Lynn's.

Best,
Thirded. It's not always true, but usually.
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