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In Reply to: Re: Why Isn't The Research Being Done? posted by AJinFLA on April 10, 2007 at 17:56:35:
Hi AJ,Yes, by that comment I meant listening to the binaural recording through headphones. I have not listened to them through my Sequence speakers, but when played over other speakers the sound is unimpressive, nearly mono.
I am interested to hear some of latest class-D amplifiers. Some colleagues believe the Hypex UcD designs might yield the best sound of the genre. I do have some of their modules with plans to use them for a dipole woofer plate amplifier. If that goes well, I'd like to hear them full-range. I've read good reviews of the Channel Island Audio monoblocks which are based around the Hypex units.
Unfortunately no progress on an NRT coax speaker - AuraSound has been swamped with many OEM projects. I do want to get to it this year.
As for a dipole coax, a similar concept "dipole point source" has been done before with the Quad ESL-63 electrostatic loudspeaker. It sounded good but has its faults. And any wide dispersion point-source is going to cause floor reflections, so I wouldn't immediately say a dipole coax or point source is the ideal format.
Follow Ups:
I will of course match levels as close as possible, then A/B switch between the D2A and a couple Class AB, a friends Class A and a Tripath amp. If I think I can discern a difference, then I will repeat with someone else doing the switching for me.
I have also heard good things about the Hypex. As you already know, I believe there are only extremely subtle differences, if any, between good amplifiers and highly dependent on the reactive load they are connected to.
Good to hear about the company being busy. Not a bad thing at all.
The JBL's will do just fine until you are ready. Were the Aura's to be a similar rigid cone HE mid/tweeter design? BMS has some interesting models, but paper with woofer surrounds, so still non-ideal like the JBL. But neo motors. Something the JBL could use. The motor is the same diameter of the driver, so rear masking is a real concern.
Yes, the Quad was something of an inspiration, but as you said, had its issues. But all speakers do. Even if they were perfect, recordings are still far from.
Now as far as floor reflections go, I have to disagree with you there as it being a primary consideration in my design. We grew up with and live with floor reflections. It is an everyday life distortion that our brain filters well. I have yet to hear a live music performance where it did not exist :-). Of course, in a home, it can be excessive. I could direct a dipole null towards the floor, but this of course comes at a price.
Linkwitz noted that in going from the freestanding Phoenix, with a dipole null directed to the floor and the Orion, a floor stander, there will no noticeable loss in clarity from the increased floor reflections. I'm not saying its a bad thing to have in your speaker design, but it will be very far down the list for me, in order of importance. An example would be, if I directed a null at the floor by creating an acoustic short circuit on the main panel, this would increase the roll off, which would have to be compensated for by increasing the displacement requirement of the midbass for the same SPL and in doing so increase distortion, decreasing dynamic capability, etc. No free lunch.
Still need to hear your Sequence, but if it had increased midrange clarity and openness over a boxless W22, I'd be shocked. Never mind the huge 3D soundstage that extends beyond the confines of the listening space. Even using a SS HK receiver LOL.
Sticking with dipole coaxials for now. I've now seen several pop up around the web over the last few years, and there has been a buzz of late, including a lengthy discussion going on now on DIYAudio. I had a discussion with John K over on Madisound a couple years ago about coaxial dipoles/power radiation into a room and he too mentioned the Quad. Must have been quite the thing back in the day.cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
Yes, real life has floor reflections, but they are already captured in the recording. If one deems the goal of hi-fi is to accurately reproduce the recording in room, at the listening position, then the floor reflection from the speaker is an immediate deviation from this goal. Read some of Robert Greene's articles in The Absolute Sound. Here are a few from his website:
http://www.regonaudio.com/Gradients.html
http://www.regonaudio.com/SpendorSP12Loudspeakers.html
http://www.regonaudio.com/Snell Type B Loudspeakers.htmlTo reduce the floor reflection in a speaker requires a radical design. Linkwitz's Phoenix will encounter the usual ~300Hz floor dip, ~600Hz peak, etc., comb filtering from the floor reflection because a dipole is only ~3dB down at 37 degrees off axis, the angle of the floor reflected sound with a typical 36" tweeter height and ear height, and 96" listening distance.
I believe and people who have heard my Sequence speakers concur that they have excellent clarity. This is due to a few reasons:
1. Narrow dispersion with reduced floor, side wall, and ceiling reflections
2. Choice of midrange driver. In all my years as a speaker designer, it is the only midrange which nearly perfectly reproduces an impulse response as measured with MLSSA, among other attributes. No metal cone midrange I've tested can remotely make a similar claim.
3. Because of the choice in midrange driver, I run them higher than normal in frequency before crossing over to the tweeter.
4. Also because of the choice in midrange driver, its crossover is simple with minimal components and added attenuation. No metal cone midrange I've tested can make a similar claim.Dipoles do have a spacious soundstage, but I believe it is less accurate to the recording. Listen to your speakers outdoors and hear the difference due to the room.
Quad's current generation electrostatic speakers also are designed to function as dipole point sources.
Floor bounce being captured in the recording is highly recording dependant. There is no way to to accurately reproduce the recording in room, once the signal passes the amplifier enters the 3D power radiation of a loudspeaker system, unless it is an exact replica of the recording studio (loudspeaker/room).
The floor reflection may be one deviation, among a thousand. A comprehensive in room measurement of your speaker system vs the studio would quickly reveal that.
I have no idea who Robert Greene is, although I know what the absolute sound is. I do not read that sort of magazine.
I have heard speakers from each of those manufacturers. The Gradient being the best. Even those pale in comparison to an Orion, almost laughably so. Geddes used a Revolution when designing his Summa and it was a statistical dead heat in unsighted tests amongst a listening panel. I know those are are utter blasphemy in audiophile circles, to be avoided like the plague, but it would be nice to see an unsighted comparison of the Sequence, Orion, Revolution and Summa.
I don't think I would be suprised by the outcome.
I have no doubt that your speakers possess a lot of clarity, as expressed by some listeners. I would like to hear them myself.
I have never seen a set of measurements for them. On and off axis FR, DI, linear & non-linear distortion sweeps, *system* impulse response, etc.
How do you prevent sound re-radiation through the midrange cone diaphragm from inside the enclosure? Does your enclosure store energy? How is it released? Is the reverberant soundfield as linear in all directions as possible?
What about the impulse response of the mid driver is not shown in the FR? What is its relevance unfiltered?
What about the CSD? Is distortion as low as a metal cone *when used in the complete system, with filter network? Is the mid driver in breakup mode in its upper range? Are there flexing and bending modes? Is it behaving like a rigid piston? Why does a highly lossy medium best preserve signal integrity and minimize signal distortion?
I would still love to see the FR at varying vertical and horizontal angles with the high tweeter xo, where the tweeter is still near omni even with the small horn and a beaming mid.
I don't have any components other than wire between my amplifier and drivers, so I guess I'm a minimalist too :-).
The spaciousness of of a well positioned piston source dipole may indeed be less accurate to the recording, but more accurate to the illusion of live sound reproduction, which is what I'm really trying to accomplish, so I'll take the latter.
I have listened to my speakers outdoors, that is where I like to measure! Of course, I usually listen indoors, in an acoustically small room, which is precisely why I prefer a dipoles DI and power response.
Any Sequence dealers down in the South East?cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
I recommend you read some of Robert Greene articles. He seems to be a pretty smart guy, not to mention mathematics professor at UCLA and also a musician.My personal paradigm for a loudspeaker system is to reproduce the original recorded signal with minimal influence from the room of the reproduced sound at the listening position.
Some recordings sound like a live event because they are recordings on a live event. Others were generated in a studio, possibly purely electronically, and have no semblance of a live sound event. Of course no recording replayed through speakers, in my opinion, is remotely close to sounding like a real, live event as do binaural recordings through good headphones.
How did your speakers sound when you listened to them outdoors?
You ask many questions about my Sequence speakers. I'm not prepared to answer them all at this time, but have investigated each and every issue you mention. Here are a few comments:
1. The CSD on the midranges is excellent on a baffle and in the enclosure. Linkwitz himself liked the HDS variant of the driver and spec'd it into his Pluto system until they were no longer available. I purchased quite a few for my Sequence model.
2. The distortion on this particular driver is very low as I personally measured on a B&K 2012 and Listen SoundCheck system. Use 4 together in unison and the distortion is further reduced.
3. I have laser scanned at AuraSound many high-end 5 - 7" midwoofer transducers. ALL (paper, plastic, metal, carbon fiber, honeycomb, etc) begin their bending modes below 400 Hz. Some drivers behave uglier than others with increasing frequency. No cone driver that I have ever encountered and tested is a rigid piston in the midrange. A rigid metal or ceramic dome midrange might.
4. I recommend you and others read some of Harbeth's investigations into the behavior of cone materials versus frequency.
5. The Sequence midrange enclosures are purposefully braced, damped, and use acoustical absorptive material. How well they behave can be measured using energy-time and CSD plots.
6. Due to the gentle slope of the crossover between the midranges and tweeter, there is moderate overlap, causing further increased directivity up into the treble. Remember, I'm not using 24dB/oct slopes, so there are no abrupt changes in directivity. Only at around 8kHz is the tweeter doing most of the work and at this frequency is already down 5dB at 30 deg off axis. Together with the carpeting on the floor and there is miminal floor reflection of the tweeter's sound.In the end what matters is whether one likes the sound or not. I have no dealer for the Sequence back east at this time, but you're welcome to hear them in Los Angeles.
DN - I recommend you read some of Robert Greene articles. He seems to be a pretty smart guy, not to mention mathematics professor at UCLA and also a musician.I just started to. My apologies for not knowing who he was, he measures and listens. I will certainly pay him more attention, although I will still regard that magazine more as The Absolute Nonsense, than anything resembling readable material.
DN - My personal paradigm for a loudspeaker system is to reproduce the original recorded signal with minimal influence from the room of the reproduced sound at the listening position.
A worthy position. I'll use unavoidable room influence to enhance the illusion that I am not listening to loudspeakers or a recording.
DN - How did your speakers sound when you listened to them outdoors?
Like pink noise:-). I'm waiting on the recent rains to subside so that I can attempt a crude experiment. An H-frame with a single XLS Peerless and an identical size sealed box with 2 XLS in dipole configuration. To be listened to outdoors (on the ground) at equal radial distance about a foot apart. Mainly test tones, but maybe some (bass) music too, to see if I can hear a difference. John K is of the opinion that at subwoofer frequencies, it is the radiation pattern, not the unimpeded rear wave that determines the aural characteristics.
DN - You ask many questions about my Sequence speakers. I'm not prepared to answer them all at this time, but have investigated each and every issue you mention. Here are a few comments:
1. The CSD on the midranges is excellent on a baffle and in the enclosure. Linkwitz himself liked the HDS variant of the driver and spec'd it into his Pluto system until they were no longer available. I purchased quite a few for my Sequence model.The Peerless composite cones were my favorite non-rigid. I've owned a pair of the HDS5.5's like Linkwitz used since about 2 days after Madisound first introduced them. 1999? Used them with a D25AG35 Vifa in a little desk top monitor circa '99.
DN - 2. The distortion on this particular driver is very low as I personally measured on a B&K 2012 and Listen SoundCheck system. Use 4 together in unison and the distortion is further reduced.
Distortion is frequency dependent and involves the motor as much as the cone, as you well know. Would distortion be lower than a W18 anywhere but near the resonance peak frequencies?
The one question I would like you to answer as a driver designer, is
Why does a highly lossy medium best preserve signal integrity and minimize signal distortion?
DN - 3. I have laser scanned at AuraSound many high-end 5 - 7" midwoofer transducers. ALL (paper, plastic, metal, carbon fiber, honeycomb, etc) begin their bending modes below 400 Hz. Some drivers behave uglier than others with increasing frequency. No cone driver that I have ever encountered and tested is a rigid piston in the midrange. A rigid metal or ceramic dome midrange might.The question is which will act more like a rigid piston, not be a rigid piston. Soft cones need not apply here.
DN - 4. I recommend you and others read some of Harbeth's investigations into the behavior of cone materials versus frequency.
I will. Although I have never heard a Harbeth that I would even consider decent. Just another box with vertically aligned, uncorrelated, uncontrolled directivity drivers. Yuck/yawn.
DN - 5&6) I'de still like to know how sound re-radiation from the box through the thin cone is addressed. Also, the off axis data will tell me how much comb filtering will occur from the uncorrelated drivers. Higher XO = higher wavelength separation.
DN - In the end what matters is whether one likes the sound or not. I have no dealer for the Sequence back east at this time, but you're welcome to hear them in Los Angeles.
But of course. Much like you favor tubes, for me, listening to non rigid cones is like listening to a speaker with a veil in front of them. Even if they (rigid cone/low distortion motor) reveal the poor sound of a recording, I know that logic dictates that one blames the recording, not the speaker.
I'll keep an eye out for the NRT coax and pray that its an aluminum cone :-). If I'm ever out that way, I'll drop in for sure.cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
The 5.5" Peerless sandwich cone drivers have low distortion from 100 Hz on up. Below 100 Hz, the distortion will begin to rise with decreasing frequency due to gradual reduction of suspension and motor linearity. A well-designed 8" woofer should have lower low frequency distortion than a 5.5" for the same SPL. However a quartet of 5.5" midranges has a lot of surface area, so for the same SPL, the distortion will be very low, even below 100 Hz, due to the low cone excursion.There are many factors which determine the sound quality and signal integrity: cone material and its physical properties, cone geometry, dust cap material and geometry (if there is one), type and quantity of adhesives used, voice coil bobbin material, surround material and geometry. Cone/dust gap geometry are more significant contributors to the rigidity of the moving diaphragm than the cone material. This is why all the 5-7" midwoofers I laser scanned entered their bending modes at or below 400 Hz. This includes the Seas Excels with magnesium cones that I tested. The aggregate combination of all these design elements of the diaphragm assembly determine the impulse and frequency response, and energy-time and CSD behavior of the driver.
I think your aversion should not necessarily be to non rigid cone drivers but to drivers which store energy. I don't like drivers which store energy either.
I've disclosed all details about the design of the midrange module to which I am willing at this time. One of these days I will post measurement data for the speaker on my site. I'm pleased with their measured performance, and they correlate with my claims.
Given your preference towards dipole midrange speakers, I think you will find the Sequences dry and not as spacious as you like.
Hi there!Many years ago I did something with some similarities. I had a pair of Radio Shack PZM microphones mounted on opposites sides of a board and through open air headphones, I perceived some household sounds coming from behind me. I can't remember the details of what I did anymore.
As well, somewhere I have a binaural recording that came with an Audio magazine, and it will give surround sound through open air headphones, too. Indeed, I think it gave me the idea of doing the above, though I had no Kunstkopf.
Another recording made using a Carver processor can produce sounds from stereo speakers which seem to come from behind if sitting in the sweet spot.
I wish I had been able to get down to hear a system developed by James D. Johnston while he was with AT & T. But Wes Philips and John Atkinson have heard it, and Wes Philips has commented on it. See the link below.
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"Opposition brings concord. Out of discord comes the fairest harmony."
------Heraclitus of Ephesis (fl. 504-500 BC), trans. Wheelwright.
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