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Old 13th September 2007, 10:35 PM   #1991
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AJinFLA

Your focus on “soft” vs hard was not addressed.

I mentioned damping, mechanical loss within the radiator is very important.
One cannot avoid chaotic behavior past the upper limit of the piston range unless one has lots of loss. A good soft dome is an example of this, the driver is mostly in non-piston mode but has no pronounced resonances.
The best driver (in time) I ever measured was a Manger bending wave transducer, it is a resistively dominated device, very high mechanical losses, low stiffness.
This sounds like the way to go except that mechanical resistances tend to change with time, change with temperature and change with use and are progressively non-linear.
The down side of the Manger was that at 1 volt is that it is already pretty high in distortion (a few %) at 200Hz. They (with a subwoofer) would make a superb desktop stereo though.

For a radiator, it is difficult to keep the mass low enough and have a high enough break up AND have enough damping to kill the Q’s.
Not having a perfect radiator, one can say a low Q resonance is better than a high Q one, a 3 dB peak is better than a 10dB peak and so on. All this you can see when/if a response curve is provided.
Also, while one can filter the drivers breakup with DSP, one cannot fix the fact that the acoustic gain magnifies the natural distortion at sub-multiple frequencies.
That is not to say such a driver can’t sound great, what you hear is so much more than that one aspect of its performance.

“I see no crossover frequencies for the SH-50. Nor do I see a laser scan of the mids, whatever they may be. As a matter of fact, based on the Yorkville design, I see what appears to be closed back mid drivers. Is this the same in the Synergy? If so, can you tell me how the rear wave off the driver cone is 100% absorbed in that minuscule chamber and not reflected and re-radiated through the paper thin membrane, delayed in time to the original?”

The crossovers are about 350Hz and 1400Hz in the SH-50.
The mids are made to spec, they are closed back type.
Again the answer is in thinking of the acoustic dimensions, the rear radiation is not an issue, here is why. At the highest frequency the mid drivers go to (lets say 1500Hz), the wavelength is about 9 inches. The back cover is about 1 / 2 inch away from the cone which is far less than the 2 ¼ inch distance which could cause the first reflection notch (at 1500Hz). The rear cover is so close, it can’t cause a reflection in its operating band.

“To me, paper coloration is an association of amplified music.”
Yes but if you make speakers that are also to produce natural sounds (not generally harmonic in nature) are to be faithful to the recording, you don’t want any coloration.

On the other hand, one form of coloration is one which I don’t know the name of, but can describe.
In one case, with music or voice you can with your eyes closed you can easily tell how far away the speaker is, in another, you have no idea how far away it is.
In one case, a pair of one kind and a pair of the other gives radically different stereo images even if the responses are similar.
The one with no clues as to distance makes a much better stereo image.
I think that the source interference that lets you localize the actual depth of the speaker harms or competes with the stereo clues.
Coming a full circle, one finds that a single full range driver (which usually has a low mass thin paper cone) is the simplest emulation of that non-interfering source, the goofy horns I make at work at the large end of the scale.
Hope that helps,

Tom Danley
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Old 13th September 2007, 10:54 PM   #1992
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Default Magico Mini


Did a little digging and found the driver used in the much-hyped Magico Mini - here. Want the awful truth? Here's the frequency response. Want to make any guesses whether that kind of curve is correctable with any kind of equalization?

Note carefully the published reference efficiency - 86.5 dB/metre. Now let us descend into the deep, dark underworld of high-end reviewing and read how impressed the reviewer was with the "dynamic range" in a very large listening room:

"The "stand-in" demo in Peter's neo-gothic wing cast such a capacious soundstage filling a completely counter-intuitive cubic volume -- and at very happy levels -- that if Alon had any reservations about me getting the concept of the mondo monitor, they were gone with the proverbial wind. Frankly my dear, I do give a damn! While expensive as sin without apologies or guilty confessions, my first impressions in Oakland have me convinced that even under serious fire -- i.e. John Corigliano's Chaconne for solo violin and orchestra based on his score for The Red Violin -- the Magico Minis don't falter to telegraph the usual limitations of two-way speakers. They act far more like good conventional three-ways except for the lowest bass."

Uh-huh, yup, I think I'm starting to understand how this works.
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Old 13th September 2007, 11:08 PM   #1993
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Quote:
Originally posted by AJinFLA
Variac, beg your pardon.

[snip]

John, the NaO that I remember from the halcyon days of Madisound was the W18 version. When the inevitable Orion comparisons were made, it was not with the SS version. When I first viewed your Music and Design site, it was the W18 version for sale, with the SS option IIRC. Hindsight is 20/20, although I still can't see how you could consider this a "mistake". An option maybe.

[snip]





cheers,

AJ

Oh the good old days. I remember taking heat about the rear tweeter and a somewhat heated debate about the u-frame woofer. How the landscape has changed. Anyway, here is a link to the original NaO pages (preserved for historical reference).

http://www.geocities.com/kreskovs/NaO.html


The very first version of the NaO was back in October 2003 and used the SS mids, T25 front tweeter Vifa D27 rear, a PE 12" IB woofer and was intended to be use with an off-the-shelf active crossover (Like the Marchand XM9) between the woofer and panel with only a very simple active Eq circuit patched between preamp and active crossover. The AEP version came out about the time I offered the first generation custom PCBs with built in active crossover in the early 2004. John P. built his system and took it to the Iowa 2004 meeting. He also used a TC Sound woofer for which I design mods to the eq circuit. As far as I know, his is the only AEP version ever build other than my AEP prototype. He still seems happy with it.
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Old 14th September 2007, 12:17 AM   #1994
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by mige0
Hi




Soongsc, if I understood JohnK right this isn't the case and the correction is theoretically perfect.

It's not kind of feedback loop but rather a complimentary IN TIME balancing.

Greetings
Michael
What happens first will arrive at the ear first. Since electrical compensation happens first, you hear the wrongly compensated signal first. Unless you can make the compensation after the cone mode is excited and before the wave reaches the ear, you cannot ideally correct for it. I think if someone does a finite element analysis of the acoustic wave then you can clearly see it. I recall that Manger has a patent that does some kind of compensation acoustically, now this is possible, but the compensation will be perfect at specific measurement locations only.
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Old 14th September 2007, 12:29 AM   #1995
ucla88 is offline ucla88  Tahiti
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Quote:
Originally posted by john k...
...The very first version of the NaO was back in October 2003 ...
Has it been that long!!Have I really been ruminating about a cheap dipole for 4 years with nothing to show for it. Man, no wonder no one goes to my web pages anymore...
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Old 14th September 2007, 01:37 AM   #1996
AJinFLA is offline AJinFLA  United States
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Quote:
Originally posted by Lynn Olson


Ah! I think we come to the heart of the matter here.

By now it should be evident we hear - or at least, expect to hear - reproduced music in different ways. Speaking only for myself, I find all hifi systems not very close to the real thing - which for me, is live, un-amplified symphonic and choral music. When I go to a concert, it's at least a couple of days before I can stand to turn the hifi on again, it sounds so grossly artificial. Once I re-adapt, there is always at least some suspension of disbelief when listening to mechanical sound reproducers - and I use the word "mechanical" quite deliberately, since that's exactly what's wrong with hifi in general - a mechanical, "canned" quality that is always there.

Hi Lynn,

Well, I have to agree with you here about symphonic concerts and reproduction realism. However, I also attend smaller 4-8 pc acoustic jazz jams and I find that I can occasionally get fooled by the illusion a bit more if the recording is just right.
I find that up close to real musical instruments, the sound has a much more raw, sharp nature far from many smoothed over creamy recordings and yes, paper and other non-rigid, soft materials are capable of. That last layer of transparency is obscured by non-rigid materials IMHO. Perhaps it is all in my mind when I both see and hear a high hat being tapped and a sax's visceral feel, who knows.

Hi Tom,

Thank you for the info you provided. Perhaps we will have to agree to disagree here. I believe both rigid and non-rigid diaphragms have their issues and I pick what I perceive as the lesser poison. What I see in the data (that I have seen) is that rigid cones tend to have less distortion and smoother, more controlled behavior within the pass band that I would use them in.
Coupled with the fact that rigid cones are non-existent in HE pro audio type drivers, I'm not really sure how you could make comparisons to the drivers you are using or obtain data.
I may definitely have to try your record the output and loopback a couple times method with my next speaker design which creeps along ever so slowly. Did you ever take any impulses of the SH-100? BTW, I hope you are not using any of the standard B&C 8" coaxes, as I noted some major breakup in the factory curves.

Hi John,

I hope I wasn't one of those who gave you grief about the rear tweeter, as I would have used one myself had I not used the waveguide for my tweeter to closer match the forward directivity of the mid. I had actually used a rear tweeter with separate, adjustable eq to shape the power response on a bipole circa late 90's and quite liked the sound, given enough distance to rear wall.

Mark K,

What's taking so long with those things

cheers,

AJ
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Old 14th September 2007, 01:41 AM   #1997
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Karna is 62" high, and doesn't want the speakers to be bigger than she is. Can't say I blame her, a speaker that more than 74" high (my height) would intimidate me too. Her preference is she can at least see the tops of the speakers - again, I sympathize.

With the top of the front panel at 46" with a 12+15+15 layout (and 1" spacing), and 49" with a 12+15+18 layout, it'll be just barely within the limit with the 12" high double-panel RAAL tweeter. Now there is a bit of question about the RAAL - the front plate can be removed and the ribbons used singly, depending on how efficiency works out.

The answer to this isn't certain, since the narrow vertical dispersion means the energy from the ribbon tweeter falls off more slowly than the inverse-square law - in other words, at 3 to 5 meters, it'll be putting 2~3 dB more energy than the standard dB-at-1-meter specification implies. Alexander said in the last phone call "expect about 2.5 dB more at the listening position" than the standard spec implies. Also, the voltage sensitivity of the RAAL can fine-tuned by varying the ratio of the step-down transformer - the standard transformers have a 10:1 stepdown ratio and present a near-resistive 8 ohm impedance at the primary.

So I can't say whether I'll use 1, 2, or 3 RAAL ribbon sections (3 would be in the case of 2 stacked vertically in the front and 1 facing backwards). It seems like there's at least a reasonable chance for 1 in front and 1 in back, using the transformer to fine-tune the voltage sensitivity to match the sensitivity of the widerange driver at the 3~5 meter distance.
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Old 14th September 2007, 01:49 AM   #1998
Salas is offline Salas  Greece
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Lynn,

1. Are you going to design for a reference axis located between the wide range and the RAAL, or on the RAAL?

2. You did not tell your opinion about the open back compression driver dipole idea asked earlier...
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Old 14th September 2007, 02:02 AM   #1999
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Quote:
Originally posted by AJinFLA


Hi Lynn,

Well, I have to agree with you here about symphonic concerts and reproduction realism. However, I also attend smaller 4-8 pc acoustic jazz jams and I find that I can occasionally get fooled by the illusion a bit more if the recording is just right.
I find that up close to real musical instruments, the sound has a much more raw, sharp nature far from many smoothed over creamy recordings and yes, paper and other non-rigid, soft materials are capable of. That last layer of transparency is obscured by non-rigid materials IMHO. Perhaps it is all in my mind when I both see and hear a high hat being tapped and a sax's visceral feel, who knows.

cheers,

AJ
Hi there, AJinFLA.

I respect what you hear - our perceptions are our own, the deepest and most intimate part of personal reality. What you hear exists, and is real.

The whole symphony vs jazz discussion can get lost in the weeds of personal musical preferences, and is a diversion from a more important point that bears on what we've all been talking about. A jazz group has a much sparser spectra than a full-scale symphony orchestra, and the reverb time is much shorter as well.

This means the symphonic spectra superficially looks as dense as noise, but in reality is highly correlated with itself and the hall reflections. Any perturbation to the fine spectral and time structure does enormous violence to the performance, since so much is going on all at once - indeed, the sheer density, complexity, and fleeting spatial relationships are an integral part of the composer's and conductor's intentions.

Music with many fewer instruments has a much simpler and sparser spectrum, and is more about the vivid and pulsing tone colors of the individual instruments - the whole point of the trademark jazz solo. It's all about expression and tone colors.

The requirements of the two types of music for the hifi system are quite different. Even tiny amounts of IM distortion have a ruinous effect on a dense spectrum, creating all kinds of inharmonic sidebands that clash with the tone-colors of the ensemble. The effects of IM distortion (and driver resonances) are especially destructive to the subtle shimmering interplays of harmonic decay structures among different instruments.

This, I submit, is why symphonic and jazz fans tend to prefer different kinds of hifi systems. The spectral and dynamic requirements are dissimilar, with low dynamic IM distortion being especially important to classical music. Solid-state electronics typically have very low steady-state distortion, but can degrade by many orders of magnitude under fast transient conditions (memory effects in transistors causing on-chip thermal lags and transient mis-biasing). Similarly, the whole concept of dithering relies on a large number of samples to obtain the required distortion improvement in the LSB region - with fewer samples (shorter intervals), the benefits of dithering are greatly reduced.
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Old 14th September 2007, 02:14 AM   #2000
dlr is offline dlr  United States
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Default Very interesting thread

Quote:
Originally posted by john k...


Well it all comes down to whether the resonance is minimum phase or not. And I will suggest that is based on my measurements. Given that, minimum phase equalization of a minimum phase resonance corrects the response. The equalized driver and the ideal electrical bandpass filter have the same CSD. Since the CSD is just another way of post processing the impulse response then the two must also have the same impulse response. If its a linear system, then it can be corrected linearly.

However there are caveats. Although the breakup is primarily a linear phenomenon there are certainly nonlinear components, which, while not dominant, can not be corrected by application of such equalization. There are numerous other potential sources of problems too. As you say though, it's academic and there really isn't any way to definitive test it. All you can do is listen.
Makes me a bit nostalgic for this kind of thread that used to occur with some frequency at Madisound.

I'll throw in my $0.02 on driver minimum-phase. As you know John, I'm in full agreement, having modeled drivers for years to occasionally excruciating detail up to 24KHz, even 10" drivers. Every single one could be modeled perfectly with minimum-phase elements that resulting in essentially perfectly matching modeled/measured phase responses.

I'm also in your camp insofar as metal vs. doped paper, distinguished from the less accurate and unmodified term "paper", implying soft. I have yet to have fully successful result making a hard-coned driver the equivalent of a well done doped paper driver, especially in the midrange. I also suspect the amplification of the non-linear motor distortion by the peakiness exhibited in the raw driver.

That said, I am, however, slowly getting one hard-coned unit to finally sound good that I previously gave up on, though it's still not in the league of the SS midrange units. Also, the Accuton that you've heard at DIY, though a hard cone, doesn't have the excessive peak of a Seas and seems to be better as a result. But this is the larger 7" C95, the smaller ones still look to peaky to me, especially at the price.

AJ,

You keep referring to "soft, flexing, lossy paper cones", but this is a bit disingenuous. The truly good driver examples such as the SS units are not soft, they are relatively stiff doped-paper with significant internal damping and don't flex nearly as much as implied. There's also a very simple way to compare any two drivers in this regard. Make a range of distortion tests, such as those that Mark K and zaph make. All implications of "soft", "flexing", "lossy", etc., are really irrelevant without some sort of objective evaluation for comparison.

Better yet, make as set of these with crossover in place, since the driver's distortion profile will be altered when in use in a system. The non-linear aspect such as motor distortion amplification should be largely unmodified in only a lowpass is used whereas with a true midrange that has a bandpass applied should tend to show lower non-linear distortion products for the same acoustic output of a raw distortion measurement due to lessened driver displacement. In this case, a 3-way or more with a true midrange unit with a bandpass, the highpass could very easily, I suspect, result in a midrange output that exhibits lower non-linear distortion for a doped-paper than for a hard coned driver. At higher volumes, the doped paper could quite easily be perceived as being less dissonant since in general there will be less peak-driver amplification of distortion products.

With regard to the bandpass low-Q linear FR issues, these can, as John pointed out, be equalized, often with little difficulty. Those small perturbations that remain may be inaudible and for those that are not, they will still tend to be even order and euphonic, not dissonant. But for good doped-paper (and let's keep the conversation to good units of each type), these are usually not the big issue.

Dave
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